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Sample records for learning leave extinction

  1. Genetic disruptions of Drosophila Pavlovian learning leave extinction learning intact.

    PubMed

    Qin, H; Dubnau, J

    2010-03-01

    Individuals who experience traumatic events may develop persistent posttraumatic stress disorder. Patients with this disorder are commonly treated with exposure therapy, which has had limited long-term success. In experimental neurobiology, fear extinction is a model for exposure therapy. In this behavioral paradigm, animals are repeatedly exposed in a safe environment to the fearful stimulus, which leads to greatly reduced fear. Studying animal models of extinction already has lead to better therapeutic strategies and development of new candidate drugs. Lack of a powerful genetic model of extinction, however, has limited progress in identifying underlying molecular and genetic factors. In this study, we established a robust behavioral paradigm to study the short-term effect (acquisition) of extinction in Drosophila melanogaster. We focused on the extinction of olfactory aversive 1-day memory with a task that has been the main workhorse for genetics of memory in flies. Using this paradigm, we show that extinction can inhibit each of two genetically distinct forms of consolidated memory. We then used a series of single-gene mutants with known impact on associative learning to examine the effects on extinction. We find that extinction is intact in each of these mutants, suggesting that extinction learning relies on different molecular mechanisms than does Pavlovian learning. PMID:20015341

  2. Context, Learning, and Extinction

    ERIC Educational Resources Information Center

    Gershman, Samuel J.; Blei, David M.; Niv, Yael

    2010-01-01

    A. Redish et al. (2007) proposed a reinforcement learning model of context-dependent learning and extinction in conditioning experiments, using the idea of "state classification" to categorize new observations into states. In the current article, the authors propose an interpretation of this idea in terms of normative statistical inference. They…

  3. Behavioral tagging of extinction learning.

    PubMed

    de Carvalho Myskiw, Jociane; Benetti, Fernando; Izquierdo, Iván

    2013-01-15

    Extinction of contextual fear in rats is enhanced by exposure to a novel environment at 1-2 h before or 1 h after extinction training. This effect is antagonized by administration of protein synthesis inhibitors anisomycin and rapamycin into the hippocampus, but not into the amygdala, immediately after either novelty or extinction training, as well as by the gene expression blocker 5,6-dichloro-1-beta-D-ribofuranosylbenzimidazole administered after novelty training, but not after extinction training. Thus, this effect can be attributed to a mechanism similar to synaptic tagging, through which long-term potentiation can be enhanced by other long-term potentiations or by exposure to a novel environment in a protein synthesis-dependent fashion. Extinction learning produces a tag at the appropriate synapses, whereas novelty learning causes the synthesis of plasticity-related proteins that are captured by the tag, strengthening the synapses that generated this tag. PMID:23277583

  4. The learning of fear extinction.

    PubMed

    Furini, Cristiane; Myskiw, Jociane; Izquierdo, Ivan

    2014-11-01

    Recent work on the extinction of fear-motivated learning places emphasis on its putative circuitry and on its modulation. Extinction is the learned inhibition of retrieval of previously acquired responses. Fear extinction is used as a major component of exposure therapy in the treatment of fear memories such as those of the posttraumatic stress disorder (PTSD). It is initiated and maintained by interactions between the hippocampus, basolateral amygdala and ventromedial prefrontal cortex, which involve feedback regulation of the latter by the other two areas. Fear extinction depends on NMDA receptor activation. It is positively modulated by d-serine acting on the glycine site of NMDA receptors and blocked by AP5 (2-amino-5-phosphono propionate) in the three structures. In addition, histamine acting on H2 receptors and endocannabinoids acting on CB1 receptors in the three brain areas mentioned, and muscarinic cholinergic fibers from the medial septum to hippocampal CA1 positively modulate fear extinction. Importantly, fear extinction can be made state-dependent on circulating epinephrine, which may play a role in situations of stress. Exposure to a novel experience can strongly enhance the consolidation of fear extinction through a synaptic tagging and capture mechanism; this may be useful in the therapy of states caused by fear memory like PTSD. PMID:25452113

  5. Modulation of the extinction of fear learning.

    PubMed

    Myskiw, Jociane C; Izquierdo, Ivan; Furini, Cristiane R G

    2014-06-01

    We review recent work on extinction learning with emphasis on its modulation. Extinction is the learned inhibition of responding to previously acquired tasks. Like other forms of learning, it can be modulated by a variety of neurotransmitter systems and behavioral procedures. This bears on its use in the treatment of fear memories, particularly in posttraumatic stress disorder (PTSD), for which it is the treatment of choice, often under the name of exposure therapy. There have not been many laboratories interested in the modulation of extinction, but the available data, although not very abundant, are quite conclusive. Most studies on the nature of extinction and on its modulation have been carried out on fear motivated behaviors, possibly because of their applicability to the therapy of PTSD. A role for d-serine and the glycine site of NMDA receptors has been ascertained in two forms of extinction in the ventromedial prefrontal cortex, basolateral amygdala and dorsal hippocampus. The serine analog, d-cycloserine, has received clinical trials as an enhancer of extinction. The brain histaminergic system acting via H2 receptors, and the endocannabinoid system using CB1 receptors in the ventromedial prefrontal cortex, hippocampus and basolateral amygdala enhance extinction. Dopaminergic D1 and ß-noradrenergic receptors also modulate extinction by actions on these three structures. Isolated findings suggest roles for on serotonin-1A, dopaminergic-D2 and a- and ß-noradrenergic receptors in extinction modulation. Importantly, behavioral tagging and capture mechanisms in the hippocampus have been shown to play a major modulatory role in extinction. In addition, extinction of at least one aversive task (inhibitory avoidance) can be made state dependent on peripheral epinephrine. PMID:24742526

  6. Extinction of Learned Fear Induces Hippocampal Place Cell Remapping

    PubMed Central

    Wang, Melissa E.; Yuan, Robin K.; Keinath, Alexander T.; Ramos Álvarez, Manuel M.

    2015-01-01

    The extinction of learned fear is a hippocampus-dependent process thought to embody new learning rather than erasure of the original fear memory, although it is unknown how these competing contextual memories are represented in the hippocampus. We previously demonstrated that contextual fear conditioning results in hippocampal place cell remapping and long-term stabilization of novel representations. Here we report that extinction learning also induces place cell remapping in C57BL/6 mice. Specifically, we observed cells that preferentially remapped during different stages of learning. While some cells remapped in both fear conditioning and extinction, others responded predominantly during extinction, which may serve to modify previous representations as well as encode new safe associations. Additionally, we found cells that remapped primarily during fear conditioning, which could facilitate reacquisition of the original fear association. Moreover, we also observed cells that were stable throughout learning, which may serve to encode the static aspects of the environment. The short-term remapping observed during extinction was not found in animals that did not undergo fear conditioning, or when extinction was conducted outside of the conditioning context. Finally, conditioning and extinction produced an increase in spike phase locking to the theta and gamma frequencies. However, the degree of remapping seen during conditioning and extinction only correlated with gamma synchronization. Our results suggest that the extinction learning is a complex process that involves both modification of pre-existing memories and formation of new ones, and these traces coexist within the same hippocampal representation. PMID:26085635

  7. Cerebellar Contribution to Context Processing in Extinction Learning and Recall.

    PubMed

    Chang, D-I; Lissek, S; Ernst, T M; Thürling, M; Uengoer, M; Tegenthoff, M; Ladd, M E; Timmann, D

    2015-12-01

    Whereas acquisition of new associations is considered largely independent of the context, context dependency is a hallmark of extinction of the learned associations. The hippocampus and the prefrontal cortex are known to be involved in context processing during extinction learning and recall. Although the cerebellum has known functional and anatomic connections to the hippocampus and the prefrontal cortex, cerebellar contributions to context processing of extinction have rarely been studied. In the present study, we reanalyzed functional brain imaging data (fMRI) of previous work investigating context effects during extinction in a cognitive associative learning paradigm in 28 young and healthy subjects (Lissek et al. Neuroimage. 81:131-3, 2013). In that study, event-related fMRI analysis did not include the cerebellum. The 3 T fMRI dataset was reanalyzed using a spatial normalization method optimized for the cerebellum. Data of seven participants had to be excluded because the cerebellum had not been scanned in full. Cerebellar activation related to context change during extinction learning was most prominent in lobule Crus II bilaterally (p < 0.01, t > 2.53; partially corrected by predetermined cluster size). No significant cerebellar activations were observed related to context change during extinction retrieval. The posterolateral cerebellum appears to contribute to context-related processes during extinction learning, but not (or less) during extinction retrieval. The cerebellum may support context learning during extinction via its connections to the hippocampus. Alternatively, the cerebellum may support the shifting of attention to the context via its known connections to the dorsolateral prefrontal cortex. Because the ventromedial prefrontal cortex (vmPFC) is critically involved in context-related processes during extinction retrieval, and there are no known connections between the cerebellum and the vmPFC, the cerebellum may be less important

  8. Hippocampus NMDA receptors selectively mediate latent extinction of place learning.

    PubMed

    Goodman, Jarid; Gabriele, Amanda; Packard, Mark G

    2016-09-01

    Extinction of maze learning may be achieved with or without the animal performing the previously acquired response. In typical "response extinction," animals are given the opportunity to make the previously acquired approach response toward the goal location of the maze without reinforcement. In "latent extinction," animals are not given the opportunity to make the previously acquired response and instead are confined to the previous goal location without reinforcement. Previous evidence indicates that the effectiveness of these protocols may depend on the type of memory being extinguished. Thus, one aim of the present study was to further examine the effectiveness of response and latent extinction protocols across dorsolateral striatum (DLS)-dependent response learning and hippocampus-dependent place learning tasks. In addition, previous neural inactivation experiments indicate a selective role for the hippocampus in latent extinction, but have not investigated the precise neurotransmitter mechanisms involved. Thus, the present study also examined whether latent extinction of place learning might depend on NMDA receptor activity in the hippocampus. In experiment 1, adult male Long-Evans rats were trained in a response learning task in a water plus-maze, in which animals were reinforced to make a consistent body-turn response to reach an invisible escape platform. Results indicated that response extinction, but not latent extinction, was effective at extinguishing memory in the response learning task. In experiment 2, rats were trained in a place learning task, in which animals were reinforced to approach a consistent spatial location containing the hidden escape platform. In experiment 2, animals also received intra-hippocampal infusions of the NMDA receptor antagonist 2-amino-5-phosphopentanoic acid (AP5; 5.0 or 7.5 ug/0.5 µg) or saline vehicle immediately before response or latent extinction training. Results indicated that both extinction protocols were

  9. Adrenal-dependent diurnal modulation of conditioned fear extinction learning

    PubMed Central

    Woodruff, Elizabeth R.; Greenwood, Benjamin N.; Chun, Lauren E.; Fardi, Sara; Hinds, Laura R.; Spencer, Robert L.

    2015-01-01

    Post Traumatic Stress Disorder (PTSD) is associated with altered conditioned fear extinction expression and impaired circadian function including dysregulation of glucocorticoid hormone secretion. We examined in adult male rats the relationship between conditioned fear extinction learning, circadian phase, and endogenous glucocorticoids (CORT). Rats maintained on a 12 hr light:dark cycle were trained and tested across 3 separate daily sessions (conditioned fear acquisition and 2 extinction sessions) that were administered during either the rats’ active or inactive circadian phase. In an initial experiment we found that rats at both circadian phases acquired and extinguished auditory cue conditioned fear to a similar degree in the first extinction session. However, rats trained and tested at zeitgeber time-16 (ZT16) (active phase) showed enhanced extinction memory expression during the second extinction session compared to rats trained and tested at ZT4 (inactive phase). In a follow-up experiment, adrenalectomized (ADX) or sham surgery rats were similarly trained and tested across 3 separate daily sessions at either ZT4 or ZT16. ADX had no effect on conditioned fear acquisition or conditioned fear memory. Sham ADX rats trained and tested at ZT16 exhibited better extinction learning across the two extinction sessions compared to all other groups of rats. These results indicate that conditioned fear extinction learning is modulated by time of day, and this diurnal modulation requires the presence of adrenal hormones. These results support an important role of CORT-dependent circadian processes in regulating conditioned fear extinction learning, which may be capitalized upon to optimize effective treatment of PTSD. PMID:25746455

  10. 3,4-Methylenedioxymethamphetamine facilitates fear extinction learning.

    PubMed

    Young, M B; Andero, R; Ressler, K J; Howell, L L

    2015-01-01

    Acutely administered 3,4-methylenedioxymethamphetamine (MDMA, 'ecstasy') has been proposed to have long-term positive effects on post-traumatic stress disorder (PTSD) symptoms when combined with psychotherapy. No preclinical data support a mechanistic basis for these claims. Given the persistent nature of psychotherapeutic gains facilitated by MDMA, we hypothesized that MDMA improves fear extinction learning, a key process in exposure-based therapies for PTSD. In these experiments, mice were first exposed to cued fear conditioning and treated with drug vehicle or MDMA before extinction training 2 days later. MDMA was administered systemically and also directly targeted to brain structures known to contribute to extinction. In addition to behavioral measures of extinction, changes in mRNA levels of brain-derived neurotrophic factor (Bdnf) and Fos were measured after MDMA treatment and extinction. MDMA (7.8 mg kg(-1)) persistently and robustly enhanced long-term extinction when administered before extinction training. MDMA increased the expression of Fos in the amygdala and medial prefrontal cortex (mPFC), whereas increases in Bdnf expression were observed only in the amygdala after extinction training. Extinction enhancements were recapitulated when MDMA (1 μg) was infused directly into the basolateral complex of the amygdala (BLA), and enhancement was abolished when BDNF signaling was inhibited before extinction. These findings suggest that MDMA enhances fear memory extinction through a BDNF-dependent mechanism, and that MDMA may be a useful adjunct to exposure-based therapies for PTSD and other anxiety disorders characterized by altered fear learning. PMID:26371762

  11. The impact of context relevance during extinction learning.

    PubMed

    Lucke, Sara; Lachnit, Harald; Stüttgen, Maik C; Uengoer, Metin

    2014-09-01

    In two predictive-learning experiments, we investigated the role of the informational value of contexts for the formation of context-specific extinction learning. The contexts were each composed of two elements from two dimensions, A and B. In Phase 1 of each experiment, participants received acquisition training with a target cue Z in context A1B1 (the numbers assign particular values on the context dimensions). In Phase 2, participants were trained with conditional discriminations between two other cues, X and Y, for which only one of the two context dimensions was relevant. In a third phase, participants received extinction trials with cue Z in context A2B2. During a final test phase, we observed that a partial change of the extinction context disrupted extinction performance when the extinction context was changed on the dimension that had been trained as being relevant for the conditional discrimination. However, when the extinction context was changed on the irrelevant context dimension, extinction performance was not affected. Our results are consistent with the idea that relevant contexts receive more attention than do irrelevant contexts, leading to stronger context-specific processing of information learned in the former than in the latter type of contexts. PMID:24934214

  12. Behavioral and neural bases of extinction learning in Hermissenda

    PubMed Central

    Cavallo, Joel S.; Hamilton, Brittany N.; Farley, Joseph

    2014-01-01

    Extinction of classical conditioning is thought to produce new learning that masks or interferes with the original memory. However, research in the nudibranch Hermissenda crassicornis (H.c.) has challenged this view, and instead suggested that extinction erased the original associative memory. We have re-examined extinction in H.c. to test whether extinguished associative memories can be detected on the behavioral and cellular levels, and to characterize the temporal variables involved. Associative conditioning using pairings of light (CS) and rotation (US) produced characteristic suppression of H.c. phototactic behavior. A single session of extinction training (repeated light-alone presentations) reversed suppressed behavior back to pre-training levels when administered 15 min after associative conditioning. This effect was abolished if extinction was delayed by 23 h, and yet was recovered using extended extinction training (three consecutive daily extinction sessions). Extinguished phototactic suppression did not spontaneously recover at any retention interval (RI) tested (2-, 24-, 48-, 72-h), or after additional US presentations (no observed reinstatement). Extinction training (single session, 15 min interval) also reversed the pairing-produced increases in light-evoked spike frequencies of Type B photoreceptors, an identified site of associative memory storage that is causally related to phototactic suppression. These results suggest that the behavioral effects of extinction training are not due to temporary suppression of associative memories, but instead represent a reversal of the underlying cellular changes necessary for the expression of learning. In the companion article, we further elucidate mechanisms responsible for extinction-produced reversal of memory-related neural plasticity in Type B photoreceptors. PMID:25191236

  13. Increased prefrontal cortex neurogranin enhances plasticity and extinction learning.

    PubMed

    Zhong, Ling; Brown, Joshua; Kramer, Audra; Kaleka, Kanwardeep; Petersen, Amber; Krueger, Jamie N; Florence, Matthew; Muelbl, Matthew J; Battle, Michelle; Murphy, Geoffrey G; Olsen, Christopher M; Gerges, Nashaat Z

    2015-05-13

    Increasing plasticity in neurons of the prefrontal cortex (PFC) has been proposed as a possible therapeutic tool to enhance extinction, a process that is impaired in post-traumatic stress disorder, schizophrenia, and addiction. To test this hypothesis, we generated transgenic mice that overexpress neurogranin (a calmodulin-binding protein that facilitates long-term potentiation) in the PFC. Neurogranin overexpression in the PFC enhanced long-term potentiation and increased the rates of extinction learning of both fear conditioning and sucrose self-administration. Our results indicate that elevated neurogranin function within the PFC can enhance local plasticity and increase the rate of extinction learning across different behavioral tasks. Thus, neurogranin can provide a molecular link between enhanced plasticity and enhanced extinction. PMID:25972176

  14. Increased Prefrontal Cortex Neurogranin Enhances Plasticity and Extinction Learning

    PubMed Central

    Zhong, Ling; Brown, Joshua; Kramer, Audra; Kaleka, Kanwardeep; Petersen, Amber; Krueger, Jamie N.; Florence, Matthew; Muelbl, Matthew J.; Battle, Michelle; Murphy, Geoffrey G.; Olsen, Christopher M.

    2015-01-01

    Increasing plasticity in neurons of the prefrontal cortex (PFC) has been proposed as a possible therapeutic tool to enhance extinction, a process that is impaired in post-traumatic stress disorder, schizophrenia, and addiction. To test this hypothesis, we generated transgenic mice that overexpress neurogranin (a calmodulin-binding protein that facilitates long-term potentiation) in the PFC. Neurogranin overexpression in the PFC enhanced long-term potentiation and increased the rates of extinction learning of both fear conditioning and sucrose self-administration. Our results indicate that elevated neurogranin function within the PFC can enhance local plasticity and increase the rate of extinction learning across different behavioral tasks. Thus, neurogranin can provide a molecular link between enhanced plasticity and enhanced extinction. PMID:25972176

  15. Glutamatergic Targets for Enhancing Extinction Learning in Drug Addiction

    PubMed Central

    Cleva, R.M; Gass, J.T; Widholm, J.J; Olive, M.F

    2010-01-01

    The persistence of the motivational salience of drug-related environmental cues and contexts is one of the most problematic obstacles to successful treatment of drug addiction. Behavioral approaches to extinguishing the salience of drug-associated cues, such as cue exposure therapy, have generally produced disappointing results which have been attributed to, among other things, the context specificity of extinction and inadequate consolidation of extinction learning. Extinction of any behavior or conditioned response is a process of new and active learning, and increasing evidence suggests that glutamatergic neurotransmission, a key component of the neural plasticity that underlies normal learning and memory, is also involved in extinction learning. This review will summarize findings from both animal and human studies that suggest that pharmacological enhancement of glutamatergic neurotransmission facilitates extinction learning in the context of drug addiction. Pharmacological agents that have shown potential efficacy include NMDA partial agonists, mGluR5 receptor positive allosteric modulators, inhibitors of the GlyT1 glycine transporter, AMPA receptor potentiators, and activators of the cystine-glutamate exchanger. These classes of cognition-enhancing compounds could potentially serve as novel pharmacological adjuncts to cue exposure therapy to increase success rates in attenuating cue-induced drug craving and relapse. PMID:21629446

  16. Environmental Learning and the Study of Extinction.

    ERIC Educational Resources Information Center

    Bell, Anne C.; Russell, Constance L.; Plotkin, Rachel

    1998-01-01

    Describes an environmental workshop with three goals: (1) to develop a more grounded and personal understanding in students of extinction; (2) to draw attention to their specific life contexts while making connections between local and global phenomena; and (3) to critically examine anthropocentrism. Highlights efforts to disrupt strictly…

  17. Caloric restriction enhances fear extinction learning in mice.

    PubMed

    Riddle, Megan C; McKenna, Morgan C; Yoon, Yone J; Pattwell, Siobhan S; Santos, Patricia Mae G; Casey, B J; Glatt, Charles E

    2013-05-01

    Fear extinction learning, the ability to reassess a learned cue of danger as safe when it no longer predicts aversive events, is often dysregulated in anxiety disorders. Selective serotonin reuptake inhibitors (SSRI's) enhance neural plasticity and their ability to enhance fear extinction learning may explain their anxiolytic properties. Caloric restriction (CR) has SSRI-like effects on neural plasticity and anxiety-related behavior. We implemented CR in mice to determine its effects on conditioned-fear responses. Wild type and serotonin transporter (SERT) knockout mice underwent CR for 7 days leading to significant weight loss. Mice were then tested for cued fear learning and anxiety-related behavior. CR markedly enhanced fear extinction learning and its retention in adolescent female mice, and adults of both sexes. These effects of CR were absent in SERT knockout mice. Moreover, CR phenocopied behavioral and molecular effects of chronic fluoxetine, but there was no additive effect of CR in fluoxetine-treated mice. These results demonstrate that CR enhances fear extinction learning through a SERT-dependent mechanism. These results may have implications for eating disorders such as anorexia nervosa (AN), in which there is a high prevalence of anxiety before the onset of dietary restriction and support proposals that in AN, CR is a motivated effort to control dysregulated fear responses and elevated anxiety. PMID:23303073

  18. Caloric Restriction Enhances Fear Extinction Learning in Mice

    PubMed Central

    Riddle, Megan C; McKenna, Morgan C; Yoon, Yone J; Pattwell, Siobhan S; Santos, Patricia Mae G; Casey, B J; Glatt, Charles E

    2013-01-01

    Fear extinction learning, the ability to reassess a learned cue of danger as safe when it no longer predicts aversive events, is often dysregulated in anxiety disorders. Selective serotonin reuptake inhibitors (SSRI's) enhance neural plasticity and their ability to enhance fear extinction learning may explain their anxiolytic properties. Caloric restriction (CR) has SSRI-like effects on neural plasticity and anxiety-related behavior. We implemented CR in mice to determine its effects on conditioned-fear responses. Wild type and serotonin transporter (SERT) knockout mice underwent CR for 7 days leading to significant weight loss. Mice were then tested for cued fear learning and anxiety-related behavior. CR markedly enhanced fear extinction learning and its retention in adolescent female mice, and adults of both sexes. These effects of CR were absent in SERT knockout mice. Moreover, CR phenocopied behavioral and molecular effects of chronic fluoxetine, but there was no additive effect of CR in fluoxetine-treated mice. These results demonstrate that CR enhances fear extinction learning through a SERT-dependent mechanism. These results may have implications for eating disorders such as anorexia nervosa (AN), in which there is a high prevalence of anxiety before the onset of dietary restriction and support proposals that in AN, CR is a motivated effort to control dysregulated fear responses and elevated anxiety. PMID:23303073

  19. Learning to inhibit the response during instrumental (operant) extinction.

    PubMed

    Bouton, Mark E; Trask, Sydney; Carranza-Jasso, Rodrigo

    2016-07-01

    Five experiments tested implications of the idea that instrumental (operant) extinction involves learning to inhibit the learned response. All experiments used a discriminated operant procedure in which rats were reinforced for lever pressing or chain pulling in the presence of a discriminative stimulus (S), but not in its absence. In Experiment 1, extinction of the response (R) in the presence of S weakened responding in S, but equivalent nonreinforced exposure to S (without the opportunity to make R) did not. Experiment 2 replicated that result and found that extinction of R had no effect on a different R that had also been reinforced in the stimulus. In Experiments 3 and 4, rats first learned to perform several different stimulus and response combinations (S1R1, S2R1, S3R2, and S4R2). Extinction of a response in one stimulus (i.e., S1R1) transferred and weakened the same response, but not a different response, when it was tested in another stimulus (i.e., S2R1 but not S3R2). In Experiment 5, extinction still transferred between S1 and S2 when the stimuli set the occasion for R's association with different types of food pellets. The results confirm the importance of response inhibition in instrumental extinction: Nonreinforcement of the response in S causes the most effective suppression of responding, and response suppression is specific to the response but transfers and influences performance of the same response when it is occasioned by other stimuli. Theoretical and practical implications are discussed. (PsycINFO Database Record PMID:27379715

  20. Reconciling Reinforcement Learning Models with Behavioral Extinction and Renewal: Implications for Addiction, Relapse, and Problem Gambling

    ERIC Educational Resources Information Center

    Redish, A. David; Jensen, Steve; Johnson, Adam; Kurth-Nelson, Zeb

    2007-01-01

    Because learned associations are quickly renewed following extinction, the extinction process must include processes other than unlearning. However, reinforcement learning models, such as the temporal difference reinforcement learning (TDRL) model, treat extinction as an unlearning of associated value and are thus unable to capture renewal. TDRL…

  1. The Effect of D-Cycloserine on Immediate vs. Delayed Extinction of Learned Fear

    ERIC Educational Resources Information Center

    Langton, Julia M.; Richardson, Rick

    2010-01-01

    We compared the effect of D-cycloserine (DCS) on immediate (10 min after conditioning) and delayed (24 h after conditioning) extinction of learned fear in rats. DCS facilitated both immediate and delayed extinction when the drug was administered after extinction training. However, DCS did not facilitate immediate extinction when administered prior…

  2. Neuronal correlates of extinction learning are modulated by sex hormones.

    PubMed

    Merz, Christian J; Tabbert, Katharina; Schweckendiek, Jan; Klucken, Tim; Vaitl, Dieter; Stark, Rudolf; Wolf, Oliver T

    2012-10-01

    In emotional learning tasks, sex differences, stress effects and an interaction of these two moderators have often been observed. The sex hormones estradiol (E2) and progesterone (P4) vary over the menstrual cycle. We tested groups with different sex hormone status: 39 men, 30 women in the luteal phase (LU, high E2+P4) and 29 women taking oral contraceptives (OC, low E2+P4). They received either 30 mg cortisol or placebo prior to instructed differential fear conditioning consisting of neutral conditioned stimuli (CS) and an electrical stimulation (unconditioned stimulus; UCS). One figure (CS+) was paired with the UCS, the other figure (CS-) never. During extinction, no electrical stimulation was administered. Regarding fear acquisition, results showed higher skin conductance and higher brain responses to the CS+ compared to the CS- in several structures that were not modulated by cortisol or sex hormones. However, OC women exhibited higher CS+/CS- differentiations than men and LU women in the amygdala, thalamus, anterior cingulate and ventromedial prefrontal cortex during extinction. The suppression of endogenous sex hormones by OC seems to alter neuronal correlates of extinction. The observation that extinction is influenced by the current sex hormone availability is relevant for future studies and might also be clinically important. PMID:21990419

  3. Noradrenergic stimulation modulates activation of extinction-related brain regions and enhances contextual extinction learning without affecting renewal

    PubMed Central

    Lissek, Silke; Glaubitz, Benjamin; Güntürkün, Onur; Tegenthoff, Martin

    2015-01-01

    Renewal in extinction learning describes the recovery of an extinguished response if the extinction context differs from the context present during acquisition and recall. Attention may have a role in contextual modulation of behavior and contribute to the renewal effect, while noradrenaline (NA) is involved in attentional processing. In this functional magnetic resonance imaging (fMRI) study we investigated the role of the noradrenergic system for behavioral and brain activation correlates of contextual extinction and renewal, with a particular focus upon hippocampus and ventromedial prefrontal cortex (PFC), which have crucial roles in processing of renewal. Healthy human volunteers received a single dose of the NA reuptake inhibitor atomoxetine prior to extinction learning. During extinction of previously acquired cue-outcome associations, cues were presented in a novel context (ABA) or in the acquisition context (AAA). In recall, all cues were again presented in the acquisition context. Atomoxetine participants (ATO) showed significantly faster extinction compared to placebo (PLAC). However, atomoxetine did not affect renewal. Hippocampal activation was higher in ATO during extinction and recall, as was ventromedial PFC activation, except for ABA recall. Moreover, ATO showed stronger recruitment of insula, anterior cingulate, and dorsolateral/orbitofrontal PFC. Across groups, cingulate, hippocampus and vmPFC activity during ABA extinction correlated with recall performance, suggesting high relevance of these regions for processing the renewal effect. In summary, the noradrenergic system appears to be involved in the modification of established associations during extinction learning and thus has a role in behavioral flexibility. The assignment of an association to a context and the subsequent decision on an adequate response, however, presumably operate largely independently of noradrenergic mechanisms. PMID:25745389

  4. Stress-enhanced fear learning in rats is resistant to the effects of immediate massed extinction

    PubMed Central

    Long, Virginia A.; Fanselow, Michael S.

    2014-01-01

    Enhanced fear learning occurs subsequent to traumatic or stressful events and is a persistent challenge to the treatment of post-traumatic stress disorder (PTSD). Facilitation of learning produced by prior stress can elicit an exaggerated fear response to a minimally aversive event or stimulus. Stress-enhanced fear learning (SEFL) is a rat model of PTSD; rats previously exposed to the SEFL 15 electrical shocks procedure exhibit several behavioral responses similar to those seen in patients with PTSD. However, past reports found that SEFL is not mitigated by extinction (a model of exposure therapy) when the spaced extinction began 24 h after stress. Recent studies found that extinction from 10 min to 1 h subsequent to fear conditioning “erased” learning, whereas later extinction, occurring from 24 to 72 h after conditioning did not. Other studies indicate that massed extinction is more effective than spaced procedures. Therefore, we examined the time-dependent nature of extinction on the stress-induced enhancement of fear learning using a massed trial’s procedure. Experimental rats received 15 foot shocks and were given either no extinction or massed extinction 10 min or 72 h later. Our present data indicate that SEFL, following traumatic stress, is resistant to immediate massed extinction. Experimental rats showed exaggerated new fear learning regardless of when extinction training occurred. Thus, post-traumatic reactivity such as SEFL does not seem responsive to extinction treatments. PMID:22176467

  5. Forming Competing Fear Learning and Extinction Memories in Adolescence Makes Fear Difficult to Inhibit

    ERIC Educational Resources Information Center

    Baker, Kathryn D.; Richardson, Rick

    2015-01-01

    Fear inhibition is markedly impaired in adolescent rodents and humans. The present experiments investigated whether this impairment is critically determined by the animal's age at the time of fear learning or their age at fear extinction. Male rats (n = 170) were tested for extinction retention after conditioning and extinction at different ages.…

  6. Paid Educational Leave and Self-Directed Learning: Implications for Legislation on the Learning Leave Scheme in South Korea

    ERIC Educational Resources Information Center

    Oh, Jeong Rok; Park, Cho Hyun; Jo, Sung Jun

    2016-01-01

    Purpose: The purposes of this study are to explore paid educational leave (PEL), self-directed learning (SDL) and the relationship between them; and to identify the implications for legislation on the learning leave scheme in South Korea. Design/Methodology/Approach: The research method of the study is a literature review. Articles were identified…

  7. No evidence for blocking the return of fear by disrupting reconsolidation prior to extinction learning.

    PubMed

    Klucken, Tim; Kruse, Onno; Schweckendiek, Jan; Kuepper, Yvonne; Mueller, Erik M; Hennig, Juergen; Stark, Rudolf

    2016-06-01

    Fear extinction is a central model for the treatment of anxiety disorders. Initial research has reported that the single presentation of a conditioned stimulus prior to extinction learning can permanently block the return of fear. However, only few studies have explored this issue and could not always replicate the findings. The present study examined human fear extinction using a four-day design. On the first day, two neutral stimuli were paired with electrical stimulation (UCS), while a third stimulus (CS-) was not. Twenty-four hours later, one conditioned stimulus (CS+rem) and the CS- were reminded once, 10 min before extinction learning, while the other conditioned stimulus (CS+non-rem) was not presented prior to extinction learning. All stimuli were presented during extinction learning and during two re-extinction sessions (24 h and 6-months after extinction learning) without reinforcement. Blood oxygen level-dependent (BOLD) responses and skin conductance responses (SCRs) to both CS+ and the CS- were explored during acquisition, extinction, and in both re-extinction sessions. Regarding SCRs, the results showed that a single presentation of a conditioned stimulus did not block the return of fear during re-extinction: Fear recovery during re-extinction (24 h and 6-months after extinction learning) was observed for both CS+ compared with the CS- with no difference between CS+rem and CS+non-rem. Regarding BOLD-responses, no significant differences between CS+rem and CS+non-rem were found in region of interest (ROI)-analyses (amygdala, ventromedial prefrontal cortex) during extinction learning and both re-extinction sessions. Whole-brain analyses showed increased BOLD-responses to the CS+non-rem as compared to the CS+rem in several regions (e.g., middle frontal gyrus) during extinction learning and re-extinction (24 h after extinction learning). The present findings suggest that the effect of preventing the return of fear by disrupting reconsolidation seems to

  8. Repeated extinction and reversal learning of an approach response supports an arousal-mediated learning model

    PubMed Central

    Podlesnik, Christopher A.; Sanabria, Federico

    2016-01-01

    We assessed the effects of repeated extinction and reversals of two conditional stimuli (CS+/CS−) on an appetitive conditioned approach response in rats. Three results were observed that could not be accounted for by a simple linear operator model such as the one proposed by Rescorla and Wagner (1972): (1) responding to a CS− declined faster when a CS+ was simultaneously extinguished; (2) reacquisition of pre-extinction performance recovered rapidly within one session; and (3) reversal of CS+/CS− contingencies resulted in a more rapid recovery to the current CS− (former CS+) than the current CS+, accompanied by a slower acquisition of performance to the current CS+. An arousal parameter that mediates learning was introduced to a linear operator model to account for these effects. The arousal-mediated learning model adequately fit the data and predicted data from a second experiment with different rats in which only repeated reversals of CS+/CS− were assessed. According to this arousal-mediated learning model, learning is accelerated by US-elicited arousal and it slows down in the absence of US. Because arousal varies faster than conditioning, the model accounts for the decline in responding during extinction mainly through a reduction in arousal, not a change in learning. By preserving learning during extinction, the model is able to account for relapse effects like rapid reacquisition, renewal, and reinstatement. PMID:21172410

  9. Repeated extinction and reversal learning of an approach response supports an arousal-mediated learning model.

    PubMed

    Podlesnik, Christopher A; Sanabria, Federico

    2011-05-01

    We assessed the effects of repeated extinction and reversals of two conditional stimuli (CS+/CS-) on an appetitive conditioned approach response in rats. Three results were observed that could not be accounted for by a simple linear operator model such as the one proposed by Rescorla and Wagner (1972): (1) responding to a CS- declined faster when a CS+ was simultaneously extinguished; (2) reacquisition of pre-extinction performance recovered rapidly within one session; and (3) reversal of CS+/CS- contingencies resulted in a more rapid recovery to the current CS- (former CS+) than the current CS+, accompanied by a slower acquisition of performance to the current CS+. An arousal parameter that mediates learning was introduced to a linear operator model to account for these effects. The arousal-mediated learning model adequately fit the data and predicted data from a second experiment with different rats in which only repeated reversals of CS+/CS- were assessed. According to this arousal-mediated learning model, learning is accelerated by US-elicited arousal and it slows down in the absence of US. Because arousal varies faster than conditioning, the model accounts for the decline in responding during extinction mainly through a reduction in arousal, not a change in learning. By preserving learning during extinction, the model is able to account for relapse effects like rapid reacquisition, renewal, and reinstatement. PMID:21172410

  10. mGluR5 Positive Allosteric Modulation Enhances Extinction Learning Following Cocaine Self-Administration

    PubMed Central

    Cleva, Richard M.; Hicks, Megan P.; Gass, Justin T.; Wischerath, Kelly C.; Plasters, Elizabeth T.; Widholm, John J.; Olive, M. Foster

    2011-01-01

    Extinction of classically and instrumentally conditioned behaviors, such as conditioned fear and drug-seeking behavior, is a process of active learning, and recent studies indicate that potentiation of glutamatergic transmission facilitates extinction learning. In this study we investigated the effects of the type 5 metabotropic glutamate receptors (mGluR5) positive allosteric modulator 3-cyano-N-(1,3-diphenyl-1H-pyrazol-5-yl)benzamide (CDPPB) on the extinction of cocaine-seeking behavior in rats with a history of intravenous cocaine self-administration. To assess its effects on acquisition and consolidation of extinction learning, CDPPB (60 mg/kg) or vehicle was administered either 20 min prior to, or immediately following, each of 10 extinction sessions, respectively. When administered prior to each extinction session, CDPPB produced a significant reduction in the number of active lever presses on all 10 days of extinction training as compared to vehicle-treated animals. When administered following each extinction session, a significant reduction in the number of active lever presses was observed on the 2nd through 10th day of extinction. Both treatment regimens also reduced the number of extinction training sessions required to meet extinction criteria. Pre- or post-extinction training administration of CDPPB did not alter responding on the inactive lever and had no effects on open field locomotor activity. These data indicate that positive allosteric modulation of mGluR5 receptors facilitates the acquisition and consolidation of extinction learning following cocaine self-administration, and may provide a novel pharmacological approach to enhancing extinction learning when combined with cue exposure therapy for the treatment of cocaine addiction. PMID:21319882

  11. Impaired fear extinction learning and cortico-amygdala circuit abnormalities in a common genetic mouse strain

    PubMed Central

    Hefner, Kathryn; Whittle, Nigel; Juhasz, Jaynann; Norcross, Maxine; Karlsson, Rose-Marie; Saksida, Lisa M.; Bussey, Timothy J.; Singewald, Nicolas; Holmes, Andrew

    2008-01-01

    Fear extinction is a form of new learning that results in the inhibition of conditioned fear. Trait deficits in fear extinction are a risk factor for anxiety disorders. There are few examples of naturally-occurring animal models of impaired extinction. The present study compared fear extinction in a panel of inbred mouse strains. This strain survey revealed an impairment in fear extinction in 129/SvImJ (129S1). The phenotypic specificity of this deficit was evaluated by comparing 129S1 and C57BL/6J for one-trial and multi-trial fear conditioning, nociception, and extinction of conditioned taste aversion (CTA) and an appetitive instrumental response. 129S1 were tested for sensitivity to the extinction-facilitating effects of extended training, as well as D-cycloserine and yohimbine treatment. To elucidate the neural basis of impaired 129S1 fear extinction, c-Fos and Zif268 expression was mapped following extinction recall. Results showed that impaired fear extinction in 129S1 was unrelated to altered fear conditioning or nociception, and was dissociable from intact appetitive extinction. Yohimbine treatment facilitated extinction in 129S1, but neither extended extinction training nor D-cycloserine treatment improved 129S1 extinction. Following extinction recall, 129S1 showed reduced c-Fos and Zif268 expression in the infralimbic cortex and basolateral amygdala, and elevated c-Fos or Zif268 expression in central nucleus of the amygdala and medial paracapsular intercalated cell mass, relative to C57BL/6J. Collectively, these data demonstrate a deficit in fear extinction in 129S1 associated with a failure to properly engage corticolimbic extinction circuitry. This common inbred strain provides a novel model for studying impaired fear extinction in anxiety disorders. PMID:18685032

  12. Persistence of amygdala gamma oscillations during extinction learning predicts spontaneous fear recovery.

    PubMed

    Courtin, J; Karalis, N; Gonzalez-Campo, C; Wurtz, H; Herry, C

    2014-09-01

    Extinction of auditory fear conditioning induces a temporary inhibition of conditioned fear responses that can spontaneously reappear with the passage of time. Several lines of evidence indicate that extinction learning relies on the recruitment of specific neuronal populations within the basolateral amygdala. In contrast, post-extinction spontaneous fear recovery is thought to result from deficits in the consolidation of extinction memory within prefrontal neuronal circuits. Interestingly, recent data indicates that the strength of gamma oscillations in the basolateral amygdala during auditory fear conditioning correlates with retrieval of conditioned fear responses. In the present manuscript we evaluated the hypothesis that post-extinction spontaneous fear recovery might depend on the maintenance of gamma oscillations within the basolateral amygdala by using single unit and local field potential recordings in behaving mice. Our results indicate that gamma oscillations in the basolateral amygdala were enhanced following fear conditioning, whereas during extinction learning gamma profiles were more heterogeneous despite similar extinction learning rates. Remarkably, variations in the strength of gamma power within the basolateral amygdala between early and late stages of extinction linearly predicted the level of post-extinction spontaneous fear recovery. These data suggest that maintenance of gamma oscillations in the basolateral amygdala during extinction learning is a strong predictive factor of long term spontaneous fear recovery. PMID:24091205

  13. Transient inactivation of the pigeon hippocampus or the nidopallium caudolaterale during extinction learning impairs extinction retrieval in an appetitive conditioning paradigm.

    PubMed

    Lengersdorf, Daniel; Stüttgen, Maik C; Uengoer, Metin; Güntürkün, Onur

    2014-05-15

    The majority of experiments exploring context-dependent extinction learning employ Pavlovian fear conditioning in rodents. Since mechanisms of appetitive and aversive learning are known to differ at the neuronal level, we sought to investigate extinction learning in an appetitive setting. Working with pigeons, we established a within-subject ABA renewal paradigm based on Rescorla (Q J Exp Psychol 61:1793) and combined it with pharmacological interventions during extinction. From the fear conditioning literature, it is known that both prefrontal cortex and the hippocampus are core structures for context-specific extinction learning. Accordingly, we transiently inactivated the nidopallium caudolaterale (NCL, a functional analogue of mammalian prefrontal cortex) and the hippocampus in separate experiments by intracranial infusion of the sodium-channel blocker tetrodotoxin immediately before extinction training. We find that TTX in both structures non-specifically suppresses conditioned responding, as revealed by a reduction of response rate to both the extinguished conditioned stimulus and a control stimulus which remained reinforced throughout the experiment. Furthermore, TTX during extinction training impaired later extinction retrieval assessed under drug-free conditions. This was true when responding to the extinguished stimulus was assessed in the context of extinction but not when tested in the context of acquisition, although both contexts were matched with respect to their history of conditioning. These results indicate that both NCL and hippocampus are involved in extinction learning under appetitive conditions or, more specifically, in the consolidation of extinction memory, and that their contribution to extinction is context-specific. PMID:24569011

  14. Extinction of conditioned fear is better learned and recalled in the morning than in the evening.

    PubMed

    Pace-Schott, Edward F; Spencer, Rebecca M C; Vijayakumar, Shilpa; Ahmed, Nafis A K; Verga, Patrick W; Orr, Scott P; Pitman, Roger K; Milad, Mohammed R

    2013-11-01

    Sleep helps emotional memories consolidate and may promote generalization of fear extinction memory. We examined whether extinction learning and memory might differ in the morning and evening due, potentially, to circadian and/or sleep-homeostatic factors. Healthy men (N = 109) in 6 groups completed a 2-session protocol. In Session 1, fear conditioning was followed by extinction learning. Partial reinforcement with mild electric shock produced conditioned skin conductance responses (SCRs) to 2 differently colored lamps (CS+), but not a third color (CS-), within the computer image of a room (conditioning context). One CS+ (CS + E) but not the other (CS + U) was immediately extinguished by un-reinforced presentations in a different room (extinction context). Delay durations of 3 h (within AM or PM), 12 h (morning-to-evening or evening-to-morning) or 24 h (morning-to-morning or evening-to-evening) followed. In Session 2, extinction recall and contextual fear renewal were tested. We observed no significant effects of the delay interval on extinction memory but did observe an effect of time-of-day. Fear extinction was significantly better if learned in the morning (p = .002). Collapsing across CS + type, there was smaller morning differential SCR at both extinction recall (p = .003) and fear renewal (p = .005). Morning extinction recall showed better generalization from the CS + E to CS + U with the response to the CS + U significantly larger than to the CS + E only in the evening (p = .028). Thus, extinction is learned faster and its memory is better generalized in the morning. Cortisol and testosterone showed the expected greater salivary levels in the morning when higher testosterone/cortisol ratio also predicted better extinction learning. Circadian factors may promote morning extinction. Alternatively, evening homeostatic sleep pressure may impede extinction and favor recall of conditioned fear. PMID:23992769

  15. Extinction of Conditioned Fear is Better Learned and Recalled in the Morning than in the Evening

    PubMed Central

    Pace-Schott, Edward F.; Spencer, Rebecca M.C.; Vijayakumar, Shilpa; Ahmed, Nafis; Verga, Patrick W.; Orr, Scott P.; Pitman, Roger K.; Milad, Mohammed R.

    2013-01-01

    Sleep helps emotional memories consolidate and may promote generalization of fear extinction memory. We examined whether extinction learning and memory might differ in the morning and evening due, potentially, to circadian and/or sleep-homeostatic factors. Healthy men (N=109) in 6 groups completed a 2-session protocol. In Session 1, fear conditioning was followed by extinction learning. Partial reinforcement with mild electric shock produced conditioned skin conductance responses (SCR) to 2 differently colored lamps (CS+), but not a third color (CS−), within the computer image of a room (conditioning context). One CS+ (CS+E) but not the other (CS+U) was immediately extinguished by un-reinforced presentations in a different room (extinction context). Delay durations of 3 hr (within AM or PM), 12 hr (morning-to-evening or evening-to-morning) or 24 hr (morning-to-morning or evening-to-evening) followed. In Session 2, extinction recall and contextual fear renewal were tested. We observed no significant effects of the delay interval on extinction memory but did observe an effect of time-of-day. Fear extinction was significantly better if learned in the morning (p=.002). Collapsing across CS+ type, there was smaller morning differential SCR at both extinction recall (p=.003) and fear renewal (p=.005). Morning extinction recall showed better generalization from the CS+E to CS+U with the response to the CS+U significantly larger than to the CS+E only in the evening (p=.028). Thus, extinction is learned faster and its memory is better generalized in the morning. Cortisol and testosterone showed the expected greater salivary levels in the morning when higher testosterone/cortisol ratio also predicting better extinction learning. Circadian factors may promote morning extinction. Alternatively, evening homeostatic sleep pressure may impede extinction and favor recall of conditioned fear. PMID:23992769

  16. A Role of Protein Degradation in Memory Consolidation after Initial Learning and Extinction Learning in the Honeybee ("Apis mellifera")

    ERIC Educational Resources Information Center

    Felsenberg, Johannes; Dombrowski, Vincent; Eisenhardt, Dorothea

    2012-01-01

    Protein degradation is known to affect memory formation after extinction learning. We demonstrate here that an inhibitor of protein degradation, MG132, interferes with memory formation after extinction learning in a classical appetitive conditioning paradigm. In addition, we find an enhancement of memory formation when the same inhibitor is…

  17. Cortisol modifies extinction learning of recently acquired fear in men.

    PubMed

    Merz, Christian Josef; Hermann, Andrea; Stark, Rudolf; Wolf, Oliver Tobias

    2014-09-01

    Exposure therapy builds on the mechanism of fear extinction leading to decreased fear responses. How the stress hormone cortisol affects brain regions involved in fear extinction in humans is unknown. For this reason, we tested 32 men randomly assigned to receive either 30 mg hydrocortisone or placebo 45 min before fear extinction. In fear acquisition, a picture of a geometrical figure was either partially paired (conditioned stimulus; CS+) or not paired (CS-) with an electrical stimulation (unconditioned stimulus; UCS). In fear extinction, each CS was presented again, but no UCS occurred. Cortisol increased conditioned skin conductance responses in early and late extinction. In early extinction, higher activation towards the CS- than to the CS+ was found in the amygdala, hippocampus and posterior parahippocampal gyrus. This pattern might be associated with the establishment of a new memory trace. In late extinction, the placebo compared with the cortisol group displayed enhanced CS+/CS- differentiation in the amygdala, medial frontal cortex and nucleus accumbens. A change from early deactivation to late activation of the extinction circuit as seen in the placebo group seems to be needed to enhance extinction and to reduce fear. Cortisol appears to interfere with this process thereby impairing extinction of recently acquired conditioned fear. PMID:23945999

  18. Blockade of Dopamine Activity in the Nucleus Accumbens Impairs Learning Extinction of Conditioned Fear

    ERIC Educational Resources Information Center

    Holtzman-Assif, Orit; Laurent, Vincent; Westbrook, R. Frederick

    2010-01-01

    Three experiments used rats to investigate the role of dopamine activity in learning to inhibit conditioned fear responses (freezing) in extinction. In Experiment 1, rats systemically injected with the D2 dopamine antagonist, haloperidol, froze more across multiple extinction sessions and on a drug-free retention test than control rats. In…

  19. Context Switch Effects on Acquisition and Extinction in Human Predictive Learning

    ERIC Educational Resources Information Center

    Rosas, Juan M.; Callejas-Aguilera, Jose E.

    2006-01-01

    Four experiments tested context switch effects on acquisition and extinction in human predictive learning. A context switch impaired probability judgments about a cue-outcome relationship when the cue was trained in a context in which a different cue underwent extinction. The context switch also impaired judgments about a cue trained in a context…

  20. Cued Reacquisition Trials during Extinction Weaken Contextual Renewal in Human Predictive Learning

    ERIC Educational Resources Information Center

    Effting, Marieke; Vervliet, Bram; Beckers, Tom; Kindt, Merel

    2013-01-01

    Extinction is generally more context specific than acquisition, as illustrated by the renewal effect. While most strategies to counteract renewal focus on decreasing the context specificity of extinction, the present work aimed at increasing the context specificity of acquisition learning. Two experiments examined whether presenting cued…

  1. Extinction and Renewal of Pavlovian Modulation in Human Sequential Feature Positive Discrimination Learning

    ERIC Educational Resources Information Center

    Baeyens, Frank; Vansteenwegen, Debora; Beckers, Tom; Hermans, Dirk; Kerkhof, Ineke; De Ceulaer, Annick

    2005-01-01

    Using a conditioned suppression task, we investigated extinction and renewal of Pavlovian modulation in human sequential Feature Positive (FP) discrimination learning. In Experiment 1, in context a participants were first trained on two FP discriminations, X[right arrow]A+/A- and Y[right arrow]B+/B-. Extinction treatment was administered in the…

  2. Cannabinoid modulation of prefrontal-limbic activation during fear extinction learning and recall in humans.

    PubMed

    Rabinak, Christine A; Angstadt, Mike; Lyons, Maryssa; Mori, Shoko; Milad, Mohammed R; Liberzon, Israel; Phan, K Luan

    2014-09-01

    Pre-extinction administration of Δ9-tetrahydrocannibinol (THC) facilitates recall of extinction in healthy humans, and evidence from animal studies suggest that this likely occurs via enhancement of the cannabinoid system within the ventromedial prefrontal cortex (vmPFC) and hippocampus (HIPP), brain structures critical to fear extinction. However, the effect of cannabinoids on the underlying neural circuitry of extinction memory recall in humans has not been demonstrated. We conducted a functional magnetic resonance imaging (fMRI) study using a randomized, double-blind, placebo-controlled, between-subjects design (N=14/group) coupled with a standard Pavlovian fear extinction paradigm and an acute pharmacological challenge with oral dronabinol (synthetic THC) in healthy adult volunteers. We examined the effects of THC on vmPFC and HIPP activation when tested for recall of extinction learning 24 h after extinction learning. Compared to subjects who received placebo, participants who received THC showed increased vmPFC and HIPP activation to a previously extinguished conditioned stimulus (CS+E) during extinction memory recall. This study provides the first evidence that pre-extinction administration of THC modulates prefrontal-limbic circuits during fear extinction in humans and prompts future investigation to test if cannabinoid agonists can rescue or correct the impaired behavioral and neural function during extinction recall in patients with PTSD. Ultimately, the cannabinoid system may serve as a promising target for innovative intervention strategies (e.g. pharmacological enhancement of exposure-based therapy) in PTSD and other fear learning-related disorders. PMID:24055595

  3. Cannabinoid modulation of prefrontal-limbic activation during fear extinction learning and recall in humans

    PubMed Central

    Rabinak, Christine A.; Angstadt, Mike; Lyons, Maryssa; Mori, Shoko; Milad, Mohammed R.; Liberzon, Israel; Phan, K. Luan

    2013-01-01

    Pre-extinction administration of ∆9-tetrahydrocannibinol (THC) facilitates recall of extinction in healthy humans, and evidence from animal studies suggest that this likely involves via enhancement of the cannabinoid system within the ventromedial prefrontal cortex (vmPFC) and hippocampus (HIPP), brain structures critical to fear extinction. However, the effect of cannabinoids on the underlying neural circuitry of extinction memory recall in humans has not been demonstrated. We conducted a functional magnetic resonance imaging (fMRI) study using a randomized, double-blind, placebo-controlled, between-subjects design (N=14/group) coupled with a standard Pavlovian fear extinction paradigm and an acute pharmacological challenge with oral dronabinol (synthetic THC) in healthy adult volunteers. We examined the effects of THC on vmPFC and HIPP activation when tested for recall of extinction learning 24 hours after extinction learning. Compared to subjects who received placebo, participants who received THC showed increased vmPFC and HIPP activation to a previously extinguished conditioned stimulus (CS+E) during extinction memory recall. This study provides the first evidence that pre-extinction administration of THC modulates prefrontal-limbic circuits during fear extinction in humans and prompts future investigation to test if cannabinoid agonists can rescue or correct the impaired behavioral and neural function during extinction recall in patients with PTSD. Ultimately, the cannabinoid system may serve as a promising target for innovative intervention strategies (e.g. pharmacological enhancement of exposure-based therapy) in PTSD and other fear learning-related disorders. PMID:24055595

  4. Extinction learning is slower, weaker and less context specific after alcohol

    PubMed Central

    Bisby, James A.; King, John A.; Sulpizio, Valentina; Degeilh, Fanny; Valerie Curran, H.; Burgess, Neil

    2015-01-01

    Alcohol is frequently involved in psychological trauma and often used by individuals to reduce fear and anxiety. We examined the effects of alcohol on fear acquisition and extinction within a virtual environment. Healthy volunteers were administered alcohol (0.4 g/kg) or placebo and underwent acquisition and extinction from different viewpoints of a virtual courtyard, in which the conditioned stimulus, paired with a mild electric shock, was centrally located. Participants returned the following day to test fear recall from both viewpoints of the courtyard. Skin conductance responses were recorded as an index of conditioned fear. Successful fear acquisition under alcohol contrasted with impaired extinction learning evidenced by persistent conditioned responses (Experiment 1). Participants’ impairments in extinction under alcohol correlated with impairments in remembering object-locations in the courtyard seen from one viewpoint when tested from the other viewpoint. Alcohol-induced extinction impairments were overcome by increasing the number of extinction trials (Experiment 2). However, a test of fear recall the next day showed persistent fear in the alcohol group across both viewpoints. Thus, alcohol impaired extinction rather than acquisition of fear, suggesting that extinction is more dependent than acquisition on alcohol-sensitive representations of spatial context. Overall, extinction learning under alcohol was slower, weaker and less context-specific, resulting in persistent fear at test that generalized to the extinction viewpoint. The selective effect on extinction suggests an effect of alcohol on prefrontal involvement, while the reduced context-specificity implicates the hippocampus. These findings have important implications for the use of alcohol by individuals with clinical anxiety disorders. PMID:26234587

  5. Extinction learning is slower, weaker and less context specific after alcohol.

    PubMed

    Bisby, James A; King, John A; Sulpizio, Valentina; Degeilh, Fanny; Valerie Curran, H; Burgess, Neil

    2015-11-01

    Alcohol is frequently involved in psychological trauma and often used by individuals to reduce fear and anxiety. We examined the effects of alcohol on fear acquisition and extinction within a virtual environment. Healthy volunteers were administered alcohol (0.4g/kg) or placebo and underwent acquisition and extinction from different viewpoints of a virtual courtyard, in which the conditioned stimulus, paired with a mild electric shock, was centrally located. Participants returned the following day to test fear recall from both viewpoints of the courtyard. Skin conductance responses were recorded as an index of conditioned fear. Successful fear acquisition under alcohol contrasted with impaired extinction learning evidenced by persistent conditioned responses (Experiment 1). Participants' impairments in extinction under alcohol correlated with impairments in remembering object-locations in the courtyard seen from one viewpoint when tested from the other viewpoint. Alcohol-induced extinction impairments were overcome by increasing the number of extinction trials (Experiment 2). However, a test of fear recall the next day showed persistent fear in the alcohol group across both viewpoints. Thus, alcohol impaired extinction rather than acquisition of fear, suggesting that extinction is more dependent than acquisition on alcohol-sensitive representations of spatial context. Overall, extinction learning under alcohol was slower, weaker and less context-specific, resulting in persistent fear at test that generalized to the extinction viewpoint. The selective effect on extinction suggests an effect of alcohol on prefrontal involvement, while the reduced context-specificity implicates the hippocampus. These findings have important implications for the use of alcohol by individuals with clinical anxiety disorders. PMID:26234587

  6. Inhibiting DNA methylation alters olfactory extinction but not acquisition learning in Apis cerana and Apis mellifera.

    PubMed

    Gong, Zhiwen; Wang, Chao; Nieh, James C; Tan, Ken

    2016-07-01

    DNA methylation plays a key role in invertebrate acquisition and extinction memory. Honey bees have excellent olfactory learning, but the role of DNA methylation in memory formation has, to date, only been studied in Apis mellifera. We inhibited DNA methylation by inhibiting DNA methyltransferase (DNMT) with zebularine (zeb) and studied the resulting effects upon olfactory acquisition and extinction memory in two honey bee species, Apis cerana and A. mellifera. We used the proboscis extension reflex (PER) assay to measure memory. We provide the first demonstration that DNA methylation is also important in the olfactory extinction learning of A. cerana. DNMT did not reduce acquisition learning in either species. However, zeb bidirectionally and differentially altered extinction learning in both species. In particular, zeb provided 1h before acquisition learning improved extinction memory retention in A. mellifera, but reduced extinction memory retention in A. cerana. The reasons for these differences are unclear, but provide a basis for future studies to explore species-specific differences in the effects of methylation on memory formation. PMID:27262427

  7. Vagus Nerve Stimulation as a Tool to Induce Plasticity in Pathways Relevant for Extinction Learning

    PubMed Central

    Childs, Jessica E.; Alvarez-Dieppa, Amanda C.; McIntyre, Christa K.; Kroener, Sven

    2015-01-01

    Extinction describes the process of attenuating behavioral responses to neutral stimuli when they no longer provide the reinforcement that has been maintaining the behavior. There is close correspondence between fear and human anxiety, and therefore studies of extinction learning might provide insight into the biological nature of anxiety-related disorders such as post-traumatic stress disorder, and they might help to develop strategies to treat them. Preclinical research aims to aid extinction learning and to induce targeted plasticity in extinction circuits to consolidate the newly formed memory. Vagus nerve stimulation (VNS) is a powerful approach that provides tight temporal and circuit-specific release of neurotransmitters, resulting in modulation of neuronal networks engaged in an ongoing task. VNS enhances memory consolidation in both rats and humans, and pairing VNS with exposure to conditioned cues enhances the consolidation of extinction learning in rats. Here, we provide a detailed protocol for the preparation of custom-made parts and the surgical procedures required for VNS in rats. Using this protocol we show how VNS can facilitate the extinction of conditioned fear responses in an auditory fear conditioning task. In addition, we provide evidence that VNS modulates synaptic plasticity in the pathway between the infralimbic (IL) medial prefrontal cortex and the basolateral complex of the amygdala (BLA), which is involved in the expression and modulation of extinction memory. PMID:26325100

  8. Vagus Nerve Stimulation as a Tool to Induce Plasticity in Pathways Relevant for Extinction Learning.

    PubMed

    Childs, Jessica E; Alvarez-Dieppa, Amanda C; McIntyre, Christa K; Kroener, Sven

    2015-01-01

    Extinction describes the process of attenuating behavioral responses to neutral stimuli when they no longer provide the reinforcement that has been maintaining the behavior. There is close correspondence between fear and human anxiety, and therefore studies of extinction learning might provide insight into the biological nature of anxiety-related disorders such as post-traumatic stress disorder, and they might help to develop strategies to treat them. Preclinical research aims to aid extinction learning and to induce targeted plasticity in extinction circuits to consolidate the newly formed memory. Vagus nerve stimulation (VNS) is a powerful approach that provides tight temporal and circuit-specific release of neurotransmitters, resulting in modulation of neuronal networks engaged in an ongoing task. VNS enhances memory consolidation in both rats and humans, and pairing VNS with exposure to conditioned cues enhances the consolidation of extinction learning in rats. Here, we provide a detailed protocol for the preparation of custom-made parts and the surgical procedures required for VNS in rats. Using this protocol we show how VNS can facilitate the extinction of conditioned fear responses in an auditory fear conditioning task. In addition, we provide evidence that VNS modulates synaptic plasticity in the pathway between the infralimbic (IL) medial prefrontal cortex and the basolateral complex of the amygdala (BLA), which is involved in the expression and modulation of extinction memory. PMID:26325100

  9. Rethinking Extinction.

    PubMed

    Dunsmoor, Joseph E; Niv, Yael; Daw, Nathaniel; Phelps, Elizabeth A

    2015-10-01

    Extinction serves as the leading theoretical framework and experimental model to describe how learned behaviors diminish through absence of anticipated reinforcement. In the past decade, extinction has moved beyond the realm of associative learning theory and behavioral experimentation in animals and has become a topic of considerable interest in the neuroscience of learning, memory, and emotion. Here, we review research and theories of extinction, both as a learning process and as a behavioral technique, and consider whether traditional understandings warrant a re-examination. We discuss the neurobiology, cognitive factors, and major computational theories, and revisit the predominant view that extinction results in new learning that interferes with expression of the original memory. Additionally, we reconsider the limitations of extinction as a technique to prevent the relapse of maladaptive behavior and discuss novel approaches, informed by contemporary theoretical advances, that augment traditional extinction methods to target and potentially alter maladaptive memories. PMID:26447572

  10. Extinction learning deficit in a rodent model of attention-deficit hyperactivity disorder

    PubMed Central

    2012-01-01

    Background Deficient operant extinction has been hypothesized to be constitutive of ADHD dysfunction. In order to elucidate the behavioral mechanisms underlying this deficit, the performance of an animal model of ADHD, the spontaneously hypertensive rat (SHR), was compared against the performance of a control strain, the Wistar-Kyoto rat (WKY) during extinction. Method Following extensive training of lever pressing under variable interval schedules of food reinforcement (reported previously), SHR and WKY rats were exposed to two sessions of extinction training. Extinction data was analyzed using the Dynamic Bi-Exponential Refractory Model (DBERM) of operant performance. DBERM assumes that operant responses are organized in bouts separated by pauses; during extinction, bouts may decline across multiple dimensions, including frequency and length. DBERM parameters were estimated using hierarchical Bayesian modeling. Results SHR responded more than WKY during the first extinction session. DBERM parameter estimates revealed that, at the onset of extinction, SHR produced more response bouts than WKY. Over the course of extinction, response bouts progressively shortened for WKY but not for SHR. Conclusions Based on prior findings on the sensitivity of DBERM parameters to motivational and schedule manipulations, present data suggests that (1) more frequent response bouts in SHR are likely related to greater incentive motivation, and (2) the persistent length of bouts in SHR are likely related to a slower updating of the response-outcome association. Overall, these findings suggest specific motivational and learning deficits that may explain ADHD-related impairments in operant performance. PMID:23237608

  11. Differential Effects of Controllable Stress Exposure on Subsequent Extinction Learning in Adult Rats

    PubMed Central

    Hadad-Ophir, Osnat; Brande-Eilat, Noa; Richter-Levin, Gal

    2016-01-01

    Deficits in fear extinction are thought to be related to various anxiety disorders. While failure to extinguish conditioned fear may result in pathological anxiety levels, the ability to quickly and efficiently attenuate learned fear through extinction processes can be extremely beneficial for the individual. One of the factors that may affect the efficiency of the extinction process is prior experience of stressful situations. In the current study, we examined whether exposure to controllable stress, which is suggested to induce stress resilience, can affect subsequent fear extinction. Here, following prolonged two-way shuttle (TWS) avoidance training and a validation of acquired stress controllability, adult rats underwent either cued or contextual fear-conditioning (FC), followed by an extinction session. We further evaluated long lasting alterations of GABAergic targets in the medial pre-frontal cortex (mPFC), as these were implicated in FC and extinction and stress controllability. In cued, but not in contextual fear extinction, within-session extinction was enhanced following controllable stress compared to a control group. Interestingly, impaired extinction recall was detected in both extinction types following the stress procedure. Additionally, stress controllability-dependent alterations in GABAergic markers expression in infralimbic (IL), but not prelimbic (PL) cortex, were detected. These alterations are proposed to be related to the within-session effect, but not the recall impairment. The results emphasize the contribution of prior experience on coping with subsequent stressful experiences. Moreover, the results emphasize that exposure to controllable stress does not generally facilitate future stress coping as previously claimed, but its effects are dependent on specific features of the events taking place. PMID:26793083

  12. Methylene blue facilitates the extinction of fear in an animal model of susceptibility to learned helplessness.

    PubMed

    Wrubel, Kathryn M; Barrett, Douglas; Shumake, Jason; Johnson, S Elizabeth; Gonzalez-Lima, F

    2007-02-01

    The objectives were to (1) extend previous findings on fear extinction deficits in male congenitally helpless rats (a model for susceptibility to learned helplessness) to female congenitally helpless rats, and (2) attempt a therapeutic intervention with methylene blue, a metabolic enhancer that improves memory retention, to alleviate the predicted extinction deficits. In the first experiment, fear acquisition (four tone-shock pairings in operant chamber) was followed by extinction training (60 tones in open field). Congenitally helpless rats showed fear acquisition similar to controls but had dramatic extinction deficits, and did not display the gradual extinction curves observed in controls. Congenitally helpless rats demonstrated greater tone-evoked freezing as compared to controls in both the acquisition and extinction contexts one week after extinction training, and also in the extinction probe conducted one month later. In the second experiment (which began one month after the first experiment) congenitally helpless subjects were further exposed to tones for 5 days, each followed by 4 mg/kg methylene blue or saline IP, and had a fear renewal test in the acquisition context. Methylene blue administration improved retention of the extinction memory as demonstrated by significant decreases in fear renewal as compared to saline-administered congenitally helpless subjects. The impaired ability to extinguish fear to a traumatic memory in congenitally helpless rats supports the validity of this strain as an animal model for vulnerability to post-traumatic stress disorder, and this study further suggests that methylene blue may facilitate fear extinction as an adjunct to exposure therapy. PMID:17011803

  13. Delay and trace fear conditioning in a complex virtual learning environment-neural substrates of extinction.

    PubMed

    Ewald, Heike; Glotzbach-Schoon, Evelyn; Gerdes, Antje B M; Andreatta, Marta; Müller, Mathias; Mühlberger, Andreas; Pauli, Paul

    2014-01-01

    Extinction is an important mechanism to inhibit initially acquired fear responses. There is growing evidence that the ventromedial prefrontal cortex (vmPFC) inhibits the amygdala and therefore plays an important role in the extinction of delay fear conditioning. To our knowledge, there is no evidence on the role of the prefrontal cortex in the extinction of trace conditioning up to now. Thus, we compared brain structures involved in the extinction of human delay and trace fear conditioning in a between-subjects-design in an fMRI study. Participants were passively guided through a virtual environment during learning and extinction of conditioned fear. Two different lights served as conditioned stimuli (CS); as unconditioned stimulus (US) a mildly painful electric stimulus was delivered. In the delay conditioning group (DCG) the US was administered with offset of one light (CS+), whereas in the trace conditioning group (TCG) the US was presented 4 s after CS+ offset. Both groups showed insular and striatal activation during early extinction, but differed in their prefrontal activation. The vmPFC was mainly activated in the DCG, whereas the TCG showed activation of the dorsolateral prefrontal cortex (dlPFC) during extinction. These results point to different extinction processes in delay and trace conditioning. VmPFC activation during extinction of delay conditioning might reflect the inhibition of the fear response. In contrast, dlPFC activation during extinction of trace conditioning may reflect modulation of working memory processes which are involved in bridging the trace interval and hold information in short term memory. PMID:24904363

  14. The Plasticity of Extinction: Contribution of the Prefrontal Cortex in Treating Addiction through Inhibitory Learning.

