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Sample records for durchblutungsreserve vor geplantem

  1. Keine Panik vor Statistik!

    NASA Astrophysics Data System (ADS)

    Oestreich, Markus; Romberg, Oliver

    Die Statistik - unendliche Fragen. Sternzeit 0511,22: Wir schreiben das Jahr mit J wie "Juhu!" denn dies sind die Abenteuer der Doktorissimi Oestreich und Romberg, die mit Ihrem zusammen 28 Punkte zählenden IQ zwei Jahre lang unterwegs waren, um neue Statistik-Darstellungen zu erforschen, neue Formulierungen und neue Applikationen. Viele Lichtjahre von der faden Theorie entfernt, dringen die Autoren dabei in Phantasien vor, die nie ein Mensch zuvor so gehabt hat. Willkommen an Bord!

  2. A digital goniometer for VOR

    NASA Technical Reports Server (NTRS)

    Meer, S. A.

    1977-01-01

    A new VOR (VHF omni-range) goniometer design which promises to improve the reliability and maintainability of the VOR ground station is described. The heart of the new concept is the use of two digital phase shifters to produce the rotating figure-of-eight pattern of conventional VOR. Using digital circuits, the goniometer adjustments and calibration reduce to timing adjustments of binary signals. A common clock used for timing the digital phase shifters also synchronizes the 30 Hz modulation of the 9.96 kHz reference.

  3. VOR area navigation - Techniques and results

    NASA Technical Reports Server (NTRS)

    Ragsdale, W. A.

    1982-01-01

    Several methods for deriving position from VOR (without DME) have been developed and evaluated in this study. These methods permit navigation to arbitrary waypoints using either two VOR's or one VOR and a clock. These algorithms have been tested in computer simulations and in flight tests. The single VOR method appears to be the most practical and is a candidate for an automated light plane area navigation system, called VORNAV.

  4. Evaluation of the torsional VOR in weightlessness.

    PubMed

    Clarke, A H; Teiwes, W; Scherer, H

    1993-01-01

    The experimental concept and findings from a recent manned orbital spaceflight are described. Together with ongoing terrestrial and parabolic studies, the present experiment is intended to further our knowledge of the sensory integrative processing of information from the semicircular canals and the otolithic receptors, and to quantify the presumed otolithic adaptation to altered gravito-inertial force environments in a more reliable manner than to date. The experiment included measurement of the basic vestibulo-oculomotor response during active head rotation about each of the three orthogonal axes. Priority was given to the recording of ocular torsion, as elicited by head oscillation about the roll axis, and thus due to the concomitant stimulation of the semicircular canals and otolith receptors. Videooculography was employed for the measurement of eye movements; head movement was measured by three orthogonally arranged angular rate sensors and a triaxial linear accelerometer device. All signals were recorded synchronously on a video/data recorder. Preliminary results indicate alterations in the torsional VOR under zero-g conditions, suggesting an adaptive modification of the torsional VOR gain over the course of the 6-day orbital flight. In addition, the inflight test findings yielded discrepancies between intended and performed head movement, indicating impairment in sensorimotor coordination under prolonged microgravity conditions.

  5. Adaptation of VOR to Coriolis stimulation.

    PubMed

    Adenot, Sophie; Jarchow, Thomas; Young, Laurence R

    2005-04-01

    The vestibulo-ocular reflex (VOR) is normally characterized by the gain and phase of slow-phase velocity (SPV) relative to the stimulus velocity. Although this is perfectly satisfactory for steady-state sinusoidal oscillations about a single axis, it is less useful when applied to transient responses. The well-known decay of nystagmus following a step change of head velocity approximately follows a double exponential, with an initial amplitude (A), a long time constant (tau), and an adaptation time constant (tau(a)). We have developed a means of representing the transient response for a complex head velocity stimulus as experienced during high-speed artificial gravity (AG) experiments. When a subject, lying supine on a rotating horizontal platform, makes a yaw head movement of amplitude theta, the vertical semicircular canals experience a step in angular velocity. The pitch stimulus is equal to the change in the component of the centrifuge angular velocity (omega(c)) aligned with the interaural axis, and gives rise to a vertical VOR. The magnitude of the step change is omega(c) sin theta. The SPV is approximated by an exponential decay of amplitude A and single time constant tau, and then normalized relative to this stimulus step. MATLAB scripts filter the raw eye position data to remove noise, blinks, and saccades, differentiate the signal, and remove fast phases to obtain SPV. The amplitude of the fitted SPV exponential is divided by omega(c) sin theta to obtain the normalized SPV. A and tau are shown to behave differently as subjects adapt to repeated head movements of different amplitudes.

  6. 77 FR 64444 - VOR Federal Airway V-595; Oregon

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-10-22

    ... ``significant rule'' under Department of Transportation (DOT) Regulatory Policies and Procedures (44 FR 11034... read as follows: Authority: 49 U.S.C. 106(g), 40103, 40113, 40120; E.O. 10854, 24 FR 9565, 3 CFR, 1959... Federal Aviation Administration 14 CFR Part 71 RIN 2120-AA66 VOR Federal Airway V-595; Oregon...

  7. Liposomal voriconazole (VOR) formulation for improved ocular delivery.

    PubMed

    de Sá, Fernando Augusto Pires; Taveira, Stephânia Fleury; Gelfuso, Guilherme Martins; Lima, Eliana Martins; Gratieri, Taís

    2015-09-01

    Treating infectious eye diseases topically requires a drug delivery system capable of overcoming the eye's defense mechanisms, which efficiently reduce the drug residence time right after its administration, therefore reducing absorption. In order to try to surpass such administration issues and improve life quality for patients with fungal keratitis, liposomal voriconazol (VOR) formulations were prepared. Formulations were composed of soy phosphatidylcholine (PC) containing or not 1,2-dioleoyl-3-trimethylammonium-propane (DOTAP) and cholesterol. Liposomes were characterized by their drug entrapment efficiency (EE), drug recovery (DR), average diameter (size) and polydispersivity index (PdI). In vitro mucosal interaction and irritancy levels, ex vivo permeation, as well as the short-term stability were also assessed. Liposomal VOR formulation produced with 7.2:40mM VOR:PC showed to be the most promising formulation: mean size of 116.6±5.9nm, narrow PdI (0.17±0.06), negative zeta potential (∼-7mV) and over 80% of EE and yield, remaining stable for at least 30 days in solution and 90 days after lyophilization. This formulation was classified as 'non-irritant' after HET-CAM's test and was able to deliver about 47.85±5.72μg/cm(2) of VOR into porcine cornea after 30min of permeation test. Such drug levels are higher than the minimal inhibitory concentrations (MIC) of several fungi species isolated from clinical cases of corneal keratitis. Overall results suggest VOR can be effectively incorporated in liposomes for potential topical treatment of fungal keratitis. PMID:26123854

  8. Updating inertial navigation systems with VOR/DME information.

    NASA Technical Reports Server (NTRS)

    Bobick, J. C.; Bryson, A. E., Jr.

    1972-01-01

    Demonstration that updating an inertial navigation system (INS) with VOR/DME information (from one or two stations) by means of a maximum-likelihood filter results in substantial improvements in navigational accuracy over that obtained by the use of a single VOR/DME (current practice). When continuously updating, the use of a high-quality INS (0.01 deg/hr gyro drift) instead of a low-quality INS (1.0 deg/hr gyro drift) does not substantially improve position accuracy. In-flight alignment (or realignment) of an INS to an accuracy comparable to that of ground alignment can be accomplished by using two DMEs. Several reduced-order suboptimal filters were found to perform nearly optimally.

  9. Multiple timescales in the adaptation of the rotational VOR

    PubMed Central

    Colagiorgio, Paolo; Bertolini, Giovanni; Bockisch, Christopher J.; Straumann, Dominik

    2015-01-01

    Goal-directed movements, such as pointing and saccades, have been shown to share similar neural architectures, in spite of the different neuromuscular systems producing them. Such structure involve an inverse model of the actuator being controlled, which produces the commands innervating the muscles, and a forward model of the actuator, which predicts the sensory consequences of such commands and allows online movement corrections. Recent studies have shown that goal-directed movements also share similar motor-learning and motor-memory mechanisms, which are based on multiple timescales. The hypothesis that also the rotational vestibulo-ocular reflex (rVOR) may be based on a similar architecture has been presented recently. We hypothesize that multiple timescales are the brain's solution to the plasticity-stability dilemma, allowing adaptation to temporary and sudden changes while keeping stable motor-control abilities. If that were the case, then we would also expect the adaptation of reflex movements to follow the same principles. Thus we studied rVOR gain adaptation in eight healthy human subjects using a custom paradigm aimed at investigating the existence of spontaneous recovery, which we considered as the hallmark of multiple timescales in motor learning. Our experimental results show that spontaneous recovery occurred in six of eight subjects. Thus we developed a mathematical model of rVOR adaptation based on two hidden-states processes, which adapts the cerebellar-forward model of the ocular motor plant, and show that it accurately simulates our experimental data on rVOR gain adaptation, whereas a single timescale learning process fails to do so. PMID:25744882

  10. Listing's Plane and the 3D-VOR in Microgravity

    NASA Astrophysics Data System (ADS)

    Clarke, Andrew H.

    2008-06-01

    Listing's Plane (LP) and the 3D vestibulo-ocular response (3D-VOR) have been shown to be collinear under normal 1G conditions. Here LP and 3D-VOR were recorded under 1G and 0G conditions to determine whether this collinearity is dependent on the gravity vector. Ten healthy subjects participated in a parabolic flight study.. In 0G the orientation of Listing's Plane (LP) was consistently altered. LP elevation was tilted backwards by approx. 10° (p= 0.003). The azimuth angles of the left & right eyes also diverged in zero-G, with a statistically significant change (p = 0.04) in the vergence angle between 6.1 & 11.8°. A dissociation in torsional eye position between 1G and 0G was also observed, which proved to be statistically significant (p = 0.03). The results of spaceflight measurements onboard the ISS demonstrate that this LP re-orientation persists over six-month 0G periods. Furthermore postflight re-adaptation to 1G Earthbound conditions proceeds over several days to weeks. The findings support the idea that the absence of the gravity vector represents a qualitative change not only for vestibular and oculomotor responses, but also for the entire sensorimotor complex and the autonomic system.

  11. VOR Gain Is Related to Compensatory Saccades in Healthy Older Adults

    PubMed Central

    Anson, Eric R.; Bigelow, Robin T.; Carey, John P.; Xue, Qian-Li; Studenski, Stephanie; Schubert, Michael C.; Agrawal, Yuri

    2016-01-01

    Objective: Vestibulo-ocular reflex (VOR) gain is well-suited for identifying rotational vestibular dysfunction, but may miss partial progressive decline in age-related vestibular function. Since compensatory saccades might provide an alternative method for identifying subtle vestibular decline, we describe the relationship between VOR gain and compensatory saccades in healthy older adults. Methods: Horizontal VOR gain was measured in 243 subjects age 60 and older from the Baltimore Longitudinal Study of Aging using video head impulse testing (HIT). Saccades in each HIT were identified as either “compensatory” or “compensatory back-up,” i.e., same or opposite direction as the VOR response respectively. Saccades were also classified as “covert” (occurring during head movement) and “overt” (occurring after head movement). The relationship between VOR gain and percentage of HITs with saccades, as well as the relationship between VOR gain and saccade latency and amplitude, were evaluated using regression analyses adjusting for age, gender, and race. Results: In adjusted analyses, the percentage of HITs with compensatory saccades increased 4.5% for every 0.1 decrease in VOR gain (p < 0.0001). Overt compensatory saccade amplitude decreased 0.6° (p < 0.005) and latency increased 90 ms (p < 0.001) for every 0.1 increase in VOR gain. Covert back-up compensatory saccade amplitude increased 0.4° for every 0.1 increase in VOR gain. Conclusion: We observed significant relationships between VOR gain and compensatory saccades in healthy older adults. Lower VOR gain was associated with larger amplitude, shorter latency compensatory saccades. Compensatory saccades reflect underlying rotational vestibular hypofunction, and may be particularly useful at identifying partial vestibular deficits as occur in aging adults. PMID:27445793

  12. 14 CFR 71.15 - Designation of jet routes and VOR Federal airways.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 14 Aeronautics and Space 2 2011-01-01 2011-01-01 false Designation of jet routes and VOR Federal airways. 71.15 Section 71.15 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF... ROUTES; AND REPORTING POINTS § 71.15 Designation of jet routes and VOR Federal airways. Unless...

  13. 14 CFR 71.15 - Designation of jet routes and VOR Federal airways.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 14 Aeronautics and Space 2 2010-01-01 2010-01-01 false Designation of jet routes and VOR Federal... TRANSPORTATION (CONTINUED) AIRSPACE DESIGNATION OF CLASS A, B, C, D, AND E AIRSPACE AREAS; AIR TRAFFIC SERVICE ROUTES; AND REPORTING POINTS § 71.15 Designation of jet routes and VOR Federal airways. Unless...

  14. Effect of Spaceflight on Vestibulo-Ocular Reflexes (VORS) During Angular Head Motion

    NASA Technical Reports Server (NTRS)

    Tomko, David L.; Clifford, James O.; Hargens, Alan R. (Technical Monitor)

    1996-01-01

    Vestibulo-ocular reflexes (VORs) stabilize the eyes during head motion. During Earth-horizontal (E-H) pitch or roll rotations, canal and otolith stimuli occur together. In Earth-vertical (E-V) pitch or roll rotations, only canal signals occur. In cats and squirrel monkeys, pitch/roll VOR gains during E-H motion have been shown to be larger than during E-V motion, implying that otolith modulation plays a role in producing angular VORs (aVORs). The present experiments replicated this experiment in rhesus monkeys, and examined how spaceflight affected AVOR gain. During yaw, pitch and roll (0.5 - 1.0 Hz, 40-50 deg/s pk) motion, 3-d eye movements were recorded in four Rhesus monkeys using scleral search coils. Mean E-H and E-V pitch VOR gains were 0.85 and 0.71. Torsional VOR gains during E-H and E-V were 0.47 and 0.39. Gains are more compensatory during E-H pitch or roll. Two of the four monkeys flew for 11 days on the COSMOS 2229 Biosatellite. E-H pitch VOR gains were attenuated immediately (72 hrs) post-flight, with similar values to pre-flight E-V pitch gains. Horizontal yaw VOR gains were similar pre- and post-flight.

  15. Vestibular Compensation in Unilateral Patients Often Causes Both Gain and Time Constant Asymmetries in the VOR

    PubMed Central

    Ranjbaran, Mina; Katsarkas, Athanasios; Galiana, Henrietta L.

    2016-01-01

    The vestibulo-ocular reflex (VOR) is essential in our daily life to stabilize retinal images during head movements. Balanced vestibular functionality secures optimal reflex performance which otherwise can be distorted by peripheral vestibular lesions. Luckily, vestibular compensation in different neuronal sites restores VOR function to some extent over time. Studying vestibular compensation gives insight into the possible mechanisms for plasticity in the brain. In this work, novel experimental analysis tools are employed to reevaluate the VOR characteristics following unilateral vestibular lesions and compensation. Our results suggest that following vestibular lesions, asymmetric performance of the VOR is not only limited to its gain. Vestibular compensation also causes asymmetric dynamics, i.e., different time constants for the VOR during leftward or rightward passive head rotation. Potential mechanisms for these experimental observations are provided using simulation studies. PMID:27065839

  16. Vestibular Compensation in Unilateral Patients Often Causes Both Gain and Time Constant Asymmetries in the VOR.

    PubMed

    Ranjbaran, Mina; Katsarkas, Athanasios; Galiana, Henrietta L

    2016-01-01

    The vestibulo-ocular reflex (VOR) is essential in our daily life to stabilize retinal images during head movements. Balanced vestibular functionality secures optimal reflex performance which otherwise can be distorted by peripheral vestibular lesions. Luckily, vestibular compensation in different neuronal sites restores VOR function to some extent over time. Studying vestibular compensation gives insight into the possible mechanisms for plasticity in the brain. In this work, novel experimental analysis tools are employed to reevaluate the VOR characteristics following unilateral vestibular lesions and compensation. Our results suggest that following vestibular lesions, asymmetric performance of the VOR is not only limited to its gain. Vestibular compensation also causes asymmetric dynamics, i.e., different time constants for the VOR during leftward or rightward passive head rotation. Potential mechanisms for these experimental observations are provided using simulation studies. PMID:27065839

  17. Modeling learning in brain stem and cerebellar sites responsible for VOR plasticity

    NASA Technical Reports Server (NTRS)

    Quinn, K. J.; Didier, A. J.; Baker, J. F.; Peterson, B. W.

    1998-01-01

    A simple model of vestibuloocular reflex (VOR) function was used to analyze several hypotheses currently held concerning the characteristics of VOR plasticity. The network included a direct vestibular pathway and an indirect path via the cerebellum. An optimization analysis of this model suggests that regulation of brain stem sites is critical for the proper modification of VOR gain. A more physiologically plausible learning rule was also applied to this network. Analysis of these simulation results suggests that the preferred error correction signal controlling gain modification of the VOR is the direct output of the accessory optic system (AOS) to the vestibular nuclei vs. a signal relayed through the cerebellum via floccular Purkinje cells. The potential anatomical and physiological basis for this conclusion is discussed, in relation to our current understanding of the latency of the adapted VOR response.

