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1

Transcranial magnetic stimulation: the method and application  

Microsoft Academic Search

Summary. Transcranial magnetic stimulation is a noninvasive method for stimulation of brain that is based on the ability of magnetic field to penetrate skull and brain meninges, subsequently inducing electric current in the brain tissues that produces neuronal depolarization and generation of action potentials. Moreover, transcranial magnetic stimulation has effects on neurochemical and synaptic processes in neurons. Due to its

Jacqueline Höppner; Osvaldas Rukš?nas

2006-01-01

2

Optimization of multiple coils immersed in a conducting liquid for half-hemisphere or whole-brain deep transcranial magnetic stimulation: A simulation study.  

PubMed

Transcranial magnetic stimulation (TMS) was proposed in 1985. Nevertheless, its wider use in the treatment of several neurologic diseases has been hindered by its inability to stimulate deep-brain regions. This is mainly due to the physical limiting effect arising from the presence of surface discontinuities, particularly between the scalp and air. Here, we present the optimization of a system of large multiple coils for whole-brain and half-hemisphere deep TMS, termed orthogonal configuration. COMSOL(®)-based simulations show that the system is capable of reaching the very center of a spherical brain phantom with 58% induction relative to surface maximum. Such penetration capability surpasses to the best of our knowledge that of existing state of the art TMS systems. This induction capability strongly relies on the immersion of the stimulating coils and part of the head of the patient in a conducting liquid (e.g. simple saline solution). We show the impact of the presence of this surrounding conducting liquid by comparing the performance of our system with and without such liquid. In addition, we also compare the performance of the proposed coil with that of a circular coil, a figure-eight coil, and the H-coil. Finally, in addition to its whole-brain stimulation capability (e.g. potentially useful for prophylaxis of epileptic patients) the system is also able to stimulate mainly one brain hemisphere, which may be useful in stroke rehabilitation, among other applications. PMID:25570015

Sousa, Sonia C P; Almeida, Jorge; Cavaleiro Miranda, Pedro; Salvador, Ricardo; Silvestre, Joao; Simoes, Hugo; Crespo, Paulo

2014-08-01

3

Outcomes in spasticity after repetitive transcranial magnetic and transcranial direct current stimulations  

PubMed Central

Non-invasive brain stimulations mainly consist of repetitive transcranial magnetic stimulation and transcranial direct current stimulation. Repetitive transcranial magnetic stimulation exhibits satisfactory outcomes in improving multiple sclerosis, stroke, spinal cord injury and cerebral palsy-induced spasticity. By contrast, transcranial direct current stimulation has only been studied in post-stroke spasticity. To better validate the efficacy of non-invasive brain stimulations in improving the spasticity post-stroke, more prospective cohort studies involving large sample sizes are needed. PMID:25206878

Gunduz, Aysegul; Kumru, Hatice; Pascual-Leone, Alvaro

2014-01-01

4

Myoclonus and transcranial magnetic stimulation.  

PubMed

The neural dysfunction at the origin of myoclonus may locate at various anatomical levels within the central nervous system, including the motor cortices. Transcranial magnetic stimulation (TMS) can be used to assess the balance between inhibitory and excitatory processes involved in the regulation of motor cortex activity and thereby, may be of value to determine the pathophysiological mechanisms of myoclonus. Using paired-pulse paradigms with various interstimulus intervals, TMS studies showed that intracortical inhibition (ICI) was reduced in progressive myoclonic epilepsy (PME). In contrast, ICI was decreased only for short interstimulus intervals in patients with juvenile myoclonic epilepsy (JME). Transcallosal inhibition and sensorimotor integration were also both altered in PME but not in JME. Actually, the loss of inhibitory regulation within the central nervous system might represent an intrinsic mechanism of myoclonus, whether of epileptic origin or not. Finally, the other TMS parameters of excitability (motor threshold, silent period, intracortical facilitation) were found normal in most cases of myoclonus. According to these observations, it was quite conceivable that the application of repetitive trains of TMS (rTMS) at inhibitory low-frequency (around 1 Hz) might be able to relieve myoclonus by restoring ICI. A few reported cases illustrate the efficacy of low-frequency rTMS to alleviate myoclonic symptoms. Therapeutic-like perspectives are opened for rTMS in these forms of myoclonus that are related to motor cortical hyperexcitability secondary to the loss of ICI. PMID:17336773

Lefaucheur, J-P

2006-01-01

5

Transcranial magnetic stimulation during pregnancy.  

PubMed

The aim of the present study was to assess the safety and effectiveness of high-frequency repetitive transcranial magnetic stimulation (rTMS) in pregnant patients with depression. Thirty depressed pregnant patients received rTMS over the left prefrontal cortex for 6 days in a week, from Monday to Saturday for 3 weeks. The rTMS intensity was set at 100% of the motor threshold. A 25-Hz stimulation with a duration of 2 s was delivered 20 times with 30-s intervals. A session comprised 1,000 magnetic pulses. Depression was rated using the 17-item Hamilton depression rating scale (HAMD) before and after treatment. Response was defined as a 50% reduction of the HAMD score. Patients with HAMD scores less than 8 were considered to be in remission. The mean HAMD score for the study group decreased from 26.77?±?5.58 to 13.03?±?6.93 (p?

H?zl? Sayar, Gökben; Ozten, Eylem; Tufan, Evren; Cerit, Cem; Ka?an, Gaye; Dilbaz, Nesrin; Tarhan, Nevzat

2014-08-01

6

Add-on deep transcranial magnetic stimulation (dTMS) in patients with dysthymic disorder comorbid with alcohol use disorder: A comparison with standard treatment.  

PubMed

Abstract Objectives. Dorsolateral prefrontal cortex (DLPFC) is dysfunctional in mood and substance use disorders. We predicted higher efficacy for add-on bilateral prefrontal high-frequency deep transcranial magnetic stimulation (dTMS), compared with standard drug treatment (SDT) in patients with dysthymic disorder (DD)/alcohol use disorder (AUD) comorbidity. Methods. We carried-out a 6-month open-label study involving 20 abstinent patients with DSM-IV-TR AUD comorbid with previously developed DD. Ten patients received SDT for AUD with add-on bilateral dTMS (dTMS-AO) over the DLPFC, while another 10 received SDT alone. We rated alcohol craving with the Obsessive Compulsive Drinking Scale (OCDS), depression with the Hamilton Depression Rating Scale (HDRS), clinical status with the Clinical Global Impressions scale (CGI), and global functioning with the Global Assessment of Functioning (GAF). Results. At the end of the 20-session dTMS period (or an equivalent period in the SDT group), craving scores and depressive symptoms in the dTMS-AO group dropped signi?cantly more than in the SDT group (P < 0.001 and P < 0.02, respectively). Conclusions. High frequency bilateral DLPFC dTMS with left preference was well tolerated and found to be effective as add-on in AUD. The potential of dTMS for reducing craving in substance use disorder patients deserves to be further investigated. PMID:25140585

Girardi, Paolo; Rapinesi, Chiara; Chiarotti, Flavia; Kotzalidis, Georgios D; Piacentino, Daria; Serata, Daniele; Del Casale, Antonio; Scatena, Paola; Mascioli, Flavia; Raccah, Ruggero N; Brugnoli, Roberto; Digiacomantonio, Vittorio; Ferri, Vittoria Rachele; Ferracuti, Stefano; Zangen, Abraham; Angeletti, Gloria

2015-01-01

7

Clinical Applications of Transcranial Magnetic Stimulation in Pediatric Neurology.  

PubMed

Noninvasive brain stimulation is now an accepted technique that is used as a diagnostic aid and in the treatment of neuropsychiatric disorders in adults, and is being increasingly used in children. In this review, we will discuss the basic principles and safety of one noninvasive brain stimulation method, transcranial magnetic stimulation. Improvements in the spatial accuracy of transcranial magnetic stimulation are described in the context of image-guided transcranial magnetic stimulation. The article describes and provides examples of the current clinical applications of transcranial magnetic stimulation in children as an aid in the diagnosis and treatment of neuropsychiatric disorders and discusses future potential applications. Transcranial magnetic stimulation is a noninvasive tool that is safe for use in children and adolescents for functional mapping and treatment, and for many children it aids in the preoperative evaluation and the risk-benefit decision making. PMID:25342309

Narayana, Shalini; Papanicolaou, Andrew C; McGregor, Amy; Boop, Frederick A; Wheless, James W

2014-10-23

8

Combining functional magnetic resonance imaging with transcranial electrical stimulation  

PubMed Central

Transcranial electrical stimulation (tES) is a neuromodulatory method with promising potential for basic research and as a therapeutic tool. The most explored type of tES is transcranial direct current stimulation (tDCS), but also transcranial alternating current stimulation (tACS) and transcranial random noise stimulation (tRNS) have been shown to affect cortical excitability, behavioral performance and brain activity. Although providing indirect measure of brain activity, functional magnetic resonance imaging (fMRI) can tell us more about the global effects of stimulation in the whole brain and what is more, on how it modulates functional interactions between brain regions, complementing what is known from electrophysiological methods such as measurement of motor evoked potentials. With this review, we aim to present the studies that have combined these techniques, the current approaches and discuss the results obtained so far. PMID:23935578

Saiote, Catarina; Turi, Zsolt; Paulus, Walter; Antal, Andrea

2013-01-01

9

Transcranial Magnetic Stimulation in Child Neurology: Current and Future Directions  

Microsoft Academic Search

Transcranial magnetic stimulation (TMS) is a method for focal brain stimulation based on the principle of electromagnetic induction, where small intracranial electric currents are generated by a powerful, rapidly changing extracranial magnetic field. Over the past 2 decades TMS has shown promise in the diagnosis, monitoring, and treatment of neurological and psychiatric disease in adults, but has been used on

Richard E. Frye; Alexander Rotenberg; Molliann Ousley; Alvaro Pascual-Leone

2008-01-01

10

Transcranial Magnetic Stimulation and Volitional Quadriceps Activation  

PubMed Central

Abstract Context: Quadriceps-activation deficits have been reported after meniscectomy. Transcranial magnetic stimulation (TMS) in conjunction with maximal contractions affects quadriceps activation in patients after meniscectomy. Objective: To determine the effect of single-pulsed TMS on quadriceps central activation ratio (CAR) in patients after meniscectomy. Design: Randomized controlled clinical trial. Setting: University laboratory. Patients or Other Participants: Twenty participants who had partial meniscectomy and who had a CAR less than 85% were assigned randomly to the TMS group (7 men, 4 women; age ?=? 38.1 ± 16.2 years, height ?=? 176.8 ± 11.5 cm, mass ?=? 91.8 ± 27.5 kg, postoperative time ?=? 36.7 ± 34.9 weeks) or the control group (7 men, 2 women; age ?=? 38.2 ± 17.5 years, height ?=? 176.5 ± 7.9 cm, mass ?=? 86.2 ± 15.3 kg, postoperative time ?=? 36.6 ± 37.4 weeks). Intervention(s): Participants in the experimental group received TMS over the motor cortex that was contralateral to the involved leg and performed 3 maximal quadriceps contractions with the involved leg. The control group performed 3 maximal quadriceps contractions without the TMS. Main Outcome Measure(s): Quadriceps activation was assessed using the CAR, which was measured in 70° of knee flexion at baseline and at 0, 10, 30, and 60 minutes posttest. The CAR was expressed as a percentage of full activation. Results: Differences in CAR were detected over time (F4,72 ?=? 3.025, P ?=?.02). No interaction (F4,72 ?=? 1.457, P ?=? .22) or between-groups differences (F1,18 ?=? 0.096, P ?=? .76) were found for CAR. Moderate CAR effect sizes were found at 10 (Cohen d ?=? 0.54, 95% confidence interval [CI] ?=? ?0.33, 1.37) and 60 (Cohen d ?=? 0.50, 95% CI ?=? ?0.37, 1.33) minutes in the TMS group compared with CAR at baseline. Strong effect sizes were found for CAR at 10 (Cohen d ?=? 0.82, 95% CI ?=? ?0.13, 1.7) and 60 (Cohen d ?=? 1.06, 95% CI ?=? 0.08, 1.95) minutes in the TMS group when comparing percentage change scores between groups. Conclusions: No differences in CAR were found between groups at selected points within a 60-minute time frame, yet moderate to strong effect sizes for CAR were found at 10 and 60 minutes in the TMS group, indicating increased activation after TMS. PMID:21062180

Gibbons, Christopher E.; Pietrosimone, Brian G.; Hart, Joseph M.; Saliba, Susan A.; Ingersoll, Christopher D.

2010-01-01

11

Use of Transcranial Magnetic Stimulation in Autism Spectrum Disorders  

ERIC Educational Resources Information Center

The clinical, social and financial burden of autism spectrum disorder (ASD) is staggering. We urgently need valid and reliable biomarkers for diagnosis and effective treatments targeting the often debilitating symptoms. Transcranial magnetic stimulation (TMS) is beginning to be used by a number of centers worldwide and may represent a novel…

Oberman, Lindsay M.; Rotenberg, Alexander; Pascual-Leone, Alvaro

2015-01-01

12

Non invasive brain stimulation : modeling and experimental analysis of transcranial magnetic stimulations and transcranial DC stimulation as a modality for neuropathology treatment  

E-print Network

This thesis will explore the use of Transcranial Magnetic Stimulation (TMS) and Transcranial DC Stimulation (tDCS) as modalities for neuropathology treatment by means of both experimental and modeling paradigms. The first ...

Wagner, Timothy A. (Timothy Andrew), 1974-

2006-01-01

13

Functional neuroimaging and repetitive transcranial magnetic stimulation in Parkinson's disease.  

PubMed

Functional neuroimaging provides insights into the pathogenesis of motor symptoms in Parkinson's disease (PD) and improves our understanding of both established neuromodulatory therapies such as deep brain stimulation (DBS) and potential ones such as repetitive transcranial magnetic stimulation (rTMS). Functional imaging studies can reveal the consequences of the dopaminergic lesion in PD among a widespread network of subcortical-cortical regions. Characteristic patterns of normal cortical brain activation for motor tasks are systematically altered in PD. Recent work has emphasized the task dependence of these changes and their gradual evolution over the course of the disease. Clinically relevant PD treatment with medications or DBS tends to normalize these patterns. In this context, rTMS is discussed as a potential noninvasive alternative for neuromodulation of cortical function. Although rTMS is not a current treatment, we review recent rTMS studies in PD that suggest its promise, illustrate how functional imaging can guide application of rTMS, and suggest that subcortical dopamine release could be an rTMS mechanism of action. The combination of rTMS and functional neuroimaging broadens our knowledge of functional cortical networks in PD, which can eventually provide physicians with pathophysiologic information about different PD treatment options and rationales for neuromodulatory interventions. PMID:17514152

Wu, Allan D

2007-01-01

14

Improved transcranial magnetic stimulation coil design with realistic head modeling  

NASA Astrophysics Data System (ADS)

We are investigating Transcranial magnetic stimulation (TMS) as a noninvasive technique based on electromagnetic induction which causes stimulation of the neurons in the brain. TMS can be used as a pain-free alternative to conventional electroconvulsive therapy (ECT) which is still widely implemented for treatment of major depression. Development of improved TMS coils capable of stimulating subcortical regions could also allow TMS to replace invasive deep brain stimulation (DBS) which requires surgical implantation of electrodes in the brain. Our new designs allow new applications of the technique to be established for a variety of diagnostic and therapeutic applications of psychiatric disorders and neurological diseases. Calculation of the fields generated inside the head is vital for the use of this method for treatment. In prior work we have implemented a realistic head model, incorporating inhomogeneous tissue structures and electrical conductivities, allowing the site of neuronal activation to be accurately calculated. We will show how we utilize this model in the development of novel TMS coil designs to improve the depth of penetration and localization of stimulation produced by stimulator coils.

Crowther, Lawrence; Hadimani, Ravi; Jiles, David

2013-03-01

15

Transcranial direct current stimulation and repetitive transcranial magnetic stimulation in consultation-liaison psychiatry  

PubMed Central

Patients with clinical diseases often present psychiatric conditions whose pharmacological treatment is hampered due to hazardous interactions with the clinical treatment and/or disease. This is particularly relevant for major depressive disorder, the most common psychiatric disorder in the general hospital. In this context, nonpharmacological interventions could be useful therapies; and, among those, noninvasive brain stimulation (NIBS) might be an interesting option. The main methods of NIBS are repetitive transcranial magnetic stimulation (rTMS), which was recently approved as a nonresearch treatment for some psychiatric conditions, and transcranial direct current stimulation (tDCS), a technique that is currently limited to research scenarios but has shown promising results. Therefore, our aim was to review the main medical conditions associated with high depression rates, the main obstacles for depression treatment, and whether these therapies could be a useful intervention for such conditions. We found that depression is an important and prevalent comorbidity in a variety of diseases such as epilepsy, stroke, Parkinson's disease, myocardial infarction, cancer, and in other conditions such as pregnancy and in patients without enteral access. We found that treatment of depression is often suboptimal within the above contexts and that rTMS and tDCS therapies have been insufficiently appraised. We discuss whether rTMS and tDCS could have a significant impact in treating depression that develops within a clinical context, considering its unique characteristics such as the absence of pharmacological interactions, the use of a nonenteral route, and as an augmentation therapy for antidepressants. PMID:24141608

Valiengo, L.C.L.; Benseñor, I.M.; Lotufo, P.A.; Fraguas, R.; Brunoni, A.R.

2013-01-01

16

Muscle vibration and prefrontal repetitive transcranial magnetic stimulation.  

PubMed

We previously demonstrated that prefrontal subthreshold repetitive transcranial magnetic stimulation (rTMS) may reduce motor cortex excitability. We have now examined whether muscle vibration (MV) can compensate for this depression. We enrolled 25 healthy volunteers (aged 22 to 37 years) who received 5 HZ, 10% subthreshold prefrontal rTMS for 12 s. The extensor carpi radialis muscle was vibrated with an electromagnetic mechanical stimulator with a stimulation frequency of 120 HZ and 0.5 mm amplitude. Motor evoked potentials (MEPs) from the flexor carpi radialis muscle (FCR) following single-pulse transcranial magnetic stimulation (TMS) were recorded at baseline, and after 4, 8, and 12 s. During prefrontal rTMS, MEPs of the FCR exhibited a serial depression (P = 0.001). This effect did not occur during MV. We conclude that rTMS of the prefrontal cortex may inhibit the corticospinal system. This depression may be compensated by MV, suggesting that vibration changes motor cortex excitability. The underlying mechanism might be an input from Ia sensory afferents to the motor and prefrontal cortex. PMID:11150973

Rollnik, J D; Siggelkow, S; Schubert, M; Schneider, U; Dengler, R

2001-01-01

17

Transcranial magnetic stimulation measures in attention-deficit/hyperactivity disorder.  

PubMed

Children affected by attention-deficit/hyperactivity disorder demonstrate diminished intrahemispheric inhibition (short interval cortical inhibition), as measured by transcranial magnetic stimulation. This study determined whether interhemispheric inhibition (ipsilateral silent period latency) correlates with clinical behavioral rating and motor control deficits of affected children. In 114 right-handed children (aged 8-12 years; age/sex-matched; 50 affected, 64 controls), we performed comprehensive assessments of behavior, motor skills, and cognition. Transcranial magnetic stimulation reliably elicited ipsilateral silent periods in 54 children (23 affected); all were on average older than those with unobtainable measures. Mean ipsilateral silent period latency was 5 milliseconds longer in the affected group (P = 0.007). Longer latencies correlated with more severe behavioral symptom scores (r = 0.38, P = 0.007), particularly hyperactivity (r = 0.39, P = 0.006), and with worse motor ratings on the Physical and Neurological Examination for Soft Signs (r = 0.27, P = 0.05). Longer latency also correlated with short interval cortical inhibition (r = 0.36, P = 0.008). Longer ipsilateral silent period latencies suggest interhemispheric inhibitory signaling is slower in affected children. The deficit in this inhibitory measure may underlie developmental, behavioral, and motor impairments in children with attention-deficit/hyperactivity disorder. PMID:22883282

Wu, Steve W; Gilbert, Donald L; Shahana, Nasrin; Huddleston, David A; Mostofsky, Stewart H

2012-09-01

18

[Repetitive transcranial magnetic stimulation and rehabilitation].  

PubMed

NEURO (NovEl intervention Using Repetitive TMS and intensive Occupational therapy) have been recently reported to be clinically beneficial for post-stroke patients with upper limb hemiparesis. We confirmed the safety and feasibility of the protocol in 1,008 post-stroke patients from different institutions, and identify predictors of the clinical response to the treatment. And in our randomized controlled study of NEURO and constraint-induced movement therapy, NEURO showed the superiority of NEURO relative to constraint-induced movement therapy; NEURO improved the motion of the whole upper limb and resulted. We have investigated the recovery mechanism using electrophysiological examination and functional magnetic resonance imaging. Low-frequency rTMS applied to the non-lesional hemisphere in post-stroke patients significantly decreased the F-wave frequency and amplitude in the affected upper limb, suggesting that this modality has an anti-spastic effect in post-stroke patients. Serial functional magnetic resonance imaging indicated that our proposed treatment can induce functional cortical reorganization, leading to motor functional recovery of the affected upper limb. Especially, it seems that neural activation in the lesional hemisphere plays an important role in such recovery in poststroke hemiparetic patients. PMID:24291951

Abo, Masahiro

2013-01-01

19

Transcranial Magnetic Stimulation in Child Neurology: Current and Future Directions  

PubMed Central

Transcranial magnetic stimulation (TMS) is a method for focal brain stimulation based on the principle of electromagnetic induction, where small intracranial electric currents are generated by a powerful, rapidly changing extracranial magnetic field. Over the past 2 decades TMS has shown promise in the diagnosis, monitoring, and treatment of neurological and psychiatric disease in adults, but has been used on a more limited basis in children. We reviewed the literature to identify potential diagnostic and therapeutic applications of TMS in child neurology and also its safety in pediatrics. Although TMS has not been associated with any serious side effects in children and appears to be well tolerated, general safety guidelines should be established. The potential for applications of TMS in child neurology and psychiatry is significant. Given its excellent safety profile and possible therapeutic effect, this technique should develop as an important tool in pediatric neurology over the next decade. PMID:18056688

Frye, Richard E.; Rotenberg, Alexander; Ousley, Molliann; Pascual-Leone, Alvaro

2008-01-01

20

Transcranial magnetic stimulation in child neurology: current and future directions.  

PubMed

Transcranial magnetic stimulation (TMS) is a method for focal brain stimulation based on the principle of electromagnetic induction, where small intracranial electric currents are generated by a powerful, rapidly changing extracranial magnetic field. Over the past 2 decades TMS has shown promise in the diagnosis, monitoring, and treatment of neurological and psychiatric disease in adults, but has been used on a more limited basis in children. We reviewed the literature to identify potential diagnostic and therapeutic applications of TMS in child neurology and also its safety in pediatrics. Although TMS has not been associated with any serious side effects in children and appears to be well tolerated, general safety guidelines should be established. The potential for applications of TMS in child neurology and psychiatry is significant. Given its excellent safety profile and possible therapeutic effect, this technique should develop as an important tool in pediatric neurology over the next decade. PMID:18056688

Frye, Richard E; Rotenberg, Alexander; Ousley, Molliann; Pascual-Leone, Alvaro

2008-01-01

21

Use of transcranial magnetic stimulation in autism spectrum disorders.  

PubMed

The clinical, social and financial burden of autism spectrum disorder (ASD) is staggering. We urgently need valid and reliable biomarkers for diagnosis and effective treatments targeting the often debilitating symptoms. Transcranial magnetic stimulation (TMS) is beginning to be used by a number of centers worldwide and may represent a novel technique with both diagnostic and therapeutic potential. Here we critically review the current scientific evidence for the use of TMS in ASD. Though preliminary data suggests promise, there is simply not enough evidence yet to conclusively support the clinical widespread use of TMS in ASD, neither diagnostically nor therapeutically. Carefully designed and properly controlled clinical trials are warranted to evaluate the true potential of TMS in ASD. PMID:24127165

Oberman, Lindsay M; Rotenberg, Alexander; Pascual-Leone, Alvaro

2015-02-01

22

Transcranial magnetic stimulation study in hereditary spastic paraparesis.  

PubMed

The motor-evoked potentials and the cortical excitability by transcranial magnetic stimulation (TMS) were studied in a family with chromosome 2p linked (due to mutations in spastin) and in a family with chromosome 16q linked (due to mutations in paraplegin) hereditary spastic paraparesis (HSP), in order to evaluate the utility of these techniques in identifying the subgroups of the disease. Central motor conduction time and motor treshold to TMS were abnormal in some members of both families; the intracortical inhibition was reduced only in the affected members of the family with chromosome 2p linked HSP, even though the neurological symptoms were sometimes similar and also when clinical features reflecting cortical dysfunction were absent. The motor cortex is differentially involved in the often clinically indistinguishable forms of HSP, and TMS may help in the differential diagnosis. PMID:12736541

Nardone, R; Tezzon, F

2003-01-01

23

[Usefulness of repetitive transcranial magnetic stimulation in psychiatric disorders].  

PubMed

Mental disorders represent a concern for the public health because of their prevalence in the general population. Despite progress in psychopharmacology, 20-30 % of the patients suffering of depressive disorders are responding only partially to different pharmacological and psychological therapeutic strategies. Until recently, the therapeutic alternative in refractory depression was the electroconvulsive therapy. New therapeutic approaches should be therefore explored. In October 2008 repetitive transcranial magnetic stimulation was approved as an antidepressive monotherapy by the FDA, opening the way to a routine application of this technique, which will supplement the body of our therapeutic armamentarium for mood disorders. We review this new therapeutic approach, which is rapidly developing for treating depression and schizophrenia. PMID:20395024

Szekely, D; Polosan, M; Grimaldi, I; Buis, C; Lhommée, E; Bougerol, T

2010-07-01

24

Transcranial magnetic stimulation in schizophrenia: the contribution of neuroimaging.  

PubMed

At the most basic level, the Transcranial Magnetic Stimulation(TMS) is a neuro-scientific tool that exerts its action by influencing the neo-cortical functions. However, in-spite of so many well-evidenced roles of TMS in neuropsychiatric conditions, its exact mechanism of action remains to be known. More intriguing are its therapeutic effects in Schizophrenia at the Cerebral-level. In this review, we adopt a neuro-imaging approach for this exploration. We review the present literature for the studies in Schizophrenia which have used a combination of rTMS with 1) Electroenchephalogram (EEG) 2)The functional Magnetic Resonance Imaging (fMRI) and the 3) Positron Emission Tomography (PET)/ Single-Photon Emission Computed Tomography. The TMS-EEG combination provides direct effects of TMS on the electro- magnetic field (EMF) of brain. The TMS-fMRI/PET/SPECT combinations are very effective in exploring the functional connectivity in brains of Schizophrenia patients as well as in performing rTMS guided neuro-navigation. Our review suggests that TMS combined with other neuroimaging modalities are needed for a better clarification of its neural actions. PMID:23409741

Du, Zhong-de; Wang, R; Prakash, Ravi; Chaudhury, S; Dayananda, G

2012-01-01

25

Repetitive transcranial magnetic stimulation for major depressive disorder: a review.  

PubMed

Several studies demonstrated that repetitive transcranial magnetic stimulation (rTMS) is an efficacious treatment for treatment-resistant major depressive disorder (TRD). Recent metaanalyses and more recent large multicentre studies provided evidence suggesting that rTMS is indeed a promising treatment; however, its efficacy has often been shown to be modest, compared with sham stimulation. We review these lines of evidence and discuss several reasons that may explain the modest therapeutic efficacy in most of these studies, including: most involved left-sided treatment alone to the dorsolateral prefrontal cortex (DLPFC) only, which may be less optimal than applying bilateral stimulation; suboptimal methods were used to target the DLPFC (that is, the 5-cm anterior method), limiting the treatment potential of inherently a targeted form of treatment; some treatment durations were short (that is, 2 to 4 weeks); and stimulation intensity might have been insufficient by not considering coil-to-cortex distance, which has been linked to rTMS-induced antidepressant response. Future studies attempting to address the above-mentioned limitations are necessary to potentially optimize the efficacy of this already promising treatment option in TRD. Finally, it is also essential that research investigate the mechanisms of therapeutic efficacy, thus increases in understanding can be translated into enhanced treatment. For several reasons that will be reviewed, cortical excitability may represent an important mechanism, linked to the therapeutic efficacy of this disorder. PMID:18801218

Daskalakis, Z Jeff; Levinson, Andrea J; Fitzgerald, Paul B

2008-09-01

26

Physiology of repetitive transcranial magnetic stimulation of the human brain.  

PubMed

During the last two decades, transcranial magnetic stimulation (TMS) has rapidly become a valuable method to investigate noninvasively the human brain. In addition, repetitive TMS (rTMS) is able to induce changes in brain activity that last after stimulation. Therefore, rTMS has therapeutic potential in patients with neurologic and psychiatric disorders. It is, however, unclear by which mechanism rTMS induces these lasting effects on the brain. The effects of rTMS are often described as LTD- or LTP-like, because the duration of these alterations seems to implicate changes in synaptic plasticity. In this review we therefore discuss, based on rTMS experiments and knowledge about synaptic plasticity, whether the physiologic basis of rTMS-effects relates to changes in synaptic plasticity. We present seven lines of evidence that strongly suggest a link between the aftereffects induced by rTMS and the induction of synaptic plasticity. It is, nevertheless, important to realize that at present it is impossible to demonstrate a direct link between rTMS on the one hand and synaptic plasticity on the other. Therefore, we provide suggestions for future, innovating research, aiming to investigate both the local effects of rTMS on the synapse and the effects of rTMS on other, more global levels of brain organization. Only in that way can the aftereffects of rTMS on the brain be completely understood. PMID:20633438

Hoogendam, Janna Marie; Ramakers, Geert M J; Di Lazzaro, Vincenzo

2010-04-01

27

Transcranial magnetic stimulation in the treatment of substance addiction.  

PubMed

Transcranial magnetic stimulation (TMS) is a noninvasive method of brain stimulation used to treat a variety of neuropsychiatric disorders, but is still in the early stages of study as addiction treatment. We identified 19 human studies using repetitive TMS (rTMS) to manipulate drug craving or use, which exposed a total of 316 adults to active rTMS. Nine studies involved tobacco, six alcohol, three cocaine, and one methamphetamine. The majority of studies targeted high-frequency (5-20 Hz; expected to stimulate neuronal activity) rTMS pulses to the dorsolateral prefrontal cortex. Only five studies were controlled clinical trials: two of four nicotine trials found decreased cigarette smoking; the cocaine trial found decreased cocaine use. Many aspects of optimal treatment remain unknown, including rTMS parameters, duration of treatment, relationship to cue-induced craving, and concomitant treatment. The mechanisms of rTMS potential therapeutic action in treating addictions are poorly understood, but may involve increased dopamine and glutamate function in corticomesolimbic brain circuits and modulation of neural activity in brain circuits that mediate cognitive processes relevant to addiction, such as response inhibition, selective attention, and reactivity to drug-associated cues. rTMS treatment of addiction must be considered experimental at this time, but appears to have a promising future. PMID:25069523

Gorelick, David A; Zangen, Abraham; George, Mark S

2014-10-01

28

Stimulating the Lip Motor Cortex with Transcranial Magnetic Stimulation  

PubMed Central

Transcranial magnetic stimulation (TMS) has proven to be a useful tool in investigating the role of the articulatory motor cortex in speech perception. Researchers have used single-pulse and repetitive TMS to stimulate the lip representation in the motor cortex. The excitability of the lip motor representation can be investigated by applying single TMS pulses over this cortical area and recording TMS-induced motor evoked potentials (MEPs) via electrodes attached to the lip muscles (electromyography; EMG). Larger MEPs reflect increased cortical excitability. Studies have shown that excitability increases during listening to speech as well as during viewing speech-related movements. TMS can be used also to disrupt the lip motor representation. A 15-min train of low-frequency sub-threshold repetitive stimulation has been shown to suppress motor excitability for a further 15-20 min. This TMS-induced disruption of the motor lip representation impairs subsequent performance in demanding speech perception tasks and modulates auditory-cortex responses to speech sounds. These findings are consistent with the suggestion that the motor cortex contributes to speech perception. This article describes how to localize the lip representation in the motor cortex and how to define the appropriate stimulation intensity for carrying out both single-pulse and repetitive TMS experiments. PMID:24962266

Möttönen, Riikka; Rogers, Jack; Watkins, Kate E.

2014-01-01

29

Modulating functional and dysfunctional mentalizing by transcranial magnetic stimulation  

PubMed Central

Mentalizing, the ability to attribute mental states to others and oneself, is a cognitive function with high relevance for social interactions. Recent neuroscientific research has increasingly contributed to attempts to decompose this complex social cognitive function into constituting neurocognitive building blocks. Additionally, clinical research that focuses on social cognition to find links between impaired social functioning and neurophysiological deviations has accumulated evidence that mentalizing is affected in most psychiatric disorders. Recently, both lines of research have started to employ transcranial magnetic stimulation: the first to modulate mentalizing in order to specify its neurocognitive components, the latter to treat impaired mentalizing in clinical conditions. This review integrates findings of these two different approaches to draw a more detailed picture of the neurocognitive basis of mentalizing and its deviations in psychiatric disorders. Moreover, we evaluate the effectiveness of hitherto employed stimulation techniques and protocols, paradigms and outcome measures. Based on this overview we highlight new directions for future research on the neurocognitive basis of functional and dysfunctional social cognition. PMID:25477838

Schuwerk, Tobias; Langguth, Berthold; Sommer, Monika

2014-01-01

30

Transcranial magnetic stimulation and amyotrophic lateral sclerosis: pathophysiological insights  

PubMed Central

Amyotrophic lateral sclerosis (ALS) is a rapidly progressive neurodegenerative disorder of the motor neurons in the motor cortex, brainstem and spinal cord. A combination of upper and lower motor neuron dysfunction comprises the clinical ALS phenotype. Although the ALS phenotype was first observed by Charcot over 100?years ago, the site of ALS onset and the pathophysiological mechanisms underlying the development of motor neuron degeneration remain to be elucidated. Transcranial magnetic stimulation (TMS) enables non-invasive assessment of the functional integrity of the motor cortex and its corticomotoneuronal projections. To date, TMS studies have established motor cortical and corticospinal dysfunction in ALS, with cortical hyperexcitability being an early feature in sporadic forms of ALS and preceding the clinical onset of familial ALS. Taken together, a central origin of ALS is supported by TMS studies, with an anterograde transsynaptic mechanism implicated in ALS pathogenesis. Of further relevance, TMS techniques reliably distinguish ALS from mimic disorders, despite a compatible peripheral disease burden, thereby suggesting a potential diagnostic utility of TMS in ALS. This review will focus on the mechanisms underlying the generation of TMS measures used in assessment of cortical excitability, the contribution of TMS in enhancing the understanding of ALS pathophysiology and the potential diagnostic utility of TMS techniques in ALS. PMID:23264687

Vucic, Steve; Ziemann, Ulf; Eisen, Andrew; Hallett, Mark; Kiernan, Matthew C

2013-01-01

31

Repetitive Transcranial Magnetic Stimulator with Controllable Pulse Parameters  

PubMed Central

The characteristics of transcranial magnetic stimulation (TMS) pulses influence the physiological effect of TMS. However, available TMS devices allow very limited adjustment of the pulse parameters. We describe a novel TMS device that uses a circuit topology incorporating two energy storage capacitors and two insulated-gate bipolar transistor (IGBT) modules to generate near-rectangular electric field pulses with adjustable number, polarity, duration, and amplitude of the pulse phases. This controllable pulse parameter TMS (cTMS) device can induce electric field pulses with phase widths of 10–310 ?s and positive/negative phase amplitude ratio of 1–56. Compared to conventional monophasic and biphasic TMS, cTMS reduces energy dissipation by up to 82% and 57%, and decreases coil heating by up to 33% and 41%, respectively. We demonstrate repetitive TMS trains of 3,000 pulses at frequencies up to 50 Hz with electric field pulse amplitude and width variability less than the measurement resolution (1.7% and 1%, respectively). Offering flexible pulse parameter adjustment and reduced power consumption and coil heating, cTMS enhances existing TMS paradigms, enables novel research applications, and could lead to clinical applications with potentially enhanced potency. PMID:21540487

Peterchev, Angel V; Murphy, David L; Lisanby, Sarah H

2013-01-01

32

Noninvasive techniques for probing neurocircuitry and treating illness: vagus nerve stimulation (VNS), transcranial magnetic stimulation (TMS) and transcranial direct current stimulation (tDCS)  

PubMed Central

Although the preceding chapters discuss much of the new knowledge of neurocircuitry of neuropsychiatric diseases, and an invasive approach to treatment, this chapter describes and reviews the noninvasive methods of testing circuit-based theories and treating neuropsychiatric diseases that do not involve implanting electrodes into the brain or on its surface. These techniques are transcranial magnetic stimulation, vagus nerve stimulation, and transcranial direct current stimulation. Two of these approaches have FDA approval as therapies. PMID:19693003

George, Mark S; Aston-Jones, Gary

2010-01-01

33

Topographic mapping of human motor cortex with transcranial magnetic stimulation: Homunculus revisited  

Microsoft Academic Search

Summany The purpose of this study was to non-invasively evaluate the homuncular organization of the motor cortex in man. We used transcranial magnetic stimulation to induce motor evoked potentials (MEP's) in Abductor Pollicis Brevis (APB) and Biceps Brachii (BB) muscles of 10 healthy volunteers. The practicality and accuracy of magnetic stimulation to scalp sites one cm apart was increased by

Leo Verhagen Metman; Jacqueline S. Bellevich; Seth M. Jones; Matt D. Barber; Leopold J. Streletz

1993-01-01

34

A structurally detailed finite element human head model for simulation of transcranial magnetic stimulation  

Microsoft Academic Search

Computational studies of the head utilizing finite element models (FEMs) have been used to investigate a wide variety of brain–electromagnetic (EM) field interaction phenomena including magnetic stimulation of the head using transcranial magnetic stimulation (TMS), direct electric stimulation of the brain for electroconvulsive therapy, and electroencephalography source localization. However, no human head model of sufficient complexity for studying the biophysics

Ming Chen; David Jeffery Mogul

2009-01-01

35

Repetitive transcranial magnetic stimulation for the treatment of chronic tinnitus after traumatic brain injury: a case study.  

PubMed

Tinnitus is a frequent symptom of traumatic brain injury, which is difficult to treat. Repetitive transcranial magnetic stimulation has shown beneficial effects in some forms of tinnitus. However, traumatic brain injury in the past has been considered as a relative contraindication for repetitive transcranial magnetic stimulation because of the increased risk of seizures. Here we present the case of a 53-year-old male patient suffering from severe tinnitus after traumatic brain injury with comorbid depression and alcohol abuse, who received 5 treatment series of repetitive transcranial magnetic stimulation (1 Hz stimulation protocol over left primary auditory cortex, 10 sessions of 2000 stimuli each, stimulation intensity 110% resting motor threshold). Repetitive transcranial magnetic stimulation was tolerated without any side effects and tinnitus complaints (measured by a validated tinnitus questionnaire and numeric rating scales) were improved in a replicable way throughout 5 courses of transcranial magnetic stimulation up to now. PMID:22688213

Kreuzer, Peter Michael; Landgrebe, Michael; Frank, Elmar; Langguth, Berthold

2013-01-01

36

Analysis of the effect of repeated-pulse transcranial magnetic stimulation at the Guangming point on electroencephalograms  

PubMed Central

Here, we administered repeated-pulse transcranial magnetic stimulation to healthy people at the left Guangming (GB37) and a mock point, and calculated the sample entropy of electroencephalo-gram signals using nonlinear dynamics. Additionally, we compared electroencephalogram sample entropy of signals in response to visual stimulation before, during, and after repeated-pulse tran-scranial magnetic stimulation at the Guangming. Results showed that electroencephalogram sample entropy at left (F3) and right (FP2) frontal electrodes were significantly different depending on where the magnetic stimulation was administered. Additionally, compared with the mock point, electroencephalogram sample entropy was higher after stimulating the Guangming point. When visual stimulation at Guangming was given before repeated-pulse transcranial magnetic stimula-tion, significant differences in sample entropy were found at five electrodes (C3, Cz, C4, P3, T8) in parietal cortex, the central gyrus, and the right temporal region compared with when it was given after repeated-pulse transcranial magnetic stimulation, indicating that repeated-pulse transcranial magnetic stimulation at Guangming can affect visual function. Analysis of electroencephalogram revealed that when visual stimulation preceded repeated pulse transcranial magnetic stimulation, sample entropy values were higher at the C3, C4, and P3 electrodes and lower at the Cz and T8 electrodes than visual stimulation followed preceded repeated pulse transcranial magnetic stimula-tion. The findings indicate that repeated-pulse transcranial magnetic stimulation at the Guangming evokes different patterns of electroencephalogram signals than repeated-pulse transcranial mag-netic stimulation at other nearby points on the body surface, and that repeated-pulse transcranial magnetic stimulation at the Guangming is associated with changes in the complexity of visually evoked electroencephalogram signals in parietal regions, central gyrus, and temporal regions. PMID:25206853

Zhang, Xin; Fu, Lingdi; Geng, Yuehua; Zhai, Xiang; Liu, Yanhua

2014-01-01

37

Combination rapid transcranial magnetic stimulation in treatment refractory depression  

PubMed Central

High frequency (>1 Hz) repetitive transcranial magnetic stimulation (rTMS) applied to the left prefrontal cortex and low frequency (?1 Hz) rTMS applied to the right prefrontal cortex have shown antidepressant effects. However, the clinical significance of these effects has often been modest. It was hypothesized that a combination of these two techniques might act synergistically and result in more clinically relevant antidepressant effects. Sixty-two subjects with treatment-resistant major depression (an average of 8 failed medication trials) were randomized to receive combination right low frequency (1 Hz)/left high frequency (10 Hz) rTMS over the dorsolateral prefrontal cortex at 110% of the motor threshold vs sham rTMS. Subjects were treated for 2 weeks (10 weekday sessions) and received 1600 stimulations during each treatment session. Subjects receiving combination treatment were further randomized to receive different orders of treatment: right low frequency first (Slow Right) vs left high frequency first (Fast Left). There were no statistical differences in the active vs sham treatment arms in the primary outcome variable, the Hamilton Depression Rating Scale (HDRS). However compared with subjects in the Sham and Slow Right arms, there was a trend for subjects in the Fast Left arm to show improvement in the HDRS, the Beck Depression Inventory, and the Brief Psychotic Rating Scale with increased number of treatments. The Fast Left arm also showed significant improvement in both blinded clinician and self-ratings of global improvement. These differences were hypothesized to be due to the decreased number of failed medication trials for subjects in Fast Left arm. Neuropsychological performance was not significantly different between the sham and active rTMS arms. Future studies should increase the number of treatment sessions and focus on subjects with moderate treatment resistance. PMID:19412449

McDonald, William M; Easley, Kirk; Byrd, Eve H; Holtzheimer, Paul; Tuohy, Shannon; Woodard, John L; Beyer, Kimberly; Epstein, Charles M

2006-01-01

38

ReaChR: A red-shifted variant of channelrhodopsin enables deep transcranial optogenetic excitation  

PubMed Central

Channelrhodopsins are used to optogenetically depolarize neurons. We engineered a variant of channelrhodopsin, denoted Red-activatable Channelrhodopsin (ReaChR), that is optimally excited with orange to red light (? ~ 590 to 630 nm) and offers improved membrane trafficking, higher photocurrents, and faster kinetics compared with existing red-shifted channelrhodopsins. Red light is more weakly scattered by tissue and absorbed less by blood than the blue to green wavelengths required by other channelrhodopsin variants. ReaChR expressed in vibrissa motor cortex was used to drive spiking and vibrissa motion in awake mice when excited with red light through intact skull. Precise vibrissa movements were evoked by expressing ReaChR in the facial motor nucleus in the brainstem and illuminating with red light through the external auditory canal. Thus, ReaChR enables transcranial optical activation of neurons in deep brain structures without the need to surgically thin the skull, form a transcranial window, or implant optical fibers. PMID:23995068

Lin, John Y.; Knutsen, Per Magne; Muller, Arnaud; Kleinfeld, David; Tsien, Roger Y.

2013-01-01

39

[Therapeutic application of repetitive transcranial magnetic stimulation for major depression].  

PubMed

It has been reported that approximately one third of patients with major depression are medication-resistant. In spite of partial responsiveness to antidepressants, most of the medication-resistant patients remain incompletely remitted without successful social reintegration. Symptom severity could be mild to moderate for many of them due to the incomplete remission, and, thus, electroconvulsive therapy is not applicable for them. However, they usually feel some difficulty performing cognitive behavioral therapy or social rehabilitation training due to residual symptoms such as thought inhibition and hypobulia. Under such conditions, those patients are longing for treatment options complementary to antidepressants, for less painful social reintegration. In October 2008, the Food and Drug Administration (FDA) of the United States finally approved repetitive Transcranial Magnetic Stimulation (rTMS) for medication-resistant patients with major depression. The main reason for the FDA approval was that rTMS had shown similar effectiveness (effect size around 0.39 in a recent meta-analysis) to antidepressants for medication-resistant patients without serious adverse effects. TMS is a brain stimulation methodology employing magnetic energy which can penetrate the skull bone without energy decay, and, thus, eddy currents induced by TMS can stimulate cerebral cortices effectively and locally. When TMS is repetitively delivered over several hundreds of pulses within a session, stimulation effects can be observed beyond the stimulation period as aftereffects. Moreover, when a daily rTMS session is repeated over several weeks, rTMS could have antidepressant effects. Clinical trials of rTMS for depression have employed two kinds of rTMS protocol of high-frequency (facilitatory) rTMS over the left Dorsolateral Prefrontal Cortex (DLPFC) and low-frequency (inhibitory) rTMS over the right DLPFC. Although the antidepressant action of rTMS over DLPFC has not been fully elucidated, the neuronal level hypothesis includes the induction of neuroplasticity and activation of the dopamine system, and the neuronal circuitry level hypothesis includes the activation of the left DLPFC and inhibition of the right DLPFC and (para) limbic system such as the subgenual cingulate cortex and amygdala. On the therapeutic application of rTMS in clinical psychiatry, neuroethics and low invasiveness should be fully considered along with a negative history of punitive electroconvulsive therapy and prefrontal lobotomy. It is important to investigate the neurobiological mechanism of rTMS treatment and to place rTMS in a suitable position within comprehensive treatment algorithms of major depression. PMID:23367835

Nakamura, Motoaki

2012-01-01

40

The neural response to transcranial magnetic stimulation of the human motor cortex. II. Thalamocortical contributions  

Microsoft Academic Search

Beta oscillations (15–30 Hz) constitute an important electrophysiological signal recorded in the resting state over the human precentral gyrus. The brain circuitry involved in generating the beta oscillations is not well understood but appears to involve both cortical and subcortical structures. We have shown that single pulses of transcranial magnetic stimulation (TMS) applied over the primary motor cortex consistently elicit a

Ysbrand D. Van Der Werf; Abbas F. Sadikot; Antonio P. Strafella; Tomáš Paus

2006-01-01

41

Comparison of current distributions in electroconvulsive therapy and transcranial magnetic stimulation  

Microsoft Academic Search

We compared current density distributions in electroconvulsive therapy (ECT) and transcranial magnetic stimulation (TMS) by numerical calculations. The model consisted of an air region and three types of tissues with different conductivities representing the brain, the skull, and the scalp. In the ECT model, electric currents were applied through electrodes with a voltage of 100 V. In the TMS model,

Masaki Sekino; Shoogo Ueno

2002-01-01

42

Inter-hemispheric asymmetry of motor corticospinal excitability in major depression studied by transcranial magnetic stimulation  

Microsoft Academic Search

BackgroundImaging and electroencephalographic studies have reported inter-hemispheric asymmetries in frontal cortical regions associated with depression. This study aimed at comparing motor corticospinal excitability assessed by methods of transcranial magnetic stimulation (TMS) between the right and left hemispheres in patients with major depression and healthy controls.

J. P. Lefaucheur; B. Lucas; F. Andraud; J. Y. Hogrel; F. Bellivier; A. Del Cul; A. Rousseva; M. Leboyer; M. L. Paillère-Martinot

2008-01-01

43

Transcranial magnetic stimulation of posterior parietal cortex affects decisions of hand choice  

E-print Network

Transcranial magnetic stimulation of posterior parietal cortex affects decisions of hand choice, Pasadena, CA, and approved August 26, 2010 (received for review May 10, 2010) Deciding which hand to use task, we provide evidence that hand choice entails a com- petitive decision process between

Ivry, Rich

44

Repetitive Transcranial Magnetic Stimulation to the Primary Motor Cortex Interferes with Motor Learning by Observing  

ERIC Educational Resources Information Center

Neural representations of novel motor skills can be acquired through visual observation. We used repetitive transcranial magnetic stimulation (rTMS) to test the idea that this "motor learning by observing" is based on engagement of neural processes for learning in the primary motor cortex (M1). Human subjects who observed another person learning…

Brown, Liana E.; Wilson, Elizabeth T.; Gribble, Paul L.

2009-01-01

45

Transcranial magnetic stimulation in the visual system. II. Characterization of induced phosphenes and scotomas  

Microsoft Academic Search

Transcranial magnetic stimulation (TMS) induces phosphenes and disrupts visual perception when applied over the occipital pole. Both the underlying mechanisms and the brain structures involved are still unclear. In the first part of this study we show that the masking effect of TMS differs to masking by light in terms of the psychometric function. Here we investigate the emergence of

Thomas Kammer; Klaas Puls; Michael Erb; Wolfgang Grodd

2005-01-01

46

Pressure Pain Thresholds Increase after Preconditioning 1 Hz Repetitive Transcranial Magnetic Stimulation with Transcranial Direct Current Stimulation  

PubMed Central

Background The primary motor cortex (M1) is an effective target of non-invasive cortical stimulation (NICS) for pain threshold modulation. It has been suggested that the initial level of cortical excitability of M1 plays a key role in the plastic effects of NICS. Objective Here we investigate whether transcranial direct current stimulation (tDCS) primed 1 Hz repetitive transcranial magnetic stimulation (rTMS) modulates experimental pressure pain thresholds and if this is related to observed alterations in cortical excitability. Method 15 healthy, male participants received 10 min 1 mA anodal, cathodal and sham tDCS to the left M1 before 15 min 1 Hz rTMS in separate sessions over a period of 3 weeks. Motor cortical excitability was recorded at baseline, post-tDCS priming and post-rTMS through recording motor evoked potentials (MEPs) from right FDI muscle. Pressure pain thresholds were determined by quantitative sensory testing (QST) through a computerized algometer, on the palmar thenar of the right hand pre- and post-stimulation. Results Cathodal tDCS-primed 1 Hz-rTMS was found to reverse the expected suppressive effect of 1 Hz rTMS on cortical excitability; leading to an overall increase in activity (p<0.001) with a parallel increase in pressure pain thresholds (p<0.01). In contrast, anodal tDCS-primed 1 Hz-rTMS resulted in a corresponding decrease in cortical excitability (p<0.05), with no significant effect on pressure pain. Conclusion This study demonstrates that priming the M1 before stimulation of 1 Hz-rTMS modulates experimental pressure pain thresholds in a safe and controlled manner, producing a form of analgesia. PMID:24658333

Moloney, Tonya M.; Witney, Alice G.

2014-01-01

47

Motor cortex-induced plasticity by noninvasive brain stimulation: a comparison between transcranial direct current stimulation and transcranial magnetic stimulation.  

PubMed

The aim of this study was to test and compare the effects of a within-subject design of repetitive transcranial magnetic stimulation (rTMS) [coupled with sham transcranial direct current stimulation (tDCS)] and tDCS (coupled with sham rTMS) on the motor cortex excitability and also compare the results against sham tDCS/sham rTMS. We conducted a double-blinded, randomized, sham-controlled, cross-over trial. Eleven right-handed, healthy individuals (five women, mean age: 39.8 years, SD 13.4) received the three interventions (cross-over design) in a randomized order: (a) high-frequency (HF) rTMS (+sham tDCS), (b) anodal tDCS (+sham rTMS), and (c) sham stimulation (sham rTMS+sham tDCS). Cortical excitability measurements [motor threshold, motor evoked potential (MEP), intracortical facilitation and inhibition, and transcallosal inhibition] and motor behavioral assessments were used as outcome measures. Between-group analysis of variance showed that MEP amplitude after HF rTMS was significantly higher than MEP amplitude after anodal tDCS (P=0.001). Post-hoc analysis showed a significant increase in MEP amplitude after HF rTMS (25.3%, P=0.036) and a significant decrease in MEP amplitude after anodal tDCS (-32.7%, P=0.001). There was a similar increase in motor function as indexed by Jebsen-Taylor Hand Function Test in the two active groups compared with sham stimulation. In conclusion, here, we showed that although both techniques induced similar motor gains, they induce opposing results in cortical excitability. HF rTMS is associated with an increase in corticospinal excitability, whereas 20 min of tDCS induces the opposite effect. We discuss potential implications of these results to future clinical experiments using rTMS or tDCS for motor function enhancement. PMID:24100412

Simis, Marcel; Adeyemo, Bamidele O; Medeiros, Liciane F; Miraval, Forella; Gagliardi, Rubens J; Fregni, Felipe

2013-12-01

48

Short-latency subliminal effects of transcranial magnetic stimulation on forearm motoneurones  

Microsoft Academic Search

The H-reflex technique has been used to evaluate the time-course of the effects evoked by transcranial clockwise magnetic stimuli in flexor or extensor carpi radialis motoneurones. In six subjects, magnetic stimulation was applied over the scalp in the focus for the motor response of those muscles. At intensities below motor threshold, a facilitation of the H-reflex started at a conditioning-test

F. Baldissera; P. Cavallari

1993-01-01

49

Diagnostic relevance of transcranial magnetic and electric stimulation of the facial nerve in the management of facial palsy  

Microsoft Academic Search

ObjectiveEarlier investigations have suggested that isolated conduction block of the facial nerve to transcranial magnetic stimulation early in the disorder represents a very sensitive and potentially specific finding in Bell's palsy differentiating the disease from other etiologies.

Dennis A. Nowak; Stefan Linder; Helge Topka

2005-01-01

50

Repetitive transcranial magnetic stimulation versus electroconvulsive therapy for major depression: preliminary results of a randomized trial  

Microsoft Academic Search

Background: Many severely depressed patients do not benefit from or tolerate existing treatments. Repetitive transcranial magnetic stimulation (rTMS) has been reported to benefit depression. We compared rTMS to electroconvulsive therapy (ECT) in severely ill, depressed patients.Methods: Twenty-five patients with a major depression (unipolar or bipolar) deemed clinically appropriate for ECT were randomly assigned to rTMS (10–20 treatments, 10 Hz, 110%

Philip G. Janicak; Sheila M. Dowd; Brian Martis; Danesh Alam; Dennis Beedle; Jack Krasuski; Mary Jane Strong; Rajiv Sharma; Cherise Rosen; Marlos Viana

2002-01-01

51

Transcranial magnetic stimulation: studying the brain-behaviour relationship by induction of 'virtual lesions'.  

PubMed Central

Transcranial magnetic stimulation (TMS) provides a non-invasive method of induction of a focal current in the brain and transient modulation of the function of the targeted cortex. Despite limited understanding about focality and mechanisms of action, TMS provides a unique opportunity of studying brain-behaviour relations in normal humans. TMS can enhance the results of other neuroimaging techniques by establishing the causal link between brain activity and task performance, and by exploring functional brain connectivity. PMID:10466148

Pascual-Leone, A; Bartres-Faz, D; Keenan, J P

1999-01-01

52

Therapeutic effect and mechanism of repetitive transcranial magnetic stimulation in Parkinson's disease  

Microsoft Academic Search

The therapeutic effect of repetitive transcranial magnetic stimulation (rTMS) on clinical performance was assessed by a double-blind study in 9 patients with Parkinson's disease (PD). Nine other patients underwent sham stimulation as controls. The modified Hoehn and Yahr (H&Y) staging scale, the Schwab and England Activities of Daily Living (ADL) scale, and the Unified Parkinson's disease rating scale (UPDRS) were

Hotetsu Shimamoto; Katsuyuki Takasaki; Minoru Shigemori; Toshihiro Imaizumi; Mitsuyoshi Ayabe; Hiroshi Shoji

2001-01-01

53

Perioperative lesions of the facial nerve: follow-up investigations using transcranial magnetic stimulation  

Microsoft Academic Search

Peripheral facial palsy can occur after aural surgery and neurosurgery. Routine neurophysiological investigation (utilizing\\u000a electrical stimulation and the blink reflex) does not allow the direct assessment of the site of a lesion. In the present\\u000a study transcranial magnetic stimulation (TMS) was applied in order to evaluate the usefulness of this method for prognosis.\\u000a Twenty-three patients with postoperative facial pareses (after

S. Kotterba; M. Tegenthoff; J.-P. Malin

1997-01-01

54

Low-Frequency Repetitive Transcranial Magnetic Stimulation for the Treatment of Refractory Partial Epilepsy  

Microsoft Academic Search

Seventeen refractory partial epilepsy patients were enrolled in an open-label study to evaluate the antiepileptic effect of low-frequency repetitive transcranial magnetic stimulation (rTMS). Seven of the patients had not obtained seizure-free status after epileptogenic focus resection surgery before they were enrolled in the study. All patients were treated with low-frequency rTMS which included 3 sessions per day (0.5 Hz, 90%

Wei Sun; Wei Fu; Wei Mao; Dequan Wang; Yuping Wang

2011-01-01

55

Fundamentals of Transcranial Electric and Magnetic Stimulation Dose: Definition, Selection, and Reporting Practices  

PubMed Central

The growing use of transcranial electric and magnetic (EM) brain stimulation in basic research and in clinical applications necessitates a clear understanding of what constitutes the dose of EM stimulation and how it should be reported. The biological effects of EM stimulation are mediated through an electromagnetic field injected (via electric stimulation) or induced (via magnetic stimulation) in the body. Therefore, transcranial EM stimulation dose ought to be defined by all parameters of the stimulation device that affect the electromagnetic field generated in the body, including the stimulation electrode or coil configuration parameters: shape, size, position, and electrical properties, as well as the electrode or coil current (or voltage) waveform parameters: pulse shape, amplitude, width, polarity, and repetition frequency; duration of and interval between bursts or trains of pulses; total number of pulses; and interval between stimulation sessions and total number of sessions. Knowledge of the electromagnetic field generated in the body may not be sufficient but is necessary to understand the biological effects of EM stimulation. We believe that reporting of EM stimulation dose should be guided by the principle of reproducibility: sufficient information about the stimulation parameters should be provided so that the dose can be replicated. This paper provides fundamental definition and principles for reporting of dose that encompass any transcranial EM brain stimulation protocol. PMID:22305345

Peterchev, Angel V.; Wagner, Timothy A.; Miranda, Pedro C.; Nitsche, Michael A.; Paulus, Walter; Lisanby, Sarah H.; Pascual-Leone, Alvaro; Bikson, Marom

2011-01-01

56

Non-invasive Transcranial Magnetic Stimulation (TMS) of the Motor Cortex for Neuropathic Pain—At the Tipping Point?  

PubMed Central

The term “neuropathic pain” (NP) refers to chronic pain caused by illnesses or injuries that damage peripheral or central pain-sensing neural pathways to cause them to fire inappropriately and signal pain without cause. Neuropathic pain is common, complicating diabetes, shingles, HIV, and cancer. Medications are often ineffective or cause various adverse effects, so better approaches are needed. Half a century ago, electrical stimulation of specific brain regions (neuromodulation) was demonstrated to relieve refractory NP without distant effects, but the need for surgical electrode implantation limited use of deep brain stimulation. Next, electrodes applied to the dura outside the brain’s surface to stimulate the motor cortex were shown to relieve NP less invasively. Now, electromagnetic induction permits cortical neurons to be stimulated entirely non-invasively using transcranial magnetic stimulation (TMS). Repeated sessions of many TMS pulses (rTMS) can trigger neuronal plasticity to produce long-lasting therapeutic benefit. Repeated TMS already has US and European regulatory approval for treating refractory depression, and multiple small studies report efficacy for neuropathic pain. Recent improvements include “frameless stereotactic” neuronavigation systems, in which patients’ head MRIs allow TMS to be applied to precise underlying cortical targets, minimizing variability between sessions and patients, which may enhance efficacy. Transcranial magnetic stimulation appears poised for the larger trials necessary for regulatory approval of a NP indication. Since few clinicians are familiar with TMS, we review its theoretical basis and historical development, summarize the neuropathic pain trial results, and identify issues to resolve before large-scale clinical trials. PMID:24228166

Treister, Roi; Lang, Magdalena; Klein, Max M.; Oaklander, Anne Louise

2013-01-01

57

Co-registration of magnetic resonance spectroscopy and transcranial magnetic stimulation.  