    PubMed

    Gass, J T; Chandler, L J

    2013-01-01

    Theories of drug addiction that incorporate various concepts from the fields of learning and memory have led to the idea that classical and operant conditioning principles underlie the compulsiveness of addictive behaviors. Relapse often results from exposure to drug-associated cues, and the ability to extinguish these conditioned behaviors through inhibitory learning could serve as a potential therapeutic approach for those who suffer from addiction. This review will examine the evidence that extinction learning alters neuronal plasticity in specific brain regions and pathways. In particular, subregions of the prefrontal cortex (PFC) and their projections to other brain regions have been shown to differentially modulate drug-seeking and extinction behavior. Additionally, there is a growing body of research demonstrating that manipulation of neuronal plasticity can alter extinction learning. Therefore, the ability to alter plasticity within areas of the PFC through pharmacological manipulation could facilitate the acquisition of extinction and provide a novel intervention to aid in the extinction of drug-related memories. PMID:23750137

  15. Involvement of Dopamine D1/D5 and D2 Receptors in Context-Dependent Extinction Learning and Memory Reinstatement

    PubMed Central

    André, Marion Agnès Emma; Manahan-Vaughan, Denise

    2016-01-01

    Dopamine contributes to the regulation of higher order information processing and executive control. It is important for memory consolidation processes, and for the adaptation of learned responses based on experience. In line with this, under aversive learning conditions, application of dopamine receptor antagonists prior to extinction result in enhanced memory reinstatement. Here, we investigated the contribution of the dopaminergic system to extinction and memory reinstatement (renewal) of an appetitive spatial learning task in rodents. Rats were trained for 3 days in a T-maze (context “A”) to associate a goal arm with a food reward, despite low reward probability (acquisition phase). On day 4, extinction learning (unrewarded) occurred, that was reinforced by a context change (“B”). On day 5, re-exposure to the (unrewarded) “A” context took place (renewal of context “A”, followed by extinction of context “A”). In control animals, significant extinction occurred on day 4, that was followed by an initial memory reinstatement (renewal) on day 5, that was, in turn, succeeded by extinction of renewal. Intracerebral treatment with a D1/D5-receptor antagonist prior to the extinction trials, elicited a potent enhancement of extinction in context “B”. By contrast, a D1/D5-agonist impaired renewal in context “A”. Extinction in the “A” context on day 5 was unaffected by the D1/D5-ligands. Treatment with a D2-receptor antagonist prior to extinction had no overall effect on extinction in context “B” or renewal in context “A”, although extinction of the renewal effect was impaired on day 5, compared to controls. Taken together, these data suggest that dopamine acting on the D1/D5-receptor modulates both acquisition and consolidation of context-dependent extinction. By contrast, the D2-receptor may contribute to context-independent aspects of this kind of extinction learning. PMID:26834599

  16. D-cycloserine Deters Reacquisition of Cocaine Self-Administration by Augmenting Extinction Learning

    PubMed Central

    Nic Dhonnchadha, Bríd Á; Szalay, Jonathan J; Achat-Mendes, Cindy; Platt, Donna M; Otto, Michael W; Spealman, Roger D; Kantak, Kathleen M

    2010-01-01

    Augmentation of cue exposure (extinction) therapy with cognitive-enhancing pharmacotherapy may offer an effective strategy to combat cocaine relapse. To investigate this possibility at the preclinical level, rats and squirrel monkeys were trained to self-administer cocaine paired with a brief visual cue. Lever pressing was subsequently extinguished by withholding cocaine injections while maintaining response-contingent presentations of the cue. The glycine partial agonist D-cycloserine (DCS; 15 and 30 mg/kg in rats, 3 and 10 mg/kg in monkeys) was evaluated for its effects on the rate of extinction and subsequent reacquisition of cocaine self-administration. Compared with vehicle, pretreatment with 30 mg/kg DCS 0.5 h before extinction training reduced the number of responses and latency to reach the extinction criterion in rats, but neither dose of DCS altered these measures in monkeys. In both species, pretreatment with the higher dose of DCS before extinction training significantly attenuated reacquisition of cocaine self-administration compared with either extinction training in the absence of DCS or DCS in the absence of explicit extinction. Furthermore, treatment with 30 mg/kg DCS accompanied by brief handling (a stress induction) immediately after but not 6 h after extinction training attenuated reacquisition of cocaine self-administration in rats. No adverse effects of 10 mg/kg DCS were evident in quantitative observational studies in monkeys. The results suggest that DCS augmented consolidation of extinction learning to deter reacquisition of cocaine self-administration in rats and monkeys. The results suggest that DCS combined with exposure therapy may constitute a rational strategy for the clinical management of cocaine relapse. PMID:19741593

  17. Neural correlates of two different types of extinction learning in the amygdala central nucleus.

    PubMed

    Iordanova, Mihaela D; Deroche, Mickael L D; Esber, Guillem R; Schoenbaum, Geoffrey

    2016-01-01

    Extinction is a fundamental form of memory updating in which one learns to stop expecting an event that no longer occurs. This learning ensues when one experiences a change in environmental contingencies, that is, when an expected outcome fails to occur (simple extinction), or when a novel inflated expectation of a double outcome (overexpectation) is in conflict with the real outcome, and is a process that has been linked to amygdala function. Here, we show that in rats, the same neuronal population in the amygdala central nucleus updates reward expectancies and behaviour in both types of extinction, and neural changes in one paradigm are reflected in the other. This work may have implications for the management of addiction and anxiety disorders that require treatments based on the outcome omission, and disorders such as obesity that could use overexpectation, but not omission strategies. PMID:27531638

  18. Neural correlates of two different types of extinction learning in the amygdala central nucleus

    PubMed Central

    Iordanova, Mihaela D.; Deroche, Mickael L. D.; Esber, Guillem R.; Schoenbaum, Geoffrey

    2016-01-01

    Extinction is a fundamental form of memory updating in which one learns to stop expecting an event that no longer occurs. This learning ensues when one experiences a change in environmental contingencies, that is, when an expected outcome fails to occur (simple extinction), or when a novel inflated expectation of a double outcome (overexpectation) is in conflict with the real outcome, and is a process that has been linked to amygdala function. Here, we show that in rats, the same neuronal population in the amygdala central nucleus updates reward expectancies and behaviour in both types of extinction, and neural changes in one paradigm are reflected in the other. This work may have implications for the management of addiction and anxiety disorders that require treatments based on the outcome omission, and disorders such as obesity that could use overexpectation, but not omission strategies. PMID:27531638

  19. Learned immunosuppression: extinction, renewal, and the challenge of reconsolidation.

    PubMed

    Hadamitzky, Martin; Engler, Harald; Schedlowski, Manfred

    2013-03-01

    Behavioral conditioning of immune responses is one of the most impressive examples for the bidirectional communication among the nervous and immune systems. We established a model of behaviorally conditioned immunosuppression employing a conditioned taste aversion (CTA) paradigm in the rat pairing a novel taste (saccharin) as a conditioned stimulus (CS) with the immunosuppressive drug cyclosporine A (CsA) as an unconditioned stimulus (US). By re-presenting the CS during evocation, rats avoid drinking the saccharin. Concomitantly animals display an immunosuppression reflected by an ex vivo reduction in splenic T cell proliferation as well as diminished interleukin-2 and interferon-γ production and cytokine mRNA expression, mimicking the actual effect of the US (CsA). Due to the fact that the kinetics of this behaviorally conditioned immunosuppression are completely unknown, extinction of the conditioned response on the behavioral level (CTA) as well as in the immune response needs to be elucidated together with the neural processes mediating the extinction process. PMID:22791465

  20. Systemic or intra-amygdala infusion of the benzodiazepine, midazolam, impairs learning, but facilitates re-learning to inhibit fear responses in extinction.

    PubMed

    Hart, Genevra; Harris, Justin A; Westbrook, R Frederick

    2010-04-01

    A series of experiments used rats to study the effect of a systemic or intra-amygdala infusion of the benzodiazepine, midazolam, on learning and re-learning to inhibit context conditioned fear (freezing) responses. Rats were subjected to two context-conditioning episodes followed by extinction under drug or vehicle, or to two cycles of context conditioning and extinction with the second extinction under drug or vehicle. A 20-min extinction under vehicle resulted in better long-term inhibition on a subsequent drug-free retention test than a 4-min extinction under vehicle, or a 20-min, as well as a 4-min, extinction under drug. However, a 20-min, as well as a 4-min, second extinction under drug was just as effective in producing long-term inhibition as a 20-min second extinction under vehicle and this inhibition was greater than that produced by a 4-min second extinction under vehicle. Initial extinction of 5, 10, or 20 min were equally effective in producing long-term inhibition when the second extinction under drug was 20 min; and 5-, 10-, or 20-min second extinction under drug were equally effective in producing long-term inhibition when the initial extinction was 5 min. A 4- or 20-min second extinction under an infusion of drug into the basolateral amygdala (BLA) was as effective in producing long-term inhibition as a 20-min second extinction under vehicle and was more effective than a 4-min second extinction under vehicle. The results show that midazolam impairs learning to inhibit fear responses but spares and even facilitates re-learning this inhibition. PMID:20348202

  1. Students with Special Educational Needs in Secondary Education: Are They Intending to Learn or to Leave?

    ERIC Educational Resources Information Center

    Pijl, Sip Jan; Frostad, Per; Mjaavatn, Per Egil

    2014-01-01

    During their secondary school years, a considerable number of students seriously consider choosing between learning and leaving. Leaving school early means that students do not complete their education. Early school leaving is the last step in a process in which students gradually lose interest and develop the intention to leave school. This study…

  2. Sleep promotes consolidation and generalization of extinction learning in simulated exposure therapy for spider fear.

    PubMed

    Pace-Schott, Edward F; Verga, Patrick W; Bennett, Tobias S; Spencer, Rebecca M C

    2012-08-01

    Simulated exposure therapy for spider phobia served as a clinically naturalistic model to study effects of sleep on extinction. Spider-fearing, young adult women (N = 66), instrumented for skin conductance response (SCR), heart rate acceleration (HRA) and corrugator electromyography (EMG), viewed 14 identical 1-min videos of a behaving spider before a 12-hr delay containing a normal night's Sleep (N = 20) or continuous daytime Wake (N = 23), or a 2-hr delay of continuous wake in the Morning (N = 11) or Evening (N = 12). Following the delay, all groups viewed this same video 6 times followed by six 1-min videos of a novel spider. After each video, participants rated disgust, fearfulness and unpleasantness. In all 4 groups, all measures except corrugator EMG diminished across Session 1 (extinction learning) and, excepting SCR to a sudden noise, increased from the old to novel spider in Session 2. In Wake only, summed subjective ratings and SCR to the old spider significantly increased across the delay (extinction loss) and were greater for the novel vs. the old spider when it was equally novel at the beginning of Session 1 (sensitization). In Sleep only, SCR to a sudden noise decreased across the inter-session delay (extinction augmentation) and, along with HRA, was lower to the novel spider than initially to the old spider in Session 1 (extinction generalization). None of the above differentiated Morning and Evening groups suggesting that intervening sleep, rather than time-of-testing, produced differences between Sleep and Wake. Thus, sleep following exposure therapy may promote retention and generalization of extinction learning. PMID:22578824

  3. Conditioned fear and extinction learning performance and its association with psychiatric symptoms in active duty Marines

    PubMed Central

    Acheson, D.T.; Geyer, M.A.; Baker, D.G.; Nievergelt, C.M.; Yurgil, K.; Risbrough, V.B.

    2014-01-01

    Summary Background Posttraumatic Stress Disorder (PTSD) is a major public health concern, especially given the recent wars in Iraq and Afghanistan. Nevertheless, despite a sharp increase in the incidence of psychiatric disorders in returning veterans, empirically based prevention strategies are still lacking. To develop effective prevention and treatment strategies, it is necessary to understand the underlying biological mechanisms contributing to PTSD and other trauma related symptoms. Methods The “Marine Resiliency Study II” (MRS-II; October 2011–October 2013) Neurocognition project is an investigation of neurocognitive performance in Marines about to be deployed to Afghanistan. As part of this investigation, 1195 Marines and Navy corpsmen underwent a fear conditioning and extinction paradigm and psychiatric symptom assessment prior to deployment. The current study assesses (1) the effectiveness of the fear potentiated startle paradigm in producing fear learning and extinction and (2) the association of performance in the paradigm with baseline psychiatric symptom classes (healthy: n = 923, PTSD symptoms: n = 42, anxiety symptoms: n = 37, and depression symptoms: n = 12). Results Results suggest that the task was effective in producing differential fear learning and fear extinction in this cohort. Further, distinct patterns emerged differentiating the PTSD and anxiety symptom classes from both healthy and depression classes. During fear acquisition, the PTSD symptom group was the only group to show deficient discrimination between the conditioned stimulus (CS+) and safety cue (CS−), exhibiting larger startle responses during the safety cue compared to the healthy group. During extinction learning, the PTSD symptom group showed significantly less reduction in their CS+ responding over time compared to the healthy group, as well as reduced extinction of self-reported anxiety to the CS+ by the end of the extinction session. Conversely, the anxiety symptom

  4. Value learning and arousal in the extinction of probabilistic rewards: the role of dopamine in a modified temporal difference model.

    PubMed

    Song, Minryung R; Fellous, Jean-Marc

    2014-01-01

    Because most rewarding events are probabilistic and changing, the extinction of probabilistic rewards is important for survival. It has been proposed that the extinction of probabilistic rewards depends on arousal and the amount of learning of reward values. Midbrain dopamine neurons were suggested to play a role in both arousal and learning reward values. Despite extensive research on modeling dopaminergic activity in reward learning (e.g. temporal difference models), few studies have been done on modeling its role in arousal. Although temporal difference models capture key characteristics of dopaminergic activity during the extinction of deterministic rewards, they have been less successful at simulating the extinction of probabilistic rewards. By adding an arousal signal to a temporal difference model, we were able to simulate the extinction of probabilistic rewards and its dependence on the amount of learning. Our simulations propose that arousal allows the probability of reward to have lasting effects on the updating of reward value, which slows the extinction of low probability rewards. Using this model, we predicted that, by signaling the prediction error, dopamine determines the learned reward value that has to be extinguished during extinction and participates in regulating the size of the arousal signal that controls the learning rate. These predictions were supported by pharmacological experiments in rats. PMID:24586823

  5. Distinct Contributions of the Basolateral Amygdala and the Medial Prefrontal Cortex to Learning and Relearning Extinction of Context Conditioned Fear

    ERIC Educational Resources Information Center

    Laurent, Vincent; Westbrook, R. Frederick

    2008-01-01

    We studied the roles of the basolateral amygdala (BLA) and the medial prefrontal cortex (mPFC) in learning and relearning to inhibit context conditioned fear (freezing) in extinction. In Experiment 1, pre-extinction BLA infusion of the NMDA receptor (NMDAr) antagonist, ifenprodil, impaired the development and retention of inhibition but…

  6. Autophosphorylation of [alpha]CaMKII is Differentially Involved in New Learning and Unlearning Mechanisms of Memory Extinction

    ERIC Educational Resources Information Center

    Kimura, Ryoichi; Silva, Alcino J.; Ohno, Masuo

    2008-01-01

    Accumulating evidence indicates the key role of [alpha]-calcium/calmodulin-dependent protein kinase II ([alpha]CaMKII) in synaptic plasticity and learning, but it remains unclear how this kinase participates in the processing of memory extinction. Here, we investigated the mechanism by which [alpha]CaMKII may mediate extinction by using…

  7. Leaving

    ERIC Educational Resources Information Center

    Jones, Robyn L.

    2011-01-01

    Within this article, the author presents a personal story, "Leaving," which highlights the problematic experience of opposing established practice. The tale tells of the difficulty faced by creative agency when confronted by a constraining structural hegemony. Specifically, it draws attention to the professionalization of academic life through a…

  8. Dissociation of the Role of Infralimbic Cortex in Learning and Consolidation of Extinction of Recent and Remote Aversion Memory.

    PubMed

    Awad, Walaa; Ferreira, Guillaume; Maroun, Mouna

    2015-10-01

    Medial prefrontal circuits have been reported to undergo a major reorganization over time and gradually take a more important role for remote emotional memories such as contextual fear memory or food aversion memory. The medial prefrontal cortex, and specifically its ventral subregion, the infralimbic cortex (IL), was also reported to be critical for recent memory extinction of contextual fear conditioning and conditioned odor aversion. However, its exact role in the extinction of remotely acquired information is still not clear. Using postretrieval blockade of protein synthesis or inactivation of the IL, we showed that the IL is similarly required for extinction consolidation of recent and remote fear memory. However, in odor aversion memory, the IL was only involved in extinction consolidation of recent, but not remote, memory. In contrast, only remote retrieval of aversion memory induced c-Fos activation in the IL and preretrieval inactivation of the IL with lidocaine impaired subsequent extinction of remote but not recent memory, indicating IL is necessary for extinction learning of remote aversion memory. In contrast to the effects in odor aversion, our data show that the involvement of the IL in the consolidation of fear extinction does not depend on the memory age. More importantly, our data indicate that the IL is implicated in the extinction of fear and nonfear-based associations and suggest dissociation in the engagement of the IL in the learning and consolidation of food aversion extinction over time. PMID:25872918

  9. In vitro extinction learning in Hermissenda: involvement of conditioned inhibition molecules

    PubMed Central

    Cavallo, Joel S.; Hamilton, Brittany N.; Farley, Joseph

    2014-01-01

    Extinction of a conditioned association is typically viewed as the establishment of new learning rather than the erasure of the original memory. However, recent research in the nudibranch, Hermissenda crassicornis (H.c.) demonstrated that extinction training (using repeated light-alone presentations) given 15 min, but not 23 h, after memory acquisition reversed both the cellular correlates of learning (enhanced Type B cell excitability) and the behavioral changes (reduced phototaxis) produced by associative conditioning (pairings of light, CS, and rotation, US). Here, we investigated the putative molecular signaling pathways that underlie this extinction in H.c. by using a novel in vitro protocol combined with pharmacological manipulations. After intact H.c. received either light-rotation pairings (Paired), random presentations of light and rotation (Random), or no stimulation (Untrained), B cells from isolated CNSs were recorded from during exposure to extinction training consisting of two series of 15 consecutive light-steps (LSs). When in vitro extinction was administered shortly (2 h, but not 24 h) after paired training, B cells from Paired animals showed progressive and robust declines in spike frequency by the 30th LS, while control cells (Random and Untrained) did not. We found that several molecules implicated in H.c. conditioned inhibitory (CI) learning, protein phosphatase 1 (PP1) and arachidonic acid (AA)/12-lipoxygenase (12-LOX) metabolites, also contributed to the spike frequency decreases produced by in vitro extinction. Protein phosphatase 2B (PP2B) also appeared to play a role. Calyculin A (PP1 inhibitor), cyclosporin A (PP2B inhibitor), and baicalein (a 12-LOX inhibitor) all blocked the spike frequency declines in Paired B cells produced by 30 LSs. Conversely, injection of catalytically-active PP1 (caPP1) or PP2B (caPP2B) into Untrained B cells partially mimicked the spike frequency declines observed in Paired cells, as did bath-applied AA, and

  10. Extinction learning, which consists of the inhibition of retrieval, can be learned without retrieval

    PubMed Central

    de Carvalho Myskiw, Jociane; Furini, Cristiane Regina Guerino; Schmidt, Bianca; Ferreira, Flávia; Izquierdo, Ivan

    2015-01-01

    In the present study we test the hypothesis that extinction is not a consequence of retrieval in unreinforced conditioned stimulus (CS) presentation but the mere perception of the CS in the absence of a conditioned response. Animals with cannulae implanted in the CA1 region of hippocampus were subjected to extinction of contextual fear conditioning. Muscimol infused intra-CA1 before an extinction training session of contextual fear conditioning (CFC) blocks retrieval but not consolidation of extinction measured 24 h later. Additionally, this inhibition of retrieval does not affect early persistence of extinction when tested 7 d later or its spontaneous recovery after 2 wk. Furthermore, both anisomycin, an inhibitor of ribosomal protein synthesis, and rapamycin, an inhibitor of extraribosomal protein synthesis, given into the CA1, impair extinction of CFC regardless of whether its retrieval was blocked by muscimol. Therefore, retrieval performance in the first unreinforced session is not necessary for the installation, maintenance, or spontaneous recovery of extinction of CFC. PMID:25550507

  11. Blocking NMDA-receptors in the pigeon’s “prefrontal” caudal nidopallium impairs appetitive extinction learning in a sign-tracking paradigm

    PubMed Central

    Lengersdorf, Daniel; Marks, David; Uengoer, Metin; Stüttgen, Maik C.; Güntürkün, Onur

    2015-01-01

    Extinction learning provides the ability to flexibly adapt to new contingencies by learning to inhibit previously acquired associations in a context-dependent manner. The neural networks underlying extinction learning were mostly studied in rodents using fear extinction paradigms. To uncover invariant properties of the neural basis of extinction learning, we employ pigeons as a model system. Since the prefrontal cortex (PFC) of mammals is a key structure for extinction learning, we assessed the role of N-methyl-D-aspartate receptors (NMDARs) in the nidopallium caudolaterale (NCL), the avian functional equivalent of mammalian PFC. Since NMDARs in PFC have been shown to be relevant for extinction learning, we locally antagonized NMDARs through 2-Amino-5-phosphonovalerianacid (APV) during extinction learning in a within-subject sign-tracking ABA-renewal paradigm. APV-injection slowed down extinction learning and in addition also caused a disinhibition of responding to a continuously reinforced control stimulus. In subsequent retrieval sessions, spontaneous recovery was increased while ABA renewal was unaffected. The effect of APV resembles that observed in studies of fear extinction with rodents, suggesting common neural substrates of extinction under both appetitive and aversive conditions and highlighting the similarity of mammalian PFC and the avian caudal nidopallium despite 300 million years of independent evolution. PMID:25918502

  12. [Treatment of posttraumatic stress disorder and extinction learning of traumatic memory].

    PubMed

    Asukai, Nozomu

    2013-06-01

    Posttraumatic stress disorder (PTSD) is a debilitating psychological condition that develops following exposure to a traumatic event. The characteristic symptoms of PTSD are re-experience, avoidance, psychic numbing and hyper-arousal. The biological PTSD literature has been dramatically growing over the past three decades. PTSD symptoms related to re-experiencing the traumatic event may be conceptualized within a fear conditioning framework. Recent findings suggest that PTSD is associated with a failure of extinction learning of an acquired fear response. A fear-circuit model of PTSD posits that vmPFC fails to inhibit the amygdala, which has a crucial role in fear learning. Exposure therapy currently has the largest number of randomized clinical trials demonstrating its efficacy, and is recommended with substantial clinical confidence in treatment guidelines for PTSD. The efficacy of Prolonged Exposure (PE) was also shown for Japanese PTSD patients in a randomized controlled trial (Asukai et al., 2010). The emotional processing theory that accounts for the treatment mechanism of PE may be consistent with the hypothesis of a neurobiological mechanism in PTSD. D-cycloserine (DCS), an NMDA partial agonist, has been shown to facilitate extinction learning in animals and humans. Clinically, DCS has been shown to be a promising augmentation to PE, particularly for those who need longer treatment. PMID:25069244

  13. Loss of histone deacetylase 2 improves working memory and accelerates extinction learning.

    PubMed

    Morris, Michael J; Mahgoub, Melissa; Na, Elisa S; Pranav, Heena; Monteggia, Lisa M

    2013-04-10

    Histone acetylation and deacetylation can be dynamically regulated in response to environmental stimuli and play important roles in learning and memory. Pharmacological inhibition of histone deacetylases (HDACs) improves performance in learning tasks; however, many of these classical agents are "pan-HDAC" inhibitors, and their use makes it difficult to determine the roles of specific HDACs in cognitive function. We took a genetic approach using mice lacking the class I HDACs, HDAC1 or HDAC2, in postmitotic forebrain neurons to investigate the specificity or functional redundancy of these HDACs in learning and synaptic plasticity. We show that selective knock-out of Hdac2 led to a robust acceleration of the extinction rate of conditioned fear responses and a conditioned taste aversion as well as enhanced performance in an attentional set-shifting task. Hdac2 knock-out had no impact on episodic memory or motor learning, suggesting that the effects are task-dependent, with the predominant impact of HDAC2 inhibition being an enhancement in an animal's ability to rapidly adapt its behavioral strategy as a result of changes in associative contingencies. Our results demonstrate that the loss of HDAC2 improves associative learning, with no effect in nonassociative learning tasks, suggesting a specific role for HDAC2 in particular types of learning. HDAC2 may be an intriguing target for cognitive and psychiatric disorders that are characterized by an inability to inhibit behavioral responsiveness to maladaptive or no longer relevant associations. PMID:23575838

  14. Loss of histone deacetylase 2 improves working memory and accelerates extinction learning

    PubMed Central

    Morris, Michael J.; Mahgoub, Melissa; Na, Elisa S.; Pranav, Heena; Monteggia, Lisa. M.

    2013-01-01

    Histone acetylation and deacetylation can be dynamically regulated in response to environmental stimuli and play important roles in learning and memory. Pharmacological inhibition of histone deacetylases (HDACs) improves performance in learning tasks, however these classical agents are ‘pan-HDAC’ inhibitors and their use makes it difficult to determine the roles of specific HDACs in cognitive function. We took a genetic approach using mice lacking the class I HDACs, HDAC1 or HDAC2, in postmitotic forebrain neurons to investigate the specificity or functional redundancy of these HDACs in learning and synaptic plasticity. We show that selective knockout of HDAC2 led to a robust acceleration of the extinction rate of conditioned fear responses and a conditioned taste aversion as well as enhanced performance in an attentional set-shifting task. HDAC2 knockout had no impact on episodic memory or motor learning suggesting that the effects are task-dependent, with the predominant impact of HDAC2 inhibition being an enhancement in an animal’s ability to rapidly adapt its behavioral strategy as a result of changes in associative contingencies. Our results demonstrate that the loss of HDAC2 improves associative learning, with no effect in non-associative learning tasks, suggesting a specific role for HDAC2 in particular types of learning. HDAC2 may be an intriguing target for cognitive and psychiatric disorders that are characterized by an inability to inhibit behavioral responsiveness to maladaptive or no longer relevant associations. PMID:23575838

  15. Zinc transporter 3 is involved in learned fear and extinction, but not in innate fear.

    PubMed

    Martel, Guillaume; Hevi, Charles; Friebely, Olivia; Baybutt, Trevor; Shumyatsky, Gleb P

    2010-11-01

    Synaptically released Zn²+ is a potential modulator of neurotransmission and synaptic plasticity in fear-conditioning pathways. Zinc transporter 3 (ZnT3) knock-out (KO) mice are well suited to test the role of zinc in learned fear, because ZnT3 is colocalized with synaptic zinc, responsible for its transport to synaptic vesicles, highly enriched in the amygdala-associated neural circuitry, and ZnT3 KO mice lack Zn²+ in synaptic vesicles. However, earlier work reported no deficiency in fear memory in ZnT3 KO mice, which is surprising based on the effects of Zn²+ on amygdala synaptic plasticity. We therefore reexamined ZnT3 KO mice in various tasks for learned and innate fear. The mutants were deficient in a weak fear-conditioning protocol using single tone-shock pairing but showed normal memory when a stronger, five-pairing protocol was used. ZnT3 KO mice were deficient in memory when a tone was presented as complex auditory information in a discontinuous fashion. Moreover, ZnT3 KO mice showed abnormality in trace fear conditioning and in fear extinction. By contrast, ZnT3 KO mice had normal anxiety. Thus, ZnT3 is involved in associative fear memory and extinction, but not in innate fear, consistent with the role of synaptic zinc in amygdala synaptic plasticity. PMID:21036893

  16. Systemic or Intra-Amygdala Infusion of the Benzodiazepine, Midazolam, Impairs Learning, but Facilitates Re-Learning to Inhibit Fear Responses in Extinction

    ERIC Educational Resources Information Center

    Hart, Genevra; Harris, Justin A.; Westbrook, R. Frederick

    2010-01-01

    A series of experiments used rats to study the effect of a systemic or intra-amygdala infusion of the benzodiazepine, midazolam, on learning and re-learning to inhibit context conditioned fear (freezing) responses. Rats were subjected to two context-conditioning episodes followed by extinction under drug or vehicle, or to two cycles of context…

  17. Towards a Learning Identity: Young People Becoming Learners after Leaving School

    ERIC Educational Resources Information Center

    Higgins, Jane

    2013-01-01

    This article explores the development of learning identities among 51 young New Zealanders who left school with few or no qualifications. Most experienced a period of time after leaving school when they were not in education, employment or training (known as NEET). At the time of this research all had moved into a learning environment of some…

  18. Fear generalization in humans: impact of feature learning on conditioning and extinction.

    PubMed

    Vervliet, Bram; Geens, Maarten

    2014-09-01

    Little is known about the role of discrete stimulus features in the regulation of fear. This study examined the effects of feature learning on the acquisition and extinction of fear conditioning. Human participants were fear conditioned to a yellow triangle (CS+) using an electrical shock. We manipulated feature learning through differential conditioning. The nonconditioned control stimulus (CS-) was a red triangle in one group (Color-Relevant), but a yellow circle in the other group (Shape-Relevant). Next, two generalization stimuli were tested that shared the shape- or color-feature with the CS+ (a blue triangle and a yellow square). Online shock-expectancy ratings and skin conductance responding showed that the CS- determined the pattern of fear generalization: the same-color stimulus elicited more fear in Group Color-Relevant, versus the same-shape stimulus in group Shape-Relevant. Furthermore, extinguishing these two generalization stimuli had no detectable effect on fear of the CS+. These results show that fear generalization is influenced by feature learning through differential conditioning, and that exposures to different features of a stimulus are not sufficient to extinguish fear of that stimulus as a whole. PMID:24120427

  19. Impaired Contextual Fear Extinction Learning is Associated with Aberrant Regulation of CHD-Type Chromatin Remodeling Factors

    PubMed Central

    Wille, Alexandra; Maurer, Verena; Piatti, Paolo; Whittle, Nigel; Rieder, Dietmar; Singewald, Nicolas; Lusser, Alexandra

    2015-01-01

    Successful attenuation of fearful memories is a cognitive process requiring initiation of highly coordinated transcription programs. Chromatin-modulating mechanisms such as DNA methylation and histone modifications, including acetylation, are key regulators of these processes. However, knowledge concerning the role of ATP-dependent chromatin remodeling factors (ChRFs) being required for successful fear extinction is lacking. Underscoring the potential importance of these factors that alter histone-DNA contacts within nucleosomes are recent genome-wide association studies linking several ChRFs to various human cognitive and psychiatric disorders. To better understand the role of ChRFs in the brain, and since to date little is known about ChRF expression in the brain, we performed a comprehensive survey of expression levels of 24 ATP-dependent remodelers across different brain areas, and we identified several distinct high molecular weight complexes by chromatographic methods. We next aimed to gain novel insight into the potential regulation of ChRFs in different brain regions in association with normal and impaired fear extinction learning. To this end, we established the 129S1/SvImJ (S1) laboratory mouse strain as a model for compromised contextual fear extinction learning that can be rescued by dietary zinc restriction (ZnR). Using this model along with genetically related but fear extinction-competent 129S6/SvEv (S6) mice as controls, we found that impaired fear extinction in S1 was associated with enhanced ventral hippocampal expression of CHD1 and reduced expression of CHD5 that was normalized following successful rescue of impaired fear extinction. Moreover, a select reduction in CHD3 expression was observed in the ventral hippocampus (vHC) following successful rescue of fear extinction in S1 mice. Taken together, these data provide novel insight into the regulation of specific ChRFs following an impaired cognitive process and its rescue, and they suggest that

  20. Impaired Contextual Fear Extinction Learning is Associated with Aberrant Regulation of CHD-Type Chromatin Remodeling Factors.

    PubMed

    Wille, Alexandra; Maurer, Verena; Piatti, Paolo; Whittle, Nigel; Rieder, Dietmar; Singewald, Nicolas; Lusser, Alexandra

    2015-01-01

    Successful attenuation of fearful memories is a cognitive process requiring initiation of highly coordinated transcription programs. Chromatin-modulating mechanisms such as DNA methylation and histone modifications, including acetylation, are key regulators of these processes. However, knowledge concerning the role of ATP-dependent chromatin remodeling factors (ChRFs) being required for successful fear extinction is lacking. Underscoring the potential importance of these factors that alter histone-DNA contacts within nucleosomes are recent genome-wide association studies linking several ChRFs to various human cognitive and psychiatric disorders. To better understand the role of ChRFs in the brain, and since to date little is known about ChRF expression in the brain, we performed a comprehensive survey of expression levels of 24 ATP-dependent remodelers across different brain areas, and we identified several distinct high molecular weight complexes by chromatographic methods. We next aimed to gain novel insight into the potential regulation of ChRFs in different brain regions in association with normal and impaired fear extinction learning. To this end, we established the 129S1/SvImJ (S1) laboratory mouse strain as a model for compromised contextual fear extinction learning that can be rescued by dietary zinc restriction (ZnR). Using this model along with genetically related but fear extinction-competent 129S6/SvEv (S6) mice as controls, we found that impaired fear extinction in S1 was associated with enhanced ventral hippocampal expression of CHD1 and reduced expression of CHD5 that was normalized following successful rescue of impaired fear extinction. Moreover, a select reduction in CHD3 expression was observed in the ventral hippocampus (vHC) following successful rescue of fear extinction in S1 mice. Taken together, these data provide novel insight into the regulation of specific ChRFs following an impaired cognitive process and its rescue, and they suggest that

  1. Temporal Dynamics of Recovery from Extinction Shortly after Extinction Acquisition

    ERIC Educational Resources Information Center

    Archbold, Georgina E.; Dobbek, Nick; Nader, Karim

    2013-01-01

    Evidence suggests that extinction is new learning. Memory acquisition involves both short-term memory (STM) and long-term memory (LTM) components; however, few studies have examined early phases of extinction retention. Retention of auditory fear extinction was examined at various time points. Shortly (1-4 h) after extinction acquisition…

  2. Early age-dependent impairments of context-dependent extinction learning, object recognition, and object-place learning occur in rats.

    PubMed

    Wiescholleck, Valentina; Emma André, Marion Agnès; Manahan-Vaughan, Denise

    2014-03-01

    The hippocampus is vulnerable to age-dependent memory decline. Multiple forms of memory depend on adequate hippocampal function. Extinction learning comprises active inhibition of no longer relevant learned information concurrent with suppression of a previously learned reaction. It is highly dependent on context, and evidence exists that it requires hippocampal activation. In this study, we addressed whether context-based extinction as well as hippocampus-dependent tasks, such as object recognition and object-place recognition, are equally affected by moderate aging. Young (7-8 week old) and older (7-8 month old) Wistar rats were used. For the extinction study, animals learned that a particular floor context indicated that they should turn into one specific arm (e.g., left) to receive a food reward. On the day after reaching the learning criterion of 80% correct choices, the floor context was changed, no reward was given and animals were expected to extinguish the learned response. Both, young and older rats managed this first extinction trial in the new context with older rats showing a faster extinction performance. One day later, animals were returned to the T-maze with the original floor context and renewal effects were assessed. In this case, only young but not older rats showed the expected renewal effect (lower extinction ratio as compared to the day before). To assess general memory abilities, animals were tested in the standard object recognition and object-place memory tasks. Evaluations were made at 5 min, 1 h and 7 day intervals. Object recognition memory was poor at short-term and intermediate time-points in older but not young rats. Object-place memory performance was unaffected at 5 min, but impaired at 1 h in older but not young rats. Both groups were impaired at 7 days. These findings support that not only aspects of general memory, but also context-dependent extinction learning, are affected by moderate aging. This may reflect less flexibility in

  3. Impaired extinction of learned contextual fear memory in early growth response 1 knockout mice.

    PubMed

    Han, Seungrie; Hong, Soontaek; Mo, Jiwon; Lee, Dongmin; Choi, Eunju; Choi, June-seek; Sun, Woong; Lee, Hyun Woo; Kim, Hyun

    2014-01-01

    Inductive expression of early growth response 1 (Egr-1) in neurons is associated with many forms of neuronal activity. However, only a few Egr-1 target genes are known in the brain. The results of this study demonstrate that Egr-1 knockout (KO) mice display impaired contextual extinction learning and normal fear acquisition relative to wild-type (WT) control animals. Genome-wide microarray experiments revealed 368 differentially expressed genes in the hippocampus of Egr-1 WT exposed to different phases of a fear conditioning paradigm compared to gene expression profiles in the hippocampus of KO mice. Some of genes, such as serotonin receptor 2C (Htr2c), neuropeptide B (Npb), neuronal PAS domain protein 4 (Npas4), NPY receptor Y1 (Npy1r), fatty acid binding protein 7 (Fabp7), and neuropeptide Y (Npy) are known to regulate processing of fearful memories, and promoter analyses demonstrated that several of these genes contained Egr-1 binding sites. This study provides a useful list of potential Egr-1 target genes which may be regulated during fear memory processing. PMID:24552706

  4. Hippocampal Context Processing during Acquisition of a Predictive Learning Task Is Associated with Renewal in Extinction Recall.

    PubMed

    Lissek, Silke; Glaubitz, Benjamin; Schmidt-Wilcke, Tobias; Tegenthoff, Martin

    2016-05-01

    Renewal is defined as the recovery of an extinguished response if extinction and retrieval contexts differ. The context dependency of extinction, as demonstrated by renewal, has important implications for extinction-based therapies. Persons showing renewal (REN) exhibit higher hippocampal activation during extinction in associative learning than those without renewal (NOREN), demonstrating hippocampal context processing, and recruit ventromedial pFC in retrieval. Apart from these findings, brain processes generating renewal remain largely unknown. Conceivably, processing differences in task-relevant brain regions that ultimately lead to renewal may occur already in initial acquisition of associations. Therefore, in two fMRI studies, we investigated overall brain activation and hippocampal activation in REN and NOREN during acquisition of an associative learning task in response to presentation of a context alone or combined with a cue. Results of two studies demonstrated significant activation differences between the groups: In Study 1, a support vector machine classifier correctly assigned participants' brain activation patterns to REN and NOREN groups, respectively. In Study 2, REN and NOREN showed similar hippocampal involvement during context-only presentation, suggesting processing of novelty, whereas overall hippocampal activation to the context-cue compound, suggesting compound encoding, was higher in REN. Positive correlations between hippocampal activation and renewal level indicated more prominent hippocampal processing in REN. Results suggest that hippocampal processing of the context-cue compound rather than of context only during initial learning is related to a subsequent renewal effect. Presumably, REN participants use distinct encoding strategies during acquisition of context-related tasks, which reflect in their brain activation patterns and contribute to a renewal effect. PMID:26807840

  5. Altered consolidation of extinction-like inhibitory learning in genotype-specific dysfunctional coping fostered by chronic stress in mice.

    PubMed

    Campus, P; Maiolati, M; Orsini, C; Cabib, S

    2016-12-15

    Genetic and stress-related factors interact to foster mental disorders, possibly through dysfunctional learning. In a previous study we reported that a temporary experience of reduced food availability increases forced swim (FS)-induced helplessness tested 14days after a first experience in mice of the standard inbred C57BL/6(B6) strain but reduces it in mice of the genetically unrelated DBA/2J (D2) strain. Because persistence of FS-induced helplessness influences adaptive coping with stress challenge and involve learning processes the present study tested whether the behavioral effects of restricted feeding involved altered consolidation of FS-related learning. First, we demonstrated that restricted feeding does not influence behavior expressed on the first FS experience, supporting a specific effect on persistence rather then development of helplessness. Second, we found that FS-induced c-fos expression in the infralimbic cortex (IL) was selectively enhanced in food-restricted (FR) B6 mice and reduced in FR D2 mice, supporting opposite alterations of consolidation processes involving this brain area. Third, we demonstrated that immediate post-FS inactivation of IL prevents 24h retention of acquired helplessness by continuously free-fed mice of both strains, indicating the requirement of a functioning IL for consolidation of FS-related learning in either mouse strain. Finally, in line with the known role of IL in consolidation of extinction memories, we found that restricted feeding selectively facilitated 24h retention of an acquired extinction in B6 mice whereas impairing it in D2 mice. These findings support the conclusion that an experience of reduced food availability strain-specifically affects persistence of newly acquired passive coping strategies by altering consolidation of extinction-like inhibitory learning. PMID:27506654

  6. AX+, BX- Discrimination Learning in the Fear-Potentiated Startle Paradigm: Possible Relevance to Inhibitory Fear Learning in Extinction

    ERIC Educational Resources Information Center

    Myers, Karyn M.; Davis, Michael

    2004-01-01

    The neural mechanisms of fear suppression most commonly are studied through the use of extinction, a behavioral procedure in which a feared stimulus (i.e., one previously paired with shock) is nonreinforced repeatedly, leading to a reduction or elimination of the fear response. Although extinction is perhaps the most convenient index of fear…

  7. Neural activations during visual sequence learning leave a trace in post-training spontaneous EEG.

    PubMed

    Moisello, Clara; Meziane, Hadj Boumediene; Kelly, Simon; Perfetti, Bernardo; Kvint, Svetlana; Voutsinas, Nicholas; Blanco, Daniella; Quartarone, Angelo; Tononi, Giulio; Ghilardi, Maria Felice

    2013-01-01

    Recent EEG studies have shown that implicit learning involving specific cortical circuits results in an enduring local trace manifested as local changes in spectral power. Here we used a well characterized visual sequence learning task and high density-(hd-)EEG recording to determine whether also declarative learning leaves a post-task, local change in the resting state oscillatory activity in the areas involved in the learning process. Thus, we recorded hd-EEG in normal subjects before, during and after the acquisition of the order of a fixed spatial target sequence (VSEQ) and during the presentation of targets in random order (VRAN). We first determined the temporal evolution of spectral changes during VSEQ and compared it to VRAN. We found significant differences in the alpha and theta bands in three main scalp regions, a right occipito-parietal (ROP), an anterior-frontal (AFr), and a right frontal (RFr) area. The changes in frontal theta power during VSEQ were positively correlated with the learning rate. Further, post-learning EEG recordings during resting state revealed a significant increase in alpha power in ROP relative to a pre-learning baseline. We conclude that declarative learning is associated with alpha and theta changes in frontal and posterior regions that occur during the task, and with an increase of alpha power in the occipito-parietal region after the task. These post-task changes may represent a trace of learning and a hallmark of use-dependent plasticity. PMID:23799058

  8. Neural Activations during Visual Sequence Learning Leave a Trace in Post-Training Spontaneous EEG

    PubMed Central

    Moisello, Clara; Meziane, Hadj Boumediene; Kelly, Simon; Perfetti, Bernardo; Kvint, Svetlana; Voutsinas, Nicholas; Blanco, Daniella; Quartarone, Angelo; Tononi, Giulio; Ghilardi, Maria Felice

    2013-01-01

    Recent EEG studies have shown that implicit learning involving specific cortical circuits results in an enduring local trace manifested as local changes in spectral power. Here we used a well characterized visual sequence learning task and high density-(hd-)EEG recording to determine whether also declarative learning leaves a post-task, local change in the resting state oscillatory activity in the areas involved in the learning process. Thus, we recorded hd-EEG in normal subjects before, during and after the acquisition of the order of a fixed spatial target sequence (VSEQ) and during the presentation of targets in random order (VRAN). We first determined the temporal evolution of spectral changes during VSEQ and compared it to VRAN. We found significant differences in the alpha and theta bands in three main scalp regions, a right occipito-parietal (ROP), an anterior-frontal (AFr), and a right frontal (RFr) area. The changes in frontal theta power during VSEQ were positively correlated with the learning rate. Further, post-learning EEG recordings during resting state revealed a significant increase in alpha power in ROP relative to a pre-learning baseline. We conclude that declarative learning is associated with alpha and theta changes in frontal and posterior regions that occur during the task, and with an increase of alpha power in the occipito-parietal region after the task. These post-task changes may represent a trace of learning and a hallmark of use-dependent plasticity. PMID:23799058

  9. Amphibian decline and extinction: what we know and what we need to learn.

    PubMed

    Collins, James P

    2010-11-01

    For over 350 million yr, thousands of amphibian species have lived on Earth. Since the 1980s, amphibians have been disappearing at an alarming rate, in many cases quite suddenly. What is causing these declines and extinctions? In the modern era (post 1500) there are 6 leading causes of biodiversity loss in general, and all of these acting alone or together are responsible for modern amphibian declines: commercial use; introduced/exotic species that compete with, prey on, and parasitize native frogs and salamanders; land use change; contaminants; climate change; and infectious disease. The first 3 causes are historical in the sense that they have been operating for hundreds of years, although the rate of change due to each accelerated greatly after about the mid-20th century. Contaminants, climate change, and emerging infectious diseases are modern causes suspected of being responsible for the so-called 'enigmatic decline' of amphibians in protected areas. Introduced/exotic pathogens, land use change, and infectious disease are the 3 causes with a clear role in amphibian decline as well as extinction; thus far, the other 3 causes are only implicated in decline and not extinction. The present work is a review of the 6 causes with a focus on pathogens and suggested areas where new research is needed. Batrachochytrium dendrobatidis (Bd) is a chytrid fungus that is an emerging infectious disease causing amphibian population decline and species extinction. Historically, pathogens have not been seen as a major cause of extinction, but Bd is an exception, which is why it is such an interesting, important pathogen to understand. The late 20th and early 21st century global biodiversity loss is characterized as a sixth extinction event. Amphibians are a striking example of these losses as they disappear at a rate that greatly exceeds historical levels. Consequently, modern amphibian decline and extinction is a lens through which we can view the larger story of biodiversity

  10. Effects of prior cocaine versus morphine or heroin self-administration on extinction learning driven by over-expectation versus omission of reward

    PubMed Central

    Lucantonio, Federica; Kambhampati, S; Haney, Richard Z; Atalayer, Deniz; Rowland, Neil E; Shaham, Yavin; Schoenbaum, Geoffrey

    2014-01-01

    Background Addiction is characterized by an inability to stop using drugs, despite adverse consequences. One contributing factor to this compulsive drug taking could be the impact of drug use on the ability to extinguish drug seeking after changes in expected outcomes. Here we compared effects of cocaine, morphine, and heroin self-administration on two forms of extinction learning: standard extinction driven by reward omission and extinction driven by reward over-expectation. Methods In Experiment 1, we trained rats to self-administer cocaine, morphine, or sucrose for 3 hr/day (limited access). In Experiment 2, we trained rats to self-administer heroin or sucrose for 12 hr/day (extended access). Three weeks later, we trained the rats to associate several cues with palatable food reward, after which we assessed extinction of the learned Pavlovian response, first by pairing two cues together in the over-expectation procedure and later by omitting the food reward. Results Rats trained under limited access conditions to self-administer sucrose or morphine demonstrated normal extinction in response to both over-expectation and reward omission, whereas cocaine-experienced rats or rats trained to self-administer heroin under extended access conditions exhibited normal extinction in response to reward omission but failed to show extinction in response to over-expectation. Conclusions The specific long-lasting effects of cocaine and heroin show that drug exposure induces long-lasting deficits in the ability to extinguish reward seeking after changes in expected outcomes. These deficits were not observed in a standard extinction procedure but instead only affected extinction learning driven by a more complex phenomenon of over-expectation. PMID:25641634

  11. Activation of the Infralimbic Cortex in a Fear Context Enhances Extinction Learning

    ERIC Educational Resources Information Center

    Thompson, Brittany M.; Baratta, Michael V.; Biedenkapp, Joseph C.; Rudy, Jerry W.; Watkins, Linda R.; Maier, Steven F.

    2010-01-01

    Activation of the infralimbic region (IL) of the medial prefrontal cortex (mPFC) reduces conditioned fear in a variety of situations, and the IL is thought to play an important role in the extinction of conditioned fear. Here we report a series of experiments using contextual fear conditioning in which the IL is activated with the GABAa antagonist…

  12. Extinction, Spontaneous Recovery and Renewal of Flavor Preferences Based on Taste-Taste Learning

    ERIC Educational Resources Information Center

    Diaz, Estrella; De la Casa, L. G.

    2011-01-01

    This paper presents evidence of extinction, spontaneous recovery and renewal in a conditioned preferences paradigm based on taste-taste associations. More specifically, in three experiments rats exposed to a simultaneous compound of citric acid-saccharin solution showed a preference for the citric solution when the preference was measured with a…

  13. The Metabotropic Glutamate Receptor, mGlu5, Is Required for Extinction Learning That Occurs in the Absence of a Context Change

    PubMed Central

    André, Marion Agnes Emma; Güntürkün, Onur; Manahan-Vaughan, Denise

    2015-01-01

    The metabotropic glutamate (mGlu) receptors and, in particular, mGlu5 are crucially involved in multiple forms of synaptic plasticity that are believed to underlie explicit memory. MGlu5 is also required for information transfer through neuronal oscillations and for spatial memory. Furthermore, mGlu5 is involved in extinction of implicit forms of learning. This places this receptor in a unique position with regard to information encoding. Here, we explored the role of this receptor in context-dependent extinction learning under constant, or changed, contextual conditions. Animals were trained over 3 days to take a left turn under 25% reward probability in a T-maze with a distinct floor pattern (Context A). On Day 4, they experienced either a floor pattern change (Context B) or the same floor pattern (Context A) in the absence of reward. After acquisition of the task, the animals were returned to the maze once more on Day 5 (Context A, no reward). Treatment with the mGlu5 antagonist, 2-methyl-6-(phenylethynyl) pyridine, before maze exposure on Day 4 completely inhibited extinction learning in the AAA paradigm but had no effect in the ABA paradigm. A subsequent return to the original context (A, on Day 5) revealed successful extinction in the AAA paradigm, but impairment of extinction in the ABA paradigm. These data support that although extinction learning in a new context is unaffected by mGlu5 antagonism, extinction of the consolidated context is impaired. This suggests that mGlu5 is intrinsically involved in enabling learning that once-relevant information is no longer valid. © 2014 The Authors. Hippocampus Published by Wiley Periodicals, Inc. PMID:25160592

  14. mGlu5 Receptors and Relapse to Cocaine-Seeking: The Role of Receptor Trafficking in Postrelapse Extinction Learning Deficits

    PubMed Central

    Knackstedt, Lori A.

    2016-01-01

    We have previously demonstrated that MTEP, an allosteric antagonist of mGlu5, infused into the nucleus accumbens attenuates relapse after abstinence from cocaine self-administration. MTEP infused into the dorsolateral striatum (dlSTR) does not alter relapse but has long-lasting effects on subsequent extinction learning. Here we tested whether systemic MTEP would prevent relapse after abstinence or alter extinction learning. We also investigated the mechanism of action by which intra-dlSTR MTEP on test day alters extinction on subsequent days. Animals self-administered cocaine for 12 days followed by abstinence for 20-21 days. MTEP (0.5–5 mg/kg IP) was administered prior to placement into the operant chamber for a context-primed relapse test. A separate group of animals received intra-dlSTR MTEP prior to the relapse test and were sacrificed day later. Systemic administration of MTEP attenuated abstinent-relapse without significantly affecting extinction learning. Surface biotinylation analysis of protein expression in the dlSTR revealed that, in cocaine animals, intra-dlSTR MTEP administration decreased mGlu5 surface expression and prevented changes in Arc and GluA1/GluA2 observed in their vehicle counterparts. Thus, blockade of mGlu5 receptors may be utilized in future treatment strategies for relapse prevention in humans, although the effects of chronic blockade on extinction learning should be further evaluated. PMID:26881139

  15. Potentiation of GluN2C/D NMDA receptor subtypes in the amygdala facilitates the retention of fear and extinction learning in mice.

    PubMed

    Ogden, Kevin K; Khatri, Alpa; Traynelis, Stephen F; Heldt, Scott A

    2014-02-01

    NMDA receptors are glutamate receptor ion channels that contribute to synaptic plasticity and are important for many forms of learning and memory. In the amygdala, NMDA receptors are critical for the acquisition, retention, and extinction of classically conditioned fear responses. Although the GluN2B subunit has been implicated in both the acquisition and extinction of conditioned fear, GluN2C-knockout mice show reduced conditioned fear responses. Moreover, D-cycloserine (DCS), which facilitates fear extinction, selectively enhances the activity of GluN2C-containing NMDA receptors. To further define the contribution of GluN2C receptors to fear learning, we infused the GluN2C/GluN2D-selective potentiator CIQ bilaterally into the basolateral amygdala (3, 10, or 30 μg/side) following either fear conditioning or fear extinction training. CIQ both increased the expression of conditioned fear 24 h later and enhanced the extinction of the previously conditioned fear response. These results support a critical role for GluN2C receptors in the amygdala in the consolidation of learned fear responses and suggest that increased activity of GluN2C receptors may underlie the therapeutic actions of DCS. PMID:24008353

  16. Learning and extinction of conditioned hearing sensation change in the beluga whale (Delphinapterus leucas).

    PubMed

    Nachtigall, Paul E; Supin, Alexander Ya; Estaban, Jose-Antonio; Pacini, Aude F

    2016-02-01

    Ice-dwelling beluga whales are increasingly being exposed to anthropogenic loud sounds. Beluga's hearing sensitivity measured during a warning sound just preceding a loud sound was tested using pip-train stimuli and auditory evoked potential recording. When the test/warning stimulus with a frequency of 32 or 45 kHz preceded the loud sound with a frequency of 32 kHz and a sound pressure level of 153 dB re 1 μPa, 2 s, hearing thresholds before the loud sound increased relative to the baseline. The threshold increased up to 15 dB for the test frequency of 45 kHz and up to 13 dB for the test frequency of 32 kHz. These threshold increases were observed during two sessions of 36 trials each. Extinction tests revealed no change during three experimental sessions followed by a jump-like return to baseline thresholds. The low exposure level producing the hearing-dampening effect (156 dB re 1 µPa(2)s in each trial), and the manner of extinction, may be considered as evidence that the observed hearing threshold increases were a demonstration of conditioned dampening of hearing when the whale anticipated the quick appearance of a loud sound in the same way demonstrated in the false killer whale and bottlenose dolphin. PMID:26659822

  17. Stimulation of the noradrenergic system during memory formation impairs extinction learning but not the disruption of reconsolidation.

    PubMed

    Soeter, Marieke; Kindt, Merel

    2012-04-01

    The noradrenergic system plays a critical role in the 'consolidation' of emotional memory. If we are to target 'reconsolidation' in patients with anxiety disorders, the noradrenergic strengthening of fear memory should not impair the disruption of reconsolidation. In Experiment I, we addressed this issue using a differential fear conditioning procedure allowing selective reactivation of one of two fear associations. First, we strengthened fear memory by administering an α(2)-adrenergic receptor antagonist (ie, yohimbine HCl; double-blind placebo-controlled study) 30 min before acquisition (time for peak value yohimbine HCl <1 h). Next, the reconsolidation of one of the fear associations was manipulated by administering a β-adrenergic receptor antagonist (ie, propranolol HCl) 90 min before its selective reactivation (time for peak value propranolol HCl <2 h). In Experiment II, we administered propranolol HCl after reactivation of the memory to rule out a possible effect of the pharmacological manipulation on the memory retrieval itself. The excessive release of noradrenaline during memory formation not only delayed the process of extinction 48 h later, but also triggered broader fear generalization. Yet, the β-adrenergic receptor blocker during reconsolidation selectively 'neutralized' the fear-arousing aspects of the noradrenergic-strengthened memory and undermined the generalization of fear. We observed a similar reduction in fear responding when propranolol HCl was administered after reactivation of the memory. The present findings demonstrate the involvement of noradrenergic modulation in the formation as well as generalization of human fear memory. Given that the noradrenergic strengthening of fear memory impaired extinction learning but not the disruption of reconsolidation, our findings may have implications for the treatment of anxiety disorders. PMID:22169947

  18. The role of ventral and dorsal striatum mGluR5 in relapse to cocaine-seeking and extinction learning.

    PubMed

    Knackstedt, Lori A; Trantham-Davidson, Heather L; Schwendt, Marek

    2014-01-01

    Cocaine addiction is a chronic, relapsing disease characterized by an inability to regulate drug-seeking behavior. Here we investigated the role of mGluR5 in the ventral and dorsal striatum in regulating cocaine-seeking following both abstinence and extinction. Animals underwent 2 weeks of cocaine self-administration followed by 3 weeks of home-cage abstinence. Animals were then reintroduced to the operant chamber for a context-induced relapse test, followed by 7-10 days of extinction training. Once responding was extinguished, cue-primed reinstatement test was conducted. Both drug-seeking tests were conducted in the presence of either mGluR5 negative allosteric modulator, MTEP or vehicle infused into either the nucleus accumbens (NA) core or dorsolateral striatum (dSTR). We found that MTEP infused in the NA core attenuated both context-induced relapse following abstinence and cue-primed reinstatement following extinction training. Blocking dSTR mGluR5 had no effect on context- or cue-induced cocaine-seeking. However, the intra-dSTR MTEP infusion on the context-induced relapse test day attenuated extinction learning for 4 days after the infusion. Furthermore, mGluR5 surface expression was reduced and LTD was absent in dSTR slices of animals undergoing 3 weeks of abstinence from cocaine but not sucrose self-administration. LTD was restored by bath application of VU-29, a positive allosteric modulator of mGluR5. Bath application of MTEP prevented the induction of LTD in dSTR slices from sucrose animals. Taken together, this data indicates that dSTR mGluR5 plays an essential role in extinction learning but not cocaine relapse, while NA core mGluR5 modulates drug-seeking following both extinction and abstinence from cocaine self-administration. PMID:23710649

  19. Zinc Transporter 3 Is Involved in Learned Fear and Extinction, but Not in Innate Fear

    ERIC Educational Resources Information Center

    Martel, Guillaume; Hevi, Charles; Friebely, Olivia; Baybutt, Trevor; Shumyatsky, Gleb P.

    2010-01-01

    Synaptically released Zn[superscript 2+] is a potential modulator of neurotransmission and synaptic plasticity in fear-conditioning pathways. Zinc transporter 3 (ZnT3) knock-out (KO) mice are well suited to test the role of zinc in learned fear, because ZnT3 is colocalized with synaptic zinc, responsible for its transport to synaptic vesicles,…

  20. Genetic Inactivation of D-Amino Acid Oxidase Enhances Extinction and Reversal Learning in Mice

    ERIC Educational Resources Information Center

    Labrie, Viviane; Duffy, Steven; Wang, Wei; Barger, Steven W.; Baker, Glen B.; Roder, John C.

    2009-01-01

    Activation of the N-methyl-d-aspartate receptor (NMDAR) glycine site has been shown to accelerate adaptive forms of learning that may benefit psychopathologies involving cognitive and perseverative disturbances. In this study, the effects of increasing the brain levels of the endogenous NMDAR glycine site agonist D-serine, through the genetic…

  1. Facing Extinction: Organizational Learning in a Small Secondary School under Duress

    ERIC Educational Resources Information Center

    Symons, Cam

    2005-01-01

    This study examined the process of organizational learning in a small secondary school in a company town during a protracted period of turbulence, arising from the downsizing of the community's main employer. The hypothesis was that distributed leadership among school staff created a change in teaching practices from a limited repertoire of…

  2. A developmental analysis of threat/safety learning and extinction recall during middle childhood.

    PubMed

    Michalska, Kalina J; Shechner, Tomer; Hong, Melanie; Britton, Jennifer C; Leibenluft, Ellen; Pine, Daniel S; Fox, Nathan A

    2016-06-01

    The current study examined developmental changes in fear learning and generalization in 54 healthy 5-10-year old children using a novel fear conditioning paradigm. In this task, the conditioned stimuli (CS+/CS-) were two blue and yellow colored cartoon bells, and the unconditioned stimulus was an unpleasant loud alarm sound presented with a red cartoon bell. Physiological and subjective data were acquired. Three weeks after conditioning, 48 of these participants viewed the CS-, CS+, and morphed images resembling the CS+. Participants made threat-safety discriminations while appraising threat and remembering the CS+. Although no age-related differences in fear learning emerged, patterns of generalization were qualified by child age. Older children demonstrated better discrimination between the CS+ and CS morphs than younger age groups and also reported more fear to stimuli resembling the CS+ than younger children. Clinical implications and future directions are discussed. PMID:26922673

  3. Extinction in multiple contexts: Effects on the rate of extinction and the strength of response recovery.

    PubMed

    Bustamante, Javier; Uengoer, Metin; Thorwart, Anna; Lachnit, Harald

    2016-09-01

    In two human predictive-learning experiments, we investigated the effects of extinction in multiple contexts on the rate of extinction and the strength of response recovery. In each experiment, participants initially received acquisition training with a target cue in one context, followed by extinction either in a different context (extinction in a single context) or in three different contexts (extinction in multiple contexts). The results of both experiments showed that conducting extinction in multiple contexts led to higher levels of responding during extinction than did extinction in a single context. Additionally, Experiment 2 showed that extinction in multiple contexts prevented ABC renewal but had no detectable impact on ABA renewal. Our results are discussed within the framework of contemporary learning theories of contextual control and extinction. PMID:26895976

  4. Reorganization of Learning-Associated Prefrontal Synaptic Plasticity between the Recall of Recent and Remote Fear Extinction Memory

    ERIC Educational Resources Information Center

    Hugues, Sandrine; Garcia, Rene

    2007-01-01

    We have previously shown that fear extinction is accompanied by an increase of synaptic efficacy in inputs from the ventral hippocampus (vHPC) and mediodorsal thalamus (MD) to the medial prefrontal cortex (mPFC) and that disrupting these changes to mPFC synaptic transmission compromises extinction processes. The aim of this study was to examine…

  5. Cognitive Processes in Extinction

    ERIC Educational Resources Information Center

    Lovibond, Peter F.

    2004-01-01

    Human conditioning research shows that learning is closely related to consciously available contingency knowledge, requires attentional resources, and is influenced by language. This research suggests a cognitive model in which extinction consists of changes in contingency beliefs in long-term memory. Laboratory and clinical evidence on extinction…

  6. Extinction with multiple excitors

    PubMed Central

    McConnell, Bridget L.; Miguez, Gonzalo; Miller, Ralph R.

    2012-01-01

    Four conditioned suppression experiments with rats, using an ABC renewal design, investigated the effects of compounding the target conditioned excitor with additional, nontarget conditioned excitors during extinction. Experiment 1 showed stronger extinction, as evidenced by less renewal, when the target excitor was extinguished in compound with a second excitor, relative to when it was extinguished with associatively neutral stimuli. Critically, this deepened extinction effect was attenuated (i.e., more renewal occurred) when a third excitor was added during extinction training. This novel demonstration contradicts the predictions of associative learning models based on total error reduction, but it is explicable in terms of a counteraction effect within the framework of the extended comparator hypothesis. The attenuated deepened extinction effect was replicated in Experiments 2a and 3, which also showed that pretraining consisting of weakening the association between the two additional excitors (Experiments 2a and 2b) or weakening the association between one of the additional excitors and the unconditioned stimulus (Experiment 3) attenuated the counteraction effect, thereby resulting in a decrease in responding to the target excitor. These results suggest that more than simple total error reduction determines responding after extinction. PMID:23055103

  7. The extinction properties of forest components

    NASA Technical Reports Server (NTRS)

    Karam, M. A.; Fung, A. K.; Blanchard, A. J.; Nance, C. E.

    1988-01-01

    The effect of each forest component on the extinction of electromagnetic waves is investigated by modeling the branches with finite cylinders, deciduous leaves with elliptic disks, and coniferous leaves with needles. The inner field is estimated by the field inside an infinitely long cylinder of similar properties for the branches, and by the Shifrin approximation for the leaves. For each forest component analytic expressions were derived for the extinction cross section via the forward scattering theorem and for ohmic and scattered losses. For branches, the variation of the extinction cross section obtained via the forward scattering theorem is illustrated numerically as a function of the branch radius and the imaginery part of its dielectric constant. It is compared with the measurements from a single branch. For the leaves, the forward scattering theorem gives value for the extinction cross section equal to the ohmic cross section.

  8. Extinctions of life

    NASA Technical Reports Server (NTRS)

    Sepkoski, J. J. Jr; Sepkoski JJ, J. r. (Principal Investigator)

    1988-01-01

    This meeting presentation examines mass extinctions through earth's history. Extinctions are charted for marine families and marine genera. Timing of marine genera extinctions is discussed. Periodicity in extinctions during the Mesozoic and Cenozoic eras is plotted and compared with Paleozoic extinction peaks. The role of extinction in evolution and mankind's role in present extinctions are examined.

  9. Chronic administration of cardanol (ginkgol) extracted from ginkgo biloba leaves and cashew nutshell liquid improves working memory-related learning in rats.

    PubMed

    Tobinaga, Seisho; Hashimoto, Michio; Utsunomiya, Iku; Taguchi, Kyoji; Nakamura, Morihiko; Tsunematsu, Tokugoro

    2012-01-01

    Cardanol (ginkgol) extracted from Ginkgo biloba leaves and cashew nutshell liquid enhances the growth of NSC-34 immortalized motor neuron-like cells and, when chronically administered to young rats, improves working memory-related learning ability as assessed by eight-arm radial maze tasks. These findings suggest that cardanol is one of the components in Ginkgo biloba leaves that improves cognitive learning ability. PMID:22223349

  10. Australian Extinctions

    ERIC Educational Resources Information Center

    Science Teacher, 2005

    2005-01-01

    Massive extinctions of animals and the arrival of the first humans in ancient Australia--which occurred 45,000 to 55,000 years ago--may be linked. Researchers at the Carnegie Institution, University of Colorado, Australian National University, and Bates College believe that massive fires set by the first humans may have altered the ecosystem of…

  11. Leaving School — learning at SEA: Regular high school education alongside polar research

    NASA Astrophysics Data System (ADS)

    Gatti, Susanne

    2010-05-01

    Against the background of unsatisfactory results from the international OECD study PISA (Program for International Student Assessment), Germany is facing a period of intense school reforms. Looking back at a tradition of school culture with too few changes during the last century, quick and radical renewal of the school system is rather unlikely. Furthermore students are increasingly turning away from natural sciences [1]. The AWI aims at providing impulses for major changes in the schooling system and is offering solid science education not only for university students but also for a larger audience. All efforts towards this goal are interconnected within the project SEA (Science & Education @ the AWI). With the school-term of 2002/03 the Alfred-Wegener-Institute for Polar and Marine Research started HIGHSEA (High school of SEA). The program is the most important component of SEA. Each year 22 high school students (grade 10 or 11) are admitted to HIGHSEA spending their last three years of school not at school but at the institute. Four subjects (biology as a major, chemistry, math and English as accessory subjects) are combined and taught fully integrated. Students leave their school for two days each week to study, work and explore all necessary topics at the AWI. All of the curricular necessities of the four subjects have been rearranged in their temporal sequencing thus enabling a conceptual formulation of four major questions to be dealt with in the course of the three-year program [2]. Students are taught by teachers of the cooperation schools as well as by scientists of the AWI. Close links and intense cooperation between both groups are the basis of fundamental changes in teaching and learning climate. We are organizing expeditions for every group of HIGHSEA-students (e. g. to the Arctic or to mid-Atlantic seamounts). For each student expedition we devise a "real" research question. Usually a single working group at the AWI has a special interest in the

  12. Context and Behavioral Processes in Extinction

    ERIC Educational Resources Information Center

    Bouton, Mark E.

    2004-01-01

    This article provides a selective review and integration of the behavioral literature on Pavlovian extinction. The first part reviews evidence that extinction does not destroy the original learning, but instead generates new learning that is especially context-dependent. The second part examines insights provided by research on several related…

  13. Immediate Extinction Causes a Less Durable Loss of Performance than Delayed Extinction following Either Fear or Appetitive Conditioning

    ERIC Educational Resources Information Center

    Woods, Amanda M.; Bouton, Mark E.

    2008-01-01

    Five experiments with rat subjects compared the effects of immediate and delayed extinction on the durability of extinction learning. Three experiments examined extinction of fear conditioning (using the conditioned emotional response method), and two experiments examined extinction of appetitive conditioning (using the food-cup entry method). In…

  14. Researchers Leave Labs, Flock to Schools for a New Look at How Students Learn.

    ERIC Educational Resources Information Center

    Winkler, Karen J.

    1992-01-01

    Increasingly, researchers in the social sciences are joining education scholars and studying basic issues in learning, including how children can be actively engaged in learning, effects of educational setting, and assessment of learning. The interest is prompted by availability of funding for applied research and by broader intellectual trends.…

  15. Infralimbic D2 receptors are necessary for fear extinction and extinction-related tone responses

    PubMed Central

    Mueller, Devin; Bravo-Rivera, Christian; Quirk, Gregory J.

    2010-01-01

    Background Fear extinction is dependent on plasticity in the infralimbic prefrontal cortex (IL), an area heavily innervated by midbrain dopaminergic inputs. Dopamine D2 receptors are concentrated in infralimbic output neurons that are involved in the suppression of conditioned fear after extinction. Here we examined the specific role of the D2 receptor in mediating associative learning underlying fear extinction, using the selective D2 antagonist raclopride. Methods Raclopride was administered systemically or infused into IL prior to fear extinction, and extinction retention was tested the following day. Rats were also prepared for single unit recording in IL to assess the effect of raclopride on firing properties. Results We found that systemic injection of raclopride given prior to extinction impaired retrieval of extinction when tested drug free the next day, but also induced catalepsy during extinction training. To determine whether impaired extinction was due to impaired motor function or disruption of extinction consolidation, we infused raclopride directly into IL. Raclopride infused immediately before extinction training did not produce motor deficits, but impaired recall of extinction when tested drug free. Furthermore, in animals that underwent extinction training, systemic raclopride reduced the tone responsiveness of IL neurons in layers 5/6, with no changes in average firing rate. Conclusion We suggest that D2 receptors facilitate extinction by increasing the signal-to-noise of IL neurons that consolidate extinction. PMID:20926066

  16. Electromagnetic wave extinction within a forested canopy

    NASA Technical Reports Server (NTRS)

    Karam, M. A.; Fung, A. K.

    1989-01-01

    A forested canopy is modeled by a collection of randomly oriented finite-length cylinders shaded by randomly oriented and distributed disk- or needle-shaped leaves. For a plane wave exciting the forested canopy, the extinction coefficient is formulated in terms of the extinction cross sections (ECSs) in the local frame of each forest component and the Eulerian angles of orientation (used to describe the orientation of each component). The ECSs in the local frame for the finite-length cylinders used to model the branches are obtained by using the forward-scattering theorem. ECSs in the local frame for the disk- and needle-shaped leaves are obtained by the summation of the absorption and scattering cross-sections. The behavior of the extinction coefficients with the incidence angle is investigated numerically for both deciduous and coniferous forest. The dependencies of the extinction coefficients on the orientation of the leaves are illustrated numerically.

  17. Genetic gating of human fear learning and extinction: possible implications for gene-environment interaction in anxiety disorder.

    PubMed

    Lonsdorf, Tina B; Weike, Almut I; Nikamo, Pernilla; Schalling, Martin; Hamm, Alfons O; Ohman, Arne

    2009-02-01

    Pavlovian fear conditioning is a widely used model of the acquisition and extinction of fear. Neural findings suggest that the amygdala is the core structure for fear acquisition, whereas prefrontal cortical areas are given pivotal roles in fear extinction. Forty-eight volunteers participated in a fear-conditioning experiment, which used fear potentiation of the startle reflex as the primary measure to investigate the effect of two genetic polymorphisms (5-HTTLPR and COMTval158met) on conditioning and extinction of fear. The 5-HTTLPR polymorphism, located in the serotonin transporter gene, is associated with amygdala reactivity and neuroticism, whereas the COMTval158met polymorphism, which is located in the gene coding for catechol-O-methyltransferase (COMT), a dopamine-degrading enzyme, affects prefrontal executive functions. Our results show that only carriers of the 5-HTTLPR s allele exhibited conditioned startle potentiation, whereas carriers of the COMT met/met genotype failed to extinguish conditioned fear. These results may have interesting implications for understanding gene-environment interactions in the development and treatment of anxiety disorders. PMID:19175757

  18. The Best Distance Learning Graduate Schools: Earning Your Degree without Leaving Home.

    ERIC Educational Resources Information Center

    Phillips, Vicky; Yager, Cindy

    This book profiles 195 accredited institutions that offer graduate degrees via distance learning. The first section of the book examines the following topics of interest to individuals contemplating graduate study through a distance learning program: the increasing numbers of people embarking on graduate study later in life; the quality and…

  19. Learning to Leave Liberalism...And Live with Complicity, Conundrum and Moral Chagrin

    ERIC Educational Resources Information Center

    Boyd, Dwight

    2011-01-01

    This paper is a story of personal learning. I locate its beginning in my early, comfortable adoption of liberalism as the preferred perspective for my work as a philosopher of education. I then trace how and why I became disaffected with this perspective. I describe how learning from students, feminism and critical race theory led to an acceptance…

  20. Impossible Extinction

    NASA Astrophysics Data System (ADS)

    Cockell, Charles S.

    2003-03-01

    Every 225 million years the Earth, and all the life on it, completes one revolution around the Milky Way Galaxy. During this remarkable journey, life is influenced by calamitous changes. Comets and asteroids strike the surface of the Earth, stars explode, enormous volcanoes erupt, and, more recently, humans litter the planet with waste. Many animals and plants become extinct during the voyage, but humble microbes, simple creatures made of a single cell, survive this journey. This book takes a tour of the microbial world, from the coldest and deepest places on Earth to the hottest and highest, and witnesses some of the most catastrophic events that life can face. Impossible Extinction tells this remarkable story to the general reader by explaining how microbes have survived on Earth for over three billion years. Charles Cockell received his doctorate from the University of Oxford, and is currently a microbiologist with rhe Search for Extraterrestrial Intelligence Institute (SETI), based at the British Antarctic Survey in Cambridge, UK. His research focusses on astrobiology, life in the extremes and the human exploration of Mars. Cockell has been on expeditions to the Arctic, Antarctic, Mongolia, and in 1993 he piloted a modified insect-collecting ultra-light aircraft over the Indonesian rainforests. He is Chair of the Twenty-one Eleven Foundation for Exploration, a charity that supports expeditions that forge links between space exploration and environmentalism.

  1. Water, Weeds and Autumn Leaves: Learning to Be Drier in the Alpine Region

    ERIC Educational Resources Information Center

    Foley, Annette; Grace, Lauri

    2009-01-01

    Our paper explores how and what adults living and working in the Alpine region of Victoria understand and are learning about the changes to water availability, in a time when the response to water availability is subject to extensive debate and policy attention. Interviews for this study were conducted in the towns of Bright and Mount Beauty, with…

  2. Extinction memory is impaired in schizophrenia

    PubMed Central

    Holt, Daphne. J.; Lebron-Milad, Kelimer; Milad, Mohammed R.; Rauch, Scott L.; Pitman, Roger K.; Orr, Scott P.; Cassidy, Brittany S.; Walsh, Jared P.; Goff, Donald C.