  18. Modeling learning in brain stem and cerebellar sites responsible for VOR plasticity.

    PubMed

    Quinn, K J; Didier, A J; Baker, J F; Peterson, B W

    1998-07-01

    A simple model of vestibuloocular reflex (VOR) function was used to analyze several hypotheses currently held concerning the characteristics of VOR plasticity. The network included a direct vestibular pathway and an indirect path via the cerebellum. An optimization analysis of this model suggests that regulation of brain stem sites is critical for the proper modification of VOR gain. A more physiologically plausible learning rule was also applied to this network. Analysis of these simulation results suggests that the preferred error correction signal controlling gain modification of the VOR is the direct output of the accessory optic system (AOS) to the vestibular nuclei vs. a signal relayed through the cerebellum via floccular Purkinje cells. The potential anatomical and physiological basis for this conclusion is discussed, in relation to our current understanding of the latency of the adapted VOR response. PMID:9671263

  19. An assessment of the vestibulo-ocular reflex (VOR) in persons with Down syndrome.

    PubMed

    Costa, Alberto C S

    2011-10-01

    Down syndrome (DS), the most common genetically defined cause of intellectual disability, is the phenotypic consequence of a supernumerary chromosome 21. Persons with DS commonly display deficits in visuomotor integration, motor coordination, and balance. Despite the key roles of the optokinetic and vestibular systems in these submodalities of motor function, a systematic investigation into the optokinetic nystagmus (OKN) and vestibulo-ocular reflex (VOR) in persons with DS was lacking in the literature. Accordingly, this study generated quantitative data on oculomotor function in persons with DS under vestibular stimulation (an accompanying work describes results on the analysis of optokinetic function in the same cohort of participants). Experiments involved 32 participants with DS (14-36 years old, equally divided by gender) and 32 chronological age- and gender-matched typically developing controls. Eye movements were recorded by binocular video-oculography, and a servo-controlled rotary chair produced vestibular stimulation. Participants were assessed for VOR during step, ramp, and sinusoidal stimulations; inhibition of the VOR by visual target fixation; and VOR adaptation to conflicting visual input. Individuals with DS displayed small alterations in the VOR gain and dynamics compared to controls. In contrast, the number of VOR nystagmus beats and the ability to inhibit the VOR by visual target fixation were markedly and robustly smaller in persons with DS. Significantly increased VOR adaptation was observed in men with DS. These findings may have implications to the understanding of the neurological basis of the motor dysfunction that affects performance in many practical tasks persons with DS encounter in their everyday lives.

  20. Dependence of the roll angular vestibuloocular reflex (aVOR) on gravity.

    PubMed

    Yakushin, Sergei B; Xiang, Yongqing; Cohen, Bernard; Raphan, Theodore

    2009-11-01

    Little is known about the dependence of the roll angular vestibuloocular reflex (aVOR) on gravity or its gravity-dependent adaptive properties. To study gravity-dependent characteristics of the roll aVOR, monkeys were oscillated about a naso-occipital axis in darkness while upright or tilted. Roll aVOR gains were largest in the upright position and decreased by 7-15% as animals were tilted from the upright. Thus the unadapted roll aVOR gain has substantial gravitational dependence. Roll gains were also decreased or increased by 0.25 Hz, in- or out-of-phase rotation of the head and the visual surround while animals were prone, supine, upright, or in side-down positions. Gain changes, determined as a function of head tilt, were fit with a sinusoid; the amplitudes represented the amount of the gravity-dependent gain change, and the bias, the gravity-independent gain change. Gravity-dependent gain changes were absent or substantially smaller in roll (approximately 5%) than in yaw (25%) or pitch (17%), whereas gravity-independent gain changes were similar for roll, pitch, and yaw (approximately 20%). Thus the high-frequency roll aVOR gain has an inherent dependence on head orientation re gravity in the unadapted state, which is different from the yaw/pitch aVORs. This inherent gravitational dependence may explain why the adaptive circuits are not active when the head is tilted re gravity during roll aVOR adaptation. These behavioral differences support the idea that there is a fundamental difference in the central organization of canal-otolith convergence of the roll and yaw/pitch aVORs.

  1. A design study of VOR: A versatile optimal resolution chopper spectrometer for the ESS

    NASA Astrophysics Data System (ADS)

    Deen, P. P.; Vickery, A.; Andersen, K. H.; Hall-Wilton, R.

    2015-01-01

    VOR, the versatile optimal resolution chopper spectrometer, is designed to probe dynamic phenomena that are currently inaccessible for inelastic neutron scattering due to flux limitations. VOR is a short instrument by the standards of the European Spallation Source (ESS), 30.2 m moderator to sample, and provides instantaneous access to a broad dynamic range, 1-120 meV within each ESS period. The short instrument length combined with the long ESS pulse width enables a quadratic flux increase, even at longer wavelengths, by relaxing energy resolution from ΔE/E = 1% up to ΔE/E = 7%. This is impossible both on a long chopper spectrometer at the ESS and with instruments at short pulsed sources. In comparison to current day chopper spectrometers, VOR can offer an order of magnitude improvement in flux for equivalent energy resolutions, ΔE/E = 1-3%. Further relaxing the energy resolution enables VOR to gain an extra order of magnitude in flux. In addition, VOR has been optimised for repetition rate multiplication (RRM) and is therefore able to measure, in a single ESS period, 6-14 incident wavelengths, across a wavelength band of 9 Å with a novel chopper configuration that transmits all incident wavelengths with equivalent counting statistics. The characteristics of VOR make it a unique instrument with capabilities to access small, limited-lifetime samples and transient phenomena with inelastic neutron scattering.

  2. The under-compensatory roll aVOR does not affect dynamic visual acuity.

    PubMed

    Schubert, Michael C; Migliaccio, Americo A; Ng, Tammy W C; Shaikh, Aasef G; Zee, David S

    2012-08-01

    Rotations of the head evoke compensatory reflexive eye rotations in the orbit to stabilize images onto the fovea. In normal humans, the angular vestibulo-ocular reflex (aVOR) gain (eye/head velocity) changes depending on the head rotation plane. For pitch and yaw head rotations, the gain is near unity, but during roll head rotations, the aVOR gain is ∼ 0.7. The purpose of this study was to determine whether this physiological discrepancy affects dynamic visual acuity (DVA)--a functional measure of the aVOR that requires subjects to identify letters of varying acuities during head rotation. We used the scleral search coil technique to measure eye and head velocity during passive DVA testing in yaw, roll, and pitch head impulses in healthy controls and patients with unilateral vestibular hypofunction (UVH). For control subjects, the mean aVOR gain during roll impulses was significantly lower than the mean aVOR gain during yaw and pitch impulses; however, there was no difference in DVA between yaw, roll, or pitch. For subjects with UVH, only aVOR gain during head rotations toward the affected side (yaw) were asymmetric (ipsilesional, 0.32 ± 0.17, vs. contralesional, 0.95 ± 0.05), with no asymmetry during roll or pitch. Similarly, there was a large asymmetry for DVA only during yaw head rotations, with no asymmetry in roll or pitch. Interestingly, DVA during roll toward the affected ear was better than DVA during yaw toward the affected ear--even though the ipsilesional roll aVOR gain was 60 % lower. During roll, the axis of eye rotation remains nearly perpendicular to the fovea, resulting in minimal displacement between the fovea and fixation target image projected onto the back of the eye. For subjects with UVH, the DVA score during passive horizontal impulses is a better indicator of poor gaze stability than during passive roll or pitch.

  3. 76 FR 12645 - Proposed Revocation of VOR Federal Airway V-284; New Jersey

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-03-08

    ... amend Title 14, Code of Federal Regulations (14 CFR) part 71 by removing VOR Federal Airway V-284 (75 FR... NPRM published in the Federal Register on September 3, 2010 (75 FR 54058) . Authority: 49 U.S.C. 106(g), 40103, 40113, 40120; E.O. 10854; 24 FR 9565, 3 CFR, 1959-1963 Comp., p. 389. Issued in Washington,...

  4. 78 FR 24346 - Modification of VOR Federal Airway V-595, Oregon

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-04-25

    ... (77 FR 64444). Interested parties were invited to participate in this rulemaking effort by submitting... FAA issued a supplemental NPRM (SNPRM) (78 FR 9009, February 7, 2013) to solicit comments on a... area (78 FR 4354, January 22, 2013. VOR Federal airways are published in paragraph 6010(a) of FAA...

  5. 78 FR 9009 - Proposed Amendment of VOR Federal Airway V-595; OR

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-02-07

    ... Federal airway V-595 due to the planned decommissioning of the Portland, OR, VOR/DME (77 FR 64444). No... ``significant rule'' under Department of Transportation (DOT) Regulatory Policies and Procedures (44 FR 11034... read as follows: Authority: 49 U.S.C. 106(g), 40103, 40113, 40120; E.O. 10854, 24 FR 9565, 3 CFR,...

  6. 77 FR 26160 - Modification of VOR Federal Airway V-14; Missouri

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-05-03

    ..., 40120; E.O. 10854, 24 FR 9565, 3 CFR, 1959-1963 Comp., p. 389. Sec. 71.1 0 2. The incorporation by... the Federal Register of May 7, 1990 (55 FR 18862), the St. Louis, MO, VOR/DME was deleted from the... Department of Transportation (DOT) Regulatory Policies and Procedures (44 FR 11034; February 26, 1979);...

  7. 76 FR 2800 - Amendment of VOR Federal Airways V-2 and V-21; Hawaii

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-01-18

    ... and Procedures (44 FR 11034; February 26, 1979); and (3) does not warrant preparation of a regulatory..., 40113, 40120; E.O. 10854, 24 FR 9565, 3 CFR, 1959-1963 Comp., p. 389. Sec. 71.1 0 2. The incorporation... TRANSPORTATION Federal Aviation Administration 14 CFR Part 71 Amendment of VOR Federal Airways V-2 and...

  8. 78 FR 21856 - Proposed Amendment of VOR Federal Airway V-537; GA

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-04-12

    ... Moultrie, GA, VOR/DME facility (77 FR 62468, October 15, 2012). The public comment period closed on... Policies and Procedures (44 FR 11034; February 26, 1979); and (3) does not warrant preparation of a... continues to read as follows: Authority: 49 U.S.C. 106(g), 40103, 40113, 40120; E.O. 10854, 24 FR 9565,...

  9. Horizontal Eye Position Affects Measured Vertical VOR Gain on the Video Head Impulse Test

    PubMed Central

    McGarvie, Leigh A.; Martinez-Lopez, Marta; Burgess, Ann M.; MacDougall, Hamish G.; Curthoys, Ian S.

    2015-01-01

    Background/hypothesis: With the video head impulse test (vHIT), the vertical VOR gain is defined as (vertical eye velocity/vertical head velocity), but compensatory eye movements to vertical canal stimulation usually have a torsional component. To minimize the contribution of torsion to the eye movement measurement, the horizontal gaze direction should be directed 40° from straight ahead so it is in the plane of the stimulated canal plane pair. Hypothesis: as gaze is systematically moved horizontally away from canal plane alignment, the measured vertical VOR gain should decrease. Study design: Ten healthy subjects, with vHIT measuring vertical eye movement to head impulses in the plane of the left anterior-right posterior (LARP) canal plane, with gaze at one of five horizontal gaze positions [40°(aligned with the LARP plane), 20°, 0°, −20°, −40°]. Methods: Every head impulse was in the LARP plane. The compensatory eye movement was measured by the vHIT prototype system. The one operator delivered every impulse. Results: The canal stimulus remained identical across trials, but the measured vertical VOR gain decreased as horizontal gaze angle was shifted away from alignment with the LARP canal plane. Conclusion: In measuring vertical VOR gain with vHIT the horizontal gaze angle should be aligned with the canal plane under test. PMID:25852637

  10. 76 FR 82114 - Amendment of VOR Federal Airways V-320 and V-440; Alaska

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-12-30

    ... and efficient management of Instrument Flight Rules (IFR) operations within the National Airspace... Anchorage VOR navigation aid (76 FR 68674). Interested parties were invited to participate in this... (44 FR 11034; February 26, 1979); and (3) does not warrant preparation of a regulatory evaluation...

  11. 76 FR 72093 - Amendment of VOR Federal Airways V-81, V-89, and V-169 in the Vicinity of Chadron, NE

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-11-22

    ... route structure, is being renamed the Toadstool VOR/DME to avoid confusion with Chadron Airport that... confusion to air traffic automation systems, as well as pilot/controller communications. To eliminate confusion, and a potential flight safety issue, the Chadron VOR/DME is renamed the Toadstool VOR/DME...

  12. Development of a VOR/DME model for an advanced concepts simulator

    NASA Technical Reports Server (NTRS)

    Steinmetz, G. G.; Bowles, R. L.

    1984-01-01

    The report presents a definition of a VOR/DME, airborne and ground systems simulation model. This description was drafted in response to a need in the creation of an advanced concepts simulation in which flight station design for the 1980 era can be postulated and examined. The simulation model described herein provides a reasonable representation of VOR/DME station in the continental United States including area coverage by type and noise errors. The detail in which the model has been cast provides the interested researcher with a moderate fidelity level simulator tool for conducting research and evaluation of navigator algorithms. Assumptions made within the development are listed and place certain responsibilities (data bases, communication with other simulation modules, uniform round earth, etc.) upon the researcher.

  13. Impaired vestibulo-ocular reflex (VOR) in spinocerebellar ataxia type 3 (SCA3): bedside and search coil evaluation.

    PubMed

    Gordon, Carlos R; Zivotofsky, Ari Z; Caspi, Avi

    2014-01-01

    Vestibulo-Ocular Reflex (VOR) abnormalities in cerebellar ataxias are a matter of renewed interest. We have previously reported vestibular areflexia in a group of Yemenite-Jews with Spinocerebellar Ataxia Type 3 (SCA3) who had clear bilateral pathological horizontal Head Impulse Test (HIT). The objective of this study was to evaluate the VOR of ten SCA3 patients who have variable bedside HIT responses by recording their eye movements using magnetic search coils and to correlate these results with their clinical and genetic data. Eight out of the ten patients have abnormal horizontal HIT detected by both clinical bedside examination and laboratory tests. Results of bedside HIT testing were significantly correlated with the VOR gain recorded using magnetic search coils. No significant correlations were found between VOR gain and other clinical or genetic data. Our study confirms the presence of defective VOR in SCA3 patients and corroborates the useful of the HIT as a reliable bedside test for diagnosis of VOR deficits.

  14. Impaired vestibulo-ocular reflex (VOR) in spinocerebellar ataxia type 3 (SCA3): bedside and search coil evaluation.

    PubMed

    Gordon, Carlos R; Zivotofsky, Ari Z; Caspi, Avi

    2014-01-01

    Vestibulo-Ocular Reflex (VOR) abnormalities in cerebellar ataxias are a matter of renewed interest. We have previously reported vestibular areflexia in a group of Yemenite-Jews with Spinocerebellar Ataxia Type 3 (SCA3) who had clear bilateral pathological horizontal Head Impulse Test (HIT). The objective of this study was to evaluate the VOR of ten SCA3 patients who have variable bedside HIT responses by recording their eye movements using magnetic search coils and to correlate these results with their clinical and genetic data. Eight out of the ten patients have abnormal horizontal HIT detected by both clinical bedside examination and laboratory tests. Results of bedside HIT testing were significantly correlated with the VOR gain recorded using magnetic search coils. No significant correlations were found between VOR gain and other clinical or genetic data. Our study confirms the presence of defective VOR in SCA3 patients and corroborates the useful of the HIT as a reliable bedside test for diagnosis of VOR deficits. PMID:25564077

  15. Spatial orientation of VOR to combined vestibular stimuli in squirrel monkeys.

    PubMed

    Merfeld, D M; Young, L R; Tomko, D L; Paige, G D

    1991-01-01

    The interaction of angular and linear stimuli produces a complex alignment of spatial orientation and the VOR. This phenomenon was studied by measuring three dimensional eye movements in 6 squirrel monkeys during centrifugation in the dark. The axis of eye rotation was always aligned with gravity and with the spinal axis of the upright monkeys. The erect monkeys were oriented such that they were either facing toward the direction of motion or were facing away from the motion. Angular velocity trapezoids were utilized as the motion stimuli with a ramp acceleration of 10 degrees/s2 to a constant velocity of 200 degrees/s. This yields a final centripetal acceleration of 1 g. The orientation of centripetal acceleration dramatically altered the VOR by changing the axis of eye rotation, the peak value of slow phase eye velocity, and the time constant of per-rotary decay. The axis of eye rotation always tended to align with gravito-inertial force, the peak value of slow phase eye velocity was greater when the monkey faced the motion than when it faced away from the motion, and the time constant of decay was smaller when the monkey faced the motion than when it faced away from the motion. These findings were statistically significant (p less than 0.05) and were consistent across all monkeys. The data also indicate that the VOR may be separated into two reflexes, a linear reflex and a rotational reflex. The linear reflex decays as the axis of eye rotation aligns with gravito-inertial force (GIF). These results indicate that GIF is resolved into two components: one representing an internal estimate of linear acceleration and one representing an internal estimate of gravity.