PubMed

Transcranial magnetic stimulation (TMS) is a widely used tool for noninvasive modulation of brain activity, that is thought to interact primarily with excitatory and inhibitory neurotransmitter systems. Neurotransmitters such as glutamate and GABA can be measured by magnetic resonance spectroscopy (MRS). An important prerequisite for studying the relationship between MRS neurotransmitter levels and responses to TMS is that both modalities should examine the same regions of brain tissue. However, co-registration of TMS and MRS has been little studied to date. This study reports on a procedure for the co-registration and co-visualization of MRS and TMS, successfully localizing the hand motor cortex, as subsequently determined by its functional identification using TMS. Sixteen healthy subjects took part in the study; in 14 of 16 subjects, the TMS determined location of motor activity intersected the (2.5cm)(3) voxel selected for MRS, centered on the so called 'hand knob' of the precentral gyrus. It is concluded that MRS voxels placed according to established anatomical landmarks in most cases agree well with functional determination of the motor cortex by TMS. Reasons for discrepancies are discussed. PMID:25561395

Hone-Blanchet, Antoine; Salas, Rachel E; Celnik, Pablo; Kalloo, Aadi; Schar, Michael; Puts, Nicolaas A J; Harris, Ashley D; Barker, Peter B; Fecteau, Shirley; Earley, Christopher J; Allen, Richard P; Edden, Richard A

2015-03-15

58

Effects of Repetitive Transcranial Magnetic Stimulation in Performing Eye-Hand Integration Tasks: Four Preliminary Studies with Children Showing Low-Functioning Autism  

ERIC Educational Resources Information Center

This report, based on four studies with children with low-functioning autism, aimed at evaluating the effects of repetitive transcranial magnetic stimulation delivered on the left and right premotor cortices on eye-hand integration tasks; defining the long-lasting effects of high-frequency repetitive transcranial magnetic stimulation; and…

Panerai, Simonetta; Tasca, Domenica; Lanuzza, Bartolo; Trubia, Grazia; Ferri, Raffaele; Musso, Sabrina; Alagona, Giovanna; Di Guardo, Giuseppe; Barone, Concetta; Gaglione, Maria P.; Elia, Maurizio

2014-01-01

59

Electromagnetic Field Modeling of Transcranial Electric and Magnetic Stimulation: Targeting, Individualization, and Safety of Convulsive and Subconvulsive Applications  

NASA Astrophysics Data System (ADS)

The proliferation of noninvasive transcranial electric and magnetic brain stimulation techniques and applications in recent years has led to important insights into brain function and pathophysiology of brain-based disorders. Transcranial electric and magnetic stimulation encompasses a wide spectrum of methods that have developed into therapeutic interventions for a variety of neurological and psychiatric disorders. Although these methods are at different stages of development, the physical principle underlying these techniques is the similar. Namely, an electromagnetic field is induced in the brain either via current injection through scalp electrodes or via electromagnetic induction. The induced electric field modulates the neuronal transmembrane potentials and, thereby, neuronal excitability or activity. Therefore, knowledge of the induced electric field distribution is key in the design and interpretation of basic research and clinical studies. This work aims to delineate the fundamental physical limitations, tradeoffs, and technological feasibility constraints associated with transcranial electric and magnetic stimulation, in order to inform the development of technologies that deliver safer, and more spatially, temporally, and patient specific stimulation. Part I of this dissertation expounds on the issue of spatial targeting of the electric field. Contrasting electroconvulsive therapy (ECT) and magnetic seizure therapy (MST) configurations that differ markedly in efficacy, side effects, and seizure induction efficiency could advance our understanding of the principles linking treatment parameters and therapeutic outcome and could provide a means of testing hypotheses of the mechanisms of therapeutic action. Using the finite element method, we systematically compare the electric field characteristics of existing forms of ECT and MST. We introduce a method of incorporating a modality-specific neural activation threshold in the electric field models that can inform dosage requirements in convulsive therapies. Our results indicate that the MST electric field is more focal and more confined to the superficial cortex compared to ECT. Further, the conventional ECT current amplitude is much higher than necessary for seizure induction. One of the factors important to clinical outcome is seizure expression. However, it is unknown how the induced electric field is related to seizure onset and propagation. In this work, we explore the effect of the electric field distribution on the quantitative ictal electroencephalography and current source density in ECT and MST. We further demonstrate how the ECT electrode shape, size, spacing, and current can be manipulated to yield more precise control of the induced electric field. If desirable, ECT can be made as focal as MST while using simpler stimulation equipment. Next, we demonstrate how the electric field induced by transcranial magnetic stimulation (TMS) can be controlled. We present the most comprehensive comparison of TMS coil electric field penetration and focality to date. The electric field distributions of more than 50 TMS coils were simulated. We show that TMS coils differ markedly in their electric field characteristics, but they all are subject to a consistent depth-focality tradeoff. Specifically, the ability to directly stimulate deeper brain structures is obtained at the expense of inducing wider electric field spread. Figure-8 type coils are fundamentally more focal compared to circular type coils. Understanding the depth-focality tradeoff can help researchers and clinicians to appropriately select coils and interpret TMS studies. This work also enables the development of novel TMS coils with electronically switchable active and sham modes as well as for deep TMS. Design considerations of these coils are extensively discussed. Part II of the dissertation aims to quantify the effect of individual, sex, and age differences in head geometry and conductivity on the induced neural stimulation strength and focality of ECT and MST. Across and within ECT studies, there is

Deng, Zhi-De

60

Effect of repetitive transcranial magnetic stimulation on rectal function and emotion in humans  

Microsoft Academic Search

Background  A previous brain imaging study demonstrated activation of the right dorsolateral prefrontal cortex (DLPFC) during visceral\\u000a nociception, and this activation was associated with anxiety. We hypothesized that functional modulation of the right DLPFC\\u000a by repetitive transcranial magnetic stimulation (rTMS) can reveal the actual role of right DLPFC in brain–gut interactions\\u000a in humans.\\u000a \\u000a \\u000a \\u000a \\u000a Methods  Subjects were 11 healthy males aged 23.5 ± 1.4 (mean ± SE)

Yuuichi AizawaJoe; Joe Morishita; Michiko Kano; Takayuki Mori; Shin-Ichi Izumi; Kenichiro Tsutsui; Toshio Iijima; Motoyori Kanazawa; Shin Fukudo

61

Two phases of intracortical inhibition revealed by transcranial magnetic threshold tracking  

Microsoft Academic Search

Intracortical inhibition was investigated in normal human volunteers by paired-pulse transcranial magnetic stimulation, using\\u000a a new, computer-assisted threshold-tracking method. Motor threshold was defined as the stimulus amplitude required to evoke\\u000a a motor evoked potential of 0.2 mV (peak-to-peak) in abductor pollicis brevis, and inhibition was measured as the percentage\\u000a increase in threshold, when the test stimulus was preceded by a subthreshold

R. J. Fisher; Y. Nakamura; S. Bestmann; J. C. Rothwell; H. Bostock

2002-01-01

62

Transcranial Magnetic Stimulation for the treatment of tinnitus: Effects on cortical excitability  

PubMed Central

Background Low frequency repetitive transcranial magnetic stimulation (rTMS) has been proposed as an innovative treatment for chronic tinnitus. The aim of the present study was to elucidate the underlying mechanism and to evaluate the relationship between clinical outcome and changes in cortical excitability. We investigated ten patients with chronic tinnitus who participated in a sham-controlled crossover treatment trial. Magnetic-resonance-imaging and positron-emission-tomography guided 1 Hz rTMS were performed over the auditory cortex on 5 consecutive days. Active and sham treatments were separated by one week. Parameters of cortical excitability (motor thresholds, intracortical inhibition, intracortical facilitation, cortical silent period) were measured serially before and after rTMS treatment by using single- and paired-pulse transcranial magnetic stimulation. Clinical improvement was assessed with a standardized tinnitus-questionnaire. Results We noted a significant interaction between treatment response and changes in motor cortex excitability during active rTMS. Specifically, clinical improvement was associated with an increase in intracortical inhibition, intracortical facilitation and a prolongation of the cortical silent period. These results indicate that intraindividual changes in cortical excitability may serve as a correlate of response to rTMS treatment. Conclusion The observed alterations of cortical excitability suggest that low frequency rTMS may evoke long-term-depression like effects resulting in an improvement of subcortical inhibitory function. PMID:17605764

Langguth, Berthold; Kleinjung, Tobias; Marienhagen, Joerg; Binder, Harald; Sand, Philipp G; Hajak, Göran; Eichhammer, Peter

2007-01-01

63

Eccentric figure-eight coils for transcranial magnetic stimulation.  

PubMed

Previously we proposed an eccentric figure-eight coil that can cause threshold stimulation in the brain at lower driving currents. In this study, we performed numerical simulations and magnetic stimulations to healthy subjects for evaluating the advantages of the eccentric coil. The simulations were performed using a simplified spherical brain model and a realistic human brain model. We found that the eccentric coil required a driving current intensity of approximately 18% less than that required by the concentric coil to cause comparable eddy current densities within the brain. The eddy current localization of the eccentric coil was slightly higher than that of the concentric coil. A prototype eccentric coil was designed and fabricated. Instead of winding a wire around a bobbin, we cut eccentric-spiral slits on the insulator cases, and a wire was woven through the slits. The coils were used to deliver magnetic stimulation to healthy subjects; among our results, we found that the current slew rate corresponding to motor threshold values for the concentric and eccentric coils were 86 and 78?A/µs, respectively. The results indicate that the eccentric coil consistently requires a lower driving current to reach the motor threshold than the concentric coil. Future development of compact magnetic stimulators will enable the treatment of some intractable neurological diseases at home. Bioelectromagnetics. 35:55-65, 2015. © 2014 Wiley Periodicals, Inc. PMID:25399864

Sekino, Masaki; Ohsaki, Hiroyuki; Takiyama, Yoshihiro; Yamamoto, Keita; Matsuzaki, Taiga; Yasumuro, Yoshihiro; Nishikawa, Atsushi; Maruo, Tomoyuki; Hosomi, Koichi; Saitoh, Youichi

2015-01-01

64

Transcranial magnetic stimulation as an antidepressant alternative in a patient with brugada syndrome and recurrent syncope.  

PubMed

Brugada syndrome (BrS) is a common occult cause of sudden cardiac arrest in otherwise healthy-appearing adults. The pathognomonic electrocardiographic pattern may be unmasked only by certain medications, many of which are unknown. We report a case of a depressed but otherwise healthy man with an asymptomatic right bundle branch block on electrocardiography who experienced antidepressant-induced BrS and ultimately recovered with transcranial magnetic stimulation (TMS). After an initial trial of nortriptyline, the patient's depressive symptoms improved; however, he experienced a syncopal event and was subsequently diagnosed as having BrS. Cross titration to bupropion, which had not previously been known to exacerbate BrS, was followed by another cardiac event. As a result, the patient was referred for TMS as a substitute for pharmacotherapy. After 31 TMS sessions over 8 weeks, the patient demonstrated significant improvement by subjective report and objective reduction in his Patient Health Questionnaire-9 scores from 10 (moderate) to 1 (minimal). Transcranial magnetic stimulation is a Food and Drug Administration-approved nonpharmacologic treatment for depression. Given the potential lethality of BrS with known and unknown psychopharmacologic agents, providers should consider TMS as first-line therapy in this patient population. Bupropion should be added to the list of agents known to exacerbate this disease. PMID:25444490

Alampay, Miguel M; Haigney, Mark C; Flanagan, Michael C; Perito, Robert M; Love, Kathleen M; Grammer, Geoffrey G

2014-11-01

65

Noninvasive brain stimulation with transcranial magnetic or direct current stimulation (TMS\\/tDCS)—From insights into human memory to therapy of its dysfunction  

Microsoft Academic Search

Noninvasive stimulation of the brain by means of transcranial magnetic stimulation (TMS) or transcranial direct current stimulation (tDCS) has driven important discoveries in the field of human memory functions. Stand-alone or in combination with other brain mapping techniques noninvasive brain stimulation can assess issues such as location and timing of brain activity, connectivity and plasticity of neural circuits and functional

Roland Sparing; Felix M. Mottaghy

2008-01-01

66

BRAIN initiative: Transcranial magnetic stimulation automation and calibration.  

PubMed

In this paper, we introduced an automated TMS system with robot control and optical sensor combined with neuronavigation software. By using the robot, the TMS coil can be accurately positioned over any preselected brain region. The neuronavigation system provides an accurate positioning of a magnetic coil in order to induce a specific cortical excitation. An infrared optical measurement device is also used in order to detect and compensate for head movements of the patient. This procedure was simulated using a PC based robotic simulation program. The proposed automated robot system is integrated with TMS numerical solver and allows users to actually see the depth, location, and shape of the induced eddy current on the computer monitor. PMID:25570006

Todd, Garth D; Abdellatif, Ahmed; Sabouni, Abas

2014-08-01

67

FEM-based determination of optimum current distribution in transcranial magnetic stimulation as an alternative to electroconvulsive therapy  

Microsoft Academic Search

In this study, we investigated dependences of the current distribution in transcranial magnetic stimulation (TMS) on coil current intensity, coil diameter, and coil position, and compared the current distribution with that of electroconvulsive therapy (ECT). The head model consisted of 4-mm finite elements. In the ECT model, a voltage of 100 V was applied between a pair of electrodes place

Masaki Sekino; Shoogo Ueno

2004-01-01

68

Introducing Transcranial Magnetic Stimulation (TMS) and its Property of Causal Inference in Investigating Brain-Function Relationships  

Microsoft Academic Search

Transcranial magnetic stimulation (TMS) is a method capable of transiently modulating neural excitability. Depending on the stimulation parameters information processing in the brain can be either enhanced or disrupted. This way the contribution of different brain areas involved in mental processes can be studied, allowing a functional decomposition of cognitive behavior both in the temporal and spatial domain, hence providing

Dennis J. L. G. Schutter; Jack Van Honk; Jaak Panksepp

2004-01-01

69

Involvement of the Superior Temporal Cortex and the Occipital Cortex in Spatial Hearing: Evidence from Repetitive Transcranial Magnetic Stimulation  

Microsoft Academic Search

The processing of auditory spatial information in cortical areas of the human brain outside of the primary auditory cortex remains poorly understood. Here we investigated the role of the superior temporal gyrus (STG) and the occipital cortex (OC) in spatial hearing using repetitive transcranial magnetic stimulation (rTMS). The right STG is known to be of crucial importance for visual spatial

Jörg Lewald; Ingo G. Meister; Jürgen Weidemann; Rudolf Töpper

2004-01-01

70

Animal models of the mechanisms of action of repetitive transcranial magnetic stimulation (RTMS): Comparisons with electroconvulsive shock (ECS)  

Microsoft Academic Search

2 Repetitive transcranial magnetic stimulation (rTMS) is a noninvasive means of brain stimulation with a broad range of basic neuroscience and potential future clinical applications. Recent animal studies have shed some light on the mecha- nisms of action of rTMS, and broadened our understanding of how this inter- vention affects brain functioning acutely and chronically. Differences in the physical properties

Sarah H. Lisanby; Robert H. Belmaker

2000-01-01

71

FDTD-based Transcranial Magnetic Stimulation model applied to specific neurodegenerative disorders.  

PubMed

Non-invasive treatment of neurodegenerative diseases is particularly challenging in Western countries, where the population age is increasing. In this work, magnetic propagation in human head is modelled by Finite-Difference Time-Domain (FDTD) method, taking into account specific characteristics of Transcranial Magnetic Stimulation (TMS) in neurodegenerative diseases. It uses a realistic high-resolution three-dimensional human head mesh. The numerical method is applied to the analysis of magnetic radiation distribution in the brain using two realistic magnetic source models: a circular coil and a figure-8 coil commonly employed in TMS. The complete model was applied to the study of magnetic stimulation in Alzheimer and Parkinson Diseases (AD, PD). The results show the electrical field distribution when magnetic stimulation is supplied to those brain areas of specific interest for each particular disease. Thereby the current approach entails a high potential for the establishment of the current underdeveloped TMS dosimetry in its emerging application to AD and PD. PMID:25453382

Fanjul-Vélez, Félix; Salas-García, Irene; Ortega-Quijano, Noé; Arce-Diego, José Luis

2015-01-01

72

Remediation of Sleep-Deprivation-Induced Working Memory Impairment with fMRI-Guided Transcranial Magnetic Stimulation  

Microsoft Academic Search

Repetitive transcranial magnetic stimulation (rTMS) was applied to test the role of selected cortical regions in remediating sleep- deprivation--induced deficits in visual working memory (WM) performance. Three rTMS targets were chosen using a functional magnetic resonance imaging (fMRI)--identified network associated with sleep-deprivation--induced WM performance impairment: 2 regions from the network (upper left middle occipital gyrus and midline parietal cortex) and

B. Luber; A. D. Stanford; P. Bulow; T. Nguyen; B. C. Rakitin; C. Habeck; R. Basner; Y. Stern; S. H. Lisanby

2007-01-01

73

Transcranial magnetic stimulation as a therapeutic tool in psychiatry: what do we know about the neurobiological mechanisms?  

Microsoft Academic Search

Potential therapeutic properties of repetitive transcranial magnetic stimulation (rTMS) have been suggested in several psychiatric disorders such as depression, mania, obsessive-compulsive disorder, posttraumatic stress disorder and schizophrenia. By inducing electric currents in brain tissue via a time-varying strong magnetic field, rTMS has the potential to either directly or trans-synaptically modulate neuronal circuits thought to be dysfunctional in these psychiatric disorders.

Anke Post; Martin E. Keck

2001-01-01

74

Transcranial magnetic stimulation as a therapeutic tool in psychiatry: what do we know about the neurobiological mechanisms?  

Microsoft Academic Search

Potential therapeutic properties ofrepetitive transcranial magnetic stimulation (rTMS) have been suggested in several psychiatric disorders such as depression, mania, obsessive-compulsive disorder, posttraumatic stress disorder and schizophrenia. By inducing electric currents in brain tissue via a time-varying strong magnetic field, rTMS has the potential to either directly or trans-synapti- cally modulate neuronal circuits thought to be dysfunctional in these psychiatric disorders.

Anke Post; Martin E. Keck

2001-01-01

75

Repetitive Transcranial Magnetic Stimulation to Treat Depression and Insomnia with Chronic Low Back Pain  

PubMed Central

Transcranial magnetic stimulation (TMS) is a noninvasive and safe technique for motor cortex stimulation. TMS is used to treat neurological and psychiatric disorders, including mood and movement disorders. TMS can also treat several types of chronic neuropathic pain. The pain relief mechanism of cortical stimulation is caused by modifications in neuronal excitability. Depression is a common co-morbidity with chronic pain. Pain and depression should be treated concurrently to achieve a positive outcome. Insomnia also frequently occurs with chronic lower back pain. Several studies have proposed hypotheses for TMS pain management. Herein, we report two cases with positive results for the treatment of depression and insomnia with chronic low back pain by TMS. PMID:25031816

Park, Eun Jung; Koh, Do Yle; Han, Yoo Mi

2014-01-01

76

Update on repetitive transcranial magnetic stimulation in obsessive-compulsive disorder: different targets.  

PubMed

Obsessive-compulsive disorder (OCD) is a chronic, disabling disorder. Ten percent of patients remain treatment refractory despite several treatments. For these severe, treatment-refractory patients, repetitive transcranial magnetic stimulation (rTMS) has been suggested as a treatment option. Since 1997, in published trials, a total of 110 OCD patients have been treated with rTMS. This review aims to provide an update on rTMS treatment in patients with OCD. First, the mechanism of action is discussed, followed by the efficacy and side effects of rTMS at various brain targets, and finally implications for the future. Due to the lack of studies with comparable stimulation or treatment parameters and with reliable designs, it is difficult to draw clear conclusions. In general, rTMS appears to be effective in open-label studies; however, this has not yet been replicated in randomized, sham-controlled trials. PMID:21547545

Blom, Rianne M; Figee, Martijn; Vulink, Nienke; Denys, Damiaan

2011-08-01

77

Neural field theory of calcium dependent plasticity with applications to transcranial magnetic stimulation.  

PubMed

Calcium dependent plasticity (CaDP), a physiologically realistic plasticity mechanism in the microscopic regime, is incorporated into a neural field theory to explore system-level plasticity. This system-level plasticity model is capable of reproducing the characteristic plasticity window of spike-timing dependent plasticity (STDP) in paired associative stimulation (PAS), where a peripheral electric pulse stimulation is paired to transcranial magnetic stimulation (TMS) in the cortex, and rTMS frequency dependent plasticity, where low and high frequency rTMS trains induce depression and potentiation, respectively. These thus reproduce experimental results for system-level plasticity for the first time. This also bridges the gap between microscopic plasticity theory and system-level plasticity observed experimentally, and addresses long standing problems of stability and adaptability by predicting stable plasticity, a possible seizure state where neurons fire at a high rate, and spike-rate adaptation. PMID:23376643

Fung, P K; Robinson, P A

2013-05-01

78

[The use of repetitive transcranial magnetic stimulation (rTMS) in auditory verbal hallucinations (AVH)].  

PubMed

Up to one-third of all schizophrenic patients suffer from auditory verbal hallucinations (AVH) that are resistant to antipsychotics. The use of repetitive transcranial magnetic stimulation (rTMS) is a therapeutic option that may disrupt or attenuate treatment resistant (TR) AVHs. This article reviews the available literature on the use of rTMS to treat AVHs, particularly focusing on randomised controlled trials, which have introduced new definitions ("refractory AVHs"), and techniques (active comparator strategies and imaging-guided rTMS). A number of meta-analyses are considered, which support a range of positive effect sizes for AVH attenuation in response to rTMS. Larger maintenance and follow-up studies with clearer clinical definitions of TR AVH are required. The underlying mechanism of action of rTMS on language networks needs further clarification and future trials should focus on methods for assessing AVH changes, time courses of response, and the development of response markers. PMID:20648414

Jandl, M

2010-11-01

79

Repetitive transcranial magnetic stimulation induces kf-1 expression in the rat brain.  

PubMed

Repetitive transcranial magnetic stimulation (rTMS) is a non-invasive approach used for stimulating the brain, and has proven effective in the treatment of depression, however the mechanism of its antidepressant action is unknown. Recently, we have reported the induction of kf-1 in rat frontal cortex and hippocampus after chronic antidepressant treatment and repeated electroconvulsive treatment (ECT). In this study, we demonstrated the induction of kf-1 after rTMS in the rat frontal cortex and hippocampus, but not in hypothalamus. Our data suggest that kf-1 may be a common functional molecule that is increased after antidepressant treatment, ECT and rTMS. In conclusion, it is proposed that induction of kf-1 may be associated with the treatment induced adaptive neural plasticity in the brain, which is a long-term target for their antidepressant action. PMID:15763074

Kudo, Kentaro; Yamada, Misa; Takahashi, Kou; Nishioka, Gentaro; Tanaka, Satoshi; Hashiguchi, Tomo; Fukuzako, Hiroshi; Takigawa, Morikuni; Higuchi, Teruhiko; Momose, Kazutaka; Kamijima, Kunitoshi; Yamada, Mitsuhiko

2005-04-01

80

Chronic repetitive transcranial magnetic stimulation induces subsensitivity of presynaptic serotonergic autoreceptor activity in rat brain.  

PubMed

Repetitive transcranial magnetic stimulation (rTMS) is a novel procedure which has proven effective in the treatment of major depression. We administered rTMS chronically to rats in order to determine whether this procedure affected serotonergic neurotransmission in the prefrontal cortex. Basal 5-HT levels, and the effects of challenges with the 5-HT1A receptor agonist 8-OH-DPAT and the 5-HT1B antagonist GR 127935 on 5-HT levels were determined using in vivo microdialysis. Rats which had undergone chronic rTMS showed reduced responses to both challenges, indicating subsensitivity of both the presynaptic 5-HT1A autoreceptors situated somatodendritically in the raphe nuclei and the 5-HT1B autoreceptors situated on nerve terminals. Since such subsensitivity has been demonstrated after other antidepressant treatments, our results indicate that these treatments and rTMS may have a common mechanism of action. PMID:11006967

Gur, E; Lerer, B; Dremencov, E; Newman, M E

2000-09-11

81

Slow repetitive transcranial magnetic stimulation increases somatosensory high-frequency oscillations in humans.  

PubMed

Repetitive transcranial magnetic stimulation (rTMS) has been proposed as a possible treatment for psychiatric and neurological disorders characterized by focal brain excitability, such as major depression and action myoclonus. However, the mechanism of modulating excitability by rTMS is unclear. We examined the changes in high frequency oscillations (HFOs) of somatosensory evoked potentials (SEPs) before and after slow rTMS over the right primary somatosensory cortex (0.5 Hz, 50 pulses, 80% motor threshold intensity). The HFOs, which represent a localized activity of intracortical inhibitory interneurons, were significantly increased after slow rTMS, while the SEPs were not changed. Our results suggest that slow rTMS affects cortical excitability by modulating the activity of the intracortical inhibitory interneurons beyond the time of the stimulation and that rTMS may have therapeutic effects on such disorders. PMID:15039114

Ogawa, Asao; Ukai, Satoshi; Shinosaki, Kazuhiro; Yamamoto, Masakiyo; Kawaguchi, Shunsuke; Ishii, Ryouhei; Takeda, Masatoshi

2004-04-01

82

Transcranial Magnetic Stimulation for the Treatment of Pharmacoresistant Nondelusional Auditory Verbal Hallucinations in Dementia  

PubMed Central

Auditory verbal hallucinations (AVHs) are known as a core symptom of schizophrenia, but also occur in a number of other conditions, not least in neurodegenerative disorders such as dementia. In the last decades, Transcranial Magnetic Stimulation (TMS) emerged as a valuable therapeutic approach towards several neurological and psychiatric diseases, including AVHs. Herein we report a case of a seventy-six-years-old woman with vascular-degenerative brain disease, complaining of threatening AVHs. The patient was treated with a high-frequency temporoparietal (T3P3) rTMS protocol for fifteen days. A considerable reduction of AVHs in frequency and content (no more threatening) was observed. Although further research is needed, this seems an encouraging result. PMID:24198993

2013-01-01

83

Pharmacological, experimental therapeutic, and transcranial magnetic stimulation treatments for compulsivity and impulsivity.  

PubMed

Obsessive-compulsive disorder (OCD) has been recently drawn apart from anxiety disorder by the Diagnostic and Statistical Manual of Mental Disorders, 5th edition (DSM-5) and clustered together with related disorders (eg, hoarding, hair pulling disorder, skin picking), which with it seems to share clinical and neurophysiological similarities. Recent literature has mainly explored brain circuitries (eg, orbitofrontal cortex, striatum), molecular pathways, and genes (eg, Hoxb8, Slitrk5, Sapap3) that represent the new target of the treatments; they also lead the development of new probes and compounds. In the therapeutic field, monotherapy with cognitive behavioral therapy (CBT) or selective serotonin reuptake inhibitors (SSRIs) is recommendable, but combination or augmentation with a dopaminergic or glutamatergic agent is often adopted. A promising therapy for OCD is represented by repetitive transcranial magnetic stimulation (rTMS), which is suitable to treat compulsivity and impulsivity depending on the protocol of stimulation and the brain circuitries targeted. PMID:24176028

Pallanti, Stefano; Hollander, Eric

2014-02-01

84

Functional Neurosurgery in the Human Thalamus by Transcranial Magnetic Resonance Guided Focused Ultrasound  

NASA Astrophysics Data System (ADS)

Potential applications of Transcranial Magnetic Resonance guided Focused Ultrasound (TcMRgFUS) include treatment of functional brain disorders, such as Parkinson's disease, dystonia and tremor, neurogenic pain and tinnitus, neuropsychiatric disorders and epilepsy. In this study we demonstrate the feasibility of non-invasive TcMRgFUS ablation of clinically well established targets in the human thalamus that are currently accessed stereotactically by interventional strategies based on the concept of the thalamocortical dysrhythmia (TCD). Thermal hotspots suitable for clinical intervention were created successfully in anatomical preparations of human ex-vivo heads under pseudo clinical conditions. The hotspots could be positioned at the target locations as needed and local energy deposition was sufficient to create tissue ablation. Numerical simulations based on these experimental data predict that the acoustic energy needed to create ablative lesions in-vivo will be within limits that can safely applied.

Werner, Beat; Morel, Anne; Jeanmonod, Daniel; Martin, Ernst

2009-04-01

85

Navigated transcranial magnetic stimulation in preoperative planning for the treatment of motor area cavernous angiomas  

PubMed Central

Since the introduction of microscopic techniques, radical surgery for cavernous angiomas has become a recommended treatment option. However, the treatment of motor area cavernous angioma represents a great challenge for the surgical team. Here, we describe an approach guided by frameless neuronavigation and preoperative functional mapping with transcranial magnetic stimulation (TMS), for surgical planning. We used TMS to map the motor cortex and its relationship with the angioma. We achieved complete resection of the lesions in the surgeries, while avoiding areas of motor response identified during the preoperative mapping. We verified the complete control of seizures (Engel class 1A) in the patients with previous refractory epilepsy. Postsurgery, one patient was seizure-free without medication, and two patients required only one medication for seizure control. Thus, navigated TMS appears to be a useful tool, in preoperative planning for cavernous angiomas of the motor area. PMID:24353424

Paiva, Wellingson Silva; Fonoff, Erich Talamoni; Marcolin, Marco Antonio; Bor-Seng-Shu, Edson; Figueiredo, Eberval Gadelha; Teixeira, Manoel Jacobsen

2013-01-01

86

Long-term repetitive transcranial magnetic stimulation therapy: new research questions arising from one tinnitus case?  

PubMed

Tinnitus may become refractory to treatment and disabling. Brain transcranial magnetic stimulation (TMS) has shown promise as a therapy, but has been employed primarily short-term. We treated a patient with 5?weeks of weekly repetitive TMS (rTMS), followed by 6?months of monthly rTMS. He was a 75-year-old dentist with chronic tinnitus from occupational noise exposure. Physical examination and MRIs of the auditory canals and brain had revealed no lesions. The patient showed a general gradual, progressive improvement on per cent of severe tinnitus diary days (from baseline 100% to 33%), tinnitus handicap inventory (from baseline score 70 to 18), and mini-tinnitus questionnaire (from baseline score 17 to 6). No changes occurred in serial audiograms. Transient adverse events were a headache during stimulation, and dizziness 30?min after treatment. Implications and questions for future non-invasive neuromodulation clinical research raised by our case are discussed. PMID:25538216

Labar, Douglas Richard; Cortes, Mar; Edwards, Dylan

2014-01-01

87

Simultaneous transcranial magnetic stimulation and single neuron recording in alert non-human primates  

PubMed Central

Transcranial magnetic stimulation (TMS) is a widely used, noninvasive method for stimulating nervous tissue, yet its mechanisms of effect are poorly understood. Here we report novel methods for studying the influence of TMS on single neurons in the brain of alert non-human primates. We designed a TMS coil that focuses its effect near the tip of a recording electrode and recording electronics that enable direct acquisition of neuronal signals at the site of peak stimulus strength minimally perturbed by stimulation artifact in intact, awake monkeys (Macaca mulatta). We recorded action potentials within ~1 ms after 0.4 ms TMS pulses and observed changes in activity that differed significantly for active stimulation as compared to sham stimulation. The methodology is compatible with standard equipment in primate laboratories, allowing for easy implementation. Application of these new tools will facilitate the refinement of next generation TMS devices, experiments, and treatment protocols. PMID:24974797

Mueller, Jerel K.; Grigsby, Erinn M.; Prevosto, Vincent; Petraglia, Frank W.; Rao, Hrishikesh; Deng, Zhi-De; Peterchev, Angel V.; Sommer, Marc A.; Egner, Tobias; Platt, Michael L.; Grill, Warren M.

2014-01-01

88

Maintaining remission of depression with repetitive transcranial magnetic stimulation during pregnancy: a case report.  

PubMed

It is important to explore potential safe treatment options for the ongoing treatment of women's depression during pregnancy. One promising treatment is repetitive transcranial magnetic stimulation (rTMS). We report on the case of a woman who became pregnant while receiving regular maintenance rTMS combined with pharmacotherapy treatment for major depressive episode. The patient achieved remission following two acute courses of rTMS and continued with maintenance rTMS treatment over the course of 4 years, during which she became pregnant and gave birth to a healthy infant. Her remission was maintained over this time including during and after her pregnancy. There were no adverse effects to the patient or her infant during the pregnancy or in the post-natal period. Maintenance rTMS may be an effective and feasible treatment option for depression during pregnancy. PMID:24638141

Burton, Cassandra; Gill, Shane; Clarke, Patrick; Galletly, Cherrie

2014-06-01

89

Transcranial magnetic stimulation in partial epilepsy: drug-induced changes of motor excitability.  

PubMed

Single-pulse transcranial magnetic stimulation (s-TMS) with recording of motor evoked potentials (MEPs) from thenar muscles of both hands was performed on 84 patients with cryptogenic partial epilepsy and 50 healthy controls. We analyzed the cortical latency (CL), central conduction time (CCT), and threshold intensity (TI) required to elicit liminal MEPs at rest. In the patients, CL and CCT were normal, but TI was significantly higher than in the controls. Of the 84 patients, 65 were taking one or more antiepileptic drugs and 19 were untreated. The untreated patients had a significantly lower TI than the treated patients. In the treated patients, the TI increase paralleled the number of drugs taken. Additionally, in 2 subgroups of patients undergoing major modifications of antiepileptic treatment, TI dropped after partial withdrawal of medication and increased following the commencement of therapy. The results suggest that anticonvulsants depress the excitability of human motor pathways in epileptic subjects. PMID:8874589

Michelucci, R; Passarelli, D; Riguzzi, P; Buzzi, A M; Gardella, E; Tassinari, C A

1996-07-01

90

Adapted filter banks for feature extraction in transcranial magnetic stimulation evoked responses.  

PubMed

A novel adaptive and approximate shift-invariant wavelet packet feature extraction scheme for event-related potentials (ERPs) in the electroencephalogram (EEG) is introduced in this paper. In this algorithm, the shift-invariant wavelet packed decomposition is done by integrating a cost function for decimation decision in each sub-band expansion. Additionally, a shape adaptation of the wavelet is implemented to find the best adapted wavelet shape for a given class of ERPs. This scheme is used to analyze the time course of the impact of single-pulse transcranial magnetic stimulation (TMS) to the auditory ERPs. We show that the proposed scheme is able to extract even slightest impacts of TMS, making it a promising tool for the extraction of weak ERPs components, particularly in hybrid TMS-EEG/ERP setups. PMID:21222168

Harris, Arief R; Schwerdtfeger, Karsten; Strauss, Daniel J

2011-02-01

91

The contribution of transcranial magnetic stimulation in the diagnosis and in the management of dementia.  

PubMed

Transcranial magnetic stimulation (TMS) is emerging as a promising tool to non-invasively assess specific cortical circuits in neurological diseases. A number of studies have reported the abnormalities in TMS assays of cortical function in dementias. A PubMed-based literature review on TMS studies targeting primary and secondary dementia has been conducted using the key words "transcranial magnetic stimulation" or "motor cortex excitability" and "dementia" or "cognitive impairment" or "memory impairment" or "memory decline". Cortical excitability is increased in Alzheimer's disease (AD) and in vascular dementia (VaD), generally reduced in secondary dementias. Short-latency afferent inhibition (SAI), a measure of central cholinergic circuitry, is normal in VaD and in frontotemporal dementia (FTD), but suppressed in AD. In mild cognitive impairment, abnormal SAI may predict the progression to AD. No change in cortical excitability has been observed in FTD, in Parkinson's dementia and in dementia with Lewy bodies. Short-interval intracortical inhibition and controlateral silent period (cSP), two measures of gabaergic cortical inhibition, are abnormal in most dementias associated with parkinsonian symptoms. Ipsilateral silent period (iSP), which is dependent on integrity of the corpus callosum is abnormal in AD. While single TMS measure owns low specificity, a panel of measures can support the clinical diagnosis, predict progression and possibly identify earlier the "brain at risk". In dementias, TMS can be also exploited to select and evaluate the responders to specific drugs and, it might become a rehabilitative tool, in the attempt to restore impaired brain plasticity. PMID:24840904

Cantone, Mariagiovanna; Di Pino, Giovanni; Capone, Fioravante; Piombo, Marianna; Chiarello, Daniela; Cheeran, Binith; Pennisi, Giovanni; Di Lazzaro, Vincenzo

2014-08-01

92

Repetitive transcranial magnetic stimulation (rTMS) in a patient suffering from comorbid depression and panic disorder following a myocardial infarction.  

PubMed

Application of repetitive transcranial magnetic stimulation was effective and safe in treating a 55-year-old man with comorbid depression and panic disorder, which occurred 6 months after a myocardial infarction. PMID:16631291

Sakkas, Pavlos; Psarros, Constantin; Papadimitriou, George N; Theleritis, Christos G; Soldatos, Constantin R

2006-07-01

93

Repetitive Transcranial Magnetic Stimulation in the Treatment of Obsessive-Compulsive Disorder and Other Anxiety Disorders Repetitive Transcranial Magnetic Stimulation in the Treatment of Obsessive-Compulsive Disorder and Other Anxiety Disorders  

Microsoft Academic Search

Repetitive transcranial magnetic stimulation (rTMS) is being investigated as a treatment of psychiatric disorders. This chapter reviews publications of the treatment of anxiety disorders: obsessive-compulsive disorder (OCD), posttraumatic stress disorder (PTSD) and panic disorder (PD). No definite conclusions can be reached as insufficient work has been completed. Many reports are single-case or small case studies and there have been few

S. Pridmore; M. Marcolin; C. Ribeiro; C. Mansur

2007-01-01

94

Transcranial magnetic stimulation of mouse brain using high-resolution anatomical models  

NASA Astrophysics Data System (ADS)

Transcranial magnetic stimulation (TMS) offers the possibility of non-invasive treatment of brain disorders in humans. Studies on animals can allow rapid progress of the research including exploring a variety of different treatment conditions. Numerical calculations using animal models are needed to help design suitable TMS coils for use in animal experiments, in particular, to estimate the electric field induced in animal brains. In this paper, we have implemented a high-resolution anatomical MRI-derived mouse model consisting of 50 tissue types to accurately calculate induced electric field in the mouse brain. Magnetic field measurements have been performed on the surface of the coil and compared with the calculations in order to validate the calculated magnetic and induced electric fields in the brain. Results show how the induced electric field is distributed in a mouse brain and allow investigation of how this could be improved for TMS studies using mice. The findings have important implications in further preclinical development of TMS for treatment of human diseases.

Crowther, L. J.; Hadimani, R. L.; Kanthasamy, A. G.; Jiles, D. C.

2014-05-01

95

Induction of central nervous system plasticity by repetitive transcranial magnetic stimulation to promote sensorimotor recovery in incomplete spinal cord injury  

PubMed Central

Cortical and spinal cord plasticity may be induced with non-invasive transcranial magnetic stimulation to encourage long term potentiation or depression of neuronal circuits. Such plasticity inducing stimulation provides an attractive approach to promote changes in sensorimotor circuits that have been degraded by spinal cord injury (SCI). If residual corticospinal circuits can be conditioned appropriately there should be the possibility that the changes are accompanied by functional recovery. This article reviews the attempts that have been made to restore sensorimotor function and to obtain functional benefits from the application of repetitive transcranial magnetic stimulation (rTMS) of the cortex following incomplete spinal cord injury. The confounding issues that arise with the application of rTMS, specifically in SCI, are enumerated. Finally, consideration is given to the potential for rTMS to be used in the restoration of bladder and bowel sphincter function and consequent functional recovery of the guarding reflex. PMID:24904326

Ellaway, Peter H.; Vásquez, Natalia; Craggs, Michael

2014-01-01

96

Repetitive transcranial magnetic stimulation in a patient suffering from depression and rheumatoid arthritis: evidence for immunomodulatory effects.  

PubMed

Repetitive transcranial magnetic stimulation (rTMS) has been suggested as antidepressive treatment strategy. The mechanism of action by which the antidepressive effect is brought about remains unclear at present. Here, we report findings in a patient suffering from recurrent major depression and rheumatoid arthritis. Improvement of depressive symptoms during 20 Hz rTMS of the left dorsolateral prefrontal cortex was repeatedly associated with a systemic inflammatory reaction, suggesting that rTMS induced an immunomodulatory effect. PMID:16136019

Langguth, Berthold; Braun, Susanne; Aigner, Josef M; Landgrebe, Michael; Weinerth, Jutta; Hajak, Göran; Eichhammer, Peter

2005-08-01

97

Chronic repetitive transcranial magnetic stimulation is antidepressant but not anxiolytic in rat models of anxiety and depression  

Microsoft Academic Search

Transcranial magnetic stimulation (TMS) has been proposed as a treatment for depression and anxiety disorders. While the antidepressant effect has been modelled in animals, there have been few attempts to examine a possible anxiolytic effect of repetitive TMS (rTMS) in animal models. We administered 18 days of rTMS to male Sprague-Dawley rats. On days 10 through 18, rats were tested

Garth A. Hargreaves; Iain S. McGregor; Perminder S. Sachdev

2005-01-01

98

Antioxidant-Like Effects and Protective Action of Transcranial Magnetic Stimulation in Depression Caused by Olfactory Bulbectomy  

Microsoft Academic Search

We studied the effects of transcranial magnetic stimulation (TMS, 60 Hz and 0.7 mT for 4 h\\/day for 14 days) on oxidative and\\u000a cell damage caused by olfactory bulbectomy (OBX) in Wistar rats. The levels of lipid peroxidation products and caspase-3 were\\u000a enhanced by OBX, whereas it prompted a reduction in reduced glutathione (GSH) content and antioxidative enzymes activities.\\u000a The treatment with TMS reverted

Inmaculada TassetReneDrucker-Colõ ´; René Drucker-Colín; José Peña; Ignacio Jimena; Pedro Montilla; Francisco Javier Medina; Isaac Túnez

2010-01-01

99

Does a single session of theta-burst transcranial magnetic stimulation of inferior temporal cortex affect tinnitus perception?  

Microsoft Academic Search

BACKGROUND: Cortical excitability changes as well as imbalances in excitatory and inhibitory circuits play a distinct pathophysiological role in chronic tinnitus. Repetitive transcranial magnetic stimulation (rTMS) over the temporoparietal cortex was recently introduced to modulate tinnitus perception. In the current study, the effect of theta-burst stimulation (TBS), a novel rTMS paradigm was investigated in chronic tinnitus. Twenty patients with chronic

Csaba Poreisz; Walter Paulus; Tobias Moser; Nicolas Lang

2009-01-01

100

Effects of successive repetitive transcranial magnetic stimulation on motor performances and brain perfusion in idiopathic Parkinson's disease  

Microsoft Academic Search

We studied the effects of 0.2 Hz repetitive transcranial magnetic stimulation (rTMS) successively performed 6 times for 2 weeks in 12 patients with idiopathic Parkinson's disease (PD). Ten patients received rTMS to the bilateral frontal cortex (frontal rTMS) and six patients received rTMS to the bilateral occipital cortex (occipital rTMS). Before and after rTMS, we evaluated regional cerebral blood flow

Michiko Ikeguchi; Tetsuo Touge; Yoshihiro Nishiyama; Hiroaki Takeuchi; Shigeki Kuriyama; Motoomi Ohkawa

2003-01-01

101

Transcranial magnetic stimulation for the treatment of depression: feasibility and results under naturalistic conditions: a retrospective analysis  

Microsoft Academic Search

An increasing number of controlled studies strongly support an antidepressant effect of high-frequency repetitive transcranial\\u000a magnetic stimulation (rTMS) over the left dorsolateral prefrontal cortex. However, these data come from highly selected study\\u000a populations. Whether rTMS is a feasible therapeutic tool for the treatment of depression under naturalistic condition has\\u000a not yet been addressed. Here, we report results from 232 depressive

Elmar Frank; Peter Eichhammer; Julia Burger; Marc Zowe; Michael Landgrebe; Göran Hajak; Berthold Langguth

2011-01-01

102

Effects of low-frequency repetitive transcranial magnetic stimulation on event-related potential P300  

NASA Astrophysics Data System (ADS)

The present study analyzed the effects of repetitive transcranial magnetic stimulation (rTMS) on brain activity. P300 latency of event-related potential (ERP) was used to evaluate the effects of low-frequency and short-term rTMS by stimulating the supramarginal gyrus (SMG), which is considered to be the related area of P300 origin. In addition, the prolonged stimulation effects on P300 latency were analyzed after applying rTMS. A figure-eight coil was used to stimulate left-right SMG, and intensity of magnetic stimulation was 80% of motor threshold. A total of 100 magnetic pulses were applied for rTMS. The effects of stimulus frequency at 0.5 or 1 Hz were determined. Following rTMS, an odd-ball task was performed and P300 latency of ERP was measured. The odd-ball task was performed at 5, 10, and 15 min post-rTMS. ERP was measured prior to magnetic stimulation as a control. Electroencephalograph (EEG) was measured at Fz, Cz, and Pz that were indicated by the international 10-20 electrode system. Results demonstrated that different effects on P300 latency occurred between 0.5-1 Hz rTMS. With 1 Hz low-frequency magnetic stimulation to the left SMG, P300 latency decreased. Compared to the control, the latency time difference was approximately 15 ms at Cz. This decrease continued for approximately 10 min post-rTMS. In contrast, 0.5 Hz rTMS resulted in delayed P300 latency. Compared to the control, the latency time difference was approximately 20 ms at Fz, and this delayed effect continued for approximately 15 min post-rTMS. Results demonstrated that P300 latency varied according to rTMS frequency. Furthermore, the duration of the effect was not similar for stimulus frequency of low-frequency rTMS.

Torii, Tetsuya; Sato, Aya; Iwahashi, Masakuni; Iramina, Keiji

2012-04-01

103

The influence of sulcus width on simulated electric fields induced by transcranial magnetic stimulation  

PubMed Central

Volume conduction models can help in acquiring knowledge about the distribution of the electric field induced by transcranial magnetic stimulation (TMS). One aspect of a detailed model is an accurate description of the cortical surface geometry. Since its estimation is difficult, it is important to know how accurate the geometry has to be represented. Previous studies only looked at the differences caused by neglecting the complete boundary between the CSF and GM (Thielscher et al. 2011; Bijsterbosch et al. 2012), or by resizing the whole brain (Wagner et al. 2008). However, due to the high conductive properties of the CSF, it can be expected that alterations in sulcus width can already have a significant effect on the distribution of the electric field. To answer this question, the sulcus width of a highly realistic head model, based on T1-, T2- and diffusion-weighted magnetic resonance images (MRI), was altered systematically. This study shows that alterations in the sulcus width do not cause large differences in the majority of the electric field values. However, considerable overestimation of sulcus width produces an overestimation of the calculated field strength, also at locations distant from the target location. PMID:23787706

Janssen, A M; Rampersad, S M; Lucka, F; Lanfer, B; Lew, S; Aydin, Ü; Wolters, C H; Stegeman, D F; Oostendorp, T F

2013-01-01

104

Transcranial Magnetic Stimulation for Investigating Causal Brain-behavioral Relationships and their Time Course  

PubMed Central

Transcranial magnetic stimulation (TMS) is a safe, non-invasive brain stimulation technique that uses a strong electromagnet in order to temporarily disrupt information processing in a brain region, generating a short-lived “virtual lesion.” Stimulation that interferes with task performance indicates that the affected brain region is necessary to perform the task normally. In other words, unlike neuroimaging methods such as functional magnetic resonance imaging (fMRI) that indicate correlations between brain and behavior, TMS can be used to demonstrate causal brain-behavior relations. Furthermore, by varying the duration and onset of the virtual lesion, TMS can also reveal the time course of normal processing. As a result, TMS has become an important tool in cognitive neuroscience. Advantages of the technique over lesion-deficit studies include better spatial-temporal precision of the disruption effect, the ability to use participants as their own control subjects, and the accessibility of participants. Limitations include concurrent auditory and somatosensory stimulation that may influence task performance, limited access to structures more than a few centimeters from the surface of the scalp, and the relatively large space of free parameters that need to be optimized in order for the experiment to work. Experimental designs that give careful consideration to appropriate control conditions help to address these concerns. This article illustrates these issues with TMS results that investigate the spatial and temporal contributions of the left supramarginal gyrus (SMG) to reading. PMID:25079670

Sliwinska, Magdalena W.; Vitello, Sylvia; Devlin, Joseph T.

2014-01-01

105

Modulation of EEG Functional Connectivity Networks in Subjects Undergoing Repetitive Transcranial Magnetic Stimulation  

PubMed Central

Transcranial magnetic stimulation (TMS) is a noninvasive brain stimulation technique that utilizes magnetic fluxes to alter cortical activity. Continuous theta-burst repetitive TMS (cTBS) results in long-lasting decreases in indices of cortical excitability, and alterations in performance of behavioral tasks. We investigated the effects of cTBS on cortical function via functional connectivity and graph theoretical analysis of EEG data. Thirty-one channel resting-state EEG recordings were obtained before and after 40 s of cTBS stimulation to the left primary motor cortex. Functional connectivity between nodes was assessed in multiple frequency bands using lagged max-covariance, and subsequently thresholded to construct undirected graphs. After cTBS, we find widespread decreases in functional connectivity in the alpha band. There are also simultaneous increases in functional connectivity in the high-beta bands, especially amongst anterior and interhemispheric connections. The analysis of the undirected graphs reveals that interhemispheric and interregional connections are more likely to be modulated after cTBS than local connections. There is also a shift in the topology of network connectivity, with an increase in the clustering coefficient after cTBS in the beta bands, and a decrease in clustering and increase in path length in the alpha band, with the alpha-band connectivity primarily decreased near the site of stimulation. cTBS produces widespread alterations in cortical functional connectivity, with resulting shifts in cortical network topology. PMID:23471637

Shafi, Mouhsin M.; Westover, M. Brandon; Oberman, Lindsay; Cash, Sydney S.; Pascual-Leone, Alvaro

2014-01-01

106

The influence of sulcus width on simulated electric fields induced by transcranial magnetic stimulation.  

PubMed

Volume conduction models can help in acquiring knowledge about the distribution of the electric field induced by transcranial magnetic stimulation. One aspect of a detailed model is an accurate description of the cortical surface geometry. Since its estimation is difficult, it is important to know how accurate the geometry has to be represented. Previous studies only looked at the differences caused by neglecting the complete boundary between cerebrospinal fluid (CSF) and grey matter (Thielscher et al 2011 NeuroImage 54 234-43, Bijsterbosch et al 2012 Med. Biol. Eng. Comput. 50 671-81), or by resizing the whole brain (Wagner et al 2008 Exp. Brain Res. 186 539-50). However, due to the high conductive properties of the CSF, it can be expected that alterations in sulcus width can already have a significant effect on the distribution of the electric field. To answer this question, the sulcus width of a highly realistic head model, based on T1-, T2- and diffusion-weighted magnetic resonance images, was altered systematically. This study shows that alterations in the sulcus width do not cause large differences in the majority of the electric field values. However, considerable overestimation of sulcus width produces an overestimation of the calculated field strength, also at locations distant from the target location. PMID:23787706

Janssen, A M; Rampersad, S M; Lucka, F; Lanfer, B; Lew, S; Aydin, U; Wolters, C H; Stegeman, D F; Oostendorp, T F

2013-07-21

107

Cerebellar Transcranial Magnetic Stimulation: The Role of Coil Geometry and Tissue Depth?  

PubMed Central

Background While transcranial magnetic stimulation (TMS) coil geometry has important effects on the evoked magnetic field, no study has systematically examined how different coil designs affect the effectiveness of cerebellar stimulation. Hypothesis The depth of the cerebellar targets will limit efficiency. Angled coils designed to stimulate deeper tissue are more effective in eliciting cerebellar stimulation. Methods Experiment 1 examined basic input–output properties of the figure-of-eight, batwing and double-cone coils, assessed with stimulation of motor cortex. Experiment 2 assessed the ability of each coil to activate cerebellum, using cerebellar-brain inhibition (CBI). Experiment 3 mapped distances from the scalp to cerebellar and motor cortical targets in a sample of 100 subjects' structural magnetic resonance images. Results Experiment 1 showed batwing and double-cone coils have significantly lower resting motor thresholds, and recruitment curves with steeper slopes than the figure-of-eight coil. Experiment 2 showed the double-cone coil was the most efficient for eliciting CBI. The batwing coil induced CBI only at higher stimulus intensities. The figure-of-eight coil did not elicit reliable CBI. Experiment 3 confirmed that cerebellar tissue is significantly deeper than primary motor cortex tissue, and we provide a map of scalp-to-target distances. Conclusions The double-cone and batwing coils designed to stimulate deeper tissue can effectively stimulate cerebellar targets. The double-cone coil was found to be most effective. The depth map provides a guide to the accessible regions of the cerebellar volume. These results can guide coil selection and stimulation parameters when designing cerebellar TMS studies. PMID:24924734

Hardwick, Robert M.; Lesage, Elise; Miall, R. Chris

2014-01-01

108

Interdisciplinary Approaches of Transcranial Magnetic Stimulation Applied to a Respiratory Neuronal Circuitry Model  

PubMed Central

Respiratory related diseases associated with the neuronal control of breathing represent life-threatening issues and to date, no effective therapeutics are available to enhance the impaired function. The aim of this study was to determine whether a preclinical respiratory model could be used for further studies to develop a non-invasive therapeutic tool applied to rat diaphragmatic neuronal circuitry. Transcranial magnetic stimulation (TMS) was performed on adult male Sprague-Dawley rats using a human figure-of-eight coil. The largest diaphragmatic motor evoked potentials (MEPdia) were recorded when the center of the coil was positioned 6 mm caudal from Bregma, involving a stimulation of respiratory supraspinal pathways. Magnetic shielding of the coil with mu metal reduced magnetic field intensities and improved focality with increased motor threshold and lower amplitude recruitment curve. Moreover, transynaptic neuroanatomical tracing with pseudorabies virus (applied to the diaphragm) suggest that connections exist between the motor cortex, the periaqueductal grey cell regions, several brainstem neurons and spinal phrenic motoneurons (distributed in the C3-4 spinal cord). These results reveal the anatomical substrate through which supraspinal stimulation can convey descending action potential volleys to the spinal motoneurons (directly or indirectly). We conclude that MEPdia following a single pulse of TMS can be successfully recorded in the rat and may be used in the assessment of respiratory supraspinal plasticity. Supraspinal non-invasive stimulations aimed to neuromodulate respiratory circuitry will enable new avenues of research into neuroplasticity and the development of therapies for respiratory dysfunction associated with neural injury and disease (e.g. spinal cord injury, amyotrophic lateral sclerosis). PMID:25406091

Vinit, Stéphane; Keomani, Emilie; Deramaudt, Thérèse B.; Spruance, Victoria M.; Bezdudnaya, Tatiana; Lane, Michael A.

2014-01-01

109

Repetitive transcranial magnetic stimulation enhances BDNF-TrkB signaling in both brain and lymphocyte.  

PubMed

Repetitive transcranial magnetic stimulation (rTMS) induces neuronal long-term potentiation or depression. Although brain-derived neurotrophic factor (BDNF) and its cognate tyrosine receptor kinase B (TrkB) contribute to the effects of rTMS, their precise role and underlying mechanism remain poorly understood. Here we show that daily 5 Hz rTMS for 5 d improves BDNF-TrkB signaling in rats by increasing the affinity of BDNF for TrkB, which results in higher tyrosine-phosphorylated TrkB, increased recruitment of PLC-?1 and shc/N-shc to TrkB, and heightened downstream ERK2 and PI-3K activities in prefrontal cortex and in lymphocytes. The elevated BDNF-TrkB signaling is accompanied by an increased association between the activated TrkB and NMDA receptor (NMDAR). In normal human subjects, 5 d rTMS to motor cortex decreased resting motor threshold, which correlates with heightened BDNF-TrkB signaling and intensified TrkB-NMDAR association in lymphocytes. These findings suggest that rTMS to cortex facilitates BDNF-TrkB-NMDAR functioning in both cortex and lymphocytes. PMID:21795553

Wang, Hoau-Yan; Crupi, Domenica; Liu, Jingjing; Stucky, Andres; Cruciata, Giuseppe; Di Rocco, Alessandro; Friedman, Eitan; Quartarone, Angelo; Ghilardi, M Felice

2011-07-27

110

Parietal influence on temporal encoding indexed by simultaneous transcranial magnetic stimulation and electroencephalography.  

PubMed

Previous studies have suggested that contingent negative variation (CNV), as recorded by electroencaphalography (EEG), may serve as an index of temporal encoding. The interpretation of these studies is complicated by the fact that, in a majority of studies, the CNV signal was obtained at a time when subjects were not only registering stimulus duration but also making decisions and preparing to act. Previously, we demonstrated that repetitive transcranial magnetic stimulation (rTMS) of the right supramarginal gyrus (rSMG) in humans lengthened the perceived duration of a visual stimulus (Wiener et al., 2010a), suggesting the rSMG is involved in basic encoding processes. Here, we report a replication of this effect with simultaneous EEG recordings during the encoding of stimulus duration. Stimulation of the rSMG led to an increase in perceived duration and the amplitude of N1 and CNV components recorded from frontocentral sites. Furthermore, the size of the CNV amplitude, but not N1, positively correlated with the size of the rTMS effect but negatively correlated with bias (the baseline tendency to report a comparison stimulus as shorter), suggesting that the CNV indexes stimulus duration. These results suggest that a feedforward mechanism from parietal to prefrontal regions mediates temporal encoding and demonstrate a dissociation between early and late phases of encoding processes. PMID:22933807

Wiener, Martin; Kliot, Dasha; Turkeltaub, Peter E; Hamilton, Roy H; Wolk, David A; Coslett, H Branch

2012-08-29

111

Disruptions to human speed perception induced by motion adaptation and transcranial magnetic stimulation.  

PubMed

To investigate the underlying nature of the effects of transcranial magnetic stimulation (TMS) on speed perception, we applied repetitive TMS (rTMS) to human V5/MT+ following adaptation to either fast- (20 deg/s) or slow (4 deg/s)-moving grating stimuli. The adapting stimuli induced changes in the perceived speed of a standard reference stimulus moving at 10 deg/s. In the absence of rTMS, adaptation to the slower stimulus led to an increase in perceived speed of the reference, whilst adaptation to the faster stimulus produced a reduction in perceived speed. These induced changes in speed perception can be modelled by a ratio-taking operation of the outputs of two temporally tuned mechanisms that decay exponentially over time. When rTMS was applied to V5/MT+ following adaptation, the perceived speed of the reference stimulus was reduced, irrespective of whether adaptation had been to the faster- or slower-moving stimulus. The fact that rTMS after adaptation always reduces perceived speed, independent of which temporal mechanism has undergone adaptation, suggests that rTMS does not selectively facilitate activity of adapted neurons but instead leads to suppression of neural function. The results highlight the fact that potentially different effects are generated by TMS on adapted neuronal populations depending upon whether or not they are responding to visual stimuli. PMID:19912329

Burton, M P; McKeefry, D J; Barrett, B T; Vakrou, C; Morland, A B

2009-11-01

112

Relation between responses to repetitive transcranial magnetic stimulation and partial sleep deprivation in major depression.  

PubMed

Repetitive transcranial magnetic stimulation (rTMS) has been found to ameliorate symptoms in major depression. However, its mechanism of action has to be further elucidated and the relationship between responses to rTMS and other antidepressant interventions except electroconvulsive therapy has not been investigated to date. Here we studied in an open trial whether the response to partial sleep deprivation may predict the clinical outcome of rTMS treatment. Thirty-three drug-free patients suffering from a major depressive episode underwent a partial sleep deprivation at least 5 days prior to rTMS and subsequently received 10 sessions of 10 Hz rTMS of the left prefrontal cortex. After rTMS a significant overall improvement of 32% on the Hamilton Rating Scale for Depression was observed. Forty-two percent of patients showed an antidepressant response after rTMS. Amelioration of depression after partial sleep deprivation was inversely correlated with improvement after rTMS. There was no clinically applicable predictive value of the response to partial sleep deprivation for the outcome after rTMS. Apparently, different subgroups of depressed patients respond to both interventions. Further studies are needed to characterize the response to rTMS by means of clinical and biological parameters. PMID:11886690

Padberg, Frank; Schüle, Cornelius; Zwanzger, Peter; Baghai, Thomas; Ella, Robin; Mikhaiel, Patrick; Hampel, Harald; Möller, Hans-Jürgen; Rupprecht, Rainer

2002-01-01

113

Repetitive transcranial magnetic stimulation: a possible novel therapeutic approach to eating disorders.  

PubMed

The two most common eating disorders, anorexia nervosa and bulimia nervosa, are characterized by aberrant eating patterns and disturbances in body image. Treatment involves combining individual, behavioural, group, and family therapies, possibly with medications. Studies have found that medication, chiefly antidepressants, could be of help in bulimia nervosa but the evidence is weaker for use in anorexia nervosa. Repetitive transcranial magnetic stimulation (rTMS) is a non-invasive technique that briefly stimulates or depresses cortical areas within the brain. It has been used in the treatment of various psychiatric disorders, especially major depression, which is a condition that patients with eating disorders often experience as a significant comorbidity. Given that both disorders may share a common pathogenesis, this report proposes that rTMS may represent an alternative strategy for the treatment of eating disorders. Other evidence that supports this notion comes from animal studies that show that rTMS can change feeding behaviours and central neurotransmitters related to the regulation of eating behaviours. Further investigation into the dose, duration and type of rTMS stimulus is needed to verify the efficacy of this intervention in eating disorders. PMID:16005573

Tsai, Shih-Jen

2005-01-01

114

Repetitive transcranial magnetic stimulation transiently reduces punding in Parkinson's disease: a preliminary study.  

PubMed

Amongst the impulse-control disorders (ICDs) associated with dopamine-replacement therapy in patients with Parkinson's disease (PD) is a repetitive, complex, stereotyped behaviour called punding. Disruption of the reciprocal loops between the striatum and structures in the prefrontal cortex (PFC) following dopamine depletion may predispose patients with PD to these behavioural disorders. The purpose of the present study was to assess the effects of repetitive transcranial magnetic stimulation (rTMS) over the dorsolateral PFC (DLPFC) on punding in PD. We used low-frequency (LF) rTMS in four PD patients presenting with punding. Punding was transiently reversed by LF-rTMS over the DLPFC without enhancing motor impairment. The effect was more sustained after right DLPFC rTMS. Therefore, LF-rTMS produced a transient beneficial effect in PD patients with punding, similar to that reported in PD patients with levodopa-induced dyskinesias. rTMS might have therapeutic potential for the treatment of punding and perhaps other ICDs in PD. PMID:24132699

Nardone, Raffaele; De Blasi, Pierpaolo; Höller, Yvonne; Christova, Monica; Tezzon, Frediano; Trinka, Eugen; Brigo, Francesco

2014-01-01

115

Effect of cerebellar transcranial magnetic stimulation on soleus Ia presynaptic and reciprocal inhibition.  

PubMed

Previously, we reported that cerebellar transcranial magnetic stimulation (C-TMS) facilitates spinal motoneuronal excitability in resting humans. In this study, we aimed to characterize the descending pathway that is responsible for the C-TMS-associated cerebellar spinal facilitation. We evaluated the effect of C-TMS on ipsilateral soleus Ia presynaptic inhibition (PSI) and reciprocal inhibition (RI) because the vestibulospinal and reticulospinal tracts project from the cerebellum to mediate spinal motoneurons via interneurons associated with PSI. PSI and RI were measured with a soleus H-reflex test following operant conditioning using electrical stimulation of the common peroneal nerve. C-TMS was delivered before test tibial nerve stimulation with conditioning-test interstimulus intervals of 110?ms. C-TMS did not generate motor-evoked potentials, and it did not increase electromyography activity in the ipsilateral soleus muscle, indicating that C-TMS does not directly activate the corticospinal tract and motoneurons. However, C-TMS facilitated the ipsilateral soleus H-reflex and reduced the amount of soleus Ia PSI, but not RI. These findings indicate that C-TMS may facilitate the excitability of the spinal motoneuron pool via the vestibulospinal or reticulospinal tracts associated with PSI. Cerebellar spinal facilitation may be useful for assessing the functional connectivity of the cerebellum and vestibular nuclei or reticular formation. PMID:25569794

Matsugi, Akiyoshi; Mori, Nobuhiko; Uehara, Shintaro; Kamata, Noriyuki; Oku, Kosuke; Okada, Yohei; Kikuchi, Yutaka; Mukai, Kouichi; Nagano, Kiyoshi

2015-02-11

116

What have We Learned from “Perturbing” the Human Cortical Motor System with Transcranial Magnetic Stimulation?  