    2013-01-01

    Background Schizophrenia is associated with abnormalities in emotional processing and social cognition, which may result from disruption of the underlying neural mechanism(s) governing emotional learning and memory. To investigate this possibility, we measured the acquisition and extinction of conditioned fear responses and delayed recall of extinction in schizophrenia and control subjects. Methods 28 schizophrenia and 18 demographically-matched control subjects underwent a two-day fear conditioning, extinction learning and extinction recall procedure, in which skin conductance response (SCR) magnitude was used as the index of conditioned responses. Results During fear acquisition, 83% of the controls and 57% of the patients showed autonomic responsivity (‘responders’), and the patients showed larger SCRs to the stimulus that was not paired with the unconditioned stimulus (CS−) than the controls. Within the responder group, there was no difference between the patients and controls in levels of extinction learning; however, the schizophrenia patients showed significant impairment, relative to the controls, in context-dependent recall of the extinction memory. In addition, delusion severity in the patients correlated with baseline skin conductance levels. Conclusions These data are consistent with prior evidence for a heightened neural response to innocuous stimuli in schizophrenia and elevated arousal levels in psychosis. The finding of deficient extinction recall in schizophrenia patients who showed intact extinction learning suggests that schizophrenia is associated with a disturbance in the neural processes supporting emotional memory. PMID:18986648

  3. Outcome-Specific Transfer between Predictive and Instrumental Learning Is Unaffected by Extinction but Reversed by Counterconditioning in Human Participants

    ERIC Educational Resources Information Center

    Rosas, Juan M.; Paredes-Olay, Maria C.; Garcia-Gutierrez, Ana; Espinosa, Juan J.; Abad, Maria J. F.

    2010-01-01

    Three experiments were conducted to explore the effects of different interference treatments upon outcome-specific transfer from predictive learning to instrumental responding. A computer game was designed in which participants had to defend Andalusia from navy and air-force attacks. Participants learned the relationship between two instrumental…

  4. A sphingolipid mechanism for behavioral extinction.

    PubMed

    Huston, Joseph P; Kornhuber, Johannes; Mühle, Christiane; Japtok, Lukasz; Komorowski, Mara; Mattern, Claudia; Reichel, Martin; Gulbins, Erich; Kleuser, Burkhard; Topic, Bianca; De Souza Silva, Maria A; Müller, Christian P

    2016-05-01

    Reward-dependent instrumental behavior must continuously be re-adjusted according to environmental conditions. Failure to adapt to changes in reward contingencies may incur psychiatric disorders like anxiety and depression. When an expected reward is omitted, behavior undergoes extinction. While extinction involves active re-learning, it is also accompanied by emotional behaviors indicative of frustration, anxiety, and despair (extinction-induced depression). Here, we report evidence for a sphingolipid mechanism in the extinction of behavior. Rapid extinction, indicating efficient re-learning, coincided with a decrease in the activity of the enzyme acid sphingomyelinase (ASM), which catalyzes turnover of sphingomyelin to ceramide, in the dorsal hippocampus of rats. The stronger the decline in ASM activity, the more rapid was the extinction. Sphingolipid-focused lipidomic analysis showed that this results in a decline of local ceramide species in the dorsal hippocampus. Ceramides shape the fluidity of lipid rafts in synaptic membranes and by that way can control neural plasticity. We also found that aging modifies activity of enzymes and ceramide levels in selective brain regions. Aging also changed how the chronic treatment with corticosterone (stress) or intranasal dopamine modified regional enzyme activity and ceramide levels, coinciding with rate of extinction. These data provide first evidence for a functional ASM-ceramide pathway in the brain involved in the extinction of learned behavior. This finding extends the known cellular mechanisms underlying behavioral plasticity to a new class of membrane-located molecules, the sphingolipids, and their regulatory enzymes, and may offer new treatment targets for extinction- and learning-related psychopathological conditions. Sphingolipids are common lipids in the brain which form lipid domains at pre- and postsynaptic membrane compartments. Here we show a decline in dorsal hippocampus ceramide species together with a

  5. Cannabinoid facilitation of fear extinction memory recall in humans

    PubMed Central

    Rabinak, Christine A.; Angstadt, Mike; Sripada, Chandra S.; Abelson, James L.; Liberzon, Israel; Milad, Mohammed R.; Phan, K. Luan

    2012-01-01

    A first-line approach to treat anxiety disorders is exposure-based therapy, which relies on extinction processes such as repeatedly exposing the patient to stimuli (conditioned stimuli; CS) associated with the traumatic, fear-related memory. However, a significant number of patients fail to maintain their gains, partly attributed to the fact that this inhibitory learning and its maintenance is temporary and conditioned fear responses can return. Animal studies have shown that activation of the cannabinoid system during extinction learning enhances fear extinction and its retention. Specifically, CB1 receptor agonists, such as Δ9-tetrahydrocannibinol (THC), can facilitate extinction recall by preventing recovery of extinguished fear in rats. However, this phenomenon has not been investigated in humans. We conducted a study using a randomized, double-blind, placebo-controlled, between-subjects design, coupling a standard Pavlovian fear extinction paradigm and simultaneous skin conductance response (SCR) recording with an acute pharmacological challenge with oral dronabinol (synthetic THC) or placebo (PBO) 2 hours prior to extinction learning in 29 healthy adult volunteers (THC = 14; PBO = 15) and tested extinction retention 24 hours after extinction learning. Compared to subjects that received PBO, subjects that received THC showed low SCR to a previously extinguished CS when extinction memory recall was tested 24 hours after extinction learning, suggesting that THC prevented the recovery of fear. These results provide the first evidence that pharmacological enhancement of extinction learning is feasible in humans using cannabinoid system modulators, which may thus warrant further development and clinical testing. PMID:22796109

  6. An Efficient Leave-One-Out Cross-Validation-Based Extreme Learning Machine (ELOO-ELM) With Minimal User Intervention.

    PubMed

    Shao, Zhifei; Er, Meng Joo; Wang, Ning

    2016-08-01

    It is well known that the architecture of the extreme learning machine (ELM) significantly affects its performance and how to determine a suitable set of hidden neurons is recognized as a key issue to some extent. The leave-one-out cross-validation (LOO-CV) is usually used to select a model with good generalization performance among potential candidates. The primary reason for using the LOO-CV is that it is unbiased and reliable as long as similar distribution exists in the training and testing data. However, the LOO-CV has rarely been implemented in practice because of its notorious slow execution speed. In this paper, an efficient LOO-CV formula and an efficient LOO-CV-based ELM (ELOO-ELM) algorithm are proposed. The proposed ELOO-ELM algorithm can achieve fast learning speed similar to the original ELM without compromising the reliability feature of the LOO-CV. Furthermore, minimal user intervention is required for the ELOO-ELM, thus it can be easily adopted by nonexperts and implemented in automation processes. Experimentation studies on benchmark datasets demonstrate that the proposed ELOO-ELM algorithm can achieve good generalization with limited user intervention while retaining the efficiency feature. PMID:26259254

  7. Serotonergic antidepressants decrease hedonic signals but leave learning signals in the nucleus accumbens unaffected.

    PubMed

    Graf, Heiko; Metzger, Coraline D; Walter, Martin; Abler, Birgit

    2016-01-01

    Investigating the effects of serotonergic antidepressants on neural correlates of visual erotic stimulation revealed decreased reactivity within the dopaminergic reward network along with decreased subjective sexual functioning compared with placebo. However, a global dampening of the reward system under serotonergic drugs is not intuitive considering clinical observations of their beneficial effects in the treatment of depression. Particularly, learning signals as coded in prediction error processing within the dopaminergic reward system can be assumed to be rather enhanced as antidepressant drugs have been demonstrated to facilitate the efficacy of psychotherapeutic interventions relying on learning processes. Within the same study sample, we now explored the effects of serotonergic and dopaminergic/noradrenergic antidepressants on prediction error signals compared with placebo by functional MRI. A total of 17 healthy male participants (mean age: 25.4 years) were investigated under the administration of paroxetine, bupropion and placebo for 7 days each within a randomized, double-blind, within-subject cross-over design. During functional MRI, we used an established monetary incentive task to explore neural prediction error signals within the bilateral nucleus accumbens as region of interest within the dopaminergic reward system. In contrast to diminished neural activations and subjective sexual functioning under the serotonergic agent paroxetine under visual erotic stimulation, we revealed unaffected or even enhanced neural prediction error processing within the nucleus accumbens under this antidepressant along with unaffected behavioural processing. Our study provides evidence that serotonergic antidepressants facilitate prediction error signalling and may support suggestions of beneficial effects of these agents on reinforced learning as an essential element in behavioural psychotherapy. PMID:26555033

  8. Fibroblast Growth Factor-2 Alters the Nature of Extinction

    ERIC Educational Resources Information Center

    Graham, Bronwyn M.; Richardson, Rick

    2011-01-01

    These experiments examined the effects of the NMDA-receptor (NMDAr) antagonist MK801 on reacquisition and re-extinction of a conditioned fear that had been previously extinguished before injection of fibroblast growth factor-2 (FGF2) or vehicle. Recent findings have shown that relearning and re-extinction, unlike initial learning and extinction,…

  9. The extinction context enables extinction performance after a change in context

    PubMed Central

    Nelson, James Byron; Gregory, Pamela; Sanjuan, Maria del Carmen

    2012-01-01

    One experiment with human participants determined the extent to which recovery of extinguished responding with a context switch was due to a failure to retrieve contextually-controlled learning, or some other process such as participants learning that context changes signal reversals in the meaning of stimulus – outcome relationships. In a video game, participants learned to suppress mouse clicking in the presence of a stimulus that predicted an attack. Then, that stimulus underwent extinction in a different context (environment within the game). Following extinction, suppression was recovered and then extinguished again during testing in the conditioning context. In a final test, participants that were tested in the context where extinction first took place showed less of a recovery than those tested in a neutral context, but they showed a recovery of suppression nevertheless. A change in context tended to cause a change in the meaning of the stimulus, leading to recovery in both the neutral and extinction contexts. The extinction context attenuated that recovery, perhaps by enabling retrieval of the learning that took place in extinction. Recovery outside an extinction context is due to a failure of the context to enable the learning acquired during extinction, but only in part. PMID:22521549

  10. NMDA receptor blockade in the basolateral amygdala disrupts consolidation of stimulus-reward memory and extinction learning during reinstatement of cocaine-seeking in an animal model of relapse.

    PubMed

    Feltenstein, Matthew W; See, Ronald E

    2007-11-01

    Previous research from our laboratory has implicated the basolateral amygdala (BLA) complex in the acquisition and consolidation of cue-cocaine associations, as well as extinction learning, which may regulate the long-lasting control of conditioned stimuli (CS) over drug-seeking behavior. Given the well established role of NMDA glutamate receptor activation in other forms of amygdalar-based learning, we predicted that BLA-mediated drug-cue associative learning would be NMDA receptor dependent. To test this hypothesis, male Sprague-Dawley rats self-administered i.v. cocaine (0.6 mg/kg/infusion) in the absence of explicit CS pairings (2-h sessions, 5 days), followed by a single 1-h classical conditioning (CC) session, during which they received passive infusions of cocaine discretely paired with a light+tone stimulus complex. Following additional cocaine self-administration sessions in the absence of the CS (2-h sessions, 5 days) and extinction training sessions (no cocaine or CS presentation, 2-h sessions, 7 days), the ability of the CS to reinstate cocaine-seeking on three test days was assessed. Rats received bilateral intra-BLA infusions (0.5 microl/hemisphere) of vehicle or the selective NMDA receptor antagonist, 2-amino-5-phosphonovalerate (AP-5), immediately prior to the CC session (acquisition), immediately following the CC session (consolidation), or immediately following reinstatement testing (consolidation of conditioned-cued extinction learning). AP-5 administered before or after CC attenuated subsequent CS-induced reinstatement, whereas AP-5 administered immediately following the first two reinstatement tests impaired the extinction of cocaine-seeking behavior. These results suggest that NMDA receptor-mediated mechanisms within the BLA play a crucial role in the consolidation of drug-CS associations into long-term memories that, in turn, drive cocaine-seeking during relapse. PMID:17613253

  11. NMDA receptor blockade in the basolateral amygdala disrupts consolidation of stimulus-reward memory and extinction learning during reinstatement of cocaine-seeking in an animal model of relapse

    PubMed Central

    Feltenstein, Matthew W.; See, Ronald E.

    2007-01-01

    Previous research from our laboratory has implicated the basolateral amygdala (BLA) complex in the acquisition and consolidation of cue-cocaine associations, as well as extinction learning, which may regulate the long-lasting control of conditioned stimuli (CS) over drug-seeking behavior. Given the well established role of NMDA glutamate receptor activation in other forms of amygdalar-based learning, we predicted that BLA-mediated drug-cue associative learning would be NMDA receptor dependent. To test this hypothesis, male Sprague-Dawley rats self-administered i.v. cocaine (0.6 mg/kg/infusion) in the absence of explicit CS pairings (2-h sessions, 5 days), followed by a single 1-h classical conditioning (CC) session, during which they received passive infusions of cocaine discretely paired with a light+tone stimulus complex. Following additional cocaine self-administration sessions in the absence of the CS (2-h sessions, 5 days) and extinction training sessions (no cocaine or CS presentation, 2-h sessions, 7 days), the ability of the CS to reinstate cocaine-seeking on three test days was assessed. Rats received bilateral intra-BLA infusions (0.5 μl/hemisphere) of vehicle or the selective NMDA receptor antagonist, 2-amino-5-phosphonovalerate (AP-5), immediately prior to the CC session (acquisition), immediately following the CC session (consolidation), or immediately following reinstatement testing (consolidation of conditioned-cued extinction learning). AP-5 administered before or after CC attenuated subsequent CS-induced reinstatement, whereas AP-5 administered immediately following the first two reinstatement tests impaired the extinction of cocaine-seeking behavior. These results suggest that NMDA receptor-mediated mechanisms within the BLA play a crucial role in the consolidation of drug-CS associations into long-term memories that, in turn, drive cocaine-seeking during relapse. PMID:17613253

  12. D-cycloserine facilitates extinction the first time but not the second time: an examination of the role of NMDA across the course of repeated extinction sessions.

    PubMed

    Langton, Julia M; Richardson, Rick

    2008-12-01

    Extinction of learned fear is facilitated by the partial NMDA agonist D-cycloserine (DCS). However, some studies suggest that the involvement of NMDA in learning differs depending on whether learning is for the first or second time. The current study aimed to extend these findings by examining the role of NMDA in extinction for the first and the second time. Specifically, the present series of experiments used Pavlovian fear conditioning and extinction paradigms to compare the effect of DCS on extinction of fear to a light CS the first and second time around. As found previously, DCS facilitated extinction of learned fear (Experiment 1). A novel finding, however, was that DCS did not facilitate the re-extinction of fear to this same CS following retraining (Experiments 2A and 2B). Finally, it was demonstrated that the transition from NMDA-dependent to NMDA-independent extinction was stimulus specific (Experiment 3). That is, rats were first trained to fear a CS (light); this fear was then extinguished. Following this, rats were then retrained to fear the same CS (light) or a new CS (white noise). When given a second extinction session, DCS was found to facilitate extinction of the new CS but not the original CS. The results of this series of experiments suggest that the role of NMDA in extinction depends on whether extinction is new learning (first extinction) or retrieval of a previous extinction memory (re-extinction). PMID:18354389

  13. Dissociation of extinction and behavioral disinhibition: the role of NMDA receptors in the pigeon associative forebrain during extinction.

    PubMed

    Lissek, Silke; Güntürkün, Onur

    2003-09-01

    Extinction is a unique learning process that requires the alteration of stimulus-response associations such that the organism ceases to respond to a previously rewarded stimulus. Extinction is mostly studied with fear conditioning and is impaired by lesions of the prefrontal cortex as well as by blockade of NMDA receptors in the amygdala. Because previous tasks could not clearly disambiguate extinction from behavioral disinhibition, the underlying process was difficult to define. In this study, we examined the possible role of NMDA receptors and the pigeon "prefrontal cortex," the neostriatum caudolaterale (NCL), for extinction of appetitive instrumental conditioning. We used a new design that discerns extinction from behavioral disinhibition. Our results demonstrate that NCL lesions cause deficits neither in extinction learning nor in extinction recall. However, blockade of NMDA receptors in the pigeon NCL by DL-AP-5 drastically impairs extinction learning without producing behavioral disinhibition or deficits in extinction recall. We suggest that NMDA receptors in the NCL contribute to the establishment of a learning process that selectively signals the change in value of the instrumental stimulus. Although NCL plays a key role for extinction learning, other structures can subsume similar functions after postlesional regeneration. PMID:12954874

  14. Deepened Extinction following Compound Stimulus Presentation: Noradrenergic Modulation

    ERIC Educational Resources Information Center

    Janak, Patricia H.; Corbit, Laura H.

    2011-01-01

    Behavioral extinction is an active form of new learning involving the prediction of nonreward where reward has previously been present. The expression of extinction learning can be disrupted by the presentation of reward itself or reward-predictive stimuli (reinstatement) as well as the passage of time (spontaneous recovery) or contextual changes…

  15. Effects of sleep on memory for conditioned fear and fear extinction

    PubMed Central

    Pace-Schott, Edward F.; Germain, Anne; Milad, Mohammed R.

    2015-01-01

    Learning and memory for extinction of conditioned fear is a basic mammalian mechanism for regulating negative emotion. Sleep promotes both the consolidation of memory and the regulation of emotion. Sleep can influence consolidation and modification of memories associated with both fear and its extinction. After brief overviews of the behavior and neural circuitry associated with fear conditioning, extinction learning and extinction memory in the rodent and human, interactions of sleep with these processes will be examined. Animal and human studies suggest that sleep can serve to consolidate both fear and extinction memory. In humans, sleep also promotes generalization of extinction memory. Time-of-day effects on extinction learning and generalization are also seen. REM may be a sleep stage of particular importance for the consolidation of both fear and extinction memory as evidenced by selective REM deprivation experiments. REM sleep is accompanied by selective activation of the same limbic structures implicated in the learning and memory of fear and extinction. Preliminary evidence also suggests extinction learning can take place during slow wave sleep. Study of low-level processes such as conditioning, extinction and habituation may allow sleep effects on emotional memory to be identified and inform study of sleep’s effects on more complex, emotionally salient declarative memories. Anxiety disorders are marked by impairments of both sleep and extinction memory. Improving sleep quality may ameliorate anxiety disorders by strengthening naturally acquired extinction. Strategically timed sleep may be used to enhance treatment of anxiety by strengthening therapeutic extinction learned via exposure therapy. PMID:25894546

  16. Is extinction forever?

    PubMed

    Smith-Patten, Brenda D; Bridge, Eli S; Crawford, Priscilla H C; Hough, Daniel J; Kelly, Jeffrey F; Patten, Michael A

    2015-05-01

    Mistrust of science has seeped into public perception of the most fundamental aspect of conservation-extinction. The term ought to be straightforward, and yet, there is a disconnect between scientific discussion and public views. This is not a mere semantic issue, rather one of communication. Within a population dynamics context, we say that a species went locally extinct, later to document its return. Conveying our findings matters, for when we use local extinction, an essentially nonsensical phrase, rather than extirpation, which is what is meant, then we contribute to, if not create outright, a problem for public understanding of conservation, particularly as local extinction is often shortened to extinction in media sources. The public that receives the message of our research void of context and modifiers comes away with the idea that extinction is not forever or, worse for conservation as a whole, that an extinction crisis has been invented. PMID:25711479

  17. Is extinction forever?

    PubMed Central

    Bridge, Eli S.; Crawford, Priscilla H. C.; Hough, Daniel J.; Kelly, Jeffrey F.; Patten, Michael A.

    2015-01-01

    Mistrust of science has seeped into public perception of the most fundamental aspect of conservation—extinction. The term ought to be straightforward, and yet, there is a disconnect between scientific discussion and public views. This is not a mere semantic issue, rather one of communication. Within a population dynamics context, we say that a species went locally extinct, later to document its return. Conveying our findings matters, for when we use local extinction, an essentially nonsensical phrase, rather than extirpation, which is what is meant, then we contribute to, if not create outright, a problem for public understanding of conservation, particularly as local extinction is often shortened to extinction in media sources. The public that receives the message of our research void of context and modifiers comes away with the idea that extinction is not forever or, worse for conservation as a whole, that an extinction crisis has been invented. PMID:25711479

  18. Biological selectivity of extinction

    NASA Astrophysics Data System (ADS)

    Kitchell, Jennifer A.

    Selective survival across major extinction event horizons is both a bothersome puzzle and an opportunity to delimit the biologically interesting question of causality. Heritable differences in characters may have predictable consequences in terms of differential species survival. Differences in magnitude and intensity of extinction are insufficient to distinguish background from mass extinction regimes. Biological adaptations may establish links of causality between abnormal times of mass extinction and normal times of background extinction. A current hypothesis, developed from a comparison of extinction patterns among Late Cretaceous molluscs, is that biological adaptations of organisms, effective during normal times of Earth history, are ineffectual during times of crises. A counter example is provided by data from high-latitude laminated marine strata that preserve evidence of an actively exploited life-history strategy among Late Cretaceous phytoplankton. These data illustrate a causal dependency between a biological character selected for during times of background extinction and macroevolutionary survivorship during an unusual time of crisis.

  19. The Infralimbic Cortex Regulates the Consolidation of Extinction after Cocaine Self-Administration

    ERIC Educational Resources Information Center

    LaLumiere, Ryan T.; Niehoff, Kate E.; Kalivas, Peter W.

    2010-01-01

    The infralimbic cortex (IL) regulates the consolidation of extinction learning for fear conditioning. Whether the IL influences the consolidation of extinction learning for cocaine self-administration is unknown. To address this issue, male Sprague-Dawley rats underwent 2 wk of cocaine self-administration followed by extinction training. On the…

  20. Estrous cycle phase and gonadal hormones influence conditioned fear extinction

    PubMed Central

    Milad, Mohammed R; Igoe, Sarah A; Lebron-Milad, Kelimer; Novales, Juan E

    2009-01-01

    Gonadal hormones modulate fear acquisition, but less is known about the influence of gonadal hormones on fear extinction. We assessed sex differences and the influence of gonadal hormone fluctuations and exogenous manipulations of estrogen and progesterone on acquisition, extinction learning and extinction recall in a 3-day auditory fear conditioning and extinction protocol. Experiments were conducted on males and naturally cycling female rats. Regarding female rats, significant differences in fear extinction were observed between subgroups of females, depending on their phase of the estrous cycle. Extinction that took place during the proestrus (high estrogen/progesterone) phase was more fully consolidated, as evidenced by low freezing during a recall test. This suggests that estrogen and/or progesterone facilitate extinction. In support of this, injection of both estrogen and progesterone prior to extinction learning in female rats during the metestrus phase of the cycle (low estrogen/progesterone) facilitated extinction consolidation, and blockade of estrogen and progesterone receptors during the proestrus phase impaired extinction consolidation. When comparing male to female rats without consideration of the estrous cycle phase, no significant sex differences were observed. When accounting for cycle phase in females, sex differences were observed only during extinction recall. Female rats that underwent extinction during the metestrus phase showed significantly higher freezing during the recall test relative to males. Collectively, these data suggest that gonadal hormones influence extinction behavior possibly by influencing the function of brain regions involved in the consolidation of fear extinction. Moreover, the elevated fear observed in female relative to male rats during extinction recall suggests that gonadal hormones may in part play a role in the higher prevalence of anxiety disorders in women. PMID:19761818

  1. Leaving School — learning at SEA: Regular high school education alongside polar research, not only during IPY

    NASA Astrophysics Data System (ADS)

    Gatti, S.

    2006-12-01

    Against the background of unsatisfactory results from the international OECD study PISA (Program for International Student Assessment), Germany is facing a period of intense school reforms. Looking back at a tradition of school culture with too few changes during the last century, quick and radical renewal of the school system is rather unlikely. Furthermore students are increasingly turning away from natural sciences. The AWI aims at providing impulses for major changes in the schooling system and is offering solid science education not only for university students but also for a much younger audience. All efforts towards this goal are interconnected within the project SEA (Science & Education @ the AWI). Fife years ago the AWI started HIGHSEA (High school of SEA). Each year 22 high school students (grade 11) are admitted to HIGHSEA spending their last three years of school not at school but at the institute. Four subjects (biology as a major, chemistry, math and English as accessory subjects) are combined and taught fully integrated. Students leave their schools for two days each week to study, work and explore all necessary topics at the AWI. All of the curricular necessities of the four subjects are being met. After rearrangement of the temporal sequencing conceptual formulation of four major questions around AWI-topics was possible. Students are taught by teachers of the cooperating schools as well as by scientists of the AWI. Close links and intense cooperation between all three groups are the basis of fundamental changes in teaching and learning climate. For each group of students we organize a short research expedition: in August 2005 we worked in the high Arctic, in January and February 2006 we performed measurements at two eastern Atlantic seamounts. Even if the amount of data coming from these expeditions is comparatively small they still contribute to ongoing research projects of the oceanographic department. The first two groups of students finished

  2. Dissociation of neuronal, electrodermal, and evaluative responses in disgust extinction.

    PubMed

    Klucken, Tim; Schweckendiek, Jan; Merz, Christian J; Vaitl, Dieter; Stark, Rudolf

    2013-06-01

    Disgust extinction is an important mechanism relevant for the treatment of psychiatric disorders. However, only a few studies have investigated disgust extinction. Moreover, because disgust sensitivity (DS) is considered as a relevant factor for learning processes, this study also investigated the potential relationship between DS and disgust extinction learning. The aim of this study was to explore the neuronal correlates of disgust extinction, as well as changes in skin conductance responses (SCRs) and evaluative conditioning. Twenty subjects were exposed to a differential extinction paradigm, in which a previous conditioned, and now unreinforced, stimulus (conditioned stimulus, CS+) was compared to a second stimulus (CS-), which was previously not associated with the unconditioned stimulus (UCS). Extinction learning was measured on three different response levels (BOLD responses, SCRs, and evaluative conditioning). Regarding evaluative conditioning, the CS+ was rated as more unpleasant than the CS-. Interestingly, significantly increased amygdala responses and SCRs toward to the CS- were observed. Finally, a (negative) trend was found between DS scores and BOLD responses of the prefrontal cortex. The present findings showed a dissociation of different response levels. The increased CS- responses could be explained by the assumption that the increased amygdala activity may reflect a safety learning signal during the first extinction trials and the subjective focus may therefore shift from the CS+ to the CS-. The correlation finding supports previous studies postulating that DS hampers extinction processes. The present results point toward dissociations between the response levels in context of extinction processes. PMID:23731074

  3. Secondary extinctions of biodiversity.

    PubMed

    Brodie, Jedediah F; Aslan, Clare E; Rogers, Haldre S; Redford, Kent H; Maron, John L; Bronstein, Judith L; Groves, Craig R

    2014-12-01

    Extinctions beget further extinctions when species lose obligate mutualists, predators, prey, or hosts. Here, we develop a conceptual model of species and community attributes affecting secondary extinction likelihood, incorporating mechanisms that buffer organisms against partner loss. Specialized interactors, including 'cryptic specialists' with diverse but nonredundant partner assemblages, incur elevated risk. Risk is also higher for species that cannot either evolve new traits following partner loss or obtain novel partners in communities reorganizing under changing environmental conditions. Partner loss occurs alongside other anthropogenic impacts; multiple stressors can circumvent ecological buffers, enhancing secondary extinction risk. Stressors can also offset each other, reducing secondary extinction risk, a hitherto unappreciated phenomenon. This synthesis suggests improved conservation planning tactics and critical directions for research on secondary extinctions. PMID:25445878

  4. Cannabinoid facilitation of fear extinction memory recall in humans.

    PubMed

    Rabinak, Christine A; Angstadt, Mike; Sripada, Chandra S; Abelson, James L; Liberzon, Israel; Milad, Mohammed R; Phan, K Luan

    2013-01-01

    A first-line approach to treat anxiety disorders is exposure-based therapy, which relies on extinction processes such as repeatedly exposing the patient to stimuli (conditioned stimuli; CS) associated with the traumatic, fear-related memory. However, a significant number of patients fail to maintain their gains, partly attributed to the fact that this inhibitory learning and its maintenance is temporary and conditioned fear responses can return. Animal studies have shown that activation of the cannabinoid system during extinction learning enhances fear extinction and its retention. Specifically, CB1 receptor agonists, such as Δ9-tetrahydrocannibinol (THC), can facilitate extinction recall by preventing recovery of extinguished fear in rats. However, this phenomenon has not been investigated in humans. We conducted a study using a randomized, double-blind, placebo-controlled, between-subjects design, coupling a standard Pavlovian fear extinction paradigm and simultaneous skin conductance response (SCR) recording with an acute pharmacological challenge with oral dronabinol (synthetic THC) or placebo (PBO) 2 h prior to extinction learning in 29 healthy adult volunteers (THC = 14; PBO = 15) and tested extinction retention 24 h after extinction learning. Compared to subjects that received PBO, subjects that received THC showed low SCR to a previously extinguished CS when extinction memory recall was tested 24 h after extinction learning, suggesting that THC prevented the recovery of fear. These results provide the first evidence that pharmacological enhancement of extinction learning is feasible in humans using cannabinoid system modulators, which may thus warrant further development and clinical testing. This article is part of a Special Issue entitled 'Cognitive Enhancers'. PMID:22796109

  5. Gradual extinction reduces reinstatement

    PubMed Central

    Shiban, Youssef; Wittmann, Jasmin; Weißinger, Mara; Mühlberger, Andreas

    2015-01-01

    The current study investigated whether gradually reducing the frequency of aversive stimuli during extinction can prevent the return of fear. Thirty-one participants of a three-stage procedure (acquisition, extinction and a reinstatement test on day 2) were randomly assigned to a standard extinction (SE) and gradual extinction (GE) procedure. The two groups differed only in the extinction procedure. While the SE group ran through a regular extinction process without any negative events, the frequency of the aversive stimuli during the extinction phase was gradually reduced for the GE group. The unconditioned stimulus (US) was an air blast (5 bar, 10 ms). A spider and a scorpion were used as conditioned stimuli (CS). The outcome variables were contingency ratings and physiological measures (skin conductance response, SCR and startle response). There were no differences found between the two groups for the acquisition and extinction phases concerning contingency ratings, SCR, or startle response. GE compared to SE significantly reduced the return of fear in the reinstatement test for the startle response but not for SCR or contingency ratings. This study was successful in translating the findings in rodent to humans. The results suggest that the GE process is suitable for increasing the efficacy of fear extinction. PMID:26441581

  6. Mass extinction: a commentary

    NASA Technical Reports Server (NTRS)

    Raup, D. M.

    1987-01-01

    Four neocatastrophist claims about mass extinction are currently being debated; they are that: 1, the late Cretaceous mass extinction was caused by large body impact; 2, as many as five other major extinctions were caused by impact; 3, the timing of extinction events since the Permian is uniformly periodic; and 4, the ages of impact craters on Earth are also periodic and in phase with the extinctions. Although strongly interconnected the four claims are independent in the sense that none depends on the others. Evidence for a link between impact and extinction is strong but still needs more confirmation through bed-by-bed and laboratory studies. An important area for future research is the question of whether extinction is a continuous process, with the rate increasing at times of mass extinctions, or whether it is episodic at all scales. If the latter is shown to be generally true, then species are at risk of extinction only rarely during their existence and catastrophism, in the sense of isolated events of extreme stress, is indicated. This is line of reasoning can only be considered an hypothesis for testing. In a larger context, paleontologists may benefit from a research strategy that looks to known Solar System and Galactic phenomena for predictions about environmental effects on earth. The recent success in the recognition of Milankovitch Cycles in the late Pleistocene record is an example of the potential of this research area.

  7. The fossil record of the sixth extinction.

    PubMed

    Plotnick, Roy E; Smith, Felisa A; Lyons, S Kathleen

    2016-05-01

    Comparing the magnitude of the current biodiversity crisis with those in the fossil record is difficult without an understanding of differential preservation. Integrating data from palaeontological databases with information on IUCN status, ecology and life history characteristics of contemporary mammals, we demonstrate that only a small and biased fraction of threatened species (< 9%) have a fossil record, compared with 20% of non-threatened species. We find strong taphonomic biases related to body size and geographic range. Modern species with a fossil record tend to be large and widespread and were described in the 19(th) century. The expected magnitude of the current extinction based only on species with a fossil record is about half of that of one based on all modern species; values for genera are similar. The record of ancient extinctions may be similarly biased, with many species having originated and gone extinct without leaving a tangible record. PMID:26932459

  8. Population Health and Paid Parental Leave: What the United States Can Learn from Two Decades of Research

    PubMed Central

    Burtle, Adam; Bezruchka, Stephen

    2016-01-01

    Over the last two decades, numerous studies have suggested that dedicated time for parents to be with their children in the earliest months of life offers significant benefits to child health. The United States (US) is the only wealthy nation without a formalized policy guaranteeing workers paid time off when they become new parents. As individual US states consider enacting parental leave policies, there is a significant opportunity to decrease health inequities and build a healthier American population. This document is intended as a critical review of the present evidence for the association between paid parental leave and population health. PMID:27417618

  9. A window of vulnerability: impaired fear extinction in adolescence.

    PubMed

    Baker, Kathryn D; Den, Miriam L; Graham, Bronwyn M; Richardson, Rick

    2014-09-01

    There have been significant advances made towards understanding the processes mediating extinction of learned fear. However, despite being of clear theoretical and clinical significance, very few studies have examined fear extinction in adolescence, which is often described as a developmental window of vulnerability to psychological disorders. This paper reviews the relatively small body of research examining fear extinction in adolescence. A prominent finding of this work is that adolescents, both humans and rodents, exhibit a marked impairment in extinction relative to both younger (e.g., juvenile) and older (e.g., adult) groups. We then review some potential mechanisms that could produce the striking extinction deficit observed in adolescence. For example, one neurobiological candidate mechanism for impaired extinction in adolescence involves changes in the functional connectivity within the fear extinction circuit, particularly between prefrontal cortical regions and the amygdala. In addition, we review research on emotion regulation and attention processes that suggests that developmental changes in attention bias to threatening cues may be a cognitive mechanism that mediates age-related differences in extinction learning. We also examine how a differential reaction to chronic stress in adolescence impacts upon extinction retention during adolescence as well as in later life. Finally, we consider the findings of several studies illustrating promising approaches that overcome the typically-observed extinction impairments in adolescent rodents and that could be translated to human adolescents. PMID:24513634

  10. Adrenergic Transmission Facilitates Extinction of Conditional Fear in Mice

    ERIC Educational Resources Information Center

    Barad, Mark; Cain, Christopher K.; Blouin, Ashley M.

    2004-01-01

    Extinction of classically conditioned fear, like its acquisition, is active learning, but little is known about its molecular mechanisms. We recently reported that temporal massing of conditional stimulus (CS) presentations improves extinction memory acquisition, and suggested that temporal spacing was less effective because individual CS…

  11. Extinction and the fossil record

    NASA Technical Reports Server (NTRS)

    Sepkoski, J. J. Jr; Sepkoski JJ, ,. J. r. (Principal Investigator)

    1994-01-01

    The author examines evidence of mass extinctions in the fossil record and searches for reasons for such large extinctions. Five major mass extinctions eliminated at least 40 percent of animal genera in the oceans and from 65 to 95 percent of ocean species. Questions include the occurrence of gradual or catastrophic extinctions, causes, environment, the capacity of a perturbation to cause extinctions each time it happens, and the possibility and identification of complex events leading to a mass extinction.

  12. Antiamnesic Effect of Broccoli (Brassica oleracea var. italica) Leaves on Amyloid Beta (Aβ)1-42-Induced Learning and Memory Impairment.

    PubMed

    Park, Seon Kyeong; Ha, Jeong Su; Kim, Jong Min; Kang, Jin Yong; Lee, Du Sang; Guo, Tian Jiao; Lee, Uk; Kim, Dae-Ok; Heo, Ho Jin

    2016-05-01

    To examine the antiamnesic effects of broccoli (Brassica oleracea var. italica) leaves, we performed in vitro and in vivo tests on amyloid beta (Aβ)-induced neurotoxicity. The chloroform fraction from broccoli leaves (CBL) showed a remarkable neuronal cell-protective effect and an inhibition against acetylcholinesterase (AChE). The ameliorating effect of CBL on Aβ1-42-induced learning and memory impairment was evaluated by Y-maze, passive avoidance, and Morris water maze tests. The results indicated improving cognitive function in the CBL group. After the behavioral tests, antioxidant effects were detected by superoxide dismutase (SOD), oxidized glutathione (GSH)/total GSH, and malondialdehyde (MDA) assays, and inhibition against AChE was also presented in the brain. Finally, oxo-dihydroxy-octadecenoic acid (oxo-DHODE) and trihydroxy-octadecenoic acid (THODE) as main compounds were identified by quadrupole time-of-flight ultraperformance liquid chromatography (Q-TOF UPLC-MS) analysis. Therefore, our studies suggest that CBL could be used as a natural resource for ameliorating Aβ1-42-induced learning and memory impairment. PMID:27079470

  13. Is extinction age dependent?

    USGS Publications Warehouse

    Doran, N.A.; Arnold, A.J.; Parker, W.C.; Huffer, F.W.

    2006-01-01

    Age-dependent extinction is an observation with important biological implications. Van Valen's Red Queen hypothesis triggered three decades of research testing its primary implication: that age is independent of extinction. In contrast to this, later studies with species-level data have indicated the possible presence of age dependence. Since the formulation of the Red Queen hypothesis, more powerful tests of survivorship models have been developed. This is the first report of the application of the Cox Proportional Hazards model to paleontological data. Planktonic foraminiferal morphospecies allow the taxonomic and precise stratigraphic resolution necessary for the Cox model. As a whole, planktonic foraminiferal morphospecies clearly show age-dependent extinction. In particular, the effect is attributable to the presence of shorter-ranged species (range < 4 myr) following extinction events. These shorter-ranged species also possess tests with unique morphological architecture. The morphological differences are probably epiphenomena of underlying developmental and heterochronic processes of shorter-ranged species that survived various extinction events. Extinction survivors carry developmental and morphological characteristics into postextinction recovery times, and this sets them apart from species populations established independently of extinction events. Copyright ?? 2006, SEPM (Society for Sedimentary Geology).

  14. [GABA-Receptors in Modulation of Fear Memory Extinction].

    PubMed

    Dubrovina, N I

    2016-01-01

    GABA is the major inhibitory neurotransmitter in the central nervous system determining the efficacy of neuronal interaction. GABA-receptors play a key role in different aspects of fear memory--acquisition and consolidation, retention, reconsolidation and extinction. Extinction is an important behavioural phenomenon which allows organism to adapt its behavior to a changing environment. Extinction of fear memory is a form of new inhibitory learning which interferes with expression of the initial acquired fear conditioning. Resistance to extinction is symptom of depression and posttraumatic stress disorder. The aim of the present review was to summarize own and literary data about GABAergic modulation of fear extinction and pharmacological correction of extinction impairment at influences on GABA(A)- and GABA(B)- receptors. PMID:27538279

  15. Extinction and Retrieval + Extinction of Conditioned Fear Differentially Activate Medial Prefrontal Cortex and Amygdala in Rats.

    PubMed

    Lee, Hongjoo J; Haberman, Rebecca P; Roquet, Rheall F; Monfils, Marie-H

    2015-01-01

    Pairing a previously neutral conditioned stimulus (CS; e.g., a tone) to an aversive unconditioned stimulus (US; e.g., a footshock) leads to associative learning such that the tone alone comes to elicit a conditioned response (e.g., freezing). We have previously shown that an extinction session that occurs within the reconsolidation window (termed retrieval + extinction) attenuates fear responding and prevents the return of fear in Pavlovian fear conditioning (Monfils et al., 2009). To date, the mechanisms that explain the different behavioral outcomes between standard extinction and retrieval + extinction remain poorly understood. Here we sought to examine the differential temporal engagement of specific neural systems by these two approaches using Arc catFISH (cellular compartment analysis of temporal activity using fluorescence in situ hybridization (FISH)). Our results demonstrate that extinction and retrieval + extinction lead to differential patterns of expression, suggesting that they engage different networks. These findings provide insight into the neural mechanisms that allow extinction during reconsolidation to prevent the return of fear in rodents. PMID:26834596

  16. Extinction and Retrieval + Extinction of Conditioned Fear Differentially Activate Medial Prefrontal Cortex and Amygdala in Rats

    PubMed Central

    Lee, Hongjoo J.; Haberman, Rebecca P.; Roquet, Rheall F.; Monfils, Marie-H.

    2016-01-01

    Pairing a previously neutral conditioned stimulus (CS; e.g., a tone) to an aversive unconditioned stimulus (US; e.g., a footshock) leads to associative learning such that the tone alone comes to elicit a conditioned response (e.g., freezing). We have previously shown that an extinction session that occurs within the reconsolidation window (termed retrieval + extinction) attenuates fear responding and prevents the return of fear in Pavlovian fear conditioning (Monfils et al., 2009). To date, the mechanisms that explain the different behavioral outcomes between standard extinction and retrieval + extinction remain poorly understood. Here we sought to examine the differential temporal engagement of specific neural systems by these two approaches using Arc catFISH (cellular compartment analysis of temporal activity using fluorescence in situ hybridization (FISH)). Our results demonstrate that extinction and retrieval + extinction lead to differential patterns of expression, suggesting that they engage different networks. These findings provide insight into the neural mechanisms that allow extinction during reconsolidation to prevent the return of fear in rodents. PMID:26834596

  17. Fear Extinction in Rodents

    PubMed Central

    Chang, Chun-hui; Knapska, Ewelina; Orsini, Caitlin A.; Rabinak, Christine A.; Zimmerman, Joshua M.; Maren, Stephen

    2009-01-01

    Pavlovian conditioning paradigms have become important model systems for understanding the neuroscience of behavior. In particular, studies of the extinction of Pavlovian fear responses are yielding important information about the neural substrates of anxiety disorders in humans. These studies are germane to understanding the neural mechanisms underlying behavioral interventions that suppress fear, including exposure therapy. This chapter described detailed behavioral protocols for examining the nature and properties of fear extinction in laboratory rodents. PMID:19340814

  18. Extinction of oscillating populations.

    PubMed

    Smith, Naftali R; Meerson, Baruch

    2016-03-01

    Established populations often exhibit oscillations in their sizes that, in the deterministic theory, correspond to a limit cycle in the space of population sizes. If a population is isolated, the intrinsic stochasticity of elemental processes can ultimately bring it to extinction. Here we study extinction of oscillating populations in a stochastic version of the Rosenzweig-MacArthur predator-prey model. To this end we develop a WKB (Wentzel, Kramers and Brillouin) approximation to the master equation, employing the characteristic population size as the large parameter. Similar WKB theories have been developed previously in the context of population extinction from an attracting multipopulation fixed point. We evaluate the extinction rates and find the most probable paths to extinction from the limit cycle by applying Floquet theory to the dynamics of an effective four-dimensional WKB Hamiltonian. We show that the entropic barriers to extinction change in a nonanalytic way as the system passes through the Hopf bifurcation. We also study the subleading pre-exponential factors of the WKB approximation. PMID:27078294

  19. Extinction of oscillating populations

    NASA Astrophysics Data System (ADS)

    Smith, Naftali R.; Meerson, Baruch

    2016-03-01

    Established populations often exhibit oscillations in their sizes that, in the deterministic theory, correspond to a limit cycle in the space of population sizes. If a population is isolated, the intrinsic stochasticity of elemental processes can ultimately bring it to extinction. Here we study extinction of oscillating populations in a stochastic version of the Rosenzweig-MacArthur predator-prey model. To this end we develop a WKB (Wentzel, Kramers and Brillouin) approximation to the master equation, employing the characteristic population size as the large parameter. Similar WKB theories have been developed previously in the context of population extinction from an attracting multipopulation fixed point. We evaluate the extinction rates and find the most probable paths to extinction from the limit cycle by applying Floquet theory to the dynamics of an effective four-dimensional WKB Hamiltonian. We show that the entropic barriers to extinction change in a nonanalytic way as the system passes through the Hopf bifurcation. We also study the subleading pre-exponential factors of the WKB approximation.

  20. Mass extinction causes debated

    NASA Astrophysics Data System (ADS)

    Katzoff, Judith A.

    A highly charged atmosphere and a tacit agreement to disagree marked the first Union session at the 1985 AGU Fall Meeting,“Where Are We Now on Iridium, Anomalies, Extinctions, Impacts, Volcanism, and Periodicity?” The session brought together a remarkably large and varied group of participants who are studying topics related to mass extinctions. “The important thing is bringing all these people together, sharing … how they think,” said J. John Sepkoski, Jr., of the University of Chicago, who presented one of the session's invited papers.The controversies under discussion included the nature of the catastrophic events that may have occurred 65 million years ago to precipitate mass extinctions between the Cretaceous and Tertiary periods and whether mass extinctions have occurred at regular intervals (and if so, what those intervals are). Both the group advocating extraterrestrial impacts and that advocating episodes of unusual terrestrial volcanism seemed to agree that both kinds of catastrophes would have brought on highly acidic precipitation that could have threatened many life forms. In fact, one paleontologist called for closer examination of patterns of survival during periods of mass extinctions in order to gain clues about the nature of the events that may have brought on the extinctions. “The survivors … set limits on what could have occurred,” said William A. Clemens of the University of California, Berkeley.

  1. Role of Medial Prefrontal Cortex Narp in the Extinction of Morphine Conditioned Place Preference

    ERIC Educational Resources Information Center

    Blouin, Ashley M.; Han, Sungho; Pearce, Anne M.; Cheng, KaiLun; Lee, JongAh J.; Johnson, Alexander W.; Wang, Chuansong; During, Matthew J.; Holland, Peter C.; Shaham, Yavin; Baraban, Jay M.; Reti, Irving M.

    2013-01-01

    Narp knockout (KO) mice demonstrate an impaired extinction of morphine conditioned place preference (CPP). Because the medial prefrontal cortex (mPFC) has been implicated in extinction learning, we tested whether Narp cells in this region play a role in the extinction of morphine CPP. We found that intracranial injections of adenoassociated virus…

  2. All about Endangered and Extinct Animals. Animal Life for Children. [Videotape].

    ERIC Educational Resources Information Center

    2000

    While there are thousands of different animals in the world, some have been extinct for many years and others are on the verge of extinction. In this videotape, students learn about the natural and man-made factors that lead to the endangerment and extinction of animals. Children find out why it is essential for people to help all forms of…

  3. The infralimbic cortex regulates the consolidation of extinction after cocaine self-administration

    PubMed Central

    LaLumiere, Ryan T.; Niehoff, Kate E.; Kalivas, Peter W.

    2010-01-01

    The infralimbic cortex (IL) regulates the consolidation of extinction learning for fear conditioning. Whether the IL influences the consolidation of extinction learning for cocaine self-administration is unknown. To address this issue, male Sprague–Dawley rats underwent 2 wk of cocaine self-administration followed by extinction training. On the first 5 d of extinction, rats underwent brief (15- or 30-min) extinction sessions and received intra-IL microinjections immediately after each extinction session. On days 6–12 of extinction, rats underwent full-length (2-h) extinction sessions that were used to assess the retention of the extinction learning from the short sessions. IL inactivation via microinjections of the GABA agonists baclofen and muscimol (BM) immediately after the extinction sessions (days 1–5) impaired the retention of extinction learning. Control experiments demonstrated that this effect was not due to inactivation of the prelimbic cortex or due to effects of the drugs on the subsequent day's behavior. In contrast, post-training intra-IL microinjections of the allosteric AMPA receptor potentiator 4-[2-(phenylsulfonylamino)ethylthio]-2,6-difluorophenoxyacetamide (PEPA) enhanced retention of the extinction learning. As evidence suggests a role for the β-adrenergic receptors in memory consolidation, other rats received microinjections of the β2-adrenergic receptor agonist clenbuterol or antagonist ICI-118,551 (ICI). Post-training intra-IL administration of clenbuterol or pre-training administration of ICI enhanced or impaired, respectively, the retention of extinction learning. These data indicate that the IL, and specifically the glutamatergic and β-adrenergic systems in the IL, regulates the consolidation of extinction of cocaine self-administration and that the IL can be manipulated to influence the retention of extinction. PMID:20332188

  4. Differential Regulation of Glutamic Acid Decarboxylase Gene Expression after Extinction of a Recent Memory vs. Intermediate Memory

    ERIC Educational Resources Information Center

    Sangha, Susan; Ilenseer, Jasmin; Sosulina, Ludmila; Lesting, Jorg; Pape, Hans-Christian

    2012-01-01

    Extinction reduces fear to stimuli that were once associated with an aversive event by no longer coupling the stimulus with the aversive event. Extinction learning is supported by a network comprising the amygdala, hippocampus, and prefrontal cortex. Previous studies implicate a critical role of GABA in extinction learning, specifically the GAD65…

  5. Candesartan ameliorates impaired fear extinction induced by innate immune activation.

    PubMed

    Quiñones, María M; Maldonado, Lizette; Velazquez, Bethzaly; Porter, James T

    2016-02-01

    Patients with post-traumatic stress disorder (PTSD) tend to show signs of a relatively increased inflammatory state suggesting that activation of the immune system may contribute to the development of PTSD. In the present study, we tested whether activation of the innate immune system can disrupt acquisition or recall of auditory fear extinction using an animal model of PTSD. Male adolescent rats received auditory fear conditioning in context A. The next day, an intraperitoneal injection of lipopolysaccharide (LPS; 100 μg/kg) prior to auditory fear extinction in context B impaired acquisition and recall of extinction. LPS (100 μg/kg) given after extinction training did not impair extinction recall suggesting that LPS did not affect consolidation of extinction. In contrast to cued fear extinction, contextual fear extinction was not affected by prior injection of LPS (100 μg/kg). Although LPS also reduced locomotion, we could dissociate the effects of LPS on extinction and locomotion by using a lower dose of LPS (50 μg/kg) which impaired locomotion without affecting extinction. In addition, 15 h after an injection of 250 μg/kg LPS in adult rats, extinction learning and recall were impaired without affecting locomotion. A sub-chronic treatment with candesartan, an angiotensin II type 1 receptor blocker, prevented the LPS-induced impairment of extinction in adult rats. Our results demonstrate that activation of the innate immune system can disrupt auditory fear extinction in adolescent and adult animals. These findings also provide direction for clinical studies of novel treatments that modulate the innate immune system for stress-related disorders like PTSD. PMID:26520214

  6. Leave It to Beaver. Merchants Millpond State Park: An Environmental Education Learning Experience Designed for Grades 4-6.

    ERIC Educational Resources Information Center

    Williams, Floyd K.

    This learning packet, one in a group of eight, was developed by the Merchants Millpond State Park in North Carolina to teach students in grades 4-6 about the habitat and lifestyle of the beaver. Loose-leaf pages are presented in nine sections that contain: (1) introductions to the North Carolina State Parks System, the Merchants Millpond State…

  7. Acute stress impairs the retrieval of extinction memory in humans

    PubMed Central

    Raio, Candace M.; Brignoni-Perez, Edith; Goldman, Rachel; Phelps, Elizabeth A.

    2014-01-01

    Extinction training is a form of inhibitory learning that allows an organism to associate a previously aversive cue with a new, safe outcome. Extinction does not erase a fear association, but instead creates a competing association that may or may not be retrieved when a cue is subsequently encountered. Characterizing the conditions under which extinction learning is expressed is important to enhancing the treatment of anxiety disorders that rely on extinction-based exposure therapy as a primary treatment technique. The ventromedial prefrontal cortex, which plays an important role in the expression of extinction memory, has been shown to be functionally impaired after stress exposure. Further, recent research in rodents found that exposure to stress led to deficits in extinction retrieval, although this has yet to be tested in humans. To explore how stress might influence extinction retrieval in humans, participants underwent a differential aversive learning paradigm, in which one image was probabilistically paired with an aversive shock while the other image denoted safety. Extinction training directly followed, at which point reinforcement was omitted. A day later, participants returned to the lab and either completed an acute stress manipulation (i.e., cold pressor), or a control task, before undergoing an extinction retrieval test. Skin conductance responses and salivary cortisol concentrations were measured throughout each session as indices of fear arousal and neuroendocrine stress responses, respectively. The efficacy of our stress induction was established by observing significant increases in cortisol for the stress condition only. We examined extinction retrieval by comparing conditioned responses during the last trial of extinction (day 1) with that of the first trial of re-extinction (day 2). Groups did not differ on initial fear acquisition or extinction, however, one day later participants in the stress group (n = 27) demonstrated significantly less

  8. Alterations in neuronal morphology in infralimbic cortex predict resistance to fear extinction following acute stress

    PubMed Central

    Moench, Kelly M.; Maroun, Mouna; Kavushansky, Alexandra; Wellman, Cara

    2015-01-01

    Dysfunction in corticolimbic circuits that mediate the extinction of learned fear responses is thought to underlie the perseveration of fear in stress-related psychopathologies, including post-traumatic stress disorder. Chronic stress produces dendritic hypertrophy in basolateral amygdala (BLA) and dendritic hypotrophy in medial prefrontal cortex, whereas acute stress leads to hypotrophy in both BLA and prelimbic cortex. Additionally, both chronic and acute stress impair extinction retrieval. Here, we examined the effects of a single elevated platform stress on extinction learning and dendritic morphology in infralimbic cortex, a region considered to be critical for extinction. Acute stress produced resistance to extinction, as well as dendritic retraction in infralimbic cortex. Spine density on apical and basilar terminal branches was unaffected by stress. However, animals that underwent conditioning and extinction had decreased spine density on apical terminal branches. Thus, whereas dendritic morphology in infralimbic cortex appears to be particularly sensitive to stress, changes in spines may more sensitively reflect learning. Further, in stressed rats that underwent conditioning and extinction, the level of extinction learning was correlated with spine densities, in that rats with poorer extinction retrieval had more immature spines and fewer thin spines than rats with better extinction retrieval, suggesting that stress may have impaired learning-related spine plasticity. These results may have implications for understanding the role of medial prefrontal cortex in learning deficits associated with stress-related pathologies. PMID:26844245

  9. Alterations in neuronal morphology in infralimbic cortex predict resistance to fear extinction following acute stress.

    PubMed

    Moench, Kelly M; Maroun, Mouna; Kavushansky, Alexandra; Wellman, Cara

    2016-06-01

    Dysfunction in corticolimbic circuits that mediate the extinction of learned fear responses is thought to underlie the perseveration of fear in stress-related psychopathologies, including post-traumatic stress disorder. Chronic stress produces dendritic hypertrophy in basolateral amygdala (BLA) and dendritic hypotrophy in medial prefrontal cortex, whereas acute stress leads to hypotrophy in both BLA and prelimbic cortex. Additionally, both chronic and acute stress impair extinction retrieval. Here, we examined the effects of a single elevated platform stress on extinction learning and dendritic morphology in infralimbic cortex, a region considered to be critical for extinction. Acute stress produced resistance to extinction, as well as dendritic retraction in infralimbic cortex. Spine density on apical and basilar terminal branches was unaffected by stress. However, animals that underwent conditioning and extinction had decreased spine density on apical terminal branches. Thus, whereas dendritic morphology in infralimbic cortex appears to be particularly sensitive to stress, changes in spines may more sensitively reflect learning. Further, in stressed rats that underwent conditioning and extinction, the level of extinction learning was correlated with spine densities, in that rats with poorer extinction retrieval had more immature spines and fewer thin spines than rats with better extinction retrieval, suggesting that stress may have impaired learning-related spine plasticity. These results may have implications for understanding the role of medial prefrontal cortex in learning deficits associated with stress-related pathologies. PMID:26844245

  10. Hybridization and extinction.

    PubMed

    Todesco, Marco; Pascual, Mariana A; Owens, Gregory L; Ostevik, Katherine L; Moyers, Brook T; Hübner, Sariel; Heredia, Sylvia M; Hahn, Min A; Caseys, Celine; Bock, Dan G; Rieseberg, Loren H

    2016-08-01

    Hybridization may drive rare taxa to extinction through genetic swamping, where the rare form is replaced by hybrids, or by demographic swamping, where population growth rates are reduced due to the wasteful production of maladaptive hybrids. Conversely, hybridization may rescue the viability of small, inbred populations. Understanding the factors that contribute to destructive versus constructive outcomes of hybridization is key to managing conservation concerns. Here, we survey the literature for studies of hybridization and extinction to identify the ecological, evolutionary, and genetic factors that critically affect extinction risk through hybridization. We find that while extinction risk is highly situation dependent, genetic swamping is much more frequent than demographic swamping. In addition, human involvement is associated with increased risk and high reproductive isolation with reduced risk. Although climate change is predicted to increase the risk of hybridization-induced extinction, we find little empirical support for this prediction. Similarly, theoretical and experimental studies imply that genetic rescue through hybridization may be equally or more probable than demographic swamping, but our literature survey failed to support this claim. We conclude that halting the introduction of hybridization-prone exotics and restoring mature and diverse habitats that are resistant to hybrid establishment should be management priorities. PMID:27468307

  11. The role of the medial prefrontal cortex in trace fear extinction.

    PubMed

    Kwapis, Janine L; Jarome, Timothy J; Helmstetter, Fred J

    2014-01-01

    The extinction of delay fear conditioning relies on a neural circuit that has received much attention and is relatively well defined. Whether this established circuit also supports the extinction of more complex associations, however, is unclear. Trace fear conditioning is a better model of complex relational learning, yet the circuit that supports extinction of this memory has received very little attention. Recent research has indicated that trace fear extinction requires a different neural circuit than delay extinction; trace extinction requires the participation of the retrosplenial cortex, but not the amygdala, as noted in a previous study. Here, we tested the roles of the prelimbic and infralimbic regions of the medial prefrontal cortex in trace and delay fear extinction by blocking NMDA receptors during extinction learning. We found that the prelimbic cortex is necessary for trace, but not for delay fear extinction, whereas the infralimbic cortex is involved in both types of extinction. These results are consistent with the idea that trace fear associations require plasticity in multiple cortical areas for successful extinction. Further, the infralimbic cortex appears to play a role in extinction regardless of whether the animal was initially trained in trace or delay conditioning. Together, our results provide new information about how the neural circuits supporting trace and delay fear extinction differ. PMID:25512576

  12. Effects of sleep on memory for conditioned fear and fear extinction.

    PubMed

    Pace-Schott, Edward F; Germain, Anne; Milad, Mohammed R

    2015-07-01

    Learning and memory for extinction of conditioned fear is a basic mammalian mechanism for regulating negative emotion. Sleep promotes both the consolidation of memory and the regulation of emotion. Sleep can influence consolidation and modification of memories associated with both fear and its extinction. After brief overviews of the behavior and neural circuitry associated with fear conditioning, extinction learning, and extinction memory in the rodent and human, interactions of sleep with these processes will be examined. Animal and human studies suggest that sleep can serve to consolidate both fear and extinction memory. In humans, sleep also promotes generalization of extinction memory. Time-of-day effects on extinction learning and generalization are also seen. Rapid eye movement (REM) may be a sleep stage of particular importance for the consolidation of both fear and extinction memory as evidenced by selective REM deprivation experiments. REM sleep is accompanied by selective activation of the same limbic structures implicated in the learning and memory of fear and extinction. Preliminary evidence also suggests extinction learning can take place during slow wave sleep. Study of low-level processes such as conditioning, extinction, and habituation may allow sleep effects on emotional memory to be identified and inform study of sleep's effects on more complex, emotionally salient declarative memories. Anxiety disorders are marked by impairments of both sleep and extinction memory. Improving sleep quality may ameliorate anxiety disorders by strengthening naturally acquired extinction. Strategically timed sleep may be used to enhance treatment of anxiety by strengthening therapeutic extinction learned via exposure therapy. (PsycINFO Database Record PMID:25894546

  13. Cortisol disrupts the neural correlates of extinction recall.

    PubMed

    Kinner, Valerie L; Merz, Christian J; Lissek, Silke; Wolf, Oliver T

    2016-06-01

    The renewal effect describes the recovery of extinguished responses that may occur after a change in context and indicates that extinction memory retrieval is sometimes prone to failure. Stress hormones have been implicated to modulate extinction processes, with mostly impairing effects on extinction retrieval. However, the neurobiological mechanisms mediating stress effects on extinction memory remain elusive. In this functional magnetic resonance imaging study, we investigated the effects of cortisol administration on the neural correlates of extinction memory retrieval in a predictive learning task. In this task, participants were required to predict whether certain food stimuli were associated with stomach trouble when presented in two different contexts. A two-day renewal paradigm was applied in which an association was acquired in context A and subsequently extinguished in context B. On the following day, participants received either cortisol or placebo 40min before extinction memory retrieval was tested in both contexts. Behaviorally, cortisol impaired the retrieval of extinguished associations when presented in the extinction context. On the neural level, this effect was characterized by a reduced context differentiation for the extinguished stimulus in the ventromedial prefrontal cortex, but only in men. In the placebo group, ventromedial prefrontal cortex was functionally connected to the left cerebellum, the anterior cingulate and the right anterior parahippocampal gyrus to express extinction memory. This functional crosstalk was reduced under cortisol. These findings illustrate that the stress hormone cortisol disrupts ventromedial prefrontal cortex functioning and its communication with other brain regions implicated in extinction memory. PMID:26973167

  14. Biological Extinction in Earth History

    NASA Astrophysics Data System (ADS)

    Raup, David M.

    1986-03-01

    Virtually all plant and animal species that have ever lived on the earth are extinct. For this reason alone, extinction must play an important role in the evolution of life. The five largest mass extinctions of the past 600 million years are of greatest interest, but there is also a spectrum of smaller events, many of which indicate biological systems in profound stress. Extinction may be episodic at all scales, with relatively long periods of stability alternating with short-lived extinction events. Most extinction episodes are biologically selective, and further analysis of the victims and survivors offers the greatest chance of deducing the proximal causes of extinction. A drop in sea level and climatic change are most frequently invoked to explain mass extinctions, but new theories of collisions with extraterrestrial bodies are gaining favor. Extinction may be constructive in a Darwinian sense or it may only perturb the system by eliminating those organisms that happen to be susceptible to geologically rare stresses.

  15. Biological extinction in earth history

    NASA Technical Reports Server (NTRS)

    Raup, D. M.

    1986-01-01

    Virtually all plant and animal species that have ever lived on the earth are extinct. For this reason alone, extinction must play an important role in the evolution of life. The five largest mass extinctions of the past 600 million years are of greatest interest, but there is also a spectrum of smaller events, many of which indicate biological systems in profound stress. Extinction may be episodic at all scales, with relatively long periods of stability alternating with short-lived extinction events. Most extinction episodes are biologically selective, and further analysis of the victims and survivors offers the greatest chance of deducing the proximal causes of extinction. A drop in sea level and climatic change are most frequently invoked to explain mass extinctions, but new theories of collisions with extraterrestrial bodies are gaining favor. Extinction may be constructive in a Darwinian sense or it may only perturb the system by eliminating those organisms that happen to be susceptible to geologically rare stresses.

  16. Species extinction mires ecosystem

    SciTech Connect

    Holzman, D.

    1990-03-26

    Extinction is normal in the evolution of life, but amphibians, insects, birds and mammals are vanishing at an alarming pace. While habitat destruction, overexploitation and pollution are among the main causes, some disappearances cannot be explained. The extinction problem among amphibians mirrors the general, worldwide phenomenon. A synergism of insults may be responsible. Chance events such as a dry year might occasionally clean out a pond. But a larger lake nearby would replenish it. Now acid pollution adds to the ponds' burden while stocking of amphibian-eating sport fish in the lake - which happens even in natural parks - would destroy the source of replenishment. Some fear that extinctions ultimately could destroy nature's fabric.

  17. Supernovae and mass extinctions

    NASA Technical Reports Server (NTRS)

    Vandenbergh, S.

    1994-01-01

    Shklovsky and others have suggested that some of the major extinctions in the geological record might have been triggered by explosions of nearby supernovae. The frequency of such extinction events will depend on the galactic supernova frequency and on the distance up to which a supernova explosion will produce lethal effects upon terrestrial life. In the present note it will be assumed that a killer supernova has to occur so close to Earth that it will be embedded in a young, active, supernova remnant. Such young remnants typically have radii approximately less than 3 pc (1 x 10(exp 19) cm). Larger (more pessimistic?) killer radii have been adopted by Ruderman, Romig, and by Ellis and Schramm. From observations of historical supernovae, van den Bergh finds that core-collapse (types Ib and II) supernovae occur within 4 kpc of the Sun at a rate of 0.2 plus or minus 0.1 per century. Adopting a layer thickness of 0.3 kpc for the galacitc disk, this corresponds to a rate of approximately 1.3 x 10(exp -4) supernovae pc(exp -3) g.y.(exp -1). Including supernovae of type Ia will increase the total supernovae rate to approximately 1.5 x 10(exp -4) supernovae pc(exp -3) g.y.(exp -1). For a lethal radius of R pc the rate of killer events will therefore be 1.7 (R/3)(exp 3) x 10(exp -2) supernovae per g.y. However, a frequency of a few extinctions per g.y. is required to account for the extinctions observed during the phanerozoic. With R (extinction) approximately 3 pc, the galactic supernova frequency is therefore too low by 2 orders of magnitude to account for the major extinctions in the geological record.

  18. Extinction and Renewal of Conditioned Sexual Responses

    PubMed Central

    Brom, Mirte; Laan, Ellen; Everaerd, Walter; Spinhoven, Philip; Both, Stephanie

    2014-01-01

    Introduction Extinction involves an inhibitory form of new learning that is highly dependent on the context for expression. This is supported by phenomena such as renewal and spontaneous recovery, which may help explain the persistence of appetitive behavior, and related problems such as addictions. Research on these phenomena in the sexual domain is lacking, where it may help to explain the persistence of learned sexual responses. Method Men (n = 40) and women (n = 62) participated in a differential conditioning paradigm, with genital vibrotactile stimulation as US and neutral pictures as conditional stimuli (CSs). Dependent variables were genital and subjective sexual arousal, affect, US expectancy, and approach and avoid tendencies towards the CSs. Extinction and renewal of conditioned sexual responses were studied by context manipulation (AAA vs. ABA condition). Results No renewal effect of genital conditioned responding could be detected, but an obvious recovery of US expectancy following a context change after extinction (ABA) was demonstrated. Additionally, women demonstrated recovery of subjective affect and subjective sexual arousal. Participants in the ABA demonstrated more approach biases towards stimuli. Conclusions The findings support the context dependency of extinction and renewal of conditioned sexual responses in humans. This knowledge may have implications for the treatment of disturbances in sexual appetitive responses such as hypo- and hypersexuality. PMID:25170909

  19. A current overview of cannabinoids and glucocorticoids in facilitating extinction of aversive memories: potential extinction enhancers.

    PubMed

    de Bitencourt, Rafael Mariano; Pamplona, Fabrício Alano; Takahashi, Reinaldo Naoto

    2013-01-01

    Emotional learning is extremely important for the survival of an individual. However, once acquired, emotional associations are not always expressed. The regulation of emotional responses under different environmental conditions is essential for mental health. Indeed, pathologic feelings of fear and anxiety are defining features of many serious psychiatric illness, including post-traumatic stress disorder (PTSD) and specific phobias. The simplest form of regulation of emotional responses is extinction, in which the conditioned response to a stimulus decreases when reinforcement (stimulus) is omitted. In addition to modulating basal anxiety states, recent studies suggest an important role for the endocannabinoid (eCB) and glucocorticoid systems in the modulation of emotional states and extinction of aversive memories in animals. The purpose of this review is to briefly outline the animal models of fear extinction and to describe how these have been used to examine the potential of extinction enhancing agents which specifically alter the eCB and glucocorticoid systems. Pharmacological manipulations of these systems by agents such as cannabinoid or glucocorticoid agonists can enhance the extinction process and avoid the retention of memories which have the potential to trigger trauma. A better understanding of these findings through animal models highlights the possibilities of using combined extinction enhancing agents in exposure-based psychotherapies for anxiety disorders related to inappropriate retention of aversive memories. This article is part of a special issue entitled 'Cognitive Enhancers'. PMID:22687521

  20. Extinction from a paleontological perspective

    NASA Technical Reports Server (NTRS)

    Raup, D. M.

    1993-01-01

    Extinction of widespread species is common in evolutionary time (millions of years) but rare in ecological time (hundreds or thousands of years). In the fossil record, there appears to be a smooth continuum between background and mass extinction; and the clustering of extinctions at mass extinctions cannot be explained by the chance coincidence of independent events. Although some extinction is selective, much is apparently random in that survivors have no recognizable superiority over victims. Extinction certainly plays an important role in evolution, but whether it is constructive or destructive has not yet been determined.

  1. Extinction from a paleontological perspective.

    PubMed

    Raup, D M

    1993-01-01

    Extinction of widespread species is common in evolutionary time (millions of years) but rare in ecological time (hundreds or thousands of years). In the fossil record, there appears to be a smooth continuum between background and mass extinction; and the clustering of extinctions at mass extinctions cannot be explained by the chance coincidence of independent events. Although some extinction is selective, much is apparently random in that survivors have no recognizable superiority over victims. Extinction certainly plays an important role in evolution, but whether it is constructive or destructive has not yet been determined. PMID:11539838

  2. Out with the old and in with the new: Synaptic mechanisms of extinction in the amygdala.

    PubMed

    Maren, Stephen

    2015-09-24

    Considerable research indicates that long-term synaptic plasticity in the amygdala underlies the acquisition of emotional memories, including those learned during Pavlovian fear conditioning. Much less is known about the synaptic mechanisms involved in other forms of associative learning, including extinction, that update fear memories. Extinction learning might reverse conditioning-related changes (e.g., depotentiation) or induce plasticity at inhibitory synapses (e.g., long-term potentiation) to suppress conditioned fear responses. Either mechanism must account for fear recovery phenomena after extinction, as well as savings of extinction after fear recovery. This article is part of a Special Issue entitled SI: Brain and Memory. PMID:25312830

  3. Mechanisms governing the reactivation-dependent destabilization of memories and their role in extinction

    PubMed Central

    Flavell, Charlotte R.; Lambert, Elliot A.; Winters, Boyer D.; Bredy, Timothy W.