  16. A rodent model for artificial gravity: VOR adaptation and Fos expression.

    PubMed

    Kaufman, Galen; Weng, Tianxiang; Ruttley, Tara

    2005-01-01

    Vestibulo-ocular reflex (VOR) adaptation and brainstem Fos expression as a result of short radius cross-coupling stimuli were investigated to find neural correlates of the inherent Coriolis force asymmetry from an artificial gravity (AG) environment. Head-fixed gerbils (Meriones unguiculatus, N=79) were exposed, in the dark, to 60--90 minutes of cross-coupled rotations, combinations of pitch (or roll) and yaw rotation, while binocular horizontal, vertical, and torsional eye position were determined using infrared video-oculography. Centripetal acceleration in combination with angular cross-coupling was also studied. Simultaneous sinusoidal rotations in two planes (yaw with roll or pitch) provided a net symmetrical stimulus for the right and left labyrinths. In contrast, a constant velocity yaw rotation during sinusoidal roll or pitch provided the asymmetric stimulus model for AG. We found orthogonally oriented half-cycle VOR gain changes. The results depended on the direction of horizontal rotation during asymmetrical cross-coupling, and other aspects of the stimulus, including the phase relationship between the two rotational inputs, the symmetry of the stimulus, and training. Fos expression also revealed laterality differences in the prepositus and inferior olivary C subnucleus. In contrast the inferior olivary beta and ventrolateral outgrowth were labeled bilaterally. Additional cross-coupling dependent labeling was found in the flocculus, hippocampus, and several cortical regions, including the perirhinal and temporal association cortices. Analyses showed significant differences across the brain regions for several factors (symmetry, rotation velocity and direction, the presence of centripetal acceleration or a visual surround, and training). Finally, animals compensating from a unilateral surgical labyrinthectomy who received multiple cross-coupling training sessions had improved half-cycle VOR gain in the ipsilateral eye with head rotation toward the intact

  17. Horizontal angular VOR, nystagmus dumping, and sensation duration in spacelab SLS-1 crewmembers

    NASA Technical Reports Server (NTRS)

    Oman, C. M.; Balkwill, M. D.; Young, L. R. (Principal Investigator)

    1993-01-01

    In 1G, the apparent time constant (Td) of postrotatory SPV decay with the head tilted face down is 55% of that with head erect (Te). This phenomenon is called "nystagmus dumping" and has been attributed to G effects on VOR velocity storage. Similarly, postrotatory sensation duration with head tilted (Dd) is 32% of that when head erect (De). In parabolic flight, Te and De are 70% of 1-G values, but a pitch back dumping movement produces no further change. Te, Td, and Dd have not previously been measured in orbital flight. VOR and sensation duration was tested in 4 crewmembers in 4 preflight, 1 inflight (days 4 or 5) and 4 post flight sessions. Bitemporal EOG was recorded with eyes open in darkness. Instructions were to "gaze straight ahead," and indicate when "rotation sensation disappears or becomes ambiguous". Subjects were rotated CW and CCW head erect for 1 min at 120 degrees/s, stopped, and EOG was recorded for another 1 min. This procedure was then used to study dumping, except that immediately after chair stop, subjects pitched their head forward 90 degrees. SPV was calculated using order statistic filtering, and dropouts removed using an iterative model fitting method. Te and Td were determined by logarithmic linear regression of mean SPV for each subject. In orbit, 90 degrees pitch movement produced rapid subjective dumping, but not nystagmus dumping. Dd was noticeably shorter ("almost instantaneous") compared to preflight Dd. Te and Td in orbit were similar to preflight Te for 3/4 subjects (rather than to preflight Td as expected). No consistent VOR gain changes were seen in orbit. Although Te is known to decrease acutely in parabolic flight, a longer time constant was measured in 3/4 subjects after 4-5 days adaptation to weightlessness, suggesting a return of angular velocity storage.

  18. Short-term adaptation of the VOR: non-retinal-slip error signals and saccade substitution

    NASA Technical Reports Server (NTRS)

    Eggers, Sscott D Z.; De Pennington, Nick; Walker, Mark F.; Shelhamer, Mark; Zee, David S.

    2003-01-01

    We studied short-term (30 min) adaptation of the vestibulo-ocular reflex (VOR) in five normal humans using a "position error" stimulus without retinal image motion. Both before and after adaptation a velocity gain (peak slow-phase eye velocity/peak head velocity) and a position gain (total eye movement during chair rotation/amplitude of chair motion) were measured in darkness using search coils. The vestibular stimulus was a brief ( approximately 700 ms), 15 degrees chair rotation in darkness (peak velocity 43 degrees /s). To elicit adaptation, a straight-ahead fixation target disappeared during chair movement and when the chair stopped the target reappeared at a new location in front of the subject for gain-decrease (x0) adaptation, or 10 degrees opposite to chair motion for gain-increase (x1.67) adaptation. This position-error stimulus was effective at inducing VOR adaptation, though for gain-increase adaptation the primary strategy was to substitute augmenting saccades during rotation while for gain-decrease adaptation both corrective saccades and a decrease in slow-phase velocity occurred. Finally, the presence of the position-error signal alone, at the end of head rotation, without any attempt to fix upon it, was not sufficient to induce adaptation. Adaptation did occur, however, if the subject did make a saccade to the target after head rotation, or even if the subject paid attention to the new location of the target without actually looking at it.

  19. An Indirect System Identification Technique for Stable Estimation of Continuous-Time Parameters of the Vestibulo-Ocular Reflex (VOR)

    NASA Technical Reports Server (NTRS)

    Kukreja, Sunil L.; Wallin, Ragnar; Boyle, Richard D.

    2013-01-01

    The vestibulo-ocular reflex (VOR) is a well-known dual mode bifurcating system that consists of slow and fast modes associated with nystagmus and saccade, respectively. Estimation of continuous-time parameters of nystagmus and saccade models are known to be sensitive to estimation methodology, noise and sampling rate. The stable and accurate estimation of these parameters are critical for accurate disease modelling, clinical diagnosis, robotic control strategies, mission planning for space exploration and pilot safety, etc. This paper presents a novel indirect system identification method for the estimation of continuous-time parameters of VOR employing standardised least-squares with dual sampling rates in a sparse structure. This approach permits the stable and simultaneous estimation of both nystagmus and saccade data. The efficacy of this approach is demonstrated via simulation of a continuous-time model of VOR with typical parameters found in clinical studies and in the presence of output additive noise.

  20. Tuning of gravity-dependent and gravity-independent vertical angular VOR gain changes by frequency of adaptation.

    PubMed

    Yakushin, Sergei B

    2012-06-01

    The gain of the vertical angular vestibulo-ocular reflex (aVOR) was adaptively increased and decreased in a side-down head orientation for 4 h in two cynomolgus monkeys. Adaptation was performed at 0.25, 1, 2, or 4 Hz. The gravity-dependent and -independent gain changes were determined over a range of head orientations from left-side-down to right-side-down at frequencies from 0.25 to 10 Hz, before and after adaptation. Gain changes vs. frequency data were fit with a Gaussian to determine the frequency at which the peak gain change occurred, as well as the tuning width. The frequency at which the peak gravity-dependent gain change occurred was approximately equal to the frequency of adaptation, and the width increased monotonically with increases in the frequency of adaptation. The gravity-independent component was tuned to the adaptive frequency of 0.25 Hz but was uniformly distributed over all frequencies when the adaptation frequency was 1-4 Hz. The amplitude of the gravity-independent gain changes was larger after the aVOR gain decrease than after the gain increase across all tested frequencies. For the aVOR gain decrease, the phase lagged about 4° for frequencies below the adaptation frequency and led for frequencies above the adaptation frequency. For gain increases, the phase relationship as a function of frequency was inverted. This study demonstrates that the previously described dependence of aVOR gain adaptation on frequency is a property of the gravity-dependent component of the aVOR only. The gravity-independent component of the aVOR had a substantial tuning curve only at an adaptation frequency of 0.25 Hz.

  1. 75 FR 12675 - Amendment of VOR Federal Airway V-422 in the Vicinity of Wolf Lake, IN

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-03-17

    ...'' under DOT Regulatory Policies and Procedures (44 FR 11034; February 26, 1979); and (3) does not warrant...; E.O. 10854, 24 FR 9565, 3 CFR, 1959-1963 Comp., p. 389. Sec. 71.1 0 2. The incorporation by... Federal Aviation Administration 14 CFR Part 71 RIN 2120-AA66 Amendment of VOR Federal Airway V-422 in...

  2. Graphical Analysis of Electromagnetic Coupling on B-737 and B-757 Aircraft for VOR and LOC IPL Data

    NASA Technical Reports Server (NTRS)

    Jafri, Madiha; Ely, Jay; Vahala, Linda

    2005-01-01

    Electromagnetic coupling measurements were performed from numerous passenger cabin locations to aircraft instrument landing system localizer (LOC) and VHF Omni-Ranging (VOR) systems. This paper presents and compares the data for B-757 and B-737 airplanes, and provides a basis for fuzzy modeling of coupling patterns in different types of airplanes and airplanes with different antenna locations.

  3. 78 FR 37103 - Amendment of VOR Federal Airways V-55 and V-169 in Eastern North Dakota

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-06-20

    ... in Part 71 by removing reference to special use airspace (SUA) exclusionary language no longer needed..., the FAA took action to amend VOR Federal airways V-55 (44 FR 43714, July 26, 1979) and V-169 (44 FR... the existing exclusionary language contained in the V-55 description under Part 71 when the...

  4. Full-Body Gaze Control Mechanisms Elicited During Locomotion: Effects Of VOR Adaptation

    NASA Technical Reports Server (NTRS)

    Mulavara, A. P.; Houser, J.; Peters, B.; Miller, C.; Richards, J.; Marshburn, A.; Brady, R.; Cohen, H.; Bloomberg, J. J.

    2004-01-01

    Control of locomotion requires precise interaction between several sensorimotor subsystems. During locomotion the performer must satisfy two performance criteria: maintain stable forward translation and to stabilize gaze (McDonald, et al., 1997). Precise coordination demands integration of multiple sensorimotor subsystems for fulfilling both criteria. In order to test the general hypothesis that the whole body can serve as an integrated gaze stabilization system, we have previously investigated how the multiple, interdependent full-body sensorimotor subsystems respond to changes in gaze stabilization task constraints during locomotion (Mulavara and Bloomberg, 2003). The results suggest that the full body contributes to gaze stabilization during locomotion, and that its different functional elements respond to changes in visual task constraints. The goal of this study was to determine how the multiple, interdependent, full-body sensorimotor subsystems aiding gaze stabilization during locomotion are functionally coordinated after the vestibulo-ocular reflex (VOR) gain has been altered. We investigated the potential of adaptive remodeling of the full-body gaze control system following exposure to visual-vestibular conflict known to adaptively reduce the VOR. Subjects (n=14) walked (6.4 km/h) on the treadmill before and after they were exposed to 0.5X manifying lenses worn for 30 minutes during self-generated sinusoidal vertical head rotations performed while seated. In this study we measured: temporal parameters of gait, full body sagittal plane segmental kinematics of the head, trunk, thigh, shank and foot, accelerations along the vertical axis at the head and the shank, and the vertical forces acting on the support surface. Results indicate that, following exposure to the 0.5X minifying lenses, there was a significant increase in the duration of stance and stride times, alteration in the amplitude of head movement with respect to space and a significant increase in

  5. A least-squares parameter estimation algorithm for switched hammerstein systems with applications to the VOR

    NASA Technical Reports Server (NTRS)

    Kukreja, Sunil L.; Kearney, Robert E.; Galiana, Henrietta L.

    2005-01-01

    A "Multimode" or "switched" system is one that switches between various modes of operation. When a switch occurs from one mode to another, a discontinuity may result followed by a smooth evolution under the new regime. Characterizing the switching behavior of these systems is not well understood and, therefore, identification of multimode systems typically requires a preprocessing step to classify the observed data according to a mode of operation. A further consequence of the switched nature of these systems is that data available for parameter estimation of any subsystem may be inadequate. As such, identification and parameter estimation of multimode systems remains an unresolved problem. In this paper, we 1) show that the NARMAX model structure can be used to describe the impulsive-smooth behavior of switched systems, 2) propose a modified extended least squares (MELS) algorithm to estimate the coefficients of such models, and 3) demonstrate its applicability to simulated and real data from the Vestibulo-Ocular Reflex (VOR). The approach will also allow the identification of other nonlinear bio-systems, suspected of containing "hard" nonlinearities.

  6. Can low-cost VOR and Omega receivers suffice for RNAV - A new computer-based navigation technique

    NASA Technical Reports Server (NTRS)

    Hollaar, L. A.

    1978-01-01

    It is shown that although RNAV is particularly valuable for the personal transportation segment of general aviation, it has not gained complete acceptance. This is due, in part, to its high cost and the necessary special-handling air traffic control. VOR/DME RNAV calculations are ideally suited for analog computers, and the use of microprocessor technology has been suggested for reducing RNAV costs. Three navigation systems, VOR, Omega, and DR, are compared for common navigational difficulties, such as station geometry, siting errors, ground disturbances, and terminal area coverage. The Kalman filtering technique is described with reference to the disadvantages when using a system including standard microprocessors. An integrated navigation system, using input data from various low-cost sensor systems, is presented and current simulation studies are noted.

  7. Adaptation of primate vestibuloocular reflex to altered peripheral vestibular inputs. I. Frequency-specific recovery of horizontal VOR after inactivation of the lateral semicircular canals

    NASA Technical Reports Server (NTRS)

    Angelaki, D. E.; Hess, B. J.; Arai, Y.; Suzuki, J.

    1996-01-01

    1. The adaptive plasticity of the vestibuloocular reflex (VOR) following a selective lesion of the peripheral vestibular organs was investigated in rhesus monkeys whose lateral semicircular canals were inactivated by plugging of the canal lumen in both ears. Gain and phase of horizontal, vertical, and torsional slow-phase eye velocity were determined from three-dimensional eye movement recordings obtained acutely after the plugging operation, as well as in regular intervals up to 10 mo later. 2. Acutely after plugging, horizontal VOR was minimal during yaw rotation with gains of < 0.1 at all frequencies. Horizontal VOR gain gradually increased over time, reaching gains of 0.4-0.5 for yaw oscillations at 1.1 Hz approximately 5 mo after lateral canal inactivation. This response recovery was strongly frequency dependent: horizontal VOR gains were largest at the highest frequency tested and progressively decreased for lower frequencies. Below approximately 0.1 Hz, no consistent horizontal VOR could be elicited even 10 mo after plugging. 3. The frequency-dependent changes in gain paralleled changes in horizontal VOR phase. Below approximately 0.1-0.05 Hz large phase leads were present, similarly as in semicircular canal primary afferents. Smaller phase leads were also present at higher frequencies, particularly at 1.1 Hz (the highest frequency tested). 4. Consistent with the afferent-like dynamics of the adapted horizontal VOR, per- and postrotatory horizontal responses to constant-velocity yaw rotations were short lasting. Time constants of the slow-phase eye velocity envelope of the horizontal postrotatory nystagmus were approximately 2 s. Nonetheless, a consistent horizontal optokinetic afternystagmus was evoked in plugged animals. 5. A torsional component that was absent in intact animals was consistently present during yaw rotation acutely after lateral canal inactivation and remained approximately constant thereafter. The frequency response characteristics of this

  8. [Visual tracking with/without passive whole-body rotation in Parkinson's disease (PD): Dissociation of smooth-pursuit and cancellation of vestibulo-ocular reflex (VOR)].

    PubMed

    Ito, Norie; Takei, Hidetoshi; Chiba, Susumu; Inoue, Kiyoharu; Fukushima, Kikuro

    2016-01-01

    Although impaired smooth-pursuit in Parkinson's disease (PD) is well known, reports are conflicting on the ability to cancel vestibulo-ocular reflex (VOR) when the target moves with head, requiring gaze-pursuit. To compare visual tracking performance with or without passive whole-body rotation, we examined eye movements of 10 PD patients and 6 age-matched controls during sinusoidal horizontal smooth-pursuit and passive whole-body rotation (0.3 Hz, ± 10°). Three tasks were tested: smooth-pursuit, VOR cancellation, and VORx1 while subjects fixated an earth-stationary spot during whole-body rotation. Mean ± SD eye velocity gains (eye velocities/stimulus velocities) of PD patients during the 3 tasks were 0.32 ± 0.24 0.25 ± 0.22, 0.85 ± 0.20, whereas those of controls were 0.91 ± 0.06, 0.14 ± 0.07, 0.94 ± 0.05, respectively. Difference was significant between the two subject groups only during smooth-pursuit. Plotting eye-velocity gains of individual subjects during VOR cancellation against those during smooth-pursuit revealed significant negative linear correlation between the two parameters in the controls, but no correlation was found in PD patients. Based on the regression equation of the controls, we estimated expected eye velocity gains of individual subjects during VOR cancellation from their smooth-pursuit gains. Estimated gains of PD patients during VOR cancellation were significantly different from their actual gains, suggesting that different neural mechanisms operate during VOR cancellation in the controls and PD.

  9. [Visual tracking with/without passive whole-body rotation in Parkinson's disease (PD): Dissociation of smooth-pursuit and cancellation of vestibulo-ocular reflex (VOR)].