PubMed Central

The purpose of this paper is twofold. First, we will review different approaches that one can use with transcranial magnetic stimulation (TMS) to study both its effects on motor behavior and on neural connections in the human brain. Second, we will present evidence obtained in TMS-based studies showing that the dorsal premotor area (PMd), the ventral premotor area (PMv), the supplementary motor area (SMA), and the pre-supplementary motor area (pre-SMA) each have different roles to play in motor behavior. We highlight the importance of the PMd in response selection based on arbitrary cues and in the control of arm movements, the PMv in grasping and in the discrimination of bodily actions, the SMA in movement sequencing and in bimanual coordination, and the pre-SMA in cognitive control. We will also discuss ways in which TMS can be used to chart “true” cerebral reorganization in clinical populations and how TMS might be used as a therapeutic tool to facilitate motor recovery after stroke. We will end our review by discussing some of the methodological challenges and future directions for using this tool in basic and clinical neuroscience. PMID:21060721

Chouinard, Philippe A.; Paus, Tomáš

2010-01-01

117

Transcranial magnetic stimulation (TMS) of the supramarginal gyrus: a window to perception of upright.  

PubMed

Although the pull of gravity, primarily detected by the labyrinth, is the fundamental input for our sense of upright, vision and proprioception must also be integrated with vestibular information into a coherent perception of spatial orientation. Here, we used transcranial magnetic stimulation (TMS) to probe the role of the cortex at the temporal parietal junction (TPJ) of the right cerebral hemisphere in the perception of upright. We measured the perceived vertical orientation of a visual line; that is, the subjective visual vertical (SVV), after a short period of continuous theta burst stimulation (cTBS) with the head upright. cTBS over the posterior aspect of the supramarginal gyrus (SMGp) in 8 right-handed subjects consistently tilted the perception of upright when tested with the head tilted 20° to either shoulder (right: 3.6°, left: 2.7°). The tilt of SVV was always in the direction opposite to the head tilt. On the other hand, there was no significant tilt after sham stimulation or after cTBS of nearby areas. These findings suggest that a small area of cerebral cortex-SMGp-has a role in processing information from different sensory modalities into an accurate perception of upright. PMID:24084127

Kheradmand, Amir; Lasker, Adrian; Zee, David S

2015-03-01

118

Effects of repetitive transcranial magnetic stimulation on synaptic plasticity and apoptosis in vascular dementia rats.  

PubMed

This study aims to determine whether low-frequency repetitive transcranial magnetic stimulation (rTMS) protects pyramidal cells from apoptosis and promotes hippocampal synaptic plasticity in a vascular dementia (VaD) rat model. Following establishment of a VaD rat model using two-vessel occlusion (2VO), learning and memory were evaluated via the Morris Water Maze (MWM), hippocampal CA1 neuron ultrastructure was examined via electron microscopy, and hippocampal synaptic plasticity was assessed by long-term potentiation (LTP). Western blot was used to detect the expression of N-methyl-d-aspartic acid receptor 1 (NMDAR1), Bcl-2, and Bax. Compared with VaD group, rats treated with low-frequency rTMS had reduced-escape latencies, increased swimming time in the target quadrant (P<0.05), and significantly less synaptic structure damage. LTP at hippocampal CA3-CA1 synapses was enhanced (P<0.05). Low-frequency rTMS significantly up-regulated NMDAR1 and Bcl-2 expression and down-regulated Bax expression. Low-frequency rTMS improves learning and memory, protects the synapse, and increases synaptic plasticity in VaD model rats. Increased Bcl-2 expression and reduced Bax expression may be a novel protective mechanism of low-frequency rTMS treatment for VaD. PMID:25541037

Yang, Hui-Yun; Liu, Yang; Xie, Jia-Cun; Liu, Nan-Nan; Tian, Xin

2015-03-15

119

Responses of the human motor system to observing actions across species: A transcranial magnetic stimulation study.  

PubMed

Ample evidence suggests that the role of the mirror neuron system (MNS) in monkeys is to represent the meaning of actions. The MNS becomes active in monkeys during execution, observation, and auditory experience of meaningful, object-oriented actions, suggesting that these cells represent the same action based on a variety of cues. The present study sought to determine whether the human motor system, part of the putative human MNS, similarly represents and reflects the meaning of actions rather than simply the mechanics of the actions. To this end, transcranial magnetic stimulation (TMS) of primary motor cortex was used to generate motor-evoked potentials (MEPs) from muscles involved in grasping while participants viewed object-oriented grasping actions performed by either a human, an elephant, a rat, or a body-less robotic arm. The analysis of MEP amplitudes suggested that activity in primary motor cortex during action observation was greatest during observation of the grasping actions of the rat and elephant, and smallest for the human and robotic arm. Based on these data, we conclude that the human action observation system can represent actions executed by non-human animals and shows sensitivity to species-specific differences in action mechanics. PMID:25463135

White, Nicole C; Reid, Connor; Welsh, Timothy N

2014-10-22

120

Prospects for clinical applications of transcranial magnetic stimulation and real-time EEG in epilepsy.  

PubMed

Recent advances in methods for transcranial magnetic stimulation (TMS) enable its coupling to real-time EEG (TMS-EEG). Although TMS-EEG is applied largely in neurophysiology research, there are prospects for its use in clinical TMS practice, particularly in epilepsy where EEG is already in wide use, and where TMS is emerging as a diagnostic and therapeutic tool. In diagnostic applications, TMS-EEG may provide a useful measure of cortical excitability at baseline or after antiepileptic treatment. For therapeutic purposes, TMS-EEG may be of use in selection of appropriate TMS strength outside of the motor cortex where the threshold for cortical activation is more apparent with the aid of EEG. In other realistic clinical applications, TMS-EEG may be of use in real-time monitoring for epileptiform activity in vulnerable populations where TMS may trigger seizures, or as a component of a responsive neurostimulation setup in which TMS timing is determined by underlying EEG activity. Future trials and evolution of TMS-EEG methods are likely to provide answers as to the actual clinical value of TMS-EEG. PMID:19921417

Rotenberg, Alexander

2010-01-01

121

Repetitive transcranial magnetic stimulator with controllable pulse parameters (cTMS).  

PubMed

We describe a novel transcranial magnetic stimulation (TMS) device that uses a circuit topology incorporating two energy-storage capacitors and two insulated-gate bipolar transistors (IGBTs) to generate near-rectangular electric field E-field) pulses with adjustable number, polarity, duration, and amplitude of the pulse phases. This controllable-pulse-parameter TMS (cTMS) device can induce E-field pulses with phase widths of 5-200 µs and positive/negative phase amplitude ratio of 1-10. Compared to conventional monophasic and biphasic TMS, cTMS reduces energy dissipation by 78-82% and 55-57% and decreases coil heating by 15-33% and 31-41%, respectively. We demonstrate repetitive TMS (rTMS) trains of 3,000 pulses at frequencies up to 50 Hz with E-field pulse amplitude and width variability of less than 1.7% and 1%, respectively. The reduced power consumption and coil heating, and the flexible pulse parameter adjustment offered by cTMS could enhance existing TMS paradigms and could enable novel research and clinical applications with potentially enhanced potency. PMID:21095986

Peterchev, Angel V; Murphy, David L; Lisanby, Sarah H

2010-01-01

122

A study using transcranial magnetic stimulation to investigate motor mechanisms in psychomotor retardation in depression.  

PubMed

The pathophysiological basis of psychomotor retardation in depression is unclear. In this study, transcranial magnetic stimulation (TMS) was used to examine the functioning of the motor cortical system in 19 depressed patients and 10 healthy control subjects. Motor-evoked potentials were measured in the biceps brachii muscle during a series of tests with the muscle at rest and during voluntary elbow flexion contractions. Maximal voluntary force, as well as force and electromyographic responses to TMS were also measured during fatiguing maximal contractions. Depressed psychomotor-retarded subjects were less able to produce output from the motor cortex than non-psychomotor-retarded, depressed subjects and healthy controls during maximal exertion and fatigue. This finding was independent of depression severity. In contrast, responses to TMS elicited during relaxation or weak contractions did not differ between healthy and psychomotor-retarded subjects. Our study suggests that although the motor pathway from the motor cortex to the muscle is unimpaired, psychomotor retardation in depression is characterized by a reduced ability to drive the motor cortex. PMID:18447965

Loo, Colleen K; Sachdev, Perminder; Mitchell, Philip B; Gandevia, Simon C; Malhi, Gin S; Todd, Gabrielle; Taylor, Janet L

2008-11-01

123

Corticospinal facilitation during observation of graspable objects: a transcranial magnetic stimulation study.  

PubMed

In 1979, Gibson first advanced the idea that the sight of graspable objects automatically activates in the observer the repertoire of actions necessary to interact with them, even in the absence of any intention to act ("affordance effect"). The neurophysiological substrate of this effect was later identified in a class of bimodal neurons, the so-called "canonical" neurons, located within monkey premotor cortex. In humans, even if different behavioral studies supported the existence of affordance effect, neurophysiological investigations exploring its neural substrates showed contradictory results. Here, by means of Transcranial Magnetic Stimulation (TMS), we explored the time-course of the "affordance effect" elicited by the observation of everyday-life graspable objects on motor cortex of resting observers. We recorded motor evoked potentials (MEP) from three intrinsic hand muscles (two "synergic" for grasping, OP and FDI and one "neutral", ADM). We found that objects' vision determined an increased excitability at 120 milliseconds after their presentation. Moreover, this modulation was proved to be specific to the cortical representations of synergic muscles. From an evolutionary perspective, this timing perfectly fits with a fast recruitment of the motor system aimed at rapidly and accurately choosing the appropriate motor plans in a competitive environment filled with different opportunities. PMID:23145052

Franca, Michele; Turella, Luca; Canto, Rosario; Brunelli, Nicola; Allione, Luisa; Andreasi, Nico Golfré; Desantis, Marianna; Marzoli, Daniele; Fadiga, Luciano

2012-01-01

124

Differences between Han Chinese and Caucasians in transcranial magnetic stimulation parameters.  

PubMed

The study was conducted to investigate the difference between Han Chinese and Caucasians on various parameters measured from responses to transcranial magnetic brain stimulation (TMS). Sixteen subjects were studied in each group. A circular coil at the vertex was used for stimulation, whilst recording surface electromyograms from right first dorsal interosseous. In the passive state, motor-evoked potential (MEP) threshold, MEP recruitment, short-interval intracortical inhibition (SICI) and intracortical facilitation were measured. The MEP threshold, recruitment and silent period were also measured in the active state. Chinese subjects showed significantly higher passive thresholds (P < 0.005), less inhibition of the motor response (SICI, P < 0.0005) and a shorter silent period (P < 0.05). Differences in SICI appeared to be a consequence of the differences in passive threshold and were not seen when active threshold was used to determine the conditioning stimulus intensity. Differences in silent period may also reflect differences in cortical excitability rather than inhibitory processes, as they were not seen when the silent-period duration was expressed as a function of MEP size, rather than TMS intensity. There appears to be a significant difference in some TMS parameters between Han Chinese and Caucasian subjects. This may reflect an underlying difference in cortical excitability. PMID:24240390

Yi, Xiang; Fisher, Karen M; Lai, Ming; Mansoor, Kashif; Bicker, R; Baker, Stuart N

2014-02-01

125

Neural summation in human motor cortex by subthreshold transcranial magnetic stimulations.  

PubMed

Integration of diverse synaptic inputs is a basic neuronal operation that relies on many neurocomputational principles, one of which is neural summation. However, we lack empirical understanding of neuronal summation in the human brains in vivo. Here, we explored the effect of neural summation on the motor cortex using two subthreshold pulses of transcranial magnetic stimulation (TMS), each with intensities ranging from 60 to 95 % of the resting motor threshold (RMT) and interstimulus interval (ISI) varying from 1 to 25 ms. We found that two subthreshold TMS pulses can produce suprathreshold motor response when ISIs were less than 10 ms, most prominent at 1, 1.5 and 3 ms. This facilitatory, above-threshold response was evident when the intensity of the subthreshold pulses was above 80 % of RMT but was absent as the intensity was 70 % or below. Modeling of the summation data across intensity suggested that they followed an exponential function with excellent model fitting. Understanding the constraints for inducing summation of subthreshold stimulations to generate above-threshold response may have implications in modeling neural operations and potential clinical applications. PMID:25399245

Du, Xiaoming; Choa, Fow-Sen; Summerfelt, Ann; Tagamets, Malle A; Rowland, Laura M; Kochunov, Peter; Shepard, Paul; Hong, L Elliot

2015-02-01

126

Exploring facial emotion perception in schizophrenia using transcranial magnetic stimulation and spatial filtering.  

PubMed

Schizophrenia patients have difficulty extracting emotional information from facial expressions. Perception of facial emotion can be examined by systematically altering the spatial frequency of stimuli and suppressing visual processing with temporal precision using transcranial magnetic stimulation (TMS). In the present study, we compared 25 schizophrenia patients and 27 healthy controls using a facial emotion identification task. Spatial processing was examined by presenting facial photographs that contained either high (HSF), low (LSF), or broadband/unfiltered (BSF) spatial frequencies. Temporal processing was manipulated using a single-pulse TMS delivered to the visual cortex either before (forward masking) or after (backward masking) photograph presentation. Consistent with previous studies, schizophrenia patients performed significantly below controls across all three spatial frequencies. A spatial frequency by forward/backward masking interaction effect demonstrated reduced performance in the forward masking component in the BSF condition and a reversed performance pattern in the HSF condition, with no significant differences between forward and backward masking in the LSF condition. However, the group by spatial frequency interaction was not significant. These findings indicate that manipulating visual suppression of emotional information at the level of the primary visual cortex results in comparable effects on both groups. This suggests that patients' deficits in facial emotion identification are not explained by low-level processes in the retino-geniculo-striate projection, but may rather depend on deficits of affect perception occurring at later integrative processing stages. PMID:25106071

Rassovsky, Yuri; Lee, Junghee; Nori, Poorang; Wu, Allan D; Iacoboni, Marco; Breitmeyer, Bruno G; Hellemann, Gerhard; Green, Michael F

2014-11-01

127

Correlation Networks for Identifying Changes in Brain Connectivity during Epileptiform Discharges and Transcranial Magnetic Stimulation  

PubMed Central

The occurrence of epileptiform discharges (ED) in electroencephalographic (EEG) recordings of patients with epilepsy signifies a change in brain dynamics and particularly brain connectivity. Transcranial magnetic stimulation (TMS) has been recently acknowledged as a non-invasive brain stimulation technique that can be used in focal epilepsy for therapeutic purposes. In this case study, it is investigated whether simple time-domain connectivity measures, namely cross-correlation and partial cross-correlation, can detect alterations in the connectivity structure estimated from selected EEG channels before and during ED, as well as how this changes with the application of TMS. The correlation for each channel pair is computed on non-overlapping windows of 1 s duration forming weighted networks. Further, binary networks are derived by thresholding or statistical significance tests (parametric and randomization tests). The information for the binary networks is summarized by statistical network measures, such as the average degree and the average path length. Alterations of brain connectivity before, during and after ED with or without TMS are identified by statistical analysis of the network measures at each state. PMID:25025550

Siggiridou, Elsa; Kugiumtzis, Dimitris; Kimiskidis, Vasilios K.

2014-01-01

128

Induced Effects of Transcranial Magnetic Stimulation on the Autonomic Nervous System and the Cardiac Rhythm  

PubMed Central

Several standard protocols based on repetitive transcranial magnetic stimulation (rTMS) have been employed for treatment of a variety of neurological disorders. Despite their advantages in patients that are retractable to medication, there is a lack of knowledge about the effects of rTMS on the autonomic nervous system that controls the cardiovascular system. Current understanding suggests that the shape of the so-called QRS complex together with the size of the different segments and intervals between the PQRST deflections of the heart could predict the nature of the different arrhythmias and ailments affecting the heart. This preliminary study involving 10 normal subjects from 20 to 30 years of age demonstrated that rTMS can induce changes in the heart rhythm. The autonomic activity that controls the cardiac rhythm was indeed altered by an rTMS session targeting the motor cortex using intensity below the subject's motor threshold and lasting no more than 5 minutes. The rTMS activation resulted in a reduction of the RR intervals (cardioacceleration) in most cases. Most of these cases also showed significant changes in the Poincare plot descriptor SD2 (long-term variability), the area under the low frequency (LF) power spectrum density curve, and the low frequency to high frequency (LF/HF) ratio. The RR intervals changed significantly in specific instants of time during rTMS activation showing either heart rate acceleration or heart rate deceleration. PMID:25136660

Cabrera, Anastasio; Perez, Juan O.; de la Rua, Jesus; Rojas, Niovi; Zhou, Qi; Pinzon-Ardila, Alberto; Gonzalez-Arias, Sergio M.

2014-01-01

129

Probing feedforward and feedback contributions to awareness with visual masking and transcranial magnetic stimulation  

PubMed Central

A number of influential theories posit that visual awareness relies not only on the initial, stimulus-driven (i.e., feedforward) sweep of activation but also on recurrent feedback activity within and between brain regions. These theories of awareness draw heavily on data from masking paradigms in which visibility of one stimulus is reduced due to the presence of another stimulus. More recently transcranial magnetic stimulation (TMS) has been used to study the temporal dynamics of visual awareness. TMS over occipital cortex affects performance on visual tasks at distinct time points and in a manner that is comparable to visual masking. We draw parallels between these two methods and examine evidence for the neural mechanisms by which visual masking and TMS suppress stimulus visibility. Specifically, both methods have been proposed to affect feedforward as well as feedback signals when applied at distinct time windows relative to stimulus onset and as a result modify visual awareness. Most recent empirical evidence, moreover, suggests that while visual masking and TMS impact stimulus visibility comparably, the processes these methods affect may not be as similar as previously thought. In addition to reviewing both masking and TMS studies that examine feedforward and feedback processes in vision, we raise questions to guide future studies and further probe the necessary conditions for visual awareness. PMID:25374548

Tapia, Evelina; Beck, Diane M.

2014-01-01

130

[Computer modelling of electroconvulsive treatment and transcranial magnetic stimulation--an explanation of poor efficacy of the magnetic method].  

PubMed

With help of informatics technology it is possible to simulate various physiological processes in virtual models of biological structures. In a created realistic model of the human head we made some comparative investigations over physical phenomena accompanying the electroconvulsive treatment ECT and transcranial magnetic stimulation TMS--two methods with confirmed (ECT) or presumable (TMS) antidepressant efficacy. The present investigations are a continuation of the earlier conducted study in the simple spherical model of the head. Investigations confirmed, that magnetic stimulation TMS generates a considerably weaker current flow in the brain than it is present in electroconvulsive technique. Applying of such weak stimulation in modus,,at haphazard", i.e. on the brain area which does not need to be metabolically disturbed in this patient--cannot cause an antidepressant effect at all. The results of the investigations explain not only the safety of the magnetic method, but the weak effectiveness of this method. The authors propose some methods for improvement of TMS efficacy. PMID:21449167

Zyss, Tomasz; Krawczyk, Andrzej; Zieba, Andrzej; Dudek, Dominika; Hese, Robert T; Drzyma?a, Pawe?; Wiak, S?awomir; Sawicki, Bartosz; Starzy?ski, Jacek; Szmur?o, Robert; Wincenciak, Stanis?aw

2010-01-01

131

[Transcranial magnetic stimulation as an alternative to electroshock therapy in treatment resistant depressions. A literature review].  

PubMed

Transcranial magnet stimulation (TMS) is a low-risk method for direct and localised stimulation of the cerebral cortex. For several years it has played an important part in measurements of the central motor conduction time (magnetically evoked potentials/MEP). Further technical and methodological developments, such as high-frequency (rapid rate TMS/rTMS) or triggered stimulation have led to broad scientific application of this method. Electric convulsive therapy (ECT) has proved its value in the treatment of various psychiatric disorders, especially in pharmaco-resistant depression. The therapeutic mechanism is actually unclear. However, the generalised convulsive fit appears to be the precondition for the therapeutic effect. A disadvantage lies in the risk inherent in the necessary general anaesthesia and the possible side effects, such as transitory states of confusion and transient mnestic deficits. Bearing in mind the possibility that TMS could have the same effects as ECT due to stimulations below the convulsion threshold or to the direct or indirect stimulations of so-called disorder-specific key regions, several pilot studies and some controlled studies have been published during the past three years on its efficacy in depressive disorders. The results were reported on and critically evaluated. The results of this survey of the literature on the subject is that (r)TMS does not represent an alternative to ECT in the therapy of pharmaco-resistant depressions. Due to its slight and only transient antidepressive effect, (r)TMS is also, in our opinion, not suitable as so-called add-on therapy as a complement to antidepressant medication. PMID:9451566

Markwort, S; Cordes, P; Aldenhoff, J

1997-12-01

132

Testing a Neurobiological Model of Depersonalization Disorder Using Repetitive Transcranial Magnetic Stimulation?  

PubMed Central

Background Depersonalization disorder (DPD) includes changes in subjective experiencing of self, encompassing emotional numbing. Functional magnetic resonance imaging (fMRI) has pointed to ventrolateral prefrontal cortex (VLPFC) inhibition of insula as a neurocognitive correlate of the disorder. Objective We hypothesized that inhibition to right VLPFC using repetitive transcranial magnetic stimulation (rTMS) would lead to increased arousal and reduced symptoms. Methods Patients with medication-resistant DSM-IV DPD (N = 17) and controls (N = 20) were randomized to receive one session of right-sided rTMS to VLPFC or temporo-parietal junction (TPJ). 1Hz rTMS was guided using neuronavigation and delivered for 15 min. Co-primary outcomes were: (a) maximum skin conductance capacity, and (b) reduction in depersonalization symptoms (Cambridge Depersonalisation Scale (CDS) [state version]). Secondary outcomes included spontaneous fluctuations (SFs) and event-related skin conductance responses. Results In patients with DPD, rTMS to VLPFC led to increased electrodermal capacity, namely maximum skin conductance deflections. Patients but not controls also showed increased SFs post rTMS. Patients who had either VLPFC or TPJ rTMS showed a similar significant reduction in symptoms. Event-related electrodermal activity did not change. Conclusions A single session of right-sided rTMS to VLPFC (but not TPJ) significantly increased physiological arousal capacity supporting our model regarding the relevance of increased VLPFC activity to emotional numbing in DPD. rTMS to both sites led to reduced depersonalization scores but since this was independent of physiological arousal, this may be a non-specific effect. TMS is a potential therapeutic option for DPD; modulation of VLPFC, if replicated, is a plausible mechanism. PMID:24439959

Jay, Emma-Louise; Sierra, Mauricio; Van den Eynde, Frederique; Rothwell, John C.; David, Anthony S.

2014-01-01

133

Solving the Orientation Specific Constraints in Transcranial Magnetic Stimulation by Rotating Fields  

PubMed Central

Transcranial Magnetic Stimulation (TMS) is a promising technology for both neurology and psychiatry. Positive treatment outcome has been reported, for instance in double blind, multi-center studies on depression. Nonetheless, the application of TMS towards studying and treating brain disorders is still limited by inter-subject variability and lack of model systems accessible to TMS. The latter are required to obtain a deeper understanding of the biophysical foundations of TMS so that the stimulus protocol can be optimized for maximal brain response, while inter-subject variability hinders precise and reliable delivery of stimuli across subjects. Recent studies showed that both of these limitations are in part due to the angular sensitivity of TMS. Thus, a technique that would eradicate the need for precise angular orientation of the coil would improve both the inter-subject reliability of TMS and its effectiveness in model systems. We show here how rotation of the stimulating field relieves the angular sensitivity of TMS and provides improvements in both issues. Field rotation is attained by superposing the fields of two coils positioned orthogonal to each other and operated with a relative phase shift in time. Rotating field TMS (rfTMS) efficiently stimulates both cultured hippocampal networks and rat motor cortex, two neuronal systems that are notoriously difficult to excite magnetically. This opens the possibility of pharmacological and invasive TMS experiments in these model systems. Application of rfTMS to human subjects overcomes the orientation dependence of standard TMS. Thus, rfTMS yields optimal targeting of brain regions where correct orientation cannot be determined (e.g., via motor feedback) and will enable stimulation in brain regions where a preferred axonal orientation does not exist. PMID:24505266

Neef, Nicole E.; Agudelo-Toro, Andres; Rakhmilevitch, David; Paulus, Walter; Moses, Elisha

2014-01-01

134

How does transcranial magnetic stimulation modify neuronal activity in the brain? Implications for studies of cognition.  

PubMed

Transcranial magnetic stimulation (TMS) uses a magnetic field to "carry" a short lasting electrical current pulse into the brain where it stimulates neurones, particularly in superficial regions of cerebral cortex. TMS can interfere with cognitive functions in two ways. A high intensity TMS pulse causes a synchronised high frequency burst of discharge in a relatively large population of neurones that is terminated by a long lasting GABAergic inhibition. The combination of artificial synchronisation of activity followed by depression effectively disrupts perceptual, motor and cognitive processes in the human brain. This transient neurodisruption has been termed a "virtual lesion". Smaller intensities of stimulation produce less activity; in such cases, cognitive operations can probably continue but are disrupted because of the added noisy input from the TMS pulse. It is usually argued that if a TMS pulse affects performance, then the area stimulated must provide an essential contribution to behaviour being studied. However, there is one exception to this: the pulse could be applied to an area that is not involved in the task but which has projections to the critical site. Activation of outputs from the site of stimulation could potentially disrupt processing at the distant site, interfering with behaviour without having any involvement in the task. A final important feature of the response to TMS is "context dependency", which indicates that the response depends on how excitable the cortex is at the time the stimulus is applied: if many neurones are close to firing threshold then the more of them are recruited by the pulse than at rest. Many studies have noted this context-dependent modulation. However, it is often assumed that the excitability of an area has a simple relationship to activity in that area. We argue that this is not necessarily the case. Awareness of the problem may help resolve some apparent anomalies in the literature. PMID:19371866

Siebner, Hartwig R; Hartwigsen, Gesa; Kassuba, Tanja; Rothwell, John C

2009-10-01

135

Voltage-sensitive dye imaging of transcranial magnetic stimulation-induced intracortical dynamics  

PubMed Central

Transcranial magnetic stimulation (TMS) is widely used in clinical interventions and basic neuroscience. Additionally, it has become a powerful tool to drive plastic changes in neuronal networks. However, highly resolved recordings of the immediate TMS effects have remained scarce, because existing recording techniques are limited in spatial or temporal resolution or are interfered with by the strong TMS-induced electric field. To circumvent these constraints, we performed optical imaging with voltage-sensitive dye (VSD) in an animal experimental setting using anaesthetized cats. The dye signals reflect gradual changes in the cells' membrane potential across several square millimeters of cortical tissue, thus enabling direct visualization of TMS-induced neuronal population dynamics. After application of a single TMS pulse across visual cortex, brief focal activation was immediately followed by synchronous suppression of a large pool of neurons. With consecutive magnetic pulses (10 Hz), widespread activity within this “basin of suppression” increased stepwise to suprathreshold levels and spontaneous activity was enhanced. Visual stimulation after repetitive TMS revealed long-term potentiation of evoked activity. Furthermore, loss of the “deceleration–acceleration” notch during the rising phase of the response, as a signature of fast intracortical inhibition detectable with VSD imaging, indicated weakened inhibition as an important driving force of increasing cortical excitability. In summary, our data show that high-frequency TMS changes the balance between excitation and inhibition in favor of an excitatory cortical state. VSD imaging may thus be a promising technique to trace TMS-induced changes in excitability and resulting plastic processes across cortical maps with high spatial and temporal resolutions. PMID:25187557

Kozyrev, Vladislav; Eysel, Ulf T.; Jancke, Dirk

2014-01-01

136

Repetitive Transcranial Magnetic Stimulation for Clinical Applications in Neurological and Psychiatric Disorders: An Overview  

PubMed Central

Neurological and psychiatric disorders are characterized by several disabling symptoms for which effective, mechanism-based treatments remain elusive. Consequently, more advanced non-invasive therapeutic methods are required. A method that may modulate brain activity and be viable for use in clinical practice is repetitive transcranial magnetic stimulation (rTMS). It is a non-invasive procedure whereby a pulsed magnetic field stimulates electrical activity in the brain. Here, we focus on the basic foundation of rTMS, the main stimulation parametters, the factors that influence individual responses to rTMS and the experimental advances of rTMS that may become a viable clinical application to treat neurological and psychiatric disorders. The findings showed that rTMS can improve some symptoms associated with these conditions and might be useful for promoting cortical plasticity in patients with neurological and psychiatric disorders. However, these changes are transient and it is premature to propose these applications as realistic therapeutic options, even though the rTMS technique has been evidenced as a potential modulator of sensorimotor integration and neuroplasticity. Functional imaging of the region of interest could highlight the capacity of rTMS to bring about plastic changes of the cortical circuitry and hint at future novel clinical interventions. Thus, we recommend that further studies clearly determine the role of rTMS in the treatment of these conditions. Finally, we must remember that however exciting the neurobiological mechanisms might be, the clinical usefulness of rTMS will be determined by its ability to provide patients with neurological and psychiatric disorders with safe, long-lasting and substantial improvements in quality of life.

Machado, Sergio; Arias-Carrión, Oscar; Paes, Flávia; Vieira, Renata Teles; Caixeta, Leonardo; Novaes, Felipe; Marinho, Tamires; Almada, Leonardo Ferreira; Silva, Adriana Cardoso; Nardi, Antonio Egidio

2013-01-01

137

Magnetic Field Distribution and Application of a Transcranial Magnetic Stimulation for Drug Addicts  

Microsoft Academic Search

This article introduces the property of magnetic field distribution and application of TMS developed by BJUT. The TMS generates time-varying magnetic field to stimulate the particular area in human brain. To obtain the distribution of magnetic density, we carried out survey by utilizing a Gauss meter, from three aspects: the distribution of magnetic density in axial direction, in radial direction

Yu Chang; Miao Song; Bin Gao; Ningning Chen; Ling Li; Hongxing Wang

2009-01-01

138

Cortical excitability changes after high-frequency repetitive transcranial magnetic stimulation for central poststroke pain.  

PubMed

Central poststroke pain (CPSP) is one of the most refractory chronic pain syndromes. Repetitive transcranial magnetic stimulation (rTMS) of the primary motor cortex has been demonstrated to provide moderate pain relief for CPSP. However, the mechanism underlying the pain relief remains unclear. The objective of this study was to assess changes in cortical excitability in patients with intractable CPSP before and after rTMS of the primary motor cortex. Subjects were 21 patients with CPSP of the hand who underwent rTMS. The resting motor threshold, the amplitude of the motor evoked potential, duration of the cortical silent period, short interval intracortical inhibition, and intracortical facilitation were measured as parameters of cortical excitability before and after navigation-guided 5 Hz rTMS of the primary motor cortex corresponding to the painful hand. Pain reduction from rTMS was assessed with a visual analog scale. The same parameters were measured in both hemispheres of 8 healthy controls. Eight of 21 patients experienced ? 30% pain reduction after rTMS (responders). The resting motor threshold in the patients was higher than those in the controls at baseline (P=.035). Intracortical facilitation in the responders was lower than in the controls and the nonresponders at baseline (P=.035 and P=.019), and significantly increased after rTMS (P=.039). There were no significant differences or changes in the other parameters. Our findings suggest that restoration of abnormal cortical excitability might be one of the mechanisms underlying pain relief as a result of rTMS in CPSP. PMID:23707310

Hosomi, Koichi; Kishima, Haruhiko; Oshino, Satoru; Hirata, Masayuki; Tani, Naoki; Maruo, Tomoyuki; Yorifuji, Shiro; Yoshimine, Toshiki; Saitoh, Youichi

2013-08-01

139

Effects of repetitive transcranial magnetic stimulation on the somatosensory cortex during prism adaptation.  

PubMed

Although the behavioral characteristics and the neural correlates of prism adaptation processes have been studied extensively, the underlying mechanism is yet to be investigated. Recently, somatosensory suppression was heralded as a mechanism for the sensory re-alignment process accompanying the adaptation. Somatosensory suppression should facilitate the re-alignment process in the proprioceptive system. The shift in the proprioceptive system takes place mostly during a concurrent visual feedback (CVF) condition; during a terminal visual feedback (TVF) condition, the visual system experiences significant adaptation (visual shift), so somatosensory suppression should have minimal functional consequences under TVF. To test this hypothesis, a repetitive transcranial magnetic stimulation (rTMS) was applied to the primary somatosensory cortex as an artificial somatosensory suppression right after the reaching initiation in CVF and TVF conditions, and changes in adaptation were observed. Because somatosensory suppression is already in effect during CVF, rTMS would cause no significant changes. During TVF with rTMS, however, significantly different patterns of adaptation could be expected when compared to a sham rTMS condition. Young adults (N = 12) participated in 4 sessions (CVF/ TVF, real/sham rTMS); visual proprioceptive, and total shifts were measured. Movement time and curvature of the reaching movement were measured during the adaptation phase. Results showed that while the total shift was unchanged, the proprioceptive shift increased and the visual shift decreased in the TVF condition when rTMS was delivered. However, the total, proprioceptive, and visual shifts were not influenced by rTMS in the CVF condition. Suppression of proprioception induced by the rTMS could be one of the requisites for successful proprioceptive shift during prism adaptation. PMID:24897882

Yoon, Hee-Chul; Lee, Kyung-Hyun; Huh, Dong-Chan; Lee, Ji-Hang; Lee, Dong-Hyun

2014-04-01

140

Mechanisms of human motor cortex facilitation induced by subthreshold 5-Hz repetitive transcranial magnetic stimulation.  

PubMed

Our knowledge about the mechanisms of human motor cortex facilitation induced by repetitive transcranial magnetic stimulation (rTMS) is still incomplete. Here we used pharmacological conditioning with carbamazepine, dextrometorphan, lorazepam, and placebo to elucidate the type of plasticity underlying this facilitation, and to probe if mechanisms reminiscent of long-term potentiation are involved. Over the primary motor cortex of 10 healthy subjects, we applied biphasic rTMS pulses of effective posterior current direction in the brain. We used six blocks of 200 pulses at 5-Hz frequency and 90% active motor threshold intensity and controlled for corticospinal excitability changes using motor-evoked potential (MEP) amplitudes and latencies elicited by suprathreshold pulses before, in between, and after rTMS. Target muscle was the dominant abductor digiti minimi muscle; we coregistered the dominant extensor carpi radialis muscle. We found a lasting facilitation induced by this type of rTMS. The GABAergic medication lorazepam and to a lesser extent the ion channel blocker carbamazepine reduced the MEP facilitation after biphasic effective posteriorly oriented rTMS, whereas the N-methyl-d-aspartate receptor-antagonist dextrometorphan had no effect. Our main conclusion is that the mechanism of the facilitation induced by biphasic effective posterior rTMS is more likely posttetanic potentiation than long-term potentiation. Additional findings were prolonged MEP latency under carbamazepine, consistent with sodium channel blockade, and larger MEP amplitudes from extensor carpi radialis under lorazepam, suggesting GABAergic involvement in the center-surround balance of excitability. PMID:23536708

Sommer, Martin; Rummel, Milena; Norden, Christoph; Rothkegel, Holger; Lang, Nicolas; Paulus, Walter

2013-06-01

141

A neurophysiological insight into the potential link between transcranial magnetic stimulation, thalamocortical dysrhythmia and neuropsychiatric disorders.  

PubMed

Altered neural oscillations and their abnormal synchronization are crucial factors in the pathophysiology of several neuropsychiatric disorders. There is increasing evidence that the perturbation with an abnormal increase of spontaneous thalamocortical neural oscillations lead to a phenomenon termed Thalamocortical dysrhythmia (TCD) which underlies the symptomatology of a variety of neurological and psychiatric disorders including Parkinson's disease, schizophrenia, epilepsy, neuropathic pain, tinnitus, major depression and obsessive-compulsive disorder. In addition, repetitive transcranial magnetic stimulation (rTMS) is a non-invasive neurophysiological tool that has been shown to both induce a modulation of neural oscillations and alleviate a wide range of human neuropsychiatric pathologies. However, little is known about the precise electrophysiological mechanisms behind the therapeutic effect of rTMS and its potential to improve abnormal oscillations across diverse neuropsychiatric disorders. Here we show, using combined rTMS and surface electroencephalography (EEG), a short lasting frequency-dependent rTMS after-effect on thalamocortical rhythmic interplay of low-frequency oscillations in healthy humans at rest. In particular, high-frequency rTMS (10 Hz) induces a transient synchronised activity for delta (?) and theta (?) rhythms thus mimicking the pathological TCD-like oscillations. In contrast, rTMS 1 and 5 Hz have the opposite outcome of de-synchronising low-frequency brain rhythms. These results lead to a new neurophysiological insight of basic mechanisms underlying neurological and psychiatric disorders and a probable electrophysiological mechanism underlying the therapeutic effects of rTMS. Thus, we propose the use of rTMS and EEG as a platform to test possible treatments of TCD phenotypes by restoring proper neural oscillations across various neuropsychiatric disorders. PMID:23063603

Fuggetta, Giorgio; Noh, Nor Azila

2013-07-01

142

Therapeutic effects of repetitive transcranial magnetic stimulation in an animal model of Parkinson's disease.  

PubMed

Repetitive transcranial magnetic stimulation (rTMS) is used to treat neurological diseases such as stroke and Parkinson's disease (PD). Although rTMS has been used clinically, its underlying therapeutic mechanism remains unclear. The objective of the present study was to clarify the neuroprotective effect and therapeutic mechanism of rTMS in an animal model of PD. Adult Sprague-Dawley rats were unilaterally injected with 6-hydroxydopamine (6-OHDA) into the right striatum. Rats with PD were then treated with rTMS (circular coil, 10 Hz, 20 min/day) daily for 4 weeks. Behavioral assessments such as amphetamine-induced rotational test and treadmill locomotion test were performed, and the dopaminergic (DA) neurons of substantia nigra pas compacta (SNc) and striatum were histologically examined. Expression of neurotrophic/growth factors was also investigated by multiplex ELISA, western blotting analysis and immunohistochemistry 4 weeks after rTMS application. Among the results, the number of amphetamine-induced rotations was significantly lower in the rTMS group than in the control group at 4 weeks post-treatment. Treadmill locomotion was also significantly improved in the rTMS-treated rats. Tyrosine hydroxylase-positive DA neurons and DA fibers in rTMS group rats were greater than those in untreated group in both ipsilateral SNc and striatum, respectively. The expression levels of brain-derived neurotrophic factor, glial cell line-derived neurotrophic factor, platelet-derived growth factor, and vascular endothelial growth factor were elevated in both the 6-OHDA-injected hemisphere and the SNc of the rTMS-treated rats. In conclusion, rTMS treatment improved motor functions and survival of DA neurons, suggesting that the neuroprotective effect of rTMS treatment might be induced by upregulation of neurotrophic/growth factors in the PD animal model. PMID:23998987

Lee, Ji Yong; Kim, Sung Hoon; Ko, Ah-Ra; Lee, Jin Suk; Yu, Ji Hea; Seo, Jung Hwa; Cho, Byung Pil; Cho, Sung-Rae

2013-11-01

143

Repetitive transcranial magnetic stimulation protects hippocampal plasticity in an animal model of depression.  

PubMed

Despite its therapeutic success in treating mood-related disorders, little is known about the mechanism by which repetitive transcranial magnetic stimulation (rTMS) alters physiological responses of neurons. Using the forced swim test (FST) in rats as a model of depression, we tested the protective effect of rTMS on synaptic plasticity, specifically, on the induction of hippocampal long-term potentiation (LTP). Male Sprague-Dawley rats were subjected to FST to induce immobility, a behavioral symptom of depression. They were subsequently treated with one of the three conditions: rTMS (rTMS: 1000 stimuli at 10Hz), sham rTMS (SHAM: acoustic stimulation only), or an antidepressant drug, fluoxetine (FLX: 10mg/kg, i.p.) for 7 days. There was a significant difference in immobility time between rTMS and SHAM groups after 7 days of treatment, but not after a single day. Following the second swim test on day 7, they were anesthetized and LTP was induced in vivo in the perforant path-dentate gyrus synapses. Another group (NAIVE) that had received no prior treatment was used as a control for LTP. The SHAM or FLX group exhibited little signs of LTP induction. On the contrary, the rTMS and NAIVE group showed a significant increase in field excitatory postsynaptic potentials after LTP induction. These results show that rTMS has an antidepressant-like effect after a relatively short period of treatment, and this effect might be mediated by a cellular process that can potentially reverse the impaired synaptic efficacy caused by the forced swim procedure. PMID:16839687

Kim, Eun Joo; Kim, Woon Ryoung; Chi, Sang Eun; Lee, Kang Hee; Park, Eun Hye; Chae, Jeong-Ho; Park, Soon Kwon; Kim, Hyun Taek; Choi, June-Seek

2006-09-11

144

[Clinical applications of transcranial magnetic stimulation for the treatment of various neurological diseases].  

PubMed

Repetitive transcranial magnetic stimulation (rTMS) has been used as a potential therapeutic tool in various neurological and psychiatric diseases including depression, Parkinson disease, spinocerebellar degeneration, epilepsy, urinary incontinence, movement disorders, chronic pain, migraine and chronic tinnitus, etc. Several reports showed the therapeutic effects of rTMS as a treatment of depression and Parkinson disease (PD), whereas others found no significant effects. It is by now not yet fully understood whether rTMS has a therapeutic effect on those diseases. The controversy arises from the differences of the stimulation parameters and evaluation methods of the effects in those studies. The Japanese multi-center, double blinded, sham stimulation controlled trial in 85 patients with PD showed an efficacy in both the rTMS-treated and sham stimulated patients. This result does not prove the efficacy of the rTMS in PD; on the other hand, it does not rule out the efficacy. Possible mechanism of favorable effects of rTMS is related to increasing the release of dopamine in the mesolimbic and mesostriatal system. The other Japanese multi-center, double blinded, sham stimulation controlled trial in 99 patients with spinocerebellar degeneration revealed significant therapeutic effects of rTMS in 51 patients with SCA6. We studied the effects of rTMS on seizure susceptibility in rats which prevented the development of status epilepticus of pentylenetetrazol-induced convulsions. This finding suggests the possibility of therapeutic use of rTMS in epilepsy. Further studies should be performed aiming to reveal the optimal stimulation parameters, and are necessary to reveal the therapeutic role of the rTMS in neurological and psychiatric diseases. PMID:16447738

Tsuji, Sadatoshi

2005-11-01

145

Suppression of Motor Cortical Excitability in Anesthetized Rats by Low Frequency Repetitive Transcranial Magnetic Stimulation  

PubMed Central

Repetitive transcranial magnetic stimulation (rTMS) is a widely-used method for modulating cortical excitability in humans, by mechanisms thought to involve use-dependent synaptic plasticity. For example, when low frequency rTMS (LF rTMS) is applied over the motor cortex, in humans, it predictably leads to a suppression of the motor evoked potential (MEP), presumably reflecting long-term depression (LTD) – like mechanisms. Yet how closely such rTMS effects actually match LTD is unknown. We therefore sought to (1) reproduce cortico-spinal depression by LF rTMS in rats, (2) establish a reliable animal model for rTMS effects that may enable mechanistic studies, and (3) test whether LTD-like properties are evident in the rat LF rTMS setup. Lateralized MEPs were obtained from anesthetized Long-Evans rats. To test frequency-dependence of LF rTMS, rats underwent rTMS at one of three frequencies, 0.25, 0.5, or 1 Hz. We next tested the dependence of rTMS effects on N-methyl-D-aspartate glutamate receptor (NMDAR), by application of two NMDAR antagonists. We find that 1 Hz rTMS preferentially depresses unilateral MEP in rats, and that this LTD-like effect is blocked by NMDAR antagonists. These are the first electrophysiological data showing depression of cortical excitability following LF rTMS in rats, and the first to demonstrate dependence of this form of cortical plasticity on the NMDAR. We also note that our report is the first to show that the capacity for LTD-type cortical suppression by rTMS is present under barbiturate anesthesia, suggesting that future neuromodulatory rTMS applications under anesthesia may be considered. PMID:24646791

Muller, Paul A.; Dhamne, Sameer C.; Vahabzadeh-Hagh, Andrew M.; Pascual-Leone, Alvaro; Jensen, Frances E.; Rotenberg, Alexander

2014-01-01

146

Movement-generated afference paired with transcranial magnetic stimulation: an associative stimulation paradigm  

PubMed Central

Background A peripheral nerve stimulus can enhance or suppress the evoked response to transcranial magnetic stimulation (TMS) depending on the latency of the preceding peripheral nerve stimulation (PNS) pulse. Similarly, somatosensory afference from the passively moving limb can transiently alter corticomotor excitability, in a phase-dependent manner. The repeated association of PNS with TMS is known to modulate corticomotor excitability; however, it is unknown whether repeated passive-movement associative stimulation (MAS) has similar effects. Methods In a proof-of-principle study, using a cross-over design, seven healthy subjects received in separate sessions: (1) TMS (120% of the resting motor threshold-RMT, optimal site for Flexor Carpi Radialis) with muscle at rest; (2) TMS paired with cyclic passive movement during extension cyclic passive movement (400 pairs, 1 Hz), with the intervention order randomly assigned. Normality was tested using the Kolmogorov-Smirnov test, then compared to pre-intervention baseline using repeated measures ANOVA with a Dunnet multiple comparisons test. Results MAS led to a progressive and significant decrease in the motor evoked potential (MEP) amplitude over the intervention (R2?=?0.6665, P?

2014-01-01

147

Safety of Transcranial Magnetic Stimulation in Parkinson’s Disease: A Review of the Literature  

PubMed Central

Background Transcranial magnetic stimulation (TMS) has been used in both physiological studies and, more recently, the therapy of Parkinson’s Disease (PD). Prior TMS studies in healthy subjects and other patient populations demonstrate a slight risk of seizures and other adverse events. Our goal was to estimate these risks and document other safety concerns specific to PD patients. Methods We performed an English-Language literature search through PudMed to review all TMS studies involving PD patients. We documented any seizures or other adverse events associated with these studies. Crude risks were calculated per subject and per session of TMS. Results We identified 84 single pulse (spTMS) and/or paired pulse (ppTMS) TMS studies involving 1091 patients and 77 repetitive TMS (rTMS) studies involving 1137 patients. Risk of adverse events was low in all protocols. spTMS and ppTMS risk per patient for any adverse event was 0.0018 (95% CI: 0.0002 – 0.0066) per patient and no seizures were encountered. Risk of an adverse event from rTMS was 0.040 (95% CI: 0.029 – 0.053) per patient and no seizures were reported. Other adverse events included transient headaches, scalp pain, tinnitus, nausea, increase in pre-existing pain, and muscle jerks. Transient worsening of Parkinsonian symptoms was noted in one study involving rTMS of the supplementary motor area (SMA). Conclusion We conclude that current TMS and rTMS protocols do not pose significant risks to PD patients. We would recommend that TMS users in this population follow the most recent safety guidelines but do not warrant additional precautions. PMID:23473718

VonLoh, Matthew; Chen, Robert; Kluger, Benzi

2013-01-01

148

Controllable pulse parameter transcranial magnetic stimulator with enhanced circuit topology and pulse shaping  

NASA Astrophysics Data System (ADS)

Objective. This work aims at flexible and practical pulse parameter control in transcranial magnetic stimulation (TMS), which is currently very limited in commercial devices. Approach. We present a third generation controllable pulse parameter device (cTMS3) that uses a novel circuit topology with two energy-storage capacitors. It incorporates several implementation and functionality advantages over conventional TMS devices and other devices with advanced pulse shape control. cTMS3 generates lower internal voltage differences and is implemented with transistors with a lower voltage rating than prior cTMS devices. Main results. cTMS3 provides more flexible pulse shaping since the circuit topology allows four coil-voltage levels during a pulse, including approximately zero voltage. The near-zero coil voltage enables snubbing of the ringing at the end of the pulse without the need for a separate active snubber circuit. cTMS3 can generate powerful rapid pulse sequences (\\lt 10 ms inter pulse interval) by increasing the width of each subsequent pulse and utilizing the large capacitor energy storage, allowing the implementation of paradigms such as paired-pulse and quadripulse TMS with a single pulse generation circuit. cTMS3 can also generate theta (50 Hz) burst stimulation with predominantly unidirectional electric field pulses. The cTMS3 device functionality and output strength are illustrated with electrical output measurements as well as a study of the effect of pulse width and polarity on the active motor threshold in ten healthy volunteers. Significance. The cTMS3 features could extend the utility of TMS as a research, diagnostic, and therapeutic tool.

Peterchev, Angel V.; D?Ostilio, Kevin; Rothwell, John C.; Murphy, David L.

2014-10-01

149

Uncertainty Quantification in Transcranial Magnetic Stimulation via High-Dimensional Model Representation.  

PubMed

A computational framework for uncertainty quantification in transcranial magnetic stimulation (TMS) is presented. The framework leverages high-dimensional model representations (HDMRs), which approximate observables (i.e., quantities of interest such as electric (E) fields induced inside targeted cortical regions) via series of iteratively constructed component functions involving only the most significant random variables (i.e., parameters that characterize the uncertainty in a TMS setup such as the position and orientation of TMS coils, as well as the size, shape, and conductivity of the head tissue). The component functions of HDMR expansions are approximated via a multielement probabilistic collocation (ME-PC) method. While approximating each component function, a quasi-static finite-difference simulator is used to compute observables at integration/collocation points dictated by the ME-PC method. The proposed framework requires far fewer simulations than traditional Monte Carlo methods for providing highly accurate statistical information (e.g., the mean and standard deviation) about the observables. The efficiency and accuracy of the proposed framework are demonstrated via its application to the statistical characterization of E-fields generated by TMS inside cortical regions of an MRI-derived realistic head model. Numerical results show that while uncertainties in tissue conductivities have negligible effects on TMS operation, variations in coil position/orientation and brain size significantly affect the induced E-fields. Our numerical results have several implications for the use of TMS during depression therapy: 1) uncertainty in the coil position and orientation may reduce the response rates of patients; 2) practitioners should favor targets on the crest of a gyrus to obtain maximal stimulation; and 3) an increasing scalp-to-cortex distance reduces the magnitude of E-fields on the surface and inside the cortex. PMID:25203980

Gomez, Luis J; Yucel, Abdulkadir C; Hernandez-Garcia, Luis; Taylor, Stephan F; Michielssen, Eric

2015-01-01

150

Volitional muscle activity paired with transcranial magnetic stimulation increases corticospinal excitability  

PubMed Central

Studies of activity-dependent stimulation in non-human primates suggest that pairing each instance of volitional muscle activity with immediate intracortical stimulation causes long-term-potentiation-like effects. This technique holds promise for clinical rehabilitation, yet few investigators have tested activity-dependent stimulation in human subjects. In addition, no one has studied activity-dependent stimulation on the cortical representation for two separate target muscles in human subjects. We hypothesized that 40 min of transcranial magnetic stimulation (TMS) triggered from ballistic muscle activity at a mean repetition rate of 1 Hz would cause greater increases in corticospinal excitability than TMS-cued muscle activity, and that these changes would be specific to the muscle of study. Ten healthy human subjects participated in 4 separate sessions in this crossover study: (1) visually cued volitional activation of the abductor pollicis brevis (APB) muscle triggering TMS (APB-Triggered TMS), (2) volitional activation of APB in response to TMS delivered from a recording of the prior APB-Triggered TMS session (TMS-Cued APB), (3) visually cued volitional activation of the extensor digitorum (ED) triggering TMS (ED-Triggered TMS), and (4) volitional activation of ED in response to TMS delivered from a recording of the prior ED-Triggered TMS session (TMS-Cued ED). Contrary to our hypothesis, we discovered evidence of increased corticospinal excitability for all conditions as measured by change in area of the motor evoked potential. We conclude that single TMS pulses paired either before or after muscle activity may increase corticospinal excitability and that further studies are needed to clarify the optimal time window for inducing neural plasticity with activity-dependent stimulation. These findings will inform the design of future activity-dependent stimulation protocols for clinical rehabilitation. PMID:25628525

Edwardson, Matthew A.; Avery, David H.; Fetz, Eberhard E.

2015-01-01

151

Cholinergic dysfunction and amnesia in patients with Wernicke-Korsakoff syndrome: a transcranial magnetic stimulation study.  

PubMed

The specific neurochemical substrate underlying the amnesia in patients with Wernicke-Korsakoff syndrome (WKS) is still poorly defined. Memory impairment has been linked to dysfunction of neurons in the cholinergic system. A transcranial magnetic stimulation (TMS) protocol, the short latency afferent inhibition (SAI), may give direct information about the function of some cholinergic pathways in the human motor cortex. In the present study, we measured SAI in eight alcoholics with WKS and compared the data with those from a group of age-matched healthy individuals; furthermore, we correlated the individual SAI values of the WKS patients with memory and other cognitive functions. Mean SAI was significantly reduced in WKS patients when compared with the controls. SAI was increased after administration of a single dose of donezepil in a subgroup of four patients. The low score obtained in the Rey Complex Figure delayed recall test, the Digit Span subtest of the Wechsler Adult Intelligence Scale-Revised (WAIS-R) and the Corsi's Block Span subtest of the WAIS-R documented a severe impairment in the anterograde memory and short-term memory. None of the correlations between SAI values and these neuropsychological tests reached significance. We provide physiological evidence of cholinergic involvement in WKS. However, this putative marker of central cholinergic activity did not significantly correlate with the memory deficit in our patients. These findings suggest that the cholinergic dysfunction does not account for the memory disorder and that damage to the cholinergic system is not sufficient to cause a persisting amnesic syndrome in WKS. PMID:19960210

Nardone, Raffaele; Bergmann, Jürgen; De Blasi, Pierpaolo; Kronbichler, Martin; Kraus, Jörg; Caleri, Francesca; Tezzon, Frediano; Ladurner, Gunther; Golaszewski, Stefan

2010-03-01

152

Interaction between vestibulo-spinal and corticospinal systems: a combined caloric and transcranial magnetic stimulation study.  

PubMed

We investigated the interaction between vestibular and corticospinal stimuli in 8 healthy volunteers. Vestibular stimulation was induced with unilateral ear caloric irrigation (30°C) with subjects supine. Single transcranial magnetic stimulation (TMS) pulses were delivered (double-cone coil, intensities 60-75% maximal output) every 10-20 s during vestibular activation and during baseline. Bilateral surface electromyography (EMG) from splenius capitis, sternocleidomastoid (SCM), obliquus externus abdominis, vastus lateralis, biceps femoris (BF), tibialis anterior and peroneus longus was obtained. During whole-body maximal rotatory voluntary isometric contraction (MRVC), only SCM and BF displayed EMG activation/inhibition patterns indicating axial rotatory action. TMS-induced motor evoked potentials (MEPs) after caloric irrigation revealed that only SCM showed consistent vestibular-mediated excitation/inhibition responses, i.e. an increase in MEP area contralateral to the irrigation and a decrease in MEP area ipsilaterally (+12.7 and -6.3% of the MRVC, respectively). A putative head turn induced by this SCM activity pattern would be in the same direction of the slow-phase eye movement. EMG in the 100 ms preceding TMS showed muscle tone values of approximately 10% of MRVC. After caloric irrigation, these values increased by ca. 2% for all muscles bilaterally and hence cannot explain the direction-specific SCM MEP changes. Thus, SCM MEPs show caloric-induced amplitude modulation indicating that SCM is under both horizontal semicircular canal and corticospinal control. This vestibular modulation of corticospinal SCM control likely occurs at cortical levels. The direction of the MEP modulation indicates a directional coupling between vestibularly induced head and eye movements. PMID:21805198

Guzman-Lopez, J; Buisson, Y; Strutton, P H; Bronstein, A M

2011-09-01

153

Modifying the cortical processing for motor preparation by repetitive transcranial magnetic stimulation.  

PubMed

To investigate the effects of repetitive transcranial magnetic stimulation (rTMS) on the central processing of motor preparation, we had subjects perform a precued-choice reaction time (RT) task. They had to press one of two buttons as quickly as possible after a go signal specifying both the hand to be used and the button to press. A precue preceding this signal conveyed full, partial, or no advance information (hand and/or button), such that RT shortened with increasing amount of information. We applied 1200 to 2400 pulses of 1-Hz rTMS over various cortical areas and compared the subjects' performances at various times before and after this intervention. rTMS delayed RT at two distinct phases after stimulation, one within 10 min and another with a peak at 20 to 30 min and lasting for 60 to 90 min, with no significant effects on error rates or movement time. The effect was significantly larger on left- than on right-hand responses. RT was prominently delayed over the premotor and motor cortices with similar effects across different conditions of advance information, suggesting that preparatory processes relatively close to the formation of motor output were influenced by rTMS. In contrast, the effect of rTMS over the supplementary motor area and the anterior parietal cortex varied with the amount of advance information, indicating specific roles played by these areas in integrating target and effector information. The primary motor area, especially of the left hemisphere, may take over this processing, implementing motor output based on the information processed in other areas. PMID:17714016

Terao, Yasuo; Furubayashi, Toshiaki; Okabe, Shingo; Mochizuki, Hitoshi; Arai, Noritoshi; Kobayashi, Shunsuke; Ugawa, Yoshikazu

2007-09-01

154

Age-related changes in motor cortical representation and interhemispheric interactions: a transcranial magnetic stimulation study.  

PubMed

To better understand the physiological mechanisms responsible for the differential motor cortex functioning in aging, we used transcranial magnetic stimulation to investigate interhemispheric interactions and cortical representation of hand muscles in the early phase of physiological aging, correlating these data with participants' motor abilities. Right-handed healthy subjects were divided into a younger group (n?=?15, mean age 25.4?±?1.9?years old) and an older group (n?=?16, mean age 61.1?±?5.1?years old). Activity of the bilateral abductor pollicis brevis (APB) and abductor digiti minimi (ADM) was recorded. Ipsilateral silent period (ISP) was measured in both APBs. Cortical maps of APB and ADM were measured bilaterally. Mirror movements (MM) were recorded during thumb abductions. Motor abilities were tested using Nine Hole Peg Test, finger tapping, and grip strength. ISP was reduced in the older group on both sides, in terms of duration (p?=?0.025), onset (p?=?0.029), and area (p?=?0.008). Resting motor threshold did not differ between groups. APB and ADM maps were symmetrical in the younger group, but were reduced on the right compared to the left hemisphere in the older group (p?=?0.008). The APB map of the right hemisphere was reduced in the older group compared to the younger (p?=?0.021). Older subjects showed higher frequency of MM and worse motor abilities (p?

Coppi, Elisabetta; Houdayer, Elise; Chieffo, Raffaella; Spagnolo, Francesca; Inuggi, Alberto; Straffi, Laura; Comi, Giancarlo; Leocani, Letizia

2014-01-01

155

Transcranial magnetic stimulation-induced global propagation of transient phase resetting associated with directional information flow  

PubMed Central

Electroencephalogram (EEG) phase synchronization analyses can reveal large-scale communication between distant brain areas. However, it is not possible to identify the directional information flow between distant areas using conventional phase synchronization analyses. In the present study, we applied transcranial magnetic stimulation (TMS) to the occipital area in subjects who were resting with their eyes closed, and analyzed the spatial propagation of transient TMS-induced phase resetting by using the transfer entropy (TE), to quantify the causal and directional flow of information. The time-frequency EEG analysis indicated that the theta (5 Hz) phase locking factor (PLF) reached its highest value at the distant area (the motor area in this study), with a time lag that followed the peak of the transient PLF enhancements of the TMS-targeted area at the TMS onset. Phase-preservation index (PPI) analyses demonstrated significant phase resetting at the TMS-targeted area and distant area. Moreover, the TE from the TMS-targeted area to the distant area increased clearly during the delay that followed TMS onset. Interestingly, the time lags were almost coincident between the PLF and TE results (152 vs. 165 ms), which provides strong evidence that the emergence of the delayed PLF reflects the causal information flow. Such tendencies were observed only in the higher-intensity TMS condition, and not in the lower-intensity or sham TMS conditions. Thus, TMS may manipulate large-scale causal relationships between brain areas in an intensity-dependent manner. We demonstrated that single-pulse TMS modulated global phase dynamics and directional information flow among synchronized brain networks. Therefore, our results suggest that single-pulse TMS can manipulate both incoming and outgoing information in the TMS-targeted area associated with functional changes. PMID:24723875

Kawasaki, Masahiro; Uno, Yutaka; Mori, Jumpei; Kobata, Kenji; Kitajo, Keiichi

2014-01-01

156

Conditioning effect of transcranial magnetic stimulation evoking motor-evoked potential on V-wave response.  

PubMed

The aim of this study was to examine the collision responsible for the volitional V-wave evoked by supramaximal electrical stimulation of the motor nerve during voluntary contraction. V-wave was conditioned by transcranial magnetic stimulation (TMS) over the motor cortex at several inter-stimuli intervals (ISI) during weak voluntary plantar flexions (n = 10) and at rest for flexor carpi radialis muscle (FCR; n = 6). Conditioning stimulations were induced by TMS with intensity eliciting maximal motor-evoked potential (MEPmax). ISIs used were ranging from -20 to +20 msec depending on muscles tested. The results showed that, for triceps surae muscles, conditioning TMS increased the V-wave amplitude (~ +250%) and the associated mechanical response (~ +30%) during weak voluntary plantar flexion (10% of the maximal voluntary contraction -MVC) for ISIs ranging from +6 to +18 msec. Similar effect was observed at rest for the FCR with ISI ranging from +6 to +12 msec. When the level of force was increased from 10 to 50% MVC or the conditioning TMS intensity was reduced to elicit responses of 50% of MEPmax, a significant decrease in the conditioned V-wave amplitude was observed for the triceps surae muscles, linearly correlated to the changes in MEP amplitude. The slope of this correlation, as well as the electro-mechanical efficiency, was closed to the identity line, indicating that V-wave impact at muscle level seems to be similar to the impact of cortical stimulation. All these results suggest that change in V-wave amplitude is a great index to reflect changes in cortical neural drive addressed to spinal motoneurons. PMID:25501438

Grosprêtre, Sidney; Martin, Alain

2014-12-01

157

Alterations in human motor cortex during dual motor task by transcranial magnetic stimulation study.  