    2013-01-01

    The extinction of learned associations has traditionally been considered to involve new learning, which competes with the original memory for control over behavior. However, a recent resurgence of interest in reactivation-dependent amnesia has revealed that the retrieval of fear-related memory (with what is essentially a brief extinction session) can result in its destabilization. This review discusses some of the cellular and molecular mechanisms that are involved in the destabilization of a memory following its reactivation and/or extinction, and investigates the evidence that extinction may involve both new learning as well as a partial destabilization-induced erasure of the original memory trace. PMID:24421762

  4. Unexpectedly many extinct hominins.

    PubMed

    Bokma, Folmer; van den Brink, Valentijn; Stadler, Tanja

    2012-09-01

    Recent studies indicate that Neanderthal and Denisova hominins may have been separate species, while debate continues on the status of Homo floresiensis. The decade-long debate between "splitters," who recognize over 20 hominin species, and "lumpers," who maintain that all these fossils belong to just a few lineages, illustrates that we do not know how many extinct hominin species to expect. Here, we present probability distributions for the number of speciation events and the number of contemporary species along a branch of a phylogeny. With estimates of hominin speciation and extincton rates, we then show that the expected total number of extinct hominin species is 8, but may be as high as 27. We also show that it is highly unlikely that three very recent species disappeared due to natural, background extinction. This may indicate that human-like remains are too easily considered distinct species. Otherwise, the evidence suggesting that Neanderthal and the Denisova hominin represent distinct species implies a recent wave of extinctions, ostensibly driven by the only survivor, H. sapiens. PMID:22946817

  5. Extinction Curves of Lensing Galaxies

    NASA Astrophysics Data System (ADS)

    Elíasdóttir, Árdís

    2006-09-01

    Dust extinction causes light from distant sources to be dimmed on itsway to the observer. In cosmological studies, such as SN Ia studies,it is of great importance that the effects of dust extinction becorrectly accounted for. However, although dust properties, andhence extinction, are expected to vary with redshift, not very muchis known about the extinction properties of high redshift galaxies.This is because the methods traditionally used to study extinctioncurves are only applicable for the most nearby galaxies. Studyinggravitationally lensed quasars is an emerging method of studying thedust extinction of high redshift galaxies. I will present an ESO VLTstudy of 10 such lensing galaxies, with redshifts up to 1. The 10systems display varying amount and type of extinction, with thedoubly imaged quasar B1152+199 showing the greatest extinction with A(V)=2.4 and R_V=2.1 for a Galactic type extinction law.

  6. Differential Endocannabinoid Regulation of Extinction in Appetitive and Aversive Barnes Maze Tasks

    ERIC Educational Resources Information Center

    Harloe, John P.; Thorpe, Andrew J.; Lichtman, Aron H.

    2008-01-01

    CB[subscript 1] receptor-compromised animals show profound deficits in extinguishing learned behavior from aversive conditioning tasks, but display normal extinction learning in appetitive operant tasks. However, it is difficult to discern whether the differential involvement of the endogenous cannabinoid system on extinction results from the…

  7. Inactivation of the Infralimbic but Not the Prelimbic Cortex Impairs Consolidation and Retrieval of Fear Extinction

    ERIC Educational Resources Information Center

    Laurent, Vincent; Westbrook, R. Frederick

    2009-01-01

    Rats were subjected to one or two cycles of context fear conditioning and extinction to study the roles of the prelimbic cortex (PL) and infralimbic cortex (IL) in learning and relearning to inhibit fear responses. Inactivation of the PL depressed fear responses across the first or second extinction but did not impair learning or relearning fear…

  8. Calcineurin inhibition blocks within-, but not between-session fear extinction in mice

    PubMed Central

    Moulin, Thiago C.; Carneiro, Clarissa F. D.; Gonçalves, Marina M. C.; Junqueira, Lara S.; Amaral, Olavo B.

    2015-01-01

    Memory extinction involves the formation of a new associative memory that inhibits a previously conditioned association. Nonetheless, it could also depend on weakening of the original memory trace if extinction is assumed to have multiple components. The phosphatase calcineurin (CaN) has been described as being involved in extinction but not in the initial consolidation of fear learning. With this in mind, we set to study whether CaN could have different roles in distinct components of extinction. Systemic treatment with the CaN inhibitors cyclosporin A (CsA) or FK-506, as well as i.c.v. administration of CsA, blocked within-session, but not between-session extinction or initial learning of contextual fear conditioning. Similar effects were found in multiple-session extinction of contextual fear conditioning and in auditory fear conditioning, indicating that CaN is involved in different types of short-term extinction. Meanwhile, inhibition of protein synthesis by cycloheximide (CHX) treatment did not affect within-session extinction, but disrupted fear acquisition and slightly impaired between-session extinction. Our results point to a dissociation of within- and between-session extinction of fear conditioning, with the former being more dependent on CaN activity and the latter on protein synthesis. Moreover, the modulation of within-session extinction did not affect between-session extinction, suggesting that these components are at least partially independent. PMID:25691516

  9. Dissociable Roles for the Ventromedial Prefrontal Cortex and Amygdala in Fear Extinction: NR2B Contribution

    PubMed Central

    Diaz-Mataix, Llorenç; Bush, David E.A.; LeDoux, Joseph E.

    2009-01-01

    Fear extinction, which involves learning to suppress the expression of previously learned fear, requires N-methyl-D-aspartate receptors (NMDARs) and is mediated by the amygdala and ventromedial prefrontal cortex (vmPFC). Like other types of learning, extinction involves acquisition and consolidation phases. We recently demonstrated that NR2B-containing NMDARs (NR2Bs) in the lateral amygdala (LA) are required for extinction acquisition, but whether they are involved in consolidation is not known. Further, although it has been shown that NMDARs in the vmPFC are required for extinction consolidation, whether NR2Bs in vmPFC are involved in consolidation is not known. In this report, we investigated the possible role of LA and vmPFC NR2Bs in the consolidation of fear extinction using the NR2B-selective antagonist ifenprodil. We show that systemic treatment with ifenprodil immediately after extinction training disrupts extinction consolidation. Ifenprodil infusion into vmPFC, but not the LA, immediately after extinction training also disrupts extinction consolidation. In contrast, we also show pre-extinction training infusions into vmPFC has no effect. These results, together with our previous findings showing that LA NR2Bs are required during the acquisition phase in extinction, indicate a double dissociation for the phase-dependent role of NR2Bs in the LA (acquisition, not consolidation) and vmPFC (consolidation, not acquisition). PMID:18562331

  10. The influence of gonadal hormones on conditioned fear extinction in healthy humans.

    PubMed

    Milad, M R; Zeidan, M A; Contero, A; Pitman, R K; Klibanski, A; Rauch, S L; Goldstein, J M

    2010-07-14

    Recent rodent studies suggest that gonadal hormones influence extinction of conditioned fear. Here we investigated sex differences in, and the influence of estradiol and progesterone on, fear extinction in healthy humans. Men and women underwent a two-day paradigm in which fear conditioning and extinction learning took place on day 1 and extinction recall was tested on day 2. Visual cues were used as the conditioned stimuli and a mild electric shock was used as the unconditioned stimulus. Skin conductance was recorded throughout the experiment and used to measure conditioned responses (CRs). Blood samples were obtained from all women to measure estradiol and progesterone levels. We found that higher estradiol during extinction learning enhanced subsequent extinction recall but had no effects on fear acquisition or extinction learning itself. Sex differences were only observed during acquisition, with men exhibiting significantly higher CRs. After dividing women into low- and high-estradiol groups, men showed comparable extinction recall to high-estradiol women, and both of these groups showed higher extinction recall than low-estradiol women. Therefore, sex differences in extinction memory emerged only after taking into account women's estradiol levels. Lower estradiol may impair extinction consolidation in women. These findings could have practical applications in the treatment of anxiety disorders through cognitive and behavioral therapies. PMID:20412837

  11. The influence of gonadal hormones on conditioned fear extinction in healthy humans

    PubMed Central

    Milad, Mohammed R; Zeidan, Mohamed A.; Contero, Angelica; Pitman, Roger K.; Klibanski, Anne; Rauch, Scott L.; Goldstein, Jill M.

    2010-01-01

    Recent rodent studies suggest that gonadal hormones influence extinction of conditioned fear. Here we investigated sex differences in, and the influence of estradiol and progesterone on, fear extinction in healthy humans. Men and women underwent a two-day paradigm in which fear conditioning and extinction learning took place on day 1 and extinction recall was tested on day 2. Visual cues were used as the conditioned stimuli and a mild electric shock was used as the unconditioned stimulus. Skin conductance was recorded throughout the experiment and used to measure conditioned responses (CRs). Blood samples were obtained from all women to measure estradiol and progesterone levels. We found that higher estradiol during extinction learning enhanced subsequent extinction recall but had no effects on fear acquisition or extinction learning itself. Sex differences were only observed during acquisition, with men exhibiting significantly higher CRs. After dividing women into low- and high-estradiol groups, men showed comparable extinction recall to high-estradiol women, and both of these groups showed higher extinction recall than low-estradiol women. Therefore, sex differences in extinction memory emerged only after taking into account women's estradiol levels. Lower estradiol may impair extinction consolidation in women. These findings could have practical applications in the treatment of anxiety disorders through cognitive and behavioral therapies. PMID:20412837

  12. Mass Extinctions Past and Present.

    ERIC Educational Resources Information Center

    Allmon, Warren Douglas

    1987-01-01

    Discusses some parallels that seem to exist between mass extinction recognizable in the geologic record and the impending extinction of a significant proportion of the earth's species due largely to tropical deforestation. Describes some recent theories of causal factors and periodicities in mass extinction. (Author/TW)

  13. Extinction and spontaneous recovery of spatial behavior in pigeons.

    PubMed

    Leising, Kenneth J; Wong, Jared; Blaisdell, Aaron P

    2015-10-01

    We investigated extinction and spontaneous recovery of spatial associations using a landmark-based appetitive search task in a touchscreen preparation with pigeons. Four visual landmarks (A, B, C, and D) were separately established as signals of a hidden reinforced target among an 8 × 7 array of potential target locations. The target was located above landmarks (LM) A and C and below B and D. After conditioning, A and B were extinguished. Responding to A and C was assessed on probe tests 2 days following extinction, whereas, B and D were tested 14 days after extinction. We observed spontaneous recovery from spatial extinction following a 14-day, but not a 2-day, postextinction retention interval. Furthermore, by plotting the spatial distribution of responding across the X and Y axes during testing, we found that spontaneous recovery of responding to the target in our task was due to enhanced spatial control (i.e., a change in the overall distribution of responses) following the long delay to testing. These results add spatial extinction and spontaneous recovery to the list of findings supporting the assertion that extinction involves new learning that attenuates the originally acquired response, and that original learning of the spatial relationship between paired events survives extinction. (PsycINFO Database Record PMID:26437383

  14. Habituation and extinction of fear recruit overlapping forebrain structures.

    PubMed

    Furlong, Teri M; Richardson, Rick; McNally, Gavan P

    2016-02-01

    Establishing the neurocircuitry involved in inhibiting fear is important for understanding and treating anxiety disorders. To date, extinction procedures have been predominately used to examine the inhibition of learned fear, where fear is reduced to a conditioned stimulus (CS) by presenting it in the absence of the unconditioned stimulus (US). However, learned fear can also be reduced by habituation procedures where the US is presented in the absence of the CS. Here we used expression of the activity marker c-Fos in rats to compare the recruitment of several forebrain structures following fear habituation and extinction. Following fear conditioning where a tone CS was paired with a loud noise US, fear was then reduced the following day by either presentation of the CS or US alone (i.e. CS extinction or US habituation, respectively). This extinction and habituation training recruited several common structures, including infralimbic cortex, basolateral amygdala, midline thalamus and medial hypothalamus (orexin neurons). Moreover, this overlap was shared when examining the neural correlates of the expression of habituation and extinction, with common recruitment of infralimbic cortex and midline thalamus. However, there were also important differences. Specifically, acquisition of habituation was associated with greater recruitment of prelimbic cortex whereas expression of habituation was associated with greater recruitment of paraventricular thalamus. There was also less recruitment of central amygdala for habituation compared to extinction in the retention phase. These findings indicate that largely overlapping neurocircuitries underlie habituation and fear extinction and imply common mechanisms for reducing fear across different inhibitory treatments. PMID:26690954

  15. Renewal after the extinction of free operant behavior.

    PubMed

    Bouton, Mark E; Todd, Travis P; Vurbic, Drina; Winterbauer, Neil E

    2011-03-01

    Four experiments were performed to explore the role of context in operant extinction. In all experiments, leverpressing in rats was first reinforced with food pellets on a variable interval 30-s schedule, then extinguished, and finally tested in the same and a different physical context. The experiments demonstrated a clear ABA renewal effect, a recovery of extinguished responding when conditioning, extinction, and testing occurred in contexts A, B, and A, respectively. They also demonstrated ABC renewal (where conditioning extinction and testing occurred in contexts A, B, and C) and, for the first time in operant conditioning, AAB renewal (where conditioning, extinction, and testing occurred in contexts A, A, and B). The latter two phenomena indicate that tests outside the extinction context are sufficient to cause a recovery of extinguished operant behavior and, thus, that operant extinction, like Pavlovian extinction, is relatively specific to the context in which it is learned. AAB renewal was not weakened by tripling the amount of extinction training. ABA renewal was stronger than AAB, but not merely because of context A's direct association with the reinforcer. PMID:21279496

  16. Discreteness induced extinction

    NASA Astrophysics Data System (ADS)

    dos Santos, Renato Vieira; da Silva, Linaena Méricy

    2015-11-01

    Two simple models based on ecological problems are discussed from the point of view of non-equilibrium statistical mechanics. It is shown how discrepant may be the results of the models that include spatial distribution with discrete interactions when compared with the continuous analogous models. In the continuous case we have, under certain circumstances, the population explosion. When we take into account the finiteness of the population, we get the opposite result, extinction. We will analyze how these results depend on the dimension d of the space and describe the phenomenon of the "Discreteness Inducing Extinction" (DIE). The results are interpreted in the context of the "paradox of sex", an old problem of evolutionary biology.

  17. 2-arachidonoylglycerol signaling impairs short-term fear extinction

    PubMed Central

    Hartley, N D; Gunduz-Cinar, O; Halladay, L; Bukalo, O; Holmes, A; Patel, S

    2016-01-01

    Impairments in fear extinction are thought to be central to the psychopathology of posttraumatic stress disorder, and endocannabinoid (eCB) signaling has been strongly implicated in extinction learning. Here we utilized the monoacylglycerol lipase inhibitor JZL184 to selectively augment brain 2-AG levels combined with an auditory cue fear-conditioning paradigm to test the hypothesis that 2-AG-mediated eCB signaling modulates short-term fear extinction learning in mice. We show that systemic JZL184 impairs short-term extinction learning in a CB1 receptor-dependent manner without affecting non-specific freezing behavior or the acquisition of conditioned fear. This effect was also observed in over-conditioned mice environmentally manipulated to re-acquire fear extinction. Cumulatively, the effects of JZL184 appear to be partly due to augmentation of 2-AG signaling in the basolateral nucleus of the amygdala (BLA), as direct microinfusion of JZL184 into the BLA produced similar results. Moreover, we elucidate a short ~3-day temporal window during which 2-AG augmentation impairs extinction behavior, suggesting a preferential role for 2-AG-mediated eCB signaling in the modulation of short-term behavioral sequelae to acute traumatic stress exposure. PMID:26926885

  18. Yohimbine Impairs Extinction of Cocaine-Conditioned Place Preference in an [alpha] [subscript 2]-Adrenergic Receptor Independent Process

    ERIC Educational Resources Information Center

    Davis, Adeola R.; Shields, Angela D.; Brigman, Jonathan L.; Norcross, Maxine; McElligott, Zoe A.; Holmes, Andrew; Winder, Danny G.

    2008-01-01

    Extinction, a form of learning that has the ability to reshape learned behavior based on new experiences, has been heavily studied utilizing fear learning paradigms. Mechanisms underlying extinction of positive-valence associations, such as drug self-administration and place preference, are poorly understood yet may have important relevance to…

  19. Histone Modifications around Individual BDNF Gene Promoters in Prefrontal Cortex Are Associated with Extinction of Conditioned Fear

    ERIC Educational Resources Information Center

    Bredy, Timothy W.; Wu, Hao; Crego, Cortney; Zellhoefer, Jessica; Sun, Yi E.; Barad, Mark

    2007-01-01

    Extinction of conditioned fear is an important model both of inhibitory learning and of behavior therapy for human anxiety disorders. Like other forms of learning, extinction learning is long-lasting and depends on regulated gene expression. Epigenetic mechanisms make an important contribution to persistent changes in gene expression; therefore,…

  20. Contextual-Specificity of Short-Delay Extinction in Humans: Renewal of Fear-Potentiated Startle in a Virtual Environment

    ERIC Educational Resources Information Center

    Alvarez, Ruben P.; Johnson, Linda; Grillon, Christian

    2007-01-01

    A recent fear-potentiated startle study in rodents suggested that extinction was not context dependent when extinction was conducted after a short delay following acquisition, suggesting that extinction can lead to erasure of fear learning in some circumstances. The main objective of this study was to attempt to replicate these findings in humans…

  1. Selective and protracted effect of nifedipine on fear memory extinction correlates with induced stress response.

    PubMed

    Waltereit, Robert; Mannhardt, Sönke; Nescholta, Sabine; Maser-Gluth, Christiane; Bartsch, Dusan

    2008-05-01

    Memory extinction, defined as a decrease of a conditioned response as a function of a non-reinforced conditioned stimulus presentation, has high biological and clinical relevance. Extinction is not a passive reversing or erasing of the plasticity associated with acquisition, but a novel, active learning process. Nifedipine blocks L-type voltage gated calcium channels (LVGCC) and has been shown previously to selectively interfere with the extinction, but not the acquisition, of fear memory. We studied here the effect of retrograde and anterograde shifts of nifedipine application, with respect to an extinction training, on the extinction of fear conditioning. Subcutaneous injection of 30 mg/kg nifedipine, at least up to 4 h before the extinction session, significantly impaired extinction, as did intraperitoneal injection of 15 mg/kg nifedipine, at least up to 2 h before extinction training. However, the injection of nifedipine also induced a strong and protracted stress response. The pharmacokinetics of nifedipine suggest that it was mainly this stress response that triggered the specific inhibition of extinction, not the blockade of LVGCC in the brain. Our results support recent findings that stress selectively interferes with the extinction, but not the acquisition, of fear memory. They also indicate that a pharmacological approach is not sufficient to study the role of brain LVGCC in learning and memory. Further research using specific genetically modified animals is necessary to delineate the role of LVGCC in fear memory extinction. PMID:18441293

  2. Inhibition of Rac1 activity in the hippocampus impaired extinction of contextual fear.

    PubMed

    Jiang, Lizhu; Mao, Rongrong; Tong, Jianbin; Li, Jinnan; Chai, Anping; Zhou, Qixin; Yang, Yuexiong; Wang, Liping; Li, Lingjiang; Xu, Lin

    2016-10-01

    Promoting extinction of fear memory is the main treatment of fear disorders, especially post-traumatic stress disorder (PTSD). However, fear extinction is often incomplete in these patients. Our previous study had shown that Rac1 activity in hippocampus plays a crucial role in the learning of contextual fear memory in rats. Here, we further investigated whether Rac1 activity also modulated the extinction of contextual fear memory. We found that massed extinction obviously upregulated hippocampal Rac1 activity and induced long-term extinction of contextual fear in rats. Intrahippocampal injection of the Rac1 inhibitor NSC23766 prevents extinction of contextual fear in massed extinction training rats. In contrast, long-spaced extinction downregulated Rac1 activity and caused less extinction. And Rac1 activator CN04-A promotes extinction of contextual fear in long-spaced extinction rats. Our study demonstrates that inhibition of Rac1 activity in the hippocampus impaired extinction of contextual fear, suggesting that modulating Rac1 activity of the hippocampus may be promising therapy of fear disorders. PMID:27329554

  3. HDAC1 regulates fear extinction in mice.

    PubMed

    Bahari-Javan, Sanaz; Maddalena, Andrea; Kerimoglu, Cemil; Wittnam, Jessica; Held, Torsten; Bähr, Mathias; Burkhardt, Susanne; Delalle, Ivanna; Kügler, Sebastian; Fischer, Andre; Sananbenesi, Farahnaz

    2012-04-11

    Histone acetylation has been implicated with the pathogenesis of neuropsychiatric disorders and targeting histone deacetylases (HDACs) using HDAC inhibitors was shown to be neuroprotective and to initiate neuroregenerative processes. However, little is known about the role of individual HDAC proteins during the pathogenesis of brain diseases. HDAC1 was found to be upregulated in patients suffering from neuropsychiatric diseases. Here, we show that virus-mediated overexpression of neuronal HDAC1 in the adult mouse hippocampus specifically affects the extinction of contextual fear memories, while other cognitive abilities were unaffected. In subsequent experiments we show that under physiological conditions, hippocampal HDAC1 is required for extinction learning via a mechanism that involves H3K9 deacetylation and subsequent trimethylation of target genes. In conclusion, our data show that hippocampal HDAC1 has a specific role in memory function. PMID:22496552

  4. MEST- avoid next extinction

    NASA Astrophysics Data System (ADS)

    Cao, Dayong

    2012-11-01

    Asteroid 2011 AG5 will impact on Earth in 2040. (See Donald K. Yoemans, ``Asteroid 2011 AG5 - A Reality Check,'' NASA-JPL, 2012) In 2011, The author say: the dark hole will take the dark comet to impact our solar system in 20 years, and give a systemic model between the sun and its companion-dark hole to explain why were there periodicity mass extinction on earth. (see Dayong Cao, BAPS.2011.CAL.C1.7, BAPS.2011.DFD.LA.24, BAPS.2012.APR.K1.78 and BAPS.2011.APR.K1.17) The dark Asteroid 2011 AG5 (as a dark comet) is made of the dark matter which has a space-time (as frequence-amplitude square) center- a different systemic model from solar systemic model. It can asborb the space-time and wave. So it is ``dark.'' When many dark matters hit on our earth, they can break our atom structure and our genetic code to trigger the Mass Extinction. In our experiments, consciousness can change the systematic model and code by a life-informational technology. So it can change the output signals of the solar cell. (see Dayong Cao, BAPS.2011.MAR.C1.286 and BAPS.2012.MAR.P33.14) So we will develop the genetic code of lives to evolution and sublimation, will use the dark matter to change the systemic model between dark hole and sun and will avoid next extinction.

  5. The Memory System Engaged During Acquisition Determines the Effectiveness of Different Extinction Protocols

    PubMed Central

    Goodman, Jarid; Packard, Mark G.

    2015-01-01

    Previous research indicates that extinction of rodent maze behavior may occur without explicit performance of the previously acquired response. In latent extinction, confining an animal to a previously rewarded goal location without reinforcement is typically sufficient to produce extinction of maze learning. However, previous studies have not determined whether latent extinction may be successfully employed to extinguish all types of memory acquired in the maze, or whether only specific types of memory may be vulnerable to latent extinction. The present study examined whether latent extinction may be effective across two plus-maze tasks that depend on anatomically distinct neural systems. Adult male Long-Evans rats were trained in a hippocampus-dependent place learning task (Experiment 1), in which animals were trained to approach a consistent spatial location for food reward. A separate group of rats were trained in a dorsolateral striatum-dependent response learning task (Experiment 2), in which animals were trained to make a consistent egocentric body-turn response for food reward. Following training, animals received response extinction or latent extinction. For response extinction, animals were given the opportunity to execute the original running approach response toward the empty food cup. For latent extinction, animals were confined to the original goal locations with the empty food cup, thus preventing them from making the original running approach response. Results indicate that, relative to no extinction, latent extinction was effective at extinguishing memory in the place learning task, but remained ineffective in the response learning task. In contrast, typical response extinction remained very effective at extinguishing memory in both place and response learning tasks. The present findings confirm that extinction of maze learning may occur with or without overt performance of the previously acquired response, but that the effectiveness of latent

  6. Extinction Events Can Accelerate Evolution

    PubMed Central

    Lehman, Joel; Miikkulainen, Risto

    2015-01-01

    Extinction events impact the trajectory of biological evolution significantly. They are often viewed as upheavals to the evolutionary process. In contrast, this paper supports the hypothesis that although they are unpredictably destructive, extinction events may in the long term accelerate evolution by increasing evolvability. In particular, if extinction events extinguish indiscriminately many ways of life, indirectly they may select for the ability to expand rapidly through vacated niches. Lineages with such an ability are more likely to persist through multiple extinctions. Lending computational support for this hypothesis, this paper shows how increased evolvability will result from simulated extinction events in two computational models of evolved behavior. The conclusion is that although they are destructive in the short term, extinction events may make evolution more prolific in the long term. PMID:26266804

  7. Rescuing Ecosystems from Extinction Cascades

    NASA Astrophysics Data System (ADS)

    Sahasrabudhe, Sagar; Motter, Adilson

    2010-03-01

    Food web perturbations stemming from climate change, overexploitation, invasive species, and natural disasters often cause an initial loss of species that results in a cascade of secondary extinctions. Using a predictive modeling framework, here we will present a systematic network-based approach to reduce the number of secondary extinctions. We will show that the extinction of one species can often be compensated by the concurrent removal of a second specific species, which is a counter-intuitive effect not previously tested in complex food webs. These compensatory perturbations frequently involve long-range interactions that are not a priori evident from local predator-prey relationships. Strikingly, in numerous cases even the early removal of a species that would eventually be extinct by the cascade is found to significantly reduce the number of cascading extinctions. Other nondestructive interventions based on partial removals and growth suppression and/or mortality increase are shown to sometimes prevent all secondary extinctions.

  8. Belief bias and the extinction of induced fear.

    PubMed

    Vroling, Maartje S; de Jong, Peter J

    2013-01-01

    Some people show slower extinction of UCS expectancies than other people. Little is known about what predicts such delayed extinction. Extinction requires that people deduce the logical implication of corrective experiences challenging the previously learned CS-UCS contingency. "A strong habitual tendency to confirm beliefs" may therefore be a powerful mechanism immunising against refutation of UCS expectancies. This study investigated whether individual differences in such a belief confirming tendency (a process called "belief bias") may help in explaining individual differences in extinction. We tested whether relatively strong belief bias predicts delayed extinction of experimentally induced UCS expectancies. In a differential aversive conditioning paradigm, we used UCS-irrelevant (Experiment 1) and UCS-relevant (Experiment 2) pictorial stimuli as CS⁺ and CS⁻, and electrical stimulation as UCS. Belief bias indeed predicted delayed extinction of UCS expectancies when the CS⁺ was UCS-relevant (as is typically the case for phobic stimuli, Experiment 2). The study provides preliminary evidence that enhanced belief bias may indeed play a role in the persistence of UCS expectancies, and can thereby contribute to the development and persistence of anxiety disorders. The results also point to the relevance of reasoning tendencies in the search for predictors of delayed extinction of UCS expectancies. PMID:23679911

  9. Attenuating fearful memories: effect of cued extinction on intrusions.

    PubMed

    Marks, Elizabeth H; Zoellner, Lori A

    2014-12-01

    Exposure-based therapies for posttraumatic stress disorder are thought to reduce intrusive memories through extinction processes. Methods that enhance extinction may translate to improved treatment. Rat research suggests retrieving a memory via a conditioned stimulus (CS) cue, and then modifying the retrieved memory within a specific reconsolidation window may enhance extinction. In humans, studies (e.g., Kindt & Soeter, 2013; Schiller et al., 2010) using basic learning paradigms show discrepant findings. Using a distressing film paradigm, participants (N = 148) completed fear acquisition and extinction. At extinction, they were randomized to 1 of 3 groups: CS cue within reconsolidation window, CS cue outside window, or non-CS cue within window. Intrusions were assessed 24 hr after extinction. Participants receiving the CS cue and completing extinction within the reconsolidation window had more intrusions (M = 2.40, SD = 2.54) than those cued outside (M = 1.65, SD = 1.70) or those receiving a non-CS cue (M = 1.24, SD = 1.26), F(2, 145) = 4.52, p = .01, d = 0.55. Consistent with the reconsolidation hypothesis, presenting a CS cue does appear to activate a specific period of time during which a memory can be updated. However, the CS cue caused increased, rather than decreased, frequency of intrusions. Understanding parameters of preextinction cueing may help us better understand reconsolidation as a potential memory updating mechanism. PMID:25286077

  10. Periodicity in marine extinction events

    NASA Technical Reports Server (NTRS)

    Sepkoski, J. John, Jr.; Raup, David M.

    1986-01-01

    The periodicity of extinction events is examined in detail. In particular, the temporal distribution of specific, identifiable extinction events is analyzed. The nature and limitations of the data base on the global fossil record is discussed in order to establish limits of resolution in statistical analyses. Peaks in extinction intensity which appear to differ significantly from background levels are considered, and new analyses of the temporal distribution of these peaks are presented. Finally, some possible causes of periodicity and of interdependence among extinction events over the last quarter billion years of earth history are examined.

  11. The impact of mass extinctions

    NASA Technical Reports Server (NTRS)

    Flessa, Karl W.

    1988-01-01

    In the years since Snowbird an explosive growth of research on the patterns, causes, and consequences of extinction was seen. The fossil record of extinction is better known, stratigraphic sections were scrutinized in great detail, and additional markers of environmental change were discovered in the rock record. However flawed, the fossil record is the only record that exists of natural extinction. Compilations from the primary literature contain a faint periodic signal: the extinctions of the past 250 my may be regulary spaced. The reality of the periodicity remains a subject for debate. The implications of periodicity are so profound that the debate is sure to continue. The greater precision from stratigraphic sections spanning extinction events has yet to resolve controversies concerning the rates at which extinctions occurred. Some sections seem to record sudden terminations, while others suggest gradual or steplike environmental deterioration. Unfortunately, the manner in which the strata record extinctions and compile stratigraphic ranges makes a strictly literal reading of the fossil record inadvisable. Much progress was made in the study of mass extinctions. The issues are more sharply defined but they are not fully resolved. Scenarios should look back to the phenomena they purport to explain - not just an iridium-rich layer, but the complex fabric of a mass extinction.

  12. Sex differences and estrous cycle in female rats interact with the effects of fluoxetine treatment on fear extinction

    PubMed Central

    Lebrón-Milad, K.; Tsareva, A.; Ahmed, N.; Milad, M. R.

    2014-01-01

    A common treatment for anxiety disorders is chronic administration of selective serotonin reuptake inhibitors (SSRIs) such as fluoxetine. Recent data suggest that SSRIs modulate fear responses after conditioned fear extinction and that gonadal hormones influence fear extinction. In this study we investigated the influence of sex and the estrous cycle on the effects of acute (experiment 1) and chronic (experiment 2) fluoxetine treatment on fear extinction. In experiment 1, rats received tone-footshock pairings during day 1. On day 2, rats received either fluoxetine (10mg/kg in 0.5mL) or vehicle prior to extinction learning. On day 3, extinction memory was assessed during extinction recall. In experiment 2, rats were exposed to a similar behavioral protocol, except that fluoxetine and vehicle were administered for 14 consecutives days after conditioning (days 2–15). Extinction learning and extinction recall occurred on days 15 and 16, respectively. Acute administration of fluoxetine increased fear responses equally in males and females during extinction learning and extinction recall. Chronic administration of fluoxetine reduced fear responses during extinction learning and extinction recall in female but not in male rats and this effect seems to be modulated by the estrous cycle. The SSRI-induced reduction of freezing during extinction learning and recall suggest a general anxiolytic effect of the drug treatment rather than a specific effect on extinction learning per se. Our data show evidence of sex-specific anxiolytic effects of 14-day treatment of fluoxetine while the acute anxiogenic effect of SSRI seems independent of sex effects. PMID:23886596

  13. Sex differences and estrous cycle in female rats interact with the effects of fluoxetine treatment on fear extinction.

    PubMed

    Lebrón-Milad, K; Tsareva, A; Ahmed, N; Milad, M R

    2013-09-15

    A common treatment for anxiety disorders is chronic administration of selective serotonin reuptake inhibitors (SSRIs) such as fluoxetine. Recent data suggest that SSRIs modulate fear responses after conditioned fear extinction and that gonadal hormones influence fear extinction. In this study we investigated the influence of sex and the estrous cycle on the effects of acute (experiment 1) and chronic (experiment 2) fluoxetine treatment on fear extinction. In experiment 1, rats received tone-footshock pairings during day 1. On day 2, rats received either fluoxetine (10mg/kg in 0.5mL) or vehicle prior to extinction learning. On day 3, extinction memory was assessed during extinction recall. In experiment 2, rats were exposed to a similar behavioral protocol, except that fluoxetine and vehicle were administered for 14 consecutives days after conditioning (days 2-15). Extinction learning and extinction recall occurred on days 15 and 16, respectively. Acute administration of fluoxetine increased fear responses equally in males and females during extinction learning and extinction recall. Chronic administration of fluoxetine reduced fear responses during extinction learning and extinction recall in female but not in male rats and this effect seems to be modulated by the estrous cycle. The SSRI-induced reduction of freezing during extinction learning and recall suggest a general anxiolytic effect of the drug treatment rather than a specific effect on extinction learning per se. Our data show evidence of sex-specific anxiolytic effects of 14-day treatment of fluoxetine while the acute anxiogenic effect of SSRI seems independent of sex effects. PMID:23886596

  14. Timing, tempo and paleoenvironmental implications of Deccan volcanism relative to the KTB extinction, what we can learn from the red bole record?

    NASA Astrophysics Data System (ADS)

    Adatte, Thierry; Sordet, Valentin; Keller, Gerta; Schoene, Blair; Samperton, Kyle; Khadri, Syed

    2016-04-01

    Deccan Traps erupted in three main phases with 6% total Deccan volume in phase-1 (C30n), 80% in phase-2 (C29r) and 14% in phase-3 (C29n). Recent studies indicate that the bulk (80%) of Deccan trap eruptions (phase-2) occurred over a relatively short time interval in magnetic polarity C29r. U-Pb zircon geochronology shows that the main phase-2 began 250 ky before the Cretaceous-Tertiary (KT) mass extinction and continued into the early Danian suggesting a cause-and-effect relationship. In India a strong floral response is observed as a direct consequence of volcanic phase-2. Shortly after the onset of Deccan phase-2, the floral association dominated by gymnosperms and angiosperms was decimated as indicated by a sharp decrease in pollen and spores coupled with the appearance of fungi, which mark increasing stress conditions as a direct result of volcanic activity. The inter-trappean sediments deposited in phase-2 are characterized by the highest alteration CIA index values suggesting increased acid rains due to SO2 emissions. In addition, a sharp decrease in pollen and spores coupled with the appearance of fungi mark increasing stress conditions, which are likely a direct result of volcanic activity. Bulk organic geochemistry points to a strong degradation of the indigenous organic matter, suggesting that the biomass was oxidized in acidic conditions triggered by intense volcanic activity. Closer to the eruption center, the lava flows are generally separated by red weathered horizons known as red boles that mark quiescent periods between basalt flows. Red boles have increasingly attracted the attention of researchers to understand the climatic and paleoenvironmental impact of Continental Flood Basalts (CFB). Recent advances in U-Pb dating of Deccan lava flows, studies of weathering patterns and paleoclimatic information gained from multiproxy analyses of red bole beds (e.g., lithology, mineralogy, geochemistry) yield crucial evidence of environmental changes

  15. Neurobiological Basis of Failure to Recall Extinction Memory in Posttraumatic Stress Disorder

    PubMed Central

    Milad, Mohammed R.; Pitman, Roger K.; Ellis, Cameron B.; Gold, Andrea L.; Shin, Lisa M; Lasko, Natasha B.; Zeidan, Mohamed A.; Handwerger, Kathryn; Orr, Scott P.; Rauch, Scott L.

    2009-01-01

    Background: A clinical characteristic of posttraumatic stress disorder (PTSD) is persistently elevated fear responses to stimuli associated with the traumatic event. The objective herein is to determine whether extinction of fear responses is impaired in PTSD and whether such impairment is related to dysfunctional activation of brain regions known to be involved in fear extinction, viz., amygdala, hippocampus, ventromedial prefrontal cortex (vmPFC), and dorsal anterior cingulate cortex (dACC). Methods: Sixteen individuals diagnosed with PTSD and 15 trauma-exposed non-PTSD controls (TENCs) underwent a two-day fear conditioning and extinction protocol in a 3T fMRI scanner. Conditioning and extinction training were conducted on day 1. Extinction recall (or extinction memory) test was conducted on day 2 (extinguished conditioned stimuli presented in the absence of shock). Skin conductance response (SCR) was scored throughout the experiment as an index of the conditioned response. Results: SCR data revealed no significant differences between groups during acquisition and extinction of conditioned fear on day 1. On day 2, however, PTSD subjects showed impaired recall of extinction memory. Analysis of fMRI data showed greater amygdala activation in the PTSD group during day 1 extinction learning. During extinction recall, lesser activation in hippocampus and vmPFC, and greater activation in dACC, was observed in the PTSD group. The magnitude of extinction memory across all subjects was correlated with activation of hippocampus and vmPFC during extinction recall testing. Conclusions: These findings support the hypothesis that fear extinction is impaired in PTSD. They further suggest that dysfunctional activation in brain structures that mediate fear extinction learning, and especially its recall, underlie this impairment. PMID:19748076

  16. Extinction from a Rationalist Perspective

    PubMed Central

    Gallistel, C. R.

    2012-01-01

    The merging of the computational theory of mind and evolutionary thinking leads to a kind of rationalism, in which enduring truths about the world have become implicit in the computations that enable the brain to cope with the experienced world. The dead reckoning computation, for example, is implemented within the brains of animals as one of the mechanisms that enables them to learn where they are (Gallistel, 1990, 1995). It integrates a velocity signal with respect to a time signal. Thus, the manner in which position and velocity relate to one another in the world is reflected in the manner in which signals representing those variables are processed in the brain. I use principles of information theory and Bayesian inference to derive from other simple principles explanations for: 1) the failure of partial reinforcement to increase reinforcements to acquisition; 2) the partial reinforcement extinction effect; 3) spontaneous recovery; 4) renewal; 5) reinstatement; 6) resurgence (aka facilitated reacquisition). Like the principle underlying dead-reckoning, these principles are grounded in analytic considerations. They are the kind of enduring truths about the world that are likely to have shaped the brain's computations. PMID:22391153

  17. Extinction from a rationalist perspective.

    PubMed

    Gallistel, C R

    2012-05-01

    The merging of the computational theory of mind and evolutionary thinking leads to a kind of rationalism, in which enduring truths about the world have become implicit in the computations that enable the brain to cope with the experienced world. The dead reckoning computation, for example, is implemented within the brains of animals as one of the mechanisms that enables them to learn where they are (Gallistel, 1990, 1995). It integrates a velocity signal with respect to a time signal. Thus, the manner in which position and velocity relate to one another in the world is reflected in the manner in which signals representing those variables are processed in the brain. I use principles of information theory and Bayesian inference to derive from other simple principles explanations for: (1) the failure of partial reinforcement to increase reinforcements to acquisition; (2) the partial reinforcement extinction effect; (3) spontaneous recovery; (4) renewal; (5) reinstatement; (6) resurgence (aka facilitated reacquisition). Like the principle underlying dead-reckoning, these principles are grounded in analytic considerations. They are the kind of enduring truths about the world that are likely to have shaped the brain's computations. PMID:22391153

  18. Extinction during reconsolidation of threat memory diminishes prefrontal cortex involvement

    PubMed Central

    Schiller, Daniela; Kanen, Jonathan W.; LeDoux, Joseph E.; Monfils, Marie-H.; Phelps, Elizabeth A.

    2013-01-01

    Controlling learned defensive responses through extinction does not alter the threat memory itself, but rather regulates its expression via inhibitory influence of the prefrontal cortex (PFC) over amygdala. Individual differences in amygdala–PFC circuitry function have been linked to trait anxiety and posttraumatic stress disorder. This finding suggests that exposure-based techniques may actually be least effective in those who suffer from anxiety disorders. A theoretical advantage of techniques influencing reconsolidation of threat memories is that the threat representation is altered, potentially diminishing reliance on this PFC circuitry, resulting in a more persistent reduction of defensive reactions. We hypothesized that timing extinction to coincide with threat memory reconsolidation would prevent the return of defensive reactions and diminish PFC involvement. Two conditioned stimuli (CS) were paired with shock and the third was not. A day later, one stimulus (reminded CS+) but not the other (nonreminded CS+) was presented 10 min before extinction to reactivate the threat memory, followed by extinction training for all CSs. The recovery of the threat memory was tested 24 h later. Extinction of the nonreminded CS+ (i.e., standard extinction) engaged the PFC, as previously shown, but extinction of the reminded CS+ (i.e., extinction during reconsolidation) did not. Moreover, only the nonreminded CS+ memory recovered on day 3. These results suggest that extinction during reconsolidation prevents the return of defensive reactions and diminishes PFC involvement. Reducing the necessity of the PFC–amygdala circuitry to control defensive reactions may help overcome a primary obstacle in the long-term efficacy of current treatments for anxiety disorders. PMID:24277809

  19. Pleistocene extinctions: haunting the survivors.

    PubMed

    Hofreiter, Michael

    2007-08-01

    For many years, the megafaunal extinctions at the end of the Pleistocene have been assumed to have affected only those species that became extinct. However, recent analyses show that the surviving species may also have experienced losses in terms of genetic and ecological diversity. PMID:17686436

  20. Ecology: Dynamics of Indirect Extinction.

    PubMed

    Montoya, Jose M

    2015-12-01

    The experimental identification of the mechanism by which extinctions of predators trigger further predator extinctions emphasizes the role of indirect effects between species in disturbed ecosystems. It also has deep consequences for the hidden magnitude of the current biodiversity crisis. PMID:26654371

  1. The effects of compound stimulus extinction and inhibition of noradrenaline reuptake on the renewal of alcohol seeking.

    PubMed

    Furlong, T M; Pan, M J; Corbit, L H

    2015-01-01

    Alcohol-related stimuli can trigger relapse of alcohol-seeking behaviors even after extended periods of abstinence. Extinction of such stimuli can reduce their impact on relapse; however, the expression of extinction can be disrupted when testing occurs outside the context where extinction learning took place, an effect termed renewal. Behavioral and pharmacological methods have recently been shown to augment extinction learning; yet, it is not known whether the improved expression of extinction following these treatments remains context-dependent. Here we examined whether two methods, compound-stimulus extinction and treatment with the noradrenaline reuptake inhibitor atomoxetine, would reduce the vulnerability of extinction to a change in context. Following alcohol self-administration, responding was extinguished in a distinct context. After initial extinction, further extinction was given to a target stimulus presented in compound with another alcohol-predictive stimulus intended to augment prediction error (Experiment 1) or after a systemic injection of atomoxetine (1.0 mg kg(-1); Experiment 2). A stimulus extinguished as part of a compound elicited less responding than a stimulus receiving equal extinction alone regardless of whether animals were tested in the training or extinction context; however, reliable renewal was not observed in this paradigm. Importantly, atomoxetine enhanced extinction relative to controls even in the presence of a reliable renewal effect. Thus, extinction of alcohol-seeking behavior can be improved by extinguishing multiple alcohol-predictive stimuli or enhancing noradrenaline neurotransmission during extinction training. Importantly, both methods improve extinction even when the context is changed between extinction training and test, and thus could be utilized to enhance the outcome of extinction-based treatments for alcohol-use disorders. PMID:26327688

  2. Fear extinction can be made state-dependent on peripheral epinephrine: role of norepinephrine in the nucleus tractus solitarius.

    PubMed

    Rosa, Jessica; Myskiw, Jociane C; Furini, Cristiane R G; Sapiras, Gerson G; Izquierdo, Ivan

    2014-09-01

    We investigate whether the extinction of inhibitory avoidance (IA) learning can be subjected to endogenous state-dependence with systemic injections of epinephrine (E), and whether endogenous norepinephrine (NE) and the nucleus tractus solitarius (NTS)→locus coeruleus→hippocampus/amygdala (HIPP/BLA) pathway participate in this. Rats trained in IA were submitted to two sessions of extinction 24 h apart: In the first, the animals were submitted to a training session of extinction, and in the second they were tested for the retention of extinction. Saline or E were given i.p. immediately after the extinction training (post-extinction training injections) and/or 6 min before the extinction test (pre-extinction test). Post-extinction training E (50 or 100 μg/kg) induced a poor retrieval of extinction in the test session of this task unless an additional E injection (50 μg/kg) was given prior to the extinction test. This suggested state-dependence. Muscimol (0.01 μg/side) microinfused into the NTS prior to the extinction test session blocked E-induced state-dependence. Norepinephrine (NE, 1 μg/side) infused bilaterally into NTS restores the extinction impairment caused by post-extinction training i.p. E. In animals with bilateral NTS blockade induced by muscimol, NE (1 μg/side) given prior to the extinction test into the CA1 region of the dorsal hippocampus or into the basolateral amygdala restored the normal extinction levels that had been impaired by muscimol. These results suggest a role for the NTS→locus coeruleus→HIPP/BLA pathway in the retrieval of extinction, as it has been shown to have in the consolidation of inhibitory avoidance and of object recognition learning. PMID:24161888

  3. Acoustic integrated extinction

    PubMed Central

    Norris, Andrew N.

    2015-01-01

    The integrated extinction (IE) is defined as the integral of the scattering cross section as a function of wavelength. Sohl et al. (2007 J. Acoust. Soc. Am. 122, 3206–3210. (doi:10.1121/1.2801546)) derived an IE expression for acoustic scattering that is causal, i.e. the scattered wavefront in the forward direction arrives later than the incident plane wave in the background medium. The IE formula was based on electromagnetic results, for which scattering is causal by default. Here, we derive a formula for the acoustic IE that is valid for causal and non-causal scattering. The general result is expressed as an integral of the time-dependent forward scattering function. The IE reduces to a finite integral for scatterers with zero long-wavelength monopole and dipole amplitudes. Implications for acoustic cloaking are discussed and a new metric is proposed for broadband acoustic transparency. PMID:27547100

  4. Extinction in multiple virtual reality contexts diminishes fear reinstatement in humans

    PubMed Central

    Dunsmoor, Joseph E.; Åhs, Fredrik; Zielinski, David J.; LaBar, Kevin S.

    2014-01-01

    Although conditioned fear can be effectively extinguished by unreinforced exposure to a threat cue, fear responses tend to return when the cue is encountered some time after extinction (spontaneous recovery), in a novel environment (renewal), or following presentation of an aversive stimulus (reinstatement). As extinction represents a context-dependent form of new learning, one possible strategy to circumvent the return of fear is to conduct extinction across several environments. Here, we tested the effectiveness of multiple context extinction in a two-day fear conditioning experiment using 3-D virtual reality technology to create immersive, ecologically-valid context changes. Fear-potentiated startle served as the dependent measure. All three experimental groups initially acquired fear in a single context. A multiple extinction group then underwent extinction in three contexts, while a second group underwent extinction in the acquisition context and a third group underwent extinction in a single different context. All groups returned 24 hours later to test for return of fear in the extinction context (spontaneous recovery) and a novel context (renewal and reinstatement/test). Extinction in multiple contexts attenuated reinstatement of fear but did not reduce spontaneous recovery. Results from fear renewal were tendential. Our findings suggest that multi-context extinction can reduce fear relapse following an aversive event – an event that often induces return of fear in real-world settings -- and provides empirical support for conducting exposure-based clinical treatments across a variety of environments. PMID:24583374

  5. Extinction in multiple virtual reality contexts diminishes fear reinstatement in humans.

    PubMed

    Dunsmoor, Joseph E; Ahs, Fredrik; Zielinski, David J; LaBar, Kevin S

    2014-09-01

    Although conditioned fear can be effectively extinguished by unreinforced exposure to a threat cue, fear responses tend to return when the cue is encountered some time after extinction (spontaneous recovery), in a novel environment (renewal), or following presentation of an aversive stimulus (reinstatement). As extinction represents a context-dependent form of new learning, one possible strategy to circumvent the return of fear is to conduct extinction across several environments. Here, we tested the effectiveness of multiple context extinction in a two-day fear conditioning experiment using 3-D virtual reality technology to create immersive, ecologically-valid context changes. Fear-potentiated startle served as the dependent measure. All three experimental groups initially acquired fear in a single context. A multiple extinction group then underwent extinction in three contexts, while a second group underwent extinction in the acquisition context and a third group underwent extinction in a single different context. All groups returned 24h later to test for return of fear in the extinction context (spontaneous recovery) and a novel context (renewal and reinstatement/test). Extinction in multiple contexts attenuated reinstatement of fear but did not reduce spontaneous recovery. Results from fear renewal were tendential. Our findings suggest that multi-context extinction can reduce fear relapse following an aversive event--an event that often induces return of fear in real-world settings--and provides empirical support for conducting exposure-based clinical treatments across a variety of environments. PMID:24583374

  6. Measuring Extinction with ALE

    NASA Astrophysics Data System (ADS)

    Zimmer, Peter C.; McGraw, J. T.; Gimmestad, G. G.; Roberts, D.; Stewart, J.; Smith, J.; Fitch, J.

    2007-12-01

    ALE (Astronomical LIDAR for Extinction) is deployed at the University of New Mexico's (UNM) Campus Observatory in Albuquerque, NM. It has begun a year-long testing phase prior deployment at McDonald Observatory in support of the CCD/Transit Instrument II (CTI-II). ALE is designed to produce a high-precision measurement of atmospheric absorption and scattering above the observatory site every ten minutes of every moderately clear night. LIDAR (LIght Detection And Ranging) is the VIS/UV/IR analog of radar, using a laser, telescope and time-gated photodetector instead of a radio transmitter, dish and receiver. In the case of ALE -- an elastic backscatter LIDAR -- 20ns-long, eye-safe laser pulses are launched 2500 times per second from a 0.32m transmitting telescope co-mounted with a 50mm short-range receiver on an alt-az mounted 0.67m long-range receiver. Photons from the laser pulse are scattered and absorbed as the pulse propagates through the atmosphere, a portion of which are scattered into the field of view of the short- and long-range receiver telescopes and detected by a photomultiplier. The properties of a given volume of atmosphere along the LIDAR path are inferred from both the altitude-resolved backscatter signal as well as the attenuation of backscatter signal from altitudes above it. We present ALE profiles from the commissioning phase and demonstrate some of the astronomically interesting atmospheric information that can be gleaned from these data, including, but not limited to, total line-of-sight extinction. This project is funded by NSF Grant 0421087.

  7. Extinction of Harrington's Mountain Goat

    NASA Astrophysics Data System (ADS)

    Mead, Jim I.; Martin, Paul S.; Euler, Robert C.; Long, Austin; Jull, A. J. T.; Toolin, Laurence J.; Donahue, Douglas J.; Linick, T. W.

    1986-02-01

    Keratinous horn sheaths of the extinct Harrington's mountain goat, Oreamnos harringtoni, were recovered at or near the surface of dry caves of the Grand Canyon, Arizona. Twenty-three separate specimens from two caves were dated nondestructively by the tandem accelerator mass spectrometer (TAMS). Both the TAMS and the conventional dates indicate that Harrington's mountain goat occupied the Grand Canyon for at least 19,000 years prior to becoming extinct by 11,160 ± 125 radiocarbon years before present. The youngest average radiocarbon dates on Shasta ground sloths, Nothrotheriops shastensis, from the region are not significantly younger than those on extinct mountain goats. Rather than sequential extinction with Harrington's mountain goat disappearing from the Grand Canyon before the ground sloths, as one might predict in view of evidence of climatic warming at the time, the losses were concurrent. Both extinctions coincide with the regional arrival of Clovis hunters.

  8. Extinction of Harrington's mountain goat

    SciTech Connect

    Mead, J.I.; Martin, P.S.; Euler, R.C.; Long, A.; Jull, A.J.T.; Toolin, L.J.; Donahue, D.J.; Linick, T.W.

    1986-02-01

    Keratinous horn sheaths of the extinct Harrington's mountain goat, Oreamnos harringtoni, were recovered at or near the surface of dry caves of the Grand Canyon, Arizona. Twenty-three separate specimens from two caves were dated nondestructively by the tandem accelerator mass spectrometer (TAMS). Both the TAMS and the conventional dates indicate that Harrington's mountain goat occupied the Grand Canyon for at least 19,000 years prior to becoming extinct by 11,160 +/- 125 radiocarbon years before present. The youngest average radiocarbon dates on Shasta ground sloths, Nothrotheriops shastensis, from the region are not significantly younger than those on extinct mountain goats. Rather than sequential extinction with Harrington's mountain goat disappearing from the Grand Canyon before the ground sloths, as one might predict in view of evidence of climatic warming at the time, the losses were concurrent. Both extinctions coincide with the regional arrival of Clovis hunters.

  9. Interstellar extinction in the ultraviolet

    NASA Technical Reports Server (NTRS)

    Bless, R. C.; Savage, B. D.

    1972-01-01

    Interstellar extinction curves over the region 3600-1100 A for 17 stars are presented. The observations were made by the two Wisconsin spectrometers onboard the OAO-2 with spectral resolutions of 10 A and 20 A. The extinction curves generally show a pronounced maximum at 2175 plus or minus 25 A, a broad minimum in the region 1800-1350 A, and finally a rapid rise to the far ultraviolet. Large extinction variations from star to star are found, especially in the far ultraviolet; however, with only two possible exceptions in this sample, the wavelength at the maximum of the extinction bump is essentially constant. These data are combined with visual and infrared observations to display the extinction behavior over a range in wavelength of about a factor of 20.

  10. The end-Permian mass extinction: A complex, multicausal extinction

    NASA Technical Reports Server (NTRS)

    Erwin, D. H.

    1994-01-01

    The end-Permian mass extinction was the most extensive in the history of life and remains one of the most complex. Understanding its causes is particularly important because it anchors the putative 26-m.y. pattern of periodic extinction. However, there is no good evidence for an impact and this extinction appears to be more complex than others, involving at least three phases. The first began with the onset of a marine regression during the Late Permian and resulting elimination of most marine basins, reduction in habitat area, and increased climatic instability; the first pulse of tetrapod extinctions occurred in South Africa at this time. The second phase involved increased regression in many areas (although apparently not in South China) and heightened climatic instability and environmental degradation. Release of gas hydrates, oxidation of marine carbon, and the eruption of the Siberian flood basalts occurred during this phase. The final phase of the extinction episode began with the earliest Triassic marine regression and destruction of nearshore continental habitats. Some evidence suggests oceanic anoxia may have developed during the final phase of the extinction, although it appears to have been insufficient to the sole cause of the extinction.

  11. Evidence for Recovery of Fear Following Immediate Extinction in Rats and Humans

    ERIC Educational Resources Information Center

    Schiller, Daniela; Cain, Christopher K.; Curley, Nina G.; Schwartz, Jennifer S.; Stern, Sarah A.; LeDoux, Joseph E.; Phelps, Elizabeth A.

    2008-01-01

    Fear responses can be eliminated through extinction, a procedure involving the presentation of fear-eliciting stimuli without aversive outcomes. Extinction is believed to be mediated by new inhibitory learning that acts to suppress fear expression without erasing the original memory trace. This hypothesis is supported mainly by behavioral data…

  12. Selective and Protracted Effect of Nifedipine on Fear Memory Extinction Correlates with Induced Stress Response

    ERIC Educational Resources Information Center

    Waltereit, Robert; Mannhardt, Sonke; Nescholta, Sabine; Maser-Gluth, Christiane; Bartsch, Dusan

    2008-01-01

    Memory extinction, defined as a decrease of a conditioned response as a function of a non-reinforced conditioned stimulus presentation, has high biological and clinical relevance. Extinction is not a passive reversing or erasing of the plasticity associated with acquisition, but a novel, active learning process. Nifedipine blocks L-type voltage…

  13. Reexposure to the Amnestic Agent Alleviates Cycloheximide-Induced Retrograde Amnesia for Reactivated and Extinction Memories

    ERIC Educational Resources Information Center

    Briggs, James F.; Olson, Brian P.

    2013-01-01

    We investigated whether reexposure to an amnestic agent would reverse amnesia for extinction of learned fear similar to that of a reactivated memory. When cycloheximide (CHX) was administered immediately after a brief cue-induced memory reactivation (15 sec) and an extended extinction session (12 min) rats showed retrograde amnesia for both…

  14. The Role of the Medial Prefrontal Cortex in Trace Fear Extinction

    ERIC Educational Resources Information Center

    Kwapis, Janine L.; Jarome, Timothy J.; Helmstetter, Fred J.

    2015-01-01

    The extinction of delay fear conditioning relies on a neural circuit that has received much attention and is relatively well defined. Whether this established circuit also supports the extinction of more complex associations, however, is unclear. Trace fear conditioning is a better model of complex relational learning, yet the circuit that…

  15. Extinction, Reacquisition, and Rapid Forgetting of Eyeblink Conditioning in Developing Rats

    ERIC Educational Resources Information Center

    Brown, Kevin L.; Freeman, John H.

    2014-01-01

    Eyeblink conditioning is a well-established model for studying the developmental neurobiology of associative learning and memory. However, age differences in extinction and subsequent reacquisition have yet to be studied using this model. The present study examined extinction and reacquisition of eyeblink conditioning in developing rats. In…

  16. Different Mechanisms of Fear Extinction Dependent on Length of Time since Fear Acquisition

    ERIC Educational Resources Information Center

    Davis, Michael; Myers, Karyn M.; Ressler, Kerry J.

    2006-01-01

    Fear extinction is defined as a decline in conditioned fear responses (CRs) following nonreinforced exposure to a feared conditioned stimulus (CS). Behavioral evidence indicates that extinction is a form of inhibitory learning: Extinguished fear responses reappear with the passage of time (spontaneous recovery), a shift of context (renewal), and…

  17. Sleep supports cued fear extinction memory consolidation independent of circadian phase.

    PubMed

    Melo, Irene; Ehrlich, Ingrid

    2016-07-01

    Sleep promotes memory, particularly for declarative learning. However, its role in non-declarative, emotional memories is less well understood. Some studies suggest that sleep may influence fear-related memories, and thus may be an important factor determining the outcome of treatments for emotional disorders such as post-traumatic stress disorder. Here, we investigated the effect of sleep deprivation and time of day on fear extinction memory consolidation. Mice were subjected to a cued Pavlovian fear and extinction paradigm at the beginning of their resting or active phase. Immediate post-extinction learning sleep deprivation for 5h compromised extinction memory when tested 24h after learning. Context-dependent extinction memory recall was completely prevented by sleep-manipulation during the resting phase, while impairment was milder during the active phase and extinction memory retained its context-specificity. Importantly, control experiments excluded confounding factors such as differences in baseline locomotion, fear generalization and stress hormone levels. Together, our findings indicate that post-learning sleep supports cued fear extinction memory consolidation in both circadian phases. The lack of correlation between memory efficacy and sleep time suggests that extinction memory may be influenced by specific sleep events in the early consolidation period. PMID:27109918

  18. Cannabinoid modulation of fear extinction brain circuits: a novel target to advance anxiety treatment.

    PubMed

    Rabinak, Christine A; Phan, K Luan

    2014-01-01

    Anxiety disorders, such as post-traumatic stress (PTSD), panic, and phobic disorders, can be conceptualized as a failure to inhibit inappropriate fear responses. A common, effective treatment strategy involves repeated presentations to the feared cue without any danger (extinction). However, extinction learning has a number of important limitations, and enhancing its effects, generalizability and durability via cognitive enhancers may improve its therapeutic impact. In this review we focus specifically on the role of the cannabinoid system in fear extinction learning and its retention. We address the following questions: What are the neural circuits mediating fear extinction?; Can we make fear extinction more effective?; Can cannabinoids facilitate fear extinction in humans?; How might the cannabinoid system effect fear extinction? Collectively, translational evidence suggest that enhancing cannabinoid transmission may facilitate extinction learning and its recall, and that the cannabinoid system is a potential pharmacological target for improving the active learning that occurs during exposure-based behavioral treatments prompting future research in terms of mechanisms research, novel treatment approaches ('cognitive enhancers'), and pharmacotherapeutic drug discovery. PMID:23829364

  19. Brain Mechanisms of Extinction of the Classically Conditioned Eyeblink Response

    ERIC Educational Resources Information Center

    Thompson, Richard F.; Robleto, Karla; Poulos, Andrew M.

    2004-01-01

    It is well established that the cerebellum and its associated circuitry are essential for classical conditioning of the eyeblink response and other discrete motor responses (e.g., limb flexion, head turn, etc.) learned with an aversive unconditioned stimulus (US). However, brain mechanisms underlying extinction of these responses are still…

  20. Extinction Circuits for Fear and Addiction Overlap in Prefrontal Cortex

    ERIC Educational Resources Information Center

    Peters, Jamie; Kalivas, Peter W.; Quirk, Gregory J.

    2009-01-01

    Extinction is a form of inhibitory learning that suppresses a previously conditioned response. Both fear and drug seeking are conditioned responses that can lead to maladaptive behavior when expressed inappropriately, manifesting as anxiety disorders and addiction, respectively. Recent evidence indicates that the medial prefrontal cortex (mPFC) is…

  1. Mass Extinctions in Earth's History

    NASA Astrophysics Data System (ADS)

    Ward, P. D.

    2002-12-01

    Mass extinctions are short intervals of elevated species death. Possible causes of Earth's mass extinctions are both external (astronomical) and internal (tectonic and biotic changes from planetary mechanisms). Paleontologists have identified five "major" mass extinctions (>50 die-off in less than a million years) and more than 20 other minor events over the past 550 million years. Earlier major extinction events undoubtedly also occurred, but we have no fossil record; these were probably associated with, for example, the early heavy bombardment that cleared out the solar system, the advent of oxygen in the atmosphere, and various "snowball Earth" events. Mass extinctions are viewed as both destructive (species death ) and constructive, in that they allow evolutionary innovation in the wake of species disappearances. From an astrobiological perspective, mass extinctions must be considered as able both to reduce biodiversity and even potentially end life on any planet. Of the five major mass extinctions identified on Earth, only one (the Cretaceous/Tertiary event 65 million years ago that famously killed off the dinosaurs ) is unambiguously related to the impact of an asteroid or comet ( 10-km diameter). The Permian/Triassic (250 Myr ago) and Triassic/Jurassic (202 Myr ago) events are now the center of debate between those favoring impact and those suggesting large volume flooding by basaltic lavas. The final two events, Ordovician (440 Myr ago) and Devonian (370 Myr ago) have no accepted causal mechanisms.

  2. Extinction in young massive clusters

    NASA Astrophysics Data System (ADS)

    De Marchi, Guido; Panagia, Nino

    2016-01-01

    Up to ages of ~100 Myr, massive clusters are still swamped in large amounts of gas and dust, causing considerable and uneven levels of extinction. At the same time, large grains (ices?) produced by type II supernovae profoundly alter the interstellar medium (ISM), thus resulting in extinction properties very different from those of the diffuse ISM. To obtain physically meaningful parameters of stars (luminosities, effective temperatures, masses, ages, etc.) we must understand and measure the local extinction law. We have developed a powerful method to unambiguously determine the extinction law everywhere across a cluster field, using multi-band photometry of red giant stars belonging to the red clump (RC) and are applying it to young massive clusters in the Local Group. In the Large Magellanic Cloud, with about 20 RC stars per arcmin2, for each field we can easily derive an accurate extinction curve over the entire wavelength range of the photometry. As an example, we present the extinction law of the Tarantula nebula (30 Dor) based on thousands of stars observed as part of the Hubble Tarantula Treasury Project. We discuss how the incautious adoption of the Milky Way extinction law in the analysis of massive star forming regions may lead to serious underestimates of the fluxes and of the star formation rates by factors of 2 or more.

  3. Spatial memory extinction: a c-Fos protein mapping study.

    PubMed

    Méndez-Couz, M; Conejo, N M; Vallejo, G; Arias, J L

    2014-03-01

    While the neuronal basis of spatial memory consolidation has been thoroughly studied, the substrates mediating the process of extinction remain largely unknown. This study aimed to evaluate the functional contribution of selected brain regions during the extinction of a previously acquired spatial memory task in the Morris water maze. For that purpose, we used adult male Wistar rats trained in a spatial reference memory task. Learning-related changes in c-Fos inmunoreactive cells after training were evaluated in cortical and subcortical regions. Results show that removal of the hidden platform in the water maze induced extinction of the previously reinforced escape behavior after 16 trials, without spontaneous recovery 24h later. Extinction was related with significantly higher numbers of c-Fos positive nuclei in amygdala nuclei and prefrontal cortex. On the other hand, the lateral mammillary bodies showed higher number of c-Fos positive cells than the control group. Therefore, in contrast with the results obtained in studies of classical conditioning, we show the involvement of diencephalic structures mediating this kind of learning. In summary, our findings suggest that medial prefrontal cortex, the amygdala complex and diencephalic structures like the lateral mammillary nuclei are relevant for the extinction of spatial memory. PMID:24315832

  4. Hunger Promotes Fear Extinction by Activation of an Amygdala Microcircuit.

    PubMed

    Verma, Dilip; Wood, James; Lach, Gilliard; Herzog, Herbert; Sperk, Guenther; Tasan, Ramon

    2016-01-01

    Emotions control evolutionarily-conserved behavior that is central to survival in a natural environment. Imbalance within emotional circuitries, however, may result in malfunction and manifestation of anxiety disorders. Thus, a better understanding of emotional processes and, in particular, the interaction of the networks involved is of considerable clinical relevance. Although neurobiological substrates of emotionally controlled circuitries are increasingly evident, their mutual influences are not. To investigate interactions between hunger and fear, we performed Pavlovian fear conditioning in fasted wild-type mice and in mice with genetic modification of a feeding-related gene. Furthermore, we analyzed in these mice the electrophysiological microcircuits underlying fear extinction. Short-term fasting before fear acquisition specifically impaired long-term fear memory, whereas fasting before fear extinction facilitated extinction learning. Furthermore, genetic deletion of the Y4 receptor reduced appetite and completely impaired fear extinction, a phenomenon that was rescued by fasting. A marked increase in feed-forward inhibition between the basolateral and central amygdala has been proposed as a synaptic correlate of fear extinction and involves activation of the medial intercalated cells. This form of plasticity was lost in Y4KO mice. Fasting before extinction learning, however, resulted in specific activation of the medial intercalated neurons and re-established the enhancement of feed-forward inhibition in this amygdala microcircuit of Y4KO mice. Hence, consolidation of fear and extinction memories is differentially regulated by hunger, suggesting that fasting and modification of feeding-related genes could augment the effectiveness of exposure therapy and provide novel drug targets for treatment of anxiety disorders. PMID:26062787

  5. New theories about ancient extinctions

    USGS Publications Warehouse

    Spall, H.

    1986-01-01

    But all this may be changing. Mass extinctions have been very much in the news in the last few years, triggered in large part by the proposal that the extinction of the dinosaurs and marine animals was caused by a catastrophic collision between the Earth and an extra-terrestrial body (bolide). Recently an equally contentious suggestion has been made that mass extinctions have swept the Earth every 26 to 31 million years for at least the last 250 million years-caused by encounters with some kind of extra-terrestrial object such as one of the asteroids or the comets. 

  6. Issues in the extinction of specific stimulus-outcome associations in Pavlovian conditioning.

    PubMed

    Delamater, Andrew R

    2012-05-01

    This paper reviews a variety of studies designed to examine the effects of extinction upon control by specific stimulus-outcome (S-O) associations in Pavlovian conditioning. Studies conducted with rats in a magazine approach conditioning paradigm have shown that control by specific S-O associations is normally unaffected by extinction treatments, although other aspects of conditioned responding seem affected in a more enduring way. However, recent work suggests that extinction can undermine control by such associations if it is administered after the conditioned stimulus is weakly encoded. The results from these studies suggest that it may be important to consider multiple response systems in assessing the impact of extinction. Studies conducted with the flavor preference learning paradigm in rats also show that specific S-O associations can be undermined by procedures that involve presenting a flavor cue in the absence of its associated nutrient. These findings provide no support for the view that flavor preference learning necessarily entails some unique learning process that differs from more conventional processes. As in other situations, some of these effects likely involve a masking process, but the extent to which masking or true associative weakening occurs in extinction more generally is a topic that is not well understood. Finally, we present some data to suggest that extinction also involves conditional "occasion-setting" control by contextual cues. Special procedures are recommended in assessing such learning when the goal is to distinguish this form of learning from other more conventional mechanisms of extinction. PMID:22465262

  7. The effect of temporary amygdala inactivation on extinction and reextinction of fear in the developing rat: unlearning as a potential mechanism for extinction early in development.

    PubMed

    Kim, Jee Hyun; Richardson, Rick

    2008-02-01

    It is well accepted that fear extinction does not cause erasure of the original conditioned stimulus (CS)-unconditioned stimulus association in the adult rat because the extinguished fear often returns (e.g., renewal and reinstatement). Furthermore, extinction is NMDA and GABA dependent, showing that extinction involves new inhibitory learning. We have recently observed each of these extinction-related phenomena in 24-d-old but not in 17-d-old rats. These results suggest that different neural processes mediate extinction early in development. However, the neural processes underlying extinction in the developing rat are unknown. Therefore, the present study investigated amygdala involvement in extinction and reextinction during development. In experiment 1, temporary inactivation of the amygdala (using bupivacaine, a sodium channel modulator) during extinction training impaired extinction of conditioned fear in 17- and 24-d-old rats. In experiment 2, 17- and 24-d-old rats were conditioned, extinguished, and then reconditioned to the same CS. After reconditioning, the CS was reextinguished; at this time, some rats at each age had their amygdala temporarily inactivated. Reextinction was amygdala independent in 24-d-old rats, as previously shown in adult rats. However, reextinction was still amygdala dependent in 17-d-old rats. In Experiment 3, the age at conditioning, reconditioning, reextinction, and test was held constant, but the age of initial extinction varied across groups; reextinction was found to be amygdala independent if initial extinction occurred at 24 d of age but amygdala dependent if it occurred at 17 d of age. Consistent with previous findings, these results show that there are fundamental differences in the neural mechanisms of fear extinction across development. PMID:18256248

  8. Extinction under a Behavioral Microscope: Isolating the Sources of Decline in Operant Response Rate

    PubMed Central

    Cheung, Timothy H C; Neisewander, Janet L; Sanabria, Federico

    2012-01-01

    Extinction performance is often used to assess underlying psychological processes without the interference of reinforcement. For example, in the extinction/reinstatement paradigm, motivation to seek drug is assessed by measuring responding elicited by drug-associated cues without drug reinforcement. Nonetheless, extinction performance is governed by several psychological processes that involve motivation, memory, learning, and motoric functions. These processes are confounded when overall response rate is used to measure performance. Based on evidence that operant responding occurs in bouts, this paper proposes an analytic procedure that separates extinction performance into several behavioral components: 1) the baseline bout initiation rate, within-bout response rate, and bout length at the onset of extinction; 2) their rates of decay during extinction; 3) the time between extinction onset and the decline of responding; 4) the asymptotic response rate at the end of extinction; 5) the refractory period after each response. Data that illustrate the goodness of fit of this analytic model are presented. This paper also describes procedures to 1) isolate behavioral components contributing to extinction performance; 2) make inferences about experimental effects on these components. This microscopic behavioral analysis allows the mapping of different psychological processes to distinct behavioral components implicated in extinction performance, which may further our understanding of the psychological effects of neurobiological treatments. PMID:22425782

  9. The extinction of morphine-induced conditioned place preference by histone deacetylase inhibition.

    PubMed

    Wang, Ru; Zhang, Yan; Qing, Hua; Liu, Mei; Yang, Peng

    2010-10-11

    Recent evidence suggests that epigenetic mechanisms have an important role in the development of addictive behavior. However, little is known about the role of epigenetic mechanisms in the extinction of morphine-induced behavioral changes. In this study, we will examine the effect of histone deacetylase (HDAC) inhibitors on extinction of morphine-induced conditioned place preference (CPP). To facilitate extinction, rats will be administered an HDAC inhibitor (HDACi) following nonreinforced exposure to the conditioned context. To measure persistence, rats were subject to a reinstatement test using 3 mg/kg dose of morphine. To exclude the effect of repeated NaBut injections themselves on morphine-CPP in the absence of extinction session, rats received injection of either NaBut or vehicle for 8 days. We found that HDAC inhibition during nonconfined extinction or confined extinction consolidation can facilitate extinction of morphine-induced CPP. We also showed that the extinction of drug seeking via HDAC inhibition modulates extinction learning such that reinstatement behavior is significantly attenuated. There is no effect of repeated NaBut injections themselves on morphine-CPP in the absence of extinction session. In conclusion, our results extend earlier reports on the ability of HDACi to modify the behavioral effects of drugs of abuse. Our increasing understanding of these epigenetic mechanisms will provide key answers to basic processes in drug addiction and hopefully provide insight into designing improved treatments for drug addiction. PMID:20691756

  10. Investigation of ultraviolet interstellar extinction

    NASA Technical Reports Server (NTRS)

    Payne, C.; Haramundanis, K. L.