    PubMed

    Ito, Norie; Takei, Hidetoshi; Chiba, Susumu; Inoue, Kiyoharu; Fukushima, Kikuro

    2016-01-01

    Although impaired smooth-pursuit in Parkinson's disease (PD) is well known, reports are conflicting on the ability to cancel vestibulo-ocular reflex (VOR) when the target moves with head, requiring gaze-pursuit. To compare visual tracking performance with or without passive whole-body rotation, we examined eye movements of 10 PD patients and 6 age-matched controls during sinusoidal horizontal smooth-pursuit and passive whole-body rotation (0.3 Hz, ± 10°). Three tasks were tested: smooth-pursuit, VOR cancellation, and VORx1 while subjects fixated an earth-stationary spot during whole-body rotation. Mean ± SD eye velocity gains (eye velocities/stimulus velocities) of PD patients during the 3 tasks were 0.32 ± 0.24 0.25 ± 0.22, 0.85 ± 0.20, whereas those of controls were 0.91 ± 0.06, 0.14 ± 0.07, 0.94 ± 0.05, respectively. Difference was significant between the two subject groups only during smooth-pursuit. Plotting eye-velocity gains of individual subjects during VOR cancellation against those during smooth-pursuit revealed significant negative linear correlation between the two parameters in the controls, but no correlation was found in PD patients. Based on the regression equation of the controls, we estimated expected eye velocity gains of individual subjects during VOR cancellation from their smooth-pursuit gains. Estimated gains of PD patients during VOR cancellation were significantly different from their actual gains, suggesting that different neural mechanisms operate during VOR cancellation in the controls and PD. PMID:26912226

  10. 75 FR 47709 - Amendment of VOR Federal Airways V-8, V-14, V-38, V-47, V-279, and V-422 in the Vicinity of...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-08-09

    ... a ``significant rule'' under DOT Regulatory Policies and Procedures (44 FR 11034; February 26, 1979... U.S.C. 106(g), 40103, 40113, 40120; E.O. 10854, 24 FR 9565, 3 CFR, 1959-1963 Comp., p. 389. ] Sec... Federal Aviation Administration 14 CFR Part 71 RIN 2120-AA66 Amendment of VOR Federal Airways V-8, V-14,...

  11. Experiment K-7-30: Effects of Spaceflight in the Cosmos Biosatellite 2044 on the Vestibular-Ocular Reflex (VOR) of Rhesus Monkeys

    NASA Technical Reports Server (NTRS)

    Cohen, B.; Cohen, N.; Helwig, D.; Solomon, D.; Kozlovskaya, I.; Sirota, M.; Yakushin, S.; Raphan, T.

    1994-01-01

    This technical paper discusses the following: (1) The VOR of two rhesus monkeys was studied before and after 14 days of spaceflight to determine effects of microgravity on the VOR. Horizontal, vertical and roll eye movements were recorded in these and six other monkeys implanted with scleral search coils. Animals were rotated about a vertical axis to determine the gain of the horizontal, vertical and roll VOR. They were rotated about axes tilted from the vertical (off-vertical axis rotation, OVAR) to determine steady state gains and effects of gravity on modulations in eye position and eye velocity. They were also tested for tilt dumping of post-rotatory nystagmus. (2) The gain of the horizontal VOR was close to unity when animals were tested 15 and 18 hours after flight. VOR gain values were similar to those registered before flight. If the gain of the horizontal VOR changes in microgravity, it must revert to normal soon after landing. (3) Steady state velocities of nystagmus induced by off-vertical axis rotation (OVAR) were unchanged by adaptation to microgravity, and the phase of the modulations was similar before and after flight. However, modulations in horizontal eye velocity had more variation after landing and were on mean about 50% larger for angles of tilt of the axis of rotation between 50 and 90?/s after flight. This difference was similar in both animals and was significant. (4) A striking finding was that tilt dumping was lost in the one animal tested for this function. This loss persisted for several days after return. This is reminiscent of the loss of response to pitch while rotating in the M-131 experiments of Skylab, and must be studied in detail in future spaceflights. (5) Thus, two major findings emerged from these studies: after spaceflight the modulation of horizontal eye velocity was larger during OVAR, and one animal lost its ability to tilt-dump its nystagmus. Both findings are consistent with the postulate that adaptation to microgravity

  12. The complete genome sequence and analysis of vB_VorS-PVo5, a Vibrio phage infectious to the pathogenic bacterium Vibrio ordalii ATCC-33509.

    PubMed

    Echeverría-Vega, Alex; Morales-Vicencio, Pablo; Saez-Saavedra, Camila; Ceh, Janja; Araya, Rubén

    2016-01-01

    The bacterium Vibrio ordalii is best known as the causative agent of vibriosis outbreaks in fish and thus recognized for generating serious production losses in aquaculture systems. Here we report for the first time on the isolation and the genome sequencing of phage vB_VorS-PVo5, infectious to Vibrio ordalii ATCC 33509. The features as well as the complete genome sequence and annotation of the Vibrio phage are described; vB_VorS-PVo5 consists of a lineal double stranded DNA totaling ~ 80.6 Kb in length. Considering its ability to lyse Vibrio ordalii ATCC 33509, the phage is likely to gain importance in future aquaculture applications by controlling the pathogen and as such replacing antibiotics as the treatment of choice. PMID:27382430

  13. Model simulation studies to clarify the effect on saccadic eye movements of initial condition velocities set by the Vestibular Ocular Reflex (VOR)

    NASA Technical Reports Server (NTRS)

    Nam, M. H.; Winters, J. M.; Stark, L.

    1981-01-01

    Voluntary active head rotations produced vestibulo-ocular reflex eye movements (VOR) with the subject viewing a fixation target. When this target jumped, the size of the refixation saccades were a function of the ongoing initial velocity of the eye. Saccades made against the VOR were larger in magnitude. Simulation of a reciprocally innervated model eye movement provided results comparable to the experimental data. Most of the experimental effect appeared to be due to linear summation for saccades of 5 and 10 degree magnitude. For small saccades of 2.5 degrees, peripheral nonlinear interaction of state variables in the neuromuscular plant also played a role as proven by comparable behavior in the simulated model with known controller signals.

  14. Loss of α-calcitonin gene-related peptide (αCGRP) reduces the efficacy of the Vestibulo-ocular Reflex (VOR).

    PubMed

    Luebke, Anne E; Holt, Joseph C; Jordan, Paivi M; Wong, Yi Shan; Caldwell, Jillian S; Cullen, Kathleen E

    2014-07-30

    The neuroactive peptide calcitonin-gene related peptide (CGRP) is known to act at efferent synapses and their targets in hair cell organs, including the cochlea and lateral line. CGRP is also expressed in vestibular efferent neurons as well as a number of central vestibular neurons. Although CGRP-null (-/-) mice demonstrate a significant reduction in cochlear nerve sound-evoked activity compared with wild-type mice, it is unknown whether and how the loss of CGRP influence vestibular system function. Vestibular function was assessed by quantifying the vestibulo-ocular reflex (VOR) in alert mice. The loss of CGRP in (-/-) mice was associated with a reduction of the VOR gain of ≈50% without a concomitant change in phase. Using immunohistochemistry, we confirmed that, although CGRP staining was absent in the vestibular end-organs of null (-/-) mice, cholinergic staining appeared normal, suggesting that the overall gross development of vestibular efferent innervation was unaltered. We further confirmed that the observed deficit in vestibular function of null (-/-) mice was not the result of nontargeted effects at the level of the extraocular motor neurons and/or their innervation of extraocular muscles. Analysis of the relationship between vestibular quick phase amplitude and peak velocity revealed that extraocular motor function was unchanged, and immunohistochemistry revealed no abnormalities in motor endplates. Together, our findings show that the neurotransmitter CGRP plays a key role in ensuring VOR efficacy.

  15. Loss of α-Calcitonin Gene-Related Peptide (αCGRP) Reduces the Efficacy of the Vestibulo-ocular Reflex (VOR)

    PubMed Central

    Holt, Joseph C.; Jordan, Paivi M.; Wong, Yi Shan; Caldwell, Jillian S.; Cullen, Kathleen E.

    2014-01-01

    The neuroactive peptide calcitonin-gene related peptide (CGRP) is known to act at efferent synapses and their targets in hair cell organs, including the cochlea and lateral line. CGRP is also expressed in vestibular efferent neurons as well as a number of central vestibular neurons. Although CGRP-null (−/−) mice demonstrate a significant reduction in cochlear nerve sound-evoked activity compared with wild-type mice, it is unknown whether and how the loss of CGRP influence vestibular system function. Vestibular function was assessed by quantifying the vestibulo-ocular reflex (VOR) in alert mice. The loss of CGRP in (−/−) mice was associated with a reduction of the VOR gain of ≈50% without a concomitant change in phase. Using immunohistochemistry, we confirmed that, although CGRP staining was absent in the vestibular end-organs of null (−/−) mice, cholinergic staining appeared normal, suggesting that the overall gross development of vestibular efferent innervation was unaltered. We further confirmed that the observed deficit in vestibular function of null (−/−) mice was not the result of nontargeted effects at the level of the extraocular motor neurons and/or their innervation of extraocular muscles. Analysis of the relationship between vestibular quick phase amplitude and peak velocity revealed that extraocular motor function was unchanged, and immunohistochemistry revealed no abnormalities in motor endplates. Together, our findings show that the neurotransmitter CGRP plays a key role in ensuring VOR efficacy. PMID:25080603

  16. Kafka's "Vor dem Gesetz": The Case for an Integrated Approach

    ERIC Educational Resources Information Center

    Pickar, Gertrud Bauer

    1975-01-01

    Uses a parable from a Kafka novel to illustrate and support the premise that language and literature study should be integrated, even in the early stages. Reading short literary works can explain involved language problems better than long explanations, and can also stimulate further literary study. (CHK)

  17. 77 FR 62468 - Proposed Amendment of VOR Federal Airway V-537, GA

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-10-15

    ... traffic within the National Airspace System. Environmental Review This proposal will be subject to an... regulatory, aeronautical, economic, environmental, and energy-related aspects of the proposal. Communications..., for a copy of Advisory Circular No. 11-2A, Notice of Proposed Rulemaking Distribution System,...

  18. 75 FR 54058 - Proposed Revocation of VOR Federal Airway V-284; New Jersey

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-09-03

    ... efficient flow of air traffic within the National Airspace System. Environmental Review The FAA has... INFORMATION CONTACT: Paul Gallant, Airspace and Rules Group, Office of System Operations Airspace and AIM... regulatory, aeronautical, economic, environmental, and energy-related aspects of the proposal....

  19. Frequency response of the vestibulo-ocular reflex /VOR/ in the monkey

    NASA Technical Reports Server (NTRS)

    Buettner, U. W.; Henn, V.; Young, L. R.

    1981-01-01

    The frequency response of the vestibulo-ocular reflex has been investigated in the alert monkey during sinusoidal rotation about a vertical axis in a frequency range of 0.001-0.5 Hz. Phase and gain of nystagmus slow phase velocity was determined. In the frequency range above 0.1 Hz, nystagmus slow phase velocity was in phase with (compensated for) head velocity. At lower frequencies, an increasing phase lead was present which could reach more than 90 deg. Gain fell off correspondingly at low frequencies. Calculated time constants were 10-40 s in different monkeys. Animals which had been exposed to numerous previous rotary stimuli in the laboratory showed much shorter time constants than did 'native' monkeys.

  20. The bedside examination of the vestibulo-ocular reflex (VOR): an update.

    PubMed

    Kheradmand, A; Zee, D S

    2012-10-01

    Diagnosing dizzy patients remains a daunting challenge to the clinician in spite of modern imaging and increasingly sophisticated electrophysiological testing. Here we review the major bedside tests of the vestibulo-ocular reflex and how, when combined with a proper examination of the other eye movement systems, one can arrive at an accurate vestibular diagnosis.

  1. 78 FR 2200 - Establishment of VOR Federal Airway V-629; Las Vegas, NV

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-01-10

    ..., NV. (77 FR 54859). Interested parties were invited to participate in this rulemaking effort by... and Procedures (44 FR 11034; February 26, 1979); and (3) does not warrant preparation of a regulatory..., 40120; E.O. 10854, 24 FR 9565, 3 CFR, 1959-1963 Comp., p.389. Sec. 71.1 0 2. The incorporation...

  2. 77 FR 54859 - Proposed Establishment of VOR Federal Airway V-629; Las Vegas, NV

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-09-06

    ... and Procedures (44 FR 11034; February 26, 1979); and (3) does not warrant preparation of a regulatory..., 40120; E.O. 10854, 24 FR 9565, 3 CFR, 1959-1963 Comp., p. 389. Sec. 71.1 2. The incorporation by... of marginal radar coverage. This would enhance the efficiency of the National Airspace System...

  3. 78 FR 72005 - Amendment of VOR Federal Airway V-45, North Carolina

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-12-02

    ... Procedures (44 FR 11034; February 26, 1979); and (3) does not warrant preparation of a Regulatory Evaluation... FR 9565, 3 CFR, 1959-1963 Comp., p. 389. Sec. 71.1 0 2. The incorporation by reference in 14 CFR 71.1... with standard formatting for describing routes and does not alter the alignment of the airway....

  4. 77 FR 42428 - Amendment of Jet Routes and VOR Federal Airways; Northeastern United States

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-07-19

    ... Pendleton, OR; Whitehall, MT; Billings, MT; Dupree, SD; Sioux Falls, SD; Mason City, IA; Badger, WI; Peck... Executive Order 12866; (2) is not a ``significant rule'' under DOT Regulatory Policies and Procedures (44 FR... follows: Authority: 49 U.S.C. 106(g), 40103, 40113, 40120; E.O. 10854, 24 FR 9565, 3 CFR, 1959-1963...

  5. D Extention of the Vor Algorithm to Determine and Optimize the Coverage of Geosensor Networks

    NASA Astrophysics Data System (ADS)

    Doodman, S.; Afghantoloee, A.; Mostafavi, M. A.; Karimipour, F.

    2014-10-01

    Recent advances in electrical, mechanical and communication systems have led to development of efficient low-cost and multi-function geosensor networks. The efficiency of a geosensor network is significantly based on network coverage, which is the result of network deployment. Several optimization methods have been proposed to enhance the deployment efficiency and hence increase the coverage, but most of them considered the problem in the 2D environment models, which is usually far from the real situation. This paper extends a Voronoi-based deployment algorithm to 3D environment, which takes the 3D features into account. The proposed approach is applied on two case studies whose results are evaluated and discussed.

  6. 78 FR 41686 - Modification of VOR Federal Airway V-345 in the Vicinity of Ashland, WI

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-07-11

    ... modify V-345 in the vicinity of Ashland, WI (78 FR 18271). Interested parties were invited to participate... Procedures (44 FR 11034; February 26, 1979); and (3) does not warrant preparation of a regulatory evaluation..., 40120; E.O. 10854, 24 FR 9565, 3 CFR, 1959-1963 Comp., p. 389. Sec. 71.1 0 2. The incorporation...

  7. Hydraulische Leitfähigkeiten von Sedimentwürfeln vor und nach einem gefrorenen Zustand

    NASA Astrophysics Data System (ADS)

    Vaitl, Tobias; Gökpinar, Thorsten; Englert, Andreas

    2014-09-01

    To study flow and transport processes in heterogeneous porous media, frozen sediment cubes that were assembled in sandbox experiments may represent a viable procedure. In this investigation, it was important to find out how flow and transport properties would be modified by sediment freezing. In this study, a medium sand, a coarse sand and a fine gravel were investigated to find out to what extent the hydraulic conductivities might change before and after freezing. For this purpose, a cubic Darcy-cell was developed. The results of the study show that it is possible to produce 10 × 10 × 10 cm frozen sediment cubes with the presented apparatus. The study also suggests that freezing and subsequent thawing only caused small changes in hydraulic conductivity of the investigated sediments.

  8. Fremdsprachliche Moglichkeiten vor der "eigenen Haustur" (Foreign Language Possibilities at One's Own Doorstep)

    ERIC Educational Resources Information Center

    Zydatiss, Wolfgang

    1973-01-01

    Describes an instructional project, How to Tell a Foreigner to Berlin the Way,'' designed to give 8th graders practical experience in using English; format based on the text London--People ans Pictures,'' Cornelsen-Velhagen & Klasing, Berlin. (RS)

  9. 77 FR 23113 - Modification of VOR Federal Airways V-135 and V-137; Southwest United States

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-04-18

    ...., Washington, DC 20591; telephone: (202) 267-8783. SUPPLEMENTARY INFORMATION: History On December 21, 2011, the... in the southwest United States (76 FR 79140). Interested parties were invited to participate in this... Transportation (DOT) Regulatory Policies and Procedures (44 FR 11034; February 26, 1979); and (3) does...

  10. 78 FR 18232 - Amendment of VOR Federal Airway V-233, Springfield, IL

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-03-26

    ...., Washington, DC 20591; telephone: (202) 267-8783. SUPPLEMENTARY INFORMATION: History After a recent review of... depiction of the airway. When V- 233 was amended in the Federal Register of August 8, 2005 (70 FR 45527... Department of Transportation (DOT) Regulatory Policies and Procedures (44 FR 11034; February 26, 1979);...

  11. 77 FR 71493 - Amendment of VOR Federal Airway V-8 in the Vicinity of Rifle, CO

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-12-03

    ...., Washington, DC 20591; telephone: (202) 267-8783. SUPPLEMENTARY INFORMATION: History After a recent review of.... When V-8 was amended in the Federal Register of September 30, 1993 (58 FR 51010), the airway was... aid between Grand Junction, CO, and Kremmling, CO. In the Federal Register of August 9, 2010 (75...

  12. 75 FR 39149 - Establishment of VOR Federal Airway V-625; Arizona

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-07-08

    ..., SW., Washington, DC 20591; telephone: (202) 267-8783. History On April 20, 2009, the FAA published in... Arizona, (74 FR 17911). Interested parties were invited to participate in this rulemaking effort by... ``significant rule'' under Department of Transportation (DOT) Regulatory Policies and Procedures (44 FR...

  13. 14 CFR 91.171 - VOR equipment check for IFR operations.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... checked within the preceding 30 days, and was found to be within the limits of the permissible indicated... permissible indicated bearing error is plus or minus 4 degrees); or (2) Use, at the airport of intended... minus 4 degrees); (3) If neither a test signal nor a designated checkpoint on the surface is...