PubMed

The aim of this study was to determine how and whether changes in the primary motor cortex (M1) are affected by dual motor task. We further investigated how dual motor task is dependent on task properties measured using transcranial magnetic stimulation (TMS). TMS delivered to left M1 during the dual motor task and motor-evoked potential (MEP) were simultaneously evoked in the right FDI, thenar, FCR and ECR muscles. In experiment 1, subjects were asked to simultaneously walk on a treadmill and perform finger prehension. The gait conditions were employed 30, 50 and 80% of maximum walking speed (gait 30%, gait 50% and gait 80%). Conditions for finger prehension while following the visual tracking task varied with force outputs of 5 and 25% of maximum voluntary contraction (MVC). In experiment 2, the subjects were asked to perform optimal walking synchronized with the finger prehension task with an optimal walking rhythm (2-Hz dual motor task), as well as optimal walking desynchronized with the finger prehension task (0.7-Hz dual motor task). In experiment 1, MEPs were markedly decreased under the gait 50% condition compared with those under the gait 30 and 80% conditions at 5% MVC. In experiment 2, MEPs were markedly decreased with the 2-Hz dual motor task compared with those with the 0.7-Hz dual motor task. Our results suggest that the excitability changes in M1 during the dual motor task were dependent on changes in the gait speed, precision of prehension task and temporal movement. PMID:21082314

Uehara, Kazumasa; Higashi, Toshio; Tanabe, Shigeo; Sugawara, Kenichi

2011-01-01

158

The Role of Pulse Shape in Motor Cortex Transcranial Magnetic Stimulation Using Full-Sine Stimuli  

PubMed Central

A full-sine (biphasic) pulse waveform is most commonly used for repetitive transcranial magnetic stimulation (TMS), but little is known about how variations in duration or amplitude of distinct pulse segments influence the effectiveness of a single TMS pulse to elicit a corticomotor response. Using a novel TMS device, we systematically varied the configuration of full-sine pulses to assess the impact of configuration changes on resting motor threshold (RMT) as measure of stimulation effectiveness with single-pulse TMS of the non-dominant motor hand area (M1). In young healthy volunteers, we (i) compared monophasic, half-sine, and full-sine pulses, (ii) applied two-segment pulses consisting of two identical half-sines, and (iii) manipulated amplitude, duration, and current direction of the first or second full-sine pulse half-segments. RMT was significantly higher using half-sine or monophasic pulses compared with full-sine. Pulses combining two half-sines of identical polarity and duration were also characterized by higher RMT than full-sine stimuli resulting. For full-sine stimuli, decreasing the amplitude of the half-segment inducing posterior-anterior oriented current in M1 resulted in considerably higher RMT, whereas varying the amplitude of the half-segment inducing anterior-posterior current had a smaller effect. These findings provide direct experimental evidence that the pulse segment inducing a posterior-anterior directed current in M1 contributes most to corticospinal pathway excitation. Preferential excitation of neuronal target cells in the posterior-anterior segment or targeting of different neuronal structures by the two half-segments can explain this result. Thus, our findings help understanding the mechanisms of neural stimulation by full-sine TMS. PMID:25514673

Delvendahl, Igor; Gattinger, Norbert; Berger, Thomas; Gleich, Bernhard; Siebner, Hartwig R.; Mall, Volker

2014-01-01

159

Evidence-based guidelines on the therapeutic use of repetitive transcranial magnetic stimulation (rTMS).  

PubMed

A group of European experts was commissioned to establish guidelines on the therapeutic use of repetitive transcranial magnetic stimulation (rTMS) from evidence published up until March 2014, regarding pain, movement disorders, stroke, amyotrophic lateral sclerosis, multiple sclerosis, epilepsy, consciousness disorders, tinnitus, depression, anxiety disorders, obsessive-compulsive disorder, schizophrenia, craving/addiction, and conversion. Despite unavoidable inhomogeneities, there is a sufficient body of evidence to accept with level A (definite efficacy) the analgesic effect of high-frequency (HF) rTMS of the primary motor cortex (M1) contralateral to the pain and the antidepressant effect of HF-rTMS of the left dorsolateral prefrontal cortex (DLPFC). A Level B recommendation (probable efficacy) is proposed for the antidepressant effect of low-frequency (LF) rTMS of the right DLPFC, HF-rTMS of the left DLPFC for the negative symptoms of schizophrenia, and LF-rTMS of contralesional M1 in chronic motor stroke. The effects of rTMS in a number of indications reach level C (possible efficacy), including LF-rTMS of the left temporoparietal cortex in tinnitus and auditory hallucinations. It remains to determine how to optimize rTMS protocols and techniques to give them relevance in routine clinical practice. In addition, professionals carrying out rTMS protocols should undergo rigorous training to ensure the quality of the technical realization, guarantee the proper care of patients, and maximize the chances of success. Under these conditions, the therapeutic use of rTMS should be able to develop in the coming years. PMID:25034472

Lefaucheur, Jean-Pascal; André-Obadia, Nathalie; Antal, Andrea; Ayache, Samar S; Baeken, Chris; Benninger, David H; Cantello, Roberto M; Cincotta, Massimo; de Carvalho, Mamede; De Ridder, Dirk; Devanne, Hervé; Di Lazzaro, Vincenzo; Filipovi?, Saša R; Hummel, Friedhelm C; Jääskeläinen, Satu K; Kimiskidis, Vasilios K; Koch, Giacomo; Langguth, Berthold; Nyffeler, Thomas; Oliviero, Antonio; Padberg, Frank; Poulet, Emmanuel; Rossi, Simone; Rossini, Paolo Maria; Rothwell, John C; Schönfeldt-Lecuona, Carlos; Siebner, Hartwig R; Slotema, Christina W; Stagg, Charlotte J; Valls-Sole, Josep; Ziemann, Ulf; Paulus, Walter; Garcia-Larrea, Luis

2014-11-01

160

Enhancement of single motor unit inhibitory responses to transcranial magnetic stimulation in amyotrophic lateral sclerosis.  

PubMed

In healthy human subjects, transcranial magnetic stimulation (TMS) applied to the motor cortex induces concurrent inhibitory and excitatory effects on motoneurone activity. In amyotrophic lateral sclerosis (ALS), a neurodegenerative disease affecting both cortical and spinal motor neurons, paired-pulse studies based on electromyographic (EMG) recording have revealed a decrease in TMS-induced inhibition. This suggested that inhibition loss may promote excito-toxicity in this disease. Against this hypothesis, an abnormally high incidence of inhibitory responses to TMS has been observed in the peristimulus time histograms (PSTHs) in ALS single motor unit studies. The disappearance of cortico-motoneuronal excitatory inputs might, however, have facilitated the detection of single motor unit inhibitory responses in the PSTHs. This question was addressed here using a new approach, where the strength of the excitatory and inhibitory effects of TMS on motoneurone activity was assessed from the duration of inter-spike intervals (ISIs). This analysis was conducted on single motor unit (MU), tested on healthy subjects and patients with ALS or Kennedy's disease (KD), a motor neuron disease which unlike ALS, spares the cortico-spinal pathway. MUs tested on KD patients behaved like those of healthy subjects unlike those tested on ALS patients. The present data reveal that in ALS, the TMS-induced inhibitory effects are truly enhanced during voluntary contractions and not reduced, as observed in paired-pulse TMS studies under resting conditions. The possible contribution of inhibitory loss to the physiopathology of ALS therefore needs to be reconsidered. The present data do not support the idea that inhibition loss may underlie excito-toxicity in ALS. PMID:18496679

Schmied, Annie; Attarian, Shahram

2008-08-01

161

Modulation of corticospinal excitability by transcranial magnetic stimulation in children and adolescents with autism spectrum disorder  

PubMed Central

The developmental pathophysiology of autism spectrum disorders (ASD) is currently not fully understood. However, multiple lines of evidence suggest that the behavioral phenotype may result from dysfunctional inhibitory control over excitatory synaptic plasticity. Consistent with this claim, previous studies indicate that adults with Asperger’s Syndrome show an abnormally extended modulation of corticospinal excitability following a train of repetitive transcranial magnetic stimulation (rTMS). As ASD is a developmental disorder, the current study aimed to explore the effect of development on the duration of modulation of corticospinal excitability in children and adolescents with ASD. Additionally, as the application of rTMS to the understanding and treatment of pediatric neurological and psychiatric disorders is an emerging field, this study further sought to provide evidence for the safety and tolerability of rTMS in children and adolescents with ASD. Corticospinal excitability was measured by applying single pulses of TMS to the primary motor cortex both before and following a 40 s train of continuous theta burst stimulation. 19 high-functioning males ages 9–18 with ASD participated in this study. Results from this study reveal a positive linear relationship between age and duration of modulation of rTMS after-effects. Specifically we found that the older participants had a longer lasting response. Furthermore, though the specific protocol employed typically suppresses corticospinal excitability in adults, more than one third of our sample had a paradoxical facilitatory response to the stimulation. Results support the safety and tolerability of rTMS in pediatric clinical populations. Data also support published theories implicating aberrant plasticity and GABAergic dysfunction in this population. PMID:25165441

Oberman, Lindsay M.; Pascual-Leone, Alvaro; Rotenberg, Alexander

2014-01-01

162

Age-Related Changes in Motor Cortical Representation and Interhemispheric Interactions: A Transcranial Magnetic Stimulation Study  

PubMed Central

To better understand the physiological mechanisms responsible for the differential motor cortex functioning in aging, we used transcranial magnetic stimulation to investigate interhemispheric interactions and cortical representation of hand muscles in the early phase of physiological aging, correlating these data with participants’ motor abilities. Right-handed healthy subjects were divided into a younger group (n?=?15, mean age 25.4?±?1.9?years old) and an older group (n?=?16, mean age 61.1?±?5.1?years old). Activity of the bilateral abductor pollicis brevis (APB) and abductor digiti minimi (ADM) was recorded. Ipsilateral silent period (ISP) was measured in both APBs. Cortical maps of APB and ADM were measured bilaterally. Mirror movements (MM) were recorded during thumb abductions. Motor abilities were tested using Nine Hole Peg Test, finger tapping, and grip strength. ISP was reduced in the older group on both sides, in terms of duration (p?=?0.025), onset (p?=?0.029), and area (p?=?0.008). Resting motor threshold did not differ between groups. APB and ADM maps were symmetrical in the younger group, but were reduced on the right compared to the left hemisphere in the older group (p?=?0.008). The APB map of the right hemisphere was reduced in the older group compared to the younger (p?=?0.021). Older subjects showed higher frequency of MM and worse motor abilities (p?

Coppi, Elisabetta; Houdayer, Elise; Chieffo, Raffaella; Spagnolo, Francesca; Inuggi, Alberto; Straffi, Laura; Comi, Giancarlo; Leocani, Letizia

2014-01-01

163

Perfusion MRI Indexes Variability in the Functional Brain Effects of Theta-Burst Transcranial Magnetic Stimulation  

PubMed Central

Transcranial Magnetic Stimulation (TMS) is an important tool for testing causal relationships in cognitive neuroscience research. However, the efficacy of TMS can be variable across individuals and difficult to measure. This variability is especially a challenge when TMS is applied to regions without well-characterized behavioral effects, such as in studies using TMS on multi-modal areas in intrinsic networks. Here, we examined whether perfusion fMRI recordings of Cerebral Blood Flow (CBF), a quantitative measure sensitive to slow functional changes, reliably index variability in the effects of stimulation. Twenty-seven participants each completed four combined TMS-fMRI sessions during which both resting state Blood Oxygen Level Dependent (BOLD) and perfusion Arterial Spin Labeling (ASL) scans were recorded. In each session after the first baseline day, continuous theta-burst TMS (TBS) was applied to one of three locations: left dorsolateral prefrontal cortex (L dlPFC), left anterior insula/frontal operculum (L aI/fO), or left primary somatosensory cortex (L S1). The two frontal targets are components of intrinsic networks and L S1 was used as an experimental control. CBF changes were measured both before and after TMS on each day from a series of interleaved resting state and perfusion scans. Although TBS led to weak selective increases under the coil in CBF measurements across the group, individual subjects showed wide variability in their responses. TBS-induced changes in rCBF were related to TBS-induced changes in functional connectivity of the relevant intrinsic networks measured during separate resting-state BOLD scans. This relationship was selective: CBF and functional connectivity of these networks were not related before TBS or after TBS to the experimental control region (S1). Furthermore, subject groups with different directions of CBF change after TBS showed distinct modulations in the functional interactions of targeted networks. These results suggest that CBF is a marker of individual differences in the effects of TBS. PMID:24992641

Gratton, Caterina; Lee, Taraz G.; Nomura, Emi M.; D’Esposito, Mark

2014-01-01

164

Therapeutic effect of repetitive transcranial magnetic stimulation on motor function in Parkinson's disease patients.  

PubMed

Cortical excitability of the primary motor cortex is altered in patients with Parkinson's disease (PD). Therefore, modulation of cortical excitability by high frequency repetitive transcranial magnetic stimulation (rTMS) of the motor cortex might result in beneficial effects on motor functions in PD. The present study aims to evaluate the effect of rTMS of the motor cortex on motor functions in patients with PD. Thirty-six unmedicated PD patients were included consecutively in this study. The patients were assigned in a randomized pattern to one of two groups, one group receiving real-rTMS (suprathreshold 5-Hz, 2000 pulses once a day for 10 consecutive days) and the second group receiving sham-rTMS using closed envelopes. Total motor section of Unified Parkinson's Disease Rating Scale (UPDRS), walking speed, and self-assessment scale were performed for each patient before rTMS and after the first, fifth, 10th sessions, and then after 1 month. Evaluation of these measures was performed blindly without knowing the type of rTMS. anova for repeated measurements revealed a significant time effect for the total motor UPDRS, walking speed and self-assessment scale during the course of the study in the group of patients receiving real-rTMS (P = 0.0001, 0.001, and 0.002), while no significant changes were observed in the group receiving sham-rTMS except in self-assessment scale (P = 0.019). A 10-day course of real-rTMS resulted in statistically significant long-term improvement of the motor functions in comparison with the sham-rTMS. The rTMS could have a therapeutic role of for PD patients. PMID:12940840

Khedr, E M; Farweez, H M; Islam, H

2003-09-01

165

The dual nature of time preparation: neural activation and suppression revealed by transcranial magnetic stimulation of the motor cortex.  

PubMed

Single-pulse transcranial magnetic stimulations (TMSs) of the motor cortex (M1) were performed in order to decipher the neural mechanisms of time preparation. We varied the degree to which it was possible to prepare for the response signal in a choice reaction time (RT) task by employing either a short (500 ms) or a long (2500 ms) foreperiod in separate blocks of trials. Transcranial magnetic stimulations were delivered during these foreperiods in order to study modulations in both the size of the motor evoked potential (MEP) and the duration of the silent period (SP) in tonically activated response agonists. Motor evoked potential area and silent period duration were assumed to reflect, respectively, the excitability of the cortico-spinal pathway and the recruitment of inhibitory cortical interneurons. Shorter reaction times were observed with the shorter foreperiod, indicating that a better level of preparation was attained for the short foreperiod. Silent period duration decreased as time elapsed during the foreperiod and this decrement was more pronounced for the short foreperiod. This result suggests that time preparation is accompanied by a removal of intracortical inhibition, resulting in an activation. Motor evoked potential area decreased over the course of the short foreperiod, but not over the long foreperiod, revealing that time preparation involves the inhibition of the cortico-spinal pathway. We propose that cortico-spinal inhibition secures the development of cortical activation, preventing erroneous premature responding. PMID:17610596

Davranche, Karen; Tandonnet, Christophe; Burle, Boris; Meynier, Chloé; Vidal, Franck; Hasbroucq, Thierry

2007-06-01

166

Changes in visual cortex excitability in blind subjects as demonstrated by transcranial magnetic stimulation.  

PubMed

Any attempt to restore visual functions in blind subjects with pregeniculate lesions provokes the question of the extent to which deafferented visual cortex is still able to generate conscious visual experience. As a simple approach to assessing activation of the visual cortex, subjects can be asked to report conscious subjective light sensations (phosphenes) elicited by focal transcranial magnetic stimulation (TMS) over the occiput. We hypothesized that such induction of phosphenes can be used as an indicator of residual function of the visual cortex and studied 35 registered blind subjects after partial or complete long-term (>10 years) deafferentation of the visual cortex due to pregeniculate lesions. TMS was applied over the visual cortex in 10 blind subjects with some residual vision (visual acuity <20/400; Group 1), 15 blind subjects with very poor residual vision (only perception of movement or light; Group 2), 10 blind subjects without any residual vision (Group 3) and 10 healthy controls. A stimulation mapping procedure was performed on a 1 x 1 cm skull surface grid with 130 stimulation points overlying the occipital skull. We analysed the occurrence of phosphenes at each stimulation point with regard to frequency and location of phosphenes in the visual field. Previous experiments have shown that repetitive TMS reliably elicits brief flashes of white or coloured patches of light. Therefore, stimulation was performed with short trains of seven consecutive 15 Hz stimuli applied with an intensity of 1.3 times the motor threshold. Under such conditions, phosphenes occurred in 100% of subjects in Group 1, in 60% of Group 2 and in 20% of Group 3. Phosphene thresholds were normal, but the number of effective stimulation sites was significantly reduced in Groups 2 and 3. The results indicate that in blind subjects there is alteration in TMS-induced activation of the deafferented visual cortex or processes engaged in bringing the artificial cortex input to consciousness. The ability to elicit phosphenes is reduced in subjects with a high degree of visual deafferentation, especially in those without previous visual experience. PMID:11872606

Gothe, Janna; Brandt, Stephan A; Irlbacher, Kerstin; Röricht, Simone; Sabel, Bernhard A; Meyer, Bernd-Ulrich

2002-03-01

167

Repetitive Transcranial Magnetic Stimulation for the Treatment of Major Depressive Disorder  

PubMed Central

Executive Summary Objective This review was conducted to assess the effectiveness of repetitive transcranial magnetic stimulation (rTMS) in the treatment of major depressive disorder (MDD). The Technology rTMS is a noninvasive way to stimulate nerve cells in areas of the brain. During rTMS, an electrical current passes through a wire coil placed over the scalp. The current induces a magnetic field that produces an electrical field in the brain that then causes nerve cells to depolarize, resulting in the stimulation or disruption of brain activity. Researchers have investigated rTMS as an option to treat MDD, as an add-on to drug therapy, and, in particular, as an alternative to electroconvulsive therapy (ECT) for patients with treatment-resistant depression. The advantages of rTMS over ECT for patients with severe refractory depression are that general anesthesia is not needed, it is an outpatient procedure, it requires less energy, the simulation is specific and targeted, and convulsion is not required. The advantages of rTMS as an add-on treatment to drug therapy may include hastening of the clinical response when used with antidepressant drugs. Review Strategy The Medical Advisory Secretariat used its standard search strategy to locate international health technology assessments and English-language journal articles published from January 1996 to March 2004. Summary of Findings Some early meta-analyses suggested rTMS might be effective for the treatment of MDD (for treatment-resistant MDD and as an add-on treatment to drug therapy for patients not specifically defined as treatment resistant). There were, however, several crucial methodological limitations in the included studies that were not critically assessed. These are discussed below. Recent meta-analyses (including 2 international health technology assessments) have done evidence-based critical analyses of studies that have assessed rTMS for MDD. The 2 most recent health technology assessments (from the Oxford Cochrane Collaboration and the Norwegian Centre for Health Technology Assessment) concluded that there is no evidence that rTMS is effective for the treatment of MDD, either as compared with a placebo for patients with treatment-resistant or nontreatment-resistant MDD, or as an alternative to ECT for patients with treatment-resistant MDD. This mainly due to the poor quality of the studies. The major methodological limitations were identified in older meta-analyses, recent health technology assessments, and the most recently published trials (Level 2–4 evidence) on the effectiveness of rTMS for MDD are discussed below. Small sample size was a limitation acknowledged by many of the authors. There was also a lack of a priori sample size calculation or justification. Biased randomization may have been a problem. Generally, the published reports lacked detailed information on the method of allocation concealment used. This is important because it is impossible to determine if there was a possible influence (direct or indirect) in the allocation of the patients to different treatment groups. The trials were single blind, evaluated by external blinded assessors, rather than double blind. Double blinding is more robust, because neither the participants nor the investigators know which participants are receiving the active treatment and which are getting a placebo. Those administering rTMS, however, cannot be blinded to whether they are administering the active treatment or a placebo. There was patient variability among the studies. In some studies, the authors said that patients were “medication resistant,” but the definitions of resistant, if provided, were inconsistent or unclear. For example, some described “medication resistant” as failing at least one trial of drugs during the current depressive episode. Furthermore, it was unclear if the term “medication resistant” referred to antidepressants only or to combinations of antidepressants and other drug augmentation strategies (such as neuroleptics, benzodiazepine

2004-01-01

168

Repetitive transcranial magnetic stimulation applications normalized prefrontal dysfunctions and cognitive-related metabolic profiling in aged mice.  

PubMed

Chronic high-frequency repetitive transcranial magnetic stimulation (rTMS) is a noninvasive brain stimulation technique that has recently received increasing interests as a therapeutic procedure for neurodegenerative diseases. To identify the metabolism mechanism underlying the improving effects of rTMS, we observed that high frequency (25Hz) rTMS for 14 days could reverse the decline of the performance of the passive avoidance task in aged mice. We further investigated the metabolite profiles in the prefrontal cortex (PFC) in those mice and found that rTMS could also reverse the metabolic abnormalities of gamma-aminobutyric acid, N-acetyl aspartic, and cholesterol levels to the degree similar to the young mice. These data suggested that the rTMS could ameliorate the age-related cognitive impairment and improving the metabolic profiles in PFC, and potentially can be used to improve cognitive decline in the elderly. PMID:24278445

Wang, Hualong; Geng, Yuan; Han, Bing; Qiang, Jing; Li, Xiaoli; Sun, Meiyu; Wang, Qian; Wang, Mingwei

2013-01-01

169

Repetitive Transcranial Magnetic Stimulation Applications Normalized Prefrontal Dysfunctions and Cognitive-Related Metabolic Profiling in Aged Mice  

PubMed Central

Chronic high-frequency repetitive transcranial magnetic stimulation (rTMS) is a noninvasive brain stimulation technique that has recently received increasing interests as a therapeutic procedure for neurodegenerative diseases. To identify the metabolism mechanism underlying the improving effects of rTMS, we observed that high frequency (25Hz) rTMS for 14 days could reverse the decline of the performance of the passive avoidance task in aged mice. We further investigated the metabolite profiles in the prefrontal cortex (PFC) in those mice and found that rTMS could also reverse the metabolic abnormalities of gamma-aminobutyric acid, N-acetyl aspartic, and cholesterol levels to the degree similar to the young mice. These data suggested that the rTMS could ameliorate the age-related cognitive impairment and improving the metabolic profiles in PFC, and potentially can be used to improve cognitive decline in the elderly. PMID:24278445

Wang, Hualong; Geng, Yuan; Han, Bing; Qiang, Jing; Li, Xiaoli; Sun, Meiyu; Wang, Qian; Wang, Mingwei

2013-01-01

170

Repetitive Transcranial Magnetic Stimulation (rTMS) to Treat Social Anxiety Disorder: Case Reports and a Review of the Literature  

PubMed Central

Objectives: Social anxiety disorder (SAD) is a common and debilitating anxiety disorders. However, few studies had been dedicated to the neurobiology underlying SAD until the last decade. Rates of non-responders to standard methods of treatment remain unsatisfactorily high of approximately 25%, including SAD. Advances in our understanding of SAD could lead to new treatment strategies. A potential non invasive therapeutic option is repetitive transcranial magnetic stimulation (rTMS). Thus, we reported two cases of SAD treated with rTMS Methods: The bibliographical search used Pubmed/Medline, ISI Web of Knowledge and Scielo databases. The terms chosen for the search were: anxiety disorders, neuroimaging, repetitive transcranial magnetic stimulation. Results: In most of the studies conducted on anxiety disorders, except SAD, the right prefrontal cortex (PFC), more specifically dorsolateral PFC was stimulated, with marked results when applying high-rTMS compared with studies stimulating the opposite side. However, according to the “valence hypothesis”, anxiety disorders might be characterized by an interhemispheric imbalance associated with increased right-hemispheric activity. With regard to the two cases treated with rTMS, we found a decrease in BDI, BAI and LSAS scores from baseline to follow-up. Conclusion: We hypothesize that the application of low-rTMS over the right medial PFC (mPFC; the main structure involved in SAD circuitry) combined with high-rTMS over the left mPFC, for at least 4 weeks on consecutive weekdays, may induce a balance in brain activity, opening an attractive therapeutic option for the treatment of SAD. PMID:24278088

Paes, Flávia; Baczynski, Tathiana; Novaes, Felipe; Marinho, Tamires; Arias-Carrión, Oscar; Budde, Henning; Sack, Alexander T.; Huston, Joseph P.; Almada, Leonardo Ferreira; Carta, Mauro; Silva, Adriana Cardoso; Nardi, Antonio E.; Machado, Sergio

2013-01-01

171

Shaped magnetic field pulses by multi-coil repetitive transcranial magnetic stimulation (rTMS) differentially modulate anterior cingulate cortex responses and pain in volunteers and fibromyalgia patients  

PubMed Central

Background Repetitive transcranial magnetic stimulation (rTMS) has shown promise in the alleviation of acute and chronic pain by altering the activity of cortical areas involved in pain sensation. However, current single-coil rTMS technology only allows for effects in surface cortical structures. The ability to affect activity in certain deep brain structures may however, allow for a better efficacy, safety, and tolerability. This study used PET imaging to determine whether a novel multi-coil rTMS would allow for preferential targeting of the dorsal anterior cingulate cortex (dACC), an area always activated with pain, and to provide preliminary evidence as to whether this targeted approach would allow for efficacious, safe, and tolerable analgesia both in a volunteer/acute pain model as well as in fibromyalgia chronic pain patients. Methods Part 1: Different coil configurations were tested in a placebo-controlled crossover design in volunteers (N?=?16). Tonic pain was induced using a capsaicin/thermal pain model and functional brain imaging was performed by means of H215O positron emission tomography – computed tomography (PET/CT) scans. Differences in NRS pain ratings between TMS and sham treatment (NRSTMS-NRSplacebo) which were recorded each minute during the 10 minute PET scans. Part 2: 16 fibromyalgia patients were subjected to 20 multi-coil rTMS treatments over 4 weeks and effects on standard pain scales (Brief Pain Inventory, item 5, i.e. average pain NRS over the last 24 hours) were recorded. Results A single 30 minute session using one of 3 tested rTMS coil configurations operated at 1 Hz consistently produced robust reduction (mean 70% on NRS scale) in evoked pain in volunteers. In fibromyalgia patients, the 20 rTMS sessions also produced a significant pain inhibition (43% reduction in NRS pain over last 24 hours), but only when operated at 10 Hz. This degree of pain control was maintained for at least 4 weeks after the final session. Conclusion Multi-coil rTMS may be a safe and effective treatment option for acute as well as for chronic pain, such as that accompanying fibromyalgia. Further studies are necessary to optimize configurations and settings as well as to elucidate the mechanisms that lead to the long-lasting pain control produced by these treatments. PMID:23819466

2013-01-01

172

Opposite impact on 14 C-2-deoxyglucose brain metabolism following patterns of high and low frequency repetitive transcranial magnetic stimulation in the posterior parietal cortex  

Microsoft Academic Search

Repetitive transcranial magnetic stimulation (rTMS) appears capable of modulating human cortical excitability beyond the duration\\u000a of the stimulation train. However, the basis and extent of this “off-line” modulation remains unknown. In a group of anesthetized\\u000a cats, we applied patterns of real or sham focal rTMS to the visuo-parietal cortex (VP) at high (HF) or low (LF) frequency\\u000a and recorded brain

Antoni Valero-Cabré; Bertram R. Payne; Alvaro Pascual-Leone

2007-01-01

173

The relationship between brain oscillatory activity and therapeutic effectiveness of transcranial magnetic stimulation in the treatment of major depressive disorder.  

PubMed

Major depressive disorder (MDD) is marked by disturbances in brain functional connectivity. This connectivity is modulated by rhythmic oscillations of brain electrical activity, which enable coordinated functions across brain regions. Oscillatory activity plays a central role in regulating thinking and memory, mood, cerebral blood flow, and neurotransmitter levels, and restoration of normal oscillatory patterns is associated with effective treatment of MDD. Repetitive transcranial magnetic stimulation (rTMS) is a robust treatment for MDD, but the mechanism of action (MOA) of its benefits for mood disorders remains incompletely understood. Benefits of rTMS have been tied to enhanced neuroplasticity in specific brain pathways. We summarize here the evidence that rTMS entrains and resets thalamocortical oscillators, normalizes regulation and facilitates reemergence of intrinsic cerebral rhythms, and through this mechanism restores normal brain function. This entrainment and resetting may be a critical step in engendering neuroplastic changes and the antidepressant effects of rTMS. It may be possible to modify the method of rTMS administration to enhance this MOA and achieve better antidepressant effectiveness. We propose that rTMS can be administered: (1) synchronized to a patient's individual alpha frequency (IAF), or synchronized rTMS (sTMS); (2) as a low magnetic field strength sinusoidal waveform; and, (3) broadly to multiple brain areas simultaneously. We present here the theory and evidence indicating that these modifications could enhance the therapeutic effectiveness of rTMS for the treatment of MDD. PMID:23550274

Leuchter, Andrew F; Cook, Ian A; Jin, Yi; Phillips, Bill

2013-01-01

174

Chronic repetitive transcranial magnetic stimulation alters beta-adrenergic and 5-HT2 receptor characteristics in rat brain.  

PubMed

Repetitive transcranial magnetic stimulation (rTMS) has been shown to affect mood in health and disease. Evidence to date has demonstrated an antidepressant potential for low- and high-frequency rTMS treatment. In animal behavioral models of depression magnetic stimulation of the brain induced similar effects to those of electroconvulsive shock (ECS). In this study the effects of repeated rTMS on rat brain noradrenaline, dopamine, serotonin and their metabolites levels, as well as on beta-adrenergic and 5-HT2 receptor characteristics were studied. After 10 days of treatment, beta-adrenergic receptors were significantly up regulated in the frontal cortex, down regulated in the striatum and were unchanged in the hippocampus. 5-HT2 receptors were down regulated in the frontal cortex and were not changed in the other brain areas. No change in benzodiazepine receptors in the frontal cortex and cerebellum were demonstrated. These findings demonstrate specific and selective alterations induced by repeated rTMS, which are distinct from those induced by other antidepressant treatments. TMS therapeutic effects in humans and behavioral and biochemical effects in animal, suggest that TMS has a unique mechanism of action which requires further investigation. PMID:9878693

Ben-Shachar, D; Gazawi, H; Riboyad-Levin, J; Klein, E

1999-01-16

175

Movement and afferent representations in human motor areas: a simultaneous neuroimaging and transcranial magnetic/peripheral nerve-stimulation study  

PubMed Central

Neuroimaging combined with transcranial magnetic stimulation (TMS) to primary motor cortex (M1) is an emerging technique that can examine motor-system functionality through evoked activity. However, because sensory afferents from twitching muscles are widely represented in motor areas the amount of evoked activity directly resulting from TMS remains unclear. We delivered suprathreshold TMS to left M1 or gave electrical right median nerve stimulation (MNS) in 18 healthy volunteers while simultaneously conducting functional magnetic resonance imaging and monitoring with electromyography (EMG). We examined in detail the localization of TMS-, muscle afferent- and superficial afferent-induced activity in M1 subdivisions. Muscle afferent- and TMS-evoked activity occurred mainly in rostral M1, while superficial afferents generated a slightly different activation distribution. In 12 participants who yielded quantifiable EMG, differences in brain activity ascribed to differences in movement-size were adjusted using integrated information from the EMGs. Sensory components only explained 10–20% of the suprathreshold TMS-induced activity, indicating that locally and remotely evoked activity in motor areas mostly resulted from the recruitment of neural and synaptic activity. The present study appears to justify the use of fMRI combined with suprathreshold TMS to M1 for evoked motor network imaging. PMID:24062660

Shitara, H.; Shinozaki, T.; Takagishi, K.; Honda, M.; Hanakawa, T.

2013-01-01

176

Extended Remediation of Sleep Deprived-Induced Working Memory Deficits Using fMRI-guided Transcranial Magnetic Stimulation  

PubMed Central

Study Objectives: We attempted to prevent the development of working memory (WM) impairments caused by sleep deprivation using fMRI-guided repetitive transcranial magnetic stimulation (rTMS). Novel aspects of our fMRI-guided rTMS paradigm included the use of sophisticated covariance methods to identify functional networks in imaging data, and the use of fMRI-targeted rTMS concurrent with task performance to modulate plasticity effects over a longer term. Design: Between-groups mixed model. Setting: TMS, MRI, and sleep laboratory study. Participants: 27 subjects (13 receiving Active rTMS, and 14 Sham) completed the sleep deprivation protocol, with another 21 (10 Active, 11 Sham) non-sleep deprived subjects run in a second experiment. Interventions: Our previous covariance analysis had identified a network, including occipital cortex, which demonstrated individual differences in resilience to the deleterious effects of sleep deprivation on WM performance. Five Hz rTMS was applied to left lateral occipital cortex while subjects performed a WM task during 4 sessions over the course of 2 days of total sleep deprivation. Measurements and Results: At the end of the sleep deprivation period, Sham sleep deprived subjects exhibited degraded performance in the WM task. In contrast, those receiving Active rTMS did not show the slowing and lapsing typical in sleep deprivation, and instead performed similarly to non- sleep deprived subjects. Importantly, the Active sleep deprivation group showed rTMS-induced facilitation of WM performance a full 18 hours after the last rTMS session. Conclusions: Over the course of sleep deprivation, these results indicate that rTMS applied concurrently with WM task performance affected neural circuitry involved in WM to prevent its full impact. Citation: Luber B; Steffener J; Tucker A; Habeck C; Peterchev AV; Deng ZD; Basner RC; Stern Y; Lisanby SH. Extended remediation of sleep deprived-induced working memory deficits using fMRI-guided transcranial magnetic stimulation. SLEEP 2013;36(6):857-871. PMID:23729929

Luber, Bruce; Steffener, Jason; Tucker, Adrienne; Habeck, Christian; Peterchev, Angel V.; Deng, Zhi-De; Basner, Robert C.; Stern, Yaakov; Lisanby, Sarah H.

2013-01-01

177

SKA Deep Polarization and Cosmic Magnetism  

E-print Network

Deep surveys with the SKA1-MID array offer for the first time the opportunity to systematically explore the polarization properties of the microJy source population. Our knowledge of the polarized sky approaching these levels is still very limited. In total intensity the population will be dominated by star-forming and normal galaxies to intermediate redshifts ($z \\sim1-2$), and low-luminosity AGN to high redshift. The polarized emission from these objects is a powerful probe of their intrinsic magnetic fields and of their magnetic environments. For redshift of order 1 and above the broad bandwidth of the mid-bands span the Faraday thick and thin regimes allowing study of the intrinsic polarization properties of these objects as well as depolarization from embedded and foreground plasmas. The deep field polarization images will provide Rotation Measures data with very high solid angle density allowing a sensitive statistical analysis of the angular variation of RM on critical arc-minute scales from a magnetic...

Taylor, A R; Akahori, Takuya; Beck, Rainer; Gaensler, Bryan; Heald, George; Johnston-Hollitt, Melanie; Langer, Mathieu; Rudnick, Lawrence; Ryu, Dongsu; Scaife, Anna; Schleicher, Dominik; Stil, Jeroen

2015-01-01

178

Cerebellar-related long latency motor response in upper limb musculature by transcranial magnetic stimulation of the cerebellum.  

PubMed

In this study, we aimed to identify the cerebellum-related electromyographic (EMG) response that appeared in the upper limbs musculature. Thirty times averaged transcranial magnetic stimulation (TMS) with a double-cone coil placed over the cerebellar hemisphere elicited long latency EMG responses at the bilateral extensor carpi radialis (ECR) muscles. The peak latency of this EMG response was 70.7±12.7 ms in the ipsilateral ECR and 62.9±10.2 ms in the contralateral ECR of the TMS side. These latencies were much longer than the latency of the muscle evoked potential when we stimulated pyramidal tracts at the foramen magnum level. Cerebellar hemisphere loading by the finger target pursuit test made this EMG response faster during TMS on the ipsilateral side of the cerebellum and slower during TMS on the contralateral side of the cerebellum. Furthermore, the deeper the level of drowsiness, the slower the peak latency of this EMG response became. These results suggest that this EMG potential is a specific response of the cerebellum and brainstem reticular formation, and may be conducted from the cerebellar structure to the ECR muscle through the polysynaptic transmission of the reticulospinal tract. PMID:24113113

Hosokawa, Sachiyo; Hirata, Masayuki; Goto, Tetsu; Yanagisawa, Takufumi; Sugata, Hisato; Araki, Toshihiko; Okamura, Yumiko; Hasegawa, Yuka; Shinshi, Misako; Yorifuji, Shiro

2014-04-16

179

Does Inhibitory Repetitive Transcranial Magnetic Stimulation Augment Functional Task Practice to Improve Arm Recovery in Chronic Stroke?  

PubMed Central

Introduction. Restoration of upper extremity (UE) functional use remains a challenge for individuals following stroke. Repetitive transcranial magnetic stimulation (rTMS) is a noninvasive modality that modulates cortical excitability and is being explored as a means to potentially ameliorate these deficits. The purpose of this study was to evaluate, in the presence of chronic stroke, the effects of low-frequency rTMS to the contralesional hemisphere as an adjuvant to functional task practice (FTP), to improve UE functional ability. Methods. Twenty-two individuals with chronic stroke and subsequent moderate UE deficits were randomized to receive 16 sessions (4 times/week for 4 weeks) of either real-rTMS or sham-rTMS followed by 1-hour of paretic UE FTP. Results. No differences in UE outcomes were revealed between the real-rTMS and sham-rTMS intervention groups. After adjusting for baseline differences, no differences were revealed in contralesional cortical excitability postintervention. In a secondary analysis, data pooled across both groups revealed small, but statistically significant, improvements in UE behavioral measures. Conclusions. rTMS did not augment changes in UE motor ability in this population of individuals with chronic stroke. The chronicity of our participant cohort and their degree of UE motor impairment may have contributed to inability to produce marked effects using rTMS. PMID:25197611

McGuirk, Theresa E.; Triggs, William J.

2014-01-01

180

Bilateral Repetitive Transcranial Magnetic Stimulation for Auditory Hallucinations in Patients with Schizophrenia: A Randomized Controlled, Cross-over Study  

PubMed Central

Objective A randomized double-blind cross-over trial was conducted in patients with persistent auditory hallucinations (AHs) to investigate whether bilateral repetitive transcranial magnetic stimulation (rTMS) at the temporoparietal area or Broca's area is more effective at high- or low-frequencies compared to a sham condition. Methods Twenty three patients with persistent AHs who remained stable on the same medication for 2 months were enrolled. They were randomized to one of four conditions: low-frequency (1 Hz)-rTMS to the temporoparietal area (L-TP), high-frequency (20 Hz)-rTMS to the temporoparietal area (H-TP), high-frequency (20 Hz)-rTMS to Broca's area (H-B), or sham. Results All the four rTMS conditions resulted in significant decrease in the scores under the auditory hallucination rating scale and hallucination change scale over time. However, there were no significant treatment effects or interaction between time and treatment, suggesting no superior effects of the new paradigms over the sham condition. Conclusion Our findings suggest that bilateral rTMS at the temporoparietal area or Broca's area with high- or low-frequency does not produce superior effects in reducing AHs compared to sham stimulation. PMID:25598827

Kim, Eun-Ji; Yeo, Seonguk; Hwang, Inho; Park, Jong-Il; Cui, Yin; Jin, Hong-Mei; Kim, Hyung Tae; Hwang, Tae-Young

2014-01-01

181

Representation of goal and movements without overt motor behavior in the human motor cortex: a transcranial magnetic stimulation study.  

PubMed

We recorded motor-evoked potentials (MEPs) to transcranial magnetic stimulation from the right opponens pollicis (OP) muscle while participants observed an experimenter operating two types of pliers: pliers opened by the extension of the fingers and closed by their flexion ("normal pliers") and pliers opened by the flexion of the fingers and closed by their extension ("reverse pliers"). In one experimental condition, the experimenter merely opened and closed the pliers; in the other, he grasped an object with them. In a further condition, the participants imagined themselves operating the normal and reverse pliers. During the observation of actions devoid of a goal, the MEP amplitudes, regardless of pliers used, reflected the muscular pattern involved in the execution of the observed action. In contrast, during the observation of goal-directed actions, the MEPs from OP were modulated by the action goal, increasing during goal achievement despite the opposite hand movements necessary to obtain it. During motor imagery, the MEPs recorded from OP reflected the muscular pattern required to perform the imagined action. We propose that covert activity in the human motor cortex may reflect different aspects of motor behavior. Imagining oneself performing tool actions or observing tool actions devoid of a goal activates the representation of the hand movements that correspond to the observed ones. In contrast, the observation of tool actions with a goal incorporates the distal part of the tool in the observer's body schema, resulting in a higher-order representation of the meaning of the motor act. PMID:19741119

Cattaneo, Luigi; Caruana, Fausto; Jezzini, Ahmad; Rizzolatti, Giacomo

2009-09-01

182

Transcranial Magnetic Stimulation Reveals Dissociable Mechanisms for Global Versus Selective Corticomotor Suppression Underlying the Stopping of Action  

PubMed Central

Stopping an initiated response is an essential function, investigated in many studies with go/no-go and stop-signal paradigms. These standard tests require rapid action cancellation. This appears to be achieved by a suppression mechanism that has “global” effects on corticomotor excitability (i.e., affecting task-irrelevant muscles). By contrast, stopping action in everyday life may require selectivity (i.e., targeting a specific response tendency without affecting concurrent action). We hypothesized that while standard stopping engages global suppression, behaviorally selective stopping engages a selective suppression mechanism. Accordingly, we measured corticomotor excitability of the task-irrelevant leg using transcranial magnetic stimulation while subjects stopped the hand. Experiment 1 showed that for standard (i.e., nonselective) stopping, the task-irrelevant leg was suppressed. Experiment 2 showed that for behaviorally selective stopping, there was no mean leg suppression. Experiment 3 directly compared behaviorally nonselective and selective stopping. Leg suppression occurred only in the behaviorally nonselective condition. These results argue that global and selective suppression mechanisms are dissociable. Participants may use a global suppression mechanism when speed is stressed; however, they may recruit a more selective suppression mechanism when selective stopping is behaviorally necessary and preparatory information is available. We predict that different fronto–basal–ganglia pathways underpin these different suppression mechanisms. PMID:21666129

Majid, D. S. Adnan; Cai, Weidong; George, Jobi S.; Verbruggen, Frederick

2012-01-01

183

Disrupted Central Inhibition after Transcranial Magnetic Stimulation of Motor Cortex in Schizophrenia with Long-Term Antipsychotic Treatment  

PubMed Central

Aims. Schizophrenia is a neuropsychiatric disorder associated with mental and motor disturbances. We aimed to investigate motor control, especially central silent period (CSP) in subjects with schizophrenia (n = 11) on long-term antipsychotic treatment compared to healthy controls (n = 9). Methods. Latency and duration of motor evoked potentials (MEPs) and CSPs were measured with the help of single pulse transcranial magnetic stimulation (TMS) and intramuscular electrodes. After stimulation of the dominant and nondominant motor cortex of abductor digiti minimi (ADM) and tibialis anterior (TA) muscle areas, respective responses were measured on the contralateral side. Results. MEPs did not differ significantly between the groups. Multiple CSPs were found predominantly in subjects with schizophrenia, which showed a higher number of CSPs in the dominant ADM and the longest summarized duration of CSPs in the nondominant ADM (P < 0.05) compared to controls. Conclusions. There were multiple CSPs predominantly in the upper extremities and in the dominant body side in subjects with schizophrenia. Behind multiple CSPs may lie an impaired regulation of excitatory or inhibitory neurotransmitter systems in central motor pathways. Further research is needed to clarify the role of the intramuscular recording methods and the effect of antipsychotics on the results. PMID:23738224

Lauerma, Hannu; Kähkönen, Seppo

2013-01-01

184

Repetitive transcranial magnetic stimulation over the orbitofrontal cortex for obsessive-compulsive disorder: a double-blind, crossover study  

PubMed Central

This pilot study was designed to assess the efficacy of low-frequency repetitive transcranial magnetic stimulation (rTMS) over the right orbitofrontal cortex (OFC) by means of a double-cone coil in patients suffering from obsessive-compulsive disorder. We hypothesized that low-frequency stimulation of the OFC would lead to a reduction in clinical symptoms, as measured on the Yale-Brown Obsessive Compulsive Scale (Y-BOCS). A randomized, double-blind, crossover design was implemented with two 1-week treatment periods (active stimulation versus sham stimulation) separated by a 1-month washout period. Concomitantly, a subgroup of patients underwent a positron emission tomography (PET) scan after each stimulation sequence. Statistical analyses compared the Y-BOCS scores at the end of each period. At day 7, we observed a significant decrease from baseline in the Y-BOCS scores, after both active (P<0.01) and sham stimulation (P=0.02). This decrease tended to be larger after active stimulation than after sham stimulation: ?6 (?29, 0) points versus ?2 (?20, 4) points (P=0.07). Active versus sham PET scan contrasts showed that stimulation was related to a bilateral decrease in the metabolism of the OFC. The OFC should definitely be regarded as a key neuroanatomical target for rTMS, as it is easier to reach than either the striatum or the subthalamic nucleus, structures favored in neurosurgical approaches. PMID:25203167

Nauczyciel, C; Le Jeune, F; Naudet, F; Douabin, S; Esquevin, A; Vérin, M; Dondaine, T; Robert, G; Drapier, D; Millet, B

2014-01-01

185

Animal models of the mechanisms of action of repetitive transcranial magnetic stimulation (RTMS): comparisons with electroconvulsive shock (ECS).  

PubMed

Repetitive transcranial magnetic stimulation (rTMS) is a noninvasive means of brain stimulation with a broad range of basic neuroscience and potential future clinical applications. Recent animal studies have shed some light on the mechanisms of action of rTMS, and broadened our understanding of how this intervention affects brain functioning acutely and chronically. Differences in the physical properties of magnetic and electrical stimulation result in marked disparities in the amount and distribution of electrical current induced in the brain; nevertheless, rTMS shares many of the behavioral and biochemical actions of electroconvulsive shock (ECS) and other antidepressant treatments. rTMS reduces immobility in the Porsolt swim task and enhances apomorphine-induced stereotypy, as does ECS. Although rTMS can induce a seizure when given at high enough doses, most studies have found subconvulsive levels of rTMS to be anticonvulsant. rTMS acutely modulates dopamine and serotonin content and turnover rates. Chronic rTMS modulates cortical beta-adrenergic receptors, reduces frontal cortex 5-HT2 receptors, increases 5-hydroxytryptamine1A receptors in frontal cortex and cingulate, and increases N-methyl-D-aspartate receptors in the ventromedial hypothalamus, basolateral amygdala, and parietal cortex. More work will be needed to clarify and explore the mechanism behind the early suggestions that rTMS may exert long-term-potentiation-like or long-term-depression-like action on hippocampal activity. Finally, rTMS is emerging as yet another intervention, like ECS and other antidepressants, that can regulate gene expression and may have an impact on neuronal viability and synaptic plasticity. PMID:11126193

Lisanby, S H; Belmaker, R H

2000-01-01

186

Safety, ethical considerations, and application guidelines for the use of transcranial magnetic stimulation in clinical practice and research?  

PubMed Central

This article is based on a consensus conference, which took place in Certosa di Pontignano, Siena (Italy) on March 7–9, 2008, intended to update the previous safety guidelines for the application of transcranial magnetic stimulation (TMS) in research and clinical settings. Over the past decade the scientific and medical community has had the opportunity to evaluate the safety record of research studies and clinical applications of TMS and repetitive TMS (rTMS). In these years the number of applications of conventional TMS has grown impressively, new paradigms of stimulation have been developed (e.g., patterned repetitive TMS) and technical advances have led to new device designs and to the real-time integration of TMS with electroencephalography (EEG), positron emission tomography (PET) and functional magnetic resonance imaging (fMRI). Thousands of healthy subjects and patients with various neurological and psychiatric diseases have undergone TMS allowing a better assessment of relative risks. The occurrence of seizures (i.e., the most serious TMS-related acute adverse effect) has been extremely rare, with most of the few new cases receiving rTMS exceeding previous guidelines, often in patients under treatment with drugs which potentially lower the seizure threshold. The present updated guidelines review issues of risk and safety of conventional TMS protocols, address the undesired effects and risks of emerging TMS interventions, the applications of TMS in patients with implanted electrodes in the central nervous system, and safety aspects of TMS in neuroimaging environments. We cover recommended limits of stimulation parameters and other important precautions, monitoring of subjects, expertise of the rTMS team, and ethical issues. While all the recommendations here are expert based, they utilize published data to the extent possible. PMID:19833552

Rossi, Simone; Hallett, Mark; Rossini, Paolo M.; Pascual-Leone, Alvaro

2011-01-01

187

Magnetic resonance imaging/angiography and transcranial Doppler velocities in sickle cell anemia: results from the SWiTCH trial.  

PubMed

The Stroke With Transfusions Changing to Hydroxyurea (SWiTCH) trial compared standard (transfusions/chelation) to alternative (hydroxyurea/phlebotomy) treatment to prevent recurrent stroke and manage iron overload in children chronically transfused over 7 years before enrollment. Standardized brain magnetic resonance imaging/magnetic resonance angiography (MRA) and transcranial Doppler (TCD) exams were performed at entry and exit, with a central blinded review. A novel MRA vasculopathy grading scale demonstrated frequent severe baseline left/right vessel stenosis (53%/41% ?Grade 4); 31% had no vessel stenosis on either side. Baseline parenchymal injury was prevalent (85%/79% subcortical, 53%/37% cortical, 50%/35% subcortical and cortical). Most children had low or uninterpretable baseline middle cerebral artery TCD velocities, which were associated with worse stenoses (incidence risk ratio [IRR] = 5.1, P ? .0001 and IRR = 4.1, P < .0001) than normal velocities; only 2% to 12% had any conditional/abnormal velocity. Patients with adjudicated stroke (7) and transient ischemic attacks (19 in 11 standard/8 alternative arm subjects) had substantial parenchymal injury/vessel stenosis. At exit, 1 child (alternative arm) had a new silent infarct, and another had worse stenosis. SWiTCH neuroimaging data document severe parenchymal and vascular abnormalities in children with SCA and stroke and support concerns about chronic transfusions lacking effectiveness for preventing progressive cerebrovascular injury. The novel SWiTCH vasculopathy grading scale warrants validation testing and consideration for use in future clinical trials. This trial was registered at www.clinicaltrials.gov as #NCT00122980. PMID:24914136

Helton, Kathleen J; Adams, Robert J; Kesler, Karen L; Lockhart, Alex; Aygun, Banu; Driscoll, Catherine; Heeney, Matthew M; Jackson, Sherron M; Krishnamurti, Lakshmanan; Miller, Scott T; Sarnaik, Sharada A; Schultz, William H; Ware, Russell E

2014-08-01

188

Anti-depressive mechanism of repetitive transcranial magnetic stimulation in rat: the role of the endocannabinoid system.  

PubMed

Repetitive transcranial magnetic stimulation (rTMS) to treat depression has been thoroughly investigated in recent years. However, the underlying mechanisms are not fully understood. In this study, a chronic unpredictable mild stress (CUMS) paradigm was applied to male Sprague Dawley rats. Then rTMS was performed for 7 consecutive days, and the anti-depressive effects were evaluated by the sucrose preference test (SPT), the forced swimming test (FST), and the open-field test (OFT). Hippocampal cannabinoid type I receptor (CB1) expression was measured, and the expression levels of brain-derived neurotrophic factor (BDNF), Bcl-2, and Bax and the number of bromodeoxyuridine (BrdU)-positive cells were also investigated. These parameters were also observed after the selective CB1 receptor antagonist AM251 was used as a blocking agent. The results showed that CUMS induced a significant decrease in sucrose preference, a significant increase in immobility time in the FST, and a significantly decreased horizontal distance in the OFT. In addition, reduced hippocampal CB1 receptor, BDNF, and Bcl-2/Bax protein expression levels in CUMS rats, as well as decreased cell proliferation were also observed in the dentate gyrus. Meanwhile, rTMS treatment up-regulated cell proliferation; elevated CB1 receptor, BDNF, and Bcl-2/Bax expression levels in the hippocampus; and ameliorated depressive-like behaviors. All of these beneficial effects were abolished by AM251. These results indicate that rTMS increases BDNF production and hippocampal cell proliferation to protect against CUMS-induced changes through its effect on CB1 receptors. PMID:24479995

Wang, Hua-ning; Wang, Lei; Zhang, Rui-guo; Chen, Yun-chun; Liu, Ling; Gao, Fang; Nie, Huang; Hou, Wu-gang; Peng, Zheng-wu; Tan, Qingrong

2014-04-01

189

Diffusion tensor fiber tracking in patients with central post-stroke pain; correlation with efficacy of repetitive transcranial magnetic stimulation.  

PubMed

Central post-stroke pain (CPSP) is one of the most common types of intractable pain. We reported that repetitive transcranial magnetic stimulation (rTMS) of primary motor cortex relieves pain for patients who were refractory to medical treatment. But the mechanism is unclear. In the present study, we investigated relations between the characteristics of CPSP and the results of fiber tracking, which is the only noninvasive method of evaluating the anatomical connectivity of white matter pathways. Fiber tracking of the corticospinal tract (CST) and thalamocortical tract (TCT) was investigated in 17 patients with CPSP. The stroke lesion was located in a supratentorial region in all cases (corona radiata, one case; thalamus, seven cases; putamen, nine cases). Relations between the delineation ratio (defined as the ratio of the cross section of the affected side to that of the unaffected side) of the CST and of the TCT, manual muscle test score, pain score, region of pain, and efficacy of rTMS were evaluated. Fiber tracking was successful in 13 patients with the stroke lesion involving the TCT. The rTMS-effective group had higher delineation ratio of the CST (p=0.02) and the TCT (p=0.005) than the rTMS-ineffective group. Previous studies suggested that an intact CST allows pain control but did not discuss the TCT. Our results suggest that the TCT also plays a role in pain reduction by rTMS of the primary motor cortex and that the efficacy of rTMS for patients with CPSP is predictable by fiber tracking. PMID:19004554

Goto, Tetsu; Saitoh, Youichi; Hashimoto, Naoya; Hirata, Masayuki; Kishima, Haruhiko; Oshino, Satoru; Tani, Naoki; Hosomi, Koichi; Kakigi, Ryusuke; Yoshimine, Toshiki

2008-12-01

190

Low-intensity repetitive transcranial magnetic stimulation improves abnormal visual cortical circuit topography and upregulates BDNF in mice.  

PubMed

Repetitive transcranial magnetic stimulation (rTMS) is increasingly used as a treatment for neurological and psychiatric disorders. Although the induced field is focused on a target region during rTMS, adjacent areas also receive stimulation at a lower intensity and the contribution of this perifocal stimulation to network-wide effects is poorly defined. Here, we examined low-intensity rTMS (LI-rTMS)-induced changes on a model neural network using the visual systems of normal (C57Bl/6J wild-type, n = 22) and ephrin-A2A5(-/-) (n = 22) mice, the latter possessing visuotopic anomalies. Mice were treated with LI-rTMS or sham (handling control) daily for 14 d, then fluorojade and fluororuby were injected into visual cortex. The distribution of dorsal LGN (dLGN) neurons and corticotectal terminal zones (TZs) was mapped and disorder defined by comparing their actual location with that predicted by injection sites. In the afferent geniculocortical projection, LI-rTMS decreased the abnormally high dispersion of retrogradely labeled neurons in the dLGN of ephrin-A2A5(-/-) mice, indicating geniculocortical map refinement. In the corticotectal efferents, LI-rTMS improved topography of the most abnormal TZs in ephrin-A2A5(-/-) mice without altering topographically normal TZs. To investigate a possible molecular mechanism for LI-rTMS-induced structural plasticity, we measured brain derived neurotrophic factor (BDNF) in the visual cortex and superior colliculus after single and multiple stimulations. BDNF was upregulated after a single stimulation for all groups, but only sustained in the superior colliculus of ephrin-A2A5(-/-) mice. Our results show that LI-rTMS upregulates BDNF, promoting a plastic environment conducive to beneficial reorganization of abnormal cortical circuits, information that has important implications for clinical rTMS. PMID:25100609

Makowiecki, Kalina; Harvey, Alan R; Sherrard, Rachel M; Rodger, Jennifer

2014-08-01

191

Effect of chronic and acute low-frequency repetitive transcranial magnetic stimulation on spatial memory in rats.  

PubMed

Repetitive transcranial magnetic stimulation (rTMS) is a novel, non-invasive neurological and psychiatric tool. The low-frequency (1 Hz or less) rTMS is likely to play a particular role in its mechanism of action with different effects in comparison with high-frequency (>1 Hz) rTMS. There is limited information regarding the effect of low-frequency rTMS on spatial memory. In our study, each male Wistar rat was daily given 300 stimuli (1.0 T, 200 micros) at a rate of 0.5 Hz or sham stimulation. We investigated the effects of chronic and acute rTMS on reference/working memory process in Morris water maze test with the hypothesis that the effect would differ by chronic or acute condition. Chronic low-frequency rTMS impaired the retrieval of spatial short- and long-term spatial reference memory but not acquisition process and working memory, whereas acute low-frequency rTMS predominantly induced no deficits in acquisition or short-term spatial reference memory as well as working memory except for long-term reference memory. In summary, chronic 0.5 Hz rTMS disrupts spatial short- and long-term reference memory function, but acute rTMS differently affects reference memory. Chronic low-frequency rTMS may be used to modulate reference memory. Treatment protocols using low-frequency rTMS in neurological and psychiatric disorders need to take into account the potential effect of chronic low-frequency rTMS on memory and other cognitive functions. PMID:17259018

Li, Wei; Yang, Yuye; Ye, Qing; Yang, Bo; Wang, Zhengrong

2007-03-15

192

The molecular evidence of neural plasticity induced by cerebellar repetitive transcranial magnetic stimulation in the rat brain: a preliminary report.  

PubMed

Cerebellar repetitive transcranial magnetic stimulation (rTMS) has been applied to treat several pathological conditions with insufficient evidence of molecular mechanism. Neural plasticity is proposed as one of mechanism. This study aimed to (1) confirm the feasibility of focal stimulation over cerebellar cortex and (2) investigate cerebellar rTMS effects on molecular changes associated with neural plasticity in the rat. For feasibility, six male Sprague-Dawley rats underwent (18)F-FDG positron emission tomography (PET) to confirm focal stimulation on the cerebellar cortex after rTMS. For molecular evidence, thirty rats underwent a single (N=15) or 10 sessions (N=15) of rTMS with low-, high-frequency, or sham stimulation. In cerebellar cortex, reverse-transcriptase polymerase chain reaction and western blotting were performed on mRNA and proteins associated with neural plasticity: metabotrophic glutamate receptor 1 (GluR1), 2-amino-5-methyl-4-isoxazole-propionatic acid (AMPA) receptor (GluR2) and protein kinase C (PKC). As a result, (18)F-FDG-PET showed an increase of glucose metabolism in the cerebellar cortex. The transcription of mGluR1 decreased following a single session of high-frequency rTMS. Synthesis of mGluR, PKC and GluR2 was reduced after rTMS, especially high frequency stimulation. It is suggested that rTMS could focus on the cerebellar cortex in the rat and induce neural plasticity associated with long-term depression. PMID:24861505

Lee, Seung Ah; Oh, Byung-Mo; Kim, Sang Jeong; Paik, Nam-Jong

2014-07-11

193

Changes in motor cortex excitability associated with temporal repetitive transcranial magnetic stimulation in tinnitus: hints for cross-modal plasticity?  

PubMed Central

Background Motor cortex excitability was found to be changed after repetitive transcranial magnetic stimulation (rTMS) of the temporal cortex highlighting the occurrence of cross-modal plasticity in non-invasive brain stimulation. Here, we investigated the effects of temporal low-frequency rTMS on motor cortex plasticity in a large sample of tinnitus patients. In 116 patients with chronic tinnitus different parameters of cortical excitability were assessed before and after ten rTMS treatment sessions. Patients received one of three different protocols all including 1 Hz rTMS over the left temporal cortex. Treatment response was defined as improvement by at least five points in the tinnitus questionnaire (TQ). Variables of interest were resting motor threshold (RMT), short-interval intra-cortical inhibition (SICI), intracortical facilitation (ICF), and cortical silent period (CSP). Results After rTMS treatment RMT was decreased by about 1% of stimulator output near-significantly in the whole group of patients. SICI was associated with significant changes with respect to treatment response. The group of treatment responders showed a decrease of SICI over the course of treatment, the group of non-responders the reverse pattern. Conclusions Minor RMT changes during rTMS treatment do not necessarily suggest the need for systematic re-examination of the RMT for safety and efficacy issues. Treatment response to rTMS was shown to be related to changes in SICI that might reflect modulation of GABAergic mechanisms directly or indirectly related to rTMS treatment effects. PMID:24898574

2014-01-01

194

Descending motor pathways and cortical physiology after spinal cord injury assessed by transcranial magnetic stimulation: a systematic review.  

PubMed

We performed here a systematic review of the studies using transcranial magnetic stimulation (TMS) as a research and clinical tool in patients with spinal cord injury (SCI). Motor evoked potentials (MEPs) elicited by TMS represent a highly accurate diagnostic test that can supplement clinical examination and neuroimaging findings in the assessment of SCI functional level. MEPs allows to monitor the changes in motor function and evaluate the effects of the different therapeutic approaches. Moreover, TMS represents a useful non-invasive approach for studying cortical physiology, and may be helpful in elucidating the pathophysiological mechanisms of brain reorganization after SCI. Measures of motor cortex reactivity, e.g., the short interval intracortical inhibition and the cortical silent period, seem to point to an increased cortical excitability. However, the results of TMS studies are sometimes contradictory or divergent, and should be replicated in a larger sample of subjects. Understanding the functional changes at brain level and defining their effects on clinical outcome is of crucial importance for development of evidence-based rehabilitation therapy. TMS techniques may help in identifying neurophysiological biomarkers that can reliably assess the extent of neural damage, elucidate the mechanisms of neural repair, predict clinical outcome, and identify therapeutic targets. Some researchers have begun to therapeutically use repetitive TMS (rTMS) in patients with SCI. Initial studies revealed that rTMS can induce acute and short duration beneficial effects especially on spasticity and neuropathic pain, but the evidence is to date still very preliminary and well-designed clinical trials are warranted. This article is part of a Special Issue entitled SI: Spinal cord injury. PMID:25251591

Nardone, Raffaele; Höller, Yvonne; Brigo, Francesco; Orioli, Andrea; Tezzon, Frediano; Schwenker, Kerstin; Christova, Monica; Golaszewski, Stefan; Trinka, Eugen

2014-09-22

195

Finding the Right Words: Transcranial Magnetic Stimulation Improves Discourse Productivity in Non-fluent Aphasia After Stroke  

PubMed Central

Background Loss of fluency is a significant source of functional impairment in many individuals with aphasia. Repetitive transcranial magnetic stimulation (rTMS) administered to the right inferior frontal gyrus (IFG) has been shown to facilitate naming in persons with chronic left hemisphere stroke and non-fluent aphasia. However, changes in fluency in aphasic subjects receiving rTMS have not been adequately explored. Aims To determine whether rTMS improves fluency in individuals with chronic nonfluent aphasia, and to identify aspects of fluency that are modulated in persons who respond to rTMS. Methods & Procedures Ten individuals with left hemisphere MCA strokes and mild to moderate non-fluent aphasia participated in the study. Before treatment, subjects were asked to describe the Cookie Theft picture in three separate sessions. During treatment, all subjects received 1200 pulses of 1 Hz rTMS daily in 10 sessions over two weeks at a site that had previously been shown to improve naming. Subjects repeated the Cookie Theft description two months after treatment. Five subjects initially received sham stimulation instead of real TMS. Two months after sham treatment, these individuals received real rTMS. Performance both at baseline and after stimulation was coded using Quantitative Production Analysis (Saffran, Berndt & Schwartz, 1989) and Correct Information Unit (Nicholas & Brookshire, 1993) analysis. Outcomes & Results Across all subjects (n=10), real rTMS treatment resulted in a significant increase in multiple measures of discourse productivity compared to baseline performance. There was no significant increase in measures of sentence productivity or grammatical accuracy. There was no significant increase from baseline in the sham condition (n=5) on any study measures. Conclusions Stimulation of the right IFG in patients with chronic non-fluent aphasia facilitates discourse production. We posit that this effect may be attributable to improved lexical-semantic access. PMID:23280015

Medina, Jared; Norise, Catherine; Faseyitan, Olufunsho; Coslett, H. Branch; Turkeltaub, Peter E.; Hamilton, Roy H.