    1973-01-01

    Results concerning interstellar extinction in the ultraviolet are reported. These results were initially obtained by using data from main-sequence stars and were extended to include supergiants and emission stars. The principal finding of the analysis of ultraviolet extinction is not only that it is wavelength dependent, but that if changes with galactic longitude in the U3 passband (lambda sub eff = 1621 A); it does not change significantly in the U2 passband (lambda sub eff = 2308 A). Where data are available in the U4 passband (lambda sub eff = 1537 A), they confirm the rapid rise of extinction in the ultraviolet found by other investigators. However, in all cases, emission stars must be used with great caution. It is important to realize that while extinction continues to rise toward shorter wavelengths in the ultraviolet, including the shortest ultraviolet wavelengths measured (1100 A), it no longer plays an important role in the X-ray region (50 A).

  11. What Caused the Mass Extinction?

    ERIC Educational Resources Information Center

    Alvarez, Walter; And Others

    1990-01-01

    Presented are the arguments of two different points of view on the mass extinction of the dinosaurs. Evidence of extraterrestrial impact theory and massive volcanic eruption theory are discussed. (CW)

  12. The Sixth Great Mass Extinction

    ERIC Educational Resources Information Center

    Wagler, Ron

    2012-01-01

    Five past great mass extinctions have occurred during Earth's history. Humanity is currently in the midst of a sixth, human-induced great mass extinction of plant and animal life (e.g., Alroy 2008; Jackson 2008; Lewis 2006; McDaniel and Borton 2002; Rockstrom et al. 2009; Rohr et al. 2008; Steffen, Crutzen, and McNeill 2007; Thomas et al. 2004;…

  13. Series cell light extinction monitor

    DOEpatents

    Novick, Vincent J.

    1990-01-01

    A method and apparatus for using the light extinction measurements from two or more light cells positioned along a gasflow chamber in which the gas volumetric rate is known to determine particle number concentration and mass concentration of an aerosol independent of extinction coefficient and to determine estimates for particle size and mass concentrations. The invention is independent of particle size. This invention has application to measurements made during a severe nuclear reactor fuel damage test.

  14. Magnetic reversals and mass extinctions

    NASA Technical Reports Server (NTRS)

    Raup, D. M.

    1985-01-01

    The results of a study of reversals of the earth's magnetic field over the past 165 Myr are presented. A stationary periodicity of 30 Myr emerges which predicts pulses of increased reversal activity centered at 10, 40, 70, . . . Myr before the present. The correlation between the reversal intensity and biological extinctions is examined, and a nontrivial discrepancy is found between the magnetic and extinction periodicity.

  15. To leave or not to leave.

    PubMed

    Buchan, James

    2016-06-22

    Lies, damned lies and Brexit statistics. It's not been a good month for anyone espousing evidence-based policy and politics after the chair of the Commons health committee switched from Leave to Remain, citing misuse of data by the Leave campaign. PMID:27332589

  16. Extinction, Relapse, and Behavioral Momentum

    PubMed Central

    Podlesnik, Christopher A.; Shahan, Timothy A.

    2010-01-01

    Previous experiments on behavioral momentum have shown that relative resistance to extinction of operant behavior in the presence of a discriminative stimulus depends upon the baseline rate or magnitude of reinforcement associated with that stimulus (i.e., the Pavlovian stimulus-reinforcer relation). Recently, we have shown that relapse of operant behavior in reinstatement, resurgence, and context renewal preparations also is a function of baseline stimulus-reinforcer relations. In this paper we present new data examining the role of baseline stimulus-reinforcer relations on resistance to extinction and relapse using a variety of baseline training conditions and relapse operations. Furthermore, we evaluate the adequacy of a behavioral-momentum based model in accounting for the results. The model suggests that relapse occurs as a result of a decrease in the disruptive impact of extinction precipitated by a change in circumstances associated with extinction, and that the degree of relapse is a function of the pre-extinction baseline Pavlovian stimulus-reinforcer relation. Across experiments, relative resistance to extinction and relapse were greater in the presence of stimuli associated with more favorable conditions of reinforcement and were positively related to one another. In addition, the model did a good job in accounting for these effects. Thus, behavioral momentum theory may provide a useful quantitative approach for characterizing how differential reinforcement conditions contribute to relapse of operant behavior. PMID:20152889

  17. Extinction, relapse, and behavioral momentum.

    PubMed

    Podlesnik, Christopher A; Shahan, Timothy A

    2010-05-01

    Previous experiments on behavioral momentum have shown that relative resistance to extinction of operant behavior in the presence of a discriminative stimulus depends upon the baseline rate or magnitude of reinforcement associated with that stimulus (i.e., the Pavlovian stimulus-reinforcer relation). Recently, we have shown that relapse of operant behavior in reinstatement, resurgence, and context renewal preparations also is a function of baseline stimulus-reinforcer relations. In this paper we present new data examining the role of baseline stimulus-reinforcer relations on resistance to extinction and relapse using a variety of baseline training conditions and relapse operations. Furthermore, we evaluate the adequacy of a behavioral momentum based model in accounting for the results. The model suggests that relapse occurs as a result of a decrease in the disruptive impact of extinction precipitated by a change in circumstances associated with extinction, and that the degree of relapse is a function of the pre-extinction baseline Pavlovian stimulus-reinforcer relation. Across experiments, relative resistance to extinction and relapse were greater in the presence of stimuli associated with more favorable conditions of reinforcement and were positively related to one another. In addition, the model did a good job in accounting for these effects. Thus, behavioral momentum theory may provide a useful quantitative approach for characterizing how differential reinforcement conditions contribute to relapse of operant behavior. PMID:20152889

  18. Extinction and the associative structure of heterogeneous instrumental chains.

    PubMed

    Thrailkill, Eric A; Bouton, Mark E

    2016-09-01

    Drug abuse, overeating, and smoking are all examples of instrumental behaviors that often involve chains or sequences of behavior. A behavior chain is minimally composed of a procurement response that is required in order for a subsequent consumption response to be reinforced. Despite the translational importance of behavior chains, few studies have attempted to understand what binds them together and takes them apart. This article surveys the development of the heterogeneous instrumental chain method and introduces recent findings that have used extinction to analyze the associative content of (what is learned in) the chain. Chained responses that are occasion-set by their own discriminative stimuli may be directly associated; extinction of the procurement response weakens its associated consumption response, and extinction of the consumption response weakens its associated procurement response. Extinction itself involves learning to inhibit the response. Extinguished chained responses are subject to renewal when they are tested either back in the acquisition context or in a new context. In addition, a consumption response that is extinguished outside its chain is renewed when returned to the context of the preceding response in the chain. Research on heterogeneous behavior chains can provide important insights into an important but often overlooked aspect of instrumental learning. PMID:27296700

  19. Contextual Change After Fear Acquisition Affects Conditioned Responding and the Time Course of Extinction Learning—Implications for Renewal Research

    PubMed Central

    Sjouwerman, Rachel; Niehaus, Johanna; Lonsdorf, Tina B.

    2015-01-01

    Context plays a central role in retrieving (fear) memories. Accordingly, context manipulations are inherent to most return of fear (ROF) paradigms (in particular renewal), involving contextual changes after fear extinction. Context changes are, however, also often embedded during earlier stages of ROF experiments such as context changes between fear acquisition and extinction (e.g., in ABC and ABA renewal). Previous studies using these paradigms have however focused exclusively on the context switch after extinction (i.e., renewal). Thus, the possibility of a general effect of context switch on conditioned responding that may not be conditional to preceding extinction learning remains unstudied. Hence, the current study investigated the impact of a context switch between fear acquisition and extinction on immediate conditioned responding and on the time-course of extinction learning by using a multimodal approach. A group that underwent contextual change after fear conditioning (AB; n = 36) was compared with a group without a contextual change from acquisition to extinction (AA; n = 149), while measuring physiological (skin conductance and fear potentiated startle) measures and subjective fear ratings. Contextual change between fear acquisition and extinction had a pronounced effect on both immediate conditioned responding and on the time course of extinction learning in skin conductance responses and subjective fear ratings. This may have important implications for the mechanisms underlying and the interpretation of the renewal effect (i.e., contextual switch after extinction). Consequently, future studies should incorporate designs and statistical tests that disentangle general effects of contextual change from genuine ROF effects. PMID:26696855

  20. Thermal Transgressions and Phanerozoic Extinctions

    NASA Astrophysics Data System (ADS)

    Worsley, T. R.; Kidder, D. L.

    2007-12-01

    A number of significant Phanerozoic extinctions are associated with marine transgressions that were probably driven by rapid ocean warming. The conditions associated with what we call thermal transgressions are extremely stressful to life on Earth. The Earth system setting associated with end-Permian extinction exemplifies an end-member case of our model. The conditions favoring extreme warmth and sea-level increases driven by thermal expansion are also conducive to changes in ocean circulation that foster widespread anoxia and sulfidic subsurface ocean waters. Equable climates are characterized by reduced wind shear and weak surface ocean circulation. Late Permian and Early Triassic thermohaline circulation differs considerably from today's world, with minimal polar sinking and intensified mid-latitude sinking that delivers sulfate from shallow evaporative areas to deeper water where it is reduced to sulfide. Reduced nutrient input to oceans from land at many of the extinction intervals results from diminished silicate weathering and weakened delivery of iron via eolian dust. The falloff in iron-bearing dust leads to minimal nitrate production, weakening food webs and rendering faunas and floras more susceptible to extinction when stressed. Factors such as heat, anoxia, ocean acidification, hypercapnia, and hydrogen sulfide poisoning would significantly affect these biotas. Intervals of tectonic quiescence set up preconditions favoring extinctions. Reductions in chemical silicate weathering lead to carbon dioxide buildup, oxygen drawdown, nutrient depletion, wind and ocean current abatement, long-term global warming, and ocean acidification. The effects of extinction triggers such as large igneous provinces, bolide impacts, and episodes of sudden methane release are more potent against the backdrop of our proposed preconditions. Extinctions that have characteristics we call for in the thermal transgressions include the Early Cambrian Sinsk event, as well as

  1. Yohimbine impairs extinction of cocaine-conditioned place preference in an alpha2-adrenergic receptor independent process.

    PubMed

    Davis, Adeola R; Shields, Angela D; Brigman, Jonathan L; Norcross, Maxine; McElligott, Zoe A; Holmes, Andrew; Winder, Danny G

    2008-09-01

    Extinction, a form of learning that has the ability to reshape learned behavior based on new experiences, has been heavily studied utilizing fear learning paradigms. Mechanisms underlying extinction of positive-valence associations, such as drug self-administration and place preference, are poorly understood yet may have important relevance to addiction treatment. Data suggest a major role for the noradrenergic system in extinction of fear-based learning. Employing both pharmacological and genetic approaches, we investigated the role of the alpha(2)-adrenergic receptor (alpha(2)-AR) in extinction of cocaine-conditioned place preference (CPP) and glutamatergic transmission in the bed nucleus of the stria terminalis (BNST). We found that pre-extinction systemic treatment with the alpha(2)-AR antagonist yohimbine impaired cocaine CPP extinction in C57BL/6J mice, an effect that was not mimicked by the more selective alpha(2)-AR antagonist, atipamezole. Moreover, alpha(2A)-AR knockout mice exhibited similar cocaine CPP extinction and exacerbated extinction impairing effects of yohimbine. Using acute brain slices and electrophysiological approaches, we found that yohimbine produces a slowly evolving depression of glutamatergic transmission in the BNST that was not mimicked by atipamezole. Further, this action was extant in slices from alpha(2A)-AR knockout mice. Our data strongly suggest that extinction-modifying effects of yohimbine are unlikely to be due to actions at alpha(2A)-ARs. PMID:18772254

  2. Study Leave in Sweden.

    ERIC Educational Resources Information Center

    Gould, Arthur

    2003-01-01

    Analysis of statistics since 1994 on the use of study leave as allowed by a 1974 Swedish law indicates that about 1% of the work force takes leave at any time. Women and manual workers benefit more than men and salaried workers. Leave application causes employees few problems with employers but financial assistance is a concern. (Contains 37…

  3. Biostratigraphic case studies of six major extinctions

    NASA Technical Reports Server (NTRS)

    Sloan, R. E.

    1988-01-01

    Biostratigraphic case studies of six major extinctions show all are gradual save one, which is a catastrophic extinction of terrestrial origin. These extinctions show a continuum of environmental insults from major to minor. The major causes of these extinctions are positive and negative eustatic sea level changes, temperature, or ecological competition. Extraterrestrial causes should not be posited without positive association with a stratigraphically sharp extinction. The Cretaceous-Tertiary terrestrial extinction is considerably smaller in percentage of extinction than the marine extinction and is spread over 10 my of the Cretaceous and 1 my of the Tertiary. Sixty percent of the 30 dinosaurs in the northern Great Plains of the U.S. and Canada had become extinct in the 9 my before the late Maastrichtian sea level drop. The best data on the Permo-Triassic terrestrial extinction are from the Karoo basin of South Africa. This is a series of 6 extinctions in some 8 my, recorded in some 2800 meters of sediment. Precision of dating is enhanced by the high rate of accumulation of these sediments. Few data are readily available on the timing of the marine Permo-Triassic extinction, due to the very restricted number of sequences of Tatarian marine rocks. The terminal Ordovician extinction at 438 my is relatively rapid, taking place over about 0.5 my. The most significant aspect of this extinction is a eustatic sea level lowering associated with a major episode of glaciation. New data on this extinction is the reduction from 61 genera of trilobites in North America to 14, for a 77 percent extinction. Another Ordovician extinction present over 10 percent of the North American craton occurs at 454 my in the form of a catastrophic extinction due to a volcanic eruption which blanketed the U.S. east of the Transcontinental Arch. This is the only other sizeable extinction in the Ordovician.

  4. Interstellar Extinction Toward Young Stars

    NASA Astrophysics Data System (ADS)

    McJunkin, Matthew; France, Kevin

    2015-01-01

    We present work on a molecular hydrogen (H2) fluorescence model to characterize the ultraviolet (UV) extinction curve along the line of sight towards young stars with circumstellar disks. Stellar UV radiation plays a strong role in heating the disk gas and driving chemical reactions, so it is important to measure the UV extinction curve in order to reconstruct the intrinsic stellar UV flux impacting the disk. To measure the extinction, we compare modeled H2 fluorescence spectra to observed H2 lines. Lyman-alpha radiation from the stars pumps electronic transitions of H2 in the disk, and we model the flux that is re-emitted through the subsequent fluorescent cascade. We then extract the extinction along the line-of-sight over the 1100-1700 Angstrom wavelength region from the difference between the modeled H2 fluorescence and the HST-COS data. The shape of the extinction curve allows us to characterize the dust grain distribution in the intervening material as well as to recover the intrinsic spectral energy distribution of the stars over a wide wavelength range.

  5. The extinction of the dinosaurs.

    PubMed

    Brusatte, Stephen L; Butler, Richard J; Barrett, Paul M; Carrano, Matthew T; Evans, David C; Lloyd, Graeme T; Mannion, Philip D; Norell, Mark A; Peppe, Daniel J; Upchurch, Paul; Williamson, Thomas E

    2015-05-01

    Non-avian dinosaurs went extinct 66 million years ago, geologically coincident with the impact of a large bolide (comet or asteroid) during an interval of massive volcanic eruptions and changes in temperature and sea level. There has long been fervent debate about how these events affected dinosaurs. We review a wealth of new data accumulated over the past two decades, provide updated and novel analyses of long-term dinosaur diversity trends during the latest Cretaceous, and discuss an emerging consensus on the extinction's tempo and causes. Little support exists for a global, long-term decline across non-avian dinosaur diversity prior to their extinction at the end of the Cretaceous. However, restructuring of latest Cretaceous dinosaur faunas in North America led to reduced diversity of large-bodied herbivores, perhaps making communities more susceptible to cascading extinctions. The abruptness of the dinosaur extinction suggests a key role for the bolide impact, although the coarseness of the fossil record makes testing the effects of Deccan volcanism difficult. PMID:25065505

  6. Flood basalts and extinction events

    NASA Technical Reports Server (NTRS)

    Stothers, Richard B.

    1993-01-01

    The largest known effusive eruptions during the Cenozoic and Mesozoic Eras, the voluminous flood basalts, have long been suspected as being associated with major extinctions of biotic species. Despite the possible errors attached to the dates in both time series of events, the significance level of the suspected correlation is found here to be 1 percent to 4 percent. Statistically, extinctions lag eruptions by a mean time interval that is indistinguishable from zero, being much less than the average residual derived from the correlation analysis. Oceanic flood basalts, however, must have had a different biological impact, which is still uncertain owing to the small number of known examples and differing physical factors. Although not all continental flood basalts can have produced major extinction events, the noncorrelating eruptions may have led to smaller marine extinction events that terminated at least some of the less catastrophically ending geologic stages. Consequently, the 26 Myr quasi-periodicity seen in major marine extinctions may be only a sampling effect, rather than a manifestation of underlying periodicity.

  7. Flood basalts and mass extinctions

    NASA Technical Reports Server (NTRS)

    Morgan, W. Jason

    1988-01-01

    There appears to be a correlation between the times of flood basalts and mass-extinction events. There is a correlation of flood basalts and hotspot tracks--flood basalts appear to mark the beginning of a new hotspot. Perhaps there is an initial instability in the mantle that bursts forth as a flood basalt but then becomes a steady trickle that persists for many tens of millions of years. Suppose that flood basalts and not impacts cause the environmental changes that lead to mass-extinctions. This is a very testable hypothesis: it predicts that the ages of the flows should agree exactly with the times of extinctions. The Deccan and K-T ages agree with this hypothesis; An iridium anomaly at extinction boundaries apparently can be explained by a scaled-up eruption of the Hawaiian type; the occurrence of shocked-quartz is more of a problem. However if the flood basalts are all well dated and their ages indeed agree with extinction times, then surely some mechanism to appropriately produce shocked-quartz will be found.

  8. The Class I HDAC inhibitor RGFP963 enhances consolidation of cued fear extinction

    PubMed Central

    Bowers, Mallory E.; Xia, Bing; Carreiro, Samantha

    2015-01-01

    Evidence indicates that broad, nonspecific histone deacetylase (HDAC) inhibition enhances learning and memory, however, the contribution of the various HDACs to specific forms of learning is incompletely understood. Here, we show that the Class I HDAC inhibitor, RGFP963, enhances consolidation of cued fear extinction. However, RGFP966, a strong inhibitor of HDAC3, does not significantly enhance consolidation of cued fear extinction. These data extend previous evidence that demonstrate the Class I HDACs play a role in the consolidation of long-term memory, suggesting that HDAC1 and/or HDAC2, but less likely HDAC3, may function as negative regulators of extinction retention. The development of specific HDAC inhibitors, such as RGFP963, will further illuminate the role of specific HDACs in various types of learning and memory. Moreover, HDAC inhibitors that enhance cued fear extinction may show translational promise for the treatment of fear-related disorders, including post-traumatic stress disorder (PTSD). PMID:25776040

  9. The effects of transcutaneous vagus nerve stimulation on conditioned fear extinction in humans.

    PubMed

    Burger, Andreas M; Verkuil, Bart; Van Diest, Ilse; Van der Does, Willem; Thayer, Julian F; Brosschot, Jos F

    2016-07-01

    A critical component of the treatment for anxiety disorders is the extinction of fear via repeated exposure to the feared stimulus. This process is strongly dependent on successful memory formation and consolidation. Stimulation of the vagus nerve enhances memory formation in both animals and humans. The objective of this study was to assess whether transcutaneous stimulation of the vagus nerve (tVNS) can accelerate extinction memory formation and retention in fear conditioned humans. To assess fear conditioning and subsequent fear extinction, we assessed US expectancy ratings, fear potentiated startle responses and phasic heart rate responses. We conducted a randomized controlled trial in thirty-one healthy participants. After fear conditioning participants were randomly assigned to receive tVNS or sham stimulation during the extinction phase. Retention of extinction memory was tested 24h later. tVNS accelerated explicit fear extinction learning (US expectancy ratings), but did not lead to better retention of extinction memory 24h later. We did not find a differential physiological conditioning response during the acquisition of fear and thus were unable to assess potential effects of tVNS on the extinction of physiological indices of fear. These findings complement recent studies that suggest vagus nerve stimulation could be a promising tool to improve memory consolidation and fear extinction. PMID:27222436

  10. Infralimbic EphB2 Modulates Fear Extinction in Adolescent Rats

    PubMed Central

    Cruz, Emmanuel; Soler-Cedeño, Omar; Negrón, Geovanny; Criado-Marrero, Marangelie; Chompré, Gladys

    2015-01-01

    Adolescent rats are prone to impaired fear extinction, suggesting that mechanistic differences in extinction could exist in adolescent and adult rats. Since the infralimbic cortex (IL) is critical for fear extinction, we used PCR array technology to identify gene expression changes in IL induced by fear extinction in adolescent rats. Interestingly, the ephrin type B receptor 2 (EphB2), a tyrosine kinase receptor associated with synaptic development, was downregulated in IL after fear extinction. Consistent with the PCR array results, EphB2 levels of mRNA and protein were reduced in IL after fear extinction compared with fear conditioning, suggesting that EphB2 signaling in IL regulates fear extinction memory in adolescents. Finally, reducing EphB2 synthesis in IL with shRNA accelerated fear extinction learning in adolescent rats, but not in adult rats. These findings identify EphB2 in IL as a key regulator of fear extinction during adolescence, perhaps due to the increase in synaptic remodeling occurring during this developmental phase. PMID:26354908

  11. Infralimbic EphB2 Modulates Fear Extinction in Adolescent Rats.

    PubMed

    Cruz, Emmanuel; Soler-Cedeño, Omar; Negrón, Geovanny; Criado-Marrero, Marangelie; Chompré, Gladys; Porter, James T

    2015-09-01

    Adolescent rats are prone to impaired fear extinction, suggesting that mechanistic differences in extinction could exist in adolescent and adult rats. Since the infralimbic cortex (IL) is critical for fear extinction, we used PCR array technology to identify gene expression changes in IL induced by fear extinction in adolescent rats. Interestingly, the ephrin type B receptor 2 (EphB2), a tyrosine kinase receptor associated with synaptic development, was downregulated in IL after fear extinction. Consistent with the PCR array results, EphB2 levels of mRNA and protein were reduced in IL after fear extinction compared with fear conditioning, suggesting that EphB2 signaling in IL regulates fear extinction memory in adolescents. Finally, reducing EphB2 synthesis in IL with shRNA accelerated fear extinction learning in adolescent rats, but not in adult rats. These findings identify EphB2 in IL as a key regulator of fear extinction during adolescence, perhaps due to the increase in synaptic remodeling occurring during this developmental phase. PMID:26354908

  12. Rapid eye movement sleep deprivation selectively impairs recall of fear extinction in hippocampus-independent tasks in rats.

    PubMed

    Fu, J; Li, P; Ouyang, X; Gu, C; Song, Z; Gao, J; Han, L; Feng, S; Tian, S; Hu, B

    2007-02-23

    Previous studies have shown that rapid eye movement (REM) sleep deprivation (RSD) exerts a detrimental effect on some memory tasks. However, whether post-learning RSD impairs memory for fear extinction, an important model of inhibitory learning, remains to be elucidated. The present study examined the effects of post-extinction RSD from 0 to 6 h and 6 to 12 h on recall of fear extinction tested 24 h after extinction training. We found that RSD from 0 to 6 h significantly increased freezing when recall of extinction of cued fear was tested in the context in which rats received extinction training whereas RSD from 6 to 12 h had no effect (experiments 1 and 2, two hippocampus-independent memory tasks). RSD at either time point had no effect on freezing when recall of extinction of cued fear was tested in the context different from that in which extinction training occurred (experiment 3, a hippocampus-dependent memory task). Additionally, we observed no effect of RSD at either time point on freezing during recall test for extinction of contextual fear (experiment 4, a hippocampus-dependent memory task). These results suggest that the effects of post-extinction RSD on memory for fear extinction are complex. RSD impairs recall of fear extinction in hippocampus-independent tasks, but does not affect recall of fear extinction in hippocampus-dependent tasks. Our findings extend previous research on the effects of RSD on learning and memory and support the notion that REM sleep is involved in memory process of certain tasks. PMID:17157993

  13. Retrieval and Reconsolidation Accounts of Fear Extinction

    PubMed Central

    Ponnusamy, Ravikumar; Zhuravka, Irina; Poulos, Andrew M.; Shobe, Justin; Merjanian, Michael; Huang, Jeannie; Wolvek, David; O’Neill, Pia-Kelsey; Fanselow, Michael S.

    2016-01-01

    Extinction is the primary mode for the treatment of anxiety disorders. However, extinction memories are prone to relapse. For example, fear is likely to return when a prolonged time period intervenes between extinction and a subsequent encounter with the fear-provoking stimulus (spontaneous recovery). Therefore there is considerable interest in the development of procedures that strengthen extinction and to prevent such recovery of fear. We contrasted two procedures in rats that have been reported to cause such deepened extinction. One where extinction begins before the initial consolidation of fear memory begins (immediate extinction) and another where extinction begins after a brief exposure to the consolidated fear stimulus. The latter is thought to open a period of memory vulnerability similar to that which occurs during initial consolidation (reconsolidation update). We also included a standard extinction treatment and a control procedure that reversed the brief exposure and extinction phases. Spontaneous recovery was only found with the standard extinction treatment. In a separate experiment we tested fear shortly after extinction (i.e., within 6 h). All extinction procedures, except reconsolidation update reduced fear at this short-term test. The findings suggest that strengthened extinction can result from alteration in both retrieval and consolidation processes. PMID:27242459

  14. How partial reinforcement of food cues affects the extinction and reacquisition of appetitive responses. A new model for dieting success?

    PubMed

    van den Akker, Karolien; Havermans, Remco C; Bouton, Mark E; Jansen, Anita

    2014-10-01

    Animals and humans can easily learn to associate an initially neutral cue with food intake through classical conditioning, but extinction of learned appetitive responses can be more difficult. Intermittent or partial reinforcement of food cues causes especially persistent behaviour in animals: after exposure to such learning schedules, the decline in responding that occurs during extinction is slow. After extinction, increases in responding with renewed reinforcement of food cues (reacquisition) might be less rapid after acquisition with partial reinforcement. In humans, it may be that the eating behaviour of some individuals resembles partial reinforcement schedules to a greater extent, possibly affecting dieting success by interacting with extinction and reacquisition. Furthermore, impulsivity has been associated with less successful dieting, and this association might be explained by impulsivity affecting the learning and extinction of appetitive responses. In the present two studies, the effects of different reinforcement schedules and impulsivity on the acquisition, extinction, and reacquisition of appetitive responses were investigated in a conditioning paradigm involving food rewards in healthy humans. Overall, the results indicate both partial reinforcement schedules and, possibly, impulsivity to be associated with worse extinction performance. A new model of dieting success is proposed: learning histories and, perhaps, certain personality traits (impulsivity) can interfere with the extinction and reacquisition of appetitive responses to food cues and they may be causally related to unsuccessful dieting. PMID:24973507

  15. Infectious disease, endangerment, and extinction.

    PubMed

    Macphee, Ross D E; Greenwood, Alex D

    2013-01-01

    Infectious disease, especially virulent infectious disease, is commonly regarded as a cause of fluctuation or decline in biological populations. However, it is not generally considered as a primary factor in causing the actual endangerment or extinction of species. We review here the known historical examples in which disease has, or has been assumed to have had, a major deleterious impact on animal species, including extinction, and highlight some recent cases in which disease is the chief suspect in causing the outright endangerment of particular species. We conclude that the role of disease in historical extinctions at the population or species level may have been underestimated. Recent methodological breakthroughs may lead to a better understanding of the past and present roles of infectious disease in influencing population fitness and other parameters. PMID:23401844

  16. Speeding up spontaneous disease extinction

    NASA Astrophysics Data System (ADS)

    Khasin, Michael

    2012-02-01

    The dynamics of epidemic in a susceptible population is affected both by the random character of interactions between the individuals and by environmental variations. As a consequence, the sizes of the population groups (infected, susceptible, etc.) fluctuate in the course of evolution of the epidemic. In a small community a rare large fluctuation in the number of infected can result in extinction of the disease. We suggest a novel paradigm of controlling the epidemic, where the control field, such as vaccination, is designed to maximize the rate of spontaneous disease extinction. We show that, for a limited-scope vaccination, the optimal vaccination protocol and its impact on the epidemics have universal features: (i) the vaccine must be applied in pulses, (ii) the spontaneous disease extinction is synchronized with the vaccination. We trace this universality to general properties of the response of large fluctuations to external perturbations.

  17. Infectious Disease, Endangerment, and Extinction

    PubMed Central

    MacPhee, Ross D. E.; Greenwood, Alex D.

    2013-01-01

    Infectious disease, especially virulent infectious disease, is commonly regarded as a cause of fluctuation or decline in biological populations. However, it is not generally considered as a primary factor in causing the actual endangerment or extinction of species. We review here the known historical examples in which disease has, or has been assumed to have had, a major deleterious impact on animal species, including extinction, and highlight some recent cases in which disease is the chief suspect in causing the outright endangerment of particular species. We conclude that the role of disease in historical extinctions at the population or species level may have been underestimated. Recent methodological breakthroughs may lead to a better understanding of the past and present roles of infectious disease in influencing population fitness and other parameters. PMID:23401844

  18. The atmospheric extinction of light

    NASA Astrophysics Data System (ADS)

    Hughes, Stephen W.; Cowley, Michael; Powell, Sean; Carroll, Joshua

    2016-01-01

    An experiment is described that enables students to understand the properties of atmospheric extinction due to Rayleigh scattering. The experiment requires the use of red, green and blue lasers attached to a travelling microscope or similar device. The laser beams are passed through an artificial atmosphere, made from milky water, at varying depths, before impinging on either a light meter or a photodiode integral to a Picotech Dr. DAQ ADC. A plot of measured spectral intensity verses depth reveals the contribution Rayleigh scattering has to the extinction coefficient. For the experiment with the light meter, the extinction coefficients for red, green and blue light in the milky sample of water were 0.27, 0.36 and 0.47 cm-1 respectively and 0.032, 0.037 and 0.092 cm-1 for the Picotech Dr. DAQ ADC.

  19. ALE: Astronomical LIDAR for Extinction

    NASA Astrophysics Data System (ADS)

    Zimmer, Peter C.; McGraw, J. T.; Gimmestad, G.; Roberts, D.; Stewart, J.; Dawsey, M.; Fitch, J.; Smith, J.; Townsend, A.; Black, B.

    2006-12-01

    The primary impediment to precision all-sky photometry is the scattering or absorption of incoming starlight by the aerosols suspended in, and the molecules of, the Earth's atmosphere. The University of New Mexico (UNM) and the Georgia Tech Research Institute (GTRI) are currently developing the Astronomical LIDAR (LIght Detection And Ranging) for Extinction (ALE), which is undergoing final integration and initial calibration at UNM. ALE is based upon a 527nm laser operated at a pulse repetition rate of 1500 pps, and rendered eyesafe by expanding its beam through a 32cm diameter transmitter. The alt-az mounted ALE will operate in multiple modes, including mapping the sky to obtain a quantitative measurement of extinction sources, measuring a monochromatic extinction coefficient by producing Langely plots, and monitoring extinction in the direction in which a telescope is observing. A primary goal is to use the Rayleigh scattered LIDAR return from air above 20km as a quasi-constant illumination source. Air above this altitude is generally free from aerosols and the variations in density are relatively constant over intervals of a few minutes. When measured at several zenith angles, the integrated line-of-sight extinction can be obtained from a simple model fit of these returns. The 69 microjoule exit pulse power and 0.6m aperture receiver will allow ALE to collect approximately one million photons per minute from above 20km, enough to enable measurements of the monochromatic vertical extinction to better than 1% under photometric conditions. Along the way, ALE will also provide a plethora of additional information about the vertical and horizontal distributions of low-lying aerosols, dust or smoke in the free troposphere, and high cirrus, as well as detect the passage of boundary layer atmospheric gravity waves. This project is funded by NSF Grant 0421087.

  20. The galactic cycle of extinction

    NASA Astrophysics Data System (ADS)

    Gillman, Michael; Erenler, Hilary

    2008-01-01

    Global extinction and geological events have previously been linked with galactic events such as spiral arm crossings and galactic plane oscillation. The expectation that these are repeating predictable events has led to studies of periodicity in a wide set of biological, geological and climatic phenomena. Using data on carbon isotope excursions, large igneous provinces and impact craters, we identify three time zones of high geological activity which relate to the timings of the passage of the Solar System through the spiral arms. These zones are shown to include a significantly large proportion of high extinction periods. The mass extinction events at the ends of the Ordovician, Permian and Cretaceous occur in the first zone, which contains the predicted midpoints of the spiral arms. The start of the Cambrian, end of the Devonian and end of the Triassic occur in the second zone. The pattern of extinction timing in relation to spiral arm structure is supported by the positions of the superchrons and the predicted speed of the spiral arms. The passage times through an arm are simple multiples of published results on impact and fossil record periodicity and galactic plane half-periods. The total estimated passage time through four arms is 703.8 Myr. The repetition of extinction events at the same points in different spiral arm crossings suggests a common underlying galactic cause of mass extinctions, mediated through galactic effects on geological, solar and extra-solar processes. The two largest impact craters (Sudbury and Vredefort), predicted to have occurred during the early part of the first zone, extend the possible pattern to more than 2000 million years ago.

  1. Evidence for recovery of fear following immediate extinction in rats and humans

    PubMed Central

    Schiller, Daniela; Cain, Christopher K.; Curley, Nina G.; Schwartz, Jennifer S.; Stern, Sarah A.; LeDoux, Joseph E.; Phelps, Elizabeth A.

    2008-01-01

    Fear responses can be eliminated through extinction, a procedure involving the presentation of fear-eliciting stimuli without aversive outcomes. Extinction is believed to be mediated by new inhibitory learning that acts to suppress fear expression without erasing the original memory trace. This hypothesis is supported mainly by behavioral data demonstrating that fear can recover following extinction. However, a recent report by Myers and coworkers suggests that extinction conducted immediately after fear learning may erase or prevent the consolidation of the fear memory trace. Since extinction is a major component of nearly all behavioral therapies for human fear disorders, this finding supports the notion that therapeutic intervention beginning very soon after a traumatic event will be more efficacious. Given the importance of this issue, and the controversy regarding immediate versus delayed therapeutic interventions, we examined two fear recovery phenomena in both rats and humans: spontaneous recovery (SR) and reinstatement. We found evidence for SR and reinstatement in both rats and humans even when extinction was conducted immediately after fear learning. Thus, our data do not support the hypothesis that immediate extinction erases the original memory trace, nor do they suggest that a close temporal proximity of therapeutic intervention to the traumatic event might be advantageous. PMID:18509113

  2. Extinction risk of soil biota.

    PubMed

    Veresoglou, Stavros D; Halley, John M; Rillig, Matthias C

    2015-01-01

    No species lives on earth forever. Knowing when and why species go extinct is crucial for a complete understanding of the consequences of anthropogenic activity, and its impact on ecosystem functioning. Even though soil biota play a key role in maintaining the functioning of ecosystems, the vast majority of existing studies focus on aboveground organisms. Many questions about the fate of belowground organisms remain open, so the combined effort of theorists and applied ecologists is needed in the ongoing development of soil extinction ecology. PMID:26593272

  3. Extinction risk of soil biota

    PubMed Central

    Veresoglou, Stavros D.; Halley, John M.; Rillig, Matthias C.

    2015-01-01

    No species lives on earth forever. Knowing when and why species go extinct is crucial for a complete understanding of the consequences of anthropogenic activity, and its impact on ecosystem functioning. Even though soil biota play a key role in maintaining the functioning of ecosystems, the vast majority of existing studies focus on aboveground organisms. Many questions about the fate of belowground organisms remain open, so the combined effort of theorists and applied ecologists is needed in the ongoing development of soil extinction ecology. PMID:26593272

  4. Star formation and extinct radioactivities

    NASA Technical Reports Server (NTRS)

    Cameron, A. G. W.

    1984-01-01

    An assessment is made of the evidence for the existence of now-extinct radioactivities in primitive solar system material, giving attention to implications for the early stages of sun and solar system formation. The characteristics of possible disturbances in dense molecular clouds which can initiate the formation of cloud cores is discussed, with emphasis on these disturbances able to generate fresh radioactivities. A one-solar mass red giant star on the asymptotic giant branch appears to have been the best candidate to account for the short-lived extinct radioactivities in the early solar system.

  5. Endangered and Extinct Radioactivity

    NASA Astrophysics Data System (ADS)

    Leising, M. D.

    1993-07-01

    Gamma ray spectroscopy holds great promise for probing nucleosynthesis in individual nucleosynthesis events, via observations of short-lived radioactivity, and for measuring global galactic nucleosynthesis today with detections of longer-lived radioactivity. Many of the astrophysical issues addressed by these observations are precisely those that must be understood in order to interpret observations of extinct radioactivity in meteorites. It was somewhat surprising that the former case was realized first for a Type II supernova, when both 56Co [1] and 57Co [2] were detected in SN 1987A. These provide unprecedented constraints on models of Type II explosions. Live 26Al in the galaxy might come from Type II supernovae and their progenitors, and if this is eventually shown to be the case, can constrain massive star evolution, supernova nucleosynthesis, the galactic Type II supernova rate, and even models of the chemical evolution of the galaxy [3]. Titanium-44 is produced primarily in the alpha-rich freezeout from nuclear statistical equilibrium, possibly in Type Ia [4] and almost certainly in Type II supernovae [5]. The galactic recurrence time of these events is comparable to the 44Ti lifetime, so we expect to be able to see at most a few otherwise unseen 44Ti remnants at any given time. No such remnants have been detected yet [6]. Very simple arguments lead to the expectation that about 4 x 10^-4 M(sub)solar mass of 44Ca are produced per century. The product of the supernova frequency times the 44Ti yield per event must equal this number. Even assuming that only the latest event would be seen, rates in excess of 2 century^-1 are ruled out at >=99% confidence by the gamma ray limits. Only rates less than 0.3 century^-1 are acceptable at >5% confidence, and this means that the yield per event must be >10^-3 M(sub)solar mass to produce the requisite 44Ca. Rates this low are incompatible with current estimates for Type II supernovae and yields this high are also very

  6. Modelling anomalous extinction using nanodiamonds

    NASA Astrophysics Data System (ADS)

    Rai, Rakesh K.; Rastogi, Shantanu

    2012-07-01

    The modelling of extinction along anomalous/non-Cardelli, Clayton & Mathis sightlines, which are characterized by a broad 217.5-nm bump and steep far-ultraviolet (FUV) rise, is reported. The extinction along these sightlines, namely HD 210121, HD 204827, HD 29647 and HD 62542, is difficult to reproduce using standard silicate and graphite grains. A very good match with the observed extinction is obtained by considering a nanodiamond component as part of the carbonaceous matter. Most of these sightlines are rich in carbon and are invariably backed by a young hot stellar object. Nanodiamond is taken as a core within amorphous carbon and graphite. These core-mantle particles, taken as additional components along with graphite and silicates, lead to a reduction in the silicate requirement. The abundance of carbonaceous matter is not affected, as a very small fraction of nanodiamond is required. Extinction along sightlines that show steep FUV is also reported, demonstrating the importance of the nanodiamond component in all such regions.

  7. Modeling Population Growth and Extinction

    ERIC Educational Resources Information Center

    Gordon, Sheldon P.

    2009-01-01

    The exponential growth model and the logistic model typically introduced in the mathematics curriculum presume that a population grows exclusively. In reality, species can also die out and more sophisticated models that take the possibility of extinction into account are needed. In this article, two extensions of the logistic model are considered,…

  8. Noradrenergic blockade stabilizes prefrontal activity and enables fear extinction under stress

    PubMed Central

    Fitzgerald, Paul J.; Giustino, Thomas F.; Seemann, Jocelyn R.; Maren, Stephen

    2015-01-01

    Stress-induced impairments in extinction learning are believed to sustain posttraumatic stress disorder (PTSD). Noradrenergic signaling may contribute to extinction impairments by modulating medial prefrontal cortex (mPFC) circuits involved in fear regulation. Here we demonstrate that aversive fear conditioning rapidly and persistently alters spontaneous single-unit activity in the prelimbic and infralimbic subdivisions of the mPFC in behaving rats. These conditioning-induced changes in mPFC firing were mitigated by systemic administration of propranolol (10 mg/kg, i.p.), a β-noradrenergic receptor antagonist. Moreover, propranolol administration dampened the stress-induced impairment in extinction observed when extinction training is delivered shortly after fear conditioning. These findings suggest that β-adrenoceptors mediate stress-induced changes in mPFC spike firing that contribute to extinction impairments. Propranolol may be a helpful adjunct to behavioral therapy for PTSD, particularly in patients who have recently experienced trauma. PMID:26124100

  9. The currency and tempo of extinction.

    PubMed

    Regan, H M; Lupia, R; Drinnan, A N; Burgman, M A

    2001-01-01

    This study examines estimates of extinction rates for the current purported biotic crisis and from the fossil record. Studies that compare current and geological extinctions sometimes use metrics that confound different sources of error and reflect different features of extinction processes. The per taxon extinction rate is a standard measure in paleontology that avoids some of the pitfalls of alternative approaches. Extinction rates reported in the conservation literature are rarely accompanied by measures of uncertainty, despite many elements of the calculations being subject to considerable error. We quantify some of the most important sources of uncertainty and carry them through the arithmetic of extinction rate calculations using fuzzy numbers. The results emphasize that estimates of current and future rates rely heavily on assumptions about the tempo of extinction and on extrapolations among taxa. Available data are unlikely to be useful in measuring magnitudes or trends in current extinction rates. PMID:18707231

  10. D-Cycloserine Does Not Facilitate Fear Extinction by Reducing Conditioned Stimulus Processing or Promoting Conditioned Inhibition to Contextual Cues

    ERIC Educational Resources Information Center

    Baker, Kathryn D.; McNally, Gavan P.; Richardson, Rick

    2012-01-01

    The NMDA receptor partial agonist d-cycloserine (DCS) enhances the extinction of learned fear in rats and exposure therapy in humans with anxiety disorders. Despite these benefits, little is known about the mechanisms by which DCS promotes the loss of fear. The present study examined whether DCS augments extinction retention (1) through reductions…

  11. The Geochemistry of Mass Extinction

    NASA Astrophysics Data System (ADS)

    Kump, L. R.

    2003-12-01

    The course of biological evolution is inextricably linked to that of the environment through an intricate network of feedbacks that span all scales of space and time. Disruptions to the environment have biological consequences, and vice versa. Fossils provide the prima facie evidence for biotic disruptions: catastrophic losses of global biodiversity at various times in the Phanerozoic. However, the forensic evidence for the causes and environmental consequences of these mass extinctions resides primarily in the geochemical composition of sedimentary rocks deposited during the extinction intervals. Thus, advancement in our understanding of mass extinctions requires detailed knowledge obtained from both paleontological and geochemical records.This chapter reviews the state of knowledge concerning the geochemistry of the "big five" extinctions of the Phanerozoic (e.g., Sepkoski, 1993): the Late Ordovician (Hirnantian; 440 Ma), the Late Devonian (an extended or multiple event with its apex at the Frasnian-Famennian (F-F) boundary; 367 Ma), the Permian-Triassic (P-Tr; 251 Ma), the Triassic-Jurassic (Tr-J; 200 Ma), and the Cretaceous-Tertiary (K-T; 65 Ma). The focus on the big five is a matter of convenience, as there is a continuum in extinction rates from "background" to "mass extinction." Although much of the literature on extinctions centers on the causes and extents of biodiversity loss, in recent years paleontologists have begun to focus on recoveries (see, e.g., Hart, 1996; Kirchner and Weil, 2000; Erwin, 2001 and references therein).To the extent that the duration of the recovery interval may reflect a slow relaxation of the environment from perturbation, analysis of the geochemical record of recovery is an integral part of this effort. In interpreting the geochemical and biological records of recovery, we need to maintain a clear distinction among the characteristics of the global biota: their biodiversity (affected by differences in origination and extinction

  12. A parametric analysis of factors affecting acquisition and extinction of contextual fear in C57BL/6 and DBA/2 mice

    PubMed Central

    Lattal, K. Matthew; Maughan, DeeAnna K.

    2012-01-01

    Behavioral analyses of genetically modified and inbred strains of mice have revealed neural systems and molecules that are involved in memory formation. Many of these studies have examined memories that form in contextual fear conditioning, in which an organism learns that a particular context signals the occurrence of a footshock. During fear extinction, nonreinforced exposure to the context results in the loss of the conditioned fear response. The study of extinction has been instrumental for behavioral and molecular theories of memory. However, many of the transgenic, knockout, and inbred strains of mice that have been widely studied in memory have behavioral deficits in contextual fear conditioning, which makes the study of extinction in these mice particularly challenging. Here we explore several strategies for studying extinction in C57BL/6 and DBA/2 mice, two strains known to differ in contextual fear conditioning. First, we attempt to equate performance prior to extinction through several extensive conditioning protocols. Second, we examine extinction in subsets of mice matched for initial levels of context conditioning. Third, we examine within-strain effects of variables known to affect extinction. Differences between the strains persisted across extensive conditioning and extinction protocols, but both strains were sensitive to session duration and context manipulations during extinction. We describe the implications of our results for behavioral and neurobiological approaches to extinction, and we examine the general challenges in studying extinction in subjects that differ in learning or performance prior to extinction. PMID:22465469

  13. Fear-potentiated Startle During Extinction is Associated with White Matter Microstructure and Functional Connectivity

    PubMed Central

    Fani, Negar; King, Tricia Z.; Brewster, Ryan; Srivastava, Amita; Stevens, Jennifer S.; Glover, Ebony; Norrholm, Seth D.; Bradley, Bekh; Ressler, Kerry J; Jovanovic, Tanja

    2015-01-01

    Background Extinction of conditioned fear is an associative learning process that involves communication among the hippocampus, medial prefrontal cortex, and amygdala. Strength of connectivity between the hippocampus and the anterior cingulate cortex (ACC), and between the amygdala and ventromedial prefrontal cortex (vmPFC), may influence fear-potentiated startle (FPS) responses during extinction. Specific white matter tracts, the cingulum and uncinate fasciculus (UF), serve as primary routes of communication for these areas. Our objective was to investigate associations between FPS during extinction and cingulum and UF connectivity. Method Diffusion tensor imaging (DTI) and probabilistic tractography analyses were used to examine cingulum and UF structural connectivity in 40 female African-Americans with psychological trauma exposure. FPS responses during fear conditioning and extinction were assessed via EMG of the right orbicularis oculi muscle. Secondarily, functional connectivity analyses were performed with the seed ROIs used for tractography. Results A significant negative association between cingulum microstructure and FPS during early extinction (r=−.42, p=.01) and late extinction (r=−.36, p=.03) was observed after accounting for the effects of age, trauma exposure, and psychopathology (posttraumatic stress disorder symptoms); this pattern was similar for early extinction and functional connectivity between these regions (p<.05corrected). No significant correlations were observed between FPS and UF microstructure. Conclusions These data indicate that structural integrity of the cingulum is directly associated with extinction learning and appears to influence functional connectivity between these regions. Decrements in cingulum microstructure may interfere with extinction learning, thereby increasing risk for the development of pathological anxiety. PMID:25522360

  14. Further Evidence of Auditory Extinction in Aphasia

    ERIC Educational Resources Information Center

    Marshall, Rebecca Shisler; Basilakos, Alexandra; Love-Myers, Kim

    2013-01-01

    Purpose: Preliminary research ( Shisler, 2005) suggests that auditory extinction in individuals with aphasia (IWA) may be connected to binding and attention. In this study, the authors expanded on previous findings on auditory extinction to determine the source of extinction deficits in IWA. Method: Seventeen IWA (M[subscript age] = 53.19 years)…

  15. From the neurobiology of extinction to improved clinical treatments.

    PubMed

    Morrison, Filomene G; Ressler, Kerry J

    2014-04-01

    The neural circuitry underlying the fear response is extremely well conserved across mammalian species, which has allowed for the rapid translation of research findings in rodent models of fear to therapeutic interventions in human populations. Many aspects of exposure-based psychotherapy treatments in humans, which are widely used in the treatment of PTSD, panic disorder, phobias, and other anxiety disorders, are closely paralleled by extinction training in rodent fear conditioning models. Here, we discuss how the neural circuitry of fear learning and extinction in rodent animal models may be used to understand the underlying neural circuitry of fear-related disorders, such as PTSD in humans. We examine the factors that contribute to the pathology and development of PTSD. Next, we will review how fear is measured in animal models using classical Pavlovian fear conditioning paradigms, as well as brain regions such as the amygdala, which are involved in the fear response across species. Finally, we highlight the following three systems involved in the extinction of fear, all of which represent promising avenues for therapeutic interventions in the clinic: (1) the role of the glutamatergic N-methyl-d-aspartate (NMDA) receptor, (2) the role of the brain-derived neurotrophic factor (BDNF)-tyrosine kinase B (TrkB) induced signaling pathway, and (3) the role of the renin-angiotensin system. The modulation of pathways underlying fear learning and extinction, such as the ones presented in this review, in combination with extinction-based exposure therapy, represents promising avenues for therapeutic intervention in the treatment of human fear related disorders. PMID:24254958

  16. FROM THE NEUROBIOLOGY OF EXTINCTION TO IMPROVED CLINICAL TREATMENTS

    PubMed Central

    Morrison, Filomene G.; Ressler, Kerry J.

    2015-01-01

    The neural circuitry underlying the fear response is extremely well conserved across mammalian species, which has allowed for the rapid translation of research findings in rodent models of fear to therapeutic interventions in human populations. Many aspects of exposure-based psychotherapy treatments in humans, which are widely used in the treatment of PTSD, panic disorder, phobias, and other anxiety disorders, are closely paralleled by extinction training in rodent fear conditioning models. Here, we discuss how the neural circuitry of fear learning and extinction in rodent animal models may be used to understand the underlying neural circuitry of fear-related disorders, such as PTSD in humans. We examine the factors that contribute to the pathology and development of PTSD. Next, we will review how fear is measured in animal models using classical Pavlovian fear conditioning paradigms, as well as brain regions such as the amygdala, which are involved in the fear response across species. Finally, we highlight the following three systems involved in the extinction of fear, all of which represent promising avenues for therapeutic interventions in the clinic: (1) the role of the glutamatergic N-methyl-d-aspartate (NMDA) receptor, (2) the role of the brain-derived neurotrophic factor (BDNF)–tyrosine kinase B (TrkB) induced signaling pathway, and (3) the role of the renin-angiotensin system. The modulation of pathways underlying fear learning and extinction, such as the ones presented in this review, in combination with extinction-based exposure therapy, represents promising avenues for therapeutic intervention in the treatment of human fear related disorders. PMID:24254958

  17. Effects of a Context Shift and Multiple Context Extinction on Reactivity to Alcohol Cues

    PubMed Central

    MacKillop, James; Lisman, Stephen A.

    2008-01-01

    Cue exposure treatment (CET) attempts to reduce the influence of conditioned substance cues on addictive behavior via prolonged cue exposure with response prevention (i.e., extinction), but has received only modest empirical support in clinical trials. This may be because extinction learning appears to be context dependent and a change in context may result in a return of conditioned responding (i.e., renewal), although this has received only limited empirical examination. The current study used a four-session laboratory analogue of CET to examine whether a change in context following three sessions of alcohol cue exposure with response prevention would result in renewal of conditioned responding. In addition, this study examined whether conducting extinction in multiple contexts would attenuate renewal of conditioned responding. In a one-way between-subjects design, 73 heavy drinkers (71% male) were randomized to three conditions: 1) single context extinction (extinction to alcohol cues in the same context for three sessions followed by a context shift at the fourth session); 2) multiple context extinction (extinction to alcohol cues in different contexts each day for all four sessions); and 3) pseudo-extinction control condition (exposure to neutral cues in the same context for three sessions followed by exposure to alcohol cues at the fourth session). The results revealed the predicted cue reactivity and extinction effects, but the hypotheses that a context shift would generate renewed cue reactivity and that multiple contexts would enhance extinction were not supported. Methodological aspects of the study and the need for parametric data on the context dependency of extinction to alcohol cues are discussed. PMID:18729687

  18. Uncertainty-Dependent Extinction of Fear Memory in an Amygdala-mPFC Neural Circuit Model.

    PubMed

    Li, Yuzhe; Nakae, Ken; Ishii, Shin; Naoki, Honda

    2016-09-01

    Uncertainty of fear conditioning is crucial for the acquisition and extinction of fear memory. Fear memory acquired through partial pairings of a conditioned stimulus (CS) and an unconditioned stimulus (US) is more resistant to extinction than that acquired through full pairings; this effect is known as the partial reinforcement extinction effect (PREE). Although the PREE has been explained by psychological theories, the neural mechanisms underlying the PREE remain largely unclear. Here, we developed a neural circuit model based on three distinct types of neurons (fear, persistent and extinction neurons) in the amygdala and medial prefrontal cortex (mPFC). In the model, the fear, persistent and extinction neurons encode predictions of net severity, of unconditioned stimulus (US) intensity, and of net safety, respectively. Our simulation successfully reproduces the PREE. We revealed that unpredictability of the US during extinction was represented by the combined responses of the three types of neurons, which are critical for the PREE. In addition, we extended the model to include amygdala subregions and the mPFC to address a recent finding that the ventral mPFC (vmPFC) is required for consolidating extinction memory but not for memory retrieval. Furthermore, model simulations led us to propose a novel procedure to enhance extinction learning through re-conditioning with a stronger US; strengthened fear memory up-regulates the extinction neuron, which, in turn, further inhibits the fear neuron during re-extinction. Thus, our models increased the understanding of the functional roles of the amygdala and vmPFC in the processing of uncertainty in fear conditioning and extinction. PMID:27617747

  19. Are Isolated Indigenous Populations Headed toward Extinction?

    PubMed Central

    Walker, Robert S.; Kesler, Dylan C.; Hill, Kim R.

    2016-01-01

    At least 50 indigenous groups spread across lowland South America remain isolated and have only intermittent and mostly hostile interactions with the outside world. Except in emergency situations, the current policy of governments in Brazil, Colombia, and Peru towards isolated tribes is a “leave them alone” strategy, in which isolated groups are left uncontacted. However, these no-contact policies are based on the assumption that isolated populations are healthy and capable of persisting in the face of mounting external threats, and that they can maintain population viability in the long-term. Here, we test this assumption by tracking the sizes and movements of cleared horticultural areas made by 8 isolated groups over the last 10–14 years. We used deforestation data derived from remote sensing Landsat satellite sensors to identify clearings, and those were then validated and assessed with high-resolution imagery. We found only a single example of a relatively large and growing population (c. 50 cleared ha and 400 people), whereas all of the other 7 groups exhibited much smaller villages and gardens with no sizable growth through time. These results indicated that the smaller groups are critically endangered, and it prompts an urgent re-thinking of policies toward isolated populations, including plans for well-organized contacts that may help save lives and rescue isolated indigenous populations from imminent extinction. PMID:26954672

  20. Are Isolated Indigenous Populations Headed toward Extinction?

    PubMed

    Walker, Robert S; Kesler, Dylan C; Hill, Kim R

    2016-01-01

    At least 50 indigenous groups spread across lowland South America remain isolated and have only intermittent and mostly hostile interactions with the outside world. Except in emergency situations, the current policy of governments in Brazil, Colombia, and Peru towards isolated tribes is a "leave them alone" strategy, in which isolated groups are left uncontacted. However, these no-contact policies are based on the assumption that isolated populations are healthy and capable of persisting in the face of mounting external threats, and that they can maintain population viability in the long-term. Here, we test this assumption by tracking the sizes and movements of cleared horticultural areas made by 8 isolated groups over the last 10-14 years. We used deforestation data derived from remote sensing Landsat satellite sensors to identify clearings, and those were then validated and assessed with high-resolution imagery. We found only a single example of a relatively large and growing population (c. 50 cleared ha and 400 people), whereas all of the other 7 groups exhibited much smaller villages and gardens with no sizable growth through time. These results indicated that the smaller groups are critically endangered, and it prompts an urgent re-thinking of policies toward isolated populations, including plans for well-organized contacts that may help save lives and rescue isolated indigenous populations from imminent extinction. PMID:26954672

  1. Role of Dopamine 2 Receptor in Impaired Drug-Cue Extinction in Adolescent Rats.

    PubMed

    Zbukvic, Isabel C; Ganella, Despina E; Perry, Christina J; Madsen, Heather B; Bye, Christopher R; Lawrence, Andrew J; Kim, Jee Hyun

    2016-06-01

    Adolescent drug users display resistance to treatment such as cue exposure therapy (CET), as well as increased liability to relapse. The basis of CET is extinction learning, which involves dopamine signaling in the medial prefrontal cortex (mPFC). This system undergoes dramatic alterations during adolescence. Therefore, we investigated extinction of a cocaine-associated cue in adolescent and adult rats. While cocaine self-administration and lever-alone extinction were not different between the two ages, we observed that cue extinction reduced cue-induced reinstatement in adult but not adolescent rats. Infusion of the selective dopamine 2 receptor (D2R)-like agonist quinpirole into the infralimbic cortex (IL) of the mPFC prior to cue extinction significantly reduced cue-induced reinstatement in adolescents. This effect was replicated by acute systemic treatment with the atypical antipsychotic aripiprazole (Abilify), a partial D2R-like agonist. These data suggest that adolescents may be more susceptible to relapse due to a deficit in cue extinction learning, and highlight the significance of D2R signaling in the IL for cue extinction during adolescence. These findings inspire new tactics for improving adolescent CET, with aripiprazole representing an exciting potential pharmacological adjunct for behavioral therapy. PMID:26946126

  2. From lab to clinic: Extinction of cued cravings to reduce overeating.

    PubMed

    Jansen, Anita; Schyns, Ghislaine; Bongers, Peggy; van den Akker, Karolien

    2016-08-01

    Food cue reactivity is a strong motivation to eat, even in the absence of hunger. Therefore, food cue reactivity might sabotage healthy eating, induce weight gain and impede weight loss or weight maintenance. Food cue reactivity can be learned via Pavlovian appetitive conditioning: It is easily acquired but the extinction of appetitive responding seems to be more challenging. Several properties of extinction make it fragile: extinction does not erase the original learning and extinction is context-dependent. These properties threaten full extinction and increase the risk of full relapse. Extinction procedures are discussed to reduce or prevent the occurrence of rapid reacquisition, spontaneous recovery, renewal and reinstatement after extinction. A translation to food cue exposure treatment is made and suggestions are provided, such as conducting the exposure in relevant contexts, using occasional reinforcement and targeting expectancy violation instead of habituation. A new hypothesis proposed here is that the adding of inhibition training to strengthen inhibition skills that reduce instrumental responding, might be beneficial to improve food cue exposure effects. PMID:26994737

  3. Role of Dopamine 2 Receptor in Impaired Drug-Cue Extinction in Adolescent Rats

    PubMed Central

    Zbukvic, Isabel C.; Ganella, Despina E.; Perry, Christina J.; Madsen, Heather B.; Bye, Christopher R.; Lawrence, Andrew J.; Kim, Jee Hyun

    2016-01-01

    Adolescent drug users display resistance to treatment such as cue exposure therapy (CET), as well as increased liability to relapse. The basis of CET is extinction learning, which involves dopamine signaling in the medial prefrontal cortex (mPFC). This system undergoes dramatic alterations during adolescence. Therefore, we investigated extinction of a cocaine-associated cue in adolescent and adult rats. While cocaine self-administration and lever-alone extinction were not different between the two ages, we observed that cue extinction reduced cue-induced reinstatement in adult but not adolescent rats. Infusion of the selective dopamine 2 receptor (D2R)-like agonist quinpirole into the infralimbic cortex (IL) of the mPFC prior to cue extinction significantly reduced cue-induced reinstatement in adolescents. This effect was replicated by acute systemic treatment with the atypical antipsychotic aripiprazole (Abilify), a partial D2R-like agonist. These data suggest that adolescents may be more susceptible to relapse due to a deficit in cue extinction learning, and highlight the significance of D2R signaling in the IL for cue extinction during adolescence. These findings inspire new tactics for improving adolescent CET, with aripiprazole representing an exciting potential pharmacological adjunct for behavioral therapy. PMID:26946126

  4. Deep brain stimulation of the ventral striatum enhances extinction of conditioned fear.

    PubMed

    Rodriguez-Romaguera, Jose; Do Monte, Fabricio H M; Quirk, Gregory J

    2012-05-29

    Deep brain stimulation (DBS) of the ventral capsule/ventral striatum (VC/VS) reduces symptoms of intractable obsessive-compulsive disorder (OCD), but the mechanism of action is unknown. OCD is characterized by avoidance behaviors that fail to extinguish, and DBS could act, in part, by facilitating extinction of fear. We investigated this possibility by using auditory fear conditioning in rats, for which the circuits of fear extinction are well characterized. We found that DBS of the VS (the VC/VS homolog in rats) during extinction training reduced fear expression and strengthened extinction memory. Facilitation of extinction was observed for a specific zone of dorsomedial VS, just above the anterior commissure; stimulation of more ventrolateral sites in VS impaired extinction. DBS effects could not be obtained with pharmacological inactivation of either dorsomedial VS or ventrolateral VS, suggesting an extrastriatal mechanism. Accordingly, DBS of dorsomedial VS (but not ventrolateral VS) increased expression of a plasticity marker in the prelimbic and infralimbic prefrontal cortices, the orbitofrontal cortex, the amygdala central nucleus (lateral division), and intercalated cells, areas known to learn and express extinction. Facilitation of fear extinction suggests that, in accord with clinical observations, DBS could augment the effectiveness of cognitive behavioral therapies for OCD. PMID:22586125

  5. Blockade of estrogen by hormonal contraceptives impairs fear extinction in female rats and women

    PubMed Central

    Graham, Bronwyn M; Milad, Mohammed R

    2012-01-01

    Background Fear extinction is a laboratory model of fear inhibition and is the basis of exposure therapy for anxiety disorders. Emerging evidence from naturally cycling female rodents and women indicates that estrogens are necessary to the consolidation of fear extinction. Hormonal contraceptives (HCs) inhibit estrogen production, yet their effects on fear extinction are unknown. Methods We used a cross-species translational approach to investigate the impact of HCs and estradiol supplementation on fear extinction in healthy women (n=76) and female rats (n=140). Results Women using HCs exhibited significantly poorer extinction recall compared to naturally cycling women. The extinction impairment was also apparent in HC-treated female rats and was associated with reduced serum estradiol levels. The impairment could be rescued in HC-treated rats either by terminating HC treatment after fear learning or by systemic injection of estrogen-receptor agonists prior to fear extinction, all of which restored serum estradiol levels. Finally, a single administration of estradiol to naturally cycling women significantly enhanced their ability to recall extinction memories. Conclusions Together, these findings suggest that HCs may impact women’s ability to inhibit fear, but that this impairment is not permanent and could potentially be alleviated with estrogen treatment. PMID:23158459

  6. Deep brain stimulation, histone deacetylase inhibitors and glutamatergic drugs rescue resistance to fear extinction in a genetic mouse model.

    PubMed

    Whittle, Nigel; Schmuckermair, Claudia; Gunduz Cinar, Ozge; Hauschild, Markus; Ferraguti, Francesco; Holmes, Andrew; Singewald, Nicolas

    2013-01-01

    Anxiety disorders are characterized by persistent, excessive fear. Therapeutic interventions that reverse deficits in fear extinction represent a tractable approach to treating these disorders. We previously reported that 129S1/SvImJ (S1) mice show no extinction learning following normal fear conditioning. We now demonstrate that weak fear conditioning does permit fear reduction during massed extinction training in S1 mice, but reveals specific deficiency in extinction memory consolidation/retrieval. Rescue of this impaired extinction consolidation/retrieval was achieved with d-cycloserine (N-methly-d-aspartate partial agonist) or MS-275 (histone deacetylase (HDAC) inhibitor), applied after extinction training. We next examined the ability of different drugs and non-pharmacological manipulations to rescue the extreme fear extinction deficit in S1 following normal fear conditioning with the ultimate aim to produce low fear levels in extinction retrieval tests. Results showed that deep brain stimulation (DBS) by applying high frequency stimulation to the nucleus accumbens (ventral striatum) during extinction training, indeed significantly reduced fear during extinction retrieval compared to sham stimulation controls. Rescue of both impaired extinction acquisition and deficient extinction consolidation/retrieval was achieved with prior extinction training administration of valproic acid (a GABAergic enhancer and HDAC inhibitor) or AMN082 [metabotropic glutamate receptor 7 (mGlu7) agonist], while MS-275 or PEPA (AMPA receptor potentiator) failed to affect extinction acquisition in S1 mice. Collectively, these data identify potential beneficial effects of DBS and various drug treatments, including those with HDAC inhibiting or mGlu7 agonism properties, as adjuncts to overcome treatment resistance in exposure-based therapies. This article is part of a Special Issue entitled 'Cognitive Enhancers'. PMID:22722028

  7. Deep brain stimulation, histone deacetylase inhibitors and glutamatergic drugs rescue resistance to fear extinction in a genetic mouse model

    PubMed Central

    Whittle, Nigel; Schmuckermair, Claudia; Gunduz Cinar, Ozge; Hauschild, Markus; Ferraguti, Francesco; Holmes, Andrew; Singewald, Nicolas

    2013-01-01

    Anxiety disorders are characterized by persistent, excessive fear. Therapeutic interventions that reverse deficits in fear extinction represent a tractable approach to treating these disorders. We previously reported that 129S1/SvImJ (S1) mice show no extinction learning following normal fear conditioning. We now demonstrate that weak fear conditioning does permit fear reduction during massed extinction training in S1 mice, but reveals specific deficiency in extinction memory consolidation/retrieval. Rescue of this impaired extinction consolidation/retrieval was achieved with d-cycloserine (N-methly-d-aspartate partial agonist) or MS-275 (histone deacetylase (HDAC) inhibitor), applied after extinction training. We next examined the ability of different drugs and non-pharmacological manipulations to rescue the extreme fear extinction deficit in S1 following normal fear conditioning with the ultimate aim to produce low fear levels in extinction retrieval tests. Results showed that deep brain stimulation (DBS) by applying high frequency stimulation to the nucleus accumbens (ventral striatum) during extinction training, indeed significantly reduced fear during extinction retrieval compared to sham stimulation controls. Rescue of both impaired extinction acquisition and deficient extinction consolidation/retrieval was achieved with prior extinction training administration of valproic acid (a GABAergic enhancer and HDAC inhibitor) or AMN082 [metabotropic glutamate receptor 7 (mGlu7) agonist], while MS-275 or PEPA (AMPA receptor potentiator) failed to affect extinction acquisition in S1 mice. Collectively, these data identify potential beneficial effects of DBS and various drug treatments, including those with HDAC inhibiting or mGlu7 agonism properties, as adjuncts to overcome treatment resistance in exposure-based therapies. This article is part of a Special Issue entitled ‘Cognitive Enhancers’. PMID:22722028

  8. The Class I HDAC Inhibitor RGFP963 Enhances Consolidation of Cued Fear Extinction

    ERIC Educational Resources Information Center

    Bowers, Mallory E.; Xia, Bing; Carreiro, Samantha; Ressler, Kerry J.

    2015-01-01

    Evidence indicates that broad, nonspecific histone deacetylase (HDAC) inhibition enhances learning and memory, however, the contribution of the various HDACs to specific forms of learning is incompletely understood. Here, we show that the Class I HDAC inhibitor, RGFP963, enhances consolidation of cued fear extinction. However, RGFP966, a strong…

  9. Fear conditioning and extinction across development: Evidence from human studies and animal models☆

    PubMed Central

    Shechner, Tomer; Hong, Melanie; Britton, Jennifer C.; Pine, Daniel S.; Fox, Nathan A.

    2015-01-01

    The ability to differentiate danger and safety through associative processes emerges early in life. Understanding the mechanisms underlying associative learning of threat and safety can clarify the processes that shape development of normative fears and pathological anxiety. Considerable research has used fear conditioning and extinction paradigms to delineate underlying mechanisms in animals and human adults; however, little is known about these mechanisms in children and adolescents. The current paper summarizes the empirical data on the development of fear conditioning and extinction. It reviews methodological considerations and future directions for research on fear conditioning and extinction in pediatric populations. PMID:24746848

  10. Fear conditioning and extinction across development: evidence from human studies and animal models.

    PubMed

    Shechner, Tomer; Hong, Melanie; Britton, Jennifer C; Pine, Daniel S; Fox, Nathan A

    2014-07-01

    The ability to differentiate danger and safety through associative processes emerges early in life. Understanding the mechanisms underlying associative learning of threat and safety can clarify the processes that shape development of normative fears and pathological anxiety. Considerable research has used fear conditioning and extinction paradigms to delineate underlying mechanisms in animals and human adults; however, little is known about these mechanisms in children and adolescents. The current paper summarizes the empirical data on the development of fear conditioning and extinction. It reviews methodological considerations and future directions for research on fear conditioning and extinction in pediatric populations. PMID:24746848

  11. Reexposure to the amnestic agent alleviates cycloheximide-induced retrograde amnesia for reactivated and extinction memories.

    PubMed

    Briggs, James F; Olson, Brian P

    2013-05-01

    We investigated whether reexposure to an amnestic agent would reverse amnesia for extinction of learned fear similar to that of a reactivated memory. When cycloheximide (CHX) was administered immediately after a brief cue-induced memory reactivation (15 sec) and an extended extinction session (12 min) rats showed retrograde amnesia for both memories. CHX did not produce amnesia for a moderate extinction session (6 min). Re-administering CHX before testing reversed the amnestic effect for both memories (i.e., the memories were recovered). These results are discussed using a modified state dependent model of retrograde amnesia. PMID:23596315

  12. Plasticity of Fear and Safety Neurons of the Amygdala in Response to Fear Extinction

    PubMed Central

    Sangha, Susan

    2015-01-01

    Fear inhibition learning induces plasticity and remodeling of circuits within the amygdala. Most studies examine these changes in nondiscriminative fear conditioning paradigms. Using a discriminative fear, safety, and reward conditioning task, Sangha et al. (2013) have previously reported several neural microcircuits within the basal amygdala (BA) which discriminate among these cues, including a subpopulation of neurons responding selectively to a safety cue and not a fear cue. Here, the hypothesis that these “safety” neurons isolated during discriminative conditioning are biased to become fear cue responsive as a result of extinction, when fear behavior diminishes, was tested. Although 41% of “safety” neurons became fear cue responsive as a result of extinction, the data revealed that there was no bias for these neurons to become preferentially responsive during fear extinction compared to the other identified subgroups. In addition to the plasticity seen in the “safety” neurons, 44% of neurons unresponsive to either the fear cue or safety cue during discriminative conditioning became fear cue responsive during extinction. Together these emergent responses to the fear cue as a result of extinction support the hypothesis that new learning underlies extinction. In contrast, 47% of neurons responsive to the fear cue during discriminative conditioning became unresponsive to the fear cue during extinction. These findings are consistent with a suppression of neural responding mediated by inhibitory learning, or, potentially, by direct unlearning. Together, the data support extinction as an active process involving both gains and losses of responses to the fear cue and suggests the final output of the integrated BA circuit in influencing fear behavior is a balance of excitation and inhibition, and perhaps reversal of learning-induced changes. PMID:26733838

  13. Problematising Early School Leaving

    ERIC Educational Resources Information Center

    Ross, Alistair; Leathwood, Carole

    2013-01-01

    Early school leaving has been identified as a key policy priority across Europe. In this article, we critically discuss the underpinning assumptions and rationale for this policy focus, challenging the association that is made between early school leaving, economic growth and employment. We suggest that ESL is important, not because it is…

  14. Darwin and the uses of extinction.

    PubMed

    Beer, Gillian

    2009-01-01

    We currently view extinction with dismay and even horror, but Darwin saw extinction as ordinary and as necessary to evolutionary change. Still, the degree to which extinction is fundamental to his theory is rarely discussed. This essay examines Darwin's linking of the idea of "improvement" with that of natural selection and tracks a cluster of reasons for our changed valuation of extinction now. Those reasons demonstrate how scientific information and ideological preferences have reshaped the concept. The essay challenges the reader to assess some current assumptions about extinction and concludes by considering the shift in Darwin's own understanding from the "Origin" to the late "Autobiography". PMID:19824221

  15. The extinction differential induced virulence macroevolution

    NASA Astrophysics Data System (ADS)

    Zhang, Feng; Xu, Liufang; Wang, Jin

    2014-04-01

    We apply the potential-flux landscape theory to deal with the large fluctuation induced extinction phenomena. We quantify the most probable extinction pathway on the landscape and measure the extinction risk by the landscape topography. In this Letter, we investigate the disease extinction through an epidemic model described by a set of chemical reaction. We found the virulence-differential-dependent symbioses between mother and daughter pathogen species: mutualism and parasitism. The symbioses, whether mutualism or parasitism, benefit the higher virulence species. This implies that speciation towards lower virulence is an effective strategy for a pathogen species to reduce its extinction risk.