  14. 76 FR 13083 - Amendment to VOR Federal Airway V-358; TX

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-03-10

    ... Federal Register amending thirteen Federal airways in the vicinity of Dallas/ Fort Worth, TX (65 FR 61087... (66 FR 50101). The realignment around P-49 was necessary to assist the United States Secret Service in... in the Federal Register amending the V-358 airway description (74 FR 54896). That rule renamed...

  15. Die Keplersche Supernova - Entdeckung vor 400 Jahren [Kepler's supernova: its discovery 400 years ago

    NASA Astrophysics Data System (ADS)

    Posch, Thomas; Maitzen, Hans Michael

    2004-10-01

    We summarize the early observations of SN 1604 made by Johannes Brunowsky and Johannes Kepler in Prague in October 1604. Quoting from Kepler's two books on this subject ("Gründlicher Bericht" and "De stella nova"), we point out that he compared the supernova with respect to its twinkling with an "exquisite multifaceted diamond" and that he thought this object to be rather something like a newly born (proto-)star than a star in its final phase of evolution, as we would call it today. The twinkling of the star was interpreted by Kepler as intrinsic to it rather than an effect of the Earth's atmosphere.

  16. 78 FR 37105 - Modification of VOR Federal Airway V-537, GA

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-06-20

    ... Georgia (77 FR 62468). Interested parties were invited to participate in this rulemaking effort by... (SNPRM) (78 FR 21856, April 12, 2013) to reopen the comment period and solicit comments on the proposed... Department of Transportation (DOT) Regulatory Policies and Procedures (44 FR 11034; February 26, 1979);...

  17. 76 FR 61257 - Amendment to Description of VOR Federal Airway V-299; CA

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-10-04

    ...-2520. See (52 FR 5947; February 27, 1987). The exclusionary wording had previously been included in the description of V-299 (45 FR 335; January 2, 1980). The Rule This action amends Title 14 Code of Federal... Policies and Procedures (44 FR 11034; February 26, 1979); and (3) does not warrant preparation of...

  18. Der Physik-Nobelpreis vor 100 Jahren Die Entdeckung des trägen Gases

    NASA Astrophysics Data System (ADS)

    Jacobi, Manfred

    2004-11-01

    Im Jahr 1904 erhielt der britische Physiker Lord Rayleigh (John William Strutt, 1842 bis 1919) den Nobelpreis für seine Untersuchungen über die Dichte von Gasen und die Entdeckung des Edelgases Argon.

  19. 78 FR 72005 - Amendment of VOR Federal Airway V-374, Northeastern United States

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-12-02

    ... ``significant rule'' under DOT Regulatory Policies and Procedures (44 FR 11034; February 26, 1979); and (3) does... FR 9565, 3 CFR, 1959-1963 Comp., p. 389. Sec. 71.1 0 2. The incorporation by reference in 14 CFR 71.1... radials; INT Calverton 044 and Groton, CT, 276 radials; Groton; to Martha's Vineyard, MA. Issued...

  20. Sterblichkeit: der paradoxe Kunstgriff des Lebens - Eine Betrachtung vor dem Hintergrund der modernen Biologie

    NASA Astrophysics Data System (ADS)

    Verbeek, Bernhard

    Leben gibt es auf der Erde seit fast 4 Mio. Jahren, trotz allen Katastrophen. Die Idee des Lebens scheint unsterblich. Der Tod aber offenbar auch. Jedes Lebewesen ist davon bedroht, ja für Menschen und andere "höhere“ Lebewesen ist er im Lebensprogramm eingebaut - todsicher. Diese Tatsache ist alles andere als selbstverständlich. Ist sie überhaupt kompatibel mit dem Prinzip der Evolution, nach dem der am besten Angepasste überlebt?

  1. Gain, phase and frequency stability of DSS-42 and DSS-43 vor Voyage Uranus encounter

    NASA Technical Reports Server (NTRS)

    Cha, A. G.; Levy, R.

    1986-01-01

    Theoretically rigorous definitions are derived of such parameters as RF signal path length, phase delay, and phase/frequency stability in a Cassegrainian antenna applicable to a narrow bandwidth channel, as well as algorithms for evaluating these parameters. This work was performed in support of the Voyager spacecraft encounter with Uranus in January 1986. The information was needed to provide Voyager/Uranus radio science researchers with a rotational basis for deciding the best strategy to operate the three antennas involved during the crucial 5-hour occultation period of the encounter. Such recommendations are made at the end of the article.

  2. 76 FR 68674 - Proposed Amendment of VOR Federal Airways V-320 and V-440; Alaska

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-11-07

    ... necessary for the continued safe and efficient management of Instrument Flight Rules (IFR) operations within... and Airspace Docket No. 11-AAL-19) and be submitted in triplicate to the Docket Management Facility.... 11-AAL-1 published on April 28, 2011 (76 FR 23687), that amends all Alaska Federal Airways...

  3. 78 FR 1751 - Modification of VOR Federal Airway V-170 in the Vicinity of Devils Lake, ND

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-01-09

    ...-radar separation and airway clearance from the newly established R-5402, Devils Lake, ND (77 FR 54860... (44 FR 11034; February 26, 1979); and (3) does not warrant preparation of a regulatory evaluation as.... 10854, 24 FR 9565, 3 CFR, 1959-1963 Comp., p. 389. Sec. 71.1 0 2. The incorporation by reference in...

  4. 76 FR 79140 - Proposed Modification of VOR Federal Airways V-135 and V-137; Southwest United States

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-12-21

    ...'' under Department of Transportation (DOT) Regulatory Policies and Procedures (44 FR 11034; February 26... read as follows: Authority: 49 U.S.C. 106(g), 40103, 40113, 40120; E.O. 10854, 24 FR 9565, 3 CFR, 1959... V-135 and V-137; Southwest United States AGENCY: Federal Aviation Administration (FAA), DOT....

  5. 76 FR 20835 - Amendment of VOR Federal Airways V-1, V-7, V-11 and V-20; Kona, HI

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-04-14

    ... flight inspection. DATES: The effective date of FR Doc. 2011-5078, published on March 10, 2011 (76 FR...: Background Airspace Docket No. 10-AWP-20, published in the Federal Register on March 10, 2011, (76 FR 13082...; (2) is not a ``significant rule'' under DOT Regulatory Policies and Procedures (44 FR 11034;...

  6. 76 FR 13082 - Amendment of VOR Federal Airways V-1, V-7, V-11 and V-20; Kona, HI

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-03-10

    ... and Procedures (44 FR 11034; February 26, 1979); and (3) does not warrant preparation of a regulatory..., 40113, 40120; E.O. 10854, 24 FR 9565, 3 CFR, 1959-1963 Comp., p. 389. Sec. 71.1 0 2. The incorporation...-11 and V-20; Kona, HI AGENCY: Federal Aviation Administration (FAA), DOT. ACTION: Final rule....

  7. 78 FR 18271 - Proposed Modification of VOR Federal Airway V-345 in the Vicinity of Ashland, WI

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-03-26

    ... Policies and Procedures (44 FR 11034; February 26, 1979); and (3) does not warrant preparation of a... read as follows: Authority: 49 U.S.C. 106(g), 40103, 40113, 40120; E.O. 10854, 24 FR 9565, 3 CFR, 1959... out of service for over ten months, with a Notice to Airmen (NOTAM) published, and is scheduled to...

  8. 75 FR 12674 - Amendment of Jet Routes and VOR Federal Airways in the Vicinity of Gage, OK

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-03-17

    ... Procedures (44 FR 11034; February 26, 1979); and (3) does not warrant preparation of a Regulatory Evaluation... continues to read as follows: Authority: 49 U.S.C. 106(g), 40103, 40113, 40120; E.O. 10854, 24 FR 9565, 3..., is being renamed the Mitbee VORTAC for identity clarification. DATES: Effective date 0901 UTC, June...

  9. 77 FR 54860 - Proposed Modification of VOR Federal Airway V-170 in the Vicinity of Devils Lake, ND

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-09-06

    ...'' under Department of Transportation (DOT) Regulatory Policies and Procedures (44 FR 11034; February 26.... 106(g), 40103, 40113, 40120; E.O. 10854, 24 FR 9565, 3 CFR, 1959-1963 Comp., p. 389. Sec. 71.1 2. The... boundary of R- 5402, established for hazardous laser training activities, in support of...

  10. 75 FR 43818 - Amendment of VOR Federal Airways V-50, V-251, and V-313 in the Vicinity of Decatur, IL

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-07-27

    ... Regulatory Policies and Procedures (44 FR 11034; February 26, 1979); and (3) does not warrant preparation of.... 10854, 24 FR 9565, 3 CFR, 1959-1963 Comp., p. 389. Sec. 71.1 0 2. The incorporation by reference in...

  11. Warum kommt hier NICHT nicht vor? - Regularitaeten beim L-2-Erwerb (Why Is "Nicht" Not Used Here? Regularities in Second Language Acquisition).

    ERIC Educational Resources Information Center

    Stalb, Heinrich

    1978-01-01

    Presents a German test for English students. Errors in the placing of "nicht" are examined and categorized. Criticism of the objectivity of the findings are examined. The tests are seen as a measure of oral skills. Study is recommended of how to present most economically the various items. (IFS/WGA)

  12. 78 FR 19985 - Modification of VOR Federal Airways V-68, V-76, V-194, and V-548 in the Vicinity of Houston, TX

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-04-03

    ... published in FAA Order 7400.9W (77 FR 50907, August 23, 2012), the FAA is amending the V-68, V-76, V-194... Transportation (DOT) Regulatory Policies and Procedures (44 FR 11034; February 26, 1979); and (3) does not... follows: Authority: 49 U.S.C. 106(g), 40103, 40113, 40120; E.O. 10854, 24 FR 9565, 3 CFR, 1959-1963...

  13. 77 FR 42625 - Modification of VOR Federal Airways V-10, V-12, and V-508 in the Vicinity of Olathe, KS

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-07-20

    ...-508, in the vicinity of Olathe, KS (77 FR 9876), due to the planned decommissioning of the Johnson... and Procedures (44 FR 11034; February 26, 1979); and (3) does not warrant preparation of a regulatory.... 106(g), 40103, 40113, 40120; E.O. 10854, 24 FR 9565, 3 CFR, 1959-1963 Comp., p. 389. Sec. 71.1 0...

  14. 77 FR 9876 - Proposed Modification of VOR Federal Airways V-10, V-12, and V-508 in the Vicinity of Olathe, KS

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-02-21

    ... Department of Transportation (DOT) Regulatory Policies and Procedures (44 FR 11034; February 26, 1979); and.... 106(g), 40103, 40113, 40120; E.O. 10854, 24 FR 9565, 3 CFR, 1959-1963 Comp., p. 389. Sec. 71.1 2. The... route segments in the vicinity of Olathe, KS, between Emporia, KS, and Napoleon, MO, unchanged....

  15. 75 FR 43813 - Modification of VOR Federal Airways V-82, V-175, V-191, and V-430 in the Vicinity of Bemidji, MN

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-07-27

    ... modify V-82, V-175, V-191, and V-430 in the vicinity of Bemidji, MN (75 FR 24504). Interested parties... Procedures (44 FR 11034; February 26, 1979); and (3) does not warrant preparation of a regulatory evaluation...: Authority: 49 U.S.C. 106(g), 40103, 40113, 40120; E.O. 10854, 24 FR 9565, 3 CFR, 1959-1963 Comp., p.389....

  16. 75 FR 24504 - Proposed Modification of VOR Federal Airways V-82, V-175, V-191, and V-430 in the Vicinity of...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-05-05

    ... Department of Transportation (DOT) Regulatory Policies and Procedures (44 FR 11034; February 26, 1979); and..., 40120; E.O. 10854, 24 FR 9565, 3 CFR, 1959-1963 Comp., p. 389. Sec. 71.1 2. The incorporation by... these airways has been out of service for over two years due to terrain and new construction...

  17. Die Biomasse mariner Makrobenthos-Gesellschaften im Einflußbereich der Klärschlammverklappung vor der Elbemündung

    NASA Astrophysics Data System (ADS)

    Mühlenhardt-Siegel, U.

    1981-12-01

    The macrofauna of a dumping area in the eastern part of the German Bight (North Sea) was investigated in July, August and November, 1978 at five stations situated on a transect including central and peripheral areas of the dumping region. Abundance and biomass (ash free dry weight) of the macrofauna and its variation from July to November were analysed as well as the biomass of different taxa. Molluscs dominated over polychaetes, crustaceans and echinoderms. A positive correlation seemed to exist between mud content and biomass at the peripherally situated stations. In the central sewage sludge area, however, the biomass values were reduced. In late autumn the biomass decreased in the entire area due to the death of Diastylis rathkei, Abra alba and Pectinaria koreni. These species were replaced by the mollusc Nucula turgida and polychaete Nephtys hombergii. In autumn the biomass values also showed a distinct minimum at the central stations.

  18. "Onkle Karl" aus Milwaukee: Deutsch-amerikanische Einwandererkultur im Spiegel der Jugendliteratur vor hundert Jahren (Uncle Carl from Milwaukee: German-American Newcomer Culture Reflected in Children's Literature a Hundred Years Ago).

    ERIC Educational Resources Information Center

    Weiss, Gerhard

    1998-01-01

    Examines a late nineteenth-century Milwaukee (Wisconsin) publication for children and young people as a reflection of German-American middle-class culture of the time, showing how the spirit of the 1848 revolution and the experience of the American Civil War shaped German-American intellectuals and how the ideals of freedom and equality dominated…

  19. Curved spaces before Einstein: Karl Schwarzschild's cosmological speculations and the beginnings of relativistic cosmology (German Title: Gekrümmte Universen vor Einstein: Karl Schwarzschilds kosmologische Spekulationen und die Anfänge der relativistischen Kosmologie)

    NASA Astrophysics Data System (ADS)

    Schemmel, Matthias

    In contrast to most of his collegues in astronomy and physics, the German astronomer Karl Schwarzschild immediately recognized the significance of general relativity for physics and astronomy, and played a pioneering role in its early development. In this contribution, it is argued that the clue for understanding Schwarzschild's exceptional reaction to general relativity lies in the study of his prerelativistic work. Long before the rise of general relativity, Schwarzschild occupied himself with foundational problems on the borderline of physics, astronomy, and mathematics that, from today's perspective, belong to the field of problems of that theory. In this contribution, the example of Schwarzschild's early speculations about the non-Euclidean nature of physical space on cosmological scales is presented and their reflection in his reception of general relativity is discussed.

  20. 14 CFR 171.3 - Requests for IFR procedure.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ...) NAVIGATIONAL FACILITIES NON-FEDERAL NAVIGATION FACILITIES VOR Facilities § 171.3 Requests for IFR procedure. (a) Each person who requests an IFR procedure based on a VOR facility that he owns must submit...

  1. 14 CFR 171.13 - Reports.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... FACILITIES NON-FEDERAL NAVIGATION FACILITIES VOR Facilities § 171.13 Reports. The owner of each facility to... the appropriate Regional office of the FAA. (d) (e) VOR ground check error data (Forms FAA-2396...

  2. 14 CFR 171.1 - Scope.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... NON-FEDERAL NAVIGATION FACILITIES VOR Facilities § 171.1 Scope. This subpart sets forth minimum requirements for the approval and operation on non-Federal VOR facilities that are to be involved in...

  3. 14 CFR 171.5 - Minimum requirements for approval.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... (CONTINUED) NAVIGATIONAL FACILITIES NON-FEDERAL NAVIGATION FACILITIES VOR Facilities § 171.5 Minimum... approve an IFR procedure for a non-Federal VOR: (1) The facility's performance, as determined by air...

  4. 76 FR 21234 - Standard Instrument Approach Procedures, and Takeoff Minimums and Obstacle Departure Procedures...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-04-15

    ... Policies and Procedures (44 FR 11034; February 26, 1979); and (3) does not warrant preparation of a....25, 97.27, 97.29, 97.31, 97.33 and 97.35 By amending: Sec. 97.23 VOR, VOR/DME, VOR or TACAN, and VOR... ILS, ILS/DME, MLS, MLS/DME, MLS/RNAV; Sec. 97.31 RADAR SIAPs; Sec. 97.33 RNAV SIAPs; and Sec....

  5. 78 FR 7652 - Standard Instrument Approach Procedures, and Takeoff Minimums and Obstacle Departure Procedures...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-02-04

    ... Policies and Procedures (44 FR 11034; February 26, 1979); and (3) does not warrant preparation of a....25, 97.27, 97.29, 97.31, 97.33 and 97.35 By amending: Sec. 97.23 VOR, VOR/DME, VOR or TACAN, and VOR... ILS, ILS/DME, MLS, MLS/DME, MLS/RNAV; Sec. 97.31 RADAR SIAPs; Sec. 97.33 RNAV SIAPs; and Sec....

  6. 76 FR 18381 - Standard Instrument Approach Procedures, and Takeoff Minimums and Obstacle Departure Procedures...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-04-04

    ... Policies and Procedures (44 FR 11034; February 26, 1979); and (3) does not warrant preparation of a....25, 97.27, 97.29, 97.31, 97.33, and 97.35 By amending: Sec. 97.23 VOR, VOR/DME, VOR or TACAN, and VOR... ILS, ILS/DME, MLS, MLS/DME, MLS/RNAV; Sec. 97.31 RADAR SIAPs; Sec. 97.33 RNAV SIAPs; and Sec....