2012-01-01

196

Medium-term results of combined treatment with transcranial magnetic stimulation and antidepressant drug for chronic tinnitus.  

PubMed

We compared the effects of repetitive transcranial magnetic stimulation (rTMS) and paroxetine [a selective serotonin reuptake inhibitor (SSRI)] on tinnitus in terms of effectiveness and medium-term results. This is a randomised, double-blind, placebo-controlled study. Seventy-five patients with moderate tinnitus were divided into five equal groups. Each group was treated for 1 month as follows: group 1 received rTMS alone at 1 Hz frequency; group 2 received rTMS alone at 10 Hz frequency; group 3 received rTMS at 1 Hz frequency combined with paroxetine; group 4 received paroxetine alone; and group 5 received a placebo (sham rTMS). Participants were tested using the Tinnitus Handicap Inventory (THI), Tinnitus Severity Index (TSI), the Beck Anxiety Scoring (BAS), and Psychiatric Sign Screening (PSS) tests. THI, TSI, BAS, and PSS were measured prior to treatment, and at the first and sixth month post-treatment. The THI and TSI scores improved after treatment in all groups, except the placebo group. The THI scores in groups 1 and 2 showed a statistically significant improvement after the first and sixth month compared to pretreatment scores, whereas a significant improvement in THI scores occurred only after the sixth month in groups 3 and 4. The TSI scores in group 3 showed a significant improvement at the first and sixth month marks after treatment. The rTMS and SSRI play potential roles in the reduction of tinnitus severity, but without cumulative or synergistic effects when a combination of treatment regimens is applied. These positive effects might be due to the relationship between the auditory cortex areas related to emotions and tinnitus. PMID:24337899

Bilici, Suat; Yigit, Ozgur; Taskin, Umit; Gor, Ayse Pelin; Yilmaz, Enver Demirel

2015-02-01

197

Group-level variations in motor representation areas of thenar and anterior tibial muscles: Navigated Transcranial Magnetic Stimulation Study.  

PubMed

Navigated transcranial magnetic stimulation (TMS) can be used to stimulate functional cortical areas at precise anatomical location to induce measurable responses. The stimulation has commonly been focused on anatomically predefined motor areas: TMS of that area elicits a measurable muscle response, the motor evoked potential. In clinical pathologies, however, the well-known homunculus somatotopy theory may not be straightforward, and the representation area of the muscle is not fixed. Traditionally, the anatomical locations of TMS stimulations have not been reported at the group level in standard space. This study describes a methodology for group-level analysis by investigating the normal representation areas of thenar and anterior tibial muscle in the primary motor cortex. The optimal representation area for these muscles was mapped in 59 healthy right-handed subjects using navigated TMS. The coordinates of the optimal stimulation sites were then normalized into standard space to determine the representation areas of these muscles at the group-level in healthy subjects. Furthermore, 95% confidence interval ellipsoids were fitted into the optimal stimulation site clusters to define the variation between subjects in optimal stimulation sites. The variation was found to be highest in the anteroposterior direction along the superior margin of the precentral gyrus. These results provide important normative information for clinical studies assessing changes in the functional cortical areas because of plasticity of the brain. Furthermore, it is proposed that the presented methodology to study TMS locations at the group level on standard space will be a suitable tool for research purposes in population studies. PMID:20082330

Niskanen, Eini; Julkunen, Petro; Säisänen, Laura; Vanninen, Ritva; Karjalainen, Pasi; Könönen, Mervi

2010-08-01

198

Differential effects of motor cortical excitability and plasticity in young and old individuals: a Transcranial Magnetic Stimulation (TMS) study.  

PubMed

Aging is associated with changes in the motor system that, over time, can lead to functional impairments and contribute negatively to the ability to recover after brain damage. Unfortunately, there are still many questions surrounding the physiological mechanisms underlying these impairments. We examined cortico-spinal excitability and plasticity in a young cohort (age range: 19-31) and an elderly cohort (age range: 47-73) of healthy right-handed individuals using navigated transcranial magnetic stimulation (nTMS). Subjects were evaluated with a combination of physiological [motor evoked potentials (MEPs), motor threshold (MT), intracortical inhibition (ICI), intracortical facilitation (ICF), and silent period (SP)] and behavioral [reaction time (RT), pinch force, 9 hole peg task (HPT)] measures at baseline and following one session of low-frequency (1 Hz) navigated repetitive TMS (rTMS) to the right (non-dominant) hemisphere. In the young cohort, the inhibitory effect of 1 Hz rTMS was significantly in the right hemisphere and a significant facilitatory effect was noted in the unstimulated hemisphere. Conversely, in the elderly cohort, we report only a trend toward a facilitatory effect in the unstimulated hemisphere, suggesting reduced cortical plasticity and interhemispheric communication. To this effect, we show that significant differences in hemispheric cortico-spinal excitability were present in the elderly cohort at baseline, with significantly reduced cortico-spinal excitability in the right hemisphere as compared to the left hemisphere. A correlation analysis revealed no significant relationship between cortical thickness of the selected region of interest (ROI) and MEPs in either young or old subjects prior to and following rTMS. When combined with our preliminary results, further research into this topic could lead to the development of neurophysiological markers pertinent to the diagnosis, prognosis, and treatment of neurological diseases characterized by monohemispheric damage and lateralized motor deficits. PMID:24959141

Bashir, Shahid; Perez, Jennifer M; Horvath, Jared C; Pena-Gomez, Cleofe; Vernet, Marine; Capia, Anuhya; Alonso-Alonso, Miguel; Pascual-Leone, Alvaro

2014-01-01

199

Safety and tolerability of repetitive transcranial magnetic stimulation in patients with pathologic positive sensory phenomena: a review of literature  

PubMed Central

BACKGROUND Repetitive transcranial magnetic stimulation (rTMS) is emerging as a valuable therapeutic and diagnostic tool. rTMS appears particularly promising for disorders characterized by positive sensory phenomena attributable to alterations in sensory cortex excitability. Among these are tinnitus, auditory and visual hallucinations, and pain syndromes. OBJECTIVE Despite studies addressing rTMS efficacy in suppression of positive sensory symptoms, the safety of stimulation of potentially hyperexcitable cortex has not been fully addressed. We performed a systematic literature review and metanalysis to describe the rTMS safety profile in these disorders. METHODS Using the PubMed database, we performed an English-language literature search from January 1985 to April 2011 to review all pertinent publications. Per study, we noted and listed pertinent details. From these data we also calculated a crude per-subject risk for each adverse event. RESULTS 106 publications (n = 1815 subjects) were identified with patients undergoing rTMS for pathologic positive sensory phenomena. Adverse events associated with rTMS were generally mild and occurred in 16.7% of subjects. Seizure was the most serious adverse event, and occurred in three patients with a 0.16% crude per-subject risk. The second most severe adverse event involved aggravation of sensory phenomena, occurring in 1.54%. CONCLUSIONS The published data suggest rTMS for the treatment or diagnosis of pathologic positive sensory phenomena appears to be a relatively safe and well-tolerated procedure. However, published data are lacking in systematic reporting of adverse events, and safety risks of rTMS in these patient populations will have to be addressed in future prospective trials. PMID:22322098

Muller, Paul A; Pascual-Leone, Alvaro; Rotenberg, Alexander

2013-01-01

200

Low-Intensity Repetitive Transcranial Magnetic Stimulation Improves Abnormal Visual Cortical Circuit Topography and Upregulates BDNF in Mice  

PubMed Central

Repetitive transcranial magnetic stimulation (rTMS) is increasingly used as a treatment for neurological and psychiatric disorders. Although the induced field is focused on a target region during rTMS, adjacent areas also receive stimulation at a lower intensity and the contribution of this perifocal stimulation to network-wide effects is poorly defined. Here, we examined low-intensity rTMS (LI-rTMS)-induced changes on a model neural network using the visual systems of normal (C57Bl/6J wild-type, n = 22) and ephrin-A2A5?/? (n = 22) mice, the latter possessing visuotopic anomalies. Mice were treated with LI-rTMS or sham (handling control) daily for 14 d, then fluorojade and fluororuby were injected into visual cortex. The distribution of dorsal LGN (dLGN) neurons and corticotectal terminal zones (TZs) was mapped and disorder defined by comparing their actual location with that predicted by injection sites. In the afferent geniculocortical projection, LI-rTMS decreased the abnormally high dispersion of retrogradely labeled neurons in the dLGN of ephrin-A2A5?/? mice, indicating geniculocortical map refinement. In the corticotectal efferents, LI-rTMS improved topography of the most abnormal TZs in ephrin-A2A5?/? mice without altering topographically normal TZs. To investigate a possible molecular mechanism for LI-rTMS-induced structural plasticity, we measured brain derived neurotrophic factor (BDNF) in the visual cortex and superior colliculus after single and multiple stimulations. BDNF was upregulated after a single stimulation for all groups, but only sustained in the superior colliculus of ephrin-A2A5?/? mice. Our results show that LI-rTMS upregulates BDNF, promoting a plastic environment conducive to beneficial reorganization of abnormal cortical circuits, information that has important implications for clinical rTMS. PMID:25100609

Makowiecki, Kalina; Harvey, Alan R.; Sherrard, Rachel M.

2014-01-01

201

Task-related changes in intracortical inhibition assessed with paired- and triple-pulse transcranial magnetic stimulation.  

PubMed

Recent research has demonstrated a task-related modulation of postsynaptic intracortical inhibition within primary motor cortex for tasks requiring isolated (abduction) or synergistic (precision grip) muscle activation. The current study sought to investigate task-related changes in pre- and postsynaptic intracortical inhibition in motor cortex. In 13 young adults (22.5 ± 3.5 years), paired-pulse transcranial magnetic stimulation (TMS) was used to measure short- (SICI) and long-interval intracortical inhibition (LICI) (i.e. postsynaptic motor cortex inhibition) in first dorsal interosseous muscle, and triple-pulse TMS was used to investigate changes in SICI-LICI interactions (i.e. presynaptic motor cortex inhibition). These measurements were obtained at rest and during muscle activation involving isolated abduction of the index finger and during a precision grip using the index finger and thumb. SICI was reduced during abduction and precision grip compared with rest, with greater reductions during precision grip. The modulation of LICI during muscle activation depended on the interstimulus interval (ISI, 100 and 150 ms), but was not different between abduction and precision grip. For triple-pulse TMS, SICI was reduced in the presence of LICI at both ISIs in resting muscle (reflecting presynaptic motor cortex inhibition), but was only modulated at the 150 ms ISI during index finger abduction. Results suggest that synergistic contractions are accompanied by greater reductions in postsynaptic motor cortex inhibition than isolated contractions, but the contribution of presynaptic mechanisms to this disinhibition is limited. Furthermore, timing-dependent variations in LICI provide additional evidence that measurements using different ISIs may not represent activation of the same cortical process. PMID:25475354

Opie, George Mackenzie; Ridding, Michael C; Semmler, John G

2014-12-01

202

Synergistic effects of noradrenergic modulation with atomoxetine and 10 Hz repetitive transcranial magnetic stimulation on motor learning in healthy humans  

PubMed Central

Background Repetitive transcranial magnetic stimulation (rTMS) is able to induce changes in neuronal activity that outlast stimulation. The underlying mechanisms are not completely understood. They might be analogous to long-term potentiation or depression, as the duration of the effects seems to implicate changes in synaptic plasticity. Norepinephrine (NE) has been shown to play a crucial role in neuronal plasticity in the healthy and injured human brain. Atomoxetine (ATX) and other NE reuptake inhibitors have been shown to increase excitability in different systems and to influence learning processes. Thus, the combination of two facilitative interventions may lead to further increase in excitability and motor learning. But in some cases homeostatic metaplasticity might protect the brain from harmful hyperexcitability. In this study, the combination of 60 mg ATX and 10 Hz rTMS over the primary motor cortex was used to examine changes in cortical excitability and motor learning and to investigate their influence on synaptic plasticity mechanisms. Results The results of this double-blind placebo-controlled study showed that ATX facilitated corticospinal and intracortical excitability in motor cortex. 10 Hertz rTMS applied during a motor task was able to further increase intracortical excitability only in combination with ATX. In addition, only the combination of 10 Hz rTMS and ATX was capable of enhancing the total number of correct responses and reaction time significantly, indicating an interaction effect between rTMS and ATX without signs of homeostatic metaplasticity. Conclusion These results suggest that pharmacologically enhanced NE transmission and 10 Hz rTMS exert a synergistic effect on motor cortex excitability and motor learning in healthy humans. PMID:24690416

2014-01-01

203

Transcranial magnetic stimulation: potential treatment for co-occurring alcohol, traumatic brain injury and posttraumatic stress disorders.  

PubMed

Alcohol use disorder (AUD), mild traumatic brain injury (mTBI), and posttraumatic stress disorder (PTSD) commonly co-occur (AUD + mTBI + PTSD). These conditions have overlapping symptoms which are, in part, reflective of overlapping neuropathology. These conditions become problematic because their co-occurrence can exacerbate symptoms. Therefore, treatments must be developed that are inclusive to all three conditions. Repetitive transcranial magnetic stimulation (rTMS) is non-invasive and may be an ideal treatment for co-occurring AUD + mTBI + PTSD. There is accumulating evidence on rTMS as a treatment for people with AUD, mTBI, and PTSD each alone. However, there are no published studies to date on rTMS as a treatment for co-occurring AUD + mTBI + PTSD. This review article advances the knowledge base for rTMS as a treatment for AUD + mTBI + PTSD. This review provides background information about these co-occurring conditions as well as rTMS. The existing literature on rTMS as a treatment for people with AUD, TBI, and PTSD each alone is reviewed. Finally, neurobiological findings in support of a theoretical model are discussed to inform TMS as a treatment for co-occurring AUD + mTBI + PTSD. The peer-reviewed literature was identified by targeted literature searches using PubMed and supplemented by cross-referencing the bibliographies of relevant review articles. The existing evidence on rTMS as a treatment for these conditions in isolation, coupled with the overlapping neuropathology and symptomology of these conditions, suggests that rTMS may be well suited for the treatment of these conditions together. PMID:25422632

Herrold, Amy A; Kletzel, Sandra L; Harton, Brett C; Chambers, R Andrew; Jordan, Neil; Pape, Theresa Louise-Bender

2014-10-01

204

Transcranial magnetic stimulation: potential treatment for co-occurring alcohol, traumatic brain injury and posttraumatic stress disorders  

PubMed Central

Alcohol use disorder (AUD), mild traumatic brain injury (mTBI), and posttraumatic stress disorder (PTSD) commonly co-occur (AUD + mTBI + PTSD). These conditions have overlapping symptoms which are, in part, reflective of overlapping neuropathology. These conditions become problematic because their co-occurrence can exacerbate symptoms. Therefore, treatments must be developed that are inclusive to all three conditions. Repetitive transcranial magnetic stimulation (rTMS) is non-invasive and may be an ideal treatment for co-occurring AUD + mTBI + PTSD. There is accumulating evidence on rTMS as a treatment for people with AUD, mTBI, and PTSD each alone. However, there are no published studies to date on rTMS as a treatment for co-occurring AUD + mTBI + PTSD. This review article advances the knowledge base for rTMS as a treatment for AUD + mTBI + PTSD. This review provides background information about these co-occurring conditions as well as rTMS. The existing literature on rTMS as a treatment for people with AUD, TBI, and PTSD each alone is reviewed. Finally, neurobiological findings in support of a theoretical model are discussed to inform TMS as a treatment for co-occurring AUD + mTBI + PTSD. The peer-reviewed literature was identified by targeted literature searches using PubMed and supplemented by cross-referencing the bibliographies of relevant review articles. The existing evidence on rTMS as a treatment for these conditions in isolation, coupled with the overlapping neuropathology and symptomology of these conditions, suggests that rTMS may be well suited for the treatment of these conditions together. PMID:25422632

Herrold, Amy A.; Kletzel, Sandra L.; Harton, Brett C.; Chambers, R. Andrew; Jordan, Neil; Pape, Theresa Louise-Bender

2014-01-01

205

Comparison of Transcranial Magnetic Stimulation and Electroneuronography Between Bell's Palsy and Ramsay Hunt Syndrome in Their Acute Stages  

PubMed Central

Objective To examine the neurophysiologic status in patients with idiopathic facial nerve palsy (Bell's palsy) and Ramsay Hunt syndrome (herpes zoster oticus) within 7 days from onset of symptoms, by comparing the amplitude of compound muscle action potentials (CMAP) of facial muscles in electroneuronography (ENoG) and transcranial magnetic stimulation (TMS). Methods The facial nerve conduction study using ENoG and TMS was performed in 42 patients with Bell's palsy and 14 patients with Ramsay Hunt syndrome within 7 days from onset of symptoms. Denervation ratio was calculated as CMAP amplitude evoked by ENoG or TMS on the affected side as percentage of the amplitudes on the healthy side. The severity of the facial palsy was graded according to House-Brackmann facial grading scale (H-B FGS). Results In all subjects, the denervation ratio in TMS (71.53±18.38%) was significantly greater than the denervation ratio in ENoG (41.95±21.59%). The difference of denervation ratio between ENoG and TMS was significantly smaller in patients with Ramsay Hunt syndrome than in patients with Bell's palsy. The denervation ratio of ENoG or TMS did not correlated significantly with the H-B FGS. Conclusion In the electrophysiologic study for evaluation in patients with facial palsy within 7 days from onset of symptoms, ENoG and TMS are useful in gaining additional information about the neurophysiologic status of the facial nerve and may help to evaluate prognosis and set management plan. PMID:23525840

Hur, Dong Min; Lee, Young Hee; Kim, Sung Hoon; Park, Jung Mi; Kim, Ji Hyun; Yong, Sang Yeol; Shinn, Jong Mock; Oh, Kyung Joon

2013-01-01

206

Repeated transcranial magnetic stimulation prevents kindling-induced changes in electrophysiological properties of rat hippocampal CA1 pyramidal neurons.  

PubMed

The mechanisms underlying antiepileptic or antiepileptogenic effects of repeated transcranial magnetic stimulation (rTMS) are poorly understood. In this study, we investigated the effect of rTMS applied during rapid amygdala kindling on some electrophysiological properties of hippocampal CA1 pyramidal neurons. Male Wistar rats were kindled by daily electrical stimulation of the basolateral amygdala in a semi-rapid manner (12 stimulations/day) until they achieved stage-5 seizure. One group (kindled+rTMS (KrTMS)) of animals received rTMS (1Hz for 4min) 5min after termination of daily kindling stimulations. Twenty four hours following the last kindling stimulation electrophysiological properties of hippocampal CA1 pyramidal neurons were investigated using whole-cell patch-clamp technique. Amygdala kindling significantly depolarized the resting membrane potential and increased the input resistance, spontaneous firing activity, number of evoked spikes and half-width of the first evoked spike. Kindling also decreased the first-spike latency and amplitude significantly. Application of rTMS during kindling somehow prevented the development of seizures and protected CA1 pyramidal neurons of hippocampus against deleterious effect of kindling on both passive and active neuronal electrophysiological properties. Interestingly, application of rTMS alone enhanced the excitability of CA1 pyramidal neurons significantly. Based on the results of our study, it may be suggested that rTMS exerts its anticonvulsant effect, in part, through preventing the amygdala kindling-induced changes in electrophysiological properties of hippocampal CA1 pyramidal neurons. It seems that rTMS exerts protective effects on the neural circuits involved in spreading the seizures from the focus to other parts of the brain. PMID:25241070

Shojaei, A; Semnanian, S; Janahmadi, M; Moradi-Chameh, H; Firoozabadi, S M; Mirnajafi-Zadeh, J

2014-11-01

207

Acute and chronic effects of hypercalcaemia on cortical excitability as studied by 5 Hz repetitive transcranial magnetic stimulation  

PubMed Central

Abstract We designed the present study to disclose changes in cortical excitability in humans with hypercalcaemia, by delivering repetitive transcranial magnetic stimulation (rTMS) over the primary motor area (M1). In 22 patients with chronic hypercalcaemia related to primary hyperparathyroidism and 22 age-matched healthy subjects 5 Hz-rTMS was delivered at rest and during a sustained voluntary contraction of the target muscle. Changes in the resting motor threshold (RMT), motor evoked potential (MEP) amplitudes and cortical silent period (CSP) duration were measured and compared in patients and healthy controls. Two of the 22 patients were re-tested after parathyroidectomy when serum calcium had normalized. In a subgroup of healthy subjects, changes in the rTMS parameters were tested before and after acute hypercalcaemia. No significant difference between healthy normocalcaemic subjects and chronic hypercalcaemic patients was found in the RMT values and MEP amplitude and CSP duration evoked by the first stimulus of the trains. During the course of 5 Hz-rTMS trains, MEP size increased significantly less in patients with chronic hypercalcaemia than in healthy subjects, whereas the CSP duration lengthened to a similar extent in both groups. In the two patients studied after parathyroidectomy, rTMS elicited a normal MEP amplitude facilitation. Our findings indicate that acute hypercalcaemia significantly decreased the MEP amplitude facilitation. Given that 5 Hz-rTMS modulates cortical excitability through mechanisms resembling short-term synaptic enhancement, the reduction of MEP amplitude facilitation by hypercalcaemia may be related to Ca2+-dependent changes in synaptic plasticity. PMID:21300754

Iacovelli, Elisa; Gilio, Francesca; Mascia, Maria Lucia; Scillitani, Alfredo; Romagnoli, Elisabetta; Pichiorri, Floriana; Fucile, Sergio; Minisola, Salvatore; Inghilleri, Maurizio

2011-01-01

208

Differential effects of motor cortical excitability and plasticity in young and old individuals: a Transcranial Magnetic Stimulation (TMS) study  

PubMed Central

Aging is associated with changes in the motor system that, over time, can lead to functional impairments and contribute negatively to the ability to recover after brain damage. Unfortunately, there are still many questions surrounding the physiological mechanisms underlying these impairments. We examined cortico-spinal excitability and plasticity in a young cohort (age range: 19–31) and an elderly cohort (age range: 47–73) of healthy right-handed individuals using navigated transcranial magnetic stimulation (nTMS). Subjects were evaluated with a combination of physiological [motor evoked potentials (MEPs), motor threshold (MT), intracortical inhibition (ICI), intracortical facilitation (ICF), and silent period (SP)] and behavioral [reaction time (RT), pinch force, 9 hole peg task (HPT)] measures at baseline and following one session of low-frequency (1 Hz) navigated repetitive TMS (rTMS) to the right (non-dominant) hemisphere. In the young cohort, the inhibitory effect of 1 Hz rTMS was significantly in the right hemisphere and a significant facilitatory effect was noted in the unstimulated hemisphere. Conversely, in the elderly cohort, we report only a trend toward a facilitatory effect in the unstimulated hemisphere, suggesting reduced cortical plasticity and interhemispheric communication. To this effect, we show that significant differences in hemispheric cortico-spinal excitability were present in the elderly cohort at baseline, with significantly reduced cortico-spinal excitability in the right hemisphere as compared to the left hemisphere. A correlation analysis revealed no significant relationship between cortical thickness of the selected region of interest (ROI) and MEPs in either young or old subjects prior to and following rTMS. When combined with our preliminary results, further research into this topic could lead to the development of neurophysiological markers pertinent to the diagnosis, prognosis, and treatment of neurological diseases characterized by monohemispheric damage and lateralized motor deficits. PMID:24959141

Bashir, Shahid; Perez, Jennifer M.; Horvath, Jared C.; Pena-Gomez, Cleofe; Vernet, Marine; Capia, Anuhya; Alonso-Alonso, Miguel; Pascual-Leone, Alvaro

2014-01-01

209

Transcranial direct current stimulation (tDCS) produces localized and specific alterations in neurochemistry: a ¹H magnetic resonance spectroscopy study.  

PubMed

Transcranial direct current stimulation (tDCS) has been found to produce significant changes in behavior, including a large increase of learning and performance for a difficult visual perceptual task (Clark et al., NeuroImage 2010). The mechanisms by which tDCS produces these behavioral effects are currently uncertain. One hypothesis is that anodal tDCS leads to increased metabolic activity in the brain, which enhances cognitive and memory processes. Here we examined the neuronal mechanisms by which tDCS influences learning by measuring changes in brain metabolite concentrations using proton magnetic resonance spectroscopy (¹H MRS). As perception and learning can also influence neurochemistry, here we applied tDCS during rest. MRS data was obtained before and after 2.0 mA of anodal tDCS was applied for 30 min over electrode site P4, with the cathode placed on the contralateral arm. MRS data were acquired from the right parietal lobe beneath the anodal tDCS electrode, and from the homologous regions of the left hemisphere once before and once after tDCS. Significantly higher combined glutamate and glutamine levels were found in right parietal cortex, beneath the stimulating electrode, with non-significant increases in homologous regions of the opposite hemisphere. In addition, a significant interaction between hemispheres was found for tDCS effects on tNAA. These results suggest that changes in glutamatergic activity and tNAA may be related to the mechanisms by which tDCS influences learning and behavior. PMID:21683766

Clark, Vincent P; Coffman, Brian A; Trumbo, Michael C; Gasparovic, Charles

2011-08-01

210

Modulation of cortical excitability induced by repetitive transcranial magnetic stimulation: influence of timing and geometrical parameters and underlying mechanisms.  

PubMed

Transcranial magnetic stimulation (TMS) is a non-invasive brain stimulation technique that activates neurons via generation of brief pulses of high-intensity magnetic field. If these pulses are applied in a repetitive fashion (rTMS), persistent modulation of neural excitability can be achieved. The technique has proved beneficial in the treatment of a number of neurological and psychiatric conditions. However, the effect of rTMS on excitability and the other performance indicators shows a considerable degree of variability across different sessions and subjects. The frequency of stimulation has always been considered as the main determinant of the direction of excitability modulation. However, interactions exist between frequency and several other stimulation parameters that also influence the degree of modulation. In addition, the spatial interaction of the transient electric field induced by the TMS pulse with the cortical neurons is another contributor to variability. Consideration of all of these factors is necessary in order to improve the consistency of the conditioning effect and to better understand the outcomes of investigations with rTMS. These user-controlled sources of variability are discussed against the background of the mechanisms that are believed to drive the excitability changes. The mechanism behind synaptic plasticity is commonly accepted as the driver of sustained excitability modulation for rTMS and indeed, plasticity and rTMS share many characteristics, but definitive evidence is lacking for this. It is more likely that there is a multiplicity of mechanisms behind the action of rTMS. The different mechanisms interact with each other and this will contribute to the variability of rTMS-induced excitability changes. This review investigates the links between rTMS and synaptic plasticity, describes their similarities and differences, and highlights a neglected contribution of the membrane potential. In summary, the principal aims of this review are (i) to discuss the different experimental and subject-related factors that contribute to the variability of excitability modulation induced by rTMS, and (ii) to discuss a generalized underlying mechanism for the excitability modulation. PMID:21056619

Pell, Gaby S; Roth, Yiftach; Zangen, Abraham

2011-01-01

211

Chronic cerebro-spinal venous insufficiency: report of transcranial magnetic stimulation follow-up study in a patient with multiple sclerosis.  

PubMed

The pyramidal pathway is frequently affected early on in multiple sclerosis (MS) and impaired motor performance is a major cause of disability. Pyramidal tract function can be assessed using transcranial magnetic stimulation (TMS). TMS supports the diagnosis of MS, detecting corticospinal tract involvement and monitoring its course with or without treatment. It has been never investigated whether any relationship exists between the TMS outcome measure and minimally invasive treatment of multiple severe extracranial stenosis, affecting the principal ce rebrospinal venous segments in MS patients. We report the clinical and transcranial magnetic stimulation follow-up of a patient during a relapse in relapsing-remitting MS. She underwent percutaneous balloon angioplasty of the associated chronic cerebrospinal venous insufficiency (CCSVI), due to membranous obstruction of the proximal azygous vein, with severe stenosis of the left internal jugular vein. Treatment of the associated CCSVI made a parallel improvement in both clinical and neurophysiological parameters, allowing us to avoid high dose steroid therapy. The relationship between the clinical and neurophysiological course on the one hand, and haemodynamic correction of the associated CCSVI on the other, calls for further exploration on a wider number of patients. The impact of CCSVI on the different neuro-physiological parameters has not been fully estimated, but the intriguing case here reported suggests that it may be greater than previously assumed. The demonstration of a modification of the cerebrovenous function with both clinical manifestation and via TMS suggests that the hampered cerebral venous return may contribute to the clinical course of MS. PMID:20351675

Plasmati, R; Pastorelli, F; Fini, N; Salvi, F; Galeotti, R; Zamboni, P

2010-04-01

212

Randomized controlled trial of four protocols of repetitive transcranial magnetic stimulation for treating the negative symptoms of schizophrenia  

PubMed Central

Background The negative symptoms of schizophrenia are not effectively treated with antipsychotic medications. Repetitive transcranial magnetic stimulation (rTMS) is an alternative approach that may be more effective in treating negative symptoms, but there has been little research comparing the effectiveness of different rTMS stimulation protocols. Objective Compare the effect of four different rTMS protocols in the treatment of the negative symptoms of schizophrenia. Methods Ninety-six patients with schizophrenia who had prominent negative symptoms were randomly assigned to four treatment groups: 10 Hz, 20 Hz, theta burst stimulation (TBS), and mock rTMS (i.e., the control group). In the first three groups, the left dorsolateral prefrontal cortex was stimulated at 80% of the motor threshold five times per week for four weeks. Before and after the treatment, evaluators who were blind to the group assignment of patients administered the Positive and Negative Syndrome Scale (PANSS), the Scale for the Assessment of Negative Symptoms (SANS) and the Treatment Emergent Symptom Scale (TESS). Results Three of the 96 patients dropped out during the trial (two from the control group and one from the 20 Hz group). Compared to the control group, after 4 weeks of rTMS treatment all three treatment groups had lower scores on the PANSS negative symptom subscale, the PANSS general psychopathology subscale, and the SANS. The TBS group had significantly larger reductions in these scores than the 10 Hz group and the 20 Hz group, but there were no significant differences between the 10 Hz and 20 Hz groups. There were no pre- versus post-treatment differences in the PANSS positive symptom subscale scores between the four groups. No serious adverse events occurred and there were no statistically significant differences in the TESS scores across the four groups. Conclusions We find that rTMS, particularly the TBS stimulation protocol for rTMS, is a safe and effective treatment method for patients with schizophrenia who have prominent negative symptoms. Longitudinal studies with large samples are needed to optimize the rTMS treatment, to identify the stimulation protocol, duration, intensity and treatment interval that provides the best therapeutic result at the lowest risk to the patient. PMID:25114477

ZHAO, Suhua; KONG, Jiehua; LI, Shuling; TONG, Zishun; YANG, Chanjuan; ZHONG, Huaqing

2014-01-01

213

Resting and active motor thresholds versus stimulus–response curves to determine transcranial magnetic stimulation intensity in quadriceps femoris  

PubMed Central

Background Transcranial magnetic stimulation (TMS) is a widely-used investigative technique in motor cortical evaluation. Recently, there has been a surge in TMS studies evaluating lower-limb fatigue. TMS intensity of 120-130% resting motor threshold (RMT) and 120% active motor threshold (AMT) and TMS intensity determined using stimulus–response curves during muscular contraction have been used in these studies. With the expansion of fatigue research in locomotion, the quadriceps femoris is increasingly of interest. It is important to select a stimulus intensity appropriate to evaluate the variables, including voluntary activation, being measured in this functionally important muscle group. This study assessed whether selected quadriceps TMS stimulus intensity determined by frequently employed methods is similar between methods and muscles. Methods Stimulus intensity in vastus lateralis, rectus femoris and vastus medialis muscles was determined by RMT, AMT (i.e. during brief voluntary contractions at 10% maximal voluntary force, MVC) and maximal motor-evoked potential (MEP) amplitude from stimulus–response curves during brief voluntary contractions at 10, 20 and 50% MVC at different stimulus intensities. Results Stimulus intensity determined from a 10% MVC stimulus–response curve and at 120 and 130% RMT was higher than stimulus intensity at 120% AMT (lowest) and from a 50% MVC stimulus–response curve (p??0.05). Conclusions Similar optimal stimulus intensity and maximal MEP amplitudes at 20 and 50% MVC and the minimal risk of residual fatigue at 20% MVC suggest that a 20% MVC stimulus–response curve is appropriate for determining TMS stimulus intensity in the quadriceps femoris. The higher selected stimulus intensities at 120-130% RMT have the potential to cause increased coactivation and discomfort and the lower stimulus intensity at 120% AMT may underestimate evoked responses. One muscle may also act as a surrogate in determining optimal quadriceps femoris stimulation intensity. PMID:24655366

2014-01-01

214

Functional Dopaminergic Neurons in Substantia Nigra are Required for Transcranial Magnetic Stimulation-Induced Motor Plasticity.  

PubMed

Repetitive magnetic stimulation (rTMS), including theta burst stimulation (TBS), is capable of modulating motor cortical excitability through plasticity-like mechanisms and might have therapeutic potential for Parkinson's disease (PD). An animal model would be helpful for elucidating the mechanism of rTMS that remain unclear and controversial. Here, we have established a TMS model in rat and applied this model to study the impact of substantia nigra dopamine neuron on TBS-induced motor plasticity in PD rats. In parallel with human results, continuous TBS (cTBS) successfully suppressed motor evoked potentials (MEPs), while MEPs increased after intermittent TBS (iTBS) in healthy rats. We then tested the effect of iTBS in early and advanced 6-hydroxydopamine (6-OHDA)-lesioned PD. Moreover, dopaminergic neurons in substantia nigra and rotation behavior were assessed to correlate with the amount of iTBS-induced plasticity. In results, iTBS-induced potentiation was reduced in early PD rats and was absent in advanced PD rats. Such reduction in plasticity strongly correlated with the dopaminergic cell loss and the count of rotation in PD rats. In conclusion, we have established a TMS PD rat model. With the help of this model, we confirmed the loss of domaninergic neurons in substantia nigra resulting in reduced rTMS-induced motor plasticity in PD. PMID:24451657

Hsieh, Tsung-Hsun; Huang, Ying-Zu; Rotenberg, Alexander; Pascual-Leone, Alvaro; Chiang, Yung-Hsiao; Wang, Jia-Yi; Chen, Jia-Jin J

2014-01-22

215

Deep-brain magnetic stimulation promotes adult hippocampal neurogenesis and alleviates stress-related behaviors in mouse models for neuropsychiatric disorders  

PubMed Central

Background Repetitive Transcranial Magnetic Stimulation (rTMS)/ Deep-brain Magnetic Stimulation (DMS) is an effective therapy for various neuropsychiatric disorders including major depression disorder. The molecular and cellular mechanisms underlying the impacts of rTMS/DMS on the brain are not yet fully understood. Results Here we studied the effects of deep-brain magnetic stimulation to brain on the molecular and cellular level. We examined the adult hippocampal neurogenesis and hippocampal synaptic plasticity of rodent under stress conditions with deep-brain magnetic stimulation treatment. We found that DMS promotes adult hippocampal neurogenesis significantly and facilitates the development of adult new-born neurons. Remarkably, DMS exerts anti-depression effects in the learned helplessness mouse model and rescues hippocampal long-term plasticity impaired by restraint stress in rats. Moreover, DMS alleviates the stress response in a mouse model for Rett syndrome and prolongs the life span of these animals dramatically. Conclusions Deep-brain magnetic stimulation greatly facilitates adult hippocampal neurogenesis and maturation, also alleviates depression and stress-related responses in animal models. PMID:24512669

2014-01-01

216

Changes in regional cerebral blood flow after repetitive transcranial magnetic stimulation of the left dorsolateral prefrontal cortex in treatment-resistant depression.  

PubMed

High-frequency repetitive transcranial magnetic stimulation (rTMS) of the left dorsolateral prefrontal cortex is effective in treatment-resistant depression, although its mechanism is still not completely elucidated. To clarify the neuroanatomical alteration of function elicited by rTMS, single photon emission computed tomography (SPECT) with (99m)Tc-ECD was performed on 12 male inpatients with treatment-resistant unipolar depression before and after high-frequency rTMS of the left dorsolateral prefrontal cortex. These results suggest that the manifestation of the antidepressant effect of high-frequency rTMS is associated with changes in the neuroanatomical function of the left dorsolateral prefrontal cortex as well as of the limbic-paralimbic region, including the ipsilateral subgenual cingulate, and the basal ganglia. PMID:18305287

Kito, Shinsuke; Fujita, Kenichi; Koga, Yoshihiko

2008-01-01

217

Magnetic reconnection associated fluctuations in the deep magnetotail: ARTEMIS results  

NASA Astrophysics Data System (ADS)

On the basis of ARTEMIS two-probe mission magnetic reconnection (MR) outflow associated magnetic fluctuations and turbulence are analyzed on 19 February 2011. In the deep-tail, at distances between X = 45 - 51 RE, evidence for reconnection associated plasma sheet thinning was found, accompanied by heating of the plasma sheet. Correlated flow and field reversals and the large-scale Hall-effect signatures indicated the presence of the reconnection X-line. Within fast reconnection plasma outflows, magnetic fluctuations exhibit the same spectral scaling features and kinked spectra as magnetic fluctuations in the solar wind or in various parts of geospace. It was shown that the proton scale magnetic fluctuations are constrained by oblique firehose, proton cyclotron and mirror instability thresholds. For parallel plasma ?|| > 1, where the thresholds converge, perpendicular magnetic fluctuations are enhanced. Magnetic compressibility decreases with the distance to the neutral sheet, however, near the instability thresholds it is comparable to the values obtained in the solar wind.

Vörös, Z.

2011-11-01

218

Head-to-Head Comparison of Transcranial Random Noise Stimulation, Transcranial AC Stimulation, and Transcranial DC Stimulation for Tinnitus  

PubMed Central

Tinnitus is the perception of a sound in the absence of an external sound stimulus. This phantom sound has been related to plastic changes and hyperactivity in the auditory cortex. Different neuromodulation techniques such as transcranial magnetic stimulation and transcranial direct current stimulation (tDCS) have been used in an attempt to modify local and distant neuroplasticity as to reduce tinnitus symptoms. Recently, two techniques of pulsed electrical stimulation using weak electrical currents – transcranial alternating current stimulation (tACS) and transcranial random noise stimulation (tRNS) – have also shown significant neuromodulatory effects. In the present study we conducted the first head-to-head comparison of three different transcranial electrical stimulation (tES) techniques, namely tDCS, tACS, and tRNS in 111 tinnitus patients by placing the electrodes overlying the auditory cortex bilaterally. The results demonstrated that tRNS induced the larger transient suppressive effect on the tinnitus loudness and the tinnitus related distress as compared to tDCS and tACS. Both tDCS and tACS induced small and non-significant effects on tinnitus symptoms, supporting the superior effects of tRNS as a method for tinnitus suppression. PMID:24391599

Vanneste, Sven; Fregni, Felipe; De Ridder, Dirk

2013-01-01

219

Occurrence of Magnetic Reconnection in the Deep Magnetotail: ARTEMIS Results  

NASA Astrophysics Data System (ADS)

Using two-probe ARTEMIS magnetic field and plasma measurements we have accomplished a survey of the occurrence of magnetic reconnection signatures in the distant magnetotail between October 2010 and June 2011. We have considered highly accelerated electron and fast bulk plasma flow events during ARTEMIS tail crossings. Our findings suggest that the deep-tail region between -60{R}E < X({GSM}) < -40{R}E is rather active. Fourteen events have been found exhibiting signatures of magnetic reconnection occurrence during 29 days of plasma sheet crossings. Comparisons with mid-tail surveys of reconnection statistics indicate that the deep-tail region can play a significant role in global magnetosphere dynamics.

Vörös, Zoltán; Runov, Andrei; Kendl, Alexander

220

Transcranial stimulation and cognition.  

PubMed

Noninvasive brain stimulation (NIBS) is a unique method for studying cognitive function. For the study of cognition, NIBS has gained popularity as a complementary method to functional neuroimaging. By bypassing the correlative approaches of standard imaging techniques, it is possible to establish a putative relationship between brain cognition. In fact, functional neuroimaging data cannot demonstrate the actual role of a particular cortical activation in a specific function because an activated area may simply be correlated with task performance, rather than being responsible for it. NIBS can induce a temporary modification of performance only if the stimulated area is causally engaged in the task. In analogy with lesion studies, NIBS can provide information about where and when a particular process occurs. Based on this assumption, NIBS has been used in many different cognitive domains. However, one of the most interesting questions in neuroscience may not be where and when, but how cognitive activity occurs. Beyond localization approaches, NIBS can be employed to study brain mechanisms. NIBS techniques have the potential to influence behavior transiently by altering neuronal activity, which may have facilitatory or inhibitory behavioral effects. NIBS techniques include transcranial magnetic stimulation (TMS) and transcranial electrical stimulation (tES). TMS has been shown transiently to modulate neural excitability in a manner that is dependent mainly on the timing and frequency of stimulation (high versus low). The mechanism underlying tES is a change in neuronal membrane potentials that appears to be dependent mainly on the direction of current flow (anodal versus cathodal). Nevertheless, the final effects induced by TMS or tES depend on many technical parameters used during stimulation, such as the intensity of stimulation, coil orientation, site of the reference electrode, and time of application. Moreover, an important factor is the possible interactions between these factors and the physiological and cognitive state of the subject. To use NIBS in cognition, it is important to understand not only how NIBS functions but also the brain mechanisms being studied and the features of the area of interest. To describe better the advanced knowledge provided by NIBS in cognition, we will treat each NIBS technique separately and underline the related hypotheses beyond applications. PMID:24112935

Miniussi, Carlo; Ruzzoli, Manuela

2013-01-01

221

A pilot study of the use of EEG-based synchronized Transcranial Magnetic Stimulation (sTMS) for treatment of Major Depression  

PubMed Central

Background Repetitive Transcranial Magnetic Stimulation (rTMS) is an effective treatment for Major Depressive Disorder (MDD), and is based upon delivery of focal high-energy pulses of electromagnetic stimulation. We postulated that delivery of rTMS at the subject’s individual alpha frequency (synchronized TMS, or sTMS) would achieve efficacy with lower energy of stimulation. We developed a device that rotates neodymium cylindrical magnets at three locations along the midline above the subject’s scalp to impart low-energy, sinusoidal-waveform magnetic brain stimulation over a broad area, and performed this efficacy study. Method Fifty-two subjects with MDD were enrolled in a randomized, sham controlled, double-blind treatment study (Trial Registration: NCT01683019). Forty-six subjects were included in the final analysis. Most subjects received concurrent antidepressant medications that remained unchanged during the study. Subjects were randomized to three treatment groups: 1) active sTMS with a fixed frequency at the subject’s alpha frequency; 2) active sTMS with a random stimulus frequency that varied between 8 Hz and 13 Hz; and, 3) sham sTMS. 20 half-hour sTMS sessions were administered 5 days per week for 4 weeks. Results Subjects with either fixed or random frequency active sTMS had statistically significantly greater percentage reduction in depression severity compared to sham (48.5% vs. 19.3%, respectively; p = 0.001). No significant difference was found between fixed and random groups (p = 0.30). No significant side effects were reported. Conclusions These results suggest that sTMS may be an effective treatment for MDD. PMID:24438321

2014-01-01

222

Mechanism of functional recovery after repetitive transcranial magnetic stimulation (rTMS) in the subacute cerebral ischemic rat model: neural plasticity or anti-apoptosis?  

PubMed

Repetitive transcranial magnetic stimulation (rTMS) has been studied increasingly in recent years to determine whether it has a therapeutic benefit on recovery after stroke. However, the underlying mechanisms of rTMS in stroke recovery remain unclear. Here, we evaluated the effect of rTMS on functional recovery and its underlying mechanism by assessing proteins associated with neural plasticity and anti-apoptosis in the peri-lesional area using a subacute cerebral ischemic rat model. Twenty cerebral ischemic rats were randomly assigned to the rTMS or the sham group at post-op day 4. A total of 3,500 impulses with 10 Hz frequency were applied to ipsilesional cortex over a 2-week period. Functional outcome was measured before (post-op day 4) and after rTMS (post-op day 18). The rTMS group showed more functional improvement on the beam balance test and had stronger Bcl-2 and weaker Bax expression on immunohistochemistry compared with the sham group. The expression of NMDA and MAP-2 showed no significant difference between the two groups. These results suggest that rTMS in subacute cerebral ischemia has a therapeutic effect on functional recovery and is associated with an anti-apoptotic mechanism in the peri-ischemic area rather than with neural plasticity. PMID:21904929

Yoon, Kyung Jae; Lee, Yong-Taek; Han, Tai Ryoon

2011-10-01

223

Patients with a major depressive episode responding to treatment with repetitive transcranial magnetic stimulation (rTMS) are resistant to the effects of rapid tryptophan depletion.  

PubMed

Repetitive transcranial magnetic stimulation (rTMS) appears to be efficacious in the treatment of major depression based on the results of controlled studies, but little is known about its antidepressant mechanism of action. Mood sensitivity following rapid tryptophan depletion (RTD) has been demonstrated in depressed patients responding to SSRI antidepressants and phototherapy, but not in responders to electroconvulsive therapy (ECT). We sought to study the effects of RTD in patients with major depression responding to a course of treatment with rTMS. Twelve subjects treated successfully with rTMS monotherapy underwent both RTD and sham depletion in a double-blind crossover design. Depressive symptoms were assessed using both a modified Hamilton Depression Rating Scale (HDRS) and Beck Depression Inventory (BDI). The differential change in depression scores across the procedures was compared. No significant difference in mood symptoms was noted between RTD and the sham-depletion procedure on either continuous measures of depression, or in the proportions of subjects that met predefined criteria for a significant degree of mood worsening. Responders to rTMS are resistant to the mood perturbing effects of RTD. This suggests that rTMS does not depend on the central availability of serotonin to exert antidepressant effects in major depression. PMID:17131353

O'Reardon, John P; Cristancho, Pilar; Pilania, Pramod; Bapatla, Kiran B; Chuai, Shaokun; Peshek, Andrew D

2007-01-01

224

Repetitive Transcranial Magnetic Stimulation Ameliorates Anxiety-Like Behavior and Impaired Sensorimotor Gating in a Rat Model of Post-Traumatic Stress Disorder  

PubMed Central

Background Repetitive transcranial magnetic stimulation (rTMS) has been employed for decades as a non-pharmacologic treatment for post-traumatic stress disorder (PTSD). Although a link has been suggested between PTSD and impaired sensorimotor gating (SG), studies assessing the effects of rTMS against PTSD or PTSD with impaired SG are scarce. Aim To assess the benefit of rTMS in a rat model of PTSD. Methods Using a modified single prolonged stress (SPS&S) rat model of PTSD, behavioral parameters were acquired using open field test (OFT), elevated plus maze test (EPMT), and prepulse inhibition trial (PPI), with or without 7 days of high frequency (10Hz) rTMS treatment of SPS&S rats. Results Anxiety-like behavior, impaired SG and increased plasma level of cortisol were observed in SPS&S animals after stress for a prolonged time. Interestingly, rTMS administered immediately after stress prevented those impairment. Conclusion Stress-induced anxiety-like behavior, increased plasma level of cortisol and impaired PPI occur after stress and high-frequency rTMS has the potential to ameliorate this behavior, suggesting that high frequency rTMS should be further evaluated for its use as a method for preventing PTSD. PMID:25659132

Wang, Hua-ning; Bai, Yuan-han; Chen, Yun-chun; Zhang, Rui-guo; Wang, Huai-hai; Zhang, Ya-hong; Gan, Jing-li; Peng, Zheng-wu; Tan, Qing-rong

2015-01-01

225

The effects of high-frequency repetitive transcranial magnetic stimulation (rTMS) on negative symptoms of schizophrenia and the follow-up study.  

PubMed

In this double-blind, randomized controlled study, we assessed the therapeutic effects of high-frequency left dorsolateral prefrontal cortex (DLPFC) repetitive transcranial magnetic stimulation (rTMS) on negative symptoms of schizophrenia. For the study, 117 patients with prominent negative symptoms were randomized to a 20-day course of either active rTMS applied to the left DLPFC (n=78) or sham rTMS (n=39). The primary outcome measures were the Positive and Negative Symptom Scale (PANSS) and the Scale for the Assessment of Negative Symptoms (SANS). Secondary outcomes included the Clinical Global Impressions Scale (CGI) and the Udvalg for Kliniske Under sogelser (UKU) Side Effect Rating Scale. We found that treatment with high-frequency rTMS for 6weeks significantly improved negative symptoms in the active group as compared to the sham group. However, active rTMS was not correlated with significant improvement in the CGI severity of illness scale (CGI-S). The improvement of negative symptoms persisted to the 24-week follow-up assessment. These results indicate that there is a lasting beneficial effect of rTMS on negative symptoms in absence of decrease in CGI scores. We conclude that rTMS may serve as a relatively noninvasive treatment that alleviates negative symptoms in patients with schizophrenia. PMID:25449864

Quan, Wen Xiang; Zhu, Xiao Lin; Qiao, Hong; Zhang, Wu Fang; Tan, Shu Ping; Zhou, Dong Feng; Wang, Xiang Qun

2015-01-01

226

A review of the effects of hypoxia, sleep deprivation and transcranial magnetic stimulation on EEG activity in humans: challenges for drug discovery for Alzheimer's disease.  

PubMed

Different kinds of challenge can alter cognitive process and electroencephalographic (EEG) rhythms in humans. This can provide an alternative paradigms to evaluate treatment effects in drug discovery. Here, we report recent findings on the effects of challenges represented by sleep deprivation (SD), transient hypoxia, and transcranial magnetic stimulation (TMS) in healthy volunteers on cognitive processes and EEG rhythms to build a knowledge platform for novel research for drug discovery in AD Alzheimer's disease (AD). Sleep pressure enhanced frontal delta rhythms (< 4 Hz) during the night, while SD increased slow rhythms in the theta range (4-7 Hz), and reduced resting state alpha rhythms (8-12 Hz) after the following day. Furthermore, SD transiently affected cognitive performance. In contrast, transient experimental hypoxia induced abnormal posterior resting state delta and alpha rhythms in healthy volunteers that resemble the abnormal EEG rhythms typically recorded in AD patients. However, the relationship between the cognitive and EEG effects of such challenges is poorly understood. TMS reversibly interfered with higher brain functions during EEG recordings, but few studies have investigated the relationship between the cognitive and EEG effects of TMS. In conclusion, SD is the most mature challenge model for testing new drugs for AD. Future investigation is needed to better understand the opportunities offered by TMS and hypoxia challenges. PMID:24635844

Babiloni, Claudio; Del Percio, Claudio; Lizio, Roberta; Infarinato, Francesco; Blin, Olivier; Bartres-Faz, David; Dix, Sophie L; Bentivoglio, Marina; Soricelli, Andrea; Bordet, Regis; Rossini, Paolo M; Richardson, Jill C

2014-01-01

227

The use of magnetic resonance spectroscopy as a tool for the measurement of bi-hemispheric transcranial electric stimulation effects on primary motor cortex metabolism.  

PubMed

Transcranial direct current stimulation (tDCS) is a neuromodulation technique that has been increasingly used over the past decade in the treatment of neurological and psychiatric disorders such as stroke and depression. Yet, the mechanisms underlying its ability to modulate brain excitability to improve clinical symptoms remains poorly understood. To help improve this understanding, proton magnetic resonance spectroscopy ((1)H-MRS) can be used as it allows the in vivo quantification of brain metabolites such as ?-aminobutyric acid (GABA) and glutamate in a region-specific manner. In fact, a recent study demonstrated that (1)H-MRS is indeed a powerful means to better understand the effects of tDCS on neurotransmitter concentration. This article aims to describe the complete protocol for combining tDCS (NeuroConn MR compatible stimulator) with (1)H-MRS at 3 T using a MEGA-PRESS sequence. We will describe the impact of a protocol that has shown great promise for the treatment of motor dysfunctions after stroke, which consists of bilateral stimulation of primary motor cortices. Methodological factors to consider and possible modifications to the protocol are also discussed. PMID:25490453

Tremblay, Sara; Beaulé, Vincent; Proulx, Sébastien; Lafleur, Louis-Philippe; Doyon, Julien; Marja?ska, Ma?gorzata; Théoret, Hugo

2014-01-01

228

Distinctive patterns of cortical excitability to transcranial magnetic stimulation in obstructive sleep apnea syndrome, restless legs syndrome, insomnia, and sleep deprivation.  

PubMed

Altered responses to transcranial magnetic stimulation (TMS) in obstructive sleep apnea syndrome (OSAS), restless legs syndrome (RLS), insomnia, and sleep-deprived healthy subjects have been reported. We have reviewed the relevant literature in order to identify eventual distinctive electrocortical profiles based on single and paired-pulse TMS, sensorimotor modulation, plasticity-related and repetitive TMS measures. Although obtained from heterogeneous studies, the detected changes might be the result of the different pathophysiological substrates underlying OSAS, RLS, insomnia and sleep deprivation rather than reflect the general effect of non-specific sleep loss and instability. OSAS tends to exhibit an increased motor cortex inhibition, which is reduced in RLS; intracortical excitability seems to be in favor of an "activating" profile in chronic insomnia and in sleep-deprived healthy individuals. Abnormal plasticity-related TMS phenomena have been demonstrated in OSAS and RLS. This review provides a perspective of TMS techniques by further understanding the role of neurotransmission pathways and plastic remodeling of neuronal networks involved in common sleep disorders. TMS might be considered a valuable tool in the assessment of sleep disorders, the evaluation of the effect of therapy and the design of non-pharmacological approaches. PMID:24849846

Lanza, Giuseppe; Cantone, Mariagiovanna; Lanuzza, Bartolo; Pennisi, Manuela; Bella, Rita; Pennisi, Giovanni; Ferri, Raffaele

2015-02-01

229

Comparing the effects of repetitive transcranial magnetic stimulation and electroconvulsive therapy in the treatment of depression: a systematic review and meta-analysis.  

PubMed

Electroconvulsive therapy (ECT) is the longest standing psychiatric treatment available and has unequivocal benefit in severe depression. However this treatment comes with a number of side effects such as memory impairment. On the other hand, Repetitive Transcranial Magnetic Stimulation (rTMS) is a relatively new form of treatment which has been shown to be efficacious in patients suffering from a number of psychopathologies, including severe depression, with few reported side effects. Due to its potential therapeutic efficacy and lack of side effects, rTMS has gained traction in the treatment of depression, with a number of authors keen to see it take over from ECT. However, it is not clear whether rTMS represents a therapeutic alternative to ECT. This meta-analysis will therefore compare the "gold standard" treatment for severe depression, with the relatively new but promising rTMS. A literature search will be performed with the intention to include all randomised clinical trials. The null hypothesis is that there is no difference in the antidepressant efficacy between the two types of treatment modalities. Statistical analysis of Hamilton Depression Rating Scale (HDRS) scores will be performed. PMID:25143831

Micallef-Trigona, Beppe

2014-01-01

230

Low-frequency, Repetitive Transcranial Magnetic Stimulation for the Treatment of Patients with Posttraumatic Stress Disorder: a Double-blind, Sham-controlled Study  

PubMed Central

Objective Several studies have suggested that repetitive transcranial magnetic stimulation (rTMS) of the right prefrontal cortex may be useful in the treatment of posttraumatic stress disorder (PTSD). The aim of this study was to compare the effect of rTMS on the right prefrontal cortex with that of sham stimulation among patients with PTSD. Methods In total, 18 patients with PTSD were randomly assigned to the 1-Hz low-frequency rTMS group or the sham group for 3 weeks. Primary efficacy measures were the Clinician-Administered PTSD Scale (CAPS) and its subscales, assessed at baseline and at 2, 4, and 8 weeks. Results All CAPS scores improved significantly over the study period. We found significant differences in the re-experiencing scores (F=7.47, p=0.004) and total scores (F=6.45, p=0.008) on the CAPS. The CAPS avoidance scores showed a trend toward significance (F=2.74, p=0.055), but no significant differences in the CAPS hyperarousal scores were observed. Conclusion The present study showed low-frequency rTMS to be an effective and tolerable option for the treatment of PTSD. Trials using variable indices of rTMS to the right prefrontal cortex and explorations of the differences in the effects on specific symptom clusters may be promising avenues of research regarding the use of rTMS for PTSD. PMID:24023554

Nam, Dong-Hyun; Pae, Chi-Un

2013-01-01

231

Functional Interaction between Right Parietal and Bilateral Frontal Cortices during Visual Search Tasks Revealed Using Functional Magnetic Imaging and Transcranial Direct Current Stimulation  

PubMed Central

The existence of a network of brain regions which are activated when one undertakes a difficult visual search task is well established. Two primary nodes on this network are right posterior parietal cortex (rPPC) and right frontal eye fields. Both have been shown to be involved in the orientation of attention, but the contingency that the activity of one of these areas has on the other is less clear. We sought to investigate this question by using transcranial direct current stimulation (tDCS) to selectively decrease activity in rPPC and then asking participants to perform a visual search task whilst undergoing functional magnetic resonance imaging. Comparison with a condition in which sham tDCS was applied revealed that cathodal tDCS over rPPC causes a selective bilateral decrease in frontal activity when performing a visual search task. This result demonstrates for the first time that premotor regions within the frontal lobe and rPPC are not only necessary to carry out a visual search task, but that they work together to bring about normal function. PMID:24705681

Ellison, Amanda; Ball, Keira L.; Moseley, Peter; Dowsett, James; Smith, Daniel T.; Weis, Susanne; Lane, Alison R.

2014-01-01

232

Magnetic resonance imaging safety of deep brain stimulator devices.  

PubMed

Magnetic resonance imaging (MRI) has become the standard of care for the evaluation of different neurological disorders of the brain and spinal cord due to its multiplanar capabilities and excellent soft tissue resolution. With the large and increasing population of patients with implanted deep brain stimulation (DBS) devices, a significant proportion of these patients with chronic neurological diseases require evaluation of their primary neurological disease processes by MRI. The presence of an implanted DBS device in a magnetic resonance environment presents potential hazards. These include the potential for induction of electrical currents or heating in DBS devices, which can result in neurological tissue injury, magnetic field-induced device migration, or disruption of the operational aspects of the devices. In this chapter, we review the basic physics of potential interactions of the MRI environment with implanted DBS devices, summarize results from phantom studies and clinical series, and discuss present recommendations for safe MRI in patients with implanted DBS devices. PMID:24112886

Oluigbo, Chima O; Rezai, Ali R

2013-01-01

233

Repetitive Transcranial Magnetic Stimulation Promotes Neural Stem Cell Proliferation via the Regulation of MiR-25 in a Rat Model of Focal Cerebral Ischemia  

PubMed Central

Repetitive transcranial magnetic stimulation (rTMS) has increasingly been studied over the past decade to determine whether it has a therapeutic benefit on focal cerebral ischemia. However, the underlying mechanism of rTMS in this process remains unclear. In the current study, we investigated the effects of rTMS on the proliferation of adult neural stem cells (NSCs) and explored microRNAs (miRNAs) that were affected by rTMS. Our data showed that 10 Hz rTMS significantly increased the proliferation of adult NSCs after focal cerebral ischemia in the subventricular zone (SVZ), and the expression of miR-25 was obviously up-regulated in the ischemic cortex after rTMS. p57, an identified miR-25 target gene that regulates factors linked to NSC proliferation, was also evaluated, and it exhibited down-regulation. To further verify the role of miR-25, rats were injected with a single dose of antagomir-25 and were subjected to focal cerebral ischemia followed by rTMS treatment. The results confirmed that miR-25 could be repressed specifically and could drive the up-regulation of its target gene (p57), which resulted in the inhibition of adult NSC proliferation in the SVZ after rTMS. Thus, our studies strongly indicated that 10 Hz rTMS can promote the proliferation of adult NSCs in the SVZ after focal cerebral ischemia by regulating the miR-25/p57 pathway. PMID:25302788

Zhang, Jinghui; Zhao, Xiuxiu; Lou, Jicheng; Chen, Hong; Huang, Xiaolin

2014-01-01

234

Preconditioning repetitive transcranial magnetic stimulation of premotor cortex can reduce but not enhance short-term facilitation of primary motor cortex.  

PubMed

Short trains of suprathreshold 5-Hz repetitive transcranial magnetic stimulation (rTMS) over primary motor cortex (M1) evoke motor potentials (MEPs) in hand muscles that progressively increase in amplitude via a mechanism that is thought to be similar to short-term potentiation described in animal preparations. Long trains of subthreshold rTMS over dorsal premotor cortex (PMd) are known to affect the amplitude of single-pulse MEPs evoked from M1. We tested whether PMd-rTMS affects short-term facilitation in M1. We also explored the effect of PMd-rTMS on M1 responses evoked by single-pulse TMS of different polarities. We tested in 15 healthy subjects short-term facilitation in left M1 (10 suprathreshold TMS pulses at 5 Hz) after applying rTMS to left PMd (1,500 subthreshold pulses at 1 and 5 Hz). In a sample of subjects we delivered single-pulse TMS with different polarities and paired-pulse TMS at short intervals (SICI) after PMd-rTMS. Short-term facilitation in M1 was reduced after applying 1 Hz to PMd, but was unaffected after 5-Hz PMd-rTMS. PMd-rTMS with 1 Hz reduced the amplitude of MEPs evoked by monophasic posteroanterior (PA) or biphasic anteroposterior (AP)-PA but had little effect on MEPs by monophasic AP or biphasic PA-AP single-pulse TMS. PMd-rTMS left SICI unchanged. PMd-rTMS (1 Hz) reduces short-term facilitation in M1 induced by short 5-Hz trains. This effect is likely to be caused by reduced facilitation of I-wave inputs to corticospinal neurons. PMID:18057113

Suppa, A; Bologna, M; Gilio, F; Lorenzano, C; Rothwell, J C; Berardelli, A

2008-02-01

235

Repetitive transcranial magnetic stimulation promotes neural stem cell proliferation via the regulation of MiR-25 in a rat model of focal cerebral ischemia.  