  16. Neanderthal Extinction by Competitive Exclusion

    PubMed Central

    Banks, William E.; d'Errico, Francesco; Peterson, A. Townsend; Kageyama, Masa; Sima, Adriana; Sánchez-Goñi, Maria-Fernanda

    2008-01-01

    Background Despite a long history of investigation, considerable debate revolves around whether Neanderthals became extinct because of climate change or competition with anatomically modern humans (AMH). Methodology/Principal Findings We apply a new methodology integrating archaeological and chronological data with high-resolution paleoclimatic simulations to define eco-cultural niches associated with Neanderthal and AMH adaptive systems during alternating cold and mild phases of Marine Isotope Stage 3. Our results indicate that Neanderthals and AMH exploited similar niches, and may have continued to do so in the absence of contact. Conclusions/Significance The southerly contraction of Neanderthal range in southwestern Europe during Greenland Interstadial 8 was not due to climate change or a change in adaptation, but rather concurrent AMH geographic expansion appears to have produced competition that led to Neanderthal extinction. PMID:19107186

  17. Testing for periodicity of extinction

    NASA Technical Reports Server (NTRS)

    Raup, David M.; Sepkoski, J. J., Jr.

    1988-01-01

    The statistical techniques used by Raup and Sepkoski (1984 and 1986) to identify a 26-Myr periodicity in the biological extinction record for the past 250 Myr are reexamined, responding in detail to the criticisms of Stigler and Wagner (1987). It is argued that evaluation of a much larger set of extinction data using a time scale with 51 sampling intervals supports the finding of periodicity. In a reply by Sigler and Wagner, the preference for a 26-Myr period is attributed to a numerical quirk in the Harland et al. (1982) time scale, in which the subinterval boundaries are not linear interpolations between the stage boundaries but have 25-Myr periodicity. It is stressed that the results of the stringent statistical tests imposed do not disprove periodicity but rather indicate that the evidence and analyses presented so far are inadequate.

  18. Optimising Extinction of Conditioned Disgust

    PubMed Central

    Bosman, Renske C.; Borg, Charmaine; de Jong, Peter J.

    2016-01-01

    Maladaptive disgust responses are tenacious and resistant to exposure-based interventions. In a similar vein, laboratory studies have shown that conditioned disgust is relatively insensitive to Conditioned Stimulus (CS)-only extinction procedures. The relatively strong resistance to extinction might be explained by disgust’s adaptive function to motivate avoidance from contamination threats (pathogens) that cannot be readily detected and are invisible to the naked eye. Therefore, the mere visual presentation of unreinforced disgust eliciting stimuli might not be sufficient to correct a previously acquired threat value of the CS+. Following this, the current study tested whether the efficacy of CS-only exposure can be improved by providing additional safety information about the CS+. For the CSs we included two neutral items a pea soup and a sausage roll, whereas for the Unconditioned Stimulus (US) we used one video clip of a woman vomiting and a neutral one about glass blowing. The additional safety information was conveyed by allowing actual contact with the CS+ or by observing an actress eating the food items representing the CS+. When additional safety information was provided via allowing direct contact with the CS+, there was a relatively strong post-extinction increase in participants’ willingness-to-eat the CS+. This beneficial effect was still evident at one-week follow up. Also self-reported disgust was lower at one-week follow up when additional safety information was provided. The current findings help explain why disgust is relatively insensitive to CS-only extinction procedures, and provide helpful starting points to improve interventions that are aimed to reduce distress in disgust-related psychopathology. PMID:26849211

  19. Optimising Extinction of Conditioned Disgust.

    PubMed

    Bosman, Renske C; Borg, Charmaine; de Jong, Peter J

    2016-01-01

    Maladaptive disgust responses are tenacious and resistant to exposure-based interventions. In a similar vein, laboratory studies have shown that conditioned disgust is relatively insensitive to Conditioned Stimulus (CS)-only extinction procedures. The relatively strong resistance to extinction might be explained by disgust's adaptive function to motivate avoidance from contamination threats (pathogens) that cannot be readily detected and are invisible to the naked eye. Therefore, the mere visual presentation of unreinforced disgust eliciting stimuli might not be sufficient to correct a previously acquired threat value of the CS+. Following this, the current study tested whether the efficacy of CS-only exposure can be improved by providing additional safety information about the CS+. For the CSs we included two neutral items a pea soup and a sausage roll, whereas for the Unconditioned Stimulus (US) we used one video clip of a woman vomiting and a neutral one about glass blowing. The additional safety information was conveyed by allowing actual contact with the CS+ or by observing an actress eating the food items representing the CS+. When additional safety information was provided via allowing direct contact with the CS+, there was a relatively strong post-extinction increase in participants' willingness-to-eat the CS+. This beneficial effect was still evident at one-week follow up. Also self-reported disgust was lower at one-week follow up when additional safety information was provided. The current findings help explain why disgust is relatively insensitive to CS-only extinction procedures, and provide helpful starting points to improve interventions that are aimed to reduce distress in disgust-related psychopathology. PMID:26849211

  20. Extinction of metastable stochastic populations.

    PubMed

    Assaf, Michael; Meerson, Baruch

    2010-02-01

    We investigate the phenomenon of extinction of a long-lived self-regulating stochastic population, caused by intrinsic (demographic) noise. Extinction typically occurs via one of two scenarios depending on whether the absorbing state n=0 is a repelling (scenario A) or attracting (scenario B) point of the deterministic rate equation. In scenario A the metastable stochastic population resides in the vicinity of an attracting fixed point next to the repelling point n=0 . In scenario B there is an intermediate repelling point n=n1 between the attracting point n=0 and another attracting point n=n2 in the vicinity of which the metastable population resides. The crux of the theory is a dissipative variant of WKB (Wentzel-Kramers-Brillouin) approximation which assumes that the typical population size in the metastable state is large. Starting from the master equation, we calculate the quasistationary probability distribution of the population sizes and the (exponentially long) mean time to extinction for each of the two scenarios. When necessary, the WKB approximation is complemented (i) by a recursive solution of the quasistationary master equation at small n and (ii) by the van Kampen system-size expansion, valid near the fixed points of the deterministic rate equation. The theory yields both entropic barriers to extinction and pre-exponential factors, and holds for a general set of multistep processes when detailed balance is broken. The results simplify considerably for single-step processes and near the characteristic bifurcations of scenarios A and B. PMID:20365539

  1. Surviving mass extinction by bridging the benthic/planktic divide

    PubMed Central

    Darling, Kate F.; Thomas, Ellen; Kasemann, Simone A.; Seears, Heidi A.; Smart, Christopher W.; Wade, Christopher M.

    2009-01-01

    Evolution of planktic organisms from benthic ancestors is commonly thought to represent unidirectional expansion into new ecological domains, possibly only once per clade. For foraminifera, this evolutionary expansion occurred in the Early–Middle Jurassic, and all living and extinct planktic foraminifera have been placed within 1 clade, the Suborder Globigerinina. The subsequent radiation of planktic foraminifera in the Jurassic and Cretaceous resulted in highly diverse assemblages, which suffered mass extinction at the end of the Cretaceous, leaving an impoverished assemblage dominated by microperforate triserial and biserial forms. The few survivor species radiated to form diverse assemblages once again in the Cenozoic. There have, however, long been doubts regarding the monophyletic origin of planktic foraminifera. We present surprising but conclusive genetic evidence that the Recent biserial planktic Streptochilus globigerus belongs to the same biological species as the benthic Bolivina variabilis, and geochemical evidence that this ecologically flexible species actively grows within the open-ocean surface waters, thus occupying both planktic and benthic domains. Such a lifestyle (tychopelagic) had not been recognized as adapted by foraminifera. Tychopelagic are endowed with great ecological advantage, enabling rapid recolonization of the extinction-susceptible pelagic domain from the benthos. We argue that the existence of such forms must be considered in resolving foraminiferal phylogeny. PMID:19574452

  2. Extinction Risk Escalates in the Tropics

    PubMed Central

    Vamosi, Jana C.; Vamosi, Steven M.

    2008-01-01

    The latitudinal biodiversity gradient remains one of the most widely recognized yet puzzling patterns in nature [1]. Presently, the high level of extinction of tropical species, referred to as the “tropical biodiversity crisis”, has the potential to erode this pattern. While the connection between species richness, extinction, and speciation has long intrigued biologists [2], [3], these interactions have experienced increased poignancy due to their relevancy to where we should concentrate our conservation efforts. Natural extinction is a phenomenon thought to have its own latitudinal gradient, with lower extinction rates in the tropics being reported in beetles, birds, mammals, and bivalves [4]–[7]. Processes that have buffered ecosystems from high extinction rates in the past may also buffer ecosystems against disturbance of anthropogenic origin. While potential parallels between historical and present-day extinction patterns have been acknowledged, they remain only superficially explored and plant extinction patterns have been particularly neglected. Studies on the disappearances of animal species have reached conflicting conclusions, with the rate of extinction appearing either higher [8] or lower [9] in species richness hotspots. Our global study of extinction risk in vascular plants finds disproportionately higher extinction risk in tropical countries, even when indicators of human pressure (GDP, population density, forest cover change) are taken into account. Our results are at odds with the notion that the tropics represent a museum of plant biodiversity (places of historically lowered extinction) and we discuss mechanisms that may reconcile this apparent contradiction. PMID:19066623

  3. Systemic or intrahippocampal delivery of histone deacetylase inhibitors facilitates fear extinction.

    PubMed

    Lattal, K Matthew; Barrett, Ruth M; Wood, Marcelo A

    2007-10-01

    Several recent studies have shown that chromatin, the DNA-protein complex that packages genomic DNA, has an important function in learning and memory. Dynamic chromatin modification via histone deacetylase (HDAC) inhibitors and histone acetyltransferases may enhance hippocampal synaptic plasticity and hippocampus-dependent memory. Little is known about the effects of HDAC inhibitors on extinction, a learning process through which the ability of a previously conditioned stimulus, such as a conditioning context, to evoke a conditioned response is diminished. The authors demonstrate that administration of the HDAC inhibitors sodium butyrate (NaB) systemically or trichostatin A (TSA) intrahippocampally prior to a brief (3-min) contextual extinction session causes context-evoked fear to decrease to levels observed with a long (24-min) extinction session. These results suggest that HDAC inhibitors may enhance learning during extinction and are consistent with other studies demonstrating a role for the hippocampus in contextual extinction. Molecular and behavioral mechanisms through which this enhanced extinction effect may occur are discussed. PMID:17907845

  4. Were all extinction events caused by impacts?

    NASA Astrophysics Data System (ADS)

    Sheehan, P. M.; Coorough, P. J.

    Extraterrestrial impacts are firmly implicated in several of the five major Phanerozoic extinction events. A critical issue now is whether extraterrestrial events have been the only mechanism that produced physical changes of sufficient magnitude to cause major extinction events. While we believe the evidence is overwhelming that the KT extinction event was caused by an impact, we also find that an event of similar or larger size near the end of the Ordovician is best explained by terrestrial causes. The Ordovician extinction event (End-O extinction event) occurred near the end of the Ordovician, but the interval of extinction was completed prior to the newly established Ordovician-Silurian boundary. In spite of extensive field studies, a convincing signature of an associated impact has not been found. However, a prominent glaciation does coincide with the End-O extinction event.

  5. Were all extinction events caused by impacts?

    NASA Technical Reports Server (NTRS)

    Sheehan, P. M.; Coorough, P. J.

    1994-01-01

    Extraterrestrial impacts are firmly implicated in several of the five major Phanerozoic extinction events. A critical issue now is whether extraterrestrial events have been the only mechanism that produced physical changes of sufficient magnitude to cause major extinction events. While we believe the evidence is overwhelming that the KT extinction event was caused by an impact, we also find that an event of similar or larger size near the end of the Ordovician is best explained by terrestrial causes. The Ordovician extinction event (End-O extinction event) occurred near the end of the Ordovician, but the interval of extinction was completed prior to the newly established Ordovician-Silurian boundary. In spite of extensive field studies, a convincing signature of an associated impact has not been found. However, a prominent glaciation does coincide with the End-O extinction event.

  6. The case for extraterrestrial causes of extinction

    NASA Technical Reports Server (NTRS)

    Raup, D. M.

    1989-01-01

    The dramatic increase in our knowledge of large-body impacts that have occurred in Earth's history has led to strong arguments for the plausibility of meteorite impact as a cause of extinction. Proof of causation is often hampered, however, by our inability to demonstrate the synchronism of specific impacts and extinctions. A central problem is range truncation: the last reported occurrences of fossil taxa generally underestimate the true times of extinction. Range truncation, because of gaps in sedimentation, lack of preservation, or lack of discovery, can make sudden extinctions appear gradual and gradual extinctions appear sudden. Also, stepwise extinction may appear as an artefact of range truncation. These effects are demonstrated by experiments performed on data from field collections of Cretaceous ammonities from Zumaya (Spain). The challenge for future research is to develop a new calculus for treating biostratigraphic data so that fossils can provide more accurate assessments of the timing of extinctions.

  7. The effect of phosphodiesterase inhibitors on the extinction of cocaine-induced conditioned place preference in mice.

    PubMed

    Liddie, Shervin; Anderson, Karen L; Paz, Andres; Itzhak, Yossef

    2012-10-01

    Several phosphodiesterase inhibitors (PDEis) improve cognition, suggesting that an increase in brain cAMP and cGMP facilitates learning and memory. Since extinction of drug-seeking behavior requires associative learning, consolidation and formation of new memory, the present study investigated the efficacy of three different PDEis in the extinction of cocaine-induced conditioned place preference (CPP) in B6129S mice. Mice were conditioned by escalating doses of cocaine which was resistant to extinction by free exploration. Immediately following each extinction session mice received (a) saline/vehicle, (b) rolipram (PDE4 inhibitor), (c) BAY-73-6691 (PDE9 inhibitor) or (d) papaverine (PDE10A inhibitor). Mice that received saline/vehicle during extinction training showed no reduction in CPP for >10 days. BAY-73-6691 (a) dose-dependently increased cGMP in hippocampus and amygdala, (b) significantly facilitated extinction and (c) diminished the reinstatement of cocaine CPP. Rolipram, which selectively increased brain cAMP levels, and papaverine which caused increases in both cAMP and cGMP levels, had no significant effect on the extinction of cocaine CPP. The results suggest that increase in hippocampal and amygdalar cGMP levels via blockade of PDE9 has a prominent role in the consolidation of extinction learning. PMID:22596207

  8. CO2 and the end-Triassic mass extinction.

    PubMed

    Beerling, David

    2002-01-24

    The end of the Triassic period was marked by one of the largest and most enigmatic mass-extinction events in Earth's history and, with few reliable marine geochemical records, terrestrial sediments offer an important means of deciphering environmental changes at this time. Tanner et al. describe an isotopic study of Mesozoic fossil soils which suggests that the atmospheric concentration of carbon dioxide (pCO2) across the Triassic-Jurassic boundary was relatively constant (within 250 p.p.m.v.), but this is inconsistent with high-resolution evidence from the stomatal characters of fossil leaves. Here I show that the temporal resolution of the fossil-soil samples may have been inadequate for detecting a transient rise in pCO2. I also show that the fossil-soil data are consistent with a large increase in pCO2 across the Triassic-Jurassic boundary when variations in the stable carbon isotope (denoted as delta13C) in terrestrial plant leaves are taken into account. These factors suggest that the linkage between pCO2, global warming and the end-Triassic mass extinction remains intact. PMID:11807542

  9. The Dynamics of Conditioning and Extinction

    PubMed Central

    Killeen, Peter R.; Sanabria, Federico; Dolgov, Igor

    2009-01-01

    Pigeons responded to intermittently reinforced classical conditioning trials with erratic bouts of responding to the CS. Responding depended on whether the prior trial contained a peck, food, or both. A linear-persistence/learning model moved animals into and out of a response state, and a Weibull distribution for number of within-trial responses governed in-state pecking. Variations of trial and inter-trial durations caused correlated changes in rate and probability of responding, and model parameters. A novel prediction—in the protracted absence of food, response rates can plateau above zero—was validated. The model predicted smooth acquisition functions when instantiated with the probability of food, but a more accurate jagged learning curve when instantiated with trial-to-trial records of reinforcement. The Skinnerian parameter was dominant only when food could be accelerated or delayed by pecking. These experiments provide a framework for trial-by-trial accounts of conditioning and extinction that increases the information available from the data, permitting them to comment more definitively on complex contemporary models of momentum and conditioning. PMID:19839699

  10. Dynamic competition between large-scale functional networks differentiates fear conditioning and extinction in humans.

    PubMed

    Marstaller, Lars; Burianová, Hana; Reutens, David C

    2016-07-01

    The high evolutionary value of learning when to respond to threats or when to inhibit previously learned associations after changing threat contingencies is reflected in dedicated networks in the animal and human brain. Recent evidence further suggests that adaptive learning may be dependent on the dynamic interaction of meta-stable functional brain networks. However, it is still unclear which functional brain networks compete with each other to facilitate associative learning and how changes in threat contingencies affect this competition. The aim of this study was to assess the dynamic competition between large-scale networks related to associative learning in the human brain by combining a repeated differential conditioning and extinction paradigm with independent component analysis of functional magnetic resonance imaging data. The results (i) identify three task-related networks involved in initial and sustained conditioning as well as extinction, and demonstrate that (ii) the two main networks that underlie sustained conditioning and extinction are anti-correlated with each other and (iii) the dynamic competition between these two networks is modulated in response to changes in associative contingencies. These findings provide novel evidence for the view that dynamic competition between large-scale functional networks differentiates fear conditioning from extinction learning in the healthy brain and suggest that dysfunctional network dynamics might contribute to learning-related neuropsychiatric disorders. PMID:27079532

  11. Effects of rapid eye movement sleep deprivation on fear extinction recall and prediction error signaling.

    PubMed

    Spoormaker, Victor I; Schröter, Manuel S; Andrade, Kátia C; Dresler, Martin; Kiem, Sara A; Goya-Maldonado, Roberto; Wetter, Thomas C; Holsboer, Florian; Sämann, Philipp G; Czisch, Michael

    2012-10-01

    In a temporal difference learning approach of classical conditioning, a theoretical error signal shifts from outcome deliverance to the onset of the conditioned stimulus. Omission of an expected outcome results in a negative prediction error signal, which is the initial step towards successful extinction and may therefore be relevant for fear extinction recall. As studies in rodents have observed a bidirectional relationship between fear extinction and rapid eye movement (REM) sleep, we aimed to test the hypothesis that REM sleep deprivation impairs recall of fear extinction through prediction error signaling in humans. In a three-day design with polysomnographically controlled REM sleep deprivation, 18 young, healthy subjects performed a fear conditioning, extinction and recall of extinction task with visual stimuli, and mild electrical shocks during combined functional magnetic resonance imaging (fMRI) and skin conductance response (SCR) measurements. Compared to the control group, the REM sleep deprivation group had increased SCR scores to a previously extinguished stimulus at early recall of extinction trials, which was associated with an altered fMRI time-course in the left middle temporal gyrus. Post-hoc contrasts corrected for measures of NREM sleep variability also revealed between-group differences primarily in the temporal lobe. Our results demonstrate altered prediction error signaling during recall of fear extinction after REM sleep deprivation, which may further our understanding of anxiety disorders in which disturbed sleep and impaired fear extinction learning coincide. Moreover, our findings are indicative of REM sleep related plasticity in regions that also show an increase in activity during REM sleep. PMID:21826762

  12. Effects of the protein synthesis inhibitor cycloheximide on anxiety-like extinction behavior in an animal model of post-traumatic stress.

    PubMed

    Sandusky, Leslie A; Flint, Robert W; McNay, Ewan C

    2012-05-16

    The effect of cycloheximide (CXM), a protein synthesis inhibitor, on memory reconsolidation and extinction was explored in rats using a model of post-traumatic stress. Forty-two animals were exposed to predator stress followed by 1, 2, or 4 extinction trials. Saline or CXM (1 mg/kg) was administered following the last extinction trial and anxiety was measured in the elevated-plus maze (EPM) seventy-two hours later. Saline control animals exhibited elevated anxiety levels in comparison to a no stress control group. Cycloheximide appeared to maintain stress-induced anxiety responses, which otherwise declined with repeated extinction trials in the saline control groups. These findings suggest that cycloheximide may have induced amnesia for extinction, leaving the target memory of the predatory stress intact resulting in elevated levels of anxiety. The relationships between de novo protein synthesis and reconsolidation of anxiety-related memories following extinction trials may be more complex than originally thought. PMID:22465354

  13. Enhanced extinction of cocaine seeking in brain-derived neurotrophic factor Val66Met knock-in mice.

    PubMed

    Briand, Lisa A; Lee, Francis S; Blendy, Julie A; Pierce, R Christopher

    2012-03-01

    The Val66Met polymorphism in the brain-derived neurotropic factor (BDNF) gene results in alterations in fear extinction behavior in both human populations and mouse models. However, it is not clear whether this polymorphism plays a similar role in extinction of appetitive behaviors. Therefore, we examined operant learning and extinction of both food and cocaine self-administration behavior in an inbred genetic knock-in mouse strain expressing the variant Bdnf. These mice provide a unique opportunity to relate alterations in aversive and appetitive extinction learning as well as provide insight into how human genetic variation can lead to differences in behavior. BDNF(Met/Met) mice exhibited a severe deficit in operant learning as demonstrated by an inability to learn the food self-administration task. Therefore, extinction experiments were performed comparing wildtype (BDNF(Val/Val) ) animals to mice heterozygous for the Met allele (BDNF(Val/Met) ), which did not differ in food or cocaine self-administration behavior. In contrast to the deficit in fear extinction previously demonstrated in these mice, we found that BDNF(Val/Met) mice exhibited more rapid extinction of cocaine responding compared to wildtype mice. No differences were found between the genotypes in the extinction of food self-administration behavior or the reinstatement of cocaine seeking, indicating that the effect is specific to extinction of cocaine responding. These results suggest that the molecular mechanisms underlying aversive and appetitive extinction are distinct from one another and BDNF may play opposing roles in the two phenomena. PMID:22394056

  14. Revisiting propranolol and PTSD: Memory erasure or extinction enhancement?

    PubMed

    Giustino, Thomas F; Fitzgerald, Paul J; Maren, Stephen

    2016-04-01

    Posttraumatic stress disorder (PTSD) has been described as the only neuropsychiatric disorder with a known cause, yet effective behavioral and pharmacotherapies remain elusive for many afflicted individuals. PTSD is characterized by heightened noradrenergic signaling, as well as a resistance to extinction learning. Research aimed at promoting more effective treatment of PTSD has focused on memory erasure (disrupting reconsolidation) and/or enhancing extinction retention through pharmacological manipulations. Propranolol, a β-adrenoceptor antagonist, has received considerable attention for its therapeutic potential in PTSD, although its impact on patients is not always effective. In this review, we briefly examine the consequences of β-noradrenergic manipulations on both reconsolidation and extinction learning in rodents and in humans. We suggest that propranolol is effective as a fear-reducing agent when paired with behavioral therapy soon after trauma when psychological stress is high, possibly preventing or dampening the later development of PTSD. In individuals who have already suffered from PTSD for a significant period of time, propranolol may be less effective at disrupting reconsolidation of strong fear memories. Also, when PTSD has already developed, chronic treatment with propranolol may be more effective than acute intervention, given that individuals with PTSD tend to experience long-term, elevated noradrenergic hyperarousal. PMID:26808441

  15. Methylphenidate enhances extinction of contextual fear

    PubMed Central

    Abraham, Antony D.; Cunningham, Christopher L.; Lattal, K. Matthew

    2012-01-01

    Methylphenidate (MPH, Ritalin) is a norepinephrine and dopamine transporter blocker that is widely used in humans for treatment of attention deficit disorder and narcolepsy. Although there is some evidence that targeted microinjections of MPH may enhance fear acquisition, little is known about the effect of MPH on fear extinction. Here, we show that MPH, administered before or immediately following extinction of contextual fear, will enhance extinction retention in C57BL/6 mice. Animals that received MPH (2.5–10 mg/kg) before an extinction session showed decreased freezing response during extinction, and the effect of the 10 mg/kg dose on freezing persisted to the next day. When MPH (2.5–40 mg/kg) was administered immediately following an extinction session, mice that received MPH showed dose-dependent decreases in freezing during subsequent tests. MPH administered immediately after a 3-min extinction session or 4 h following the first extinction session did not cause significant differences in freezing. Together, these findings demonstrate that MPH can enhance extinction of fear and that this effect is sensitive to dose, time of injection, and duration of the extinction session. Because MPH is widely used in clinical treatments, these experiments suggest that the drug could be used in combination with behavioral therapies for patients with fear disorders. PMID:22251891

  16. Methylphenidate enhances extinction of contextual fear.

    PubMed

    Abraham, Antony D; Cunningham, Christopher L; Lattal, K Matthew

    2012-02-01

    Methylphenidate (MPH, Ritalin) is a norepinephrine and dopamine transporter blocker that is widely used in humans for treatment of attention deficit disorder and narcolepsy. Although there is some evidence that targeted microinjections of MPH may enhance fear acquisition, little is known about the effect of MPH on fear extinction. Here, we show that MPH, administered before or immediately following extinction of contextual fear, will enhance extinction retention in C57BL/6 mice. Animals that received MPH (2.5-10 mg/kg) before an extinction session showed decreased freezing response during extinction, and the effect of the 10 mg/kg dose on freezing persisted to the next day. When MPH (2.5-40 mg/kg) was administered immediately following an extinction session, mice that received MPH showed dose-dependent decreases in freezing during subsequent tests. MPH administered immediately after a 3-min extinction session or 4 h following the first extinction session did not cause significant differences in freezing. Together, these findings demonstrate that MPH can enhance extinction of fear and that this effect is sensitive to dose, time of injection, and duration of the extinction session. Because MPH is widely used in clinical treatments, these experiments suggest that the drug could be used in combination with behavioral therapies for patients with fear disorders. PMID:22251891

  17. The role of extinction in evolution

    NASA Technical Reports Server (NTRS)

    Raup, D. M.

    1994-01-01

    The extinction of species is not normally considered an important element of neodarwinian theory, in contrast to the opposite phenomenon, speciation. This is surprising in view of the special importance Darwin attached to extinction, and because the number of species extinctions in the history of life is almost the same as the number of originations; present-day biodiversity is the result of a trivial surplus of originations, cumulated over millions of years. For an evolutionary biologist to ignore extinction is probably as foolhardy as for a demographer to ignore mortality. The past decade has seen a resurgence of interest in extinction, yet research on the topic is still at a reconnaissance level, and our present understanding of its role in evolution is weak. Despite uncertainties, extinction probably contains three important elements. (i) For geographically widespread species, extinction is likely only if the killing stress is one so rare as to be beyond the experience of the species, and thus outside the reach of natural selection. (ii) The largest mass extinctions produce major restructuring of the biosphere wherein some successful groups are eliminated, allowing previously minor groups to expand and diversify. (iii) Except for a few cases, there is little evidence that extinction is selective in the positive sense argued by Darwin. It has generally been impossible to predict, before the fact, which species will be victims of an extinction event.

  18. The role of extinction in evolution.

    PubMed Central

    Raup, D M

    1994-01-01

    The extinction of species is not normally considered an important element of neodarwinian theory, in contrast to the opposite phenomenon, speciation. This is surprising in view of the special importance Darwin attached to extinction, and because the number of species extinctions in the history of life is almost the same as the number of originations; present-day biodiversity is the result of a trivial surplus of originations, cumulated over millions of years. For an evolutionary biologist to ignore extinction is probably as foolhardy as for a demographer to ignore mortality. The past decade has seen a resurgence of interest in extinction, yet research on the topic is still at a reconnaissance level, and our present understanding of its role in evolution is weak. Despite uncertainties, extinction probably contains three important elements. (i) For geographically widespread species, extinction is likely only if the killing stress is one so rare as to be beyond the experience of the species, and thus outside the reach of natural selection. (ii) The largest mass extinctions produce major restructuring of the biosphere wherein some successful groups are eliminated, allowing previously minor groups to expand and diversify. (iii) Except for a few cases, there is little evidence that extinction is selective in the positive sense argued by Darwin. It has generally been impossible to predict, before the fact, which species will be victims of an extinction event. PMID:8041694

  19. The ethics of reviving long extinct species.

    PubMed

    Sandler, Ronald

    2014-04-01

    There now appears to be a plausible pathway for reviving species that have been extinct for several decades, centuries, or even millennia. I conducted an ethical analysis of de-extinction of long extinct species. I assessed several possible ethical considerations in favor of pursuing de-extinction: that it is a matter of justice; that it would reestablish lost value; that it would create new value; and that society needs it as a conservation last resort. I also assessed several possible ethical arguments against pursuing de-extinction: that it is unnatural; that it could cause animal suffering; that it could be ecologically problematic or detrimental to human health; and that it is hubristic. There are reasons in favor of reviving long extinct species, and it can be ethically acceptable to do so. However, the reasons in favor of pursuing de-extinction do not have to do with its usefulness in species conservation; rather, they concern the status of revived species as scientific and technological achievements, and it would be ethically problematic to promote de-extinction as a significant conservation strategy, because it does not prevent species extinctions, does not address the causes of extinction, and could be detrimental to some species conservation efforts. Moreover, humanity does not have a responsibility or obligation to pursue de-extinction of long extinct species, and reviving them does not address any urgent problem. Therefore, legitimate ecological, political, animal welfare, legal, or human health concerns associated with a de-extinction (and reintroduction) must be thoroughly addressed for it to be ethically acceptable. PMID:24372907

  20. Falling for Clay Leaves.

    ERIC Educational Resources Information Center

    Kernan, Christine

    2002-01-01

    Describes an art project that integrated science and art education. Explains that students create ceramic bowls by using real leaves. Discusses the process of creating the ceramic bowls, including how to glaze the bowls. Includes a list of materials. (CMK)

  1. Cumulative frequency distribution of past species extinctions

    NASA Technical Reports Server (NTRS)

    Raup, D. M.

    1991-01-01

    Analysis of Sepkoski's compendium of the time ranges of 30,000+ taxa yields a mean duration of 28.4 ma for genera of fossil invertebrates. This converts to an average extinction rate of 3.5 percent per million years or about one percent every 286,000 years. Using survivorship techniques, these estimates can be converted to the species level, yielding a Phanerozoic average of one percent species extinction every 40,000 years. Variation in extinction rates through time is far greater than the null expectation of a homogeneous birth-death model and this reflects the well-known episodicity of extinction ranging from a few large mass extinctions to so-called background extinction. The observed variation in rates can be used to construct a cumulative frequency distribution of extinction intensity, and this distribution, in the form of a kill curve for species, shows the expected waiting times between extinction events of a given intensity. The kill curve is an average description of the extinction events of a given intensity. The kill curve is an average description of the extinction record and does not imply any cause or causes of extinction. The kill curve shows, among other things, that only about five percent of total species extinctions in the Phanerozoic were involved in the five largest mass extinctions. The other 95 percent were distributed among large and small events not normally called mass extinctions. As an exploration of the possibly absurd proposition that most past extinctions were produced by the effects of large-body impact, the kill curve for species was mapped on the comparable distribution for comet and asteroid impacts. The result is a curve predicting the species kill for a given size of impacting object (expressed as crater size). The results are reasonable in that impacts producing craters less than 30 km (diameter) cause negligible extinction but those producing craters 100-150 km (diameter) cause extinction of species in the range of 45

  2. Sexual selection protects against extinction.

    PubMed

    Lumley, Alyson J; Michalczyk, Łukasz; Kitson, James J N; Spurgin, Lewis G; Morrison, Catriona A; Godwin, Joanne L; Dickinson, Matthew E; Martin, Oliver Y; Emerson, Brent C; Chapman, Tracey; Gage, Matthew J G

    2015-06-25

    Reproduction through sex carries substantial costs, mainly because only half of sexual adults produce offspring. It has been theorized that these costs could be countered if sex allows sexual selection to clear the universal fitness constraint of mutation load. Under sexual selection, competition between (usually) males and mate choice by (usually) females create important intraspecific filters for reproductive success, so that only a subset of males gains paternity. If reproductive success under sexual selection is dependent on individual condition, which is contingent to mutation load, then sexually selected filtering through 'genic capture' could offset the costs of sex because it provides genetic benefits to populations. Here we test this theory experimentally by comparing whether populations with histories of strong versus weak sexual selection purge mutation load and resist extinction differently. After evolving replicate populations of the flour beetle Tribolium castaneum for 6 to 7 years under conditions that differed solely in the strengths of sexual selection, we revealed mutation load using inbreeding. Lineages from populations that had previously experienced strong sexual selection were resilient to extinction and maintained fitness under inbreeding, with some families continuing to survive after 20 generations of sib × sib mating. By contrast, lineages derived from populations that experienced weak or non-existent sexual selection showed rapid fitness declines under inbreeding, and all were extinct after generation 10. Multiple mutations across the genome with individually small effects can be difficult to clear, yet sum to a significant fitness load; our findings reveal that sexual selection reduces this load, improving population viability in the face of genetic stress. PMID:25985178

  3. Light extinction in the atmosphere

    SciTech Connect

    Laulainen, N.

    1992-06-01

    Atmospheric aerosol particles originating from natural sources, such as volcanos and sulfur-bearing gas emissions from the oceans, and from human sources, such as sulfur emissions from fossil fuel combustion and biomass burning, strongly affect visual air quality and are suspected to significantly affect radiative climate forcing of the planet. During the daytime, aerosols obscure scenic vistas, while at night they diminish our ability to observe stellar objects. Scattering of light is the main means by which aerosols attenuate and redistribute light in the atmosphere and by which aerosols can alter and reduce visibility and potentially modify the energy balance of the planet. Trends and seasonal variability of atmospheric aerosol loading, such as column-integrated light extinction or optical depth, and how they may affect potential climate change have been difficult to quantify because there have been few observations made of important aerosol optical parameters, such as optical depth, over the globe and over time and often these are of uneven quality. To address questions related to possible climate change, there is a pressing need to acquire more high-quality aerosol optical depth data. Extensive deployment of improved solar radiometers over the next few years will provide higher-quality extinction data over a wider variety of locations worldwide. An often overlooked source of turbidity data, however, is available from astronomical observations, particularly stellar photoelectric photometry observations. With the exception of the Project ASTRA articles published almost 20 years ago, few of these data ever appear in the published literature. This paper will review the current status of atmospheric extinction observations, as highlighted by the ASTRA work and augmented by more recent solar radiometry measurements.

  4. Comment on the extinct paradox

    NASA Technical Reports Server (NTRS)

    Levine, D. M.

    1983-01-01

    The extinction paradox is a contradiction between geometrical optics results which predict that at high frequencies the scattering cross section of an object should equal its geometrical cross section and rigorous scattering theory which shows that at high frequencies the scattering cross section approaches twice the geometrical cross section of the object. Confusion about the reason for this paradox persists today even though the nature of the paradox was correctly identified many years ago by Brillouin. The resolution of the paradox is restated and illustrated with an example, and then the implications to the interpretation of scattering cross sections are identified.

  5. Mass extinctions and missing matter

    NASA Technical Reports Server (NTRS)

    Stothers, R. B.

    1984-01-01

    The possible influence of 'invisible matter' on the solar system's comet halo, and therefore on quasi-periodic cometary bombardment of the earth and consequent mass extinctions, is briefly addressed. Invisible matter consisting of small or cold interstellar molecular clouds could significantly modulate the comet background flux, while invisible matter consisting of a large population of old, dead stars with a relatively small galactic concentration probably could not. It is also shown that the downward force exerted by the Galaxy will perturb the halo, but will not produce any periodicity.

  6. Microwave extinction characteristics of nanoparticle aggregates

    NASA Astrophysics Data System (ADS)

    Wu, Y. P.; Cheng, J. X.; Liu, X. X.; Wang, H. X.; Zhao, F. T.; Wen, W. W.

    2016-07-01

    Structure of nanoparticle aggregates plays an important role in microwave extinction capacity. The diffusion-limited aggregation model (DLA) for fractal growth is utilized to explore the possible structures of nanoparticle aggregates by computer simulation. Based on the discrete dipole approximation (DDA) method, the microwave extinction performance by different nano-carborundum aggregates is numerically analyzed. The effects of the particle quantity, original diameter, fractal structure, as well as orientation on microwave extinction are investigated, and also the extinction characteristics of aggregates are compared with the spherical nanoparticle in the same volume. Numerical results give out that proper aggregation of nanoparticle is beneficial to microwave extinction capacity, and the microwave extinction cross section by aggregated granules is better than that of the spherical solid one in the same volume.

  7. Extinction and Reinstatement of Phasic Dopamine Signals in the Nucleus Accumbens Core during Pavlovian Conditioning

    PubMed Central

    Sunsay, Ceyhun; Rebec, George V.

    2014-01-01

    The prediction-error model of dopamine (DA) signaling has largely been confirmed with various appetitive Pavlovian conditioning procedures and has been supported in tests of Pavlovian extinction. Studies have repeatedly shown, however, that extinction does not erase the original memory of conditioning as the prediction-error model presumes, putting the model at odds with contemporary views that treat extinction as an episode of learning rather than unlearning of conditioning. Here, we combined fast-scan cyclic voltammetry (FSCV) with appetitive Pavlovian conditioning to assess DA release directly during extinction and reinstatement. DA was monitored in the nucleus accumbens core (NAc), which plays a key role in reward processing. Following at least 4 daily sessions of 16 tone-food pairings, FSCV was performed while rats received additional tone-food pairings followed by tone alone presentations (i.e., extinction). Acquisition memory was reinstated with non-contingent presentations of reward and then tested with cue presentation. Tone-food pairings produced transient (1–3 s) DA release in response to tone. During extinction, the amplitude of the DA response decreased significantly. Following presentation of two non-contingent food pellets, subsequent tone presentation reinstated the DA signal. Our results support the prediction-error model for appetitive Pavlovian extinction but not for reinstatement. PMID:25111335

  8. The hypocretin/orexin system mediates the extinction of fear memories.

    PubMed

    Flores, África; Valls-Comamala, Victòria; Costa, Giulia; Saravia, Rocío; Maldonado, Rafael; Berrendero, Fernando

    2014-11-01

    Anxiety disorders are often associated with an inability to extinguish learned fear responses. The hypocretin/orexin system is involved in the regulation of emotional states and could also participate in the consolidation and extinction of aversive memories. Using hypocretin receptor-1 and hypocretin receptor-2 antagonists, hypocretin-1 and hypocretin-2 peptides, and hypocretin receptor-1 knockout mice, we investigated the role of the hypocretin system in cue- and context-dependent fear conditioning and extinction. Hypocretins were crucial for the consolidation of fear conditioning, and this effect was mainly observed in memories with a high emotional component. Notably, after the acquisition of fear memory, hypocretin receptor-1 blockade facilitated fear extinction, whereas hypocretin-1 administration impaired this extinction process. The extinction-facilitating effects of the hypocretin receptor-1 antagonist SB334867 were associated with increased expression of cFos in the basolateral amygdala and the infralimbic cortex. Intra-amygdala, but neither intra-infralimbic prefrontal cortex nor intra-dorsohippocampal infusion of SB334867 enhanced fear extinction. These results reveal a key role for hypocretins in the extinction of aversive memories and suggest that hypocretin receptor-1 blockade could represent a novel therapeutic target for the treatment of diseases associated with inappropriate retention of fear, such as post-traumatic stress disorder and phobias. PMID:24930888

  9. Aerosol extinction measurements with CO2-lidar

    NASA Technical Reports Server (NTRS)

    Hagard, Arne; Persson, Rolf

    1992-01-01

    With the aim to develop a model for infrared extinction due to aerosols in slant paths in the lower atmosphere we perform measurements with a CO2-lidar. Earlier measurements with a transmissometer along horizontal paths have been used to develop relations between aerosol extinction and meteorological parameters. With the lidar measurements we hope to develop corresponding relations for altitude profiles of the aerosol extinction in the infrared. An important application is prediction of detection range for infrared imaging systems.

  10. Increased perceived self-efficacy facilitates the extinction of fear in healthy participants

    PubMed Central

    Zlomuzica, Armin; Preusser, Friederike; Schneider, Silvia; Margraf, Jürgen

    2015-01-01

    Self-efficacy has been proposed as an important element of a successful cognitive behavioral treatment (CBT). Positive changes in perceived self-efficacy have been linked to an improved adaptive emotional and behavioral responding in the context of anxiety-provoking situations. Furthermore, a positive influence of increased self-efficacy on cognitive functions has been confirmed. The present study examined the effect of verbal persuasion on perceived self-efficacy and fear extinction. Healthy participants were subjected to a standardized differential fear conditioning paradigm. After fear acquisition, half of the participants received a verbal persuasion aimed at increasing perceived self-efficacy. The extinction of fear was assessed immediately thereafter on both the implicit and explicit level. Our results suggest that an increased perceived self-efficacy was associated with enhanced extinction, evidenced on the psychophysiological level and accompanied by more pronounced decrements in conditioned negative valence. Changes in extinction were not due to a decrease in overall emotional reactivity to conditioned stimuli (CS). In addition, debriefing participants about the false positive feedback did not affect the processing of already extinguished conditioned responses during a subsequent continued extinction phase. Our results suggest that positive changes in perceived self-efficacy can be beneficial for emotional learning. Findings are discussed with respect to strategies aimed at increasing extinction learning in the course of exposure-based treatments. PMID:26528152

  11. Increased perceived self-efficacy facilitates the extinction of fear in healthy participants.

    PubMed

    Zlomuzica, Armin; Preusser, Friederike; Schneider, Silvia; Margraf, Jürgen

    2015-01-01

    Self-efficacy has been proposed as an important element of a successful cognitive behavioral treatment (CBT). Positive changes in perceived self-efficacy have been linked to an improved adaptive emotional and behavioral responding in the context of anxiety-provoking situations. Furthermore, a positive influence of increased self-efficacy on cognitive functions has been confirmed. The present study examined the effect of verbal persuasion on perceived self-efficacy and fear extinction. Healthy participants were subjected to a standardized differential fear conditioning paradigm. After fear acquisition, half of the participants received a verbal persuasion aimed at increasing perceived self-efficacy. The extinction of fear was assessed immediately thereafter on both the implicit and explicit level. Our results suggest that an increased perceived self-efficacy was associated with enhanced extinction, evidenced on the psychophysiological level and accompanied by more pronounced decrements in conditioned negative valence. Changes in extinction were not due to a decrease in overall emotional reactivity to conditioned stimuli (CS). In addition, debriefing participants about the false positive feedback did not affect the processing of already extinguished conditioned responses during a subsequent continued extinction phase. Our results suggest that positive changes in perceived self-efficacy can be beneficial for emotional learning. Findings are discussed with respect to strategies aimed at increasing extinction learning in the course of exposure-based treatments. PMID:26528152

  12. Cycloheximide produces amnesia for extinction and reconsolidation in an appetitive odor discrimination task in rats.

    PubMed

    Gotthard, Gretchen Hanson; Knoppel, Alexandra B

    2010-01-01

    A considerable literature has shown deficits in memory resulting from the administration of protein synthesis inhibitors; however, most of the past literature in this field has focused on acquisition of new memory using aversively-motivated tasks. The effect of protein synthesis inhibition on appetitive learning and memory as well as extinction is less clear. The present study employed an appetitive odor discrimination paradigm to examine the effects of acute cycloheximide administration (1mg/kg) on reconsolidation and extinction. Male, Long-Evans adult rats were trained to discriminate between two odors (i.e., cocoa and cinnamon) and then received extinction trials following an intraperitoneal injection of cycloheximide or vehicle. Twenty-four hours later, rats were tested via one non-reinforced test trial. Results showed amnesia for extinction as well as original training (i.e., correct odor choice) in cycloheximide-injected rats in this appetitive task, while vehicle-injected controls showed good memory for extinction. These data add to a growing literature showing the importance of protein synthesis inhibition for extinction and reconsolidation in appetitive learning and memory. PMID:19761862

  13. Controlled cortical impact before or after fear conditioning does not affect fear extinction in mice.

    PubMed

    Sierra-Mercado, Demetrio; McAllister, Lauren M; Lee, Christopher C H; Milad, Mohammed R; Eskandar, Emad N; Whalen, Michael J

    2015-05-01

    Post-traumatic stress disorder (PTSD) is characterized in part by impaired extinction of conditioned fear. Traumatic brain injury (TBI) is thought to be a risk factor for development of PTSD. We tested the hypothesis that controlled cortical impact (CCI) would impair extinction of fear learned by Pavlovian conditioning, in mice. To mimic the scenarios in which TBI occurs prior to or after exposure to an aversive event, severe CCI was delivered to the left parietal cortex at one of two time points: (1) Prior to fear conditioning, or (2) after conditioning. Delay auditory conditioning was achieved by pairing a tone with a foot shock in "context A". Extinction training involved the presentation of tones in a different context (context B) in the absence of foot shock. Test for extinction memory was achieved by presentation of additional tones alone in context B over the following two days. In pre- or post-injury paradigms, CCI did not influence fear learning and extinction. Furthermore, CCI did not affect locomotor activity or elevated plus maze testing. Our results demonstrate that, within the time frame studied, CCI does not impair the acquisition and expression of conditioned fear or extinction memory. PMID:25721797

  14. Controlled cortical impact before or after fear conditioning does not affect fear extinction in mice

    PubMed Central

    Sierra-Mercado, Demetrio; McAllister, Lauren M.; Lee, Christopher C.H.; Milad, Mohammed R.; Eskandar, Emad N.; Whalen, Michael J.

    2015-01-01

    Post-traumatic stress disorder (PTSD) is characterized in part by impaired extinction of conditioned fear. Traumatic brain injury (TBI) is thought to be a risk factor for development of PTSD. We tested the hypothesis that controlled cortical impact (CCI) would impair extinction of fear learned by Pavlovian conditioning, in mice. To mimic the scenarios in which TBI occurs prior to or after exposure to an aversive event, severe CCI was delivered to the left parietal cortex at one of two time points: (1) Prior to fear conditioning, or (2) after conditioning. Delay auditory conditioning was achieved by pairing a tone with a foot shock in “context A”. Extinction training involved the presentation of tones in a different context (context B) in the absence of foot shock. Test for extinction memory was achieved by presentation of additional tones alone in context B over the following two days. In pre- or post-injury paradigms, CCI did not influence fear learning and extinction. Furthermore, CCI did not affect locomotor activity or elevated plus maze testing. Our results demonstrate that, within the time frame studied, CCI does not impair the acquisition and expression of conditioned fear or extinction memory. PMID:25721797

  15. Compound Stimulus Presentation and the Norepinephrine Reuptake Inhibitor Atomoxetine Enhance Long-Term Extinction of Cocaine-Seeking Behavior

    PubMed Central

    Janak, Patricia H; Bowers, M Scott; Corbit, Laura H

    2012-01-01

    Drug abstinence is frequently compromised when addicted individuals are re-exposed to environmental stimuli previously associated with drug use. Research with human addicts and in animal models has demonstrated that extinction learning (non-reinforced cue-exposure) can reduce the capacity of such stimuli to induce relapse, yet extinction therapies have limited long-term success under real-world conditions (Bouton, 2002; O'Brien, 2008). We hypothesized that enhancing extinction would reduce the later ability of drug-predictive cues to precipitate drug-seeking behavior. We, therefore, tested whether compound stimulus presentation and pharmacological treatments that augment noradrenergic activity (atomoxetine; norepinephrine reuptake inhibitor) during extinction training would facilitate the extinction of drug-seeking behaviors, thus reducing relapse. Rats were trained that the presentation of a discrete cue signaled that a lever press response would result in cocaine reinforcement. Rats were subsequently extinguished and spontaneous recovery of drug-seeking behavior following presentation of previously drug-predictive cues was tested 4 weeks later. We find that compound stimulus presentations or pharmacologically increasing noradrenergic activity during extinction training results in less future recovery of responding, whereas propranolol treatment reduced the benefit seen with compound stimulus presentation. These data may have important implications for understanding the biological basis of extinction learning, as well as for improving the outcome of extinction-based therapies. PMID:22089320

  16. Presence and Acquired Origin of Reduced Recall for Fear Extinction in PTSD: Results of a Twin Study

    PubMed Central

    Milad, Mohammed R.; Orr, Scott P.; Lasko, Natasha B.; Chang, Yuchiao; Rauch, Scott L.; Pitman, Roger K.

    2008-01-01

    Recall of fear extinction, which is thought to aid in recovery from a psychologically traumatic event, is hypothesized to be deficient in post-traumatic stress disorder (PTSD), but this has not yet been demonstrated in the laboratory, nor has its origin been investigated. To address these two issues, 14 pairs of monozygotic twins discordant for combat exposure, in 7 of which the combat-exposed twin had PTSD, underwent a two-day fear conditioning and extinction procedure. On Day 1, subjects viewed colored light conditioned stimuli, some of which were paired with mild electric shock, followed by extinction of the conditioned responses. On Day 2, recall of Day 1 extinction learning (i.e., extinction retention) was assessed. Skin conductance response (SCR) was the dependent measure. There were no group differences during acquisition or extinction learning. However, a significant PTSD Diagnosis (in the exposed twin) x combat Exposure interaction emerged during extinction recall, with the PTSD combat veterans having larger SCRs than their own co-twins, and than the non-PTSD combat veterans and their co-twins. These results indicate that retention of extinction of conditioned fear is deficient in PTSD. Furthermore, they support the conclusion that this deficit is acquired as a result of combat trauma leading to PTSD, rather than being a predisposing factor to developing PTSD upon the stress of combat. PMID:18313695

  17. Extinction by Single and Multiple Particles

    NASA Astrophysics Data System (ADS)

    Berg, Matthew; Sorensen, Christopher; Chakrabarti, Amit

    2008-03-01

    The combined effect of scattering and absorption is referred to as extinction and is responsible for the redistribution of radiant energy by a particle. This presentation will show that extinction is due to wave interference. Simulations of the energy flow caused by the interference graphically demonstrate how extinction redistributes the energy of incident light. Both single and multi-particle systems are considered. A conceptual, phase-based explanation is given that builds on previous work and illustrates the physical meaning of the optical theorem. Implications regarding the measurement of extinction are discussed.

  18. Mass extinctions vs. uniformitarianism in biological evolution

    SciTech Connect

    Bak, P.; Paczuski, M.

    1995-12-31

    It is usually believed that Darwin`s theory leads to a smooth gradual evolution, so that mass extinctions must be caused by external shocks. However, it has recently been argued that mass extinctions arise from the intrinsic dynamics of Darwinian evolution. Species become extinct when swept by intermittent avalanches propagating through the global ecology. These ideas are made concrete through studies of simple mathematical models of co-evolving species. The models exhibit self-organized criticality and describe some general features of the extinction pattern in the fossil record.

  19. Secondary extinction in Pavlovian fear conditioning

    PubMed Central

    Vurbic, Drina; Bouton, Mark E.

    2011-01-01

    Pavlov (1927/1960) reported that following the conditioning of several stimuli, extinction of one conditioned stimulus (CS) attenuated responding to others that had not undergone direct extinction. However, this secondary extinction effect has not been widely replicated in the contemporary literature. In three conditioned suppression experiments with rats, we further explored the phenomenon. In Experiment 1, we asked whether secondary extinction is more likely to occur with target CSs that have themselves undergone some prior extinction. A robust secondary extinction effect was obtained with a nonextinguished target CS. Experiment 2 showed that extinction of one CS was sufficient to reduce renewal of a second CS when it was tested in a neutral (nonextinction) context. In Experiment 3, secondary extinction was observed in groups that initially received intermixed conditioning trials with the target and nontarget CSs, but not in groups that received conditioning of the two CSs in separate sessions. The results are consistent with the hypothesis that CSs must be associated with a common temporal context during conditioning for secondary extinction to occur. PMID:21286897

  20. Extinction of opiate reward reduces dendritic arborization and c-Fos expression in the nucleus accumbens core.

    PubMed

    Leite-Morris, Kimberly A; Kobrin, Kendra L; Guy, Marsha D; Young, Angela J; Heinrichs, Stephen C; Kaplan, Gary B

    2014-04-15

    Recurrent opiate use combined with environmental cues, in which the drug was administered, provokes cue-induced drug craving and conditioned drug reward. Drug abuse craving is frequently linked with stimuli from a prior drug-taking environment via classical conditioning and associative learning. We modeled the conditioned morphine reward process by using acquisition and extinction of conditioned place preference (CPP) in C57BL/6 mice. Mice were trained to associate a morphine injection with a drug context using a classical conditioning paradigm. In morphine conditioning (0, 0.25, 0.5, 1, 5, or 10 mg/kg) experimental mice acquired a morphine CPP dose response with 10mg/kg as most effective. During morphine CPP extinction experiments, mice were divided into three test groups: morphine CPP followed by extinction training, morphine CPP followed by sham extinction, and saline controls. Extinction of morphine CPP developed within one extinction experiment (4 days) that lasted over two more trials (another 8 days). However, the morphine CPP/sham extinction group retained a place preference that endured through all three extinction trials. Brains were harvested following CPP extinction and processed using Golgi-Cox impregnation. Changes in dendritic morphology and spine quantity were examined in the nucleus accumbens (NAc) Core and Shell neurons. In the NAcCore only, morphine CPP/extinguished mice produced less dendritic arborization, and a decrease in neuronal activity marker c-Fos compared to the morphine CPP/sham extinction group. Extinction of morphine CPP is associated with decreased structural complexity of dendrites in the NAcCore and may represent a substrate for learning induced structural plasticity relevant to addiction. PMID:24406724

  1. Lumbar lordosis of extinct hominins.

    PubMed

    Been, Ella; Gómez-Olivencia, Asier; Kramer, Patricia A

    2012-01-01

    The lordotic curvature of the lumbar spine (lumbar lordosis) in humans is a critical component in the ability to achieve upright posture and bipedal gait. Only general estimates of the lordotic angle (LA) of extinct hominins are currently available, most of which are based on the wedging of the vertebral bodies. Recently, a new method for calculating the LA in skeletal material has become available. This method is based on the relationship between the lordotic curvature and the orientation of the inferior articular processes relative to vertebral bodies in the lumbar spines of living primates. Using this relationship, we developed new regression models in order to calculate the LAs in hominins. The new models are based on primate group-means and were used to calculate the LAs in the spines of eight extinct hominins. The results were also compared with the LAs of modern humans and modern nonhuman apes. The lordotic angles of australopithecines (41° ± 4), H. erectus (45°) and fossil H. sapiens (54° ± 14) are similar to those of modern humans (51° ± 11). This analysis confirms the assumption that human-like lordotic curvature was a morphological change that took place during the acquisition of erect posture and bipedalism as the habitual form of locomotion. Neandertals have smaller lordotic angles (LA = 29° ± 4) than modern humans, but higher angles than nonhuman apes (22° ± 3). This suggests possible subtle differences in Neandertal posture and locomotion from that of modern humans. PMID:22052243

  2. Effect of ablated hippocampal neurogenesis on the formation and extinction of contextual fear memory

    PubMed Central

    Ko, Hyoung-Gon; Jang, Deok-Jin; Son, Junehee; Kwak, Chuljung; Choi, Jun-Hyeok; Ji, Young-Hoon; Lee, Yun-Sil; Son, Hyeon; Kaang, Bong-Kiun

    2009-01-01

    Newborn neurons in the subgranular zone (SGZ) of the hippocampus incorporate into the dentate gyrus and mature. Numerous studies have focused on hippocampal neurogenesis because of its importance in learning and memory. However, it is largely unknown whether hippocampal neurogenesis is involved in memory extinction per se. Here, we sought to examine the possibility that hippocampal neurogenesis may play a critical role in the formation and extinction of hippocampus-dependent contextual fear memory. By methylazoxymethanol acetate (MAM) or gamma-ray irradiation, hippocampal neurogenesis was impaired in adult mice. Under our experimental conditions, only a severe impairment of hippocampal neurogenesis inhibited the formation of contextual fear memory. However, the extinction of contextual fear memory was not affected. These results suggest that although adult newborn neurons contribute to contextual fear memory, they may not be involved in the extinction or erasure of hippocampus-dependent contextual fear memory. PMID:19138433

  3. Phylogenetic Clustering of Origination and Extinction across the Late Ordovician Mass Extinction

    PubMed Central

    Krug, Andrew Z.; Patzkowsky, Mark E.

    2015-01-01

    Mass extinctions can have dramatic effects on the trajectory of life, but in some cases the effects can be relatively small even when extinction rates are high. For example, the Late Ordovician mass extinction is the second most severe in terms of the proportion of genera eliminated, yet is noted for the lack of ecological consequences and shifts in clade dominance. By comparison, the end-Cretaceous mass extinction was less severe but eliminated several major clades while some rare surviving clades diversified in the Paleogene. This disconnect may be better understood by incorporating the phylogenetic relatedness of taxa into studies of mass extinctions, as the factors driving extinction and recovery are thought to be phylogenetically conserved and should therefore promote both origination and extinction of closely related taxa. Here, we test whether there was phylogenetic selectivity in extinction and origination using brachiopod genera from the Middle Ordovician through the Devonian. Using an index of taxonomic clustering (RCL) as a proxy for phylogenetic clustering, we find that A) both extinctions and originations shift from taxonomically random or weakly clustered within families in the Ordovician to strongly clustered in the Silurian and Devonian, beginning with the recovery following the Late Ordovician mass extinction, and B) the Late Ordovician mass extinction was itself only weakly clustered. Both results stand in stark contrast to Cretaceous-Cenozoic bivalves, which showed significant levels of taxonomic clustering of extinctions in the Cretaceous, including strong clustering in the mass extinction, but taxonomically random extinctions in the Cenozoic. The contrasting patterns between the Late Ordovician and end-Cretaceous events suggest a complex relationship between the phylogenetic selectivity of mass extinctions and the long-term phylogenetic signal in origination and extinction patterns. PMID:26658946

  4. Phylogenetic Clustering of Origination and Extinction across the Late Ordovician Mass Extinction.

    PubMed

    Krug, Andrew Z; Patzkowsky, Mark E

    2015-01-01

    Mass extinctions can have dramatic effects on the trajectory of life, but in some cases the effects can be relatively small even when extinction rates are high. For example, the Late Ordovician mass extinction is the second most severe in terms of the proportion of genera eliminated, yet is noted for the lack of ecological consequences and shifts in clade dominance. By comparison, the end-Cretaceous mass extinction was less severe but eliminated several major clades while some rare surviving clades diversified in the Paleogene. This disconnect may be better understood by incorporating the phylogenetic relatedness of taxa into studies of mass extinctions, as the factors driving extinction and recovery are thought to be phylogenetically conserved and should therefore promote both origination and extinction of closely related taxa. Here, we test whether there was phylogenetic selectivity in extinction and origination using brachiopod genera from the Middle Ordovician through the Devonian. Using an index of taxonomic clustering (RCL) as a proxy for phylogenetic clustering, we find that A) both extinctions and originations shift from taxonomically random or weakly clustered within families in the Ordovician to strongly clustered in the Silurian and Devonian, beginning with the recovery following the Late Ordovician mass extinction, and B) the Late Ordovician mass extinction was itself only weakly clustered. Both results stand in stark contrast to Cretaceous-Cenozoic bivalves, which showed significant levels of taxonomic clustering of extinctions in the Cretaceous, including strong clustering in the mass extinction, but taxonomically random extinctions in the Cenozoic. The contrasting patterns between the Late Ordovician and end-Cretaceous events suggest a complex relationship between the phylogenetic selectivity of mass extinctions and the long-term phylogenetic signal in origination and extinction patterns. PMID:26658946

  5. Constraints on Enhanced Extinction Resulting from Extinction Treatment in the Presence of an Added Excitor

    ERIC Educational Resources Information Center

    Urcelay, Gonzalo P.; Lipatova, Olga; Miller, Ralph R.

    2009-01-01

    Three Pavlovian fear conditioning experiments with rats as subjects explored the effect of extinction in the presence of a concurrent excitor. Our aim was to explore this particular treatment, documented in previous studies to deepen extinction, with novel control groups to shed light on the processes involved in extinction. Relative to subjects…

  6. Extinction and the spatial dynamics of biodiversity

    PubMed Central

    Jablonski, David

    2008-01-01

    The fossil record amply shows that the spatial fabric of extinction has profoundly shaped the biosphere; this spatial dimension provides a powerful context for integration of paleontological and neontological approaches. Mass extinctions evidently alter extinction selectivity, with many factors losing effectiveness except for a positive relation between survivorship and geographic range at the clade level (confirmed in reanalyses of end-Cretaceous extinction data). This relation probably also holds during “normal” times, but changes both slope and intercept with increasing extinction. The strong geographical component to clade dynamics can obscure causation in the extinction of a feature or a clade, owing to hitchhiking effects on geographic range, so that multifactorial analyses are needed. Some extinctions are spatially complex, and regional extinctions might either reset a diversity ceiling or create a diversification debt open to further diversification or invasion. Evolutionary recoveries also exhibit spatial dynamics, including regional differences in invasibilty, and expansion of clades from the tropics fuels at least some recoveries, as well as biodiversity dynamics during normal times. Incumbency effects apparently correlate more closely with extinction intensities than with standing diversities, so that regions with higher local and global extinctions are more subject to invasion; the latest Cenozoic temperate zones evidently received more invaders than the tropics or poles, but this dynamic could shift dramatically if tropical diversity is strongly depleted. The fossil record can provide valuable insights, and their application to present-day issues will be enhanced by partitioning past and present-day extinctions by driving mechanism rather than emphasizing intensity. PMID:18695229

  7. D-cycloserine to enhance extinction of cue-elicited craving for alcohol: a translational approach

    PubMed Central

    MacKillop, J; Few, L R; Stojek, M K; Murphy, C M; Malutinok, S F; Johnson, F T; Hofmann, S G; McGeary, J E; Swift, R M; Monti, P M

    2015-01-01

    Cue-elicited craving for alcohol is well established but extinction-based treatment to extinguish this response has generated only modest positive outcomes in clinical trials. Basic and clinical research suggests that D-cycloserine (DCS) enhances extinction to fear cues under certain conditions. However, it remains unclear whether DCS would also accelerate extinction of cue-elicited craving for alcohol. The goal of the current study was to examine whether, compared with placebo (PBO), DCS enhanced extinction of cue-elicited craving among treatment-seeking individuals with alcohol use disorders (AUDs). Participants were administered DCS (50 mg) or PBO 1 h before an alcohol extinction paradigm in a simulated bar environment on two occasions. The extinction procedures occurred 1 week apart and were fully integrated into outpatient treatment. Subjective craving for alcohol was the primary variable of interest. Follow-up cue reactivity sessions were conducted 1 week and 3 weeks later to ascertain persisting DCS effects. Drinking outcomes and tolerability were also examined. DCS was associated with augmented reductions in alcohol craving to alcohol cues during the first extinction session and these effects persisted through all subsequent sessions, suggesting facilitation of extinction. Participants in the DCS condition reported significant short-term reductions in drinking, although these did not persist to follow-up, and found the medication highly tolerable. These findings provide evidence that DCS enhances extinction of cue-elicited craving for alcohol in individuals with AUDs in the context of outpatient treatment. The potential clinical utility of DCS is discussed, including methodological considerations and context-dependent learning. PMID:25849983

  8. Serotonin transporter polyadenylation polymorphism modulates the retention of fear extinction memory

    PubMed Central

    Hartley, Catherine A.; McKenna, Morgan C.; Salman, Rabia; Holmes, Andrew; Casey, B. J.; Glatt, Charles E.

    2012-01-01

    Growing evidence suggests serotonin's role in anxiety and depression is mediated by its effects on learned fear associations. Pharmacological and genetic manipulations of serotonin signaling in mice alter the retention of fear extinction learning, which is inversely associated with anxious temperament in mice and humans. Here, we test whether genetic variation in serotonin signaling in the form of a common human serotonin transporter polyadenylation polymorphism (STPP/rs3813034) is associated with spontaneous fear recovery after extinction. We show that the risk allele of this polymorphism is associated with impaired retention of fear extinction memory and heightened anxiety and depressive symptoms. These STPP associations in humans mirror the phenotypic effects of serotonin transporter knockout in mice, highlighting the STPP as a potential genetic locus underlying interindividual differences in serotonin transporter function in humans. Furthermore, we show that the serotonin transporter polyadenylation profile associated with the STPP risk allele is altered through the chronic administration of fluoxetine, a treatment that also facilitates retention of extinction learning. The propensity to form persistent fear associations due to poor extinction recall may be an intermediate phenotype mediating the effects of genetic variation in serotonergic function on anxiety and depression. The consistency and specificity of these data across species provide robust support for this hypothesis and suggest that the little-studied STPP may be an important risk factor for mood and anxiety disorders in humans. PMID:22431634

  9. Orexin/hypocretin receptor 1 signaling mediates Pavlovian cue-food conditioning and extinction.

    PubMed

    Keefer, Sara E; Cole, Sindy; Petrovich, Gorica D

    2016-08-01

    Learned food cues can drive feeding in the absence of hunger, and orexin/hypocretin signaling is necessary for this type of overeating. The current study examined whether orexin also mediates cue-food learning during the acquisition and extinction of these associations. In Experiment 1, rats underwent two sessions of Pavlovian appetitive conditioning, consisting of tone-food presentations. Prior to each session, rats received either the orexin 1 receptor antagonist SB-334867 (SB) or vehicle systemically. SB treatment did not affect conditioned responses during the first conditioning session, measured as food cup behavior during the tone and latency to approach the food cup after the tone onset, compared to the vehicle group. During the second conditioning session, SB treatment attenuated learning. All groups that received SB, prior to either the first or second conditioning session, displayed significantly less food cup behavior and had longer latencies to approach the food cup after tone onset compared to the vehicle group. These findings suggest orexin signaling at the 1 receptor mediates the consolidation and recall of cue-food acquisition. In Experiment 2, another group of rats underwent tone-food conditioning sessions (drug free), followed by two extinction sessions under either SB or vehicle treatment. Similar to Experiment 1, SB did not affect conditioned responses during the first session. During the second extinction session, the group that received SB prior to the first extinction session, but vehicle prior to the second, expressed conditioned food cup responses longer after tone offset, when the pellets were previously delivered during conditioning, and maintained shorter latencies to approach the food cup compared to the other groups. The persistence of these conditioned behaviors indicates impairment in extinction consolidation due to SB treatment during the first extinction session. Together, these results demonstrate an important role for orexin

  10. Combined Neuropeptide S and D-Cycloserine Augmentation Prevents the Return of Fear in Extinction-Impaired Rodents: Advantage of Dual versus Single Drug Approaches

    PubMed Central

    Maurer, Verena; Murphy, Conor; Schmuckermair, Claudia; Muigg, Patrick; Neumann, Inga D.; Whittle, Nigel

    2016-01-01

    Background: Despite its success in treating specific anxiety disorders, the effect of exposure therapy is limited by problems with tolerability, treatment resistance, and fear relapse after initial response. The identification of novel drug targets facilitating fear extinction in clinically relevant animal models may guide improved treatment strategies for these disorders in terms of efficacy, acceleration of fear extinction, and return of fear. Methods: The extinction-facilitating potential of neuropeptide S, D-cycloserine, and a benzodiazepine was investigated in extinction-impaired high anxiety HAB rats and 129S1/SvImJ mice using a classical cued fear conditioning paradigm followed by extinction training and several extinction test sessions to study fear relapse. Results: Administration of D-cycloserine improved fear extinction in extinction-limited, but not in extinction-deficient, rodents compared with controls. Preextinction neuropeptide S caused attenuated fear responses in extinction-deficient 129S1/SvImJ mice at extinction training onset and further reduced freezing during this session. While the positive effects of either D-cycloserine or neuropeptide S were not persistent in 129S1/SvImJ mice after 10 days, the combination of preextinction neuropeptide S with postextinction D-cycloserine rendered the extinction memory persistent and context independent up to 5 weeks after extinction training. This dual pharmacological adjunct to extinction learning also protected against fear reinstatement in 129S1/SvImJ mice. Conclusions: By using the potentially nonsedative anxiolytic neuropeptide S and the cognitive enhancer D-cycloserine to facilitate deficient fear extinction, we provide here the first evidence of a purported efficacy of a dual over a single drug approach. This approach may render exposure sessions less aversive and more efficacious for patients, leading to enhanced protection from fear relapse in the long term. PMID:26625894

  11. Mass extinctions: Ecological selectivity and primary production

    NASA Astrophysics Data System (ADS)

    Rhodes, Melissa Clark; Thayer, Charles W.

    1991-09-01

    If mass extinctions were caused by reduced primary productivity, then extinctions should be concentrated among animals with starvation-susceptible feeding modes, active lifestyles, and high-energy budgets. The stratigraphic ranges (by stage) of 424 genera of bivalves and 309 genera of articulate brachiopods suggest that there was an unusual reduction of primary productivity at the Cretaceous/Tertiary (K/T) boundary extinction. For bivalves at the K/T, there were (1) selective extinction of suspension feeders and other susceptible trophic categories relative to deposit feeders and other resistant categories, and (2) among suspension feed-ers, selective extinction of bivalves with active locomotion. During the Permian-Triassic (P/Tr) extinction and Jurassic background time, extinction rates among suspension feeders were greater for articulate brachiopods than for bivalves. But during the K/T event, extinction rates of articulates and suspension-feeding bivalves equalized, possibly because the low-energy budgets of articulates gave them an advantage when food was scarce.

  12. Extinction-Induced Variability in Human Behavior

    ERIC Educational Resources Information Center

    Kinloch, Jennifer M.; Foster, T. Mary; McEwan, James S. A.