  7. 76 FR 23687 - Amendment of Federal Airways; Alaska

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-04-28

    ...;having general applicability and legal effect, most of which are keyed #0;to and codified in the Code of... proposed rulemaking (NPRM) to amend Federal airways in Alaska, (76 FR 11978). Interested parties were... was upgraded to a Doppler VOR and redesignated as the Anchorage (TED) VOR. The TED VOR was moved...

  8. Costimulation of the horizontal semicircular canal during skull vibrations in superior canal Dehiscence syndrome.

    PubMed

    Park, Joo Hyun; Kim, Hyo Jung; Kim, Ji-Soo; Koo, Ja-Won

    2014-01-01

    A sound- and pressure-induced vestibuloocular reflex (VOR) has been described as vertical and torsional in superior canal dehiscence (SCD), and the rotational axes of induced VOR have been assumed to fit with the axis of the affected superior semicircular canal (SC). However, it has been difficult to characterize the pattern of vibration-induced VOR (ViVOR). We aimed to characterize the pattern of ViVOR by comparing the intensity and the axis of ViVOR with several clinical parameters of SCD. Ten symptomatic SCD patients were recruited. SCD size and location were measured on a reformatted image in the plane of the SC. Unilateral vibratory stimulation (100 Hz) was applied to the mastoid surface. ViVOR were recorded using 3D videooculography. The median 3D velocity of ViVOR was measured and the 3D vector trajectory plotted for reference against the axes of the human semicircular canals. A correlation between the magnitude of ViVOR and the size of SCD was evaluated. We also compared the location of SCD with the vertical-to-torsional component ratio of the ViVOR. ViVOR were present in 7 patients; 6 patients showed a substantial horizontal component in the excitatory direction in addition to strong torsional and weak vertical components. The computed rotational axes of ViVOR were located mostly between the axes of the ipsilateral SC and horizontal canal (HC) with a variable deviation to the axis of the ipsilateral posterior canal (PC). The magnitude of ViVOR was not related to the size of the SCD. The vertical-to-torsional component ratio of ViVOR tended to decline as the dehiscence was closer to the common crus. In SCD, mastoid vibration may stimulate the affected-side HC and PC as well as the SC. SCD can be suspected when excitatory horizontal torsional ViVOR direct to the side of the auditory symptoms.

  9. Oculomotor function during space flight and susceptibility to space motion sickness

    NASA Astrophysics Data System (ADS)

    Thornton, William E.; Uri, John J.

    Horizontal vestibulo-ocular reflex (VOR) and saccadic eye movements (SEM) were studied in 18 subjects before and during five Space Shuttle missions to evaluate the effects of weightlessness and correlations between results and susceptibility to and actual presence of space motion sickness (SMS). Active sinusoidal head oscillation was the stimulus for VOR tests with vision (VVOR), with eyes shaded (VOR-ES), and VOR suppression (VOR-S). Eye movements were recorded by electrooculography and head position by a potentiometer. No pathological nystagmus or other abnormal eye movements were seen. No significant in-flight changes were seen in the gain, phase shift or waveform of VVOR, VOR-ES or VOR-S. Statistically significant increases in saccadic latency and decreases in saccadic velocity were seen, with no change in saccadic accuracy. Preflight differences between SMS susceptible and non-susceptible subjects were noted only in VOR-S, with less complete suppression in susceptible subjects, a finding also seen in flight. During flight, VVOR gain was significantly increased in three non-affected subjects. Saccades of SMS-affected subjects showed increased latency and velocity and decreased accuracy compared to saccades of unaffected subjects.

  10. Chemical and functional properties of fibre concentrates obtained from by-products of coconut kernel.

    PubMed

    Yalegama, L L W C; Nedra Karunaratne, D; Sivakanesan, Ramiah; Jayasekara, Chitrangani

    2013-11-01

    The coconut kernel residues obtained after extraction of coconut milk (MR) and virgin coconut oil (VOR) were analysed for their potential as dietary fibres. VOR was defatted and treated chemically using three solvent systems to isolate coconut cell wall polysaccharides (CCWP). Nutritional composition of VOR, MR and CCWPs indicated that crude fibre, neutral detergent fibre, acid detergent fibre and hemicelluloses contents were higher in CCWPs than in VOR and MR. MR contained a notably higher content of fat than VOR and CCWPs. The oil holding capacity, water holding capacity and swelling capacity were also higher in CCWPs than in VOR and MR. All the isolates and MR and VOR had high metal binding capacities. The CCWPs when compared with commercially available fibre isolates, indicated improved dietary fibre properties. These results show that chemical treatment of coconut kernel by-products can enhance the performance of dietary fibre to yield a better product.

  11. Chemical and functional properties of fibre concentrates obtained from by-products of coconut kernel.

    PubMed

    Yalegama, L L W C; Nedra Karunaratne, D; Sivakanesan, Ramiah; Jayasekara, Chitrangani

    2013-11-01

    The coconut kernel residues obtained after extraction of coconut milk (MR) and virgin coconut oil (VOR) were analysed for their potential as dietary fibres. VOR was defatted and treated chemically using three solvent systems to isolate coconut cell wall polysaccharides (CCWP). Nutritional composition of VOR, MR and CCWPs indicated that crude fibre, neutral detergent fibre, acid detergent fibre and hemicelluloses contents were higher in CCWPs than in VOR and MR. MR contained a notably higher content of fat than VOR and CCWPs. The oil holding capacity, water holding capacity and swelling capacity were also higher in CCWPs than in VOR and MR. All the isolates and MR and VOR had high metal binding capacities. The CCWPs when compared with commercially available fibre isolates, indicated improved dietary fibre properties. These results show that chemical treatment of coconut kernel by-products can enhance the performance of dietary fibre to yield a better product. PMID:23768337

  12. The human vertical translational vestibulo-ocular reflex. Normal and abnormal responses.

    PubMed

    Liao, Ke; Walker, Mark F; Joshi, Anand; Reschke, Millard; Strupp, Michael; Leigh, R John

    2009-05-01

    Geometric considerations indicate that the human translational vestibulo-ocular reflex (tVOR) should have substantially different properties than the angular vestibulo-ocular reflex (aVOR). Specifically, tVOR cannot simultaneously stabilize images of distant and near objects on the retina. Most studies make the tacit assumption that tVOR acts to stabilize foveal images even though, in humans, tVOR is reported to compensate for less than 60% of foveal image motion. We have determined that the compensation gain (eye rotational velocity/required eye rotational velocity to maintain foveal target fixation) of tVOR is held steady at approximately 0.6 during viewing of either near or distant targets during vertical (bob) translations in ambient illumination. We postulate that tVOR evolved not to stabilize the image of the target on the fovea, but rather to minimize retinal image motion between objects lying in different depth planes, in order to optimize motion parallax information. Such behavior is optimized when binocular visual cues of both near and distant targets are available in ambient light. Patients with progressive supranuclear palsy or cerebellar ataxia show impaired ability to increase tVOR responses appropriately when they view near targets. In cerebellar patients, impaired ability to adjust tVOR responses to viewing conditions occurs despite intact ability to converge at near. Loss of the ability to adjust tVOR according to viewing conditions appears to represent a distinct disorder of vestibular function.

  13. Studies of the horizontal vestibulo-ocular reflex on STS 7 and 8

    NASA Technical Reports Server (NTRS)

    Thornton, William E.; Uri, John J.; Moore, Thomas P.; Pool, Sam L.

    1988-01-01

    Unpaced voluntary horizontal head oscillation was used to study the Vestibulo-Ocular Reflex (VOR) on Shuttle flights STS 7 and 8. Ten subjects performed head oscillations at 0.33 Hz + or - 30 deg amplitude under the followng conditions: VVOR (visual VOR), eyes open and fixed on a stationary target; VOR-EC, with eyes closed and fixed on the same target in imagination; and VOR-S (VOR suppression), with eyes open and fixed on a head-synchronized target. Effects of weightlessness, flight phase, and Space Motion Sickness (SMS) on head oscillation characteristics were examined. A significant increase in head oscillation frequency was noted inflight in subjects free from SMS. In subjects susceptible to SMS, frequency was reduced during their Symptomatic period. The data also suggest that the amplitude and peak velocity of head oscillation were reduced early inflight. No significant changes were noted in reflex gain or phase in any of the test conditions; however, there was a suggestion of an increase in VVOR and VOR-ES gain early inflight in asymptomatic subjects. A significant difference in VOR-S was found between SMS susceptible and non-susceptible subjects. There is no evidence that any changes in VOR characteristics contributed to SMS.

  14. Willkommen, Mr. Chance: Methodologische Betrachtungen zur Gute empirischer Forschung in der Padagogik, diskutiert vor allem an der neueren Untersuchung uber Gewalt von Heitmeyer u.a. (1995) = Welcome, Mr. Chance: Methodological Considerations Concerning the Quality of Empirical Research in Educational Science Based on a Recent Study on Violence Published by Heitmeyer et al. (1995).

    ERIC Educational Resources Information Center

    Wellenreuther, Martin

    1997-01-01

    Argues that the usefulness of strictly quantitative research is still questioned in educational studies, primarily due to deficiencies in methodological training. Uses a critique of a recent study by Heitmeyer et al. (1995) to illustrate the requirements of "good" empirical research. Considers the problems of hypothesis testing in field research.…

  15. Habituation and adaptation of the vestibuloocular reflex: a model of differential control by the vestibulocerebellum

    NASA Technical Reports Server (NTRS)

    Cohen, H.; Cohen, B.; Raphan, T.; Waespe, W.

    1992-01-01

    We habituated the dominant time constant of the horizontal vestibuloocular reflex (VOR) of rhesus and cynomolgus monkeys by repeated testing with steps of velocity about a vertical axis and adapted the gain of the VOR by altering visual input with magnifying and reducing lenses. After baseline values were established, the nodulus and ventral uvula of the vestibulocerebellum were ablated in two monkeys, and the effects of nodulouvulectomy and flocculectomy on VOR gain adaptation and habituation were compared. The VOR time constant decreased with repeated testing, rapidly at first and more slowly thereafter. The gain of the VOR was unaffected. Massed trials were more effective than distributed trials in producing habituation. Regardless of the schedule of testing, the VOR time constant never fell below the time constant of the semicircular canals (approximately 5 s). This finding indicates that only the slow component of the vestibular response, the component produced by velocity storage, was habituated. In agreement with this, the time constant of optokinetic after-nystagmus (OKAN) was habituated concurrently with the VOR. Average values for VOR habituation were obtained on a per session basis for six animals. The VOR gain was adapted by natural head movements in partially habituated monkeys while they wore x 2.2 magnifying or x 0.5 reducing lenses. Adaptation occurred rapidly and reached about +/- 30%, similar to values obtained using forced rotation. VOR gain adaptation did not cause additional habituation of the time constant. When the VOR gain was reduced in animals with a long VOR time constant, there were overshoots in eye velocity that peaked at about 6-8 s after the onset or end of constant-velocity rotation. These overshoots occurred at times when the velocity storage integrator would have been maximally activated by semicircular canal input. Since the activity generated in the canals is not altered by visual adaptation, this finding indicates that the gain

  16. Studies of the horizontal vestibulo-ocular reflex in spaceflight

    NASA Technical Reports Server (NTRS)

    Thornton, William E.; Uri, John J.; Moore, Tom; Pool, Sam

    1989-01-01

    Changes in the vestibulo-ocular reflex (VOR) during space flight have been suspected of contributing to space motion sickness. The horizontal VOR was studied in nine subjects on two space shuttle missions. Active unpaced head oscillation at 0.3 Hz was used as the stimulus to examine the gain and phase of the VOR with and without visual input, as well as the visual suppression of the reflex. No statistically significant changes were noted inflight in the gains or phase shifts of the VOR during any test condition, or between space motion sickness susceptible and nonsusceptible populations. Although VOR suppression was unaffected by spaceflight, the space motion sickness-susceptible group tended to exhibit greater error in the suppression than the nonsusceptible group. It is concluded that at this stimulus frequency, VOR gain is unaffected by space-flight, and any minor individual changes do not seem to contribute to space motion sickness.

  17. Comparison of horizontal and vertical dynamic visual acuity in patients with vestibular dysfunction and nonvestibular dizziness.

    PubMed

    Roberts, Richard A; Gans, Richard E

    2007-03-01

    Blurred vision with head movement is a common symptom reported by patients with vestibular dysfunction affecting the vestibulo-ocular reflex (VOR). Impaired VOR can be measured by comparing visual acuity in which there is no head movement to visual acuity obtained with head movement. A previous study demonstrated that dynamic visual acuity (DVA) testing using vertical head movement revealed deficits in impaired VOR. There is evidence that horizontal head movement is more sensitive to impaired VOR. The objective of this investigation was to compare horizontal and vertical DVA in participants with normal vestibular function (NVF), impaired vestibular function (IVF), and participants with nonvestibular dizziness (NVD). Participants performed the visual acuity task in a baseline condition with no movement and also in two dynamic conditions, horizontal head movement and vertical head movement. Horizontal DVA was twice as sensitive to impaired VOR than vertical DVA. Results suggest that horizontal volitional head movement should be incorporated into tasks measuring functional deficits of impaired VOR.

  18. The conjugacy of the vestibulo-ocular reflex evoked by single labyrinth stimulation in awake monkeys.

    PubMed

    Tang, Xuehui; Xu, Youguo; Simpson, Ivra; Jeffcoat, Ben; Mustain, William; Zhou, Wu

    2010-10-01

    It is well known that the vestibulo-ocular reflex (VOR) is conjugate when measured in the dark with minimal vergence. But the neural basis of the VOR conjugacy remains to be identified. In the present study, we measured the VOR conjugacy during single labyrinth stimulation to examine whether the VOR conjugacy depends on reciprocal stimulation of the two labyrinths. There are conflicting views on this issue. First, since the vestibular signals carried by the ascending tract of Deiters' are distributed exclusively to the motoneurons of the ipsilateral eye, the neural innervations after single labyrinth stimulation are not symmetrical for the two eyes. Thus, single labyrinth stimulation may generate disjunctive VOR responses. Second, the only published study on this issue was an electrooculography (EOG) study that reported disjunctive VOR responses during unilateral caloric irrigation (Wolfe in Ann Otol 88:79-85, 1979). Third, the VOR during unilateral caloric stimulation performed in clinical vestibular tests is routinely perceived to be conjugate. To resolve these conflicting views, the present study examined the VOR conjugacy during single labyrinth stimulation by recording binocular eye position signals in awake monkeys with a search coil technique. In contradiction to the previous EOG study and the prediction based on the asymmetry of the unilateral brainstem VOR circuits, we found that the VOR during unilateral caloric irrigation was conjugate over a wide range of conditions. We conclude that the net neural innervations received by the two eyes are symmetrical after single labyrinth stimulation, despite the apparent asymmetry in the unilateral VOR pathways. A novel role for the ascending tract of Deiters' in the VOR conjugacy is proposed.

  19. The effect of retinal image error update rate on human vestibulo-ocular reflex gain adaptation.

    PubMed

    Fadaee, Shannon B; Migliaccio, Americo A

    2016-04-01

    The primary function of the angular vestibulo-ocular reflex (VOR) is to stabilise images on the retina during head movements. Retinal image movement is the likely feedback signal that drives VOR modification/adaptation for different viewing contexts. However, it is not clear whether a retinal image position or velocity error is used primarily as the feedback signal. Recent studies examining this signal are limited because they used near viewing to modify the VOR. However, it is not known whether near viewing drives VOR adaptation or is a pre-programmed contextual cue that modifies the VOR. Our study is based on analysis of the VOR evoked by horizontal head impulses during an established adaptation task. Fourteen human subjects underwent incremental unilateral VOR adaptation training and were tested using the scleral search coil technique over three separate sessions. The update rate of the laser target position (source of the retinal image error signal) used to drive VOR adaptation was different for each session [50 (once every 20 ms), 20 and 15/35 Hz]. Our results show unilateral VOR adaptation occurred at 50 and 20 Hz for both the active (23.0 ± 9.6 and 11.9 ± 9.1% increase on adapting side, respectively) and passive VOR (13.5 ± 14.9, 10.4 ± 12.2%). At 15 Hz, unilateral adaptation no longer occurred in the subject group for both the active and passive VOR, whereas individually, 4/9 subjects tested at 15 Hz had significant adaptation. Our findings suggest that 1-2 retinal image position error signals every 100 ms (i.e. target position update rate 15-20 Hz) are sufficient to drive VOR adaptation.

  20. Three-dimensional vibration-induced vestibulo-ocular reflex identifies vertical semicircular canal dehiscence.

    PubMed

    Aw, Swee Tin; Aw, Grace Elizabeth; Todd, Michael John; Bradshaw, Andrew Philip; Halmagyi, Gabor Michael

    2011-10-01

    Vertical semicircular canal dehiscence (VSCD) due to superior canal dehiscence (SCD) or posterior canal dehiscence (PCD) of the temporal bone causes vestibular and cochlear hypersensitivity to sound. This study aimed to characterize the vibration-induced vestibulo-ocular reflex (ViVOR) in VSCD. ViVORs in one PCD and 17 SCD patients, confirmed by CT imaging reformatted in semicircular canal planes, were measured with dual-search coils as binocular three-dimensional eye rotations induced by skull vibrations from a bone oscillator (B71-10 ohms) at 7 ms, 500 Hz, 135-dB peak-force level (re: 1 μN). The ViVOR eye rotation axes were computed by vector analysis and referenced to known semicircular canal planes. Onset latency of the ViVOR was 11 ms. ViVOR from VSCD was up to nine times greater than normal. The ViVOR's torsional rotation was always contraversive-torsional (the eye's upper pole rotated away from the stimulated ear), i.e. its direction was clockwise from a left and counterclockwise from a right VSCD, thereby lateralizing the side of the VSCD. The ViVORs vertical component distinguishes PCD from SCD, being downwards in PCD and upwards in SCD. In unilateral VSCD, the ViVOR eye rotation axis aligned closest to the dehiscent vertical semicircular canal axis from either ipsilateral or contralateral mastoid vibrations. However, in bilateral VSCDs, the ViVOR eye rotation axis lateralized to the ipsilateral dehiscent vertical semicircular canal axis. ViVOR was evoked in ossicular chain dysfunction, even when air-conducted click vestibulo-ocular reflex (VOR) was absent or markedly reduced. Hence, ViVOR could be a useful measurement to identify unilateral or bilateral VSCD even in the presence of ossicular chain dysfunction.