PubMed

Repetitive transcranial magnetic stimulation (rTMS) has increasingly been studied over the past decade to determine whether it has a therapeutic benefit on focal cerebral ischemia. However, the underlying mechanism of rTMS in this process remains unclear. In the current study, we investigated the effects of rTMS on the proliferation of adult neural stem cells (NSCs) and explored microRNAs (miRNAs) that were affected by rTMS. Our data showed that 10 Hz rTMS significantly increased the proliferation of adult NSCs after focal cerebral ischemia in the subventricular zone (SVZ), and the expression of miR-25 was obviously up-regulated in the ischemic cortex after rTMS. p57, an identified miR-25 target gene that regulates factors linked to NSC proliferation, was also evaluated, and it exhibited down-regulation. To further verify the role of miR-25, rats were injected with a single dose of antagomir-25 and were subjected to focal cerebral ischemia followed by rTMS treatment. The results confirmed that miR-25 could be repressed specifically and could drive the up-regulation of its target gene (p57), which resulted in the inhibition of adult NSC proliferation in the SVZ after rTMS. Thus, our studies strongly indicated that 10 Hz rTMS can promote the proliferation of adult NSCs in the SVZ after focal cerebral ischemia by regulating the miR-25/p57 pathway. PMID:25302788

Guo, Feng; Han, Xiaohua; Zhang, Jinghui; Zhao, Xiuxiu; Lou, Jicheng; Chen, Hong; Huang, Xiaolin

2014-01-01

236

Effects of pharmacological agents, sleep deprivation, hypoxia and transcranial magnetic stimulation on electroencephalographic rhythms in rodents: towards translational challenge models for drug discovery in Alzheimer's disease.  

PubMed

Different kinds of challenge can alter spontaneous ongoing electroencephalographic (EEG) rhythms in animal models, thus providing paradigms to evaluate treatment effects in drug discovery. The effects of challenges represented by pharmacological agents, hypoxia, sleep deprivation and transcranial magnetic stimulation (TMS) on EEG rhythms are here reviewed to build a knowledge platform for innovative translational models for drug discovery in Alzheimer's disease (AD). It has been reported that antagonists of cholinergic neurotransmission cause synchronisation of spontaneous ongoing EEG rhythms in terms of enhanced power of EEG low frequencies and decreased power of EEG high frequencies. Acetylcholinesterase inhibitors and serotonergic drugs may restore a normal pattern of EEG desynchronisation. Sleep deprivation and hypoxia challenges have also been reported to elicit abnormal synchronisation of spontaneous ongoing EEG rhythms in rodents. The feasibility and reproducibility of TMS have been demonstrated in rodents but information on a consistent modulation of EEG after TMS manipulation is very limited. Transgenic mice over-expressing human amyloid precursor protein complementary DNAs (cDNAs) harbouring the 'Swedish' mutation and PS-1 cDNAs harbouring the A264E mutation, which recapitulate some of the pathological features of AD, exhibit alterations of spontaneous ongoing EEG rhythms at several low and high frequencies. This does not appear, however, to be a consequence of beta-amyloid deposition in the brain. The present review provides a critical evaluation of changes of spontaneous ongoing EEG rhythms due to the experimental manipulations described above, in order to stimulate the promote more adherent models fitting dynamics in humans. PMID:23040292

Babiloni, Claudio; Infarinato, Francesco; Aujard, Fabienne; Bastlund, Jesper Frank; Bentivoglio, Marina; Bertini, Giuseppe; Del Percio, Claudio; Fabene, Paolo Francesco; Forloni, Gianluigi; Herrero Ezquerro, Maria Trinidad; Noè, Francesco Mattia; Pifferi, Fabien; Ros-Bernal, Francisco; Christensen, Ditte Zerlang; Dix, Sophie; Richardson, Jill C; Lamberty, Yves; Drinkenburg, Wilhelmus; Rossini, Paolo Maria

2013-03-01

237

Transcranial magnetic stimulation in mild to severe hemiparesis early after stroke: a proof of principle and novel approach to improve motor function.  

PubMed

Low-frequency repetitive transcranial magnetic stimulation (rTMS) of the unaffected hemisphere can enhance function of the paretic hand in patients with mild motor impairment. Effects of low-frequency rTMS to the contralesional motor cortex at an early stage of mild to severe hemiparesis after stroke are unknown. In this pilot, randomized, double-blind clinical trial we compared the effects of low-frequency rTMS or sham rTMS as add-on therapies to outpatient customary rehabilitation, in 30 patients within 5-45 days after ischemic stroke, and mild to severe hand paresis. The primary feasibility outcome was compliance with the interventions. The primary safety outcome was the proportion of intervention-related adverse events. Performance of the paretic hand in the Jebsen-Taylor test and pinch strength were secondary outcomes. Outcomes were assessed at baseline, after ten sessions of treatment administered over 2 weeks and at 1 month after end of treatment. Baseline clinical features were comparable across groups. For the primary feasibility outcome, compliance with treatment was 100% in the active group and 94% in the sham group. There were no serious intervention-related adverse events. There were significant improvements in performance in the Jebsen-Taylor test (mean, 12.3% 1 month after treatment) and pinch force (mean, 0.5 Newtons) in the active group, but not in the sham group. Low-frequency rTMS to the contralesional motor cortex early after stroke is feasible, safe and potentially effective to improve function of the paretic hand, in patients with mild to severe hemiparesis. These promising results will be valuable to design larger randomized clinical trials. PMID:22173953

Conforto, Adriana B; Anjos, Sarah M; Saposnik, Gustavo; Mello, Eduardo A; Nagaya, Erina M; Santos, Waldyr; Ferreiro, Karina N; Melo, Eduardo S; Reis, Felipe I; Scaff, Milberto; Cohen, Leonardo G

2012-07-01

238

Whole-hand water flow stimulation increases motor cortical excitability: a study of transcranial magnetic stimulation and movement-related cortical potentials.  

PubMed

Previous studies examining the influence of afferent stimulation on corticospinal excitability have demonstrated that the intensity of afferent stimulation and the nature of the afferents targeted (cutaneous/proprioceptive) determine the effects. In this study, we assessed the effects of whole-hand water immersion (WI) and water flow stimulation (WF) on corticospinal excitability and intracortical circuits by measuring motor evoked potential (MEP) recruitment curves and conditioned MEP amplitudes. We further investigated whether whole-hand WF modulated movement-related cortical activity. Ten healthy subjects participated in three experiments, comprising the immersion of participants' right hands with (whole-hand WF) or without (whole-hand WI) water flow, and no immersion (control). We evaluated MEP recruitment curves produced by a single transcranial magnetic stimulation (TMS) pulse at increasing stimulus intensities, short-interval intracortical inhibition (SICI), and intracortical facilitation (ICF) using the paired TMS technique before and after 15 min of intervention. Movement-related cortical potentials (MRCPs) were evaluated to examine primary motor cortex, supplementary motor area, and somatosensory cortex excitability upon movement before and after whole-hand WF. After whole-hand WF, the slope of the MEP recruitment curve significantly increased, whereas SICI decreased and ICF increased in the contralateral motor cortex. The amplitude of the Bereitschaftspotential, negative slope, and motor potential of MRCPs significantly increased after whole-hand WF. We demonstrated that whole-hand WF increased corticospinal excitability, decreased SICI, and increased ICF, although whole-hand WI did not change corticospinal excitability and intracortical circuits. Whole-hand WF modulated movement-related cortical activity, increasing motor cortex activation for the planning and execution of voluntary movements. PMID:25376780

Sato, Daisuke; Yamashiro, Koya; Onishi, Hideaki; Yasuhiro, Baba; Shimoyama, Yoshimitsu; Maruyama, Atsuo

2015-02-01

239

Variation in the dopamine D2 receptor gene plays a key role in human pain and its modulation by transcranial magnetic stimulation.  

PubMed

We tested whether variation of the dopamine D2 receptor (DRD2) gene contributes to individual differences in thermal pain sensitivity and analgesic efficacy of repetitive transcranial magnetic stimulation (rTMS) in healthy subjects (n=29) or susceptibility to neuropathic pain in patients with neurophysiologically confirmed diagnosis (n=16). Thermal sensitivity of healthy subjects was assessed before and after navigated rTMS provided to the S1/M1 cortex. All subjects were genotyped for the DRD2 gene 957C>T and catechol-O-methyltransferase (COMT) protein Val158Met polymorphisms. In healthy subjects, 957C>T influenced both innocuous and noxious thermal detection thresholds that were lowest in 957TT homozygotes (P values from .0277 to .0462). rTMS to S1 cortex had analgesic effect only in 957TT homozygote genotype (P=.0086). In patients, prevalence of 957TT homozygote genotype was higher than in a healthy Finnish population (50% vs 27%; P=.0191). Patients with 957TT genotype reported more severe pain than patients with other genotypes (P=.0351). COMT Val158Met polymorphism was not independently associated with the studied variables. Genetic regulation of DRD2 function by 957C>T polymorphism thus seems to influence thermal and pain sensitivity, its modulation by rTMS, and susceptibility to neuropathic pain. This indicates a central role for the dopamine system and DRD2 in pain and analgesia. This may have clinical implications regarding individualized selection of patients for rTMS treatment and assessment of risks for neuropathic pain. PMID:25180011

Jääskeläinen, Satu K; Lindholm, Pauliina; Valmunen, Tanja; Pesonen, Ullamari; Taiminen, Tero; Virtanen, Arja; Lamusuo, Salla; Forssell, Heli; Hagelberg, Nora; Hietala, Jarmo; Pertovaara, Antti

2014-10-01

240

Effect of maintaining neck flexion on anti-saccade reaction time: an investigation using transcranial magnetic stimulation to the frontal oculomotor field  

PubMed Central

Background Reaction time for anti-saccade, in which the gaze is directed to the position opposite to an illuminated target, shortens during maintenance of neck flexion. The present study applied transcranial magnetic stimulation (TMS) to the frontal oculomotor field, and investigated the effect of maintaining neck flexion on information processing time in the anti-saccade neural pathway before the frontal oculomotor field. Methods The reaction time was measured with the chin resting on a stand (‘chin-on’ condition) and with voluntary maintenance of neck flexion (‘chin-off’ condition) at 80% maximal neck flexion angle, with and without TMS. The TMS timing producing the longest prolongation of the reaction time was first roughly identified for 10 ms intervals from 0 to 180 ms after the target presentation. Thereafter, TMS timing was set finely at 2 ms intervals from ?20 to +20 ms of the 10 ms step that produced the longest prolongation. Results The reaction time without TMS was significantly shorter (21.9 ms) for the chin-off (235.9?±?14.9 ms) than for the chin-on (257.5?±?17.1 ms) condition. Furthermore, TMS timing producing maximal prolongation of the reaction time was significantly earlier (18.6 ms) for the chin-off than the chin-on condition. The ratio of the forward shift in TMS timing relative to the reduction in reaction time was 87.8%. Conclusions We confirmed that information processing time in the anti-saccade neural pathway before the frontal oculomotor field shortened while neck flexion was maintained, and that this reduction time accounted for approximately 88% of the shortening of reaction time. PMID:24220550

2013-01-01

241

Safety and tolerability of theta burst stimulation vs. single and paired pulse transcranial magnetic stimulation: a comparative study of 165 pediatric subjects  

PubMed Central

Background: Although single- and paired-pulse (sp/pp) transcranial magnetic stimulation (TMS) studies are considered minimal risk in adults and children, the safety profile for theta-burst TMS (TBS) is unknown. Objective: In this comparative analysis, we explored the rate, severity, and specific symptoms of TMS-related adverse effects (AEs) between sp/ppTMS and TBS in subjects between ages 6 and 18 years. Method: Data from 165 participants from 2009 to 2014 were analyzed. Assessment of AEs was performed based on baseline and post-TMS administration of a symptom-based questionnaire that rated AEs on a 5-level ordinal scale (minimal, mild, moderate, marked, severe). AE rates and severity were compared using Chi Square or Fisher’s Exact Test depending on data characteristics. Result: Overall, no seizures or severe-rated AEs were reported by 165 pediatric participants. The rate of AE in all TBS sessions was 10.5% (n = 76, 95% CI: 4.7–19.7%), whereas the rate of AE in all sp/ppTMS sessions was 12.4% (n = 89, 95% CI: 6.3–21.0%). There was no statistical difference in AE rates between TBS and sp/ppTMS (p = 0.71). In all sp/ppTMS and TBS sessions, 20 subjects reported a total of 35 AEs, among these 31 (~88.6%) were rated as “minimal” or “mild”. There was no difference in the severity of AE between TBS and sp/ppTMS (p = 1.0). Only one of 76 TBS participants reported an AE rated as more than minimal/mild. Conclusion: Our comparative analysis showed that TBS appears to be as safe as sp/ppTMS in terms of AE rate and severity. This report supports further investigation of TBS in children.

Hong, Yaejee H.; Wu, Steve W.; Pedapati, Ernest V.; Horn, Paul S.; Huddleston, David A.; Laue, Cameron S.; Gilbert, Donald L.

2015-01-01

242

Whole-Body Water Flow Stimulation to the Lower Limbs Modulates Excitability of Primary Motor Cortical Regions Innervating the Hands: A Transcranial Magnetic Stimulation Study  

PubMed Central

Whole-body water immersion (WI) has been reported to change sensorimotor integration. However, primary motor cortical excitability is not affected by low-intensity afferent input. Here we explored the effects of whole-body WI and water flow stimulation (WF) on corticospinal excitability and intracortical circuits. Eight healthy subjects participated in this study. We measured the amplitude of motor-evoked potentials (MEPs) produced by single transcranial magnetic stimulation (TMS) pulses and examined conditioned MEP amplitudes by paired-pulse TMS. We evaluated short-interval intracortical inhibition (SICI) and intracortical facilitation (ICF) using the paired-TMS technique before and after 15-min intervention periods. Two interventions used were whole-body WI with water flow to the lower limbs (whole-body WF) and whole-body WI without water flow to the lower limbs (whole-body WI). The experimental sequence included a baseline TMS assessment (T0), intervention for 15 min, a second TMS assessment immediately after intervention (T1), a 10 min resting period, a third TMS assessment (T2), a 10 min resting period, a fourth TMS assessment (T3), a 10 min resting period, and the final TMS assessment (T4). SICI and ICF were evaluated using a conditioning stimulus of 90% active motor threshold and a test stimulus adjusted to produce MEPs of approximately 1–1.2 mV, and were tested at intrastimulus intervals of 3 and 10 ms, respectively. Whole-body WF significantly increased MEP amplitude by single-pulse TMS and led to a decrease in SICI in the contralateral motor cortex at T1, T2 and T3. Whole-body WF also induced increased corticospinal excitability and decreased SICI. In contrast, whole-body WI did not change corticospinal excitability or intracortical circuits. PMID:25025129

Sato, Daisuke; Yamashiro, Koya; Onishi, Hideaki; Baba, Yasuhiro; Nakazawa, Sho; Shimoyama, Yoshimitsu; Maruyama, Atsuo

2014-01-01

243

Hand position-dependent modulation of errors in vibrotactile temporal order judgments: the effects of transcranial magnetic stimulation to the human posterior parietal cortex.  

PubMed

The ability to decide which of the two stimuli is presented first can be probed using a temporal order judgment (TOJ) task. When the stimuli are delivered to the fingers, TOJ decisions can be confounded by the fact that the hands can be moved to different locations in space. How and where this confounded information is processed in the brain is poorly understood. In the present set of experiments, we addressed this knowledge gap by using single-pulse transcranial magnetic stimulation (TMS) to disrupt processing in the right or left posterior parietal cortex (PPC) during a vibrotactile TOJ task with stimuli applied to the right and left index fingers. In the first experiment, participants held their hands in an uncrossed configuration, and we found that when the index finger contralateral to the site of TMS was stimulated first, there was a significant increase in TOJ errors. This increase did not occur when stimuli were delivered to the ipsilateral finger first. In the second experiment, participants held their hands in a crossed configuration and the pattern of errors was reversed relative to the first experiment. In both the first two experiments, significant increases in TOJ error were present with TMS over either hemisphere, regardless of arm configuration; however, they were larger overall following TMS over the right PPC. Control experiments using sham TMS indicated the systematic modulation in error was not due to nonspecific effects of the stimulation. Additionally, we showed that these TMS-induced changes in TOJ errors were not due to a reduced ability to detect the timing of the vibrotactile stimuli. Taken together, these results demonstrate that both the right and left PPC contribute to the processing underlying vibrotactile TOJs by integrating vibrotactile information and proprioceptive information related to arm position in space. PMID:24562409

Ritterband-Rosenbaum, Anina; Hermosillo, Robert; Kroliczak, Gregory; van Donkelaar, Paul

2014-06-01

244

Moderate therapeutic efficacy of positron emission tomography?navigated repetitive transcranial magnetic stimulation for chronic tinnitus: a randomised, controlled pilot study  

PubMed Central

Background Tinnitus has been shown to respond to modulations of cortical activity by high?frequency and low?frequency repetitive transcranial magnetic stimulation (rTMS). Objective To determine the tinnitus?attenuating effects of a 2?week daily regimen of rTMS, navigated to the maximum of tinnitus?related increase in regional cerebral blood flow. Methods Six patients with chronic tinnitus were enrolled in this sham?controlled crossover study and treated with 2×2?weeks of suprathreshold 1?Hz rTMS (30?min) applied to the region with maximal tinnitus?related increase in regional cerebral blood flow delineated by functional imaging with [15O]H2O positron emission tomography and a control area. Tinnitus?related distress was assessed before and after each treatment and 2?weeks after the end of the 4?week course of stimulation using a validated tinnitus questionnaire. Additional self?assessment scores of tinnitus change, loudness and annoyance were obtained. Results In five of six patients, rTMS induced greater reduction of the tinnitus questionnaire score than sham stimulation. In two patients, all parameters measured (tinnitus change score, tinnitus loudness, tinnitus annoyance) showed unequivocal improvement. At the group level, the degree of response in the tinnitus questionnaire score was correlated with tinnitus?associated activation of the anterior cingulate cortex. Two weeks after the final stimulation, tinnitus had returned to baseline in all patients but one. Conclusion Tinnitus can be attenuated by low?frequency rTMS navigated to each person's maximum tinnitus?related cortical hyperactivity. The effects are only moderate; interindividual responsiveness varies and the attenuation seems to wear off within 2?weeks after the last stimulation session. Notably, tinnitus?related anterior cingulate cortex activation seems to predict the response to rTMS treatment. PMID:16891384

Plewnia, C; Reimold, M; Najib, A; Reischl, G; Plontke, S K; Gerloff, C

2007-01-01

245

Short and Long Term Effects of Left and Bilateral Repetitive Transcranial Magnetic Stimulation in Schizophrenia Patients with Auditory Verbal Hallucinations: A Randomized Controlled Trial  

PubMed Central

Background Repetitive transcranial magnetic stimulation of the left temporo-parietal junction area has been studied as a treatment option for auditory verbal hallucinations. Although the right temporo-parietal junction area has also shown involvement in the genesis of auditory verbal hallucinations, no studies have used bilateral stimulation. Moreover, little is known about durability effects. We studied the short and long term effects of 1 Hz treatment of the left temporo-parietal junction area in schizophrenia patients with persistent auditory verbal hallucinations, compared to sham stimulation, and added an extra treatment arm of bilateral TPJ area stimulation. Methods In this randomized controlled trial, 51 patients diagnosed with schizophrenia and persistent auditory verbal hallucinations were randomly allocated to treatment of the left or bilateral temporo-parietal junction area or sham treatment. Patients were treated for six days, twice daily for 20 minutes. Short term efficacy was measured with the Positive and Negative Syndrome Scale (PANSS), the Auditory Hallucinations Rating Scale (AHRS), and the Positive and Negative Affect Scale (PANAS). We included follow-up measures with the AHRS and PANAS at four weeks and three months. Results The interaction between time and treatment for Hallucination item P3 of the PANSS showed a trend for significance, caused by a small reduction of scores in the left group. Although self-reported hallucination scores, as measured with the AHRS and PANAS, decreased significantly during the trial period, there were no differences between the three treatment groups. Conclusion We did not find convincing evidence for the efficacy of left-sided rTMS, compared to sham rTMS. Moreover, bilateral rTMS was not superior over left rTMS or sham in improving AVH. Optimizing treatment parameters may result in stronger evidence for the efficacy of rTMS treatment of AVH. Moreover, future research should consider investigating factors predicting individual response. Trial Registration Dutch Trial Register NTR1813 PMID:25329799

Bais, Leonie; Vercammen, Ans; Stewart, Roy; van Es, Frank; Visser, Bert; Aleman, André; Knegtering, Henderikus

2014-01-01

246

Using Simultaneous Repetitive Transcranial Magnetic Stimulation/Functional Near Infrared Spectroscopy (rTMS/fNIRS) to Measure Brain Activation and Connectivity  

PubMed Central

Introduction Simultaneously acquiring functional Near Infrared Spectroscopy (fNIRS) during Transcranial Magnetic Stimulation (rTMS) offers the possibility of directly investigating superficial cortical brain activation and connectivity. In addition, the effects of rTMS in distinct brain regions without quantifiable behavioral changes can be objectively measured. Methods Healthy, non-medicated participants age 18–50 years were recruited from the local community. After written informed consent was obtained, the participants were screened to ensure that they met inclusion criteria. They underwent two visits of simultaneous rTMS/fNIRS separated by 2 to 3 days. In each visit, the motor cortex and subsequently the prefrontal cortex (5 cm anterior to the motor cortex) were stimulated (1 Hz, max 120% MT, 10 secs on with 80 secs off, for 15 trains) while simultaneous fNIRS data were acquired from the ipsilateral and contralateral brain regions. Results Twelve healthy volunteers were enrolled with one excluded prior to stimulation. The 11 participants studied (nine male) had a mean age of 31.8 (s.d. 10.2, range 20–49) years. There was no significant difference in fNIRS between Visit 1 and Visit 2. Stimulation of both the motor and prefrontal cortices resulted in a significant decrease in oxygenated hemoglobin (HbO2) concentration in both the ipsilateral and contralateral cortices. The ipsilateral and contralateral changes showed high temporal consistency. Discussion Simultaneous rTMS/fNIRS provides a reliable measure of regional cortical brain activation and connectivity that could be very useful in studying brain disorders as well as cortical changes induced by rTMS. PMID:19446635

Kozel, F. Andrew; Tian, Fenghua; Dhamne, Sameer; Croarkin, Paul E.; McClintock, Shawn M.; Elliott, Alan; Mapes, Kimberly S.; Husain, Mustafa M.; Liu, Hanli

2009-01-01

247

Small-animal repetitive transcranial magnetic stimulation combined with [¹?F]-FDG microPET to quantify the neuromodulation effect in the rat brain.  

PubMed

Repetitive transcranial magnetic stimulation (rTMS) is a non-invasive neurostimulation technique for the treatment of various neurological and psychiatric disorders. To investigate the working mechanism of this treatment approach, we designed a small-animal coil for dedicated use in rats and we combined this neurostimulation method with small-animal positron emission tomography (microPET or ?PET) to quantify regional 2-deoxy-2-((18)F)fluoro-d-glucose ([(18)F]-FDG) uptake in the rat brain, elicited by a low- (1 Hz) and a high- (50 Hz) frequency paradigm. Rats (n=6) were injected with 1 mCi of [(18)F]-FDG 10 min after the start of 30 min of stimulation (1 Hz, 50 Hz or sham), followed by a 20-min ?PET image acquisition. Voxel-based statistical parametric mapping (SPM) image analysis of 1-Hz and 50-Hz versus sham stimulation was performed. For both the 1-Hz and 50-Hz paradigms we found a large [(18)F]-FDG hypermetabolic cluster (2.208 mm(3) and 2.616 mm(3), resp.) (analysis of variance (ANOVA), p<0.05) located in the dentate gyrus complemented with an additional [(18)F]-FDG hypermetabolic cluster (ANOVA, p<0.05) located in the entorhinal cortex (2.216 mm(3)) for the 50-Hz stimulation. The effect on [(18)F]-FDG metabolism was 2.9 ± 0.8% at 1 Hz and 2.5 ± 0.8% at 50 Hz for the dentate gyrus clusters and 3.3 ± 0.5% for the additional cluster in the entorhinal cortex at 50 Hz. The maximal (4.19 vs. 2.58) and averaged (2.87 vs. 2.21) T-values are higher for 50 Hz versus 1 Hz. This experimental study demonstrates the feasibility to combine ?PET imaging in rats stimulated with rTMS using a custom-made small-animal magnetic stimulation setup to quantify changes in the cerebral [(18)F]-FDG uptake as a measure for neuronal activity. PMID:24979056

Parthoens, J; Verhaeghe, J; Wyckhuys, T; Stroobants, S; Staelens, S

2014-09-01

248

Low Frequency Repetitive Transcranial Magnetic Stimulation to Improve Motor Function and Grip Force of Upper Limbs of Patients With Hemiplegia  

PubMed Central

Background: Stroke is the most common and debilitating neurological disorder among adults, and is a sudden onset of neurological signs caused by brain blood vessels impairments. Objectives: Some new therapeutic methods focus on the use of magnetic stimulation to produce therapeutic effects by inducing the currents. The aim of this study is to determine the effects of rTMS plus routine rehabilitation on hand grip and wrist motor functions in patients with hemiplegia, and compare with pure routine rehabilitation programs. Patients and Methods: In this study, 12 patients with hemiplegia were randomly divided in two groups. Control group, received the rehabilitation program with placebo magnetic stimulation, and the experimental group, received magnetic stimulation with routine rehabilitation program for 10 sessions for three times per week. Pre and post evaluations of treatment performed using Barthel and Fugl-Meyer indices and dynamometers. Results: In the control group, Barthel and Fugl-Meyer indices showed significant improvement (P = 0.01, P = 0.00), while in the experimental group, significant improvement in Barthel and Fugl-Meyer indices and dynamometers has been observed (P = 0.01, P = 0.00, P = 0.007). Conclusions: rTMS can improve hand muscle force and functions of patients with chronic hemiplegia, while conventional treatment is not effective. PMID:25389476

Motamed Vaziri, Poopak; Bahrpeyma, Farid; Firoozabadi, Mohammad; Forough, Bijan; Hatef, Boshra; Sheikhhoseini, Rahman; Shamili, Aryan

2014-01-01

249

Cathodal Transcranial Direct Current Stimulation of the Right Wernicke's Area Improves Comprehension in Subacute Stroke Patients  

ERIC Educational Resources Information Center

Previous studies have shown the appearance of right-sided language-related brain activity in right-handed patients after a stroke. Non-invasive brain stimulation such as transcranial direct current stimulation (tDCS) and repetitive transcranial magnetic stimulation (rTMS) have been shown to modulate excitability in the brain. Moreover, rTMS and…

You, Dae Sang; Kim, Dae-Yul; Chun, Min Ho; Jung, Seung Eun; Park, Sung Jong

2011-01-01

250

Transcranial cerebral oximeter  

Microsoft Academic Search

Transcranial cerebral oximetry (TCCO) is a techniqe that evaluates saturation of oxygen in the underlying area of the brain by the noninvasive method of near-infrared spectroscpoy. Human tissues are generally transparent to light in the near-infrared range, so the light of this range (650 nm-1 100 nm) easily penetrates tissue to a depth of several centimeters. The light is partially

Mukesh Misra; Manuel Dujovny; M. S. Alp; James I. Ausman

1995-01-01

251

The restoration after repetitive transcranial magnetic stimulation treatment on cognitive ability of vascular dementia rats and its impacts on synaptic plasticity in hippocampal CA1 area.  

PubMed

The purposes of this research were to study the restoration on the cognitive ability of rat models with vascular dementia (VaD) by repetitive transcranial magnetic stimulation (rTMS) treatment and its impacts on synaptic plasticity in hippocampal CA1 area and to further explore the molecular mechanisms of the rTMS treatment on vascular dementia. Thirty-six male Wistar rats were randomly divided into four groups: the normal control group, the vascular dementia model group, the low-frequency rTMS group, and the high-frequency rTMS group. Two-vessel occlusion was employed to make VaD models. Low-frequency rTMS group rats were treated with 0.5 Hz rTMS for 6 weeks. High-frequency rTMS group rats underwent 5 Hz rTMS for 6 weeks. Morris water maze was carried out to detect the ability of spatial learning and memory of rats. The ultra-structural changes of synapses in four groups were observed by transmission electron microscope. Then the expressions of brain-derived neurotrophic factor (BDNF), NMDAR1, and Synaptophysin (SYN) mRNA and proteins in hippocampal CA1 area were determined by real-time PCR, western blot, and immunohistochemistry assay. After rTMS treatment, the learning and memory abilities of VaD rats improved significantly. The ultra-structures of synapses in hippocampal CA1 area in rTMS groups were reformed. The mRNA and protein expressions of BDNF, NMDAR1, and SYN in the low-frequency rTMS group and in the high-frequency rTMS group were higher than that in VaD model group (P < 0.05). rTMS plays an important and beneficial role in the restoration treatment of vascular dementia, which may be related to the mechanism that rTMS can increase the mRNA and protein expressions of BDNF, NMDAR1, and SYN and affect the synaptic plasticity in hippocampal CA1 area. PMID:19953343

Wang, Fei; Geng, Xin; Tao, Hua-Ying; Cheng, Yan

2010-05-01

252

Repetitive transcranial magnetic stimulation as an augmentative strategy for treatment-resistant depression, a meta-analysis of randomized, double-blind and sham-controlled study.  

PubMed

BackgroundDozens of randomized controlled trials (RCTs) and meta-analyses have demonstrated the efficacy of repetitive transcranial magnetic stimulation (rTMS) for major depressive disorder (MDD) treatment, but there has not been a meta-analysis report which evaluates the efficacy and tolerability of rTMS used as an augmentative strategy for antidepressants in treatment-resistant depression (TRD) treatment. We thus conducted this meta-analysis, aimed at clarifying whether rTMS enhances the efficacy of TRD.MethodsWe searched MEDLINE and Cochrane Central Register of Controlled Trials for RCTs for studying the efficacy of rTMS versus (vs) sham condition when combined with antidepressants in TRD treatment, and screened the references of the previous meta-analysis about the rTMS for MDD treatment. Response rates and NNT were chose as the primary outcomes, and remission rates, change from baseline of HAMD scores, dropouts were used as secondary outcomes. For dichotomous data, an intention-to-treat analysis principle was applied; for continuous data, we calculated the standard mean difference between groups with a random-effect model. Sensitivity analysis was done to explore the source of heterogeneity and the factors which potentially impact the efficacy.ResultsSeven RCTs were finally included in the meta-analysis. The total sample size was 279, with 171 in the rTMS group and 108 in the sham group. The pooled response and remission rate for the rTMS and sham group was 46.6% and 22.1%, respectively; the pooled odds ratio (OR) was 5.12 [95% confidence interval (CI) 2.11-12.45, z¿=¿3.60, p¿=¿0.0003, and the associated number needed to treat (NNT) was 3.4. rTMS group achieved a significant reduction of HAMD score than the sham group, the pooled SMD of change from baseline was 0.86 [95% confidence interval (CI) 0.57-1.15, z¿=¿5.75, p¿<¿0.00001]. Because of the small number of included RCTs, the preplanned sensitivity and subgroup analyses were finally abandoned. The dropouts in both groups were relatively low, indicating the high acceptability of rTMS.ConclusionsFor TRD patients, augmentative rTMS after the failure of medications significantly increases the effect of antidepressants, and rTMS was a safe strategy with relatively low adverse events and low dropout rate, suggesting that augmentative rTMS is an effective intervention for TRD. PMID:25433539

Liu, Bangshan; Zhang, Yan; Zhang, Li; Li, Lingjiang

2014-11-30

253

Low-Frequency Repetitive Transcranial Magnetic Stimulation (rTMS) Affects Event-Related Potential Measures of Novelty Processing in Autism  

PubMed Central

In our previous study on individuals with autism spectrum disorder (ASD) (Sokhadze et al., Appl Psychophysiol Biofeedback 34:37–51, 2009a) we reported abnormalities in the attention-orienting frontal event-related potentials (ERP) and the sustained-attention centro-parietal ERPs in a visual oddball experiment. These results suggest that individuals with autism over-process information needed for the successful differentiation of target and novel stimuli. In the present study we examine the effects of low-frequency, repetitive Transcranial Magnetic Stimulation (rTMS) on novelty processing as well as behavior and social functioning in 13 individuals with ASD. Our hypothesis was that low-frequency rTMS application to dorsolateral prefrontal cortex (DLFPC) would result in an alteration of the cortical excitatory/inhibitory balance through the activation of inhibitory GABAergic double bouquet interneurons. We expected to find post-TMS differences in amplitude and latency of early and late ERP components. The results of our current study validate the use of low-frequency rTMS as a modulatory tool that altered the disrupted ratio of cortical excitation to inhibition in autism. After rTMS the parieto-occipital P50 amplitude decreased to novel distracters but not to targets; also the amplitude and latency to targets increased for the frontal P50 while decreasing to non-target stimuli. Low-frequency rTMS minimized early cortical responses to irrelevant stimuli and increased responses to relevant stimuli. Improved selectivity in early cortical responses lead to better stimulus differentiation at later-stage responses as was made evident by our P3b and P3a component findings. These results indicate a significant change in early, middle-latency and late ERP components at the frontal, centro-parietal, and parieto-occipital regions of interest in response to target and distracter stimuli as a result of rTMS treatment. Overall, our preliminary results show that rTMS may prove to be an important research tool or treatment modality in addressing the stimulus hypersensitivity characteristic of autism spectrum disorders. PMID:19941058

Baruth, Joshua; Tasman, Allan; Mansoor, Mehreen; Ramaswamy, Rajesh; Sears, Lonnie; Mathai, Grace; El-Baz, Ayman; Casanova, Manuel F.

2009-01-01

254

Design of a placebo-controlled, randomized study of the efficacy of repetitive transcranial magnetic stimulation for the treatment of chronic tinnitus  

PubMed Central

Background Chronic tinnitus is a frequent condition, which can have enormous impact on patient's life and which is very difficult to treat. Accumulating data indicate that chronic tinnitus is related to dysfunctional neuronal activity in the central nervous system. Repetitive transcranial magnetic stimulation (rTMS) is a non-invasive method which allows to focally modulate neuronal activity. An increasing amount of studies demonstrate reduction of tinnitus after repeated sessions of low-frequency rTMS and indicate that rTMS might represent a new promising approach for the treatment of tinnitus. However available studies have been mono-centric and are characterized by small sample sizes. Therefore, this multi-center trial will test the efficacy of rTMS treatment in a large sample of chronic tinnitus patients. Methods/Design This is a randomized, placebo-controlled, double-blind multi-center trial of two weeks 1 Hz rTMS-treatment in chronic tinnitus patients. Eligible patients will be randomized to either 2 weeks real or sham rTMS treatment. Main eligibility criteria: male or female individuals aged 18–70 years with chronic tinnitus (duration > 6 months), tinnitus-handicap-inventory-score ? 38, age-adjusted normal sensorineural hearing (i.e. not more than 5 dB below the 10% percentile of the appropriate age and gender group (DIN EN ISO 7029), conductive hearing loss ? 15dB. The primary endpoint is a change of tinnitus severity according to the tinnitus questionnaire of Goebel and Hiller (baseline vs. end of treatment period). A total of 138 patients are needed to detect a clinical relevant change of tinnitus severity (i.e. 5 points on the questionnaire of Goebel and Hiller; alpha = 0.05; 1-beta = 0.80). Assuming a drop-out rate of less than 5% until the primary endpoint, 150 patients have to be randomized to guarantee the target number of 138 evaluable patients. The study will be conducted by otorhinolaryngologists and psychiatrists of 7 university hospitals and 1 municipal hospital in Germany. Discussion This study will provide important information about the efficacy of rTMS in the treatment of chronic tinnitus. Trial registration Current Controlled Trials ISRCTN89848288 PMID:18412944

Landgrebe, Michael; Binder, Harald; Koller, Michael; Eberl, Yvonne; Kleinjung, Tobias; Eichhammer, Peter; Graf, Erika; Hajak, Goeran; Langguth, Berthold

2008-01-01

255

Comparison of effects of transcranial magnetic stimulation on primary motor cortex and supplementary motor area in motor skill learning (randomized, cross over study)  

PubMed Central

Motor skills require quick visuomotor reaction time, fast movement time, and accurate performance. Primary motor cortex (M1) and supplementary motor area (SMA) are closely related in learning motor skills. Also, it is well known that high frequency repeated transcranial magnetic stimulation (rTMS) on these sites has a facilitating effect. The aim of this study was to compare the effects of high frequency rTMS activation of these two brain sites on learning of motor skills. Twenty three normal volunteers participated. Subjects were randomly stimulated on either brain area, SMA or M1. The motor task required the learning of sequential finger movements, explicitly or implicitly. It consisted of pressing the keyboard sequentially with their right hand on seeing 7 digits on the monitor explicitly, and then tapping the 7 digits by memorization, implicitly. Subjects were instructed to hit the keyboard as fast and accurately as possible. Using Musical Instrument Digital Interface (MIDI), the keyboard pressing task was measured before and after high frequency rTMS for motor performance, which was measured by response time (RT), movement time, and accuracy (AC). A week later, the same task was repeated by cross-over study design. At this time, rTMS was applied on the other brain area. Two-way ANOVA was used to assess the carry over time effect and stimulation sites (M1 and SMA), as factors. Results indicated that no carry-over effect was observed. The AC and RT were not different between the two stimulating sites (M1 and SMA). But movement time was significantly decreased after rTMS on both SMA and M1. The amount of shortened movement time after rTMS on SMA was significantly increased as compared to the movement time after rTMS on M1 (p < 0.05), especially for implicit learning of motor tasks. The coefficient of variation was lower in implicit trial than in explicit trial. In conclusion, this finding indicated an important role of SMA compared to M1, in implicit motor learning. PMID:25477809

Kim, Yong Kyun; Shin, Sung Hun

2014-01-01

256

Monitoring Cortical Excitability during Repetitive Transcranial Magnetic Stimulation in Children with ADHD: A Single-Blind, Sham-Controlled TMS-EEG Study  

PubMed Central

Background Repetitive transcranial magnetic stimulation (rTMS) allows non-invasive stimulation of the human brain. However, no suitable marker has yet been established to monitor the immediate rTMS effects on cortical areas in children. Objective TMS-evoked EEG potentials (TEPs) could present a well-suited marker for real-time monitoring. Monitoring is particularly important in children where only few data about rTMS effects and safety are currently available. Methods In a single-blind sham-controlled study, twenty-five school-aged children with ADHD received subthreshold 1 Hz-rTMS to the primary motor cortex. The TMS-evoked N100 was measured by 64-channel-EEG pre, during and post rTMS, and compared to sham stimulation as an intraindividual control condition. Results TMS-evoked N100 amplitude decreased during 1 Hz-rTMS and, at the group level, reached a stable plateau after approximately 500 pulses. N100 amplitude to supra-threshold single pulses post rTMS confirmed the amplitude reduction in comparison to the pre-rTMS level while sham stimulation had no influence. EEG source analysis indicated that the TMS-evoked N100 change reflected rTMS effects in the stimulated motor cortex. Amplitude changes in TMS-evoked N100 and MEPs (pre versus post 1 Hz-rTMS) correlated significantly, but this correlation was also found for pre versus post sham stimulation. Conclusion The TMS-evoked N100 represents a promising candidate marker to monitor rTMS effects on cortical excitability in children with ADHD. TMS-evoked N100 can be employed to monitor real-time effects of TMS for subthreshold intensities. Though TMS-evoked N100 was a more sensitive parameter for rTMS-specific changes than MEPs in our sample, further studies are necessary to demonstrate whether clinical rTMS effects can be predicted from rTMS-induced changes in TMS-evoked N100 amplitude and to clarify the relationship between rTMS-induced changes in TMS-evoked N100 and MEP amplitudes. The TMS-evoked N100 amplitude reduction after 1 Hz-rTMS could either reflect a globally decreased cortical response to the TMS pulse or a specific decrease in inhibition. PMID:23185537

Helfrich, Christian; Pierau, Simone S.; Freitag, Christine M.; Roeper, Jochen; Ziemann, Ulf; Bender, Stephan

2012-01-01

257

Deep-tow study of magnetic anomalies in the Pacific Jurassic Quiet Zone  

E-print Network

The Jurassic Quiet Zone (JQZ) is a region of low amplitude, difficult-to-correlate magnetic anomalies located over Jurassic oceanic crust. We collected 1200 km of new deep-tow magnetic anomaly profiles over the Pacific JQZ that complement 2 deep...

Tominaga, Masako

2006-10-30

258

Cranial electrotherapy stimulation and transcranial pulsed current stimulation: a computer based high-resolution modeling study.  

PubMed

The field of non-invasive brain stimulation has developed significantly over the last two decades. Though two techniques of noninvasive brain stimulation--transcranial direct current stimulation (tDCS) and transcranial magnetic stimulation (TMS)--are becoming established tools for research in neuroscience and for some clinical applications, related techniques that also show some promising clinical results have not been developed at the same pace. One of these related techniques is cranial electrotherapy stimulation (CES), a class of transcranial pulsed current stimulation (tPCS). In order to understand further the mechanisms of CES, we aimed to model CES using a magnetic resonance imaging (MRI)-derived finite element head model including cortical and also subcortical structures. Cortical electric field (current density) peak intensities and distributions were analyzed. We evaluated different electrode configurations of CES including in-ear and over-ear montages. Our results confirm that significant amounts of current pass the skull and reach cortical and subcortical structures. In addition, depending on the montage, induced currents at subcortical areas, such as midbrain, pons, thalamus and hypothalamus are of similar magnitude than that of cortical areas. Incremental variations of electrode position on the head surface also influence which cortical regions are modulated. The high-resolution modeling predictions suggest that details of electrode montage influence current flow through superficial and deep structures. Finally we present laptop based methods for tPCS dose design using dominant frequency and spherical models. These modeling predictions and tools are the first step to advance rational and optimized use of tPCS and CES. PMID:23041337

Datta, Abhishek; Dmochowski, Jacek P; Guleyupoglu, Berkan; Bikson, Marom; Fregni, Felipe

2013-01-15

259

Rock magnetic signatures in diagenetically altered sediments from the Niger deep-sea fan  

Microsoft Academic Search

Diagenesis has extensively affected the magnetic mineral inventory of organic-rich late Quaternary sediments in the Niger deep-sea fan. Changes in concentration, grain size, and coercivity document modifications of the primary magnetic mineral assemblages at two horizons. The first front, the modern iron redox boundary, is characterized by a drastic decline in magnetic mineral content, coarsening of the grain size spectrum,

Melanie Dillon; Ulrich Bleil

2006-01-01

260

Language Lateralization in Children Using Functional Transcranial Doppler Sonography  

ERIC Educational Resources Information Center

Aim: Language lateralization with functional transcranial Doppler sonography (fTCD) and lexical word generation has been shown to have high concordance with the Wada test and functional magnetic resonance imaging in adults. We evaluated a nonlexical paradigm to determine language dominance in children. Method: In 23 right-handed children (12…

Haag, Anja; Moeller, Nicola; Knake, Susanne; Hermsen, Anke; Oertel, Wolfgang H.; Rosenow, Felix; Hamer, Hajo M.

2010-01-01

261

Premotor transcranial direct current stimulation (tDCS) affects primary motor excitability in humans  

Microsoft Academic Search

Recent studies have shown that repetitive transcranial magnetic stimulation (rTMS) over the premotor cortex (PM) modifies the excitability of the ipsilateral primary motor cortex (M1). Transcranial direct current stimulation (tDCS) is a new method to induce neuroplasticity in humans non-invasively. tDCS generates neuroplasticity directly in the cortical area under the electrode, but might also induce effects in distant brain areas,

Klára Boros; Csaba Poreisz; Alexander Münchau; Walter Paulus; Michael A. Nitsche

2008-01-01

262

Transcranial cerebral oximeter  

NASA Astrophysics Data System (ADS)

Transcranial cerebral oximetry (TCCO) is a techniqe that evaluates saturation of oxygen in the underlying area of the brain by the noninvasive method of near-infrared spectroscpoy. Human tissues are generally transparent to light in the near-infrared range, so the light of this range (650 nm-1 100 nm) easily penetrates tissue to a depth of several centimeters. The light is partially absorbed by natural chromophores. In the human brain the predominant chromophores are oxygenated (HbO2) and deoxygenated (Hb) hemoglobin. The difference in the absorption spectra between the HbO2 and Hb yields the ratio of the oxygenated to total hemoglobin (the oxygen saturation) in the area of interest. The algorithm used to calculate the oxygen saturation of brain tissue using a multiple-detector system was previously described and validated in a number of animal and human studies. The use of cerebral oximetry in neurosurgery has been described. We discuss some observations from our experience with TCCO.

Misra, Mukesh; Dujovny, Manuel; Alp, M. Serdar; Ausman, James I.

1995-08-01

263

Arrays of carbon nanoscrolls as deep subwavelength magnetic metamaterials  

NASA Astrophysics Data System (ADS)

We demonstrate theoretically that an array of carbon nanoscrolls acts as a hyperbolic magnetic metamaterial in the terahertz regime with genuine subwavelength operation corresponding to a wavelength-to-structure ratio of about 200. Due to the low sheet resistance of graphene, the electromagnetic losses in an array of carbon nanoscrolls are almost negligible, offering a very sharp magnetic resonance of extreme positive and negative values of the effective magnetic permeability. The latter property leads to superior imaging properties for arrays of carbon nanoscrolls which can operate as magnetic endoscopes in the terahertz range where magnetic materials are scarce. Our optical modeling is supplemented with ab initio density functional calculations of the self-winding of a single layer of graphene onto a carbon nanotube so as to form a carbon nanoscroll. The latter process is viewed as a means to realize ordered arrays of carbon nanoscrolls in the laboratory based on arrays of aligned carbon nanotubes which are now routinely fabricated.

Yannopapas, Vassilios; Tzavala, Marilena; Tsetseris, Leonidas

2013-10-01

264

Repetitive transcranial magnetic stimulation (rTMS) augmentation of selective serotonin reuptake inhibitors (SSRIs) for SSRI-resistant obsessive-compulsive disorder (OCD): a meta-analysis of randomized controlled trials  

PubMed Central

Background and objective: Randomized controlled trials (RCTs) on repetitive transcranial magnetic stimulation (rTMS) as augmentation of selective serotonin reuptake inhibitors (SSRIs) for SSRI-resistant obsessive-compulsive disorder (OCD) have yielded conflicting results. Therefore, this meta-analysis was conducted to assess the efficacy of this strategy for SSRI-resistant OCD. Methods: Scientific and medical databases, including international databases (PubMed, MEDLINE, EMBASE, CCTR, Web of Science, PsycINFO), two Chinese databases (CBM-disc, CNKI), and relevant websites dated up to July 2014, were searched for RCTs on this strategy for treating OCD. Mantel-Haenszel random-effects model was used. Yale-Brown Obsessive Compulsive Scale (Y-BOCS) score, response rates and drop-out rates were evaluated. Results: Data were obtained from nine RCTs consisting of 290 subjects. Active rTMS was an effective augmentation strategy in treating SSRI-resistant OCD with a pooled WMD of 3.89 (95% CI = [1.27, 6.50]) for reducing Y-BOCS score and a pooled odds ratio (OR) of 2.65 (95% CI = [1.36, 5.17] for response rates. No significant differences in drop-out rates were found. No publication bias was detected. Conclusion: The pooled examination demonstrated that this strategy seems to be efficacious and acceptable for treating SSRI-resistant OCD. As the number of RCTs included here was limited, further large-scale multi-center RCTs are required to validate our conclusions.

Ma, Zhong-Rui; Shi, Li-Jun

2014-01-01

265

Ages and magnetic structures of the South China Sea constrained by deep tow magnetic surveys and IODP Expedition 349  

NASA Astrophysics Data System (ADS)

analyses of deep tow magnetic anomalies and International Ocean Discovery Program Expedition 349 cores show that initial seafloor spreading started around 33 Ma in the northeastern South China Sea (SCS), but varied slightly by 1-2 Myr along the northern continent-ocean boundary (COB). A southward ridge jump of ˜20 km occurred around 23.6 Ma in the East Subbasin; this timing also slightly varied along the ridge and was coeval to the onset of seafloor spreading in the Southwest Subbasin, which propagated for about 400 km southwestward from ˜23.6 to ˜21.5 Ma. The terminal age of seafloor spreading is ˜15 Ma in the East Subbasin and ˜16 Ma in the Southwest Subbasin. The full spreading rate in the East Subbasin varied largely from ˜20 to ˜80 km/Myr, but mostly decreased with time except for the period between ˜26.0 Ma and the ridge jump (˜23.6 Ma), within which the rate was the fastest at ˜70 km/Myr on average. The spreading rates are not correlated, in most cases, to magnetic anomaly amplitudes that reflect basement magnetization contrasts. Shipboard magnetic measurements reveal at least one magnetic reversal in the top 100 m of basaltic layers, in addition to large vertical intensity variations. These complexities are caused by late-stage lava flows that are magnetized in a different polarity from the primary basaltic layer emplaced during the main phase of crustal accretion. Deep tow magnetic modeling also reveals this smearing in basement magnetizations by incorporating a contamination coefficient of 0.5, which partly alleviates the problem of assuming a magnetic blocking model of constant thickness and uniform magnetization. The primary contribution to magnetic anomalies of the SCS is not in the top 100 m of the igneous basement.

Li, Chun-Feng; Xu, Xing; Lin, Jian; Sun, Zhen; Zhu, Jian; Yao, Yongjian; Zhao, Xixi; Liu, Qingsong; Kulhanek, Denise K.; Wang, Jian; Song, Taoran; Zhao, Junfeng; Qiu, Ning; Guan, Yongxian; Zhou, Zhiyuan; Williams, Trevor; Bao, Rui; Briais, Anne; Brown, Elizabeth A.; Chen, Yifeng; Clift, Peter D.; Colwell, Frederick S.; Dadd, Kelsie A.; Ding, Weiwei; Almeida, Iván. Hernández; Huang, Xiao-Long; Hyun, Sangmin; Jiang, Tao; Koppers, Anthony A. P.; Li, Qianyu; Liu, Chuanlian; Liu, Zhifei; Nagai, Renata H.; Peleo-Alampay, Alyssa; Su, Xin; Tejada, Maria Luisa G.; Trinh, Hai Son; Yeh, Yi-Ching; Zhang, Chuanlun; Zhang, Fan; Zhang, Guo-Liang

2014-12-01

266

Gravity and magnetic anomalies and the deep structure of the Parnaiba cratonic basin, Brazil  

E-print Network

Gravity and magnetic anomalies and the deep structure of the Parnaiba cratonic basin, Brazil A. B profile across the Parnaiba cratonic basin in NorthEast Brazil. The purpose of this project is to acquire margin of Parnaíba Basin, Brazil. Geophysics 64: 337-356. Ussami N, Cogo de Sa N, Molina EC. 1993

Watts, A. B. "Tony"

267

Predicted current densities in the brain during transcranial electrical stimulation  

PubMed Central

Objective We sought an electrical modeling approach to evaluate the potential application of finite element method (FEM) modeling to predict current pathways and intensities in the brain after transcranial electrical stimulation. Methods A single coronal MRI section through the head, including motor cortex, was modeled using FEM. White matter compartments with both anatomically realistic anisotropies in resistivity and with a homogeneous resistivity were modeled. Current densities in the brain were predicted for electrode sites on the scalp and after theoretical application of a conductive head restraint device. Results Localized current densities were predicted for the model with white matter anisotropies. Differences in predicted peak current densities were related to location of stimulation sites relative to deep sulci in the brain and scalp shunting that was predicted to increase with inter-electrode proximity. A conductive head restraint device was predicted to shunt current away from the brain when a constant current source was used. Conclusions The complex geometry of different tissue compartments in the head and their contrasting resistivities may jointly determine the strength and location of current densities in the brain after transcranial stimulation. This might be predictable with FEM incorporating white matter anisotropies. Conductive head restraint devices during surgery may be contraindicated with constant current stimulation. Significance Individually optimized tcMEP monitoring and localized transcranial activation in the brain might be possible through FEM modeling. PMID:16644273

Holdefer, R. N.; Sadleir, R.; Russell, M. J.

2008-01-01

268

Paired-pulse transcranial magnetic stimulation reveals probability-dependent changes in functional connectivity between right inferior frontal cortex and primary motor cortex during go/no-go performance  

PubMed Central

The functional role of the right inferior frontal cortex (rIFC) in mediating human behavior is the subject of ongoing debate. Activation of the rIFC has been associated with both response inhibition and with signaling action adaptation demands resulting from unpredicted events. The goal of this study is to investigate the role of rIFC by combining a go/no-go paradigm with paired-pulse transcranial magnetic stimulation (ppTMS) over rIFC and the primary motor cortex (M1) to probe the functional connectivity between these brain areas. Participants performed a go/no-go task with 20% or 80% of the trials requiring response inhibition (no-go trials) in a classic and a reversed version of the task, respectively. Responses were slower to infrequent compared to frequent go trials, while commission errors were more prevalent to infrequent compared to frequent no-go trials. We hypothesized that if rIFC is involved primarily in response inhibition, then rIFC should exert an inhibitory influence over M1 on no-go (inhibition) trials regardless of no-go probability. If, by contrast, rIFC has a role on unexpected trials other than just response inhibition then rIFC should influence M1 on infrequent trials regardless of response demands. We observed that rIFC suppressed M1 excitability during frequent no-go trials, but not during infrequent no-go trials, suggesting that the role of rIFC in response inhibition is context dependent rather than generic. Importantly, rIFC was found to facilitate M1 excitability on all low frequent trials, irrespective of whether the infrequent event involved response inhibition, a finding more in line with a predictive coding framework of cognitive control. PMID:24282398

van Campen, A. Dilene; Neubert, Franz-Xaver; van den Wildenberg, Wery P. M.; Ridderinkhof, K. Richard; Mars, Rogier B.

2013-01-01

269

Short and long duration transcranial direct current stimulation (tDCS) over the human hand motor area  

Microsoft Academic Search

The aim of the present paper is to study effects of short and long duration transcranial direct current stimulation (tDCS)\\u000a on the human motor cortex. In eight normal volunteers, motor evoked potentials (MEPs) induced by transcranial magnetic stimulation\\u000a (TMS) were recorded from the right first dorsal interosseous muscle, and tDCS was given with electrodes over the left primary\\u000a motor cortex

Toshiaki Furubayashi; Yasuo Terao; Noritoshi Arai; Shingo Okabe; Hitoshi Mochizuki; Ritsuko Hanajima; Masashi Hamada; Akihiro Yugeta; Satomi Inomata-Terada; Yoshikazu Ugawa

2008-01-01

270

[Modulation of cortical excitability by transcranial direct current stimulation].  

PubMed

Modulation of cerebral excitability is thought to be one mechanism underlying the pharmacological treatment of neuropsychiatric diseases such as epilepsy, depression, and dystonia. Repetitive transcranial magnetic stimulation (rTMS) has been tested for several years as a nonpharmacological, noninvasive method of directly influencing patients' cortical functions. We present an overview of the more easily performed transcranial direct current stimulation (tDCS) with weak current, which produces distinctly more pronounced changes in excitability than rTMS. The basic underlying mechanism is a shift in the resting membrane potential towards either hyper- or depolarisation, depending on stimulation polarity. This in turn leads to changes in the excitability of cortical neurons. Anodic stimulation increases cortical excitability, while cathodic stimulation decreases it. These changes persist after the end of stimulation if the stimulation lasts long enough, i.e., at least several minutes. The duration of this aftereffect can be controlled through the duration and intensity of the stimulation. Transcranial direct current stimulation essentially allows a focal, selective, reversible, pain-free, and noninvasive induction of changes in cortical excitability, the therapeutic potential of which must be evaluated in clinical studies, once possible risk factors have been assessed. PMID:12040980

Nitsche, M A; Liebetanz, D; Tergau, F; Paulus, W

2002-04-01

271

Radiation shielding for deep space manned missions by cryogen free superconducting magnets.  

NASA Astrophysics Data System (ADS)

In last years some activity was dedicated to the solution of the following problem: can be artificially created, around a space vehicle in a manned interplanetary travel or around a manned `space base' in deep space, a magnetic field approaching as much as possible the terrestrial one in terms of bending power on the arriving particles? Preliminary evaluations for active shielding based on superconducting magnets were made a few years ago in ESA supported studies. The present increasing interest of permanent space `bases' located in `deep' space requires that this activity continue toward the goal of protecting from Galactic Cosmic Ray (GCR) a large volume `habitat', allowing long duration permanence in space to citizens conducting there `normal' activities besides to a restricted number of astronauts. The problem had to be stated at this global scale because it must be afforded as soon as possible for preparing the needed technologies and their integration in the spacecraft designs for the future manned exploration and for inhabitation of deep space. The realization of the magnetic protection of large volume habitats by well-established nowadays materials and techniques is in principle possible, but not workable in practice for the huge required mass of the superconductor, the too low operating temperature (10K) and the corresponding required cooling power and thermal shielding. The concept of Cryogen Free Superconducting Magnets is the only one practicable. Fast progress in the production of reliable High Temperature Superconducting (HTS) or MgB2 cables and of cryocoolers suitable for space operation opens the perspective of practicable solutions. Quantitative evaluations for the protection of large volume habitats in deep space from GCRs are reported and discussed.

Spillantini, Piero

272

A wireless batteryless deep-seated implantable ultrasonic pulser-receiver powered by magnetic coupling.  

PubMed

This study tests a deep-seated implantable ultrasonic pulser-receiver, powered wirelessly by magnetic coupling. A 30-cm energy-transmitting coil was designed to wrap around the body, and was driven by a current of 1.2 A rms at a frequency of 5.7 MHz to generate a magnetic field. A 2-cm receiving coil was positioned at the center of the primary coil for receiving the magnetic energy and powering the implantable device. A capacitor-diode voltage multiplier in the implantable circuit was used to step-up the receiving coil voltage from 12.5 to 50 V to operate an ultrasonic pulser. FEA magnetic field simulations, bench-top, and ex vivo rabbit measurements showed that the magnetic energy absorption in body tissue is negligible and that the magnetic coupling is not sensitive to receiving coil placement. The receiving coil and the power conditioning circuits in the implantable device do not contain ferromagnetic material, so a magnetic-resonance-compatible device can be achieved. A 5-MHz ultrasound transducer was used to test the implantable circuit, operating in pulse-echo mode. The received echo was amplified, envelope-detected, frequency-modulated, and transmitted out of the rabbit body by a radio wave. The modulated echo envelope signal was received by an external receiver located about 10 cm away from the primary coil. The study concludes that operation of a batteryless and wireless deep-seated implantable ultrasonic pulser-receiver powered by coplanar magnetic coupling is feasible. PMID:21693403

Tang, Sai Chun; Jolesz, Ferenc A; Clement, Gregory T

2011-06-01

273

Dose and timing effect of etomidate on motor evoked potentials elicited by transcranial electric or magnetic stimulation in the monkey and baboon  

Microsoft Academic Search

Objective  Etomidate has been shown to both enhance and depress the cortical amplitude of somatosensory evoked potentials (SSEP) depending\\u000a on the dose used. Similar amplitude increases with etomidate and motor evoked potentials resulting from cortical magnetic\\u000a (tcMMEP) and electric (tcEMEP) stimulation have not been consistent. We used a primate model to elucidate the time and dose\\u000a characteristics of the effect.\\u000a \\u000a \\u000a \\u000a Methods  

Tod Sloan; J. Rogers

2009-01-01

274

Widespread Magnetofossil Occurrences in Deep-sea Sediments and Implications for Paleo- and Environmental Magnetism (Invited)  

NASA Astrophysics Data System (ADS)

Recent progress in rock magnetism has enabled quantitative estimation of magnetizations carried by magnetofossils. Using FORC diagrams, IRM component analyses, ferromagnetic resonance spectroscopy, low-temperature magnetometry, and transmission electron microscopy, it has been found that magnetofossils are widespread in deep-sea sediments and are often a dominant constituent of magnetic mineral assemblages. Some studies have documented a relationship between increased magnetofossil abundances and enhanced oceanic productivity induced by iron fertilization via eolian dust. The morphology of magnetosomes, which is species specific, may reflect a preference of magnetotactic bacteria for particular redox conditions. Dominant magnetofossil morphologies in sediments (cubo-octahedral vs. elongated) can be detected with rock magnetic techniques. Thus, magnetofossil abundance and morphology have considerable potential as paleoenvironmental indicators. It is widely held that magnetotactic bacteria live at or below the oxic-anoxic transition zone (OATZ) in chemically stratified aquatic environments. If so, it is expected that sediments that contain magnetofossils would have acquired their remanent magnetization at around the OATZ, and that the magnetization carried by magnetofossils will be delayed with respect to a pDRM carried by detrital magnetic minerals if the OATZ lies below the surface mixed layer and the pDRM acquisition zone. However, magnetofossils often dominate the magnetic mineral assemblage even in marine red clays that lack an OATZ. Changes in the relative abundance of biogenic and detrital magnetic components can be estimated from the ratio of ARM susceptibility to SIRM; a smaller average magnetic grain size and weaker magnetostatic interactions in the biogenic component causes higher ARM susceptibility. In relative paleointensity estimations, the kARM/SIRM ratio sometimes anti-correlates with normalized intensity regardless of the choice of normalizer (ARM or IRM). This implies that changes in relative abundance of biogenic magnetite may not be well compensated for by the widely used normalizers and may contaminate relative paleointensity records.

Yamazaki, T.; Roberts, A. P.