    2009-01-01

    Participants earned points by pressing a computer space bar (Experiment 1) or forming rectangles on the screen with the mouse (Experiment 2) under differential-reinforcement-of-low-rate schedules, followed by extinction. Variability in interresponse time (the contingent dimension) increased during extinction, as for Morgan and Lee (1996);…

  13. Immediate extinction promotes the return of fear.

    PubMed

    Merz, Christian J; Hamacher-Dang, Tanja C; Wolf, Oliver T

    2016-05-01

    Accumulating evidence indicates that immediate extinction is less effective than delayed extinction in attenuating the return of fear. This line of fear conditioning research impacts the proposed onset of psychological interventions after threatening situations. In the present study, forty healthy men were investigated in a differential fear conditioning paradigm with fear acquisition in context A, extinction in context B, followed by retrieval testing in both contexts 24h later to test fear renewal. Differently coloured lights served as conditioned stimuli (CS): two CS (CS+) were paired with an electrical stimulation that served as unconditioned stimulus, the third CS was never paired (CS-). Extinction took place immediately after fear acquisition or 24h later. One CS+ was extinguished whereas the second CS+ remained unextinguished to control for different time intervals between fear acquisition and retrieval testing. Immediate extinction led to larger skin conductance responses during fear retrieval to both the extinguished and unextinguished CS relative to the CS-, indicating a stronger return of fear compared to delayed extinction. Taken together, immediate extinction is less potent than delayed extinction and is associated with a stronger renewal effect. Thus, the time-point of psychological interventions relative to the offset of threatening situations needs to be carefully considered to prevent relapses. PMID:26995309

  14. Survival without recovery after mass extinctions

    PubMed Central

    Jablonski, David

    2002-01-01

    Because many survivors of mass extinctions do not participate in postrecovery diversifications, and therefore fall into a pattern that can be termed “Dead Clade Walking” (DCW), the effects of mass extinctions extend beyond the losses observed during the event itself. Analyses at two taxonomic levels provide a first-order test of the prevalence of DCWs by using simple and very conservative operational criteria. For four of the Big Five mass extinctions of the Phanerozoic, the marine genera that survived the extinction suffered ≈10–20% attrition in the immediately following geologic stage that was significantly greater than the losses sustained in preextinction stages. The stages immediately following the three Paleozoic mass extinctions also account for 17% of all order-level losses in marine invertebrates over that interval, which is, again, significantly greater than that seen for the other stratigraphic stages (no orders are lost immediately after the end-Triassic or end-Cretaceous mass extinctions). DCWs are not evenly distributed among four regional molluscan time-series following the end-Cretaceous extinction, demonstrating the importance of spatial patterns in recovery dynamics. Although biotic interactions have been invoked to explain the differential postextinction success of clades, such hypotheses must be tested against alternatives that include stochastic processes in low-diversity lineages—which is evidently not a general explanation for the ordinal DCW patterns, because postextinction fates are not related to the size of extinction bottlenecks in Paleozoic orders—and ongoing physical environmental changes. PMID:12060760

  15. Current extinction rates of reptiles and amphibians

    PubMed Central

    Alroy, John

    2015-01-01

    There is broad concern that a mass extinction of amphibians and reptiles is now underway. Here I apply an extremely conservative Bayesian method to estimate the number of recent amphibian and squamate extinctions in nine important tropical and subtropical regions. The data stem from a combination of museum collection databases and published site surveys. The method computes an extinction probability for each species by considering its sighting frequency and last sighting date. It infers hardly any extinction when collection dates are randomized and it provides underestimates when artificial extinction events are imposed. The method also appears to be insensitive to trends in sampling; therefore, the counts it provides are absolute minimums. Extinctions or severe population crashes have accumulated steadily since the 1970s and 1980s, and at least 3.1% of frog species have already disappeared. Based on these data and this conservative method, the best estimate of the global grand total is roughly 200 extinctions. Consistent with previous results, frog losses are heavy in Latin America, which has been greatly affected by the pathogenic chytrid fungus Batrachochytrium dendrobatidis. Extinction rates are now four orders-of-magnitude higher than background, and at least another 6.9% of all frog species may be lost within the next century, even if there is no acceleration in the growth of environmental threats. PMID:26438855

  16. TROPICAL MASS EXTINCTIONS AND THE SCIENTIFIC METHOD

    EPA Science Inventory

    Kangas (1992), Undiscovered species and the falsifiability of the tropical mass extinction hypotheses, ESA Bulletin 73:124-125, 1992, argues that there is a paradox concerning the mass extinctions projected from current rates of tropical deforestation. he parameters; for a given ...

  17. Current extinction rates of reptiles and amphibians.

    PubMed

    Alroy, John

    2015-10-20

    There is broad concern that a mass extinction of amphibians and reptiles is now underway. Here I apply an extremely conservative Bayesian method to estimate the number of recent amphibian and squamate extinctions in nine important tropical and subtropical regions. The data stem from a combination of museum collection databases and published site surveys. The method computes an extinction probability for each species by considering its sighting frequency and last sighting date. It infers hardly any extinction when collection dates are randomized and it provides underestimates when artificial extinction events are imposed. The method also appears to be insensitive to trends in sampling; therefore, the counts it provides are absolute minimums. Extinctions or severe population crashes have accumulated steadily since the 1970s and 1980s, and at least 3.1% of frog species have already disappeared. Based on these data and this conservative method, the best estimate of the global grand total is roughly 200 extinctions. Consistent with previous results, frog losses are heavy in Latin America, which has been greatly affected by the pathogenic chytrid fungus Batrachochytrium dendrobatidis. Extinction rates are now four orders-of-magnitude higher than background, and at least another 6.9% of all frog species may be lost within the next century, even if there is no acceleration in the growth of environmental threats. PMID:26438855

  18. Periodicity of extinction: A 1988 update

    NASA Technical Reports Server (NTRS)

    Sepkowski, J. John, Jr.

    1988-01-01

    The hypothesis that events of mass extinction recur periodically at approximately 26 my intervals is an empirical claim based on analysis of data from the fossil record. The hypothesis has become closely linked with catastrophism because several events in the periodic series are associated with evidence of extraterrestrial impacts, and terrestrial forcing mechanisms with long, periodic recurrences are not easily conceived. Astronomical mechanisms that have been hypothesized include undetected solar companions and solar oscillation about the galactic plane, which induce comet showers and result in impacts on Earth at regular intervals. Because these mechanisms are speculative, they have been the subject of considerable controversy, as has the hypothesis of periodicity of extinction. In response to criticisms and uncertainties, a data base was developed on times of extinction of marine animal genera. A time series is given and analyzed with 49 sample points for the per-genus extinction rate from the Late Permian to the Recent. An unexpected pattern in the data is the uniformity of magnitude of many of the periodic extinction events. Observations suggest that the sequence of extinction events might be the result of two sets of mechanisms: a periodic forcing that normally induces only moderate amounts of extinction, and independent incidents or catastrophes that, when coincident with the periodic forcing, amplify its signal and produce major-mass extinctions.

  19. Long-Term Maintenance of Immediate or Delayed Extinction Is Determined by the Extinction-Test Interval

    ERIC Educational Resources Information Center

    Johnson, Justin S.; Escobar, Martha; Kimble, Whitney L.

    2010-01-01

    Short acquisition-extinction intervals (immediate extinction) can lead to either more or less spontaneous recovery than long acquisition-extinction intervals (delayed extinction). Using rat subjects, we observed less spontaneous recovery following immediate than delayed extinction (Experiment 1). However, this was the case only if a relatively…

  20. Neurosubstrates and mechanisms underlying the extinction of associative motor memory.

    PubMed

    Hu, Chen; Zhang, Li-Bin; Chen, Hao; Xiong, Yan; Hu, Bo

    2015-12-01

    Eyeblink conditioning is one of the most commonly used model systems to investigate the neural mechanisms underlying associative motor learning. It is well established that the acquisition and retention of conditioned eyeblink responses (CRs) involve neural plasticity in both the cerebellar cortex and deep cerebellar nuclei (DCN). Nevertheless, how learned CRs are extinguished remains relatively unclear. It has been suggested that extinguished CRs can recur spontaneously, can reappear by exposure to certain stimuli, and can be reacquired in fewer training trials than originally needed, indicating that associative motor memory is not merely erased by extinction training. Instead, the motor memory is preserved to some degree. Herein, we reviewed recent experimental findings demonstrating that the cerebellum subserves the preservation of learned CRs. In addition, several lines of evidence have suggested that forebrain structures (i.e., the medial prefrontal cortex and hippocampus) are involved in the CR extinction. We proposed possible mechanisms related to how preserved motor memory in the cerebellum is inhibited by the forebrain structures via the amygdalar complex. PMID:26209112

  1. Preventing the Next Mass Extinction: Ethical Obligations

    SciTech Connect

    Tonn, Bruce Edward

    2009-11-01

    This paper presents a framework to judge whether we are meeting our ethical responsibilities for preventing massive species extinction. The framework is a generalization from another framework, one that addresses ethical responsibilities related to preventing premature, involuntary human deaths from environmental risks and the extinction of the human race. The resulting ethical risk standards are quite stringent and it is argued that we are nowhere close to meeting any standards, except in the cases of human extinction and extinction of all life on earth, which are met by chance, not by design. Much work is needed to build the 'technology' needed to estimate probabilities associated with massive losses of human life and species extinction over the suggested 1000 year planning horizon.

  2. Mass extinction in poorly known taxa

    PubMed Central

    Régnier, Claire; Achaz, Guillaume; Lambert, Amaury; Cowie, Robert H.; Bouchet, Philippe; Fontaine, Benoît

    2015-01-01

    Since the 1980s, many have suggested we are in the midst of a massive extinction crisis, yet only 799 (0.04%) of the 1.9 million known recent species are recorded as extinct, questioning the reality of the crisis. This low figure is due to the fact that the status of very few invertebrates, which represent the bulk of biodiversity, have been evaluated. Here we show, based on extrapolation from a random sample of land snail species via two independent approaches, that we may already have lost 7% (130,000 extinctions) of the species on Earth. However, this loss is masked by the emphasis on terrestrial vertebrates, the target of most conservation actions. Projections of species extinction rates are controversial because invertebrates are essentially excluded from these scenarios. Invertebrates can and must be assessed if we are to obtain a more realistic picture of the sixth extinction crisis. PMID:26056308

  3. Extinctions in ancient and modern seas.

    PubMed

    Harnik, Paul G; Lotze, Heike K; Anderson, Sean C; Finkel, Zoe V; Finnegan, Seth; Lindberg, David R; Liow, Lee Hsiang; Lockwood, Rowan; McClain, Craig R; McGuire, Jenny L; O'Dea, Aaron; Pandolfi, John M; Simpson, Carl; Tittensor, Derek P

    2012-11-01

    In the coming century, life in the ocean will be confronted with a suite of environmental conditions that have no analog in human history. Thus, there is an urgent need to determine which marine species will adapt and which will go extinct. Here, we review the growing literature on marine extinctions and extinction risk in the fossil, historical, and modern records to compare the patterns, drivers, and biological correlates of marine extinctions at different times in the past. Characterized by markedly different environmental states, some past periods share common features with predicted future scenarios. We highlight how the different records can be integrated to better understand and predict the impact of current and projected future environmental changes on extinction risk in the ocean. PMID:22889500

  4. Leaves: Nature's Solar Collectors

    ERIC Educational Resources Information Center

    Isabelle, Aaron D.; de Groot, Cornelis

    2009-01-01

    One of the most captivating things about plants is the way they capture the Sun's energy, but this can be a difficult topic to cover with elementary students. Therefore, to help students to make a concrete connection to this abstract concept, this series of solar-energy lessons focuses on leaves and how they act as "solar collectors." As students…

  5. Bemoans, Belittles, and Leaves

    ERIC Educational Resources Information Center

    Lynch-Biniek, Amy

    2005-01-01

    In this article, I examine Lynn Truss's book of punctuation rules and faux pas, "Eats, Shoots & Leaves," contemplating the complex relationships among class, academics, and language snobbery. I don't refute Truss's lessons on punctuation. Instead, I use her text as a jumping-off point for discussion of the social issues embedded in her guide and…

  6. Maternity Leave in Taiwan

    PubMed Central

    Feng, Joyce Yen; Han, Wen-Jui

    2011-01-01

    Using the first nationally representative birth cohort study in Taiwan, this paper examines the role that maternity leave policy in Taiwan plays in the timing of mothers returning to work after giving birth, as well as the extent to which this timing is linked to the amount of time mothers spend with their children and their use of breast milk versus formula. We found that the time when mothers returned to work coincided with the duration of guaranteed leave. In particular, mothers with a labor pension plan resumed work significantly earlier than mothers with no pension plan, and mothers with no pension plan returned to work significantly later than those with pension plans. The short leave of absence guaranteed under existing policies translated into mothers spending less time with their children and being more likely to exclusively use formula by 6 months after birth. In contrast, mothers who resumed work later than 6 months after birth were more likely to have not worked before birth or to have quit their jobs during pregnancy. Implications and recommendations for parental leave policy in Taiwan are discussed. PMID:21603074

  7. Maternity Leave in Taiwan

    ERIC Educational Resources Information Center

    Feng, Joyce Yen; Han, Wen-Jui

    2010-01-01

    Using the first nationally representative birth cohort study in Taiwan, this paper examines the role that maternity leave policy in Taiwan plays in the timing of mothers returning to work after giving birth, as well as the extent to which this timing is linked to the amount of time mothers spend with their children and their use of breast milk…

  8. Predicting extinction debt from community patterns.

    PubMed

    Kitzes, Justin; Harte, John

    2015-08-01

    A significant challenge in both measuring and predicting species extinction rates at global and local scales is the possibility of extinction debt, time-delayed extinctions that occur gradually following an initial impact. Here we examine how relative abundance distributions and spatial aggregation combine to influence the likely magnitude of future extinction debt following habitat loss or climate-driven range contraction. Our analysis is based on several fundamental premises regarding abundance distributions, most importantly that species abundances immediately following habitat loss are a sample from an initial relative abundance distribution and that the long-term, steady-state form of the species abundance distribution is a property of the biology of a community and not of area. Under these two hypotheses, the results show that communities following canonical lognormal and broken-stick abundance distributions are prone to exhibit extinction debt, especially when species exhibit low spatial aggregation. Conversely, communities following a logseries distribution with a constant Fisher's α parameter never demonstrate extinction debt and often show an "immigration credit," in which species richness rises in the long term following an initial decrease. An illustration of these findings in 25 biodiversity hotspots suggests a negligible immediate extinction rate for bird communities and eventual extinction debts of 30-50% of initial species richness, whereas plant communities are predicted to immediately lose 5-15% of species without subsequent extinction debt. These results shed light on the basic determinants of extinction debt and provide initial indications of the magnitude of likely debts in landscapes where few empirical data are available. PMID:26405738

  9. Extinction Training During the Reconsolidation Window Prevents Recovery of Fear

    PubMed Central

    Schiller, Daniela; Raio, Candace M.; Phelps, Elizabeth A.

    2012-01-01

    Fear is maladaptive when it persists long after circumstances have become safe. It is therefore crucial to develop an approach that persistently prevents the return of fear. Pavlovian fear-conditioning paradigms are commonly employed to create a controlled, novel fear association in the laboratory. After pairing an innocuous stimulus (conditioned stimulus, CS) with an aversive outcome (unconditioned stimulus, US) we can elicit a fear response (conditioned response, or CR) by presenting just the stimulus alone1,2 . Once fear is acquired, it can be diminished using extinction training, whereby the conditioned stimulus is repeatedly presented without the aversive outcome until fear is no longer expressed3. This inhibitory learning creates a new, safe representation for the CS, which competes for expression with the original fear memory4. Although extinction is effective at inhibiting fear, it is not permanent. Fear can spontaneously recover with the passage of time. Exposure to stress or returning to the context of initial learning can also cause fear to resurface3,4. Our protocol addresses the transient nature of extinction by targeting the reconsolidation window to modify emotional memory in a more permanent manner. Ample evidence suggests that reactivating a consolidated memory returns it to a labile state, during which the memory is again susceptible to interference5-9. This window of opportunity appears to open shortly after reactivation and close approximately 6hrs later5,11,16, although this may vary depending on the strength and age of the memory15. By allowing new information to incorporate into the original memory trace, this memory may be updated as it reconsolidates10,11. Studies involving non-human animals have successfully blocked the expression of fear memory by introducing pharmacological manipulations within the reconsolidation window, however, most agents used are either toxic to humans or show equivocal effects when used in human studies12-14. Our

  10. Antidepressants reduce extinction-induced withdrawal and biting behaviors: a model for depressive-like behavior.

    PubMed

    Huston, J P; van den Brink, J; Komorowski, M; Huq, Y; Topic, B

    2012-05-17

    The withholding of expected rewards results in extinction of behavior and, hypothetically, to depression-like symptoms. In a test of this hypothesis, we examined the effects of extinction of food-reinforced lever-pressing on collateral behaviors that might be indices of depression. Operant extinction is known to be aversive to the organism and results in avoidance behavior. We hypothesized that avoidance of, or withdrawal from, the former source of reward may serve as a marker for "despair." Adult male Wistar rats (n=6-7 animals per group) were exposed to a Skinner box attached to a second compartment of the same size, providing opportunity for the animals to leave the operant chamber and to enter the "withdrawal" compartment. The animals spent a portion of the time during the extinction trials in this second chamber. To assess the predictive validity of this behavior as a potential marker of "despair," we tested the effects of chronic administration of two common antidepressant drugs on this measure. The tricyclic antidepressant imipramine (20 mg/kg) as well as the selective serotonin reuptake inhibitor citalopram (20 mg/kg) reduced the number of entries and time spent in the withdrawal compartment. We propose that entries into and time spent in the withdrawal compartment may operationalize "avoidance," a core symptom of major depression. Rearing as well as biting behaviors during the extinction trials were also attenuated by the antidepressant treatment. These results lend support to the hypothesis that extinction of positively reinforced operants evokes behaviors that reflect elements of "despair/depression" because these behaviors are modulated by antidepressant treatment. The avoidance of the operant chamber as a consequence of extinction, together with rearing and biting behaviors, may serve as useful measures for the testing of antidepressant treatments. PMID:22410342

  11. Variant BDNF Val66Met polymorphism affects extinction of conditioned aversive memory.

    PubMed

    Yu, Hui; Wang, Yue; Pattwell, Siobhan; Jing, Deqiang; Liu, Ting; Zhang, Yun; Bath, Kevin G; Lee, Francis S; Chen, Zhe-Yu

    2009-04-01

    Brain-derived neurotrophic factor (BDNF) plays important roles in activity-dependent plasticity processes, such as long-term potentiation, learning, and memory. The recently reported human BDNF Val66Met (BDNF(Met)) polymorphism has been shown to lead to altered hippocampal volume and impaired hippocampal-dependent memory and is associated with a variety of neuropsychiatric disorders. There are few studies, however, that investigate the effect of the BDNF(Met) polymorphism on hippocampal-independent memory processes. A conditioned taste aversion (CTA) task was used for studying the mechanisms of long-term, hippocampal-independent, nondeclarative memory in the mammalian brain. Using the CTA paradigm, we found a novel impairment in extinction learning, but not acquisition or retention, of aversive memories resulting from the variant BDNF(Met). BDNF(Met) mice were slower to extinguish an aversive CTA memory compared with wild-type counterparts. Moreover, the BDNF(Met) was associated with smaller volume and decreased neuronal dendritic complexity in the ventromedial prefrontal cortex (vmPFC), which plays a significant role in extinction of CTA. Finally, this delay in extinction learning could be rescued pharmacologically with a cognitive enhancer, d-cycloserine (DCS). To our knowledge, this is the first evidence that the BDNF(Met) polymorphism contributes to abnormalities in memory extinction. This abnormality in extinction learning may be explained by alterations in neuronal morphology, as well as decreased neural activity in the vmPFC. Importantly, DCS was effective in rescuing this delay in extinction, suggesting that when coupled with behavior therapy, DCS may be an effective treatment option for anxiety disorders in humans with this genetic variant BDNF. PMID:19339601

  12. Drivers and hotspots of extinction risk in marine mammals

    PubMed Central

    Davidson, Ana D.; Boyer, Alison G.; Kim, Hwahwan; Pompa-Mansilla, Sandra; Hamilton, Marcus J.; Costa, Daniel P.; Ceballos, Gerardo; Brown, James H.

    2012-01-01

    The world's oceans are undergoing profound changes as a result of human activities. However, the consequences of escalating human impacts on marine mammal biodiversity remain poorly understood. The International Union for the Conservation of Nature (IUCN) identifies 25% of marine mammals as at risk of extinction, but the conservation status of nearly 40% of marine mammals remains unknown due to insufficient data. Predictive models of extinction risk are crucial to informing present and future conservation needs, yet such models have not been developed for marine mammals. In this paper, we: (i) used powerful machine-learning and spatial-modeling approaches to understand the intrinsic and extrinsic drivers of marine mammal extinction risk; (ii) used this information to predict risk across all marine mammals, including IUCN “Data Deficient” species; and (iii) conducted a spatially explicit assessment of these results to understand how risk is distributed across the world's oceans. Rate of offspring production was the most important predictor of risk. Additional predictors included taxonomic group, small geographic range area, and small social group size. Although the interaction of both intrinsic and extrinsic variables was important in predicting risk, overall, intrinsic traits were more important than extrinsic variables. In addition to the 32 species already on the IUCN Red List, our model identified 15 more species, suggesting that 37% of all marine mammals are at risk of extinction. Most at-risk species occur in coastal areas and in productive regions of the high seas. We identify 13 global hotspots of risk and show how they overlap with human impacts and Marine Protected Areas. PMID:22308490

  13. Drivers and hotspots of extinction risk in marine mammals.

    PubMed

    Davidson, Ana D; Boyer, Alison G; Kim, Hwahwan; Pompa-Mansilla, Sandra; Hamilton, Marcus J; Costa, Daniel P; Ceballos, Gerardo; Brown, James H

    2012-02-28

    The world's oceans are undergoing profound changes as a result of human activities. However, the consequences of escalating human impacts on marine mammal biodiversity remain poorly understood. The International Union for the Conservation of Nature (IUCN) identifies 25% of marine mammals as at risk of extinction, but the conservation status of nearly 40% of marine mammals remains unknown due to insufficient data. Predictive models of extinction risk are crucial to informing present and future conservation needs, yet such models have not been developed for marine mammals. In this paper, we: (i) used powerful machine-learning and spatial-modeling approaches to understand the intrinsic and extrinsic drivers of marine mammal extinction risk; (ii) used this information to predict risk across all marine mammals, including IUCN "Data Deficient" species; and (iii) conducted a spatially explicit assessment of these results to understand how risk is distributed across the world's oceans. Rate of offspring production was the most important predictor of risk. Additional predictors included taxonomic group, small geographic range area, and small social group size. Although the interaction of both intrinsic and extrinsic variables was important in predicting risk, overall, intrinsic traits were more important than extrinsic variables. In addition to the 32 species already on the IUCN Red List, our model identified 15 more species, suggesting that 37% of all marine mammals are at risk of extinction. Most at-risk species occur in coastal areas and in productive regions of the high seas. We identify 13 global hotspots of risk and show how they overlap with human impacts and Marine Protected Areas. PMID:22308490

  14. D-cycloserine administered directly to infralimbic medial prefrontal cortex enhances extinction memory in sucrose-seeking animals.

    PubMed

    Peters, J; De Vries, T J

    2013-01-29

    d-Cycloserine (DCS), a co-agonist at the N-methyl-D-aspartate (NMDA) receptor, has proven to be an effective adjunct to cognitive behavioral therapies that utilize extinction. This pharmacological-based enhancement of extinction memory has been primarily demonstrated in neuropsychiatric disorders characterized by pathological fear (e.g. posttraumatic stress disorder and various phobias). More recently, there has been an interest in applying such a strategy in the disorders of appetitive learning (e.g. substance abuse and other addictions), but these studies have generated mixed results. Here we first examined whether extinction memory encoding in a sucrose self-administration model is dependent on NMDA receptors. The NMDA antagonist (±)-3-(2-carboxypiperazin-4-yl)propyl-1-phosphonic acid (5mg/kg, i.p.) administered 2h prior to the first extinction training session effectively inhibited extinction memory recall 24h later, without affecting the expression of the conditioned sucrose-seeking response while the drug was on board. This profile of effects suggests a specific effect on extinction memory consolidation. Next, we sought to enhance extinction memory using the co-agonist DCS (10 μg/side) by infusion directly into infralimbic medial prefrontal cortex, a brain site implicated in extinction memory recall in conditioned fear models. Indeed, infusion of DCS immediately after the first extinction training session effectively enhanced extinction memory recall 24h later. Collectively, these data suggest that the neurobiological mechanisms and the neurocircuitry mediating extinction memory are similar regardless of the valence (aversive or appetitive) of the conditioned behavior, and that similar pharmacological strategies for treatment may be applied to neuropsychiatric disorders characterized by a failure to inhibit pathological emotional memories. PMID:23159319

  15. Mismatch between What Is Expected and What Actually Occurs Triggers Memory Reconsolidation or Extinction

    ERIC Educational Resources Information Center

    Pedreira, Maria Eugenia; Perez-Cuesta, Luis Maria; Maldonado, Hector

    2004-01-01

    In previous experiments on contextual memory, we proposed that the unreinforced re-exposure to the learning context (conditioned stimulus, CS) acts as a switch guiding the memory course toward reconsolidation or extinction, depending on reminder duration. This proposal implies that the system computes the total exposure time to the context, from…

  16. A Unifying Model of the Role of the Infralimbic Cortex in Extinction and Habits

    ERIC Educational Resources Information Center

    Barker, Jacqueline M.; Taylor, Jane R.; Chandler, L. Judson

    2014-01-01

    The infralimbic prefrontal cortex (IL) has been shown to be critical for the regulation of flexible behavior, but its precise function remains unclear. This region has been shown to be critical for the acquisition, consolidation, and expression of extinction learning, leading many to hypothesize that IL suppresses behavior as part of a…

  17. The Histone Deacetylase Inhibitor Valproic Acid Enhances Acquisition, Extinction, and Reconsolidation of Conditioned Fear

    ERIC Educational Resources Information Center

    Bredy, Timothy W.; Barad, Mark

    2008-01-01

    Histone modifications contribute to the epigenetic regulation of gene expression, a process now recognized to be important for the consolidation of long-term memory. Valproic acid (VPA), used for many years as an anticonvulsant and a mood stabilizer, has effects on learning and memory and enhances the extinction of conditioned fear through its…

  18. Effects of unconditioned stimulus intensity and fear extinction on subsequent sleep architecture in an afternoon nap.

    PubMed

    Sturm, Anna; Czisch, Michael; Spoormaker, Victor I

    2013-12-01

    Impaired fear extinction and disturbed sleep coincide in post-traumatic stress disorder (PTSD), but the nature of this relationship is unclear. Rapid eye movement (REM) sleep deprivation impairs fear extinction recall in rodents and young healthy subjects, and animal models have demonstrated both disrupted sleep after fear conditioning and normalized sleep after extinction learning. As a correlation between unconditioned stimulus (US) responding and subsequent sleep architecture has been observed in healthy subjects, the goal of this study was to test whether US intensity would causally affect subsequent sleep. Twenty-four young healthy subjects underwent a fear conditioning session with skin conductance response measurements before an afternoon session of polysomnographically recorded sleep (up to 120 min) in the sleep laboratory. Two factors were manipulated experimentally in a 2 × 2 design: US (electrical shock) was set at high or low intensity, and subjects did or did not receive an extinction session after fear conditioning. We observed that neither factor affected REM sleep amount, that high US intensity nominally increased sleep fragmentation (more Stage 1 sleep, stage shifts and wake after sleep onset), and that extinction increased Stage 4 amount. Moreover, reduced Stage 1 and increased Stage 4 and REM sleep were associated with subjective sleep quality of the afternoon nap. These results provide evidence for the notion that US intensity and extinction affect subsequent sleep architecture in young healthy subjects, which may provide a translational bridge from findings in animal studies to correlations observed in PTSD patients. PMID:23919462

  19. Age effects in storage and extinction of a naturally acquired conditioned eyeblink response.

    PubMed

    Thürling, M; Galuba, J; Thieme, A; Burciu, R G; Göricke, S; Beck, A; Wondzinski, E; Siebler, M; Gerwig, M; Bracha, V; Timmann, D

    2014-03-01

    Acquisition of conditioned eyeblink responses is known to decline with age, and age-related decline has been related to a reduction of cerebellar size and function. The aim of the present study was to investigate age-related effects on storage-related processes and extinction of visual threat eyeblink responses (VTERs), conditioned responses which are naturally acquired in early childhood. Storage and extinction of VTERs were tested in 34 healthy participants with an age range from 21 to 74 years (mean age 41.6±16.3 years). High-resolution structural magnetic resonance images (MRI) were acquired in all subjects. Conventional volumetric measures and voxel-based morphometry (VBM) were performed at the level of the cerebellum. Storage and extinction of VTERs showed a significant age-dependent decline. Likewise, cerebellar volume decreased with age. Storage, but not extinction showed a significant positive correlation with age-dependent reduction of total cerebellar volume. VBM analysis showed that gray matter volume in circumscribed areas of intermediate lobules VI, and Crus I and II bilaterally were positively correlated with VTER storage (p<0.05, FWE corrected). Considering extinction, no significant correlations with gray matter cerebellar volume were observed. The present findings show that reduction of storage of learned eyeblink responses with age is explained at least in part by age-dependent decline of cerebellar function. Future studies need to be performed to better understand which brain areas contribute to age-dependent reduction of extinction. PMID:24365777

  20. Retention of perceptual generalization of fear extinction.

    PubMed

    Pappens, Meike; Schroijen, Mathias; Van den Bergh, Omer; Van Diest, Ilse

    2015-12-01

    Fear reduction obtained during a fear extinction procedure can generalize from the extinction stimulus to other perceptually similar stimuli. Perceptual generalization of fear extinction typically follows a perceptual gradient, with increasing levels of fear reduction the more a stimulus resembles the extinction stimulus. The current study aimed to investigate whether perceptual generalization of fear extinction can be observed also after a retention interval of 24h. Fear was acquired to three geometrical figures of different sizes (CS(+), CS1(+) and CS2(+)) by consistently pairing them with a short-lasting suffocation experience (US). Three other geometrical figures that were never followed by the US served as control stimuli (CS(-), CS1(-), CS2(-)). Next, only the CS(+) was extinguished by presenting it in the absence of the US. One day later, fear responses to all stimuli were assessed without any US-presentation. Outcome measures included startle blink EMG, skin conductance, US expectancy, respiratory rate and tidal volume. On day 2 spontaneous recovery of fear was observed in US expectancy and tidal volume, but not in the other outcomes. Evidence for the retention of fear extinction generalization was present in US expectancy and skin conductance, but a perceptual gradient in the retention of generalized fear extinction could not be observed. PMID:25623628

  1. Acute tianeptine treatment selectively modulates neuronal activation in the central nucleus of the amygdala and attenuates fear extinction.

    PubMed

    Godsil, B P; Bontempi, B; Mailliet, F; Delagrange, P; Spedding, M; Jay, T M

    2015-11-01

    Antidepressant drugs are commonly prescribed treatments for anxiety disorders, and there is growing interest in understanding how these drugs impact fear extinction because extinction learning is pivotal to successful exposure-based therapy (EBT). A key objective within this domain is understanding how antidepressants alter the activation of specific elements of the limbic-based network that governs such fear processing. Chronic treatment with the antidepressant tianeptine has been shown to reduce the acquisition of extinction learning in rats, yet the drug's acute influence on activation in prefrontal and amygdalar regions, and on extinction learning are not well understood. To assess its influence on cellular activation, rats were injected with tianeptine and Fos immunoreactivity was measured in these regions. Acute tianeptine treatment selectively altered Fos expression within subdivisions of the central nucleus of the amygdala (CEA) in a bidirectional manner that varied in relation to ongoing activation within the capsular subdivision and its prefrontal and intra-amygdalar inputs. This pattern of results suggests that the drug can conditionally modulate the activation of CEA subdivisions, which contain microcircuits strongly implicated in fear processing. The effect of acute tianeptine was also examined with respect to the acquisition, consolidation and expression of fear extinction in rats. Acute tianeptine attenuated extinction learning as well as the recall of extinction memory, which underscores that acute dosing with the drug could alter learning during EBT. Together these findings provide a new perspective for understanding the mechanism supporting tianeptine's clinical efficacy, as well as its potential influence on CEA-based learning mechanisms. PMID:25560759

  2. The effect of geographic range on extinction risk during background and mass extinction

    PubMed Central

    Payne, Jonathan L.; Finnegan, Seth

    2007-01-01

    Wide geographic range is generally thought to buffer taxa against extinction, but the strength of this effect has not been investigated for the great majority of the fossil record. Although the majority of genus extinctions have occurred between major mass extinctions, little is known about extinction selectivity regimes during these “background” intervals. Consequently, the question of whether selectivity regimes differ between background and mass extinctions is largely unresolved. Using logistic regression, we evaluated the selectivity of genus survivorship with respect to geographic range by using a global database of fossil benthic marine invertebrates spanning the Cambrian through the Neogene periods, an interval of ≈500 My. Our results show that wide geographic range has been significantly and positively associated with survivorship for the great majority of Phanerozoic time. Moreover, the significant association between geographic range and survivorship remains after controlling for differences in species richness and abundance among genera. However, mass extinctions and several second-order extinction events exhibit less geographic range selectivity than predicted by range alone. Widespread environmental disturbance can explain the reduced association between geographic range and extinction risk by simultaneously affecting genera with similar ecological and physiological characteristics on global scales. Although factors other than geographic range have certainly affected extinction risk during many intervals, geographic range is likely the most consistently significant predictor of extinction risk in the marine fossil record. PMID:17563357

  3. Unconscious Familiarity-based Color-Form Binding: Evidence from Visual Extinction.

    PubMed

    Rappaport, Sarah J; Riddoch, M Jane; Chechlacz, Magda; Humphreys, Glyn W

    2016-03-01

    There is good evidence that early visual processing involves the coding of different features in independent brain regions. A major question, then, is how we see the world in an integrated manner, in which the different features are "bound" together. A standard account of this has been that feature binding depends on attention to the stimulus, which enables only the relevant features to be linked together [Treisman, A., & Gelade, G. A feature-integration theory of attention. Cognitive Psychology, 12, 97-136, 1980]. Here we test this influential idea by examining whether, in patients showing visual extinction, the processing of otherwise unconscious (extinguished) stimuli is modulated by presenting objects in their correct (familiar) color. Correctly colored objects showed reduced extinction when they had a learned color, and this color matched across the ipsi- and contralesional items (red strawberry + red tomato). In contrast, there was no reduction in extinction under the same conditions when the stimuli were colored incorrectly (blue strawberry + blue tomato; Experiment 1). The result was not due to the speeded identification of a correctly colored ipsilesional item, as there was no benefit from having correctly colored objects in different colors (red strawberry + yellow lemon; Experiment 2). There was also no benefit to extinction from presenting the correct colors in the background of each item (Experiment 3). The data suggest that learned color-form binding can reduce extinction even when color is irrelevant for the task. The result is consistent with preattentive binding of color and shape for familiar stimuli. PMID:26679213

  4. Sex differences in extinction recall in posttraumatic stress disorder: a pilot fMRI study.

    PubMed

    Shvil, Erel; Sullivan, Gregory M; Schafer, Scott; Markowitz, John C; Campeas, Miriam; Wager, Tor D; Milad, Mohammed R; Neria, Yuval

    2014-09-01

    Recent research has found that individuals with posttraumatic stress disorder (PTSD) exhibit an impaired memory of fear extinction compounded by deficient functional activation of key nodes of the fear network including the amygdala, hippocampus, ventromedial prefrontal cortex (vmPFC) and dorsal anterior cingulate cortex (dACC). Research has shown these regions are sexually dimorphic and activate differentially in healthy men and women during fear learning tasks. To explore biological markers of sex differences following exposure to psychological trauma, we used a fear learning and extinction paradigm together with functional magnetic resonance imaging (fMRI) and skin conductance response (SCR) to assess 31 individuals with PTSD (18 women; 13 men) and 25 matched trauma-exposed healthy control subjects (13 women; 12 men). Whereas no sex differences appeared within the trauma-exposed healthy control group, both psychophysiological and neural activation patterns within the PTSD group indicated deficient recall of extinction memory among men and not among women. Men with PTSD exhibited increased activation in the left rostral dACC during extinction recall compared with women with PTSD. These findings highlight the importance of tracking sex differences in fear extinction when characterizing the underlying neurobiological mechanisms of PTSD psychopathology. PMID:24560771

  5. Avoidant symptoms in PTSD predict fear circuit activation during multimodal fear extinction

    PubMed Central

    Sripada, Rebecca K.; Garfinkel, Sarah N.; Liberzon, Israel

    2013-01-01

    Convergent evidence suggests that individuals with posttraumatic stress disorder (PTSD) exhibit exaggerated avoidance behaviors as well as abnormalities in Pavlonian fear conditioning. However, the link between the two features of this disorder is not well understood. In order to probe the brain basis of aberrant extinction learning in PTSD, we administered a multimodal classical fear conditioning/extinction paradigm that incorporated affectively relevant information from two sensory channels (visual and tactile) while participants underwent fMRI scanning. The sample consisted of fifteen OEF/OIF veterans with PTSD. In response to conditioned cues and contextual information, greater avoidance symptomatology was associated with greater activation in amygdala, hippocampus, vmPFC, dmPFC, and insula, during both fear acquisition and fear extinction. Heightened responses to previously conditioned stimuli in individuals with more severe PTSD could indicate a deficiency in safety learning, consistent with PTSD symptomatology. The close link between avoidance symptoms and fear circuit activation suggests that this symptom cluster may be a key component of fear extinction deficits in PTSD and/or may be particularly amenable to change through extinction-based therapies. PMID:24146643

  6. Sex differences in extinction recall in posttraumatic stress disorder: A pilot fMRI study

    PubMed Central

    Shvil, Erel; Sullivan, Gregory M.; Schafer, Scott; Markowitz, John C.; Campeas, Miriam; Wager, Tor D.; Milad, Mohammed R.; Neria, Yuval

    2014-01-01

    Recent research has found that individuals with posttraumatic stress disorder (PTSD) exhibit an impaired memory of fear extinction compounded by deficient functional activation of key nodes of the fear network including the amygdala, hippocampus, ventromedial prefrontal cortex (vmPFC) and dorsal anterior cingulate cortex (dACC). Research has shown these regions are sexually dimorphic and activate differentially in healthy men and women during fear learning tasks. To explore biological markers of sex differences following exposure to psychological trauma, we used a fear learning and extinction paradigm together with functional magnetic resonance imaging (fMRI) and skin conductance response (SCR) to assess 31 individuals with PTSD (18 women; 13 men) and 25 matched trauma-exposed healthy control subjects (13 women; 12 men). Whereas no sex differences appeared within the trauma-exposed healthy control group, both psychophysiological and neural activation patterns within the PTSD group indicated deficient recall of extinction memory among men and not among women. Men with PTSD exhibited increased activation in the left rostral dACC during extinction recall compared with women with PTSD. These findings highlight the importance of tracking sex differences in fear extinction when characterizing the underlying neurobiological mechanisms of PTSD psychopathology. PMID:24560771

  7. Sleep and REM sleep disturbance in the pathophysiology of PTSD: the role of extinction memory.

    PubMed

    Pace-Schott, Edward F; Germain, Anne; Milad, Mohammed R

    2015-01-01

    Post-traumatic stress disorder (PTSD) is accompanied by disturbed sleep and an impaired ability to learn and remember extinction of conditioned fear. Following a traumatic event, the full spectrum of PTSD symptoms typically requires several months to develop. During this time, sleep disturbances such as insomnia, nightmares, and fragmented rapid eye movement sleep predict later development of PTSD symptoms. Only a minority of individuals exposed to trauma go on to develop PTSD. We hypothesize that sleep disturbance resulting from an acute trauma, or predating the traumatic experience, may contribute to the etiology of PTSD. Because symptoms can worsen over time, we suggest that continued sleep disturbances can also maintain and exacerbate PTSD. Sleep disturbance may result in failure of extinction memory to persist and generalize, and we suggest that this constitutes one, non-exclusive mechanism by which poor sleep contributes to the development and perpetuation of PTSD. Also reviewed are neuroendocrine systems that show abnormalities in PTSD, and in which stress responses and sleep disturbance potentially produce synergistic effects that interfere with extinction learning and memory. Preliminary evidence that insomnia alone can disrupt sleep-dependent emotional processes including consolidation of extinction memory is also discussed. We suggest that optimizing sleep quality following trauma, and even strategically timing sleep to strengthen extinction memories therapeutically instantiated during exposure therapy, may allow sleep itself to be recruited in the treatment of PTSD and other trauma and stress-related disorders. PMID:26034578

  8. The circumstellar extinction of RY Sagittarii

    NASA Technical Reports Server (NTRS)

    Holm, A. V.; Wu, C.-C.; Doherty, L. R.

    1982-01-01

    In 1979-80, ultraviolet spectrophotometry of RY Sgr was obtained by the International Ultraviolet Explorer (IUE) during the star's recovery from its 1977-78 minimum. The wavelength dependence of the extinction of this R Coronae Borealis-type variable was determined by comparison of spectra obtained at different times but with nearly the same pulsational phase. The measured wavelength dependence is compatible with theoretical predictions of extinction by spherical graphite particles having a radius of 0.043 micron and with the extinction observed for amorphorus carbon smoke.

  9. Large igneous provinces and mass extinctions

    NASA Astrophysics Data System (ADS)

    Wignall, P. B.

    2001-03-01

    Comparing the timing of mass extinctions with the formation age of large igneous provinces reveals a close correspondence in five cases, but previous claims that all such provinces coincide with extinction events are unduly optimistic. The best correlation occurs for four consecutive mid-Phanerozoic examples, namely the end-Guadalupian extinction/Emeishan flood basalts, the end-Permian extinction/Siberian Traps, the end-Triassic extinction/central Atlantic volcanism and the early Toarcian extinction/Karoo Traps. Curiously, the onset of eruptions slightly post-dates the main phase of extinctions in these examples. Of the seven post-Karoo provinces, only the Deccan Traps coincide with a mass extinction, but in this case, the nature of the biotic crisis is best reconciled with the effects of a major bolide impact. Intraoceanic volcanism may also be implicated in a relatively minor end-Cenomanian extinction crisis, although once again the main phase of volcanism occurs after the crisis. The link between large igneous province formation and extinctions remains enigmatic; volume of extrusives and extinction intensity are unrelated and neither is there any apparent relationship with the rapidity of province formation. Violence of eruptions (proportions of pyroclastics) also appears unimportant. Six out of 11 provinces coincide with episodes of global warming and marine anoxia/dysoxia, a relationship that suggests that volcanic CO 2 emissions may have an important effect on global climate. Conversely, there is little, if any, geological evidence for cooling associated with continental flood basalt eruptions suggesting little long-term impact of SO 2 emissions. Large carbon isotope excursions are associated with some extinction events and intervals of flood basalt eruption but these are too great to be accounted for by the release of volcanic CO 2 alone. Thus, voluminous volcanism may in some circumstances trigger calamitous global environmental changes (runaway greenhouses

  10. Histone modifications around individual BDNF gene promoters in prefrontal cortex are associated with extinction of conditioned fear.

    PubMed

    Bredy, Timothy W; Wu, Hao; Crego, Cortney; Zellhoefer, Jessica; Sun, Yi E; Barad, Mark

    2007-04-01

    Extinction of conditioned fear is an important model both of inhibitory learning and of behavior therapy for human anxiety disorders. Like other forms of learning, extinction learning is long-lasting and depends on regulated gene expression. Epigenetic mechanisms make an important contribution to persistent changes in gene expression; therefore, in these studies, we have investigated whether epigenetic regulation of gene expression contributes to fear extinction. Since brain-derived neurotrophic factor (BDNF) is crucial for synaptic plasticity and for the maintenance of long-term memory, we examined histone modifications around two BDNF gene promoters after extinction of cued fear, as potential targets of learning-induced epigenetic regulation of gene expression. Valproic acid (VPA), used for some time as an anticonvulsant and a mood stabilizer, modulates the expression of BDNF, and is a histone deacetylase (HDAC) inhibitor. Here, we report that extinction of conditioned fear is accompanied by a significant increase in histone H4 acetylation around the BDNF P4 gene promoter and increases in BDNF exon I and IV mRNA expression in prefrontal cortex, that VPA enhances long-term memory for extinction because of its HDAC inhibitor effects, and that VPA potentiates the effect of weak extinction training on histone H4 acetylation around both the BDNF P1 and P4 gene promoters and on BDNF exon IV mRNA expression. These results suggest a relationship between histone H4 modification, epigenetic regulation of BDNF gene expression, and long-term memory for extinction of conditioned fear. In addition, they suggest that HDAC inhibitors may become a useful pharmacological adjunct to psychotherapy for human anxiety disorders. PMID:17522015

  11. Inhibition of spontaneous recovery of fear by mGluR5 after prolonged extinction training.

    PubMed

    Mao, Sheng-Chun; Chang, Chih-Hua; Wu, Chia-Chen; Orejarena, M Juliana; Orejanera, Maria Juliana; Manzoni, Olivier J; Gean, Po-Wu

    2013-01-01

    Fear behavior is vital for survival and involves learning contingent associations of non-threatening cues with aversive stimuli. In contrast, excessive levels of fear can be maladaptive and lead to anxiety disorders. Generally, extensive sessions of extinction training correlates with reduced spontaneous recovery. The molecular mechanisms underlying the long-term inhibition of fear recovery following repeated extinction training are not fully understood. Here we show that in rats, prolonged extinction training causes greater reduction in both fear-potentiated startle and spontaneous recovery. This effect was specifically blocked by metabotropic glutamate receptor 5 (mGluR5), but not by mGluR1 antagonists and by a protein synthesis inhibitor. Similar inhibition of memory recovery following prolonged extinction training was also observed in mice. In agreement with the instrumental role of mGluR5 in the prolonged inhibition of fear recovery, we found that FMR1-/- mice which exhibit enhanced mGluR5-mediated signaling exhibit lower spontaneous recovery of fear after extinction training than wild-type littermates. At the molecular level, we discovered that prolonged extinction training reversed the fear conditioning-induced increase in surface expression of GluR1, AMPA/NMDA ratio, postsynaptic density-95 (PSD-95) and synapse-associated protein-97 (SAP97). Accordingly, delivery of Tat-GluR2(3Y), a synthetic peptide that blocks AMPA receptor endocytosis, inhibited prolonged extinction training-induced inhibition of fear recovery. Together, our results demonstrate that prolonged extinction training results in the mGluR5-dependent long-term inhibition of fear recovery. This effect may involve the degradation of original memory and may explain the beneficial effects of prolonged exposure therapy for the treatment of phobias. PMID:23555716

  12. Hospital autopsy: Endangered or extinct?

    PubMed Central

    Turnbull, Angus; Osborn, Michael; Nicholas, Nick

    2015-01-01

    Aim To determine the hospital autopsy rate for the UK in 2013. Methods A study of data from a ‘Freedom of Information’ request to all (n=186) acute NHS Trusts within England (n=160), NHS Boards in Scotland (n=14) and Wales (n=7) and Social Care Trusts in Northern Ireland (n=5). Hospital autopsy rates were calculated from the number of hospital autopsies performed in 2013 as a percentage of total inpatient deaths in the Trust that year. Results The UK response rate was 99% (n=184), yielding a mean autopsy rate of 0.69%. The mean rates were 0.51% (England), 2.13% (Scotland), 0.65% (Wales) and 0.46% (Northern Ireland). 23% (n=38) of all included respondents had a rate of 0% and 86% (n=143) a rate less than 1%. Conclusions The decline in hospital autopsy has continued relentlessly and, for better or for worse, the practice is on the verge of extinction in the UK. The study highlights to health professionals and policy makers the magnitude of this decline. Further research should investigate the impact of this on patient safety, clinical audit, public health and medical education. PMID:26076965

  13. Deficiency of the 65 kDa isoform of glutamic acid decarboxylase impairs extinction of cued but not contextual fear memory.

    PubMed

    Sangha, Susan; Narayanan, Rajeevan T; Bergado-Acosta, Jorge R; Stork, Oliver; Seidenbecher, Thomas; Pape, Hans-Christian

    2009-12-16

    Extinction procedures are clinically relevant for reducing pathological fear, and the mechanisms of fear regulation are a subject of intense research. The amygdala, hippocampus, and prefrontal cortex (PFC) have all been suggested to be key brain areas in extinction of conditioned fear. GABA has particularly been implicated in extinction learning, and the 65 kDa isoform of glutamic acid decarboxylase (GAD65) may be important in elevating GABA levels in response to environmental signals. Extinction of conditioned fear was examined in Gad65(-/-) mice while recording local field potentials from the amygdala, hippocampus, and PFC simultaneously while monitoring behavior. Gad65(-/-) mice showed generalization of cued fear, as reported previously, and impaired extinction of cued fear, such that fear remained high across extinction training. This endurance in cued fear was associated with theta frequency synchronization between the amygdala and hippocampus. Extinction of contextual fear, however, was unaltered in Gad65(-/-) mice when compared with wild-type littermates. The data imply that GAD65 plays a critical role in regulating cued fear responses during extinction learning and that, during this process, GABAergic signaling is involved in modulating synchronized activity between the amygdala and hippocampus. In view of the more pronounced effect on cued versus contextual fear extinction, these influences may rely more on GABAergic mechanisms in the amygdala. PMID:20016086

  14. Employer Provisions for Parental Leave.

    ERIC Educational Resources Information Center

    Meisenheimer, Joseph R., II

    1989-01-01

    Slightly more than one-third of full-time employees in medium and large firms in private industry were covered by maternity- or paternity-leave policies; days off were usually leave without pay. (Author)

  15. Association of extinction risk of saproxylic beetles with ecological degradation of forests in Europe.

    PubMed

    Seibold, Sebastian; Brandl, Roland; Buse, Jörn; Hothorn, Torsten; Schmidl, Jürgen; Thorn, Simon; Müller, Jörg

    2015-04-01

    To reduce future loss of biodiversity and to allocate conservation funds effectively, the major drivers behind large-scale extinction processes must be identified. A promising approach is to link the red-list status of species and specific traits that connect species of functionally important taxa or guilds to resources they rely on. Such traits can be used to detect the influence of anthropogenic ecosystem changes and conservation efforts on species, which allows for practical recommendations for conservation. We modeled the German Red List categories as an ordinal index of extinction risk of 1025 saproxylic beetles with a proportional-odds linear mixed-effects model for ordered categorical responses. In this model, we estimated fixed effects for intrinsic traits characterizing species biology, required resources, and distribution with phylogenetically correlated random intercepts. The model also allowed predictions of extinction risk for species with no red-list category. Our model revealed a higher extinction risk for lowland and large species as well as for species that rely on wood of large diameter, broad-leaved trees, or open canopy. These results mirror well the ecological degradation of European forests over the last centuries caused by modern forestry, that is the conversion of natural broad-leaved forests to dense conifer-dominated forests and the loss of old growth and dead wood. Therefore, conservation activities aimed at saproxylic beetles in all types of forests in Central and Western Europe should focus on lowlands, and habitat management of forest stands should aim at increasing the amount of dead wood of large diameter, dead wood of broad-leaved trees, and dead wood in sunny areas. PMID:25429849

  16. Activation of D1/5 Dopamine Receptors: A Common Mechanism for Enhancing Extinction of Fear and Reward-Seeking Behaviors.

    PubMed

    Abraham, Antony D; Neve, Kim A; Lattal, K Matthew

    2016-07-01

    Dopamine is critical for many processes that drive learning and memory, including motivation, prediction error, incentive salience, memory consolidation, and response output. Theories of dopamine's function in these processes have, for the most part, been developed from behavioral approaches that examine learning mechanisms in appetitive tasks. A parallel and growing literature indicates that dopamine signaling is involved in consolidation of memories into stable representations in aversive tasks such as fear conditioning. Relatively little is known about how dopamine may modulate memories that form during extinction, when organisms learn that the relation between previously associated events is severed. We investigated whether fear and reward extinction share common mechanisms that could be enhanced with dopamine D1/5 receptor activation. Pharmacological activation of dopamine D1/5 receptors (with SKF 81297) enhanced extinction of both cued and contextual fear. These effects also occurred in the extinction of cocaine-induced conditioned place preference, suggesting that the observed effects on extinction were not specific to a particular type of procedure (aversive or appetitive). A cAMP/PKA biased D1 agonist (SKF 83959) did not affect fear extinction, whereas a broadly efficacious D1 agonist (SKF 83822) promoted fear extinction. Together, these findings show that dopamine D1/5 receptor activation is a target for the enhancement of fear or reward extinction. PMID:26763483

  17. Are marine and nonmarine extinctions correlated?

    NASA Astrophysics Data System (ADS)

    Rampino, Michael R.

    Recent papers in Eos have debated the possible relationships between marine mass extinctions, comet showers, and volcanism [Alvarez, 1986; Officer and Grieve, 1986], and ail three might be linked [Rampino, 1987]. Moreover, as Officer and Grieve [ 1986] point out, various other causes have been suggested for given extinction events, including changes in climate, ocean circulation, and sea level fluctuations, possibly related to plate tectonics and continental positions. Also under debate is the issue of whether mass extinctions were gradual, stepped, or geologically sudden events (see, for example, Hut et al. [1987]). A missing ingredient thus far in these debates has been the record of faunal diversity of nonmarine animals. Does this show any agreement with the marine extinction record?

  18. Opportunistic exploitation: an overlooked pathway to extinction.

    PubMed

    Branch, Trevor A; Lobo, Aaron S; Purcell, Steven W

    2013-07-01

    How can species be exploited economically to extinction? Past single-species hypotheses examining the economic plausibility of exploiting rare species have argued that the escalating value of rarity allows extinction to be profitable. We describe an alternative pathway toward extinction in multispecies exploitation systems, termed 'opportunistic exploitation'. In this mode, highly valued species that are targeted first by fishing, hunting, and logging become rare, but their populations can decline further through opportunistic exploitation while more common but less desirable species are targeted. Effectively, expanding exploitation to more species subsidizes the eventual extinction of valuable species at low densities. Managers need to recognize conditions that permit opportunistic depletion and pass regulations to protect highly desirable species when exploitation can expand to other species. PMID:23562732

  19. Epidemic Extinction and Control in Heterogeneous Networks

    NASA Astrophysics Data System (ADS)

    Hindes, Jason; Schwartz, Ira B.

    2016-07-01

    We consider epidemic extinction in finite networks with a broad variation in local connectivity. Generalizing the theory of large fluctuations to random networks with a given degree distribution, we are able to predict the most probable, or optimal, paths to extinction in various configurations, including truncated power laws. We find that paths for heterogeneous networks follow a limiting form in which infection first decreases in low-degree nodes, which triggers a rapid extinction in high-degree nodes, and finishes with a residual low-degree extinction. The usefulness of our approach is further demonstrated through optimal control strategies that leverage the dependence of finite-size fluctuations on network topology. Interestingly, we find that the optimal control is a mix of treating both high- and low-degree nodes based on theoretical predictions, in contrast to methods that ignore dynamical fluctuations.

  20. Biomarker Records Associated with Mass Extinction Events

    NASA Astrophysics Data System (ADS)

    Whiteside, Jessica H.; Grice, Kliti

    2016-06-01

    The history of life on Earth is punctuated by a series of mass extinction episodes that vary widely in their magnitude, duration, and cause. Biomarkers are a powerful tool for the reconstruction of historical environmental conditions and can therefore provide insights into the cause and responses to ancient extinction events. In examining the five largest mass extinctions in the geological record, investigators have used biomarkers to elucidate key processes such as eutrophy, euxinia, ocean acidification, changes in hydrological balance, and changes in atmospheric CO2. By using these molecular fossils to understand how Earth and its ecosystems have responded to unusual environmental activity during these extinctions, models can be made to predict how Earth will respond to future changes in its climate.

  1. Limited diversity of the interstellar extinction law

    NASA Astrophysics Data System (ADS)

    Krełowski, J.; Strobel, A.

    2012-01-01

    We have applied the method of investigating extinction curves using statistically meaningful samples that was proposed by us 25 years ago. The extensive data sets of the ANS (Astronomical Netherlands Satellite) and 2MASS (Two Micron All Sky Survey) were used, together with U BV photometry to create average extinction curves for samples of OB stars. Our results demonstrate that in the vast majority of cases the extinction curves are very close to the mean galactic extinction curve. Only a few objects were found to be obviously discrepant from the average. The latter phenomenon may be related to nitrogen chemistry in translucent interstellar clouds. Data from ANS and 2MASS Tables A4-A6 are available at the CDS via http://cdsarc.u-strasbg.fr/cgi-bin/qcat?J/AN/333/60

  2. Life in the Aftermath of Mass Extinctions.

    PubMed

    Hull, Pincelli

    2015-10-01

    The vast majority of species that have ever lived went extinct sometime other than during one of the great mass extinction events. In spite of this, mass extinctions are thought to have outsized effects on the evolutionary history of life. While part of this effect is certainly due to the extinction itself, I here consider how the aftermaths of mass extinctions might contribute to the evolutionary importance of such events. Following the mass loss of taxa from the fossil record are prolonged intervals of ecological upheaval that create a selective regime unique to those times. The pacing and duration of ecosystem change during extinction aftermaths suggests strong ties between the biosphere and geosphere, and a previously undescribed macroevolutionary driver - earth system succession. Earth system succession occurs when global environmental or biotic change, as occurs across extinction boundaries, pushes the biosphere and geosphere out of equilibrium. As species and ecosystems re-evolve in the aftermath, they change global biogeochemical cycles - and in turn, species and ecosystems - over timescales typical of the geosphere, often many thousands to millions of years. Earth system succession provides a general explanation for the pattern and timing of ecological and evolutionary change in the fossil record. Importantly, it also suggests that a speed limit might exist for the pace of global biotic change after massive disturbance - a limit set by geosphere-biosphere interactions. For mass extinctions, earth system succession may drive the ever-changing ecological stage on which species evolve, restructuring ecosystems and setting long-term evolutionary trajectories as they do. PMID:26439357

  3. Extinction rates of established spatial populations

    NASA Astrophysics Data System (ADS)

    Meerson, Baruch; Sasorov, Pavel V.

    2011-01-01

    This paper deals with extinction of an isolated population caused by intrinsic noise. We model the population dynamics in a “refuge” as a Markov process which involves births and deaths on discrete lattice sites and random migrations between neighboring sites. In extinction scenario I, the zero population size is a repelling fixed point of the on-site deterministic dynamics. In extinction scenario II, the zero population size is an attracting fixed point, corresponding to what is known in ecology as the Allee effect. Assuming a large population size, we develop a WKB (Wentzel-Kramers-Brillouin) approximation to the master equation. The resulting Hamilton’s equations encode the most probable path of the population toward extinction and the mean time to extinction. In the fast-migration limit these equations coincide, up to a canonical transformation, with those obtained, in a different way, by Elgart and Kamenev [Phys. Rev. EPHYADX1539-375510.1103/PhysRevE.70.041106 70, 041106 (2004)]. We classify possible regimes of population extinction with and without an Allee effect and for different types of refuge, and solve several examples analytically and numerically. For a very strong Allee effect, the extinction problem can be mapped into the overdamped limit of the theory of homogeneous nucleation due to Langer [Ann. Phys. (NY)APNYA60003-491610.1016/0003-4916(69)90153-5 54, 258 (1969)]. In this regime, and for very long systems, we predict an optimal refuge size that maximizes the mean time to extinction.

  4. Mass extinctions in the deep sea

    NASA Technical Reports Server (NTRS)

    Thomas, E.

    1988-01-01

    The character of mass extinctions can be assessed by studying extinction patterns of organisms, the fabric of the extinction, and assessing the environmental niche and mode of life of survivors. Deep-sea benthic foraminifera have been listed as little affected by the Cretaceous-Tertiary (K-T) mass extinction, but very few quantitative data are available. New data on deep-sea Late Maestrichtian-Eocene benthic foraminifera from Maud Rise (Antractica) indicate that about 10 percent of the species living at depths of 2000 to 2500 m had last appearances within 1 my of the Cretaceous-Tertiary (K-T) boundary, versus about 25 percent of species at 1000 to 1500 m. Many survivors from the Cretaceous became extinct in a period of global deep-sea benthic foraminiferal extinction at the end of the Paleocene, a time otherwise marked by very few extinctions. Preliminary conclusions suggest that the deep oceanic environment is essentially decoupled from the shallow marine and terrestrial environment, and that even major disturbances of one of these will not greatly affect the other. This gives deep-sea benthic faunas a good opportunity to recolonize shallow environments from greater depths and vice versa after massive extinctions. The decoupling means that data on deep-sea benthic boundary was caused by the environmental effects of asteriod impact or excessive volcanism. The benthic foraminiferal data strongly suggest, however, that the environmental results were strongest at the Earth's surface, and that there was no major disturbance of the deep ocean; this pattern might result both from excessive volcanism and from an impact on land.

  5. Properties of Dust Extinction in Starburst Galaxies

    NASA Astrophysics Data System (ADS)

    Calzetti, D.; Kinney, A. L.; Storchi-Bergmann, T.; Panagia, N.

    1993-05-01

    We have studied the extinction properties of 38 starburst and Blue Compact galaxies covering the metallicity range 8.3<=log (O/H)<=9.2, by analyzing their UV+optical spectra. The UV spectra come from the compilation of IUE spectra by Kinney et al. (Kinney, Bohlin, Calzetti, Panagia, & Wyse, 1993, ApJS, to appear on the May issue). The optical spectra, spanning the wavelength range 3200-7500 Angstroms, have been observed in a IUE-matched aperture. Following standard techniques, we have derived the selective extinction E(B-V) from the Balmer decrement and the metallicity from the [OII] and [OIII] lines. In order to clarify the properties of dust extinction in the UV for starburst galaxies, we have fitted the observed UV fluxes of our galaxies in the wavelength range 1250-2600 Angstroms according to the power law F(lambda )~lambda (beta ) and studied the behaviour of beta as function of the selective extinction E(B-V). We find that these two quantities are correlated and that there is no difference between the loci occupied by the low and high metallicity galaxies in the plane beta -vs-E(B-V). The correlation indicates that a higher metallicity does not change the characteristics of individual grains, but merely increases their number. On this ground, our conclusion is that the shape of the extinction law in the UV does not depend on metallicity, for extinctions E(B-V)>0.2. Although the low metallicity galaxies in our sample follow neither the Large Magellanic Cloud nor the Small Magellanic Cloud extinction laws, the absence in our spectra of prominent 2200 Angstroms dust features illustrates that a simple application of a galactic extinction law may be inadequate to properly correct the UV spectra. Models of clumpy dust layers and of dust mixed with the ionized gas are currently under analysis.

  6. On the prior distribution of extinction time.

    PubMed

    Solow, Andrew R

    2016-06-01

    Bayesian inference about the extinction of a species based on a record of its sightings requires the specification of a prior distribution for extinction time. Here, I critically review some specifications in the context of a specific model of the sighting record. The practical implication of the choice of prior distribution is illustrated through an application to the sighting record of the Caribbean monk seal. PMID:27277952

  7. How does climate change cause extinction?

    PubMed Central

    Cahill, Abigail E.; Aiello-Lammens, Matthew E.; Fisher-Reid, M. Caitlin; Hua, Xia; Karanewsky, Caitlin J.; Yeong Ryu, Hae; Sbeglia, Gena C.; Spagnolo, Fabrizio; Waldron, John B.; Warsi, Omar; Wiens, John J.

    2013-01-01

    Anthropogenic climate change is predicted to be a major cause of species extinctions in the next 100 years. But what will actually cause these extinctions? For example, will it be limited physiological tolerance to high temperatures, changing biotic interactions or other factors? Here, we systematically review the proximate causes of climate-change related extinctions and their empirical support. We find 136 case studies of climatic impacts that are potentially relevant to this topic. However, only seven identified proximate causes of demonstrated local extinctions due to anthropogenic climate change. Among these seven studies, the proximate causes vary widely. Surprisingly, none show a straightforward relationship between local extinction and limited tolerances to high temperature. Instead, many studies implicate species interactions as an important proximate cause, especially decreases in food availability. We find very similar patterns in studies showing decreases in abundance associated with climate change, and in those studies showing impacts of climatic oscillations. Collectively, these results highlight our disturbingly limited knowledge of this crucial issue but also support the idea that changing species interactions are an important cause of documented population declines and extinctions related to climate change. Finally, we briefly outline general research strategies for identifying these proximate causes in future studies. PMID:23075836

  8. Compound Stimulus Extinction Reduces Spontaneous Recovery in Humans

    ERIC Educational Resources Information Center

    Coelho, Cesar A. O.; Dunsmoor, Joseph E.; Phelps, Elizabeth A.

    2015-01-01

    Fear-related behaviors are prone to relapse following extinction. We tested in humans a compound extinction design ("deepened extinction") shown in animal studies to reduce post-extinction fear recovery. Adult subjects underwent fear conditioning to a visual and an auditory conditioned stimulus (CSA and CSB, respectively) separately…

  9. Enhanced extinction of contextual fear conditioning in ClockΔ19 mutant mice.

    PubMed

    Bernardi, Rick E; Spanagel, Rainer

    2014-08-01

    Clock genes have been implicated in several disorders, such as schizophrenia, bipolar disorder, autism spectrum disorders, and drug dependence. However, few studies to date have examined the role of clock genes in fear-related behaviors. The authors used mice with the ClockΔ19 mutation to assess the involvement of this gene in contextual fear conditioning. Male wild-type (WT) and ClockΔ19 mutant mice underwent a single session of contextual fear conditioning (12 min, 4 unsignaled shocks), followed by daily 12-min retention trials. There were no differences between mutant and WT mice in the acquisition of contextual fear, and WT and mutant mice demonstrated similar freezing during the first retention session. However, extinction of contextual fear was accelerated in mutant mice across the remaining retention sessions, as compared to WT mice, suggesting a role for Clock in extinction following aversive learning. Because the ClockΔ19 mutation has previously been demonstrated to result in an increase in dopamine signaling, the authors confirmed the role of dopamine in extinction learning using preretention session administration of a low dose of the dopamine transport reuptake inhibitor modafinil (0.75 mg/kg), which resulted in decreased freezing across retention sessions. These findings are consistent with an emerging portrayal of the importance of Clock genes in noncircadian functions, as well as the important role of dopamine in extinction learning. PMID:24865659

  10. On the accuracy of stratospheric aerosol extinction derived from in situ size distribution measurements and surface area density derived from remote SAGE II and HALOE extinction measurements

    NASA Astrophysics Data System (ADS)

    Kovilakam, Mahesh; Deshler, Terry

    2015-08-01

    In situ stratospheric aerosol measurements, from University of Wyoming optical particle counters (OPCs), are compared with Stratospheric Aerosol Gas Experiment (SAGE) II (versions 6.2 and 7.0) and Halogen Occultation Experiment (HALOE) satellite measurements to investigate differences between SAGE II/HALOE-measured extinction and derived surface area and OPC-derived extinction and surface area. Coincident OPC and SAGE II measurements are compared for a volcanic (1991-1996) and nonvolcanic (1997-2005) period. OPC calculated extinctions agree with SAGE II measurements, within instrumental uncertainty, during the volcanic period, but have been a factor of 2 low during the nonvolcanic period. Three systematic errors associated with the OPC measurements, anisokineticity, inlet particle evaporation, and counting efficiency, were investigated. An overestimation of the OPC counting efficiency is found to be the major source of systematic error. With this correction OPC calculated extinction increases by 15-30% (30-50%) for the volcanic (nonvolcanic) measurements. These changes significantly improve the comparison with SAGE II and HALOE extinctions in the nonvolcanic cases but slightly degrade the agreement in the volcanic period. These corrections have impacts on OPC-derived surface area density, exacerbating the poor agreement between OPC and SAGE II (version 6.2) surface areas. This disparity is reconciled with SAGE II version 7.0 surface areas. For both the volcanic and nonvolcanic cases these changes in OPC counting efficiency and in the operational SAGE II surface area algorithm leave the derived surface areas from both platforms in significantly better agreement and within the ± 40% precision of the OPC moment calculations.

  11. On the accuracy of stratospheric aerosol extinction derived from in situ size distribution measurements and surface area density derived from remote SAGE II and HALOE extinction measurements

    DOE PAGESBeta

    Kovilakam, Mahesh; Deshler, Terry

    2015-08-26

    In situ stratospheric aerosol measurements, from University of Wyoming optical particle counters (OPCs), are compared with Stratospheric Aerosol Gas Experiment (SAGE) II (versions 6.2 and 7.0) and Halogen Occultation Experiment (HALOE) satellite measurements to investigate differences between SAGE II/HALOE-measured extinction and derived surface area and OPC-derived extinction and surface area. Coincident OPC and SAGE II measurements are compared for a volcanic (1991-1996) and nonvolcanic (1997 2005) period. OPC calculated extinctions agree with SAGE II measurements, within instrumental uncertainty, during the volcanic period, but have been a factor of 2 low during the nonvolcanic period. Three systematic errors associated with themore » OPC measurements, anisokineticity, inlet particle evaporation, and counting efficiency, were investigated. An overestimation of the OPC counting efficiency is found to be the major source of systematic error. With this correction OPC calculated extinction increases by 15 30% (30 50%) for the volcanic (nonvolcanic) measurements. These changes significantly improve the comparison with SAGE II and HALOE extinctions in the nonvolcanic cases but slightly degrade the agreement in the volcanic period. These corrections have impacts on OPC-derived surface area density, exacerbating the poor agreement between OPC and SAGE II (version 6.2) surface areas. This disparity is reconciled with SAGE II version 7.0 surface areas. For both the volcanic and nonvolcanic cases these changes in OPC counting efficiency and in the operational SAGE II surface area algorithm leave the derived surface areas from both platforms in significantly better agreement and within the 40% precision of the OPC moment calculations.« less

  12. On the accuracy of stratospheric aerosol extinction derived from in situ size distribution measurements and surface area density derived from remote SAGE II and HALOE extinction measurements

    SciTech Connect

    Kovilakam, Mahesh; Deshler, Terry

    2015-08-26

    In situ stratospheric aerosol measurements, from University of Wyoming optical particle counters (OPCs), are compared with Stratospheric Aerosol Gas Experiment (SAGE) II (versions 6.2 and 7.0) and Halogen Occultation Experiment (HALOE) satellite measurements to investigate differences between SAGE II/HALOE-measured extinction and derived surface area and OPC-derived extinction and surface area. Coincident OPC and SAGE II measurements are compared for a volcanic (1991-1996) and nonvolcanic (1997 2005) period. OPC calculated extinctions agree with SAGE II measurements, within instrumental uncertainty, during the volcanic period, but have been a factor of 2 low during the nonvolcanic period. Three systematic errors associated with the OPC measurements, anisokineticity, inlet particle evaporation, and counting efficiency, were investigated. An overestimation of the OPC counting efficiency is found to be the major source of systematic error. With this correction OPC calculated extinction increases by 15 30% (30 50%) for the volcanic (nonvolcanic) measurements. These changes significantly improve the comparison with SAGE II and HALOE extinctions in the nonvolcanic cases but slightly degrade the agreement in the volcanic period. These corrections have impacts on OPC-derived surface area density, exacerbating the poor agreement between OPC and SAGE II (version 6.2) surface areas. This disparity is reconciled with SAGE II version 7.0 surface areas. For both the volcanic and nonvolcanic cases these changes in OPC counting efficiency and in the operational SAGE II surface area algorithm leave the derived surface areas from both platforms in significantly better agreement and within the 40% precision of the OPC moment calculations.