  1. Behavior of human horizontal vestibulo-ocular reflex in response to high-acceleration stimuli

    NASA Technical Reports Server (NTRS)

    Maas, E. F.; Huebner, W. P.; Seidman, S. H.; Leigh, R. J.

    1989-01-01

    The horizontal vestibulo-ocular reflex (VOR) during transient, high-acceleration (1900-7100 deg/sec-squared) head rotations was studied in four human subjects. Such stimuli perturbed the angle of gaze and caused illusory movement of a viewed target (oscillopsia). The disturbance of gaze could be attributed to the latency of the VOR (which ranged from 6-15 ms) and inadequate compensatory eye rotations (median VOR gain ranged from 0.61-0.83).

  2. The effect of retinal image error update rate on human vestibulo-ocular reflex gain adaptation.

    PubMed

    Fadaee, Shannon B; Migliaccio, Americo A

    2016-04-01

    The primary function of the angular vestibulo-ocular reflex (VOR) is to stabilise images on the retina during head movements. Retinal image movement is the likely feedback signal that drives VOR modification/adaptation for different viewing contexts. However, it is not clear whether a retinal image position or velocity error is used primarily as the feedback signal. Recent studies examining this signal are limited because they used near viewing to modify the VOR. However, it is not known whether near viewing drives VOR adaptation or is a pre-programmed contextual cue that modifies the VOR. Our study is based on analysis of the VOR evoked by horizontal head impulses during an established adaptation task. Fourteen human subjects underwent incremental unilateral VOR adaptation training and were tested using the scleral search coil technique over three separate sessions. The update rate of the laser target position (source of the retinal image error signal) used to drive VOR adaptation was different for each session [50 (once every 20 ms), 20 and 15/35 Hz]. Our results show unilateral VOR adaptation occurred at 50 and 20 Hz for both the active (23.0 ± 9.6 and 11.9 ± 9.1% increase on adapting side, respectively) and passive VOR (13.5 ± 14.9, 10.4 ± 12.2%). At 15 Hz, unilateral adaptation no longer occurred in the subject group for both the active and passive VOR, whereas individually, 4/9 subjects tested at 15 Hz had significant adaptation. Our findings suggest that 1-2 retinal image position error signals every 100 ms (i.e. target position update rate 15-20 Hz) are sufficient to drive VOR adaptation. PMID:26715411

  3. 76 FR 65951 - Standard Instrument Approach Procedures, and Takeoff Minimums and Obstacle Departure Procedures...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-10-25

    ... Obstacle DP, Presque Isle. Amdt 4. 17-Nov-11 NE Columbus Columbus Muni.... 1/7813 9/19/11 VOR RWY 14, Amdt B. 17-Nov-11 NE Columbus Columbus Muni.... 1/7814 9/19/11 VOR RWY 32, Amdt 14A. 17-Nov-11 NE Columbus Columbus Muni.... 1/7815 9/19/11 VOR/DME RWY 32, Amdt 3. 17-Nov-11 NE Columbus Columbus Muni.......

  4. Identification of the vestibulo-ocular reflex dynamics.

    PubMed

    Ranjbaran, Mina; Galiana, Henrietta L

    2014-01-01

    The vestibulo-ocular reflex (VOR) plays an important role in our daily activities by enabling us to fixate on objects during head movements. Modeling and identification of the VOR improves our insight into the system behavior and helps in diagnosing various disorders. However, the switching nature of eye movements, including the VOR, makes the dynamic analysis challenging. In this work we are using integration of subspace and prediction error methods to analyze VOR dynamics. The performance of the method is evaluated using simulation studies and experimental data.

  5. 14 CFR 91.161 - Special awareness training required for pilots flying under visual flight rules within a 60...

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... pilots flying under visual flight rules within a 60-nautical mile radius of the Washington, DC VOR/DME... Rules Visual Flight Rules § 91.161 Special awareness training required for pilots flying under visual... of an aircraft while flying within a 60-nautical mile radius of the DCA VOR/DME, under VFR,...

  6. 14 CFR 91.161 - Special awareness training required for pilots flying under visual flight rules within a 60...

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... pilots flying under visual flight rules within a 60-nautical mile radius of the Washington, DC VOR/DME... Rules Visual Flight Rules § 91.161 Special awareness training required for pilots flying under visual... of an aircraft while flying within a 60-nautical mile radius of the DCA VOR/DME, under VFR,...

  7. 75 FR 8241 - Standard Instrument Approach Procedures, and Takeoff Minimums and Obstacle Departure Procedures...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-02-24

    ... Policies and Procedures (44 FR 11034; February 26,1979); and (3) does not warrant preparation of a..., VOR/DME RWY 9, Amdt 3 On January 28, 2010 (75 FR 18) the FAA published an Amendment in Docket No... Airpark, RNAV (GPS) RWY 9, Amdt 1 Atlanta, GA, Newman Coweta County, VOR/DME-A, Amdt 8 Le Mars, IA,...

  8. 78 FR 53239 - Establishment, Modification and Cancellation of Air Traffic Service (ATS) Routes; Northeast...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-08-29

    ... (FAA), DOT. ACTION: Final rule. SUMMARY: This action modifies two jet routes, six VOR Federal airways... of proposed rulemaking (NPRM) to amend two jet routes, six VOR Federal airways, and three area... northeast United States (78 FR 38236, June 26, 2013). Interested parties were invited to participate in...

  9. The Neural Basis for Learning of Simple Motor Skills.

    ERIC Educational Resources Information Center

    Lisberger, Stephen G.

    1988-01-01

    Discusses the vestibulo-ocular reflex (VOR) which is used to investigate the neural basis for motor learning in monkeys. Suggests organizing principles that may apply in forms of motor learning as a result of similarities among VOR and other motor systems. (Author/RT)

  10. The vestibular implant: frequency-dependency of the electrically evoked vestibulo-ocular reflex in humans.

    PubMed

    van de Berg, Raymond; Guinand, Nils; Nguyen, T A Khoa; Ranieri, Maurizio; Cavuscens, Samuel; Guyot, Jean-Philippe; Stokroos, Robert; Kingma, Herman; Perez-Fornos, Angelica

    2014-01-01

    The vestibulo-ocular reflex (VOR) shows frequency-dependent behavior. This study investigated whether the characteristics of the electrically evoked VOR (eVOR) elicited by a vestibular implant, showed the same frequency-dependency. Twelve vestibular electrodes implanted in seven patients with bilateral vestibular hypofunction (BVH) were tested. Stimuli consisted of amplitude-modulated electrical stimulation with a sinusoidal profile at frequencies of 0.5, 1, and 2 Hz. The main characteristics of the eVOR were evaluated and compared to the "natural" VOR characteristics measured in a group of age-matched healthy volunteers who were subjected to horizontal whole body rotations with equivalent sinusoidal velocity profiles at the same frequencies. A strong and significant effect of frequency was observed in the total peak eye velocity of the eVOR. This effect was similar to that observed in the "natural" VOR. Other characteristics of the (e)VOR (angle, habituation-index, and asymmetry) showed no significant frequency-dependent effect. In conclusion, this study demonstrates that, at least at the specific (limited) frequency range tested, responses elicited by a vestibular implant closely mimic the frequency-dependency of the "normal" vestibular system.

  11. 77 FR 1015 - Standard Instrument Approach Procedures, and Takeoff Minimums and Obstacle Departure Procedures...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-01-09

    ... ``significant rule '' under DOT Regulatory Policies and Procedures (44 FR 11034; February 26,1979); and (3) does..., VOR RWY 26L, Amdt 32 Houston, TX, Sugar Land Rgnl, ILS OR LOC RWY 35, Amdt 4 Houston, TX, Sugar Land Rgnl, RNAV (GPS) RWY 35, Amdt 2 Houston, TX, Sugar Land Rgnl, VOR/DME-A, Amdt 2 Marshall, TX,...

  12. 76 FR 46202 - IFR Altitudes; Miscellaneous Amendments

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-08-02

    ..., MT FIX Billings, MT VORTAC. W BND 9000 E BND 6400 Sec. 95.6026 VOR Federal Airway V26 Is Amended To... Part Livingston, MT VOR/DME Reepo, MT FIX 9700 Colus, MT FIX Billings, MT VORTAC. ] W BND 9000 E BND... ``significant rule'' under DOT Regulatory Policies and Procedures (44 FR 11034; February 26, 1979); and (3)...

  13. Auf der Suche nach extrasolaren Transitplaneten

    NASA Astrophysics Data System (ADS)

    Heller, René

    2010-06-01

    Planeten um andere Sonnen, die von der Erde aus gesehen einmal während ihres Orbits vor ihrem Zentralstern vorbeiziehen, eröffnen eine bis vor Kurzem ungeahnte Palette an Möglichkeiten zu ihrer Untersuchung. Nur: Wo am Himmel lassen sich diese Kandidaten für Sternbedeckungen eigentlich finden?

  14. Multiple source navigation signal generator

    NASA Astrophysics Data System (ADS)

    Bojda, Petr

    2010-09-01

    The paper presents a FPGA based digital VOR/LOC signal generator. It provides the composite signal, which consists of the particular signals of several predefined navigation sources - VOR beacons. Design of the generator is implemented into the two different FPGA DSP platforms.

  15. Thin Clients: Anwendungsvirtualisierung (SBC) oder Desktop-Virtualisierung?

    NASA Astrophysics Data System (ADS)

    von Lamp, Frank

    Mit Thin Clients lassen sich verschiedene auf Virtualisierung basierende Infrastrukturen unterstützen, die jeweils unterschiedliche Vor- und Nachteile besitzen. Dieser Beitrag stellt die wichtigsten Vor- und Nachteile von Server Based Computing und Desktop-Virtualisierung mit Thin Clients gegenüber.

  16. Functional organization of primate translational vestibulo-ocular reflexes and effects of unilateral labyrinthectomy

    NASA Technical Reports Server (NTRS)

    Angelaki, D. E.; McHenry, M. Q.; Newlands, S. D.; Dickman, J. D.

    1999-01-01

    Translational vestibulo-ocular reflexes (trVORs) are characterized by distinct spatio-temporal properties and sensitivities that are proportional to the inverse of viewing distance. Anodal (inhibitory) labyrinthine stimulation (100 microA, < 2 s) during motion decreased the high-pass filtered dynamics, as well as horizontal trVOR sensitivity and its dependence on viewing distance. Cathodal (excitatory) currents had opposite effects. Translational VORs were also affected after unilateral labyrinthectomy. Animals lost their ability to modulate trVOR sensitivity as a function of viewing distance acutely after the lesion. These deficits partially recovered over time, albeit a significant reduction in trVOR sensitivity as a function of viewing distance remained in compensated animals. During fore-aft motion, the effects of unilateral labyrinthectomy were more dramatic. Both acute and compensated animals permanently lost their ability to modulate fore-aft trVOR responses as a function of target eccentricity. These results suggest that (1) the dynamics and viewing distance-dependent properties of the trVORs are very sensitive to changes in the resting firing rate of vestibular afferents and, consequently, vestibular nuclei neurons; (2) the most irregularly firing primary otolith afferents that are most sensitive to labyrinthine electrical stimulation might contribute to reflex dynamics and sensitivity; (3) inputs from both labyrinths are necessary for the generation of the translational VORs.

  17. Vestibulo-Ocular Response and Balance Control in Children and Young Adults with Mild-to-Moderate Intellectual and Developmental Disability: A Pilot Study

    ERIC Educational Resources Information Center

    Zur, Oz; Ronen, Ayelet; Melzer, Itshak; Carmeli, Eli

    2013-01-01

    The vestibulo-ocular response (VOR) may not be fully developed in children with an intellectual and developmental disability (IDD). This study aimed to identify the presence of VOR deficit in children and young adults with unspecified mild-to-moderate intellectual and developmental disability and its effect on balance control. Twenty-one children…

  18. 14 CFR 91.161 - Special awareness training required for pilots flying under visual flight rules within a 60...

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... pilots flying under visual flight rules within a 60-nautical mile radius of the Washington, DC VOR/DME... Rules Visual Flight Rules § 91.161 Special awareness training required for pilots flying under visual... of an aircraft while flying within a 60-nautical mile radius of the DCA VOR/DME, under VFR,...

  19. 14 CFR 91.161 - Special awareness training required for pilots flying under visual flight rules within a 60...

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... pilots flying under visual flight rules within a 60-nautical mile radius of the Washington, DC VOR/DME... Rules Visual Flight Rules § 91.161 Special awareness training required for pilots flying under visual... of an aircraft while flying within a 60-nautical mile radius of the DCA VOR/DME, under VFR,...

  20. 14 CFR 91.161 - Special awareness training required for pilots flying under visual flight rules within a 60...

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... pilots flying under visual flight rules within a 60-nautical mile radius of the Washington, DC VOR/DME... Rules Visual Flight Rules § 91.161 Special awareness training required for pilots flying under visual... of an aircraft while flying within a 60-nautical mile radius of the DCA VOR/DME, under VFR,...

  1. Über die Perihelzeit des Halleyschen Kometen bei seiner Erscheinung im Jahre 837

    NASA Astrophysics Data System (ADS)

    Landgraf, Werner

    1983-07-01

    837 erfolgte ein naher Vorübergang des Halleyschen Kometen an der Erde. Bei kleiner Verfrühung oder Verspätung ist aufgrund der Differenz seiner gravitativen Ablenkung seine Bahn vor 837 unterschiedlich. Aus den früheren Beobachtungen ergibt sich daher sehr genau die Zeit von Vorbeiflug und Periheldurchgang 837 .

  2. Age-related changes in human vestibulo-ocular and optokinetic reflexes: Pseudorandom rotation tests

    NASA Technical Reports Server (NTRS)

    Peterka, R. J.; Black, F. O.; Schoenhoff, M. B.

    1989-01-01

    The dynamic response properties of horizontal vestibulo-ocular reflex (VOR) and optokinetic reflex (OKR) were characterized in 216 human subjects ranging in age from 7 to 81 years. The object of this cross-sectional study was to determine the effects of aging on VOR and OKR reflex dynamics, and to identify the distributions of parameters which describe VOR and OKR responses to pseudorandom stimuli in a putatively normal population. In general, VOR and OKR response parameters changed in a manner consistent with declining function with increasing age. For the VOR this was reflected in declining response amplitudes, although the magnitude of the decline was small relative to the variability of the data. For the OKR the lag time of the response, probably associated with the time required for visual information processing, increased linearly with age at a rate of about 1 ms per year.

  3. Vestibulo-Oculomotor Reflex Recording Using the Scleral Search Coil Technique. Review of Peripheral Vestibular Disorders

    PubMed Central

    Boleas-Aguirre, Marisol; Migliaccio, Amerio A.; Carey, John P.

    2010-01-01

    Our goal is to review vestibulo-oculomotor reflex (VOR) studies on several peripheral vestibular disorders (Ménière’s disease, vestibular neuritis, benign paroxysmal positional vertigo, superior canal dehiscence syndrome, and vestibular neuroma), using the scleral search coil (SSC) technique. Head movements are detected by vestibular receptors and the elicited VOR is responsible for compensatory 3 dimensional eye movements. Therefore, to study the VOR it is necessary to assess the direction and velocity of 3 dimensional head, and eye movements. This can be achieved using the SSC technique. Interaction between a scleral search coil and an alternating magnetic field generates an electrical signal that is proportional to eye position. Ideally, eye rotation axis is aligned with head rotation axis and VOR gain (eye velocity/head velocity) for horizontal and vertical head rotations is almost 1. The VOR gain, however, for torsional head rotations is smaller and about 0.7. PMID:17683700

  4. Plasticity within non-cerebellar pathways rapidly shapes motor performance in vivo.

    PubMed

    Mitchell, Diana E; Della Santina, Charles C; Cullen, Kathleen E

    2016-01-01

    Although cerebellar mechanisms are vital to maintain accuracy during complex movements and to calibrate simple reflexes, recent in vitro studies have called into question the widely held view that synaptic changes within cerebellar pathways exclusively guide alterations in motor performance. Here we investigate the vestibulo-ocular reflex (VOR) circuitry by applying temporally precise activation of vestibular afferents in awake-behaving monkeys to link plasticity at different neural sites with changes in motor performance. Behaviourally relevant activation patterns produce rapid attenuation of direct pathway VOR neurons, but not their nerve input. Changes in the strength of this pathway are sufficient to induce a lasting decrease in the evoked VOR. In addition, indirect brainstem pathways display complementary nearly instantaneous changes, contributing to compensating for the reduced sensitivity of primary VOR neurons. Taken together, our data provide evidence that multiple sites of plasticity within VOR pathways can rapidly shape motor performance in vivo. PMID:27157829

  5. Effects of adaptation of vestibulo-ocular reflex function on manual target localization

    NASA Technical Reports Server (NTRS)

    Bloomberg, J. J.; Merkle, L. A.; Barry, S. R.; Huebner, W. P.; Cohen, H. S.; Mueller, S. A.; Fordice, J.