2013-12-01

275

Treatment of depression with transcranial direct current stimulation (tDCS): A Review  

Microsoft Academic Search

Major Depression Disorder (MDD) is usually accompanied by alterations of cortical activity and excitability, especially in prefrontal areas. These are reflections of a dysfunction in a distributed cortico-subcortical, bihemispheric network. Therefore it is reasonable to hypothesize that altering this pathological state with techniques of brain stimulation may offer a therapeutic target. Besides repetitive transcranial magnetic stimulation, tonic stimulation with weak

Michael A. Nitsche; Paulo S. Boggio; Felipe Fregni; Alvaro Pascual-Leone

2009-01-01

276

More female patients and fewer stimuli per session are associated with the short-term antidepressant properties of repetitive transcranial magnetic stimulation (rTMS): a meta-analysis of 54 sham-controlled studies published between 1997–2013  

PubMed Central

Background Repetitive transcranial magnetic stimulation (rTMS) of the dorsolateral prefrontal cortex (DLPFC) appears to have short-term antidepressant properties. The aim of the current study was to update our previous meta-analysis and to investigate factors associated with the antidepressant properties of rTMS. Method Following a systematic literature search conducted in Medline and PsycInfo, N=14 sham-controlled, parallel design studies (published after 2008 to August 2013) that had utilized rTMS of the DLPFC in major depression were included in the current meta-analysis. The sensitivity and moderator analyses also included data from N=40 studies (published in 1997–2008) from our previous meta-analysis. The effect size (Cohen’s d) in each study was the standardized difference in mean depression scores (on Hamilton Depression Rating Scale, Beck Depression Inventory, Montgomery Åsberg Depression Rating Scale) from baseline to final (after last session) in rTMS compared to sham groups. Results According to a random-effects model with inverse-variance weights, depression scores were significantly reduced after rTMS compared to sham in studies published from 2008–2013 based on N=659 patients (overall mean weighted d=?0.42, 95% confidence interval: ?0.66, ?0.18, P=0.001). Combining studies from our past and current meta-analyses (published in 1997–2013; N=54) revealed that depression was significantly reduced after left-fast (>1 Hz), right-slow (?1 Hz), and bilateral (or sequential) rTMS of DLPFC compared to sham. Significant antidepressant properties of rTMS were observed in studies with patients who were treatment resistant, unipolar (or bipolar), non-psychotic, medication-free (or started on antidepressants concurrently with rTMS). According to univariate meta-regressions, depression scores were significantly lower in studies with more female patients and fewer stimuli per session. There was little evidence that publication bias occurred in the analysis. Conclusion According to this study, the largest meta-analysis to date, short-term antidepressant properties of rTMS are independent of concurrent antidepressants and might depend on sex and the number of stimuli per session. PMID:24855360

Kedzior, Karina Karolina; Azorina, Valeriya; Reitz, Sarah Kim

2014-01-01

277

Different magnetic resonance imaging patterns after transcranial magnetic resonance-guided focused ultrasound of the ventral intermediate nucleus of the thalamus and anterior limb of the internal capsule in patients with essential tremor or obsessive-compulsive disorder.  

PubMed

OBJECT The authors report different MRI patterns in patients with essential tremor (ET) or obsessive-compulsive disorder (OCD) after transcranial MR-guided focused ultrasound (MRgFUS) and discuss possible causes of occasional MRgFUS failure. METHODS Between March 2012 and August 2013, MRgFUS was used to perform unilateral thalamotomy in 11 ET patients and bilateral anterior limb capsulotomy in 6 OCD patients; in all patients symptoms were refractory to drug therapy. Sequential MR images were obtained in patients across a 6-month follow-up period. RESULTS For OCD patients, lesion size slowly increased and peaked 1 week after treatment, after which lesion size gradually decreased. For ET patients, lesions were visible immediately after treatment and markedly reduced in size as time passed. In 3 ET patients and 1 OCD patient, there was no or little temperature rise (i.e., < 52°C) during MRgFUS. Successful and failed patient groups showed differences in their ratio of cortical-to-bone marrow thickness (i.e., skull density). CONCLUSIONS The authors found different MRI pattern evolution after MRgFUS for white matter and gray matter. Their results suggest that skull characteristics, such as low skull density, should be evaluated prior to MRgFUS to successfully achieve thermal rise. PMID:25343176

Jung, Hyun Ho; Chang, Won Seok; Rachmilevitch, Itay; Tlusty, Tal; Zadicario, Eyal; Chang, Jin Woo

2015-01-01

278

Diagnosis of deep infiltrating endometriosis: accuracy of magnetic resonance imaging and transvaginal 3D ultrasonography  

Microsoft Academic Search

Purpose  To compare two different imaging modalities, magnetic resonance (MR), and three-dimensional sonography (3DUS), in order to\\u000a evaluate the specific role in preoperative work-up of deep infiltrating endometriosis.\\u000a \\u000a \\u000a \\u000a \\u000a Materials and methods  33 women with endometriosis underwent 3DUS and MR followed by surgical and histopathological investigations. Investigators\\u000a described the disease extension in the following sites: torus uterinus and uterosacral ligaments (USL), vagina, rectovaginal-septum,

Rosario Francesco Grasso; Vincenza Di Giacomo; Pietro Sedati; Ornella Sizzi; Giuseppe Florio; Eliodoro Faiella; Alfonso Rossetti; Riccardo Del Vescovo; Bruno Beomonte Zobel

2010-01-01

279

Search for magnetic monopoles with deep underwater Cherenkov detectors at Lake Baikal  

E-print Network

The deep underwater Cherenkov neutrino telescope NT-200 is currently under construction at Lake Baikal. The "subdetectors" NT-36 (1993-95) and NT-72 (1995-96) have been operating successfully over 3 years. Various techniques have been developed to search for magnetic monopoles with these arrays. Here we describe a method used to detect superheavy slowly moving (beta = v/c = 0.00001 - 0.001) monopoles catalyzing baryon decay. We present results obtained from the preliminary analysis of the data taken with NT-36 detector in 1993. Furthermore, possibilities to observe faster (beta = 0.2 - 1) monopoles via other effects are discussed.

Belolaptikov, I A; Borisovets, B A; Budnev, N M; Chensky, A G; Danilchenko, I A; Djilkibaev, J A M; Dobrynin, V I; Domogatsky, G V; Doroshenko, A A; Fialkovsky, S V; Gaponenko, O N; Garus, A A; Gress, O A; Gress, T A; Heukenkamp, H; Karle, A; Klabukov, A M; Klimov, A I; Klimushin, S I; Koshechkin, A P; Kulepov, V F; Kuzmichov, L A; Lubsandorzhiev, B K; Mikolajski, T; Milenin, M B; Mirgazov, R R; Moroz, A V; Moseiko, N I; Nikiforov, S A; Osipova, E A; Panfilov, A I; Parfenov, Yu V; Pavlov, A A; Petukhov, D P

1996-01-01

280

Deep-sea Vector Magnetic Anomalies over the Bayonnaise Knoll Caldera (Izu-Ogasawara Arc) (Invited)  

NASA Astrophysics Data System (ADS)

The Bayonnaise Knoll caldera is located on the eastern margin of the backarc rift zone of the Izu-Ogasawara island arc. The caldera rim is ~3 km in diameter and 100-200 m high from the caldera floor 840-920 m deep. A large active hydrothermal field associated with sulfide deposit, called the Hakurei site, has been found at the foot of the southeastern caldera wall. We conducted deep-sea magnetic measurements using autonomous underwater vehicles to map ~75 % of an area 3 km by 4 km in the caldera. The magnetic vector field data were collected at 40-150 m altitude along the survey lines spaced 80-200 m apart. We improved the conventional correction method applied for removing the effect of vehicle magnetization, which greatly enhanced the precision of the resulting vector anomalies and allowed us to use the vector anomaly instead of the total intensity anomaly for inversion analysis. The magnetization distribution obtained using the vector anomaly was significantly different from the one obtained using the total intensity anomaly, especially in areas where the survey tracks were widely spaced. The aliasing effect appears in areas of sparse data distribution, and the magnetic field is more correctly calculated from the vector anomaly than the total intensity anomaly. The magnetization distribution in the caldera has two major features: a ~1.5-km wide belt of high magnetization, trending NNW-SSE through the caldera, and a clear low magnetization zone, ~300 m x ~500 m wide, extending over the Hakurei site. The high magnetization belt is considered to reflect basaltic volcanism associated with the backarc rifting that occurred after the formation of the Bayonnaise Knoll. The low magnetization zone is interpreted as the alteration zone resulting from the hydrothermal activity. Several zones of localized high magnetization are recognized within the high magnetization belt, some of them in the caldera wall adjacent to the low magnetization zone of the Hakurei site. We speculate that intensive magma intrusion occurred beneath the caldera wall and has provided the heat to generate hydrothermal fluid, which has been spouting out through the caldera wall faults. The surface expression of the vent field extends beyond the alteration zone inferred from the magnetization distribution, spreading upwards in the caldera wall. High-resolution topography around the Hakurei site indicates that the hydrothermal vents are generally distributed over a landform of slope failure. These observations would imply that hydrothermal fluid rising up in the up-flow zone moves laterally as well when it comes near the seafloor, probably along numerous fractures and fissures in the caldera wall. The distribution of pre-existing faults and fractures may rather control the fluid flow pathways in the shallow part and condition the surface extent of the vent field.

Honsho, C.; Ura, T.; Kim, K.

2013-12-01

281

Design and testing of planar magnetic micromotors fabricated by deep x-ray lithography and electroplating  

SciTech Connect

The successful design and testing of a three-phase planar integrated magnetic micromotor is presented. Fabrication is based on a modified deep X-ray lithography and electroplating or LIGA process. Maximum rotational speeds of 33,000 rpm are obtained in air with a rotor diameter of 285 {mu}m and do not change when operated in vacuum. Real time rotor response is obtained with an integrated shaft encoder. Long lifetime is evidenced by testing to over 5(10){sup 7} ration cycles without changes in performance. Projected speeds of the present motor configuration are in the vicinity of 100 krpm and are limited by torque ripple. Higher speeds, which are attractive for sensor applications. require constant torque characteristic excitation as is evidenced by ultracentrifuge and gyroscope design. Further understanding of electroplated magnetic material properties will drive these performance improvements.

Guckel, H.; Christenson, T.R.; Skrobis, K.J.; Klein, J. [Wisconsin Univ., Madison, WI (United States). Dept. of Electrical and Computer Engineering; Karnowsky, M. [Sandia National Labs., Albuquerque, NM (United States)

1993-05-01

282

Three-dimensional modeling of a magnetic reversal boundary from inversion of deep-tow measurements  

NASA Astrophysics Data System (ADS)

A near-bottom magnetic survey was conducted over the Brunhes/Matuyama reversal boundary near the East Pacific Rise crest at 21° N. Magnetic measurements were made on a level plane approximately 200 m above the sea floor using the Marine Physical Laboratory's deep-tow vehicle, with precise transponder navigation. Track density was high both parallel and perpendicular to the magnetic lineations in order to study fine scale deviations from two-dimensionality. The magnetic field on a gridded map was inverted to obtain the crustal magnetization distribution (including the effects of topography) by extension of the Fourier technique of Parker and Huestis [1974]. Linearity of sources parallel to the spreading center was not assumed, nor was upward continuation necessary in this treatment. We found that the polarity transition boundary is extremely straight and sharp and is very close to two-dimensional even on a scale of hundreds of meters. Deviations from two-dimensionality, however, occur within the magnetized blocks away from the transition zone. The polarity transition width is narrow, only 1000 m to 1400 m throughout the study area. This suggests a zone of crustal emplacement which is only 600-1000 m wide at the spreading center, which is in excellent agreement with geologic observations in the area. Comparisons are made with a two-dimensional treatment of the same data from profiles (i.e., assuming linearity of sources). These studies also document a long-wavelength (? 60 km) sinuosity in the trend of the magnetic anomalies. This sinuosity is the result of offsets of the spreading center which are not transform faults but which involve a component of strike slip motion subparallel to the spreading center.

MacDonald, K. C.; Miller, S. P.; Huestis, S. P.; Spiess, F. N.

1980-07-01

283

Rock magnetic signatures in diagenetically altered sediments from the Niger deep-sea fan  

NASA Astrophysics Data System (ADS)

Diagenesis has extensively affected the magnetic mineral inventory of organic-rich late Quaternary sediments in the Niger deep-sea fan. Changes in concentration, grain size, and coercivity document modifications of the primary magnetic mineral assemblages at two horizons. The first front, the modern iron redox boundary, is characterized by a drastic decline in magnetic mineral content, coarsening of the grain size spectrum, and reduction in coercivity. Beneath a second front, the transition from the suboxic to the sulfidic anoxic domain, a further but less pronounced decrease in concentration and bulk grain size occurs. Finer grains and higher coercive magnetic constituents substantially increase in the anoxic environment. Low- and high-temperature experiments were performed on bulk sediments and on extracts which have also been examined by X-ray diffraction. Thermomagnetic analyses proved ferrimagnetic titanomagnetites of terrigenous provenance as the principal primary magnetic mineral components. Their broad range of titanium contents reflects the volcanogenic traits of the Niger River drainage areas. Diagenetic alteration is not only a grain size selective process but also critically depends on titanomagnetite composition. Low-titanium compounds are less resistant to diagenetic dissolution. Intermediate titanium content titanomagnetite thus persists as the predominant magnetic mineral fraction in the sulfidic anoxic sediments. At the Fe redox boundary, precipitation of authigenic, possibly bacterial, magnetite is documented. The presence of hydrogen sulfide in the pore water suggests a formation of secondary magnetic iron sulfides in the anoxic domain. Grain size-specific data argue for a gradual development of a superparamagnetic and single-domain iron sulfide phase in this milieu, most likely greigite.

Dillon, Melanie; Bleil, Ulrich

2006-03-01

284

Correlation of transcranial Doppler ultrasonography with MRI and MRA in the evaluation of sickle cell disease patients with prior stroke  

Microsoft Academic Search

We prospectively evaluated a group of patients with sickle cell disease and a clinical history of prior stroke, comparing transcranial Doppler sonography (TCD) to both magnetic resonance imaging (MRI) and magnetic resonance angiography (MRA) to determine its efficacy for the detection of flow abnormalities associated with prior cerebral infarction. Using MRI as the standard examination, there was 94% sensitivity and

M. S. Kogutt; S. S. Goldwag; K. L. Gupta; K. Kaneko; J. R. Humbert

1994-01-01

285

Optimal coil orientation for transcranial magnetic stimulation.  

PubMed

We study the impact of coil orientation on the motor threshold (MT) and present an optimal coil orientation for stimulation of the foot. The result can be compared to results of models that predict this orientation from electrodynamic properties of the media in the skull and from orientations of cells, respectively. We used a robotized TMS system for precise coil placement and recorded motor-evoked potentials with surface electrodes on the abductor hallucis muscle of the right foot in 8 healthy control subjects. First, we performed a hot-spot search in standard (lateral) orientation and then rotated the coil in steps of 10° or 20°. At each step we estimated the MT. For navigated stimulation and for correlation with the underlying anatomy a structural MRI scan was obtained. Optimal coil orientation was 33.1 ± 18.3° anteriorly in relation to the standard lateral orientation. In this orientation the threshold was 54 ± 18% in units of maximum stimulator output. There was a significant difference of 8.0 ± 5.9% between the MTs at optimal and at standard orientation. The optimal coil orientations were significantly correlated with the direction perpendicular to the postcentral gyrus ([Formula: see text]). Robotized TMS facilitates sufficiently precise coil positioning and orientation to study even small variations of the MT with coil orientation. The deviations from standard orientation are more closely matched by models based on field propagation in media than by models based on orientations of pyramidal cells. PMID:23593200

Richter, Lars; Neumann, Gunnar; Oung, Stephen; Schweikard, Achim; Trillenberg, Peter

2013-01-01

286

Structural setting and magnetic properties of pseudotachylyte in a deep crustal shear zone, western Canadian shield  

NASA Astrophysics Data System (ADS)

Seismic slip commonly produces pseudotachylytes, a glassy vein-filling substance that is typically interpreted as either a frictional melt or an ultra-triturated cataclasite. In either form, pseudotachylytes are commonly magnetite enriched, even in magnetite-free host rocks, and therefore are potentially useful as high fidelity recorders of natural magnetic fields at the time of slip in a wide array of lithologies. Pseudotachylytes generally have high magnetic susceptibility and thus should preserve the dominant field present as the material passes the Curie temperatures of magnetic minerals, primarily magnetite. Two potential sources have been proposed for the dominant magnetic field recorded: the earth's magnetic field at the time of slip or the temporary and orders of magnitude more intense field created by the presence of coseismic currents along the failure plane. Pseudotachylytes of the Cora Lake shear zone (CLsz) in the Athabasca Granulite Terrain, western Canadian shield, are consistently hosted in high strain ultramylonitic orthogneiss. Sinistral and extensional oblique-slip in the CLsz occurred at high-pressure granulite-grade conditions of ~1.0 GPa and >800°C and may have persisted to somewhat lower P-T conditions (~0.8 GPa, 700 °C) during ductile deformation. Pseudotachylyte-bearing slip surfaces have sinistral offset, matching the larger shear zone, and clasts of wall rock in the more brecciated veins display field evidence for ductile shear along the same plane prior to brittle failure. The presence of undeformed pseudotachylyte in kinematically compatible fracture arrays localized in ultramylonite indicates that brittle failure may have occurred in the waning stages of shear zone activity and at similar deep crustal conditions. Field-documented occurrences of pseudotachylyte include 2 cm-thick veins that run subparallel to mylonitic foliation and contain small flow-aligned clasts and large, heavily brecciated foliation-crosscutting zones up to seven centimeters thick. Field studies of pseudotachylytes in the Cora Lake shear zone confirm high magnetic susceptibility, both by strongly interfering with hand-held compasses and by testing with a hand-held magnetic susceptibility meter (over 7 x10-2 SI). More detailed laboratory analyses are planned in order to clarify the spatial association between veins of pseudotachylyte and areas of magnetic susceptibility. Investigation is also currently underway to determine if the remnant field preserved in these pseudotachylytes dominantly reflects a signature of the Earth's paleomagnetic field or that of a lightning-like coseismic current.

Orlandini, O. F.; Mahan, K. H.; Brown, L. L.; Regan, S.; Williams, M. L.

2012-12-01

287

Transcranial sonography in Huntington's disease.  

PubMed

Transcranial sonography (TCS) has become a reliable and sensitive diagnostic tool in the evaluation of extrapyramidal movement disorders, especially in the differentiation of Parkinsonian syndromes. Although only rarely reported, TCS reveals also signal alterations of basal ganglia in Huntington's disease (HD). Distinct findings are related to all of the three symptom domains of the clinical triad of the disease. The TCS finding of substantia nigra hyperechogenicity was related to higher clinical disease severity. A poorer cognitive performance correlated with larger width of third ventricle. Moreover, widths of frontal horns of lateral ventricles measured with TCS corresponded closely to diameters estimated by CT imaging. Depressive symptoms were found to be associated with abnormal echogenicity of mesencephalic raphe structures. Furthermore, a larger number of CAG repeats in the huntingtin gene correlated with presence of SN hyperechogenicity. This review provides information about the examination procedure and its diagnostic value in HD. Possible morphological and pathophysiological mechanisms leading to changes in the reflection of ultrasound waves are discussed in the context of established neuroimaging modalities. PMID:20692506

Krogias, Christos; Eyding, Jens; Postert, Thomas

2010-01-01

288

Transcranial Doppler ultrasonography: year 2000 update.  

PubMed

In this update, the main clinical applications of transcranial Doppler ultrasonography are reassessed. A specific format for technology assessment, personal experience, and an extensive review of the literature form the basis of the evaluation. The document is approved by the American Society of Neuroimaging and the Neurosonology Research Group of the World Federation of Neurology. PMID:10800264

Babikian, V L; Feldmann, E; Wechsler, L R; Newell, D W; Gomez, C R; Bogdahn, U; Caplan, L R; Spencer, M P; Tegeler, C; Ringelstein, E B; Alexandrov, A V

2000-04-01

289

Acute hemispheric stroke: Correlation between three-dimensional transcranial Doppler, MR-angiography, CT and clinical findings  

Microsoft Academic Search

We examined 50 ischemic stroke patients and 67 controls free of vascular disease, intra- or extracranial. We assessed all subjects clinically by neurological examination (quantified on the Canadian Neurological Scale or CNS), by three-dimensional transcranial Doppler sonography (TCD-3D) and by computed tomography (CT) within 24 h of the acute event, repeating CT 15 days later. 15 patients also underwent magnetic

S. Viola; M. G. Tenaglia; E. De Leonardis; L. Aquilone; D. Gambi

1993-01-01

290

MR-guided transcranial brain HIFU in small animal models  

PubMed Central

Recent studies have demonstrated the feasibility of transcranial High Intensity Focused Ultrasound (HIFU) therapy in the brain using adaptive focusing techniques. However, the complexity of the procedures imposes to provide an accurate targeting, monitoring and control of this emerging therapeutic modality in order to ensure the safety of the treatment and avoid potential damaging effects of ultrasound on healthy tissues. For these purposes, a complete workflow and setup for HIFU treatment under Magnetic Resonance (MR) guidance is proposed and implemented in rats. For the first time, tissue displacements induced by the acoustic radiation force are detected in vivo in brain tissues and measured quantitatively using motion-sensitive MR sequences. Such a valuable target control prior to treatment assesses the quality of the focusing pattern in situ and enables to estimate the acoustic intensity at focus. This MR-Acoustic radiation force imaging is then correlated with conventional MR-Thermometry sequences which are used to follow the temperature changes during the HIFU therapeutic session. Last, pre and post treatment Magnetic Resonance Elastography (MRE) datasets are acquired and evaluated as a new potential way to non invasively control the stiffness changes due to the presence of thermal necrosis. As a proof of concept, MRguided HIFU is performed in vitro in turkey breast samples and in vivo in transcranial rat brain experiments. The experiments are conducted using a dedicated MR compatible HIFU setup in a high field MRI scanner (7T). Results obtained on rats confirmed that both the MR localization of the US focal point and the pre and post HIFU measurement of the tissue stiffness, together with temperature control during HIFU are feasible and valuable techniques for an efficient monitoring of HIFU in the brain. Brain elasticity appears to be more sensitive to the presence of oedema than to tissue necrosis. PMID:20019400

Larrat, Benoît; Pernot, Mathieu; Aubry, Jean-François; Dervishi, Elvis; Sinkus, Ralph; Seilhean, Danielle; Marie, Yannick; Boch, Anne-Laure; Fink, Mathias; Tanter, Mickaël

2010-01-01

291

Comparison of magnetic resonance imaging sequences for depicting the subthalamic nucleus for deep brain stimulation.  

PubMed

Electrodes are surgically implanted into the subthalamic nucleus (STN) of Parkinson's disease patients to provide deep brain stimulation. For ensuring correct positioning, the anatomic location of the STN must be determined preoperatively. Magnetic resonance imaging has been used for pinpointing the location of the STN. To identify the optimal imaging sequence for identifying the STN, we compared images produced with T2 star-weighted angiography (SWAN), gradient echo T2*-weighted imaging, and fast spin echo T2-weighted imaging in 6 healthy volunteers. Our comparison involved measurement of the contrast-to-noise ratio (CNR) for the STN and substantia nigra and a radiologist's interpretations of the images. Of the sequences examined, the CNR and qualitative scores were significantly higher on SWAN images than on other images (p < 0.01) for STN visualization. Kappa value (0.74) on SWAN images was the highest in three sequences for visualizing the STN. SWAN is the sequence best suited for identifying the STN at the present time. PMID:25113409

Nagahama, Hiroshi; Suzuki, Kengo; Shonai, Takaharu; Aratani, Kazuki; Sakurai, Yuuki; Nakamura, Manami; Sakata, Motomichi

2015-01-01

292

Computational models of electroconvulsive therapy and transcranial direct current stimulation for treatment of depression.  

E-print Network

??Electroconvulsive therapy (ECT) and transcranial direct current stimulation (tDCS) are two important forms of transcranial electrical stimulation in clinical psychiatry. They have shown impressive therapeutic… (more)

Bai, Siwei

2012-01-01

293

Predicting Vigilance Performance Under Transcranial Direct Current Stimulation.  

E-print Network

??A brain stimulation technology called transcranial direct current stimulation (tDCS) may potentially mitigate the vigilance decrement. To practically use such technology, however, a model is… (more)

Bridges, Nathaniel Reese

2011-01-01

294

Development of precise measurement systems for deep-sea electrical and magnetic explorations by ROV and AUV  

NASA Astrophysics Data System (ADS)

It is generally not easy to obtain the fine-scale structure of the oceanic crust with accuracy better than several tens of meters, because the deep sea prevents us from approaching the bottom in most parts of the oceans. The necessity of such detailed information, however, has increased in researches and developments of the ocean floor. For instance, it is essential in development of ocean floor resources like sea-floor hydrothermal deposits and methane hydrate in order to estimate accurate abundance of those resources. Therefore, it is very important to develop some instruments for precise measurements of the oceanic crust. From this standpoint, we have developed new measurement systems for electrical and magnetic explorations by Remotely Operated Vehicle (ROV) and Autonomous Underwater Vehicle (AUV). In our project, the main target is sea-floor hydrothermal deposits. We are working on research and development regarding measurement of the magnetic field with high resolution and high sampling rate, electrical exploration with accurately controlled source signals, electrical exploration tools for shallow and deep targets, versatile instruments of electrical and magnetic explorations with multi-platforms (deep-tow system, ROV, and AUV), comprehensive analyses of electrical, magnetic, acoustic and thermal data, and so on. We finished basic designs of the magnetic and electrical observation systems last year, and we have been manufacturing each instrument. So far, the first test of the magnetic exploration system was carried out in the Kumano Basin during the R/V Yokosuka cruise in July, 2009. In the test, a vector magnetometer on AUV “Urashima” and a scalar magnetometer hung below towing vehicle “Yokosuka Deep-Tow” successfully detected magnetic anomaly produced by an artificial magnetic body set up on the ocean floor. Details will be reported in another paper by Harada, M. et al. in this meeting. In addition, various performance tests will be planned for check and improvement of the observation systems. For instance, the vector magnetometer will be tested over a volcanic island using a helicopter. The electrical exploration system will be also tested using ROV “Kaiko 7000II” off the northeastern part of Japan during the R/V Kairei cruise. We will present the outline and the current state of the project in this presentation. Note that this project has been supported by the Ministry of Education, Culture, Sports, Science & Technology (MEXT).

Sayanagi, K.; Goto, T.; Harada, M.; Kasaya, T.; Sawa, T.; Nakajima, T.; Isezaki, N.; Takeuchi, A.; Nagao, T.; Matsuo, J.

2009-12-01

295

Transcranial electrical stimulation accelerates human sleep homeostasis.  

PubMed

The sleeping brain exhibits characteristic slow-wave activity which decays over the course of the night. This decay is thought to result from homeostatic synaptic downscaling. Transcranial electrical stimulation can entrain slow-wave oscillations (SWO) in the human electro-encephalogram (EEG). A computational model of the underlying mechanism predicts that firing rates are predominantly increased during stimulation. Assuming that synaptic homeostasis is driven by average firing rates, we expected an acceleration of synaptic downscaling during stimulation, which is compensated by a reduced drive after stimulation. We show that 25 minutes of transcranial electrical stimulation, as predicted, reduced the decay of SWO in the remainder of the night. Anatomically accurate simulations of the field intensities on human cortex precisely matched the effect size in different EEG electrodes. Together these results suggest a mechanistic link between electrical stimulation and accelerated synaptic homeostasis in human sleep. PMID:23459152

Reato, Davide; Gasca, Fernando; Datta, Abhishek; Bikson, Marom; Marshall, Lisa; Parra, Lucas C

2013-01-01

296

Brain Embolism Monitoring with Transcranial Doppler Ultrasound.  

PubMed

Embolism is considered to be the main mechanism leading to brain infarction today; with the introduction of sophisticated neuroimaging tools, its impact is increasingly appreciated. Transcranial Doppler ultrasound allows noninvasive monitoring of in vivo embolism. Acute stroke, internal carotid artery stenosis, several cardiac conditions, internal carotid endarterectomy, and coronary artery bypass graft surgery have been extensively monitored. These investigations and other clinical and neuroimaging studies have expanded the understanding of brain embolism; they suggest it may be appropriate to think of it as a process that occurs in the context of other hemodynamic factors. Differences have been identified among several conditions regarding the temporal profile of embolism and the characteristics of embolic particles. This article presents a brief review of brain embolism monitoring with transcranial Doppler ultrasound. PMID:12777200

Babikian, Viken L.; Wijman, Christine A.

2003-07-01

297

Trans-cranial focused ultrasound without hair shaving: feasibility study in an ex vivo cadaver model  

PubMed Central

In preparing a patient for a trans-cranial magnetic resonance (MR)-guided focused ultrasound procedure, current practice is to shave the patient’s head on treatment day. Here we present an initial attempt to evaluate the feasibility of trans-cranial focused ultrasound in an unshaved, ex vivo human head model. A human skull filled with tissue-mimicking phantom and covered with a wig made of human hair was sonicated using 220- and 710-kHz head transducers to evaluate the feasibility of acoustic energy transfer. Heating at the focal point was measured by MR proton resonance shift thermometry. Results showed that the hair had a negligible effect on focal spot thermal rise at 220 kHz and a 17% drop in temperature elevation when using 710 kHz. PMID:25512865

2013-01-01

298

Boosting brain excitability by transcranial high frequency stimulation in the ripple range  

PubMed Central

Alleviating the symptoms of neurological diseases by increasing cortical excitability through transcranial stimulation is an ongoing scientific challenge. Here, we tackle this issue by interfering with high frequency oscillations (80–250 Hz) via external application of transcranial alternating current stimulation (tACS) over the human motor cortex (M1). Twenty-one subjects participated in three different experimental studies and they received on separate days tACS at three frequencies (80 Hz, 140 Hz and 250 Hz) and sham stimulation in a randomized order. tACS with 140 Hz frequency increased M1 excitability as measured by transcranial magnetic stimulation-generated motor evoked potentials (MEPs) during and for up to 1 h after stimulation. Control experiments with sham and 80 Hz stimulation were without any effect, and 250 Hz stimulation was less efficient with a delayed excitability induction and reduced duration. After-effects elicited by 140 Hz stimulation were robust against inversion of test MEP amplitudes seen normally under activation. Stimulation at 140 Hz reduced short interval intracortical inhibition, but left intracortical facilitation, long interval cortical inhibition and cortical silent period unchanged. Implicit motor learning was not facilitated by 140 Hz stimulation. High frequency stimulation in the ripple range is a new promising non-invasive brain stimulation protocol to increase human cortical excitability during and after the end of stimulation. PMID:20962008

Moliadze, Vera; Antal, Andrea; Paulus, Walter

2010-01-01

299

Magnetic characterisation of present-day deep-sea sediments and sources in the North Atlantic  

E-print Network

formation of North Atlantic Deep Water, which drives the thermohaline circulation. To understand past-821X / 03 / $ ^ see front matter Ã? 2003 Elsevier B.V. All rights reserved. doi:10.1016/S0012-821X(03

300

Carbon: A bane for giant magnetoresistance magnetic multilayers David X. Yang, Harsh Deep Chopra, B. Shashishekar, P. J. Chen, and W. F. Egelhoff  

E-print Network

Carbon: A bane for giant magnetoresistance magnetic multilayers David X. Yang, Harsh Deep Chopra, B magnetoresistance ratio with temperature in epitaxial Fe/MgO/Co2MnSn magnetic tunnel junctions J. Appl. Phys. 110, 073905 (2011) Enhancement of magnetoresistance by ultra-thin Zn wüstite layer Appl. Phys. Lett. 99

Chopra, Harsh Deep

301

Deep-tow magnetic anomaly study of the Pacific Jurassic Quiet Zone and implications for the geomagnetic polarity reversal timescale and  

E-print Network

., 113, B07110, doi:10.1029/2007JB005527. 1. Introduction [2] The Jurassic period appears to be a time of the Jurassic magnetic field. It was once suggested that this Jurassic ``Quiet Zone'' (JQZ) reflects a periodDeep-tow magnetic anomaly study of the Pacific Jurassic Quiet Zone and implications

302

Characterization of deep geothermal energy resources using Electro-Magnetic methods, Belgium  

NASA Astrophysics Data System (ADS)

Sedimentary basins in Northwest Europe have significant potential for low to medium enthalpy, deep geothermal energy resources. These resources are currently assessed using standard exploration techniques (seismic investigations followed by drilling of a borehole). This has enabled identification of geothermal resources but such techniques are extremely costly. The high cost of exploration remains one of the main barriers to geothermal project development due to the lack of capital in the geothermal industry. We will test the possibility of using the Electro-Magnetic (EM) methods to aid identification of geothermal resources in conjunction with more traditional exploration methods. An EM campaign could cost a third of a seismic campaign and is also often a passive technology, resulting in smaller environmental impacts than seismic surveys or drilling. EM methods image changes in the resistivity of the earth's sub-surface using natural or induced frequency dependant variations of electric and magnetic fields. Changes in resistivity can be interpreted as representing different subsurface properties including changes in rock type, chemistry, temperature and/or hydraulic transmissivity. While EM techniques have proven to be useful in geothermal exploration in high enthalpy areas in the last 2-3 years only a handful of studies assess their applicability in low enthalpy sedimentary basins. Challenges include identifying which sub-surface features cause changes in electrical resistivity as low enthalpy reservoirs are unlikely to exhibit the hydrothermally altered clay layer above the geothermal aquifer that is typical for high enthalpy reservoirs. Yet a principal challenge is likely to be the high levels of industrialisation in the areas of interest. Infrastructure such as train tracks and power cables can create a high level of background noise that can obfuscate the relevant signal. We present our plans for an EM campaign in the Flemish region of Belgium. Field techniques will be developed to increase the signal-noise ratio and identify background noise. Firstly, surface noise will be filtered off by non-parametric approaches such as proper orthogonal decomposition. Secondly, the EM signal and newly acquired seismic data will be combined to obtain a multi-dimensional earth model via an inversion process. Typically, these identification procedures are non-unique, resulting in multiple possible scenarios that cannot be distinguished based on the information at hand. To this end standard approaches) use a regularisation term including an apriori model. Here, Bayesian approaches will also be used, in which expert knowledge is used to guide the outcome to reasonable solutions. We will assess the reduction in uncertainty and therefore risks that EM methods can provide when used in combination with seismic surveys for geothermal exploration prior to drilling. It may also be possible to use this technique for monitoring the evolution of geothermal systems. Such techniques may prove to be extremely valuable for the future development of geothermal energy resources.

Loveless, Sian; Harcout-Menou, Virginie; De Ridder, Fjo; Claessens, Bert; Laenen, Ben

2014-05-01

303

Deep magnetic anomaly sources interpreted as Otanmäki type Iron ore reserves  

NASA Astrophysics Data System (ADS)

In Otanmäki ore province of Central Finland vertically integrated magnetization is estimated from two aeromagnetic coverages of different altitudes and by varying overall models of regional field. Petrophysically and geochemically determined magnetization of the mined deposits and correlation between it and ore concentration is used to evaluate iron ore reserves in the deeper part of known ore fields. Further, similar analysis is made to nearby magnetically anomalous areas covered by weakly magnetic metasediments, to estimate potential ore reserves at unexposed formations.

Korhonen, Juha; Kukkonen, Ilmo

2013-04-01

304

Transcranial photoacoustic tomography of the monkey brain  

NASA Astrophysics Data System (ADS)

A photoacoustic tomography (PAT) system using a virtual point ultrasonic transducer was developed for transcranial imaging of monkey brains. The virtual point transducer provided a 10 times greater field-of-view (FOV) than finiteaperture unfocused transducers, which enables large primate imaging. The cerebral cortex of a monkey brain was accurately mapped transcranially, through up to two skulls ranging from 4 to 8 mm in thickness. The mass density and speed of sound distributions of the skull were estimated from adjunct X-ray CT image data and utilized with a timereversal algorithm to mitigate artifacts in the reconstructed image due to acoustic aberration. The oxygenation saturation (sO2) in blood phantoms through a monkey skull was also imaged and quantified, with results consistent with measurements by a gas analyzer. The oxygenation saturation (sO2) in blood phantoms through a monkey skull was also imaged and quantified, with results consistent with measurements by a gas analyzer. Our experimental results demonstrate that PAT can overcome the optical and ultrasound attenuation of a relatively thick skull, and the imaging aberration caused by skull can be corrected to a great extent.

Nie, Liming; Huang, Chao; Guo, Zijian; Anastasio, Mark; Wang, Lihong V.

2012-02-01

305

Electronic and magnetic structures of the postperovskite-type Fe2O3 and implications for planetary magnetic records and deep interiors  

PubMed Central

Recent studies have shown that high pressure (P) induces the metallization of the Fe2+–O bonding, the destruction of magnetic ordering in Fe, and the high-spin (HS) to low-spin (LS) transition of Fe in silicate and oxide phases at the deep planetary interiors. Hematite (Fe2O3) is an important magnetic carrier mineral for deciphering planetary magnetism and a proxy for Fe in the planetary interiors. Here, we present synchrotron Mössbauer spectroscopy and X-ray diffraction combined with ab initio calculations for Fe2O3 revealing the destruction of magnetic ordering at the hematite ? Rh2O3-II type (RhII) transition at 70 GPa and 300 K, and then the revival of magnetic ordering at the RhII ? postperovskite (PPv) transition after laser heating at 73 GPa. At the latter transition, at least half of Fe3+ ions transform from LS to HS and Fe2O3 changes from a semiconductor to a metal. This result demonstrates that some magnetic carrier minerals may experience a complex sequence of magnetic ordering changes during impact rather than a monotonic demagnetization. Also local Fe enrichment at Earth's core-mantle boundary will lead to changes in the electronic structure and spin state of Fe in silicate PPv. If the ultra-low-velocity zones are composed of Fe-enriched silicate PPv and/or the basaltic materials are accumulated at the lowermost mantle, high electrical conductivity of these regions will play an important role for the electromagnetic coupling between the mantle and the core. PMID:19279204

Shim, Sang-Heon; Bengtson, Amelia; Morgan, Dane; Sturhahn, Wolfgang; Catalli, Krystle; Zhao, Jiyong; Lerche, Michael; Prakapenka, Vitali

2009-01-01

306

Deep TMS add-on treatment for intractable Tourette syndrome: A feasibility study.  

PubMed

Objectives. In a considerable minority of patients who suffer from Tourette syndrome (TS) the disorder persists into adulthood and is associated with severe symptoms and limited therapeutic options. Repetitive transcranial magnetic stimulation (rTMS) to the supplementary motor area (SMA) has shown promising therapeutic results. Deep rTMS is a novel technology that enables deeper non-invasive cortical stimulation. This open-label pilot study is the first to examine the possible role of deep rTMS as add-on treatment for intractable TS. Methods. Twelve patients were recruited in order to examine bilateral SMA inhibition via deep TMS using the HBDL coil, as a possible treatment for adult TS treatment-resistant patients. Two patients did not complete the 20-day study protocol. Results. There were no significant side effects. While tics did not improve among the group as a whole, the subgroup of six patients with combined TS and OCD (obsessive compulsive syndrome) showed significant improvement in tic severity (P = 0.037). Conclusions. These findings support the safety of deep rTMS for treating TS. The results also highlight the importance of studying the different TS syndromes separately (e.g., with or without OCD comorbidity) when evaluating deep rTMS protocols for TS patients. PMID:25342253

Bloch, Yuval; Arad, Shira; Levkovitz, Yechiel

2014-10-24

307

Violation of the Guiding Center Approximation for Energetic Ions in the Deep Inner Magnetosphere during Magnetic Storms  

NASA Astrophysics Data System (ADS)

During a magnetic storm, the ring current is developed in the inner magnetosphere. It is believed that the decrease of Dst index during a strom is mainly due to the development of the ring current. Recent numerical simulations have revealed how the ring current grows and decays (Lemon et al., 2004; Zaharia et al., 2006) in the self-consistent field with the guiding center approximation (GCA). This approximation breaks down if the spatial scale of the magnetic field change is comparable to the gyroradius. From the following two reasons, we suspect an approach to treat motion of ring current oxygen ions with the GCA. (1) During magnetic storms a dominant part of energy density of the ring current is carried by oxygen ions (Daglis at al., 1999) which are 16 times heavier than protons; that is, gyroradius of oxygen ions is 4 times larger than that of protons with the same kinetic energy. (2) Magnetic field configuration becomes far deviated from dipole field even in the deep inner magnetosphere. In this study, we examine whether the GCA is valid for ring current ions, in particular for oxygen ions. We compared energetic ion trajectories computed by the Lorentz equation and those by the GCA equation (Northrop, 1963). We used the TS04 (Tsyganenko and Sitnov, 2005) magnetic field model as well as the Volland-Stern (Volland 1973; Stern 1975) electric field model. In case of integration of the Lorentz equation, we found that some of ions have different trajectories from those of the GCA equation. Most remarkable results can be summarized as follows. First, ions having a pitch angle of ~90 degrees do not conserve the first adiabatic invariant and gradually increase their amplitude of bouncing motion around the magnetic equator. Second, an ion with a large gyroradius (i.e, an energetic oxygen ion) can be accelerated thorough the meandering motion even in the deep inner magnetosphere. Above-mentioned results lead some interest phenomena, for example, pitch angle distribution or the development of the ring current. Therefore, we suggest that GCA may not describe the ring current development and decay appropriately.

Shibahara, K.; Nose, M.

2009-12-01

308

An electronically steered, wearable transcranial doppler ultrasound system  

E-print Network

This thesis details the design of a transcranial Doppler (TCD) ultrasound system to measure cerebral blood flow velocity (CBFV) at the middle cerebral artery (MCA). TCD sonography has been clinically indicated in a variety ...

Pietrangelo, Sabino Joseph

2013-01-01

309

Transcranial brain parenchymal sonography in neurodegenerative and psychiatric diseases.  

PubMed

Transcranial sonography is a highly sensitive noninvasive sonographic method for detection of early and specific echogenic changes in basal ganglia of patients with some neurodegenerative diseases. Transcranial sonography showed substantia nigra hyperechogenicity as a typical echo feature in idiopathic Parkinson disease and lenticular nucleus hyperechogenicity as a characteristic finding in atypical parkinsonian syndromes. Brain stem raphe hypoechogenicity or interruption has been shown to be highly prevalent in patients with unipolar depression as well as depression associated with certain neurodegenerative diseases. Transcranial sonography also revealed basal ganglia hyperechoic changes in movement disorders with trace metal accumulation such as Wilson disease, some entities of neurodegeneration with brain iron accumulation, as well as several forms of spinocerebellar ataxia. Transcranial sonography is a valuable neuro imaging method for early and differential diagnosis and follow-up of patients with neurodegenerative and psychiatric diseases. PMID:25425361

Mijajlovic, Milija D; Tsivgoulis, Georgios; Sternic, Nadezda

2014-12-01

310

Transcranial Clot Lysis Using High Intensity Focused Ultrasound  

NASA Astrophysics Data System (ADS)

Stroke is the third common cause of death worldwide. The majority of strokes are caused by sudden vessel occlusion, due to a blood clot. Vessel recanalization is the primary goal of all acute stroke treatment strategies. Initial data using ultrasound in combination with a therapeutic agent for clot lysis in stroke are promising. However, sound absorption and defocusing of the ultrasound beam occur during transskull insonation, limiting the efficiency of this approach to high extent. Using a transskull High Intensity Focused Ultrasound (HIFU) head system we were able to lyse blood clots within seconds and in absence of further lytic agents. We could show that any correction for the distortion might be negligible to focus the ultrasound beam after transskull insonation. The use of transskull HIFU for immediate clot lysis in the human brain without the need of further drugs and disregarding individual skull bone characteristics could become a successful strategy in early stroke treatment. Using magnetic resonance tomography for neuronavigation MRI Guided High Intensity Focused Ultrasound has the potential to open new avenues for therapeutic applications in the brain including Stroke, Intracranial Hemorrhages, Braintumors, Neurodegenerative Diseases, Thalamic Pain, BBB opening, and local drug delivery. First results in transcranial clot lysis will be presented in this paper.

Hölscher, Thilo; Zadicario, Eyal; Fisher, David J.; Bradley, William G.

2010-03-01

311

Serial transcranial Doppler study in meningitis.  

PubMed

Serial transcranial doppler studies were carried out in 12 patients, who developed meningitis during their hospital stay. Blood flow velocities in large basal vessels of the anterior circle of Willis were correlated with CSF pleocytosis and CSF sugar values. Mean blood flow velocities were found to be directly proportional to the CSF white blood cell (WBC) count and were inversely proportional to the CSF sugar values. Blood flow velocities were higher when CSF WBC count was raised. With only one exception these velocities decreased progressively with a fall in the CSF WBC count. At the time of meningitis there occurred a reduction in CSF sugar values and the blood flow velocities were significantly higher. With increase in CSF sugar values there occurred a gradual fall in the blood flow velocities. PMID:8748873

Gupta, R; Mahapatra, A K; Bhatia, R

1995-01-01

312

Hands-Free Transcranial Color Doppler Probe  

NASA Technical Reports Server (NTRS)

Current transcranial color Doppler (TCD) transducer probes are bulky and difficult to move in tiny increments to search and optimize TCD signals. This invention provides miniature motions of a TCD transducer probe to optimize TCD signals. The mechanical probe uses spherical bearing in guiding and locating the tilting crystal face. The lateral motion of the crystal face as it tilts across the full range of motion was achieved by minimizing the distance between the pivot location and the crystal face. The smallest commonly available metal spherical bearing was used with an outer diameter of 12 mm, a 3-mm tall retaining ring, and 5-mm overall height. Small geared motors were used that would provide sufficient power in a very compact package. After confirming the validity of the basic positioning concept, optimization design loops were completed to yield the final design.

Chin, Robert; Madala, Srihdar; Sattler, Graham

2012-01-01

313

Do low field magnetic resonance imaging abnormalities correlate with macroscopical and histological changes within the equine deep digital flexor tendon?  

PubMed

Correlating magnetic resonance (MR) imaging and histopathological findings is essential to validate low field MR imaging in lame horses. This study aimed to compare signal changes in the deep digital flexor tendon (DDFT) of the distal limb on low field MR imaging with macroscopical and histological findings. Cadaver limbs from lame horses with DDFT lesions were selected. The DDFT MR imaging findings and histopathological results were graded, and macroscopical abnormalities were recorded. There was a strong correlation between MR imaging and histopathology grades (rs?=?0.76, p?

Sherlock, C E; Mair, T S; Ireland, J; Blunden, T

2015-02-01

314

Onsite-effects of dual-hemisphere versus conventional single-hemisphere transcranial direct current stimulation  

PubMed Central

We performed functional MRI examinations in six right-handed healthy subjects. During functional MRI scanning, transcranial direct current stimulation was delivered with the anode over the right primary sensorimotor cortex and the cathode over the left primary sensorimotor cortex using dual-hemispheric transcranial direct current stimulation. This was compared to a cathode over the left supraorbital area using conventional single-hemispheric transcranial direct current stimulation. Voxel counts and blood oxygenation level-dependent signal intensities in the right primary sensorimotor cortex regions were estimated and compared between the two transcranial direct current stimulation conditions. Our results showed that dual-hemispheric transcranial direct current stimulation induced greater cortical activities than single-hemispheric transcranial direct current stimulation. These findings suggest that dual-hemispheric transcranial direct current stimulation may provide more effective cortical stimulation than single-hemispheric transcranial direct current stimulation.

Kwon, Yong Hyun; Jang, Sung Ho

2012-01-01

315

Transcranial Brain Stimulation Techniques For Major Depression: Should We Extend TMS Lessons to tDCS?  

PubMed Central

Transcranial magnetic stimulation (TMS) and transcranial direct current stimulation (tDCS) are non-invasive brain stimulation techniques that, by means of magnetic fields and low intensity electrical current, respectively, aim to interefere with and modulate cortical excitability, at the level of dorsolateral prefrontal cortex, in patients with major depression and poor response to standard antidepressants. While the clinical efficacy of TMS in major depression has been extensively investigated over the last 10 years, tDCS has attracted research interest only in the last years, with fewer randomized clinical trials (RCTs) in the field. Nevertheless, in spite of the different rationale and mechanism of action of the two techniques, tDCS recent acquisitions, in relation to the treatment of major depression, seem to parallel those previously obtained with TMS, in terms of treatment duration to achieve optimal benefit and patient's history of drug-resistance. After briefly introducing the two techniques, the article examines possible common pathways of clinical use for TMS and tDCS, emerging from recent RCTs and likely orienting future investigation with non invasive brain stimulation for the treatment of major depression. PMID:25317200

Dell’Osso, Bernardo; Altamura, A. Carlo

2014-01-01

316

Transcranial Direct Current Stimulation of Right Dorsolateral Prefrontal Cortex Does Not Affect Model-Based or Model-Free Reinforcement Learning in Humans  

PubMed Central

There is broad consensus that the prefrontal cortex supports goal-directed, model-based decision-making. Consistent with this, we have recently shown that model-based control can be impaired through transcranial magnetic stimulation of right dorsolateral prefrontal cortex in humans. We hypothesized that an enhancement of model-based control might be achieved by anodal transcranial direct current stimulation of the same region. We tested 22 healthy adult human participants in a within-subject, double-blind design in which participants were given Active or Sham stimulation over two sessions. We show Active stimulation had no effect on model-based control or on model-free (‘habitual’) control compared to Sham stimulation. These null effects are substantiated by a power analysis, which suggests that our study had at least 60% power to detect a true effect, and by a Bayesian model comparison, which favors a model of the data that assumes stimulation had no effect over models that assume stimulation had an effect on behavioral control. Although we cannot entirely exclude more trivial explanations for our null effect, for example related to (faults in) our experimental setup, these data suggest that anodal transcranial direct current stimulation over right dorsolateral prefrontal cortex does not improve model-based control, despite existing evidence that transcranial magnetic stimulation can disrupt such control in the same brain region. PMID:24475185

Smittenaar, Peter; Prichard, George; FitzGerald, Thomas H. B.; Diedrichsen, Joern; Dolan, Raymond J.

2014-01-01

317

CHILES Con Pol: Probing galaxy evolution, the dark Universe, and cosmic magnetism with a deep 1000 hour Jansky VLA survey  

NASA Astrophysics Data System (ADS)

We recently started a 1000 hour campaign to observe 0.2 square degrees of the COSMOS field in full polarization continuum at 1.4 GHz with the Jansky VLA, as part of a joint program with the spectral line COSMOS HI Large Extragalactic Survey (CHILES). When complete, we expect our CHILES Continuum Polarization (CHILES Con Pol) survey to reach an unprecedented SKA-era sensitivity of 0.7 uJy per 4 arcsecond FWHM beam. Here we present the key goals of CHILES Con Pol, which are to (i) produce a source catalog of legacy value to the astronomical community, (ii) measure differential source counts in total intensity, linear polarization, and circular polarization in order to constrain the redshift and luminosity distributions of source populations, (iii) perform a novel weak lensing study using radio polarization as an indicator of intrinsic alignment to better study dark energy and dark matter, and (iv) probe the unknown origin of cosmic magnetism by measuring the strength and structure of intergalactic magnetic fields in the filaments of large scale structure. The CHILES Con Pol source catalog will be a useful resource for upcoming wide-field surveys by acting as a training set for machine learning algorithms, which can then be used to identify and classify radio sources in regions lacking deep multiwavelength coverage.

Hales, Christopher A.; Chiles Con Pol Collaboration

2014-04-01

318

An Intraoperative Brain-shift Monitor Using Shear-mode Transcranial Ultrasound: Preliminary Results  

PubMed Central

Objective Various methods of intraoperative structural monitoring during neurosurgery are used to localize lesions after brain shift and guiding surgically introduced probes such as biopsy needles or stimulation electrodes. With its high temporal resolution, portability, and non-ionizing mode of radiation, ultrasound has potential advantages over other existing imaging modalities for intraoperative monitoring. Yet, sonography is rarely used during neurosurgery largely because of the craniotomy requirement to achieve sufficiently useful signals. Methods Prompted by results from recent studies on transcranial ultrasound, a prototype device that aims to use the shear mode of transcranial ultrasound transmission for intraoperative monitoring has been designed, constructed, and tested with 10 human subjects. Magnetic resonance (MR) images were then obtained with the device spatially registered to the MR reference coordinates. Peaks in both the ultrasound and MR signals were identified and analyzed both for spatial localization and signal-to-noise ratio (SNR). Results The first results aimed towards validating the prototype device with MRI have demonstrated excellent correlation (n = 38, R2 = 0.9962) between the structural localization abilities of the two modalities. In addition, the overall SNR of the ultrasound backscatter signals (n = 38, SNR = 25.4±5.2 dB) was statistically equivalent to that of the MR data (n = 38, SNR = 22.5±4.8 dB). Conclusions A statistically significant correlation of localized intracranial structures between ITUM and MRI data has been achieved with 10 human subjects. This is the first demonstration and validation of a prototype device incorporating transcranial shear-mode ultrasound towards a clinical monitoring application. PMID:19168769

White, P. Jason; Whalen, Stephen; Tang, Sai Chun; Clement, Greg T.; Golby, Alexandra J.

2008-01-01

319

Optical Detection of Magnetic Resonance for a Deep-Level Defect in Silicon  

Microsoft Academic Search

Optical detection of magnetic resonance is reported for the 0.97-eV luminescence in neutron-irradiated silicon. The resonance is of an excited triplet (S=1) state of the defect, which is not the radiative state, known to be a singlet (S=0). The spectrum is unusual in that it is characteristic of a statically distorted defect (from C3v to C1h), but with residual dynamic

K. M. Lee; K. P. O'Donnell; J. Weber; B. C. Cavenett; G. D. Watkins

1982-01-01

320

Computational models of transcranial direct current stimulation.  

PubMed

During transcranial direct current stimulation (tDCS), controllable dose parameters are electrode number (typically 1 anode and 1 cathode), position, size, shape, and applied electric current. Because different electrode montages result in distinct brain current flow patterns across the brain, tDCS dose parameters can be adjusted, in an application-specific manner, to target or avoid specific brain regions. Though the tDCS electrode montage often follows basic rules of thumb (increased/decreased excitability "under" the anode/cathode electrode), computational forward models of brain current flow provide more accurate insight into detailed current flow patterns and, in some cases, can even challenge simplified electrode-placement assumptions. With the increased recognized value of computational forward models in informing tDCS montage design and interpretation of results, there have been recent advances in modeling tools and a greater proliferation of publications.  In addition, the importance of customizing tDCS for potentially vulnerable populations (eg, skull defects, brain damage/stroke, and extremes of age) can be considered. Finally, computational models can be used to design new electrode montages, for example, to improve spatial targeting such as high-definition tDCS. Pending further validation and dissemination of modeling tools, computational forward models of neuromodulation will become standard tools to guide the optimization of clinical trials and electrotherapy. PMID:22956646

Bikson, Marom; Rahman, Asif; Datta, Abhishek

2012-07-01

321

Nanoscale nuclear magnetic resonance with a 1.9-nm-deep nitrogen-vacancy sensor  

SciTech Connect

We present nanoscale nuclear magnetic resonance (NMR) measurements performed with nitrogen-vacancy (NV) centers located down to about 2 nm from the diamond surface. NV centers were created by shallow ion implantation followed by a slow, nanometer-by-nanometer removal of diamond material using oxidative etching in air. The close proximity of NV centers to the surface yielded large {sup 1}H NMR signals of up to 3.4 ?T-rms, corresponding to ?330 statistically polarized or ?10 fully polarized proton spins in a (1.8 nm){sup 3} detection volume.

Loretz, M.; Degen, C. L., E-mail: degenc@ethz.ch [Department of Physics, ETH Zurich, Schafmattstrasse 16, 8093 Zurich (Switzerland); Pezzagna, S.; Meijer, J. [Department of Nuclear Solid State Physics, Institute for Experimental Physics II, Universität Leipzig, Linnéstr. 5, D-04103 Leipzig (Germany)

2014-01-20

322

SPATIAL AND TEMPORAL DISTRIBUTIONS OF TRANSIENT HORIZONTAL MAGNETIC FIELDS WITH DEEP EXPOSURE  

SciTech Connect

We obtained a long-exposure vector magnetogram of the quiet Sun photosphere at the disk center with a wide field of view of 51'' x 82''. The observation was performed at Fe I 525.0 nm with the shutterless mode of the Narrow Band Filter Imager of the Solar Optical Telescope (SOT) on board the Hinode satellite. We summed the linear polarization (LP) maps taken with a time cadence of 60 s for 2 hr to obtain a map with as long of an exposure as possible. The polarization sensitivity would be more than 4.6 (21.2 in exposure time) times the standard observation with the SOT Spectropolarimeter. The LP map shows a cellular structure with a typical scale of 5''-10''. We find that the enhanced LP signals essentially consist of the isolated sporadic transient horizontal magnetic fields (THMFs) with a lifetime of 1-10 minutes and are not contributed by long-duration weak horizontal magnetic fields. The cellular structure coincides in position with the negative divergence of the horizontal flow field, i.e., mesogranular boundaries with downflows. Azimuth distribution appears to be random for the scale size of the mesogranules. Some pixels have two separate appearances of THMFs, and the measured time intervals are consistent with the random appearance. THMFs tend to appear at the mesogranular boundaries, but appear randomly in time. We discuss the origin of THMFs based on these observations.

Ishikawa, Ryohko [Department of Astronomy, University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-0033 (Japan); Tsuneta, Saku, E-mail: ryoko.ishikawa@nao.ac.j [National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka, Tokyo 181-8588 (Japan)

2010-08-01

323

Transcranial alternating current stimulation: a review of the underlying mechanisms and modulation of cognitive processes.  

PubMed

Brain oscillations of different frequencies have been associated with a variety of cognitive functions. Convincing evidence supporting those associations has been provided by studies using intracranial stimulation, pharmacological interventions and lesion studies. The emergence of novel non-invasive brain stimulation techniques like repetitive transcranial magnetic stimulation (rTMS) and transcranial alternating current stimulation (tACS) now allows to modulate brain oscillations directly. Particularly, tACS offers the unique opportunity to causally link brain oscillations of a specific frequency range to cognitive processes, because it uses sinusoidal currents that are bound to one frequency only. Using tACS allows to modulate brain oscillations and in turn to influence cognitive processes, thereby demonstrating the causal link between the two. Here, we review findings about the physiological mechanism of tACS and studies that have used tACS to modulate basic motor and sensory processes as well as higher cognitive processes like memory, ambiguous perception, and decision making. PMID:23785325

Herrmann, Christoph S; Rach, Stefan; Neuling, Toralf; Strüber, Daniel

2013-01-01

324

Combination of transcranial direct current stimulation and methylphenidate in subacute stroke.  

PubMed

Noninvasive transcranial direct current stimulation (tDCS) and methylphenidate (MP) are associated with motor recovery after stroke. Based on the potentially complementary mechanisms of these interventions, we examined whether there is an interactive effect between MP and tDCS. In this preliminary study, we randomized subacute stroke subjects to receive tDCS alone, MP alone or combination of tDCS and MP. A blinded rater measured safety, hand function, and cortical excitability before and after treatment. None of the treatments caused any major or severe adverse effects or induced significant differences in cortical excitability. Analysis of variance of gain score, as measured by Purdue pegboard test, showed a significant between-group difference (F(2,6)=12.167, p=0.008). Post hoc analysis showed that the combination treatment effected greater Purdue pegboard gain scores than tDCS alone (p=0.017) or MP alone (p=0.01). Our preliminary data with nine subjects shows an interesting dissociation between motor function improvement and lack of motor corticospinal plasticity changes as indexed by transcranial magnetic stimulation in subacute stroke subjects. PMID:24631567

Wang, Qing Mei; Cui, Huashun; Han, Soo Jeong; Black-Schaffer, Randie; Volz, Magdalena Sarah; Lee, Yong-Tae; Herman, Seth; Latif, Lydia Abul; Zafonte, Ross; Fregni, Felipe

2014-05-21

325

Effect of transcranial brain stimulation for the treatment of Alzheimer disease: a review.  

PubMed

Available pharmacological treatments for Alzheimer disease (AD) have limited effectiveness, are expensive, and sometimes induce side effects. Therefore, alternative or complementary adjuvant therapeutic strategies have gained increasing attention. The development of novel noninvasive methods of brain stimulation has increased the interest in neuromodulatory techniques as potential therapeutic tool for cognitive rehabilitation in AD. In particular, repetitive transcranial magnetic stimulation (rTMS) and transcranial direct current stimulation (tDCS) are noninvasive approaches that induce prolonged functional changes in the cerebral cortex. Several studies have begun to therapeutically use rTMS or tDCS to improve cognitive performances in patients with AD. However, most of them induced short-duration beneficial effects and were not adequately powered to establish evidence for therapeutic efficacy. Therefore, TMS and tDCS approaches, seeking to enhance cognitive function, have to be considered still very preliminary. In future studies, multiple rTMS or tDCS sessions might also interact, and metaplasticity effects could affect the outcome. PMID:22114748

Nardone, Raffaele; Bergmann, Jürgen; Christova, Monica; Caleri, Francesca; Tezzon, Frediano; Ladurner, Gunther; Trinka, Eugen; Golaszewski, Stefan

2012-01-01

326

Effect of Transcranial Brain Stimulation for the Treatment of Alzheimer Disease: A Review  

PubMed Central

Available pharmacological treatments for Alzheimer disease (AD) have limited effectiveness, are expensive, and sometimes induce side effects. Therefore, alternative or complementary adjuvant therapeutic strategies have gained increasing attention. The development of novel noninvasive methods of brain stimulation has increased the interest in neuromodulatory techniques as potential therapeutic tool for cognitive rehabilitation in AD. In particular, repetitive transcranial magnetic stimulation (rTMS) and transcranial direct current stimulation (tDCS) are noninvasive approaches that induce prolonged functional changes in the cerebral cortex. Several studies have begun to therapeutically use rTMS or tDCS to improve cognitive performances in patients with AD. However, most of them induced short-duration beneficial effects and were not adequately powered to establish evidence for therapeutic efficacy. Therefore, TMS and tDCS approaches, seeking to enhance cognitive function, have to be considered still very preliminary. In future studies, multiple rTMS or tDCS sessions might also interact, and metaplasticity effects could affect the outcome. PMID:22114748

Nardone, Raffaele; Bergmann, Jürgen; Christova, Monica; Caleri, Francesca; Tezzon, Frediano; Ladurner, Gunther; Trinka, Eugen; Golaszewski, Stefan

2012-01-01

327

Anodal transcranial direct current stimulation increases brain intracellular pH and modulates bioenergetics.  

PubMed

Transcranial direct current stimulation is an emerging treatment for brain disorders but its mode of action is not well understood. We applied 10 min 1 mA anodal transcranial direct current stimulation (tDCS) inside the bore of a 3 T MRI scanner to the left dorsolateral prefrontal cortex of 13 healthy volunteers (aged 19-28 yr) in a blinded, sham-controlled, cross-over design. Brain bioenergetics were measured from the left temporo-frontal region using 31P magnetic resonance spectroscopy before, during and for 20 min following tDCS. Brain pH rose during tDCS and remained elevated afterwards. Phosphomonoesters were significantly decreased while inorganic phosphate (Pi) also fell. Partial-least squares discriminant analysis of the data revealed two significantly different subject groups: one where phosphocreatine (PCr), ATP and Pi fell along with a larger increase in pH and one where PCr and ATP increased along with a smaller increase in pH and a slower and more sustained decrease in Pi. Group membership was predicted by baseline pH and ATP. We interpreted the effects of tDCS as driving two biochemical processes: cellular consumption of ATP causing hydrolysis of PCr via the creatine kinase reaction driving the increase in pH; synthesis of ATP and PCr by mitochondria with concomitant drop in Pi and phosphomonoester levels. PMID:23473040

Rae, Caroline D; Lee, Vincent H-C; Ordidge, Roger J; Alonzo, Angelo; Loo, Colleen

2013-09-01

328

Transcranial thermoacoustic tomography: a comparison of two imaging algorithms.  