  13. The Late Ordovician Extinction: How it became the best understood of the five major extinctions.

    NASA Astrophysics Data System (ADS)

    Sheehan, P.

    2003-04-01

    The end Ordovician extinction has become arguably the best-understood major extinction event in Earth History. A plethora of workers have established the pattern of faunal change and causes of the extinction with remarkably little disagreement. The first indication of increased extinction at the end of the Ordovician was a graph of global diversity patterns by Norman Newell in 1967, although he did not recognize it as a major event. The presence of a major extinction event became clear as William Berry and Art Boucot assembled data for Silurian correlation charts in the late 1960s. The first reports of North African glaciation in the late 1960s provided a cause for the extinction and study of the event snowballed. It was no accident that recognition of the extinction began in North America, because it was there that the extinction completely overturned faunas in the epicontinental seas. Glacio-eustatic regression of shallow seaway coincided with the disappearance of endemic Laurentian faunas and replacement by a highly cosmopolitan fauna in the Silurian. Once the event was established in North America, paleontologists soon found evidence of the event around the globe. The well-documented Hirnantia Fauna was found to correspond to the glacial interval, and Pat Brenchley soon recognized that there were two pulses of extinction, at the beginning and end of the glaciation. At the same time that the faunal changes were being documented geologic studies of the glaciation provided information on the environmental changes associated with the extinction. The timing of the glacial maximum was established in Africa and by the presence of dropstones in high latitude marine rocks. The 1990s saw geochemical techniques employed that allowed examination of atmospheric CO2 and temperature changes. In many places carbonate deposition declined. Glacio-eustatic regression was obvious in many areas, and a sea-level decline in the range of 50-100 m was established. Shallow

  14. Extinction rates in North American freshwater fishes, 1900-2010

    USGS Publications Warehouse

    Burkhead, Noel M.

    2012-01-01

    Widespread evidence shows that the modern rates of extinction in many plants and animals exceed background rates in the fossil record. In the present article, I investigate this issue with regard to North American freshwater fishes. From 1898 to 2006, 57 taxa became extinct, and three distinct populations were extirpated from the continent. Since 1989, the numbers of extinct North American fishes have increased by 25%. From the end of the nineteenth century to the present, modern extinctions varied by decade but significantly increased after 1950 (post-1950s mean = 7.5 extinct taxa per decade). In the twentieth century, freshwater fishes had the highest extinction rate worldwide among vertebrates. The modern extinction rate for North American freshwater fishes is conservatively estimated to be 877 times greater than the background extinction rate for freshwater fishes (one extinction every 3 million years). Reasonable estimates project that future increases in extinctions will range from 53 to 86 species by 2050.

  15. Linking Cholinergic Interneurons, Synaptic Plasticity, and Behavior during the Extinction of a Cocaine-Context Association.

    PubMed

    Lee, Junuk; Finkelstein, Joel; Choi, Jung Yoon; Witten, Ilana B

    2016-06-01

    Despite the fact that cholinergic interneurons are a key cell type within the nucleus accumbens, a relationship between synaptic plasticity and the in vivo activity of cholinergic interneurons remains to be established. Here, we identify a three-way link between the activity of cholinergic interneurons, synaptic plasticity, and learning in mice undergoing the extinction of a cocaine-context association. We found that activity of cholinergic interneurons regulates extinction learning for a cocaine-context association and generates a sustained reduction in glutamatergic presynaptic strength onto medium spiny neurons. Interestingly, activation of cholinergic interneurons does not support reinforcement learning or plasticity by itself, suggesting that these neurons have a modulatory rather than a reinforcing function. PMID:27210555

  16. Elevational distribution and extinction risk in birds.

    PubMed

    White, Rachel L; Bennett, Peter M

    2015-01-01

    Mountainous regions are hotspots of terrestrial biodiversity. Unlike islands, which have been the focus of extensive research on extinction dynamics, fewer studies have examined mountain ranges even though they face increasing threats from human pressures - notably habitat conversion and climate change. Limits to the taxonomic and geographical extent and resolution of previously available information have precluded an explicit assessment of the relative role of elevational distribution in determining extinction risk. We use a new global species-level avian database to quantify the influence of elevational distribution (range, maximum and midpoint) on extinction risk in birds at the global scale. We also tested this relationship within biogeographic realms, higher taxonomic levels, and across phylogenetic contrasts. Potential confounding variables (i.e. phylogenetic, distributional, morphological, life history and niche breadth) were also tested and controlled for. We show that the three measures of elevational distribution are strong negative predictors of avian extinction risk, with elevational range comparable and complementary to that of geographical range size. Extinction risk was also found to be positively associated with body weight, development and adult survival, but negatively associated with reproduction and niche breadth. The robust and consistent findings from this study demonstrate the importance of elevational distribution as a key driver of variation in extinction dynamics in birds. Our results also highlight elevational distribution as a missing criterion in current schemes for quantifying extinction risk and setting species conservation priorities in birds. Further research is recommended to test for generality across non-avian taxa, which will require an advance in our knowledge of species' current elevational ranges and increased efforts to digitise and centralise such data. PMID:25849620

  17. Conservation Risks: When Will Rhinos be Extinct?

    PubMed

    Haas, Timothy C; Ferreira, Sam M

    2016-08-01

    We develop a risk intelligence system for biodiversity enterprises. Such enterprises depend on a supply of endangered species for their revenue. Many of these enterprises, however, cannot purchase a supply of this resource and are largely unable to secure the resource against theft in the form of poaching. Because replacements are not available once a species becomes extinct, insurance products are not available to reduce the risk exposure of these enterprises to an extinction event. For many species, the dynamics of anthropogenic impacts driven by economic as well as noneconomic values of associated wildlife products along with their ecological stressors can help meaningfully predict extinction risks. We develop an agent/individual-based economic-ecological model that captures these effects and apply it to the case of South African rhinos. Our model uses observed rhino dynamics and poaching statistics. It seeks to predict rhino extinction under the present scenario. This scenario has no legal horn trade, but allows live African rhino trade and legal hunting. Present rhino populations are small and threatened by a rising onslaught of poaching. This present scenario and associated dynamics predicts continued decline in rhino population size with accelerated extinction risks of rhinos by 2036. Our model supports the computation of extinction risks at any future time point. This capability can be used to evaluate the effectiveness of proposed conservation strategies at reducing a species' extinction risk. Models used to compute risk predictions, however, need to be statistically estimated. We point out that statistically fitting such models to observations will involve massive numbers of observations on consumer behavior and time-stamped location observations on thousands of animals. Finally, we propose Big Data algorithms to perform such estimates and to interpret the fitted model's output. PMID:26340794

  18. Elevational Distribution and Extinction Risk in Birds

    PubMed Central

    White, Rachel L.; Bennett, Peter M.

    2015-01-01

    Mountainous regions are hotspots of terrestrial biodiversity. Unlike islands, which have been the focus of extensive research on extinction dynamics, fewer studies have examined mountain ranges even though they face increasing threats from human pressures – notably habitat conversion and climate change. Limits to the taxonomic and geographical extent and resolution of previously available information have precluded an explicit assessment of the relative role of elevational distribution in determining extinction risk. We use a new global species-level avian database to quantify the influence of elevational distribution (range, maximum and midpoint) on extinction risk in birds at the global scale. We also tested this relationship within biogeographic realms, higher taxonomic levels, and across phylogenetic contrasts. Potential confounding variables (i.e. phylogenetic, distributional, morphological, life history and niche breadth) were also tested and controlled for. We show that the three measures of elevational distribution are strong negative predictors of avian extinction risk, with elevational range comparable and complementary to that of geographical range size. Extinction risk was also found to be positively associated with body weight, development and adult survival, but negatively associated with reproduction and niche breadth. The robust and consistent findings from this study demonstrate the importance of elevational distribution as a key driver of variation in extinction dynamics in birds. Our results also highlight elevational distribution as a missing criterion in current schemes for quantifying extinction risk and setting species conservation priorities in birds. Further research is recommended to test for generality across non-avian taxa, which will require an advance in our knowledge of species’ current elevational ranges and increased efforts to digitise and centralise such data. PMID:25849620

  19. Low-Cost Avoidance Behaviors are Resistant to Fear Extinction in Humans

    PubMed Central

    Vervliet, Bram; Indekeu, Ellen

    2015-01-01

    Elevated levels of fear and avoidance are core symptoms across the anxiety disorders. It has long been known that fear serves to motivate avoidance. Consequently, fear extinction has been the primary focus in pre-clinical anxiety research for decades, under the implicit assumption that removing the motivator of avoidance (fear) would automatically mitigate the avoidance behaviors as well. Although this assumption has intuitive appeal, it has received little scientific scrutiny. The scarce evidence from animal studies is mixed, while the assumption remains untested in humans. The current study applied an avoidance conditioning protocol in humans to investigate the effects of fear extinction on the persistence of low-cost avoidance. Online danger-safety ratings and skin conductance responses documented the dynamics of conditioned fear across avoidance and extinction phases. Anxiety- and avoidance-related questionnaires explored individual differences in rates of avoidance. Participants first learned to click a button during a predictive danger signal, in order to cancel an upcoming aversive electrical shock (avoidance conditioning). Next, fear extinction was induced by presenting the signal in the absence of shocks while button-clicks were prevented (by removing the button in Experiment 1, or by instructing not to click the button in Experiment 2). Most importantly, post-extinction availability of the button caused a significant return of avoidant button-clicks. In addition, trait-anxiety levels correlated positively with rates of avoidance during a predictive safety signal, and with the rate of pre- to post-extinction decrease during this signal. Fear measures gradually decreased during avoidance conditioning, as participants learned that button-clicks effectively canceled the shock. Preventing button-clicks elicited a sharp increase in fear, which subsequently extinguished. Fear remained low during avoidance testing, but danger-safety ratings increased again when

  20. Low-Cost Avoidance Behaviors are Resistant to Fear Extinction in Humans.

    PubMed

    Vervliet, Bram; Indekeu, Ellen

    2015-01-01

    Elevated levels of fear and avoidance are core symptoms across the anxiety disorders. It has long been known that fear serves to motivate avoidance. Consequently, fear extinction has been the primary focus in pre-clinical anxiety research for decades, under the implicit assumption that removing the motivator of avoidance (fear) would automatically mitigate the avoidance behaviors as well. Although this assumption has intuitive appeal, it has received little scientific scrutiny. The scarce evidence from animal studies is mixed, while the assumption remains untested in humans. The current study applied an avoidance conditioning protocol in humans to investigate the effects of fear extinction on the persistence of low-cost avoidance. Online danger-safety ratings and skin conductance responses documented the dynamics of conditioned fear across avoidance and extinction phases. Anxiety- and avoidance-related questionnaires explored individual differences in rates of avoidance. Participants first learned to click a button during a predictive danger signal, in order to cancel an upcoming aversive electrical shock (avoidance conditioning). Next, fear extinction was induced by presenting the signal in the absence of shocks while button-clicks were prevented (by removing the button in Experiment 1, or by instructing not to click the button in Experiment 2). Most importantly, post-extinction availability of the button caused a significant return of avoidant button-clicks. In addition, trait-anxiety levels correlated positively with rates of avoidance during a predictive safety signal, and with the rate of pre- to post-extinction decrease during this signal. Fear measures gradually decreased during avoidance conditioning, as participants learned that button-clicks effectively canceled the shock. Preventing button-clicks elicited a sharp increase in fear, which subsequently extinguished. Fear remained low during avoidance testing, but danger-safety ratings increased again when

  1. Parental Leave Policies and Parents’ Employment and Leave-Taking

    PubMed Central

    Han, Wen-Jui; Ruhm, Christopher; Waldfogel, Jane

    2009-01-01

    We describe trends in maternal employment and leave-taking after birth of a newborn and analyze the extent to which these behaviors are influenced by parental leave policies. Data are from the June Current Population Survey (CPS) Fertility Supplements, merged with other months of the CPS, and cover the period 1987 to 1994. This time-span is one during which parental leave legislation expanded at both the state and federal level. We also provide the first comprehensive examination of employment and leave-taking by fathers of infants. Our main finding is that leave expansions are associated with increased leave-taking by both mothers and fathers. The magnitudes of the changes are small in absolute terms but large relative to the baseline for men and much greater for college-educated or married mothers than for their less-educated or single counterparts. PMID:19090048

  2. The use of cognitive enhancers in animal models of fear extinction.

    PubMed

    Kaplan, Gary B; Moore, Katherine A

    2011-08-01

    In anxiety disorders, such as posttraumatic stress disorders and phobias, classical conditioning pairs natural (unconditioned) fear-eliciting stimuli with contextual or discrete cues resulting in enduring fear responses to multiple stimuli. Extinction is an active learning process that results in a reduction of conditioned fear responses after conditioned stimuli are no longer paired with unconditioned stimuli. Fear extinction often produces incomplete effects and this highlights the relative permanence of bonds between conditioned stimuli and conditioned fear responses. The animal research literature is rich in its demonstration of cognitive enhancing agents that alter fear extinction. This review specifically examines the fear extinguishing effects of cognitive enhancers that act on gamma-aminobutyric acid (GABA), glutamatergic, cholinergic, adrenergic, dopaminergic, and cannabinoid signaling pathways. It also examines the effects of compounds that alter epigenetic and neurotrophic mechanisms in fear extinction. Of these cognitive enhancers, glutamatergic N-methyl d-aspartate (NMDA) receptor agonists, such as D-cycloserine, have enhanced fear extinction in a context-, dose- and time-dependent manner. Agents that function as glutamatergic α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor agonists, alpha2-adrenergic receptor antagonists (such as yohimbine), neurotrophic factors (brain derived neurotrophic factor or BDNF) and histone deacetylase inhibitors (valproate and sodium butyrate) also improve fear extinction in animals. However, some have anxiogenic effects and their contextual and temporal effects need to be more reliably demonstrated. Various cognitive enhancers produce changes in cortico-amygdala synaptic plasticity through multiple mechanisms and these neural changes enhance fear extinction. We need to better define the changes in neural plasticity produced by these agents in order to develop more effective compounds. In the clinical

  3. Fear extinction and BDNF: translating animal models of PTSD to the clinic.

    PubMed

    Andero, R; Ressler, K J

    2012-07-01

    Brain-derived neurotrophic factor (BDNF) is the most studied neurotrophin involved in synaptic plasticity processes that are required for long-term learning and memory. Specifically, BDNF gene expression and activation of its high-affinity tropomyosin-related kinase B (TrkB) receptor are necessary in the amygdala, hippocampus and prefrontal cortex for the formation of emotional memories, including fear memories. Among the psychiatric disorders with altered fear processing, there is post-traumatic stress disorder (PTSD) which is characterized by an inability to extinguish fear memories. Since BDNF appears to enhance extinction of fear, targeting impaired extinction in anxiety disorders such as PTSD via BDNF signalling may be an important and novel way to enhance treatment efficacy. The aim of this review is to provide a translational point of view that stems from findings in the BDNF regulation of synaptic plasticity and fear extinction. In addition, there are different systems that seem to alter fear extinction through BDNF modulation like the endocannabinoid system and the hypothalamic-pituitary adrenal axis. Recent work also finds that the pituitary adenylate cyclase-activating polypeptide and PAC1 receptor, which are upstream of BDNF activation, may be implicated in PTSD. Especially interesting are data that exogenous fear extinction enhancers such as antidepressants, histone deacetylases inhibitors and D-cycloserine, a partial N-methyl d-aspartate agonist, may act through or in concert with the BDNF-TrkB system. Finally, we review studies where recombinant BDNF and a putative TrkB agonist, 7,8-dihydroxyflavone, may enhance extinction of fear. These approaches may lead to novel agents that improve extinction in animal models and eventually humans. PMID:22530815

  4. Effects of Extinction on Classical Conditioning and Conditioning-Specific Reflex Modification of Rabbit Heart Rate

    PubMed Central

    Burhans, Lauren B.; Smith-Bell, Carrie; Schreurs, Bernard G.

    2009-01-01

    Understanding the mechanisms of fear extinction has become increasingly important for treating a number of disorders, particularly post-traumatic stress disorder. Conditioning of rabbit heart rate (HR) is an established model for studying fear, yet little is known about procedures for extinguishing it other than repeated presentations of cue(s) associated with the fear-inducing event. The following study examined the effects of conditioned stimulus (CS) alone, unconditioned stimulus (US) alone, unpaired CS/US presentations, continued CS-US pairings, or no further stimulation on rabbit HR following HR conditioning. We have previously shown the rabbit HR response to the US can change as a function of learning when measured in the absence of the CS, a phenomenon referred to as conditioning-specific reflex modification (CRM). More specifically, the HR exhibits a deceleration in response to the US reminiscent of the conditioned bradycardia that develops to the CS. Consequently, the following study also examined the effects of extinction treatments on HR CRM. For HR conditioned responses (CRs), CS-alone and unpaired CS/US presentations were the most successful extinction treatments. For HR CRM, all conditions led to a reduction in CRM except for a subset of rabbits that maintained high levels following unpaired extinction, indicating a dissociation between extinction of HR CRs and CRM. The findings highlight the parameters of HR extinction, the transient nature of HR CRM, vagal involvement in both acquisition and extinction of HR CRM, and suggest that HR CRM cannot be fully explained as a CR that has generalized from the CS to the US. PMID:19747508

  5. Drivers of extinction risk in African mammals: the interplay of distribution state, human pressure, conservation response and species biology

    PubMed Central

    Di Marco, Moreno; Buchanan, Graeme M.; Szantoi, Zoltan; Holmgren, Milena; Grottolo Marasini, Gabriele; Gross, Dorit; Tranquilli, Sandra; Boitani, Luigi; Rondinini, Carlo

    2014-01-01

    Although conservation intervention has reversed the decline of some species, our success is outweighed by a much larger number of species moving towards extinction. Extinction risk modelling can identify correlates of risk and species not yet recognized to be threatened. Here, we use machine learning models to identify correlates of extinction risk in African terrestrial mammals using a set of variables belonging to four classes: species distribution state, human pressures, conservation response and species biology. We derived information on distribution state and human pressure from satellite-borne imagery. Variables in all four classes were identified as important predictors of extinction risk, and interactions were observed among variables in different classes (e.g. level of protection, human threats, species distribution ranges). Species biology had a key role in mediating the effect of external variables. The model was 90% accurate in classifying extinction risk status of species, but in a few cases the observed and modelled extinction risk mismatched. Species in this condition might suffer from an incorrect classification of extinction risk (hence require reassessment). An increased availability of satellite imagery combined with improved resolution and classification accuracy of the resulting maps will play a progressively greater role in conservation monitoring. PMID:24733953

  6. Extinction of drug- and withdrawal-paired cues in animal models: relevance to the treatment of addiction.

    PubMed

    Myers, Karyn M; Carlezon, William A

    2010-11-01

    Conditioned drug craving and withdrawal elicited by cues paired with drug use or acute withdrawal are among the many factors contributing to compulsive drug taking. Understanding how to stop these cues from having these effects is a major goal of addiction research. Extinction is a form of learning in which associations between cues and the events they predict are weakened by exposure to the cues in the absence of those events. Evidence from animal models suggests that conditioned responses to drug cues can be extinguished, although the degree to which this occurs in humans is controversial. Investigations into the neurobiological substrates of extinction of conditioned drug craving and withdrawal may facilitate the successful use of drug cue extinction within clinical contexts. While this work is still in the early stages, there are indications that extinction of drug- and withdrawal-paired cues shares neural mechanisms with extinction of conditioned fear. Using the fear extinction literature as a template, it is possible to organize the observations on drug cue extinction into a cohesive framework. PMID:20109490

  7. Human fear extinction and return of fear using reconsolidation update mechanisms: The contribution of on-line expectancy ratings

    PubMed Central

    Warren, Victor Taylor; Anderson, Kemp M.; Kwon, Cliffe; Bosshardt, Lauren; Jovanovic, Tanja; Bradley, Bekh; Norrholm, Seth Davin

    2015-01-01

    Disruption of the reconsolidation of conditioned fear memories has been suggested as a non-pharmacological means of preventing the return of learned fear in human populations. A reconsolidation update paradigm was developed in which a reconsolidation window is opened by a single isolated retrieval trial of a previously reinforced CS+ which is then followed by Extinction Training within that window. However, follow-up studies in humans using multi-methods fear conditioning indices (e.g., fear-potentiated startle, skin conductance, US-expectancy) have failed to replicate the retrieval + extinction effects. In the present study, we further investigated the retrieval + extinction reconsolidation update paradigm by directly comparing the acquisition, extinction, and return of fear-potentiated startle in the absence or presence of US-expectancy measures (using a trial-by-trial response keypad) with and without retrieval of a previously acquired CS-US association. Participants were fear conditioned to two visual cue CS+'s, one of which was presented as a single, isolated retrieval trial before Extinction Training and one that was extinguished as usual. The results show that the inclusion of US-expectancy measures strengthens the CS–US association to provide enhanced fear conditioning and maintenance of fear memories over the experimental sessions. In addition, in the groups that used on-line US-expectancy measures, the retrieval + extinction procedure reduced reinstatement of fear-potentiated startle to both previously reinforced CS+'s, as compared to the extinction as usual group. PMID:24183839

  8. Extinctions. Paleontological baselines for evaluating extinction risk in the modern oceans.

    PubMed

    Finnegan, Seth; Anderson, Sean C; Harnik, Paul G; Simpson, Carl; Tittensor, Derek P; Byrnes, Jarrett E; Finkel, Zoe V; Lindberg, David R; Liow, Lee Hsiang; Lockwood, Rowan; Lotze, Heike K; McClain, Craig R; McGuire, Jenny L; O'Dea, Aaron; Pandolfi, John M

    2015-05-01

    Marine taxa are threatened by anthropogenic impacts, but knowledge of their extinction vulnerabilities is limited. The fossil record provides rich information on past extinctions that can help predict biotic responses. We show that over 23 million years, taxonomic membership and geographic range size consistently explain a large proportion of extinction risk variation in six major taxonomic groups. We assess intrinsic risk-extinction risk predicted by paleontologically calibrated models-for modern genera in these groups. Mapping the geographic distribution of these genera identifies coastal biogeographic provinces where fauna with high intrinsic risk are strongly affected by human activity or climate change. Such regions are disproportionately in the tropics, raising the possibility that these ecosystems may be particularly vulnerable to future extinctions. Intrinsic risk provides a prehuman baseline for considering current threats to marine biodiversity. PMID:25931558

  9. Water isotopologues in leaves

    NASA Astrophysics Data System (ADS)

    Cuntz, M.; Ogée, J.; Farquhar, G. D.; Cernusak, L. A.; Peylin, P.; Bariac, T.

    2007-12-01

    Leaf water isotope enrichment is a cornerstone of a variety of isotopic applications. It imprints on different substances such as atmospheric CO2, O2, and plant organic matter. But different applications use enrichment in different parts of the leaf and weighted by different fluxes. For example, leaf organic matter is determined by the assimilation-weighted average bulk water enrichment. Atmospheric CO2 and O2 are determined by the enrichment near the evaporating sites, either weighted by the one-way CO2 flux from the stomata to the atmosphere or by electron transport, resp. These applications of leaf water enrichment are used from the leaf level up to global scales. It is therefore essential to understand the time course of leaf water enrichment at both the evaporating sites and in the mesophyll but also to asses the suitability of simple models such as the Craig & Gordon (1965) steady-state prediction or the Dongmann et al. (1974) non-steady-state model. We describe here advection and diffusion of water isotopologues in leaves in the non-steady state. We first show how this relates to earlier non-steady state bulk leaf water enrichment models. The adv.-diff. model compares very well with observations of bulk mesophyll water during the whole diel cycle. It compares well with the enrichment at the evaporative sites during the day but shows some deviations at night. It is clear that night-time stomatal conductance should be measured in the future. However, varying mesophyll water volume did not seem critical for a good prediction. In addition, observations of single diurnal cycles do not constrain the effective length in the mesophyll. Finally, we show when simpler models of leaf water enrichment are suitable for applications of leaf water isotopes once weighted with the appropriate gas exchange flux. We then present a two-dimensional adv.-diff. description of leaf water enrichment along monocot leaves. The model reproduces well all published measurements along

  10. Effects of hippocampal state-contingent trial presentation on hippocampus-dependent nonspatial classical conditioning and extinction.

    PubMed

    Nokia, Miriam S; Wikgren, Jan

    2014-04-23

    Hippocampal local field potentials are characterized by two mutually exclusive states: one characterized by regular θ oscillations (∼4-8 Hz) and the other by irregular sharp-wave ripples. Presenting stimuli during dominant θ oscillations leads to expedited learning, suggesting that θ indexes a state in which encoding is most effective. However, ripple-contingent training also expedites learning, suggesting that any discrete brain state, much like the external context, can affect learning. We trained adult rabbits in trace eyeblink conditioning, a hippocampus-dependent nonspatial task, followed by extinction. Trials were delivered either in the presence or absence of θ or regardless of hippocampal state. Conditioning in the absence of θ led to more animals learning, although learning was slower compared with a yoked control group. Contrary to expectations, conditioning in the presence of θ did not affect learning. However, extinction was expedited both when it was conducted contingent on θ and when it was conducted in a state contrary to that used to trigger trials during conditioning. Strong phase-locking of hippocampal θ-band responses to the conditioned stimulus early on during conditioning predicted good learning. No such connection was observed during extinction. Our results suggest that any consistent hippocampal oscillatory state can potentially be used to regulate learning. However, the effects depend on the specific state and task at hand. Finally, much like the external environment, the ongoing neural state appears to act as a context for learning and memory retrieval. PMID:24760859

  11. Disease and the dynamics of extinction.

    PubMed

    McCallum, Hamish

    2012-10-19

    Invading infectious diseases can, in theory, lead to the extinction of host populations, particularly if reservoir species are present or if disease transmission is frequency-dependent. The number of historic or prehistoric extinctions that can unequivocally be attributed to infectious disease is relatively small, but gathering firm evidence in retrospect is extremely difficult. Amphibian chytridiomycosis and Tasmanian devil facial tumour disease (DFTD) are two very different infectious diseases that are currently threatening to cause extinctions in Australia. These provide an unusual opportunity to investigate the processes of disease-induced extinction and possible management strategies. Both diseases are apparently recent in origin. Tasmanian DFTD is entirely host-specific but potentially able to cause extinction because transmission depends weakly, if at all, on host density. Amphibian chytridiomycosis has a broad host range but is highly pathogenic only to some populations of some species. At present, both diseases can only be managed by attempting to isolate individuals or populations from disease. Management options to accelerate the process of evolution of host resistance or tolerance are being investigated in both cases. Anthropogenic changes including movement of diseases and hosts, habitat destruction and fragmentation and climate change are likely to increase emerging disease threats to biodiversity and it is critical to further develop strategies to manage these threats. PMID:22966138

  12. Disease and the dynamics of extinction

    PubMed Central

    McCallum, Hamish

    2012-01-01

    Invading infectious diseases can, in theory, lead to the extinction of host populations, particularly if reservoir species are present or if disease transmission is frequency-dependent. The number of historic or prehistoric extinctions that can unequivocally be attributed to infectious disease is relatively small, but gathering firm evidence in retrospect is extremely difficult. Amphibian chytridiomycosis and Tasmanian devil facial tumour disease (DFTD) are two very different infectious diseases that are currently threatening to cause extinctions in Australia. These provide an unusual opportunity to investigate the processes of disease-induced extinction and possible management strategies. Both diseases are apparently recent in origin. Tasmanian DFTD is entirely host-specific but potentially able to cause extinction because transmission depends weakly, if at all, on host density. Amphibian chytridiomycosis has a broad host range but is highly pathogenic only to some populations of some species. At present, both diseases can only be managed by attempting to isolate individuals or populations from disease. Management options to accelerate the process of evolution of host resistance or tolerance are being investigated in both cases. Anthropogenic changes including movement of diseases and hosts, habitat destruction and fragmentation and climate change are likely to increase emerging disease threats to biodiversity and it is critical to further develop strategies to manage these threats. PMID:22966138

  13. Extinction as the loss of evolutionary history

    PubMed Central

    Erwin, Douglas H.

    2008-01-01

    Current plant and animal diversity preserves at most 1–2% of the species that have existed over the past 600 million years. But understanding the evolutionary impact of these extinctions requires a variety of metrics. The traditional measurement is loss of taxa (species or a higher category) but in the absence of phylogenetic information it is difficult to distinguish the evolutionary depth of different patterns of extinction: the same species loss can encompass very different losses of evolutionary history. Furthermore, both taxic and phylogenetic measures are poor metrics of morphologic disparity. Other measures of lost diversity include: functional diversity, architectural components, behavioral and social repertoires, and developmental strategies. The canonical five mass extinctions of the Phanerozoic reveals the loss of different, albeit sometimes overlapping, aspects of loss of evolutionary history. The end-Permian mass extinction (252 Ma) reduced all measures of diversity. The same was not true of other episodes, differences that may reflect their duration and structure. The construction of biodiversity reflects similarly uneven contributions to each of these metrics. Unraveling these contributions requires greater attention to feedbacks on biodiversity and the temporal variability in their contribution to evolutionary history. Taxic diversity increases after mass extinctions, but the response by other aspects of evolutionary history is less well studied. Earlier views of postextinction biotic recovery as the refilling of empty ecospace fail to capture the dynamics of this diversity increase. PMID:18695248

  14. Effectiveness of sensory stimulation on tactile extinction.

    PubMed

    Nico, D

    1999-07-01

    Eleven brain-damaged patients with extinction were asked to report double tactile stimuli before, during, and after optokinetic stimulation and transcutaneous electrical stimulation of the posterior neck region. The goal of the study was to test whether tactile extinction is sensitive to these experimental manipulations in order to better understand the nature of the disorder. Both of these sensory stimulations are known to be effective in modulating only higher-order (cognitive) disorders of spatial coding, such as visual hemineglect, deficit of position sense, hemianesthesia, etc. When applied to the side contralateral to the cerebral lesion, both optokinetic and transcutaneous electrical stimulation significantly affected patients' performances, increasing the amount of detections of contralesional double stimuli. A tendency towards worse performance was observed when sensory stimulation was applied to the ipsilesional side. The reported effectiveness in reducing tactile extinction suggests that the deficit can not be fully ascribed to a peripheral sensory disorder and that it reflects damage to a higher-order cognitive function involved in contralesional space representation or in the deployment of attention to that side of space. The nature of the close relationship between extinction and hemineglect is also discussed from the point of view of extinction as a deficit of space coding. PMID:10424416

  15. Saturated Dispersive Extinction Theory of Red Shift

    NASA Astrophysics Data System (ADS)

    Wang, Ling Jun

    2012-03-01

    The Dispersive Extinction Theory (DET) proposed by WangfootnotetextWang, Ling Jun, Physics Essays, 18, No. 2, (2005). offers an alternative to the Big Bang. According to DET, the cosmic red shift is caused by the dispersive extinction of the star light during the propagation from the stars to the earth, instead of being caused by the Doppler shift due to the expansion of the universe.footnotetextHubble, E., Astrophys. J. 64, 321 (1926).^,footnotetextHubble, E., The Realm of the Nebulae, (Yale University Press, New Haven, 1936). DET allows an infinite, stable, non expanding universe, and is immune of the fundamental problems inherent to the Big Bang such as the horizon problem, the extreme violation of the conservation of mass, energy and charge, and the geocentric nature which violates the principle of relativity.footnotetextWang, Ling Jun, Physics Essays, 20, No. 2, (2007). The scenario dealt with in Reference (1) is a one in which the extinction by the space medium is not saturated. This work deals with a different scenario when the extinction is saturated. The saturated extinction causes limited energy loss, and the star light can travel a much greater distance than in the unsaturated scenario.

  16. Fluoxetine Facilitates Fear Extinction Through Amygdala Endocannabinoids

    PubMed Central

    Gunduz-Cinar, Ozge; Flynn, Shaun; Brockway, Emma; Kaugars, Katherine; Baldi, Rita; Ramikie, Teniel S; Cinar, Resat; Kunos, George; Patel, Sachin; Holmes, Andrew

    2016-01-01

    Pharmacologically elevating brain endocannabinoids (eCBs) share anxiolytic and fear extinction-facilitating properties with classical therapeutics, including the selective serotonin reuptake inhibitor, fluoxetine. There are also known functional interactions between the eCB and serotonin systems and preliminary evidence that antidepressants cause alterations in brain eCBs. However, the potential role of eCBs in mediating the facilitatory effects of fluoxetine on fear extinction has not been established. Here, to test for a possible mechanistic contribution of eCBs to fluoxetine's proextinction effects, we integrated biochemical, electrophysiological, pharmacological, and behavioral techniques, using the extinction-impaired 129S1/Sv1mJ mouse strain. Chronic fluoxetine treatment produced a significant and selective increase in levels of anandamide in the BLA, and an associated decrease in activity of the anandamide-catabolizing enzyme, fatty acid amide hydrolase. Slice electrophysiological recordings showed that fluoxetine-induced increases in anandamide were associated with the amplification of eCB-mediated tonic constraint of inhibitory, but not excitatory, transmission in the BLA. Behaviorally, chronic fluoxetine facilitated extinction retrieval in a manner that was prevented by systemic or BLA-specific blockade of CB1 receptors. In contrast to fluoxetine, citalopram treatment did not increase BLA eCBs or facilitate extinction. Taken together, these findings reveal a novel, obligatory role for amygdala eCBs in the proextinction effects of a major pharmacotherapy for trauma- and stressor-related disorders and anxiety disorders. PMID:26514583

  17. Fluoxetine Facilitates Fear Extinction Through Amygdala Endocannabinoids.

    PubMed

    Gunduz-Cinar, Ozge; Flynn, Shaun; Brockway, Emma; Kaugars, Katherine; Baldi, Rita; Ramikie, Teniel S; Cinar, Resat; Kunos, George; Patel, Sachin; Holmes, Andrew

    2016-05-01

    Pharmacologically elevating brain endocannabinoids (eCBs) share anxiolytic and fear extinction-facilitating properties with classical therapeutics, including the selective serotonin reuptake inhibitor, fluoxetine. There are also known functional interactions between the eCB and serotonin systems and preliminary evidence that antidepressants cause alterations in brain eCBs. However, the potential role of eCBs in mediating the facilitatory effects of fluoxetine on fear extinction has not been established. Here, to test for a possible mechanistic contribution of eCBs to fluoxetine's proextinction effects, we integrated biochemical, electrophysiological, pharmacological, and behavioral techniques, using the extinction-impaired 129S1/Sv1mJ mouse strain. Chronic fluoxetine treatment produced a significant and selective increase in levels of anandamide in the BLA, and an associated decrease in activity of the anandamide-catabolizing enzyme, fatty acid amide hydrolase. Slice electrophysiological recordings showed that fluoxetine-induced increases in anandamide were associated with the amplification of eCB-mediated tonic constraint of inhibitory, but not excitatory, transmission in the BLA. Behaviorally, chronic fluoxetine facilitated extinction retrieval in a manner that was prevented by systemic or BLA-specific blockade of CB1 receptors. In contrast to fluoxetine, citalopram treatment did not increase BLA eCBs or facilitate extinction. Taken together, these findings reveal a novel, obligatory role for amygdala eCBs in the proextinction effects of a major pharmacotherapy for trauma- and stressor-related disorders and anxiety disorders. PMID:26514583

  18. Extinction risks of Amazonian plant species.

    PubMed

    Feeley, Kenneth J; Silman, Miles R

    2009-07-28

    Estimates of the number, and preferably the identity, of species that will be threatened by land-use change and habitat loss are an invaluable tool for setting conservation priorities. Here, we use collections data and ecoregion maps to generate spatially explicit distributions for more than 40,000 vascular plant species from the Amazon basin (representing more than 80% of the estimated Amazonian plant diversity). Using the distribution maps, we then estimate the rates of habitat loss and associated extinction probabilities due to land-use changes as modeled under 2 disturbance scenarios. We predict that by 2050, human land-use practices will have reduced the habitat available to Amazonian plant species by approximately 12-24%, resulting in 5-9% of species becoming "committed to extinction," significantly fewer than other recent estimates. Contrary to previous studies, we find that the primary determinant of habitat loss and extinction risk is not the size of a species' range, but rather its location. The resulting extinction risk estimates are a valuable conservation tool because they indicate not only the total percentage of Amazonian plant species threatened with extinction but also the degree to which individual species and habitats will be affected by current and future land-use changes. PMID:19617552

  19. Modelling the extinction of Steller's sea cow

    PubMed Central

    Turvey, S.T; Risley, C.L

    2005-01-01

    Steller's sea cow, a giant sirenian discovered in 1741 and extinct by 1768, is one of the few megafaunal mammal species to have died out during the historical period. The species is traditionally considered to have been exterminated by ‘blitzkrieg’-style direct overharvesting for food, but it has also been proposed that its extinction resulted from a sea urchin population explosion triggered by extirpation of local sea otter populations that eliminated the shallow-water kelps on which sea cows fed. Hunting records from eighteenth century Russian expeditions to the Commander Islands, in conjunction with life-history data extrapolated from dugongs, permit modelling of sea cow extinction dynamics. Sea cows were massively and wastefully overexploited, being hunted at over seven times the sustainable limit, and suggesting that the initial Bering Island sea cow population must have been higher than suggested by previous researchers to allow the species to survive even until 1768. Environmental changes caused by sea otter declines are unlikely to have contributed to this extinction event. This indicates that megafaunal extinctions can be effected by small bands of hunters using pre-industrial technologies, and highlights the catastrophic impact of wastefulness when overexploiting resources mistakenly perceived as ‘infinite’. PMID:17148336

  20. Modelling the extinction of Steller's sea cow.

    PubMed

    Turvey, S T; Risley, C L

    2006-03-22

    Steller's sea cow, a giant sirenian discovered in 1741 and extinct by 1768, is one of the few megafaunal mammal species to have died out during the historical period. The species is traditionally considered to have been exterminated by 'blitzkrieg'-style direct overharvesting for food, but it has also been proposed that its extinction resulted from a sea urchin population explosion triggered by extirpation of local sea otter populations that eliminated the shallow-water kelps on which sea cows fed. Hunting records from eighteenth century Russian expeditions to the Commander Islands, in conjunction with life-history data extrapolated from dugongs, permit modelling of sea cow extinction dynamics. Sea cows were massively and wastefully overexploited, being hunted at over seven times the sustainable limit, and suggesting that the initial Bering Island sea cow population must have been higher than suggested by previous researchers to allow the species to survive even until 1768. Environmental changes caused by sea otter declines are unlikely to have contributed to this extinction event. This indicates that megafaunal extinctions can be effected by small bands of hunters using pre-industrial technologies, and highlights the catastrophic impact of wastefulness when overexploiting resources mistakenly perceived as 'infinite'. PMID:17148336

  1. Mass Extinctions and Biosphere-Geosphere Stability

    NASA Astrophysics Data System (ADS)

    Rothman, Daniel; Bowring, Samuel

    2015-04-01

    Five times in the past 500 million years, mass extinctions have resulted in the loss of greater than three-fourths of living species. Each of these events is associated with significant environmental change recorded in the carbon-isotopic composition of sedimentary rocks. There are also many such environmental events in the geologic record that are not associated with mass extinctions. What makes them different? Two factors appear important: the size of the environmental perturbation, and the time scale over which it occurs. We show that the natural perturbations of Earth's carbon cycle during the past 500 million years exhibit a characteristic rate of change over two orders of magnitude in time scale. This characteristic rate is consistent with the maximum rate that limits quasistatic (i.e., near steady-state) evolution of the carbon cycle. We identify this rate with marginal stability, and show that mass extinctions occur on the fast, unstable side of the stability boundary. These results suggest that the great extinction events of the geologic past, and potentially a "sixth extinction" associated with modern environmental change, are characterized by common mechanisms of instability.

  2. 5 CFR 630.1205 - Intermittent leave or reduced leave schedule.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... REGULATIONS ABSENCE AND LEAVE Family and Medical Leave § 630.1205 Intermittent leave or reduced leave schedule... 5 Administrative Personnel 1 2012-01-01 2012-01-01 false Intermittent leave or reduced leave... reduced leave schedule unless the employee and the agency agree to do so. (b) Leave under §...

  3. 5 CFR 630.1204 - Intermittent leave or reduced leave schedule.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... REGULATIONS ABSENCE AND LEAVE Family and Medical Leave § 630.1204 Intermittent leave or reduced leave schedule... 5 Administrative Personnel 1 2011-01-01 2011-01-01 false Intermittent leave or reduced leave... reduced leave schedule unless the employee and the agency agree to do so. (b) Leave under § 630.1203(a)...

  4. 5 CFR 630.1205 - Intermittent leave or reduced leave schedule.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... REGULATIONS ABSENCE AND LEAVE Family and Medical Leave § 630.1205 Intermittent leave or reduced leave schedule... 5 Administrative Personnel 1 2014-01-01 2014-01-01 false Intermittent leave or reduced leave... reduced leave schedule unless the employee and the agency agree to do so. (b) Leave under §...

  5. 5 CFR 630.1205 - Intermittent leave or reduced leave schedule.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... REGULATIONS ABSENCE AND LEAVE Family and Medical Leave § 630.1205 Intermittent leave or reduced leave schedule... 5 Administrative Personnel 1 2013-01-01 2013-01-01 false Intermittent leave or reduced leave... reduced leave schedule unless the employee and the agency agree to do so. (b) Leave under §...

  6. 5 CFR 630.1204 - Intermittent leave or reduced leave schedule.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... REGULATIONS ABSENCE AND LEAVE Family and Medical Leave § 630.1204 Intermittent leave or reduced leave schedule... 5 Administrative Personnel 1 2010-01-01 2010-01-01 false Intermittent leave or reduced leave... reduced leave schedule unless the employee and the agency agree to do so. (b) Leave under § 630.1203(a)...

  7. Can fear extinction be enhanced? A review of pharmacological and behavioral findings.

    PubMed

    Fitzgerald, Paul J; Seemann, Jocelyn R; Maren, Stephen

    2014-06-01

    There is considerable interest, from both a basic and clinical standpoint, in gaining a greater understanding of how pharmaceutical or behavioral manipulations alter fear extinction in animals. Not only does fear extinction in rodents model exposure therapy in humans, where the latter is a cornerstone of behavioral intervention for anxiety disorders such as post-traumatic stress disorder and specific phobias, but also understanding more about extinction provides basic information into learning and memory processes and their underlying circuitry. In this paper, we briefly review three principal approaches that have been used to modulate extinction processes in animals and humans: a purely pharmacological approach, the more widespread approach of combining pharmacology with behavior, and a purely behavioral approach. The pharmacological studies comprise modulation by: brain derived neurotrophic factor (BDNF), d-cycloserine, serotonergic and noradrenergic drugs, neuropeptides, endocannabinoids, glucocorticoids, histone deacetylase (HDAC) inhibitors, and others. These studies strongly suggest that extinction can be modulated by drugs, behavioral interventions, or their combination, although not always in a lasting manner. We suggest that pharmacotherapeutic manipulations provide considerable promise for promoting effective and lasting fear reduction in individuals with anxiety disorders. This article is part of a Special Issue entitled 'Memory enhancement'. PMID:24374101

  8. Characterizing spatial extinction in an abbreviated version of the Barnes maze.

    PubMed

    Vargas-López, Viviana; Lamprea, Marisol R; Múnera, Alejandro

    2011-01-01

    Adult male Wistar rats were trained to find an escape box in the Barnes maze in order to characterize the extinction process of a learned spatial preference. To do so, once they had fully acquired the spatial task, they were repeatedly exposed to the maze without the escape box. Multiple behavioral measurements (grouped into motor skill and spatial preference indicators) were followed up throughout the complete training process. Animals gained efficiency in finding the escape box during acquisition, as indicated by the reduction in the time spent escaping from the maze, the number of errors, the length of the traveled path, and by the increase in exploration accuracy and execution speed. When their retention and preference were tested 24h later, all the subjects retained their enhanced performance efficiency and accuracy and displayed a clear-cut preference for the escape hole and its adjacent holes. Almost all motor skill indicators followed an inverse, though not monotonic, pattern during the extinction training, returning to basal levels after three trials without escape box, displaying a transient relapse during the fifth extinction trial. Preference indicators also followed a reverse pattern; however, it took seven trials for them to return to basal levels, relapsing during the eighth extinction trial. The abbreviated Barnes maze acquisition, evaluation, and extinction procedures described herein are useful tools for evaluating the effects of behavioral and/or pharmacological treatment on different stages of spatial memory, and could also be used for studying the neurophysiological and neurobiological underpinnings of this kind of memory. PMID:20708660

  9. Extinction procedure induces pruning of dendritic spines in CA1 hippocampal field depending on strength of training in rats

    PubMed Central

    Garín-Aguilar, María E.; Díaz-Cintra, Sofía; Quirarte, Gina L.; Aguilar-Vázquez, Azucena; Medina, Andrea C.; Prado-Alcalá, Roberto A.

    2012-01-01

    Numerous reports indicate that learning and memory of conditioned responses are accompanied by genesis of dendritic spines in the hippocampus, although there is a conspicuous lack of information regarding spine modifications after behavioral extinction. There is ample evidence that treatments that typically produce amnesia become innocuous when animals are submitted to a procedure of enhanced training. We now report that extinction of inhibitory avoidance (IA), trained with relatively low foot-shock intensities, induces pruning of dendritic spines along the length of the apical dendrites of hippocampal CA1 neurons. When animals are trained with a relatively high foot-shock there is a high resistance to extinction, and pruning in the proximal and medial segments of the apical dendrite are seen, while spine count in the distal dendrite remains normal. These results indicate that pruning is involved in behavioral extinction, while maintenance of spines is a probable mechanism that mediates the protecting effect against amnesic treatments produced by enhanced training. PMID:22438840

  10. Extinction rates in North American freshwater fishes, 1900-2010

    USGS Publications Warehouse

    Burkhead, Noel M.

    2012-01-01

    Widespread evidence shows that the modern rates of extinction in many plants and animals exceed background rates in the fossil record. In the present article, I investigate this issue with regard to North American freshwater fishes. From 1898 to 2006, 57 taxa became extinct, and three distinct populations were extirpated from the continent. Since 1989, the numbers of extinct North American fishes have increased by 25%. From the end of the nineteenth century to the present, modern extinctions varied by decade but significantly increased after 1950 (post-1950s mean = 7.5 extinct taxa per decade). The modern extinction rate for North American freshwater fishes is conservatively estimated to be 877 times greater than the background extinction rate for freshwater fishes (one extinction every 3 million years). Reasonable estimates project that future increases in extinctions will range from 53 to 86 species by 2050.

  11. Mass extinction caused by large bolide impacts

    NASA Technical Reports Server (NTRS)

    Alvarez, Luis W.

    1987-01-01

    A history and development status assessment is presented for the hypothesis that the great extinction of living species 65 million years ago, at the boundary between the Tertiary and Cretaceous geological ages, was due to the collision of a meteoroid, asteroid, or comet with the earth. The initial, deeply suggestive indication of the extraterrestial origin of the extinction-initiating mechanism was the detection of an exceptionally high concentration of iridium at the stratigraphic position of the extinction. Detailed computer modeling of the atmospheric effect of such a bolide impact has shown that the earth would have first grown intensely cold during a period of darkness due to particulate debris clouds in the upper atmosphere, followed by an enormous increase in global temperatures as the debris cleared, created by the persistence of greenhouse-effect gases; this heating would have been especially lethal to numerous forms of life.

  12. Mammal extinctions, body size, and paleotemperature

    USGS Publications Warehouse

    Bown, T.M.; Holroyd, P.A.; Rose, K.D.

    1994-01-01

    There is a general inverse relationship between the natural logarithm of tooth area (a body size indicator) of some fossil mammals and paleotemperature during approximately 2.9 million years of the early Eocene in the Bighorn Basin of northwest Wyoming. When mean temperatures became warmer, tooth areas tended to become smaller. During colder times, larger species predominated; these generally became larger or remained the same size. Paleotemperature trends also markedly affected patterns of local (and, perhaps, regional) extinction and immigration. New species appeared as immigrants during or near the hottest (smaller forms) and coldest (larger forms) intervals. Paleotemperature trend reversals commonly resulted in the ultimate extinction of both small forms (during cooling intervals) and larger forms (during warming intervals). These immigrations and extinctions mark faunal turnovers that were also modulated by sharp increases in sediment accumulation rate.

  13. Extinction during memory reconsolidation blocks recovery of fear in adolescents.

    PubMed

    Johnson, D C; Casey, B J

    2015-01-01

    Adolescence is a time of intensified emotional experiences, during which anxiety and stress-related disorders peak. The most effective behavioral therapies for treating these disorders share exposure-based techniques as a core component. Exposure-based therapies build on the principles of fear extinction learning and involve desensitizing the individual to cues that trigger anxiety. Yet, recent evidence shows an adolescent-specific diminished capacity to extinguish fear responses, suggesting that adolescents may respond less well to exposure-based therapies than other age groups. Here we demonstrate an alternative method for blocking the recall of fear memories in adolescents, building on principles of memory reconsolidation in adults. During memory reconsolidation, a memory that is recalled becomes labile during which time it can be updated. Prior research has shown that extinction training during memory reconsolidation attenuates the recovery of fear memory in human adults and in rodents. Using this method, we show attenuation of fear memory in adolescent humans. These findings have significant implications for treating one of the most vulnerable populations to anxiety and stress related disorders - adolescents - by optimizing exposure therapy based on principles of memory reconsolidation. PMID:25749583

  14. Sleep deprivation affects extinction but not acquisition memory in honeybees.

    PubMed

    Hussaini, Syed Abid; Bogusch, Lisa; Landgraf, Tim; Menzel, Randolf

    2009-11-01

    Sleep-like behavior has been studied in honeybees before, but the relationship between sleep and memory formation has not been explored. Here we describe a new approach to address the question if sleep in bees, like in other animals, improves memory consolidation. Restrained bees were observed by a web camera, and their antennal activities were used as indicators of sleep. We found that the bees sleep more during the dark phase of the day compared with the light phase. Sleep phases were characterized by two distinct patterns of antennal activities: symmetrical activity, more prominent during the dark phase; and asymmetrical activity, more common during the light phase. Sleep-deprived bees showed rebound the following day, confirming effective deprivation of sleep. After appetitive conditioning of the bees to various olfactory stimuli, we observed their sleep. Bees conditioned to odor with sugar reward showed lesser sleep compared with bees that were exposed to either reward alone or air alone. Next, we asked whether sleep deprivation affects memory consolidation. While sleep deprivation had no effect on retention scores after odor acquisition, retention for extinction learning was significantly reduced, indicating that consolidation of extinction memory but not acquisition memory was affected by sleep deprivation. PMID:19864296

  15. Extinction Mapping of Nearby Galaxies with LEGUS

    NASA Astrophysics Data System (ADS)

    Kahre, Lauren; Walterbos, Rene A. M.; Sabbi, Elena; Thilker, David A.; Ubeda, Leonardo; LEGUS Science Team

    2016-01-01

    Using 5-band (NUV (2750 A), U, B, V, I) photometry from the Legacy ExtraGalactic Ultraviolet Survey (LEGUS), we generate extinction maps for nearby (within 10 Mpc) galaxies at resolutions of a few arcseconds. Dust is commonly used as a tracer for cold dense gas, either through IR and NIR emission maps or through extinction mapping. Extinction mapping has been used to trace dust column densities in the Milky Way, the Magellanic Clouds, and M31. The maps for M31 use IR and NIR photometry of red giant branch stars, which is more difficult to obtain for more distant galaxies. Our method uses the extinctions derived for individual massive stars using the isochrone-matching method described by Kim et al. (2012). With our 5-band photometry, which extends into the UV, we are able to trace even small amounts of extinction. These maps are then compared to HI and CO maps of the same galaxies with the goal of constraining the dust-to-gas mass ratio, which we can then correlate with the gas phase metallicity from other observations. This poster will demonstrate the technique on a few galaxies, but the project will subsequently be expanded to cover the full LEGUS sample of nearly 50 galaxies. These maps can then be used to correct massive star and cluster photometry and HII region Halpha observations for the effects of extinction in order to better characterize star formation rates and massive stellar populations for other projects, such as initial mass function studies and ionization balance studies for HII regions and the diffuse ionized gas.

  16. The end-triassic mass extinction event

    NASA Technical Reports Server (NTRS)

    Hallam, A.

    1988-01-01

    The end-Triassic is the least studied of the five major episodes of mass extinction recognized in the Phanerozoic, and the Triassic-Jurassic boundary is not precisely defined in most parts of the world, with a paucity of good marine sections and an insufficiency of biostratigraphically valuable fossils. Despite these limitations it is clear that there was a significant episode of mass extinction, affecting many groups, in the Late Norian and the existing facts are consistent with it having taken place at the very end of the period. The best record globally comes from marine strata. There was an almost complete turnover of ammonites across the T-J boundary, with perhaps no more than one genus surviving. About half the bivalve genera and most of the species went extinct, as did many archaeogastropods. Many Paleozoic-dominant brachiopods also disappeared, as did the last of the conodonts. There was a major collapse and disappearance of the Alpine calcareous sponge. Among terrestrial biota, a significant extinction event involving tetrapods was recognized. With regard to possible environmental events that may be postulated to account for the extinctions, there is no evidence of any significant global change of climate at this time. The existence of the large Manicouagan crater in Quebec, dated as about late or end-Triassic, has led to the suggestion that an impact event might be implicated, but so far despite intensive search no unequivocal iridium anomaly or shocked quartz was discovered. On the other hand there is strong evidence for significant marine regression in many parts of the world. It is proposed therefore that the likeliest cause of the marine extinctions is severe reduction in habitat area caused either by regression of epicontinental seas, subsequent widespread anoxia during the succeeding transgression, or a combination of the two.

  17. Abrupt climate change and extinction events

    NASA Technical Reports Server (NTRS)

    Crowley, Thomas J.

    1988-01-01

    There is a growing body of theoretical and empirical support for the concept of instabilities in the climate system, and indications that abrupt climate change may in some cases contribute to abrupt extinctions. Theoretical indications of instabilities can be found in a broad spectrum of climate models (energy balance models, a thermohaline model of deep-water circulation, atmospheric general circulation models, and coupled ocean-atmosphere models). Abrupt transitions can be of several types and affect the environment in different ways. There is increasing evidence for abrupt climate change in the geologic record and involves both interglacial-glacial scale transitions and the longer-term evolution of climate over the last 100 million years. Records from the Cenozoic clearly show that the long-term trend is characterized by numerous abrupt steps where the system appears to be rapidly moving to a new equilibrium state. The long-term trend probably is due to changes associated with plate tectonic processes, but the abrupt steps most likely reflect instabilities in the climate system as the slowly changing boundary conditions caused the climate to reach some threshold critical point. A more detailed analysis of abrupt steps comes from high-resolution studies of glacial-interglacial fluctuations in the Pleistocene. Comparison of climate transitions with the extinction record indicates that many climate and biotic transitions coincide. The Cretaceous-Tertiary extinction is not a candidate for an extinction event due to instabilities in the climate system. It is quite possible that more detailed comparisons and analysis will indicate some flaws in the climate instability-extinction hypothesis, but at present it appears to be a viable candidate as an alternate mechanism for causing abrupt environmental changes and extinctions.

  18. The neural correlates and temporal sequence of the relationship between shock exposure, disturbed sleep and impaired consolidation of fear extinction.

    PubMed

    Spoormaker, V I; Sturm, A; Andrade, K C; Schröter, M S; Goya-Maldonado, R; Holsboer, F; Wetter, T C; Sämann, P G; Czisch, M

    2010-12-01

    Consolidation of extinction learning is a primary mechanism disrupted in posttraumatic stress disorder (PTSD), associated with hypoactivity of the ventromedial prefrontal cortex and hippocampus. A role for rapid eye movement (REM) sleep disturbances in this failure to consolidate extinction learning has been proposed. We performed functional magnetic resonance imaging (fMRI) with simultaneous skin conductance response (SCR) measurements in 16 healthy participants during conditioning/extinction and later recall of extinction. The visual stimuli were basic geometric forms and electrical shocks functioned as the unconditioned stimulus. Between the conditioning/extinction and recall sessions, participants received a 90-min sleep window in the sleep laboratory. This daytime sleep was polysomnographically recorded and scored by professionals blind to the study design. Only seven out of 16 participants had REM sleep; participants without REM sleep had a significantly slower decline of both SCR and neural activity of the laterodorsal tegmentum in response to electrical shocks during conditioning. At recall of fear extinction, participants with preceding REM sleep had a reduced SCR and stronger activation of the left ventromedial prefrontal cortex and bilateral lingual gyrus in response to the extinguished stimulus than participants lacking REM sleep. This study indicates that trait-like differences in shock reactivity/habituation (mediated by the brainstem) are predictive of REM sleep disruption, which in turn is associated with impaired consolidation of extinction (mediated by the ventromedial prefrontal cortex). These findings help understand the neurobiological basis and the temporal sequence of the relationship between shock exposure, disturbed sleep and impaired consolidation of extinction, as observed in PTSD. PMID:20471033

  19. Interactions of time of day and sleep with between-session habituation and extinction memory in young adult males

    PubMed Central

    Pace-Schott, Edward F.; Tracy, Lauren E.; Rubin, Zoe; Mollica, Adrian G.; Ellenbogen, Jeffrey M.; Bianchi, Matt T.; Milad, Mohammed R.; Pitman, Roger K.; Orr, Scott P.

    2014-01-01

    Within-session habituation and extinction learning co-occur as do subsequent consolidation of habituation (i.e., between-session habituation) and extinction memory. We sought to determine if, as we predicted: (1) between-session habituation is greater across a night of sleep vs. a day awake; (2) time-of-day accounts for differences; (3) between-session habituation predicts consolidation of extinction memory; (4) sleep predicts between-session habituation and/or extinction memory. Participants (N=28) completed 4–5 sessions alternating between mornings and evenings over 3 successive days (2 nights) with session 1 in either the morning (N=13) or evening (N=15). Twelve participants underwent laboratory polysomnography. During 4 sessions, participants completed a loud-tone habituation protocol while skin-conductance response (SCR), blink-startle electromyography (EMG), heart-rate acceleration (HRA) and deceleration (HRD) were recorded. For sessions 1 and 2, between-session habituation of EMG, SCR and HRD was greater across sleep. SCR and HRD were generally lower in the morning. Between-session habituation of SCR for sessions 1 and 2 was positively related to intervening (first night) slow wave sleep. In the evening before night 2, participants also underwent fear conditioning and extinction learning phases of a second protocol. Extinction recall was tested the following morning. Extinction recall was predicted only by between-session habituation of SCR across the same night (second night) and by intervening REM. We conclude that: 1) sleep augments between-session habituation, as does morning testing; 2) extinction recall is predicted by concurrent between-session habituation; and 3) both phenomena may be influenced by sleep. PMID:24481663

  20. Interactions of time of day and sleep with between-session habituation and extinction memory in young adult males.

    PubMed

    Pace-Schott, Edward F; Tracy, Lauren E; Rubin, Zoe; Mollica, Adrian G; Ellenbogen, Jeffrey M; Bianchi, Matt T; Milad, Mohammed R; Pitman, Roger K; Orr, Scott P

    2014-05-01

    Within-session habituation and extinction learning co-occur as do subsequent consolidation of habituation (i.e., between-session habituation) and extinction memory. We sought to determine whether, as we predicted: (1) between-session habituation is greater across a night of sleep versus a day awake; (2) time-of-day accounts for differences; (3) between-session habituation predicts consolidation of extinction memory; (4) sleep predicts between-session habituation and/or extinction memory. Participants (N = 28) completed 4-5 sessions alternating between mornings and evenings over 3 successive days (2 nights) with session 1 in either the morning (N = 13) or evening (N = 15). Twelve participants underwent laboratory polysomnography. During 4 sessions, participants completed a loud-tone habituation protocol, while skin conductance response (SCR), blink startle electromyography (EMG), heart-rate acceleration and heart-rate deceleration (HRD) were recorded. For sessions 1 and 2, between-session habituation of EMG, SCR and HRD was greater across sleep. SCR and HRD were generally lower in the morning. Between-session habituation of SCR for sessions 1 and 2 was positively related to intervening (first night) slow wave sleep. In the evening before night 2, participants also underwent fear conditioning and extinction learning phases of a second protocol. Extinction recall was tested the following morning. Extinction recall was predicted only by between-session habituation of SCR across the same night (second night) and by intervening REM. We conclude that: (1) sleep augments between-session habituation, as does morning testing; (2) extinction recall is predicted by concurrent between-session habituation; and (3) both phenomena may be influenced by sleep. PMID:24481663

  1. Cognitive Enhancers for Facilitating Drug Cue Extinction: Insights from Animal Models

    PubMed Central

    Nic Dhonnchadha, Bríd Áine; Kantak, Kathleen M.

    2011-01-01

    Given the success of cue exposure (extinction) therapy combined with a cognitive enhancer for reducing anxiety, it is anticipated that this approach will prove more efficacious than exposure therapy alone in preventing relapse in individuals with substance use disorders. Several factors may undermine the efficacy of exposure therapy for substance use disorders, but we suspect that neurocognitive impairments associated with chronic drug use are an important contributing factor. Numerous insights on these issues are gained from research using animal models of addiction. In this review, the relationship between brain sites whose learning, memory and executive functions are impaired by chronic drug use and brain sites that are important for effective drug cue extinction learning is explored first. This is followed by an overview of animal research showing improved treatment outcome for drug addiction (e.g. alcohol, amphetamine, cocaine, heroin) when explicit extinction training is conducted in combination with acute dosing of a cognitive-enhancing drug. The mechanism by which cognitive enhancers are thought to exert their benefits is by facilitating consolidation of drug cue extinction memory after activation of glutamatergic receptors. Based on the encouraging work in animals, factors that may be important for the treatment of drug addiction are considered. PMID:21295059

  2. Cognitive enhancers for facilitating drug cue extinction: insights from animal models.

    PubMed

    Nic Dhonnchadha, Bríd Áine; Kantak, Kathleen M

    2011-08-01

    Given the success of cue exposure (extinction) therapy combined with a cognitive enhancer for reducing anxiety, it is anticipated that this approach will prove more efficacious than exposure therapy alone in preventing relapse in individuals with substance use disorders. Several factors may undermine the efficacy of exposure therapy for substance use disorders, but we suspect that neurocognitive impairments associated with chronic drug use are an important contributing factor. Numerous insights on these issues are gained from research using animal models of addiction. In this review, the relationship between brain sites whose learning, memory and executive functions are impaired by chronic drug use and brain sites that are important for effective drug cue extinction learning is explored first. This is followed by an overview of animal research showing improved treatment outcome for drug addiction (e.g. alcohol, amphetamine, cocaine, heroin) when explicit extinction training is conducted in combination with acute dosing of a cognitive-enhancing drug. The mechanism by which cognitive enhancers are thought to exert their benefits is by facilitating consolidation of drug cue extinction memory after activation of glutamatergic receptors. Based on the encouraging work in animals, factors that may be important for the treatment of drug addiction are considered. PMID:21295059

  3. Savings and extinction of conditioned eyeblink responses in fragile X syndrome

    PubMed Central

    Smit, A E; van der Geest, J N; Vellema, M; Koekkoek, S K E; Willemsen, R; Govaerts, L C P; Oostra, B A; De Zeeuw, C I; VanderWerf, F

    2008-01-01

    The fragile X syndrome (FRAXA) is the most widespread heritable form of mental retardation caused by the lack of expression of the fragile X mental retardation protein (FMRP). This lack has been related to deficits in cerebellum-mediated acquisition of conditioned eyelid responses in individuals with FRAXA. In the present behavioral study, long-term effects of deficiency of FMRP were investigated by examining the acquisition, savings and extinction of delay eyeblink conditioning in male individuals with FRAXA. In the acquisition experiment, subjects with FRAXA displayed a significantly poor performance compared with controls. In the savings experiment performed at least 6 months later, subjects with FRAXA and controls showed similar levels of savings of conditioned responses. Subsequently, extinction was faster in subjects with FRAXA than in controls. These findings confirm that absence of the FMRP affects cerebellar motor learning. The normal performance in the savings experiment and aberrant performance in the acquisition and extinction experiments of individuals with FRAXA suggest that different mechanisms underlie acquisition, savings and extinction of cerebellar motor learning. PMID:18616611

  4. Context conditioning and extinction in humans: differential contribution of the hippocampus, amygdala and prefrontal cortex.

    PubMed

    Lang, Simone; Kroll, Alexander; Lipinski, Slawomira J; Wessa, Michèle; Ridder, Stephanie; Christmann, Christoph; Schad, Lothar R; Flor, Herta

    2009-02-01

    Functional magnetic resonance imaging was used to investigate the role of the hippocampus, amygdala and medial prefrontal cortex (mPFC) in a contextual conditioning and extinction paradigm provoking anxiety. Twenty-one healthy persons participated in a differential context conditioning procedure with two different background colours as contexts. During acquisition increased activity to the conditioned stimulus (CS+) relative to the CS- was found in the left hippocampus and anterior cingulate cortex (ACC). The amygdala, insula and inferior frontal cortex were differentially active during late acquisition. Extinction was accompanied by enhanced activation to CS+ vs. CS- in the dorsal anterior cingulate cortex (dACC). The results are in accordance with animal studies and provide evidence for the important role of the hippocampus in contextual learning in humans. Connectivity analyses revealed correlated activity between the left posterior hippocampus and dACC (BA32) during early acquisition and the dACC, left posterior hippocampus and right amygdala during extinction. These data are consistent with theoretical models that propose an inhibitory effect of the mPFC on the amygdala. The interaction of the mPFC with the hippocampus may reflect the context-specificity of extinction learning. PMID:19200075

  5. Context conditioning and extinction in humans: differential contribution of the hippocampus, amygdala and prefrontal cortex

    PubMed Central

    Lang, Simone; Kroll, Alexander; Lipinski, Slawomira J; Wessa, Michèle; Ridder, Stephanie; Christmann, Christoph; Schad, Lothar R; Flor, Herta

    2009-01-01

    Functional magnetic resonance imaging was used to investigate the role of the hippocampus, amygdala and medial prefrontal cortex (mPFC) in a contextual conditioning and extinction paradigm provoking anxiety. Twenty-one healthy persons participated in a differential context conditioning procedure with two different background colours as contexts. During acquisition increased activity to the conditioned stimulus (CS+) relative to the CS− was found in the left hippocampus and anterior cingulate cortex (ACC). The amygdala, insula and inferior frontal cortex were differentially active during late acquisition. Extinction was accompanied by enhanced activation to CS+ vs. CS− in the dorsal anterior cingulate cortex (dACC). The results are in accordance with animal studies and provide evidence for the important role of the hippocampus in contextual learning in humans. Connectivity analyses revealed correlated activity between the left posterior hippocampus and dACC (BA32) during early acquisition and the dACC, left posterior hippocampus and right amygdala during extinction. These data are consistent with theoretical models that propose an inhibitory effect of the mPFC on the amygdala. The interaction of the mPFC with the hippocampus may reflect the context-specificity of extinction learning. PMID:19200075

  6. Large extinction ratio optical electrowetting shutter.

    PubMed

    Montoya, Ryan D; Underwood, Kenneth; Terrab, Soraya; Watson, Alexander M; Bright, Victor M; Gopinath, Juliet T

    2016-05-01

    A large extinction ratio optical shutter has been demonstrated using electrowetting liquids. The device is based on switching between a liquid-liquid interface curvature that produces total internal reflection and one that does not. The interface radius of curvature can be tuned continuously from 9 mm at 0 V to -45 mm at 26 V. Extinction ratios from 55.8 to 66.5 dB were measured. The device shows promise for ultracold chip-scale atomic clocks. PMID:27137579

  7. Mass extinctions: Persistent problems and new directions

    NASA Technical Reports Server (NTRS)

    Jablonski, D.

    1994-01-01

    Few contest that mass extinctions have punctuated the history of life, or that those events were so pervasive environmentally, taxonomically, and geographically that physical forcing factors were probably involved. However, consensus remains elusive on the nature of those factors, and on how a given perturbation - impact, volcanism, sea-level change, or ocean anoxic event - could actually generate the observed intensity and selectivity of biotic losses. At least two basic problems underlie these long-standing disagreements: difficulties in resolving the fine details of taxon ranges and abundances immediately prior to and after an extinction boundary and the scarcity of simple, unitary cause-and-effect relations in complex biological systems.

  8. Inhibition of estradiol synthesis impairs fear extinction in male rats.

    PubMed

    Graham, Bronwyn M; Milad, Mohammed R

    2014-07-01

    Emerging research has demonstrated that the sex hormone estradiol regulates fear extinction in female rodents and women. Estradiol may also regulate fear extinction in males, given its role in synaptic plasticity in both sexes. Here we report that inhibition of estradiol synthesis during extinction training, via the aromatase inhibitor fadrozole, significantly impairs extinction recall in male rats. This deficit in extinction recall is not due to state-dependent memory formation and is completely abolished by coadministration of estradiol. Our data suggest that estradiol may be just as important in the regulation of fear extinction in males as it is in females. PMID:24939838

  9. Inhibition of estradiol synthesis impairs fear extinction in male rats

    PubMed Central

    Graham, Bronwyn M.; Milad, Mohammed R.

    2014-01-01

    Emerging research has demonstrated that the sex hormone estradiol regulates fear extinction in female rodents and women. Estradiol may also regulate fear extinction in males, given its role in synaptic plasticity in both sexes. Here we report that inhibition of estradiol synthesis during extinction training, via the aromatase inhibitor fadrozole, significantly impairs extinction recall in male rats. This deficit in extinction recall is not due to state-dependent memory formation and is completely abolished by coadministration of estradiol. Our data suggest that estradiol may be just as important in the regulation of fear extinction in males as it is in females. PMID:24939838

  10. Extinction space--a method for the quantification and classification of changes in morphospace across extinction boundaries.

    PubMed

    Korn, Dieter; Hopkins, Melanie J; Walton, Sonny A

    2013-10-01

    Three main modes of extinction are responsible for reductions in morphological disparity: (1) random (caused by a nonselective extinction event); (2) marginal (a symmetric, selective extinction event trimming the margin of morphospace); and (3) lateral (an asymmetric, selective extinction event eliminating one side of the morphospace). These three types of extinction event can be distinguished from one another by comparing changes in three measures of morphospace occupation: (1) the sum of range along the main axes; (2) the sum of variance; and (3) the position of the centroid. Computer simulations of various extinction events demonstrate that the pre-extinction distribution of taxa (random or normal) in the morphospace has little influence on the quantification of disparity changes, whereas the modes of the extinction events play the major role. Together, the three disparity metrics define an "extinction-space" in which different extinction events can be directly compared with one another. Application of this method to selected extinction events (Frasnian-Famennian, Devonian-Carboniferous, and Permian-Triassic) of the Ammonoidea demonstrate the similarity of the Devonian events (selective extinctions) but the striking difference from the end-Permian event (nonselective extinction). These events differ in their mode of extinction despite decreases in taxonomic diversity of similar magnitude. PMID:24094334

  11. The role of Deccan volcanism during the K-T mass extinction

    NASA Astrophysics Data System (ADS)

    Adatte, T.; Keller, G.; Gertsch, B.

    2012-12-01

    The potential role of major volcanic provinces has long been neglected as potential cause for major mass extinctions in Earth's history. This is despite the fact that volcanic activity is implicated in four of the five Phanerozoic mass extinctions, whereas a large asteroid impact is only associated with the K-T mass extinction. After 28 years of nearly unchallenged perception that a large impact (Chicxulub) on Yucatan caused the end-Cretaceous mass extinction, this theory is facing its most serious challenge from Deccan volcanism in India. Recent advances in Deccan volcanic studies s