PubMed

Thermoacoustic tomography (TAT) is a novel, non-invasive medical imaging technique but has encountered obstacles in imaging through the cranium. In this paper we present two methods for transcranial TAT: Kirchhoff migration (KM) and reverse-time migration (RTM). The two methods' imaging qualities are verified and compared based on both synthetic and experimental data. RTM proves to have better velocity variance and imaging quality, and little noise with spatial aliasing. RTM is a promising approach for achieving transcranial TAT in further studies. PMID:23076033

Liu, Zijian; Liu, Lanbo; Xu, Yuan; Wang, Lihong Victory

2013-02-01

329

Target Optimization in Transcranial Direct Current Stimulation  

PubMed Central

Transcranial direct current stimulation (tDCS) is an emerging neuromodulation therapy that has been experimentally determined to affect a wide range of behaviors and diseases ranging from motor, cognitive, and memory processes to depression and pain syndromes. The effects of tDCS may be inhibitory or excitatory, depending on the relative polarities of electrodes and their proximity to different brain structures. This distinction is believed to relate to the interaction of current flow with activation thresholds of different neural complexes. tDCS currents are typically applied via a single pair of large electrodes, with one (the active electrode) sited close to brain structures associated with targeted processes. To efficiently direct current toward the areas presumed related to these effects, we devised a method of steering current toward a selected area by reference to a 19-electrode montage applied to a high-resolution finite element model of the head. We used a non-linear optimization procedure to maximize mean current densities inside the left inferior frontal gyrus (IFG), while simultaneously restricting overall current, and median current densities within the accumbens. We found that a distributed current pattern could be found that would indeed direct current toward the IFG in this way, and compared it to other candidate 2-electrode configurations. Further, we found a combination of four anterior-posterior electrodes could direct current densities to the accumbens. We conclude that a similar method using multiple electrodes may be a useful means of directing current toward or away from specific brain regions and also of reducing tDCS side effects. PMID:23087654

Sadleir, Rosalind J.; Vannorsdall, Tracy D.; Schretlen, David J.; Gordon, Barry

2012-01-01

330

Hands-Free Transcranial Color Doppler Probe  

NASA Technical Reports Server (NTRS)

Current transcranial color Doppler (TCD) transducer probes are bulky and difficult to move in tiny increments to search and optimize TCD signals. This invention provides miniature motions of a TCD transducer probe to optimize TCD signals. The mechanical probe uses a spherical bearing in guiding and locating the tilting crystal face. The lateral motion of the crystal face as it tilts across the full range of motion was achieved by minimizing the distance between the pivot location and the crystal face. The smallest commonly available metal spherical bearing was used with an outer diameter of 12 mm, a 3-mm tall retaining ring, and 5-mm overall height. Small geared motors were used that would provide sufficient power in a very compact package. After confirming the validity of the basic positioning concept, optimization design loops were completed to yield the final design. A parallel motor configuration was used to minimize the amount of space wasted inside the probe case while minimizing the overall case dimensions. The distance from the front edge of the crystal to the edge of the case was also minimized to allow positioning of the probe very close to the ear on the temporal lobe. The mechanical probe is able to achieve a +/-20deg tip and tilt with smooth repeatable action in a very compact package. The enclosed probe is about 7 cm long, 4 cm wide, and 1.8 cm tall. The device is compact, hands-free, and can be adjusted via an innovative touchscreen. Positioning of the probe to the head is performed via conventional transducer gels and pillows. This device is amendable to having advanced software, which could intelligently focus and optimize the TCD signal.

Chin, Robert; Madala, Srihdar; Sattler, Graham

2012-01-01

331

Heating induced near deep brain stimulation lead electrodes during magnetic resonance imaging with a 3 T transceive volume head coil  

NASA Astrophysics Data System (ADS)

Heating induced near deep brain stimulation (DBS) lead electrodes during magnetic resonance imaging with a 3 T transceive head coil was measured, modeled, and imaged in three cadaveric porcine heads (mean body weight = 85.47 ± 3.19 kg, mean head weight = 5.78 ± 0.32 kg). The effect of the placement of the extra-cranial portion of the DBS lead on the heating was investigated by looping the extra-cranial lead on the top, side, and back of the head, and placing it parallel to the coil's longitudinal axial direction. The heating was induced using a 641 s long turbo spin echo sequence with the mean whole head average specific absorption rate of 3.16 W kg-1. Temperatures were measured using fluoroptic probes at the scalp, first and second electrodes from the distal lead tip, and 6 mm distal from electrode 1 (T6 mm). The heating was modeled using the maximum T6 mm and imaged using a proton resonance frequency shift-based MR thermometry method. Results showed that the heating was significantly reduced when the extra-cranial lead was placed in the longitudinal direction compared to the other placements (peak temperature change = 1.5-3.2 °C versus 5.1-24.7 °C). Thermal modeling and MR thermometry may be used together to determine the heating and improve patient safety online.

Shrivastava, Devashish; Abosch, Aviva; Hughes, John; Goerke, Ute; DelaBarre, Lance; Visaria, Rachana; Harel, Noam; Vaughan, J. Thomas

2012-09-01

332

Heating induced near deep brain stimulation lead electrodes during magnetic resonance imaging with a 3 T transceive volume head coil.  

PubMed

Heating induced near deep brain stimulation (DBS) lead electrodes during magnetic resonance imaging with a 3 T transceive head coil was measured, modeled, and imaged in three cadaveric porcine heads (mean body weight = 85.47 ± 3.19 kg, mean head weight = 5.78 ± 0.32 kg). The effect of the placement of the extra-cranial portion of the DBS lead on the heating was investigated by looping the extra-cranial lead on the top, side, and back of the head, and placing it parallel to the coil's longitudinal axial direction. The heating was induced using a 641 s long turbo spin echo sequence with the mean whole head average specific absorption rate of 3.16 W kg(-1). Temperatures were measured using fluoroptic probes at the scalp, first and second electrodes from the distal lead tip, and 6 mm distal from electrode 1 (T(6 mm)). The heating was modeled using the maximum T(6 mm) and imaged using a proton resonance frequency shift-based MR thermometry method. Results showed that the heating was significantly reduced when the extra-cranial lead was placed in the longitudinal direction compared to the other placements (peak temperature change = 1.5-3.2 °C versus 5.1-24.7 °C). Thermal modeling and MR thermometry may be used together to determine the heating and improve patient safety online. PMID:22892760

Shrivastava, Devashish; Abosch, Aviva; Hughes, John; Goerke, Ute; DelaBarre, Lance; Visaria, Rachana; Harel, Noam; Vaughan, J Thomas

2012-09-01

333

Transcranial pulsed Doppler ultrasound findings in brain stem death  

Microsoft Academic Search

Data are presented from transcranial insonation of the middle cerebral artery (MCA) performed at intervals in 23 unconscious children for whom the outcome was subsequently poor. Once an MCA signal had been observed over a 30 minute period with time averaged velocity less than 10 cm s-1 and\\/or a direction of flow index, DFI, defined as 1 minus the ratio

F J Kirkham; S D Levin; T S Padayachee; M C Kyme; B G Neville; R G Gosling

1987-01-01

334

Can Transcranial Ultrasonication Increase Recanalization Flow With Tissue Plasminogen Activator?  

Microsoft Academic Search

Background and Purpose—In thrombolytic therapy for acute ischemic stroke, it is essential to obtain rapid thrombolysis before ischemic neuronal injury occurs. To develop a new technique of thrombolysis for acute ischemic stroke, the effect of transcranially applied ultrasound (TUS) on thrombolysis was examined. Methods—An occlusion model of rabbit femoral artery was produced with thrombin after establishment of stenotic flow and

Toshihiro Ishibashi; Masahiko Akiyama; Hisashi Onoue; Toshiaki Abe; Hiroshi Furuhata

335

Feature Analysis for Parkinson's Disease Detection Based on Transcranial  

E-print Network

Feature Analysis for Parkinson's Disease Detection Based on Transcranial Sonography Image Lei Chen1 validation results show that the local features could be used for PD detection. Keywords: Parkinson's Disease sonography (TCS) was used for the first time in a clinical study between a group of Parkinson's disease (PD

Lübeck, Universität zu

336

RESEARCH Open Access Trans-cranial focused ultrasound without hair  

E-print Network

RESEARCH Open Access Trans-cranial focused ultrasound without hair shaving: feasibility study made of human hair was sonicated using 220- and 710-kHz head transducers to evaluate the feasibility. Results showed that the hair had a negligible effect on focal spot thermal rise at 220 kHz and a 17% drop

Paris-Sud XI, Université de

337

RESEARCH Open Access Facilitating myoelectric-control with transcranial  

E-print Network

treatment at the central nervous system (CNS) level with transcranial direct current stimulation (tDCS: This study on 12 healthy volunteers was conducted to investigate the effects of anodal tDCS of the primary' trials showed a significant main effect of the anodal tDCS target: cerebellar, M1, sham (F(2) = 2.33, p

Paris-Sud XI, Université de

338

Transcranial direct current stimulation: State of the art 2008  

E-print Network

. Beyond this, transcranial direct current stimulation (tDCS) of different cortical areas has been shown and standardize future tDCS studies, we offer this overview of the state of the art for tDCS. Ã? 2008 Elsevier Inc. All rights reserved. Keywords tDCS; brain; human; neuroplasticity Application of electrical currents

Miall, Chris

339

Behavioral/Cognitive Bihemispheric Transcranial Direct Current Stimulation  

E-print Network

these into purposeful sequences. Although transcranial direct current stimulation (tDCS) of the primary motor cortex (M1 facilitate motor synergy learning. Here, we determined the effects of tDCS on the learning of motor synergies patterns. Bihemispheric tDCS was applied to M1 of healthy, right-handed human participants during 4 d

Diedrichsen, Jörn

340

Random calibration for accelerating MR-ARFI guided ultrasonic focusing in transcranial therapy  

NASA Astrophysics Data System (ADS)

Transcranial focused ultrasound is a promising therapeutic modality. It consists of placing transducers around the skull and emitting shaped ultrasound waves that propagate through the skull and then concentrate on one particular location within the brain. However, the skull bone is known to distort the ultrasound beam. In order to compensate for such distortions, a number of techniques have been proposed recently, for instance using Magnetic Resonance Imaging feedback. In order to fully determine the focusing distortion due to the skull, such methods usually require as many calibration signals as transducers, resulting in a lengthy calibration process. In this paper, we investigate how the number of calibration sequences can be significantly reduced, based on random measurements and optimization techniques. Experimental data with six human skulls demonstrate that the number of measurements can be up to three times lower than with the standard methods, while restoring 90% of the focusing efficiency.

Liu, Na; Liutkus, Antoine; Aubry, Jean-François; Marsac, Laurent; Tanter, Mickael; Daudet, Laurent

2015-02-01

341

Random calibration for accelerating MR-ARFI guided ultrasonic focusing in transcranial therapy.  

PubMed

Transcranial focused ultrasound is a promising therapeutic modality. It consists of placing transducers around the skull and emitting shaped ultrasound waves that propagate through the skull and then concentrate on one particular location within the brain. However, the skull bone is known to distort the ultrasound beam. In order to compensate for such distortions, a number of techniques have been proposed recently, for instance using Magnetic Resonance Imaging feedback. In order to fully determine the focusing distortion due to the skull, such methods usually require as many calibration signals as transducers, resulting in a lengthy calibration process. In this paper, we investigate how the number of calibration sequences can be significantly reduced, based on random measurements and optimization techniques. Experimental data with six human skulls demonstrate that the number of measurements can be up to three times lower than with the standard methods, while restoring 90% of the focusing efficiency. PMID:25585885

Liu, Na; Liutkus, Antoine; Aubry, Jean-François; Marsac, Laurent; Tanter, Mickael; Daudet, Laurent

2015-02-01

342

A Review of Transcranial Magnetic Stimulation in Vascular Dementia  

Microsoft Academic Search

Vascular dementia (VaD) is a clinical syndrome that encompasses a wide spectrum of cognitive disorders caused by cerebrovascular disease. The subcortical ischemic form of VaD is clinically homogeneous and a major cause of cognitive impairment in the elderly. Vascular lesions contribute to cognitive decline in neurodegenerative dementias, and VaD and Alzheimer’s disease often coexist and share clinical features and multiple

Giovanni Pennisi; Raffaele Ferri; Mariagiovanna Cantone; Giuseppe Lanza; Manuela Pennisi; Luisa Vinciguerra; Giulia Malaguarnera; Rita Bella

2011-01-01

343

Targeting of White Matter Tracts With Transcranial Magnetic Stimulation  

PubMed Central

Background TMS activations of white matter depend not only on the distance from the coil, but also on the orientation of the axons relative to the TMS-induced electric field, and especially on axonal bends that create strong local field gradient maxima. Therefore, tractography contains potentially useful information for TMS targeting. Objective/methods Here, we utilized 1-mm resolution diffusion and structural T1-weighted MRI to construct large-scale tractography models, and localized TMS white matter activations in motor cortex using electromagnetic forward modeling in a boundary element model (BEM). Results As expected, in sulcal walls, pyramidal cell axonal bends created preferred sites of activation that were not found in gyral crowns. The model agreed with the well-known coil orientation sensitivity of motor cortex, and also suggested unexpected activation distributions emerging from the E-field and tract configurations. We further propose a novel method for computing the optimal coil location and orientation to maximally stimulate a pre-determined axonal bundle. Conclusions Diffusion MRI tractography with electromagnetic modeling may improve spatial specificity and efficacy of TMS. PMID:24220599

Nummenmaa, Aapo; McNab, Jennifer A.; Savadjiev, Peter; Okada, Yoshio; Hämäläinen, Matti S.; Wang, Ruopeng; Wald, Lawrence L.; Pascual-Leone, Alvaro; Wedeen, Van J.; Raij, Tommi

2014-01-01

344

Transcranial Extracellular Impedance Control (tEIC) Modulates Behavioral Performances  

PubMed Central

Electric brain stimulations such as transcranial direct current stimulation (tDCS), transcranial random noise stimulation (tRNS), and transcranial alternating current stimulation (tACS) electrophysiologically modulate brain activity and as a result sometimes modulate behavioral performances. These stimulations can be viewed from an engineering standpoint as involving an artificial electric source (DC, noise, or AC) attached to an impedance branch of a distributed parameter circuit. The distributed parameter circuit is an approximation of the brain and includes electric sources (neurons) and impedances (volume conductors). Such a brain model is linear, as is often the case with the electroencephalogram (EEG) forward model. Thus, the above-mentioned current stimulations change the current distribution in the brain depending on the locations of the electric sources in the brain. Now, if the attached artificial electric source were to be replaced with a resistor, or even a negative resistor, the resistor would also change the current distribution in the brain. In light of the superposition theorem, which holds for any linear electric circuit, attaching an electric source is different from attaching a resistor; the resistor affects each active electric source in the brain so as to increase (or decrease in some cases of a negative resistor) the current flowing out from each source. From an electrophysiological standpoint, the attached resistor can only control the extracellular impedance and never causes forced stimulation; we call this technique transcranial extracellular impedance control (tEIC). We conducted a behavioral experiment to evaluate tEIC and found evidence that it had real-time enhancement and depression effects on EEGs and a real-time facilitation effect on reaction times. Thus, tEIC could be another technique to modulate behavioral performance. PMID:25047913

Matani, Ayumu; Nakayama, Masaaki; Watanabe, Mayumi; Furuyama, Yoshikazu; Hotta, Atsushi; Hoshino, Shotaro

2014-01-01

345

Transcranial optogenetic stimulation for functional mapping of the motor cortex  

Microsoft Academic Search

We developed a method that uses Channelrhodopsin-2 (ChR2) for transcranial optogenetic stimulation. This method is based on scanning a light beam over the brain, thereby photostimulating ChR2-expressing neurons in intact mice. As a proof of principle, we applied this technique to the motor cortex of transgenic mice expressing ChR2 in cortical pyramidal cells. Photostimulation induced limb movements that were time-locked

Riichiro Hira; Naoki Honkura; Jun Noguchi; Yoshio Maruyama; George J. Augustine; Haruo Kasai; Masanori Matsuzaki

2009-01-01

346

Monsoon variability and deep oceanic circulation in the western equatorial Pacific over the last climatic cycle: Insights from sedimentary magnetic properties and sortable silt  

NASA Astrophysics Data System (ADS)

Magnetic and grain size properties of a sediment core located in the western equatorial Pacific, off the southeastern tip of the Philippine island of Mindanao, are presented in an effort to reconstruct past changes in the East Asian Monsoon and deep ocean circulation during the last 160 kyrs. The sedimentary concentration of magnetic particles, interpreted to reflect past changes in runoff from Mindanao, varies almost in antiphase with Northern Hemisphere insolation. This suggests that precipitation was lower in the western equatorial Pacific region during boreal insolation maxima and thus corroborates model results showing opposing trends in precipitation between land and the marine realm there. Variations in the grain size distribution of the inorganic sediment fraction, as recorded by both the sortable silt mean size and the magnetic grain size, provide a monitor of changes in sediment reworking by bottom currents. The close correlation of this proxy of bottom current strength and the benthic ?18O record from the same site implies a tight coupling between deep water flow, most likely Antarctic Intermediate Water (AAIW), and global climate.

Kissel, Catherine; Laj, Carlo; Kienast, Markus; Bolliet, Timothé; Holbourn, Ann; Hill, Paul; Kuhnt, Wolfgang; Braconnot, Pascale

2010-09-01

347

Modulation of resting state functional connectivity of the motor network by transcranial pulsed current stimulation.  

PubMed

The effects of transcranial pulsed current stimulation (tPCS) on resting state functional connectivity (rs-FC) within the motor network were investigated. Eleven healthy participants received one magnetic resonance imaging (MRI) session with three resting state functional MRI (rs-fMRI) scans, one before stimulation (PRE-STIM) to collect baseline measures, one during stimulation (STIM), and one after 13?min of stimulation (POST-STIM). Rs-FC measures during the STIM and POST-STIM conditions were compared to the PRE-STIM baseline. Regions of interest for the rs-FC analysis were extracted from the significantly activated clusters obtained during a finger tapping motor paradigm and included the right primary motor cortex (R M1), left primary motor cortex (L M1), supplemental motor area (SMA), and cerebellum (Cer). The main findings were reduced rs-FC between the left M1 and surrounding motor cortex, and increased rs-FC between the left M1 and left thalamus during stimulation, but increased rs-FC between the Cer and right insula after stimulations. Bivariate measures of connectivity demonstrate reduced strength of connectivity for the whole network average (p=0.044) and reduced diversity of connectivity for the network average during stimulation (p=0.024). During the POST-STIM condition, the trend of reduced diversity for the network average was statistically weaker (p=0.071). In conclusion, while many of the findings are comparable to previous reports using simultaneous transcranial direct current stimulation (tDCS) and fMRI acquisition, we also demonstrate additional changes in connectivity patterns that are induced by tPCS. PMID:24593667

Sours, Chandler; Alon, Gad; Roys, Steve; Gullapalli, Rao P

2014-04-01

348

Transcranial phase aberration correction using beam simulations and MR-ARFI  

SciTech Connect

Purpose: Transcranial magnetic resonance-guided focused ultrasound surgery is a noninvasive technique for causing selective tissue necrosis. Variations in density, thickness, and shape of the skull cause aberrations in the location and shape of the focal zone. In this paper, the authors propose a hybrid simulation-MR-ARFI technique to achieve aberration correction for transcranial MR-guided focused ultrasound surgery. The technique uses ultrasound beam propagation simulations with MR Acoustic Radiation Force Imaging (MR-ARFI) to correct skull-caused phase aberrations. Methods: Skull-based numerical aberrations were obtained from a MR-guided focused ultrasound patient treatment and were added to all elements of the InSightec conformal bone focused ultrasound surgery transducer during transmission. In the first experiment, the 1024 aberrations derived from a human skull were condensed into 16 aberrations by averaging over the transducer area of 64 elements. In the second experiment, all 1024 aberrations were applied to the transducer. The aberrated MR-ARFI images were used in the hybrid simulation-MR-ARFI technique to find 16 estimated aberrations. These estimated aberrations were subtracted from the original aberrations to result in the corrected images. Each aberration experiment (16-aberration and 1024-aberration) was repeated three times. Results: The corrected MR-ARFI image was compared to the aberrated image and the ideal image (image with zero aberrations) for each experiment. The hybrid simulation-MR-ARFI technique resulted in an average increase in focal MR-ARFI phase of 44% for the 16-aberration case and 52% for the 1024-aberration case, and recovered 83% and 39% of the ideal MR-ARFI phase for the 16-aberrations and 1024-aberration case, respectively. Conclusions: Using one MR-ARFI image and noa priori information about the applied phase aberrations, the hybrid simulation-MR-ARFI technique improved the maximum MR-ARFI phase of the beam's focus.

Vyas, Urvi, E-mail: urvi.vyas@gmail.com; Kaye, Elena; Pauly, Kim Butts [Department of Radiology, Stanford University, Stanford, California 94305 (United States)] [Department of Radiology, Stanford University, Stanford, California 94305 (United States)

2014-03-15

349

Smoking Restores Impaired LTD-Like Plasticity in Schizophrenia: a Transcranial Direct Current Stimulation Study.  

PubMed

Impaired neuroplastic responses following noninvasive brain stimulation have been reported repeatedly in schizophrenia patients. These findings have been associated with deficits in GABAergic, glutamatergic, and cholinergic neurotransmission. Although various neurophysiological studies have indicated a relationship between nicotine and neuroplasticity in healthy individuals, the present study is the first investigation into the impact of nicotine on LTD-like plasticity in patients with schizophrenia. Cortical excitability and cortical plasticity were explored in 30 schizophrenia patients (17 smoker, 13 nonsmoker) and 45 healthy controls (13 smoker, 32 nonsmoker) by using single-pulse transcranial magnetic stimulation (TMS) before and following cathodal transcranial direct current stimulation (tDCS) applied to the left primary motor cortex. Our analysis revealed abolished LTD-like plasticity in nonsmoking schizophrenia patients. However, these plasticity deficits were not present in smoking schizophrenia patients. In healthy controls, significant MEP reductions following cathodal tDCS were observed in nonsmoking individuals, but only trend-level reductions in smokers. In smoking schizophrenia patients, the severity of negative symptoms correlated positively with reduced neuroplasticity, whereas nonsmoking patients displayed the opposite effect. Taken together, the data of our study support the notion of an association between chronic smoking and the restitution of impaired LTD-like plasticity in schizophrenia patients. Although replication and further research are needed to better understand this relationship, our findings indicate that nicotine intake might stabilize the impaired inhibition-facilitation balance in the schizophrenic brain through a complex interaction between cortical plasticity, and GABAergic and cholinergic neurotransmission, and might explain the reduced prevalence of negative symptoms in this population. PMID:25308351

Strube, Wolfgang; Bunse, Tilmann; Nitsche, Michael A; Wobrock, Thomas; Aborowa, Richard; Misewitsch, Kristina; Herrmann, Maximiliane; Falkai, Peter; Hasan, Alkomiet

2015-03-01

350

MULTIPLE FEATURE EXTRACTION FOR EARLY PARKINSON RISK ASSESSMENT BASED ON TRANSCRANIAL SONOGRAPHY IMAGE  

E-print Network

MULTIPLE FEATURE EXTRACTION FOR EARLY PARKINSON RISK ASSESSMENT BASED ON TRANSCRANIAL SONOGRAPHY for the diagnosis of Parkinson's disease (PD) at a very early state. The TCS im- age of mesencephalon shows, Parkinson's Disease, Transcranial sonography, classification, texture analysis 1. INTRODUCTION Early

Lübeck, Universität zu

351

EFFECTS OF TRANSCRANIAL DIRECT CURRENT STIMULATION (tDCS) ON SENSORY EVOKED POTENTIALS: A COMPUTATIONAL MODELING  

E-print Network

EFFECTS OF TRANSCRANIAL DIRECT CURRENT STIMULATION (tDCS) ON SENSORY EVOKED POTENTIALS/computational modeling approach aimed at studying the effects of transcranial Direct Current Stimulation (tDCS (EPs) recorded from the somatosensory cortex of the rabbit under tDCS. Results showed that the model

Paris-Sud XI, Université de

352

Transcranial direct current stimulation over posterior parietal cortex modulates visuospatial localization  

E-print Network

, our goal was to determine whether modulation of the PPC via transcranial direct current stimulation (tDCS the left PPC (dual tDCS) and varied the polarity of the stimulation. We found that this manipulation localization. We used transcranial direct current stimulation (tDCS) over the PPC of healthy human volunteers

Krekelberg, Bart

353

Development of a Neurostimulation Method Using Pulsed Ultrasound.  

E-print Network

??Neurostimulation methods currently include deep brain stimulation (DBS), optogenetic, transcranial direct-current stimulation (tDCS), and transcranial magnetic stimulation (TMS). TMS and tDCS are noninvasive techniques whereas… (more)

Tufail, Yusuf

2011-01-01

354

Immuno-magnetic beads-based extraction-capillary zone electrophoresis-deep UV laser-induced fluorescence analysis of erythropoietin.  

PubMed

Erythropoietin (EPO) is an important glycoprotein hormone. Recombinant human EPO (rhEPO) is an important therapeutic drug and can be also used as doping reagent in sports. The analysis of EPO glycoforms in pharmaceutical and sports areas greatly challenges analytical scientists from several aspects, among which sensitive detection and effective and facile sample preparation are two essential issues. Herein, we investigated new possibilities for these two aspects. Deep UV laser-induced fluorescence detection (deep UV-LIF) was established to detect the intrinsic fluorescence of EPO while an immuno-magnetic beads-based extraction (IMBE) was developed to specifically extract EPO glycoforms. Combined with capillary zone electrophoresis (CZE), CZE-deep UV-LIF allows high resolution glycoform profiling with improved sensitivity. The detection sensitivity was improved by one order of magnitude as compared with UV absorbance detection. An additional advantage is that the original glycoform distribution can be completely preserved because no fluorescent labeling is needed. By combining IMBE with CZE-deep UV-LIF, the overall detection sensitivity was 1.5 × 10?? mol/L, which was enhanced by two orders of magnitude relative to conventional CZE with UV absorbance detection. It is applicable to the analysis of pharmaceutical preparations of EPO, but the sensitivity is insufficient for the anti-doping analysis of EPO in blood and urine. IMBE can be straightforward and effective approach for sample preparation. However, antibodies with high specificity were the key for application to urine samples because some urinary proteins can severely interfere the immuno-extraction. PMID:22381892

Wang, Heye; Dou, Peng; Lü, Chenchen; Liu, Zhen

2012-07-13

355

Relaxation oscillations of Zeeman and dipole magnetizations of a paramagnet under conditions of deep low-frequency modulation  

E-print Network

The relaxation oscillations of Zeeman and dipole magnetizaions in spin system of a solid paramagnet are theoretically analyzed under conditions of intermediate saturation of magnetic resonance and strong low-frequency modulation of the external magnetic field. Peculiarities of the relaxation oscillations in the synchronous detection regime are considered.

M. D. Zviadadze; A. G. Kvirikadze; R. L. Lepsveridze; G. I. Mamniashvili; N. M. Sozashvili

2006-10-08

356

Tests for orbital influences on the geomagnetic field, and Quarternary magnetic records from North Atlantic and Arctic deep-sea sediments  

NASA Astrophysics Data System (ADS)

This dissertation investigated the possible connection between orbital variations and the Earth's magnetic field, and the origin of orbital periods in sedimentary relative paleointensity (RPI) records, using previously published data. Circular statistic methods were utilized to test whether there is any consistent relationship between the phase of orbital parameters and the timing of geomagnetic reversals or excursions. The results indicate no discernable tendency, disagreeing with orbital forcing on the geodynamo. Numerical simulations further indicate that precision of the current polarity timescales need to be improved for any firm relationship to be established. Wavelet analyses methods were employed to investigate the origin of orbital periods in the RPI records. In some records, significant coherence at orbital periods occurs between RPI and a particular magnetic grain-size proxy. Therefore, orbital periods in some RPI records are attributed to lithologic 'contamination' resulted from incomplete normalization of the natural remanent magnetization (NRM) record. Comparison of RPI records from different regions of the world in both the time and time-frequency domains imply that the 'contamination' does not debilitate most RPI records as a global signal that is primarily of geomagnetic origin. Calibrated RPI and oxygen isotope stack records (PISO-1500) were developed by simultaneously matching and stacking both RPI and oxygen isotope data for 13 pairs of high-resolution global records. Wavelet analyses on the PISO-1500 RPI stack record failed to show significant orbital periods, and no tendencies were found for RPI minima in the stack to occur at particular phases of orbital variations. The generation of high-resolution paleomagnetic data is often associated with processing large volumes of measurement data. MATLAB(TM) software with graphical user interfaces was developed in this dissertation work to improve the efficiency of processing large volumes of paleomagnetic data and facilitates the calculation of paleomagnetic directions and RPI proxies. This new software incorporates new methods of analysis, particularly in the generation of RPI proxies. U-channel NRM measurements at Integrated Ocean Drilling Program (IODP) Site U1304 yield continuous high resolution paleomagnetic records for the last ˜1.5 Ma. Sediments from IODP Site U1304 clearly recorded the Brunhes/Matuyama boundary, the Jaramillo subchron, and the Cobb Mountain subchron, as well as the Kamikatsura excursion and the Gardar excursion. Age model for the site is established by correlating IODP Site U1304 RPI record to the PISO-1500 RPI stack using automated dynamic programming method with limited number of tie points. No significant orbital periods were detected in RPI record from the site. Various evidences indicate that the episodic deposits of laminated diatom ooze throughout the IODP Site U1304 sediments, appear to dilute the magnetic concentrations of the sediments with elevated sedimentation rates, but do not debilitate the reliability of the acquired paleomagnetic direction and intensity data. Rock magnetic experiments carried out under various temperature ranges, along with scanning electron microscopy (SEM) and X-ray energy-dispersive spectroscopy (EDS) observations as well as X-ray diffraction (XRD) analyses, on bulk Arctic deep-sea sediments and magnetic extracts from seven cores collected by the Healy-Oden Trans-Arctic Expedition 2005 (HOTRAX05), indicate that (titano)magnetite and titanomaghemite are the magnetic remanence carriers. It appears that the titanomaghemite carries a chemical remanent magnetization (CRM) that is partially self-reversed relative to the detrital remanent magnetization (DRM) carried by the host titanomagnetite, causing the apparent magnetic 'excursions' in the Arctic deep-sea sediment records. The partial self-reversal could have been accomplished by ionic ordering during oxidation, thereby changing the balance of the magnetic moments in the ferrimagnetic sublattices that characterize titanomagnetite and titanomaghemit

Xuan, Chuang

357

Brain Circulation during Panic Attack: A Transcranial Doppler Study with Clomipramine Challenge  

PubMed Central

Introduction. Cerebral blood flow has been well studied in patients with panic disorder, but only few studies analyzed the mechanisms underlying the onset of a panic attack. The aim of the present study was to monitor the cerebral hemodynamics modifications during a panic attack. Materials and Methods. 10 panic disorder patients with recent onset, fully drug naïve, were compared to 13 patients with panic disorder with a previous history of treatment and to 14 controls. A continuous bilateral monitoring of mean flow velocities in right and left middle cerebral arteries was performed by transcranial Doppler. Clomipramine was chosen as challenge. Results. Eight out of 10 patients drug naïve and 6 control subjects out of 13 had a full blown panic attack during the test, whereas none of the patients with a history of treatment panicked. The occurrence of a panic attack was accompanied by a rapid decrease of flow velocities in both right and left middle cerebral arteries. Discussion. The bilateral acute decrease of mean flow velocity during a panic attack suggests the vasoconstriction of the microcirculation of deep brain structures perfused by middle cerebral arteries and involved in the so-called “fear circuitry,” thus suggesting that cerebral homeostatic dysfunctions seem to have a key role in the onset of a panic attack. PMID:24829899

Marinoni, Marinella; Lejeune, Francesca; Alari, Fabiana; Depinesi, Daniela; Faravelli, Carlo

2014-01-01

358

Transcranial Direct Current Stimulation for Treating Depression in a Patient With Right Hemispheric Dominance: A Case Study.  

PubMed

We report the case of a 66-year-old male patient with major depressive disorder for the last 6 months. The patient had been diagnosed with dyslexia during childhood and was left-handed. The intervention protocol consisted in 10 consecutive daily transcranial direct current stimulation sessions. However, after 5 days of stimulation, the patient presented with intensification of depressive symptoms and panic attacks. It was hypothetized that the intensification of symptoms may have been due to stimulation protocol itself. Considering the patient was left-handed and presented comorbidity with dyslexia, there was a plausible hypothesis of right hemispheric dominance. This was corroborated by the Edinburgh Handedness Scale. In fact, dyslexic patients present right hemisphere dominance more frequently. The patient also presented a single photon emission computed tomography with a hypoperfusion area over the left posterior parietal lobe. After the patients agreement, a 10-day experimental repetitive transcranial magnetic stimulation low-frequency protocol over the left dorsolateral prefrontal cortex was started to inhibit the area, which was hypothetically hyperactivated following the rationale of right dominance. The patient presented amelioration of depressive and anxious symptoms. Given the hemispheric reversal we show in the present case study, however, it seems that therapies that are beneficial to right-handers could be detrimental to left-handers. PMID:25203287

Shiozawa, Pedro; da Silva, Mailu Enokibara; Cordeiro, Quirino

2014-09-01

359

Transcranial Doppler validation of hemodynamic vertebrobasilar insufficiency diagnosis.  

PubMed

Transcranial Doppler (TCD) can be useful in the diagnosis and validation of surgical treatment of vertebrobasilar insufficiency (VBI). A case is reported in which TCD confirmed the diagnosis of vertebrobasilar insufficiency and validated the indication of surgery by detecting a bidirectional flow in a stenotic and compressed vertebral artery. In the postoperative period and at late follow-up TCD demonstrated a restored antegrade flow, as a consequence of a well functioning revascularization. Surgical indication of VBI is rare and TCD can be proposed as part of routine patients' study before a surgical decision is taken. PMID:9177624

Illuminati, G; Caliò, F G; Bertagni, A; Vietri, F; Martinelli, V

1996-01-01

360

Transcranial color coded duplex sonography in the intensive care unit  

Microsoft Academic Search

Case report  A case of a 43-year-old male with severe pancreatitis complicated with neurological deterioration is presented.\\u000a \\u000a \\u000a \\u000a Methods and result  Different neurosonological examinations using transcranial color coded duplex sonography (TCCS) were combined to obtain a\\u000a certain diagnosis.\\u000a \\u000a \\u000a \\u000a \\u000a Conclusion  This case illustrates some of the applications of TCCS at bedside in ICU patients. These sonographic explorations are useful\\u000a in the monitoring of ICU patients,

Juan Antonio Llompart-Pou; Josep María Abadal; Miguel Rodríguez-Yago; Mireia Ferreruela

2011-01-01

361

Magnetic structure of an ocean core complex at the southernmost part of the Central Indian Ridge, analysis of shipboard and deep sea three component magnetometers  

NASA Astrophysics Data System (ADS)

We investigated the magnetic structure of an ocean core complex in the southernmost Central Indian Ridge (full spreading rate: 50mm/yr) near 25°S (25°S OCC). The 25°S OCC is located 22km western off-axis of the CIR segment2 and extends approximately 20km along the flow line and 10km across the flow line. It is a doomed topographic high with well-developed, flow line parallel corrugations on its top. We carried out geophysical survey over the 25°S OCC, during YK05-16 cruise of R/V Yokosuka in January 2006. Two types of geophysical measurements were conducted; 1) standard surface geophysical mapping which includes multibeam bathymetry mapping, surface-tow magnetometer, shipboard three-component magnetometer(STCM) and shipboard gravimeter, and 2) high-resolution vector magnetic measurement using deep sea three-component magnetometer(DSTCM) attached to the manned submersible Shinkai 6500 . Total three submersible dives were done over the surface of 25°S OCC and continuous magnetic profile along a corrugation was collected with video records and rock samples. The DSTCM allows us to address 1) short wavelength magnetic characteristics of the oceanic crust, and 2) information of magnetic boundaries in terms of positions, strikes and magnetization contrasts. These data lead to better understanding structure and geochemical composition of OCC. We show preliminary results of processed magnetic anomalies. Total magnetic anomalies obtained from proton magnetometer and STCM data show large positive amplitude near the top of the 25°S OCC, although the OCC is supposed to be formed at south east part of CIR segment2 during reverse polarity chron. The positive anomaly associated with the OCC may indicate the induced magnetization due to the serpentinization of olivine in the lower crust or upper mantle exhumed along the detachment fault. Magnetic boundary strike vectors derived from STCM data are perpendicular to the spreading axis near the top of the 25°S OCC, whereas the strike vectors out of the 25°S OCC are parallel to the ambient geomagnetic field. The flow line parallel magnetic boundary on the OCC may be partly due to the topographic effect of corrugations, but it can imply the magnetic characteristics of the detachment surface. Total of 6.5km of DSTCM profile was obtained during two submersible dives along the most prominent corrugation and this track covers 30% of the total length of the OCC. Measurement were done about 1~10°Eabove sea floor. Total magnetic anomaly profile shows positive anomalies along the eastern 1.8km of the profile, where the largest anomaly reaches 800nT. Negative anomalies were observed in 0.3km along the middle part of the corrugation and the peak value is -600nT. These anomalies do not show clear correlation with topography, so the detailed investigation on the relationship with collected rock sample are needed.

Sato, T.; Okino, K.; Kumagai, H.

2006-12-01

362

Ultrasound measurement of transcranial distance during head-down tilt  

NASA Technical Reports Server (NTRS)

Exposure to microgravity elevates blood pressure and flow in the head, which may increase intracranial volume (ICV) and intracranial pressure (ICP). Rhesus monkeys exposed to simulated microgravity in the form of 6 degree head-down tilt (HDT) experience elevated ICP. With humans, twenty-four hours of 6 degree HDT bed rest increases cerebral blood flow velocity relative to pre-HDT upright posture. Humans exposed to acute 6 degree HDT experiments increased ICP, measured with the tympanic membrane displacement (TMD) technique. Other studies suggest that increased ICP in humans and cats causes measurable cranial bone movement across the sagittal suture. Due to the slightly compliant nature of the cranium, elevation of the ICP will increase ICV and transcranial distance. Currently, several non-invasive approaches to monitor ICP are being investigated. Such techniques include TMD and modal analysis of the skull. TMD may not be reliable over a large range of ICP and neither method is capable of measuring the small changes in pressure. Ultrasound, however, may reliably measure small distance changes that accompany ICP fluctuations. The purpose of our study was to develop and evaluate an ultrasound technique to measure transcranial distance changes during HDT.

Torikoshi, S.; Wilson, M. H.; Ballard, R. E.; Watenpaugh, D. E.; Murthy, G.; Yost, W. T.; Cantrell, J. H.; Chang, D. S.; Hargens, A. R.

1995-01-01

363

Electroencephalography and transcranial Doppler ultrasonography in neonatal citrullinemia.  

PubMed

The authors present a case of citrullinemia with a genotype of argininosuccinate synthetase (ASS1), c.380 G>A (p.R127Q)/c.380 G>A (p.R127Q), in two alleles. A 3-day-old female infant presented with status epilepticus and coma. Laboratory data showed hyperammonemia and marked lactic acidosis in the blood and cerebrospinal fluid; electroencephalography showed severely suppressed cerebral activity and focal paroxysmal volleys of slow and sharp waves (< 1Hz) over the left hemisphere. Real-time transcranial Doppler ultrasonography showed a brain edema and high peaked systolic and low diastolic flows in basal, anterior, and middle cerebral arteries; however, immediately after a blood exchange transfusion, systolic flows were lower and diastolic flows were higher. The resistance indices were significantly different (means: 0.58 vs. 0.37; p=0.01). The patient was placed on diet therapy. After six blood exchange transfusions and peritoneal dialysis, her neurologic examination results and serum ammonia and lactate values were normal. The authors found that electroencephalography and transcranial Doppler ultrasonography were useful for the diagnosis and follow-up treatment of neonatal citrullinemia. PMID:25443352

Su, Pen-Hua; Chen, Jia-Yuh; Chen, Yung-Jung; Niu, Dau-Ming; Hsu, Ju-Hui; Lee, Inn-Chi

2014-11-01

364

A computerized tomography system for transcranial ultrasound imaging  

PubMed Central

Hardware for tomographic imaging presents both challenge and opportunity for simplification when compared with traditional pulse-echo imaging systems. Specifically, point diffraction tomography does not require simultaneous powering of elements, in theory allowing just a single transmit channel and a single receive channel to be coupled with a switching or multiplexing network. In our ongoing work on transcranial imaging, we have developed a 512-channel system designed to transmit and/or receive a high voltage signal from/to arbitrary elements of an imaging array. The overall design follows a hierarchy of modules including a software interface, microcontroller, pulse generator, pulse amplifier, high-voltage power converter, switching mother board, switching daughter board, receiver amplifier, analog-to-digital converter, peak detector, memory, and USB communication. Two pulse amplifiers are included, each capable of producing up to 400Vpp via power MOSFETS. Switching is based around mechanical relays that allow passage of 200V, while still achieving switching times of under 2ms, with an operating frequency ranging from below 100kHz to 10MHz. The system is demonstrated through ex vivo human skulls using 1MHz transducers. The overall system design is applicable to planned human studies in transcranial image acquisition, and may have additional tomographic applications for other materials necessitating a high signal output. PMID:25598864

Tang, Sai Chun; Clement, Gregory T

2014-01-01

365

DEEP X-RAY OBSERVATIONS OF THE YOUNG HIGH-MAGNETIC-FIELD RADIO PULSAR J1119-6127 AND SUPERNOVA REMNANT G292.2-0.5  

SciTech Connect

High-magnetic-field radio pulsars are important transition objects for understanding the connection between magnetars and conventional radio pulsars. We present a detailed study of the young radio pulsar J1119-6127, which has a characteristic age of 1900 yr and a spin-down-inferred magnetic field of 4.1 Multiplication-Sign 10{sup 13} G, and its associated supernova remnant G292.2-0.5, using deep XMM-Newton and Chandra X-ray Observatory exposures of over 120 ks from each telescope. The pulsar emission shows strong modulation below 2.5 keV with a single-peaked profile and a large pulsed fraction of 0.48 {+-} 0.12. Employing a magnetic, partially ionized hydrogen atmosphere model, we find that the observed pulse profile can be produced by a single hot spot of temperature 0.13 keV covering about one-third of the stellar surface, and we place an upper limit of 0.08 keV for an antipodal hot spot with the same area. The non-uniform surface temperature distribution could be the result of anisotropic heat conduction under a strong magnetic field, and a single-peaked profile seems common among high-B radio pulsars. For the associated remnant G292.2-0.5, its large diameter could be attributed to fast expansion in a low-density wind cavity, likely formed by a Wolf-Rayet progenitor, similar to two other high-B radio pulsars.

Ng, C.-Y.; Kaspi, V. M. [Department of Physics, McGill University, Montreal, QC H3A 2T8 (Canada); Ho, W. C. G. [School of Mathematics, University of Southampton, Southampton SO17 1BJ (United Kingdom); Weltevrede, P. [Jodrell Bank Centre for Astrophysics, University of Manchester, Alan Turing Building, Manchester M13 9PL (United Kingdom); Bogdanov, S. [Columbia Astrophysics Laboratory, Columbia University, 550 West 120th Street, New York, NY 10027 (United States); Shannon, R. [CSIRO Astronomy and Space Sciences, Australia Telescope National Facility, Marsfield, NSW 2210 (Australia); Gonzalez, M. E., E-mail: ncy@physics.mcgill.ca [Department of Physics and Astronomy, University of British Columbia, Vancouver, BC V6T 1Z1 (Canada)

2012-12-10

366

Magnetic fields in noninvasive brain stimulation.  

PubMed

The idea that magnetic fields could be used therapeutically arose 2000 years ago. These therapeutic possibilities were expanded after the discovery of electromagnetic induction by the Englishman Michael Faraday and the American Joseph Henry. In 1896, Arsène d'Arsonval reported his experience with noninvasive brain magnetic stimulation to the scientific French community. In the second half of the 20th century, changing magnetic fields emerged as a noninvasive tool to study the nervous system and to modulate neural function. In 1985, Barker, Jalinous, and Freeston presented transcranial magnetic stimulation, a relatively focal and painless technique. Transcranial magnetic stimulation has been proposed as a clinical neurophysiology tool and as a potential adjuvant treatment for psychiatric and neurologic conditions. This article aims to contextualize the progress of use of magnetic fields in the history of neuroscience and medical sciences, until 1985. PMID:23787954

Vidal-Dourado, Marcos; Conforto, Adriana Bastos; Caboclo, Luis Otávio Sales Ferreira; Scaff, Milberto; Guilhoto, Laura Maria de Figueiredo Ferreira; Yacubian, Elza Márcia Targas

2014-04-01

367

Transcranial LED therapy for cognitive dysfunction in chronic, mild traumatic brain injury: Two case reports  

E-print Network

Two chronic, traumatic brain injury (TBI) cases are presented, where cognitive function improved following treatment with transcranial light emitting diodes (LEDs). At age 59, P1 had closed-head injury from a motor vehicle ...

Hamblin, Michael R.

368

[Transcranial electrostimulation: a new approach (experimental and clinical bases and equipment)].  

PubMed

The paper deals with one type of electrostimulation-transcranial electrostimulation (TES). It outlines the physiological mechanisms underlying TES, the clinical features of its application, the equipment performing TES, defines its optimum analgesic mode. PMID:9213744

Lebedev, V P

1997-01-01

369

Polarity Specific Effects of Transcranial Direct Current Stimulation on Interhemispheric Inhibition  

PubMed Central

Transcranial direct current stimulation (tDCS) has been used as a useful interventional brain stimulation technique to improve unilateral upper-limb motor function in healthy humans, as well as in stroke patients. Although tDCS applications are supposed to modify the interhemispheric balance between the motor cortices, the tDCS after-effects on interhemispheric interactions are still poorly understood. To address this issue, we investigated the tDCS after-effects on interhemispheric inhibition (IHI) between the primary motor cortices (M1) in healthy humans. Three types of tDCS electrode montage were tested on separate days; anodal tDCS over the right M1, cathodal tDCS over the left M1, bilateral tDCS with anode over the right M1 and cathode over the left M1. Single-pulse and paired-pulse transcranial magnetic stimulations were given to the left M1 and right M1 before and after tDCS to assess the bilateral corticospinal excitabilities and mutual direction of IHI. Regardless of the electrode montages, corticospinal excitability was increased on the same side of anodal stimulation and decreased on the same side of cathodal stimulation. However, neither unilateral tDCS changed the corticospinal excitability at the unstimulated side. Unilateral anodal tDCS increased IHI from the facilitated side M1 to the unchanged side M1, but it did not change IHI in the other direction. Unilateral cathodal tDCS suppressed IHI both from the inhibited side M1 to the unchanged side M1 and from the unchanged side M1 to the inhibited side M1. Bilateral tDCS increased IHI from the facilitated side M1 to the inhibited side M1 and attenuated IHI in the opposite direction. Sham-tDCS affected neither corticospinal excitability nor IHI. These findings indicate that tDCS produced polarity-specific after-effects on the interhemispheric interactions between M1 and that those after-effects on interhemispheric interactions were mainly dependent on whether tDCS resulted in the facilitation or inhibition of the M1 sending interhemispheric volleys. PMID:25478912

Tazoe, Toshiki; Endoh, Takashi; Kitamura, Taku; Ogata, Toru

2014-01-01

370

Transcranial Doppler-guided deairing of a pediatric ventricular assist device: experience with twins.  

PubMed

We report the intraoperative courses of 2 consecutive Berlin Heart Excor® Pediatric Ventricular Assist Device implantations, in which transcranial Doppler ultrasonography helped to detect macroscopically undetected residual air bubbles captured in the pump after air removal had been correctly performed according to manufacturer's specifications. Our experience with these cases suggests that a beat-to beat deairing maneuver guided by transcranial Doppler is a useful strategy for reducing cerebral exposure to perioperative gaseous microembolism. PMID:25612271

Erdoes, Gabor; Kadner, Alexander; Hutter, Damian; Eberle, Balthasar

2015-01-01

371

Applications of transcranial direct current stimulation for understanding brain function.  

PubMed

In recent years there has been an exponential rise in the number of studies employing transcranial direct current stimulation (tDCS) as a means of gaining a systems-level understanding of the cortical substrates underlying behaviour. These advances have allowed inferences to be made regarding the neural operations that shape perception, cognition, and action. Here we summarise how tDCS works, and show how research using this technique is expanding our understanding of the neural basis of cognitive and motor training. We also explain how oscillatory tDCS can elucidate the role of fluctuations in neural activity, in both frequency and phase, in perception, learning, and memory. Finally, we highlight some key methodological issues for tDCS and suggest how these can be addressed. PMID:25189102

Filmer, Hannah L; Dux, Paul E; Mattingley, Jason B

2014-12-01

372

Cortical Control of Affective Networks  

E-print Network

Transcranial magnetic stimulation and deep brain stimulation have emerged as therapeutic modalities for treatment refractory depression; however, little remains known regarding the circuitry that mediates the therapeutic ...

Kumar, S.

373

Gender Differences in Current Received during Transcranial Electrical Stimulation  

PubMed Central

Low current transcranial electrical stimulation (tCS) is an effective but somewhat inconsistent tool for augmenting neuromodulation. In this study, we used 3D MRI guided electrical transcranial stimulation modeling to estimate the range of current intensities received at cortical brain tissues. Combined T1, T2, and proton density MRIs from 24 adult subjects (12 male and 12 female) were modeled with virtual electrodes placed at F3, F4, C3, and C4. Two sizes of electrodes 20?mm round and 50?mm?×?45?mm were examined at 0.5, 1, and 2?mA input currents. The intensity of current received was sampled in a 1-cm sphere placed at the cortex directly under each scalp electrode. There was a 10-fold difference in the amount of current received by individuals. A large gender difference was observed with female subjects receiving significantly less current at targeted parietal cortex than male subjects when stimulated at identical current levels (P?

Russell, Michael; Goodman, Theodore; Wang, Qiang; Groshong, Bennett; Lyeth, Bruce G.

2014-01-01

374

Direct transcranial puncture for Onyx embolization of a cerebellar hemangioblastoma.  

PubMed

Intracranial hemangioblastomas are benign but hypervascular tumors, most commonly located in the cerebellum, which are difficult to resect without significant operative blood loss. While preoperative embolization may decrease the amount of operative bleeding, the vascular supply of cerebellar hemangioblastomas frequently precludes safe embolization by an endovascular route due to the risk of thromboembolic vertebrobasilar infarction. Direct puncture embolization overcomes many of the limitations of endovascular embolization but its safety and feasibility for intracranial tumors is unknown. We report a 48-year-old man who was diagnosed with a large cerebellar mass after presenting with headaches and gait ataxia. Based on diagnostic angiography, which demonstrated a highly vascular tumor supplied by the posterior inferior cerebellar and posterior meningeal arteries, we decided to embolize the tumor by a direct transcranial puncture approach. After trephinating the skull in a standard fashion, a catheter-needle construct, composed of an Echelon 10 microcatheter (ev3 Endovascular, Plymouth, MN, USA) placed into a 21-gauge spinal needle, was inserted into the tumor under biplanar angiographic guidance. Using continuous angiographic monitoring, 9cc of Onyx 34 (ev3 Endovascular) was injected through the catheter, resulting in 75% tumor devascularization without evidence of complications. The patient was taken directly to surgery where a gross total resection of the hemangioblastoma was achieved with an acceptable operative blood loss. At his 2 year follow-up, the patient was neurologically intact without neuroimaging evidence of residual tumor. We describe, to our knowledge, the first case of direct transcranial puncture for preoperative embolization of a cerebellar hemangioblastoma. PMID:24370504

Ding, Dale; Starke, Robert M; Evans, Avery J; Liu, Kenneth C

2014-06-01

375

Prehospital stroke diagnostics based on neurological examination and transcranial ultrasound  

PubMed Central

Background Transcranial color-coded sonography (TCCS) has proved to be a fast and reliable tool for the detection of middle cerebral artery (MCA) occlusions in a hospital setting. In this feasibility study on prehospital sonography, our aim was to investigate the accuracy of TCCS for neurovascular emergency diagnostics when performed in a prehospital setting using mobile ultrasound equipment as part of a neurological examination. Methods Following a ‘911 stroke code’ call, stroke neurologists experienced in TCCS rendezvoused with the paramedic team. In patients with suspected stroke, TCCS examination including ultrasound contrast agents was performed. Results were compared with neurovascular imaging (CTA, MRA) and the final discharge diagnosis from standard patient-centered stroke care. Results We enrolled ‘232 stroke code’ patients with follow-up data available in 102 patients with complete TCCS examination. A diagnosis of ischemic stroke was made in 73 cases; 29 patients were identified as ‘stroke mimics’. MCA occlusion was diagnosed in ten patients, while internal carotid artery (ICA) occlusion/high-grade stenosis leading to reversal of anterior cerebral artery flow was diagnosed in four patients. The initial working diagnosis ‘any stroke’ showed a sensitivity of 94% and a specificity of 48%. ‘Major MCA or ICA stroke’ diagnosed by mobile ultrasound showed an overall sensitivity of 78% and specificity of 98%. Conclusions The study demonstrates the feasibility and high diagnostic accuracy of emergency transcranial ultrasound assessment combined with neurological examinations for major ischemic stroke. Future combination with telemedical support, point-of-care analysis of blood serum markers, and probability algorithms of prehospital stroke diagnosis including ultrasound may help to speed up stroke treatment. PMID:24572006

2014-01-01

376

Heating Induced near Deep Brain Stimulation Lead Electrodes during Magnetic Resonance Imaging with a 3T Transceive Volume Head Coil  

PubMed Central

Heating induced near deep brain stimulation (DBS) lead electrodes during MRI with a 3T transceive head coil was measured, modeled, and imaged in three cadaveric porcine heads (mean body weight = 85.47±3.19 kg, mean head weight = 5.78±0.32 kg). The effect of the placement of the extra-cranial portion of the DBS lead on the heating was investigated by looping the extra-cranial lead on the top, side, and back of the head; and placing it parallel to the coil’s longitudinal axial direction. The heating was induced using a 641 s long turbo spin echo sequence with the mean whole head average SAR of 3.16 W/kg. Temperatures were measured using fluoroptic probes at the scalp, first and second electrodes from the distal lead tip, and 6 mm distal from electrode 1 (T6mm). The heating was modeled using the maximum T6mm and imaged using a proton resonance frequency shift based MR thermometry method. Results showed that the heating was significantly reduced when the extra-cranial lead was placed in the longitudinal direction compared to the other placements (peak temperature change = 1.5–3.2 °C vs 5.1–24.7 °C). Thermal modeling and MR thermometry may be used together to determine the heating and improve patient safety online. PMID:22892760

Shrivastava, Devashish; Abosch, Aviva; Hughes, John; Goerke, Ute; DelaBarre, Lance; Visaria, Rachana; Harel, Noam; Vaughan, J. Thomas

2012-01-01

377

Transcranial direct current stimulation of the primary motor cortex improves word-retrieval in older adults.  

PubMed

Language facilitation by transcranial direct current stimulation (tDCS) in healthy individuals has generated hope that tDCS may also allow improving language impairment after stroke (aphasia). However, current stimulation protocols have yielded variable results and may require identification of residual language cortex using functional magnetic resonance imaging (fMRI), which complicates incorporation into clinical practice. Based on previous behavioral studies that demonstrated improved language processing by motor system pre-activation, the present study assessed whether tDCS administered to the primary motor cortex (M1) can enhance language functions. This proof-of-concept study employed a sham-tDCS controlled, cross-over, within-subject design and assessed the impact of unilateral excitatory (anodal) and bihemispheric (dual) tDCS in 18 healthy older adults during semantic word-retrieval and motor speech tasks. Simultaneous fMRI scrutinized the neural mechanisms underlying tDCS effects. Both active tDCS conditions significantly improved word-retrieval compared to sham-tDCS. The direct comparison of activity elicited by word-retrieval vs. motor-speech trials revealed bilateral frontal activity increases during both anodal- and dual-tDCS compared to sham-tDCS. This effect was driven by more pronounced deactivation of frontal regions during the motor-speech task, while activity during word-retrieval trials was unaffected by the stimulation. No effects were found in M1 and secondary motor regions. Our results show that tDCS administered to M1 can improve word-retrieval in healthy individuals, thereby providing a rationale to explore whether M1-tDCS may offer a novel approach to improve language functions in aphasia. Functional magnetic resonance imaging revealed neural facilitation specifically during motor speech trials, which may have reduced switching costs between the overlapping neural systems for lexical retrieval and speech processing, thereby resulting in improved performance. PMID:25295004

Meinzer, Marcus; Lindenberg, Robert; Sieg, Mira M; Nachtigall, Laura; Ulm, Lena; Flöel, Agnes

2014-01-01

378

Baseline effects of transcranial direct current stimulation on glutamatergic neurotransmission and large-scale network connectivity.  

PubMed

Transcranial direct current stimulation (tDCS) modulates glutamatergic neurotransmission and can be utilized as a novel treatment intervention for a multitude of populations. However, the exact mechanism by which tDCS modulates the brain?s neural architecture, from the micro to macro scales, have yet to be investigated. Using a within-subjects design, resting-state functional magnetic resonance imaging (rs-fMRI) and proton magnetic resonance spectroscopy ((1)H MRS) were performed immediately before and after the administration of anodal tDCS over right parietal cortex. Group independent component analysis (ICA) was used to decompose fMRI scans into 75 brain networks, from which 12 resting-state networks were identified that had significant voxel-wise functional connectivity to anatomical regions of interest. (1)H MRS was used to obtain estimates of combined glutamate and glutamine (Glx) concentrations from bilateral intraparietal sulcus. Paired sample t-tests showed significantly increased Glx under the anodal electrode, but not in homologous regions of the contralateral hemisphere. Increases of within-network connectivity were observed within the superior parietal, inferior parietal, left frontal-parietal, salience and cerebellar intrinsic networks, and decreases in connectivity were observed in the anterior cingulate and the basal ganglia (p<0.05, FDR-corrected). Individual differences in Glx concentrations predicted network connectivity in most of these networks. The observed relationships between glutamatergic neurotransmission and network connectivity may be used to guide future tDCS protocols that aim to target and alter neuroplastic mechanisms in healthy individuals as well as those with psychiatric and neurologic disorders. PMID:25312829

Hunter, Michael A; Coffman, Brian A; Gasparovic, Charles; Calhoun, Vince D; Trumbo, Michael C; Clark, Vincent P

2015-01-12

379

Opening of the Gulf of Mexico and the Nature of the Crust in the Deep Gulf: New Evidence from Seafloor Spreading Magnetic Anomalies  

NASA Astrophysics Data System (ADS)

The seafloor spreading history in the Gulf of Mexico is poorly constrained due to a lack of recognized seafloor spreading magnetic anomalies, a paucity of deep penetrating seismic data, and absence of drilling to constrain crystalline ocean floor composition and ages. We have identified lineated magnetic anomalies in the eastern Gulf on profiles collected during the Woods Hole R/V Farnella FRNL85-2 cruise that correlate with magnetic chrons M21R to M10. Forward modeling shows that these anomalies formed during creation of weakly magnetized new seafloor in the eastern Gulf between 149-134 Ma at an average half-spreading rate of 3.2 cm/yr. The oldest anomalies are located against stretched continental crust beneath the western Florida shelf on the east and the Yucatan shelf on the west. The youngest anomalies form a juxtaposed conjugate pair that mark the location of an extinct spreading ridge between Yucatan and Florida. Seismic velocities of the crust in the eastern Gulf and the amplitude of the magnetic anomalies are similar to the Iberian and Newfoundland rifted margins, where the early stages of continental breakup were accommodated by exhumation of subcontinental lithosphere rather than creation of new basaltic oceanic crust. We infer that the eastern Gulf of Mexico is underlain by exhumed sub-continental peridotitic mantle intruded by lesser volumes of basaltic igneous rocks generated by decompression melting of the asthenosphere during the late stages of opening of the Gulf. The long wavelength characteristics of the magnetic and gravity fields in the eastern Gulf, as well as the seismic velocity structure of the crust, differ from those in the central and western Gulf, which are more similar to typical magmatic rifted margins. This suggests that the character of the Gulf changes along strike, from a magmatic western portion to an amagmatic eastern portion. Paleogeographic restoration of the lineated magnetic anomaly pattern suggests a 4-phase model for opening of the Gulf. During phase 1 (Early Permian-Late Triassic), Yucatan and associated tectonic blocks that now comprise eastern Mexico were translated eastward from the Pacific realm into positions near the modern western Gulf. During phase 2 (Late Triassic-ca. 160 Ma) Yucatan and the South Florida block were translated southeastward relative to North America, rotating 6.7? counterclockwise about a pole located at 34?N, 74?W. This resulted in ca. 430 km of southeastward extension on the North American coastal plain, 120 km of southward extension on the northern Yucatan shelf, and displacement of the South Florida Block from a pre-rift position on the northwest Florida shelf to its modern position. During phase 3 (ca. 160-149 Ma), Yucatan rotated counterclockwise 46? relative to North America about a pole located at 27.6?N, 84.0?W. Phase 3 may have coincided with seafloor spreading in the central and western Gulf, but predated seafloor spreading in the eastern Gulf. During phase 4 (149-134 Ma), Yucatan moved southwestward relative to North America, rotating counterclockwise 2.2? about a pole located at 17.6?N, 74.2?W and completing opening of the Gulf.

Harry, D. L.; Eskamani, P. K.

2013-12-01

380

DEEP RADIO CONTINUUM IMAGING OF THE DWARF IRREGULAR GALAXY IC 10: TRACING STAR FORMATION AND MAGNETIC FIELDS  

SciTech Connect

We exploit the vastly increased sensitivity of the Expanded Very Large Array to study the radio continuum and polarization properties of the post-starburst, dwarf irregular galaxy IC 10 at 6 cm, at a linear resolution of {approx}50 pc. We find close agreement between radio continuum and H{alpha} emission, from the brightest H II regions to the weaker emission in the disk. A quantitative analysis shows a strictly linear correlation, where the thermal component contributes 50% to the total radio emission, the remainder being due to a non-thermal component with a surprisingly steep radio spectral index of between -0.7 and -1.0 suggesting substantial radiation losses of the cosmic-ray electrons. We confirm and clearly resolve polarized emission at the 10%-20% level associated with a non-thermal superbubble, where the ordered magnetic field is possibly enhanced due to the compression of the expanding bubble. A fraction of the cosmic-ray electrons has likely escaped because the measured radio emission is a factor of three lower than what is suggested by the H{alpha}-inferred star formation rate.

Heesen, V.; Brinks, E. [Centre for Astrophysics Research, University of Hertfordshire, Hatfield AL10 9AB (United Kingdom); Rau, U.; Rupen, M. P. [NRAO, P.V.D. Science Operations Center, National Radio Astronomy Observatory, 1003 Lopezville Road, Socorro, NM 87801 (United States); Hunter, D. A. [Lowell Observatory, 1400 West Mars Hill Road, Flagstaff, AZ 86001 (United States)

2011-09-20