    2000-01-01

    The goal of the present study was to determine if adaptive modulation of vestibulo-ocular reflex (VOR) function is associated with commensurate alterations in manual target localization. To measure the effects of adapted VOR on manual responses we developed the Vestibular-Contingent Pointing Test (VCP). In the VCP test, subjects pointed to a remembered target following passive whole body rotation in the dark. In the first experiment, subjects performed VCP before and after wearing 0.5X minifying lenses that adaptively attenuate horizontal VOR gain. Results showed that adaptive reduction in horizontal VOR gain was accompanied by a commensurate change in VCP performance. In the second experiment, bilaterally labyrinthine deficient (LD) subjects were tested to confirm that vestibular cues were central to the spatial coding of both eye and hand movements during VCP. LD subjects performed significantly worse than normal subjects. These results demonstrate that adaptive change in VOR can lead to alterations in manual target localization.

  6. Effect of temperature on the normal and adapted vestibulo-ocular reflex in the goldfish.

    PubMed

    McElligott, J G; Weiser, M; Baker, R

    1995-10-01

    1. The vestibulo-ocular reflex, a sensorimotor process, operates in a similar manner for homeothermic (mammals) and poikilothermic (fish) animals. However, individual physiological, biochemical, and/or pharmacological thermolabile processes that underlie the operation of this reflex could alter the operation of this reflex in a poikilotherm. The object of this study was to determine what aspects of the vestibulo-ocular reflex are affected by temperature changes naturally experienced by a poikilothermic animal, the goldfish. 2. Experiments were conducted on the visuovestibulo-(Vis-VOR) and vestibulo-ocular reflex (VOR) during normal operation as well as during the acquisition (learning) and retention (memory) phases of adaptive gain change. These studies were carried out at temperatures to which goldfish had been acclimated over several weeks and after rapid (< 5 min) shifts from this acclimation temperature. 3. Normal sinusoidal Vis-VOR and VOR gains before adaptation were found to be independent of the acclimation temperature over a wide range. Acute temperature changes of up to 10 degrees C either above or below a 20 degrees C acclimation temperature (Ac degree C = 20 degrees C) did not significantly modify normal visual and/or vestibular oculomotor reflex gains. 4. Surprisingly, slight reductions in temperature, as small as 2.5 degrees C, noticeably reduced Vis-VOR and VOR gain adaptations. Both short (3 h) and intermediate (up to 48 h) term reflex modifications were affected. Loss of adaptation was observed 10 degrees C below the acclimation temperature (Ac - 10 degrees C); however, return to the original temperature immediately restored most (60-100%) of the previously acquired Vis-VOR and VOR gain changes. In contrast, elevation of temperature up to 10 degrees C above the acclimation temperature (Ac + 10 degrees C) did not alter either increases or decreases in the adapted Vis-VOR or VOR gain. 5. A decrease in temperature reduced the magnitude of an adapted

  7. Light conditions affect the roll-induced vestibuloocular reflex in Xenopus laevis tadpoles

    NASA Astrophysics Data System (ADS)

    El-Yamany, Nabil A.

    2008-12-01

    In Xenopus laevis tadpoles, effects of asymmetrical light conditions on the roll-induced vestibuloocular reflex (rVOR) were tested for the developmental period between stage 47 and 49. For comparison, the rVOR was tested in dim- and high-symmetrical light environments. Test parameters were the rVOR gain and rVOR amplitude. Under all light conditions, the rVOR increased from tadpole stage 47 to 49. For all stages, the asymmetrical light field induced the strongest response, the dim light field the weakest one. The response for the left and right eye was identical, even if the tadpoles were tested under asymmetrical light conditions. The experiments can be considered as hints (1) for an age-dependent light sensitivity of vestibular neurons, and (2) for the existence of control systems for coordinated eye movements that has its origin in the proprioceptors of the extraocular eye muscles.

  8. Plasticity within non-cerebellar pathways rapidly shapes motor performance in vivo

    PubMed Central

    Mitchell, Diana E.; Della Santina, Charles C.; Cullen, Kathleen E.

    2016-01-01

    Although cerebellar mechanisms are vital to maintain accuracy during complex movements and to calibrate simple reflexes, recent in vitro studies have called into question the widely held view that synaptic changes within cerebellar pathways exclusively guide alterations in motor performance. Here we investigate the vestibulo-ocular reflex (VOR) circuitry by applying temporally precise activation of vestibular afferents in awake-behaving monkeys to link plasticity at different neural sites with changes in motor performance. Behaviourally relevant activation patterns produce rapid attenuation of direct pathway VOR neurons, but not their nerve input. Changes in the strength of this pathway are sufficient to induce a lasting decrease in the evoked VOR. In addition, indirect brainstem pathways display complementary nearly instantaneous changes, contributing to compensating for the reduced sensitivity of primary VOR neurons. Taken together, our data provide evidence that multiple sites of plasticity within VOR pathways can rapidly shape motor performance in vivo. PMID:27157829

  9. Role of cerebellum in motion perception and vestibulo-ocular reflex-similarities and disparities.

    PubMed

    Shaikh, Aasef G; Palla, Antonella; Marti, Sarah; Olasagasti, Itsaso; Optican, Lance M; Zee, David S; Straumann, Dominik

    2013-02-01

    Vestibular velocity storage enhances the efficacy of the angular vestibulo-ocular reflex (VOR) during relatively low-frequency head rotations. This function is modulated by GABA-mediated inhibitory cerebellar projections. Velocity storage also exists in perceptual pathway and has similar functional principles as VOR. However, it is not known whether the neural substrate for perception and VOR overlap. We propose two possibilities. First, there is the same velocity storage for both VOR and perception; second, there are nonoverlapping neural networks: one might be involved in perception and the other for the VOR. We investigated these possibilities by measuring VOR and perceptual responses in healthy human subjects during whole-body, constant-velocity rotation steps about all three dimensions (yaw, pitch, and roll) before and after 10 mg of 4-aminopyridine (4-AP). 4-AP, a selective blocker of inward rectifier potassium conductance, can lead to increased synchronization and precision of Purkinje neuron discharge and possibly enhance the GABAergic action. Hence 4-AP could reduce the decay time constant of the perceived angular velocity and VOR. We found that 4-AP reduced the decay time constant, but the amount of reduction in the two processes, perception and VOR, was not the same, suggesting the possibility of nonoverlapping or partially overlapping neural substrates for VOR and perception. We also noted that, unlike the VOR, the perceived angular velocity gradually built up and plateau prior to decay. Hence, the perception pathway may have additional mechanism that changes the dynamics of perceived angular velocity beyond the velocity storage. 4-AP had no effects on the duration of build-up of perceived angular velocity, suggesting that the higher order processing of perception, beyond the velocity storage, might not occur under the influence of mechanism that could be influenced by 4-AP.

  10. Adaptation of the vestibulo-ocular reflex for forward-eyed foveate vision.

    PubMed

    Migliaccio, Americo A; Minor, Lloyd B; Della Santina, Charles C

    2010-10-15

    To maintain visual fixation on a distant target during head rotation, the angular vestibulo-ocular reflex (aVOR) should rotate the eyes at the same speed as the head and in exactly the opposite direction. However, in primates for which the 3-dimensional (3D) aVOR has been extensively characterised (humans and squirrel monkeys (Saimiri sciureus)), the aVOR response to roll head rotation about the naso-occipital axis is lower than that elicited by yaw and pitch, causing errors in aVOR magnitude and direction that vary with the axis of head rotation. In other words, primates keep the central part of the retinal image on the fovea (where photoreceptor density and visual acuity are greatest) but fail to keep that image from twisting about the eyes' resting optic axes. We tested the hypothesis that aVOR direction dependence is an adaptation related to primates' frontal-eyed, foveate status through comparison with the aVOR of a lateral-eyed, afoveate mammal (Chinchilla lanigera). As chinchillas' eyes are afoveate and never align with each other, we predicted that the chinchilla aVOR would be relatively low in gain and isotropic (equal in gain for every head rotation axis). In 11 normal chinchillas, we recorded binocular 3D eye movements in darkness during static tilts, 20-100 deg s(1) whole-body sinusoidal rotations (0.5-15 Hz), and 3000 deg s(2) acceleration steps. Although the chinchilla 3D aVOR gain changed with both frequency and peak velocity over the range we examined, we consistently found that it was more nearly isotropic than the primate aVOR. Our results suggest that primates' anisotropic aVOR represents an adaptation to their forward-eyed, foveate status. In primates, yaw and pitch aVOR must be compensatory to stabilise images on both foveae, whereas roll aVOR can be under-compensatory because the brain tolerates torsion of binocular images that remain on the foveae. In contrast, the lateral-eyed chinchilla faces different adaptive demands and thus enlists a

  11. Adaptive plasticity in the otolith-ocular reflex.

    PubMed

    Koizuka, Izumi

    2003-02-01

    This review focuses on the plasticity in the vestibulo-ocular reflex (VOR), especially in the otolith-ocular reflex (OOR). The VOR is a mechanism for the production of rapid compensatory eye movements during head movements. The VOR is under adaptive control which corrects VOR performance when visual-vestibular mismatch arises during head movements. It has been demonstrated that chronic exposure to certain visual environments, those generated by magnifying lenses and reversing prisms, alter the gain and phase of VOR in the dark in numerous species. Most experiments concerning such modification of the VOR have used semicircular canal stimulation. The VOR consists of the semicircular-ocular reflex (ScOR) and the OOR. There are few results regarding the relationship between the gain of the ScOR and the OOR. This review summarizes the studies on plasticity in the OOR. In addition, the difficulty in evaluating the OOR using current conventional methods including earth horizontal axis (EHA) rotation, off-vertical axis rotation (OVAR) and linear sled, is discussed. We believe that the ScOR and the OOR share common neural pathways in such a way that a change in the synaptic efficacy of one pathway is accompanied by a change in the other.

  12. Application of alkyl polyglycoside surfactant in ultrasonic-assisted extraction followed by macroporous resin enrichment for the separation of vitexin-2″-O-rhamnoside and vitexin from Crataegus pinnatifida leaves.

    PubMed

    Han, Feng; Guo, Yupin; Gu, Huiyan; Li, Fenglan; Hu, Baozhong; Yang, Lei

    2016-02-15

    An alkyl polyglycoside (APG) surfactant was used in ultrasonic-assisted extraction to effectively extract vitexin-2″-O-rhamnoside (VOR) and vitexin (VIT) from Crataegus pinnatifida leaves. APG0810 was selected as the surfactant. The extraction process was optimized for ultrasonic power, the APG concentration, ultrasonic time, soaking time, and liquid-solid ratio. The proposed approach showed good recovery (99.80-102.50% for VOR and 98.83-103.19% for VIT) and reproducibility (relative standard deviation, n=5; 3.7% for VOR and 4.2% for VIT) for both components. The proposed sample preparation method is both simple and effective. The use of APG for extraction of key herbal ingredients shows great potential. Ten widely used commercial macroporous resins were evaluated in a screening study to identify a suitable resin for the separation and purification of VOR and VIT. After comparing static and dynamic adsorption and desorption processes, HPD100B was selected as the most suitable resin. After column adsorption and desorption on this resin, the target compounds VOR and VIT can be effectively separated from the APG0810 extraction solution. Recoveries of VOR and VIT were 89.27%±0.42% and 85.29%±0.36%, respectively. The purity of VOR increased from 35.0% to 58.3% and the purity of VIT increased from 12.5% to 19.9%. PMID:26807707

  13. Automatic classification and robust identification of vestibulo-ocular reflex responses: from theory to practice: introducing GNL-HybELS.

    PubMed

    Ghoreyshi, Atiyeh; Galiana, Henrietta

    2011-10-01

    The Vestibulo-Ocular Reflex (VOR) stabilizes images of the world on our retinae when our head moves. Basic daily activities are thus impaired if this reflex malfunctions. During the past few decades, scientists have modeled and identified this system mathematically to diagnose and treat VOR deficits. However, traditional methods do not analyze VOR data comprehensively because they disregard the switching nature of nystagmus; this can bias estimates of VOR dynamics. Here we propose, for the first time, an automated tool to analyze entire VOR responses (slow and fast phases), without a priori classification of nystagmus segments. We have developed GNL-HybELS (Generalized NonLinear Hybrid Extended Least Squares), an algorithmic tool to simultaneously classify and identify the responses of a multi-mode nonlinear system with delay, such as the horizontal VOR and its alternating slow and fast phases. This algorithm combines the procedures of Generalized Principle Component Analysis (GPCA) for classification, and Hybrid Extended Least Squares (HybELS) for identification, by minimizing a cost function in an optimization framework. It is validated here on clean and noisy VOR simulations and then applied to clinical VOR tests on controls and patients. Prediction errors were less than 1 deg for simulations and ranged from .69 deg to 2.1 deg for the clinical data. Nonlinearities, asymmetries, and dynamic parameters were detected in normal and patient data, in both fast and slow phases of the response. This objective approach to VOR analysis now allows the design of more complex protocols for the testing of oculomotor and other hybrid systems.

  14. HIV-1 Expression Within Resting CD4+ T Cells After Multiple Doses of Vorinostat

    PubMed Central

    Archin, Nancy M.; Bateson, Rosalie; Tripathy, Manoj K.; Crooks, Amanda M.; Yang, Kuo-Hsiung; Dahl, Noelle P.; Kearney, Mary F.; Anderson, Elizabeth M.; Coffin, John M.; Strain, Matthew C.; Richman, Douglas D.; Robertson, Kevin R.; Kashuba, Angela D.; Bosch, Ronald J.; Hazuda, Daria J.; Kuruc, Joann D.; Eron, Joseph J.; Margolis, David M.

    2014-01-01

    Background. A single dose of the histone deacetylase inhibitor vorinostat (VOR) up-regulates HIV RNA expression within resting CD4+ T cells of treated, aviremic human immunodeficiency virus (HIV)–positive participants. The ability of multiple exposures to VOR to repeatedly disrupt latency has not been directly measured, to our knowledge. Methods. Five participants in whom resting CD4+ T-cell–associated HIV RNA (rc-RNA) increased after a single dose of VOR agreed to receive daily VOR Monday through Wednesday for 8 weekly cycles. VOR serum levels, peripheral blood mononuclear cell histone acetylation, plasma HIV RNA single-copy assays, rc-RNA, total cellular HIV DNA, and quantitative viral outgrowth assays from resting CD4+ T cells were assayed. Results. VOR was well tolerated, with exposures within expected parameters. However, rc-RNA measured after dose 11 (second dose of cycle 4) or dose 22 (second dose of cycle 8) increased significantly in only 3 of the 5 participants, and the magnitude of the rc-RNA increase was much reduced compared with that after a single dose. Changes in histone acetylation were blunted. Results of quantitative viral outgrowth and other assays were unchanged. Conclusions. Although HIV latency is disrupted by an initial VOR dose, the effect of subsequent doses in this protocol was much reduced. We hypothesize that the global effect of VOR results in a refractory period of ≥24 hours. The optimal schedule for VOR administration is still to be defined. PMID:24620025

  15. The vestibulo-ocular reflex and its possible roles in space motion sickness

    NASA Technical Reports Server (NTRS)

    Watt, Douglas G. D.

    1987-01-01

    Prolonged exposure to an inappropriate vestibulo-ocular reflex (VOR) will usually lead to motion sickness, and it has been predicted on theoretical grounds that VOR gain may be decreased in weightlessness. While experiments during parabolic flight in aircraft tend to confirm this prediction, experiments during orbital spaceflight have led to apparently contradictory results. It is suggested that VOR gain is reduced initially, but that rapid compensatory mechanisms restore it to normal within minutes of reaching weightlessness. However, even though this process may lead to the rapid return of functionally normal gaze stability, it may not protect against the development of motion sickness.

  16. A Sparse Matrix Approach for Simultaneous Quantification of Nystagmus and Saccade

    NASA Technical Reports Server (NTRS)

    Kukreja, Sunil L.; Stone, Lee; Boyle, Richard D.

    2012-01-01

    The vestibulo-ocular reflex (VOR) consists of two intermingled non-linear subsystems; namely, nystagmus and saccade. Typically, nystagmus is analysed using a single sufficiently long signal or a concatenation of them. Saccade information is not analysed and discarded due to insufficient data length to provide consistent and minimum variance estimates. This paper presents a novel sparse matrix approach to system identification of the VOR. It allows for the simultaneous estimation of both nystagmus and saccade signals. We show via simulation of the VOR that our technique provides consistent and unbiased estimates in the presence of output additive noise.

  17. Contribution of irregular semicircular canal afferents to the horizontal vestibuloocular response during constant velocity rotation

    NASA Technical Reports Server (NTRS)

    Angelaki, D. E.; Perachio, A. A.

    1993-01-01

    1. The effects of constant anodal currents (100 microA) delivered bilaterally to both labyrinths on the horizontal vestibuloocular response (VOR) were studied in squirrel monkeys during steps of angular velocity in the dark. We report that bilateral anodal currents decreased eye velocity approximately 30-50% during the period of galvanic stimulation without a change in the time constant of VOR. The decrease in eye velocity, present during steps of angular velocity, was not observed during sinusoidal head rotation at 0.2, 0.5, and 1 Hz. The results suggest that responses from irregular vestibular afferents influence VOR amplitude during constant velocity rotation.

  18. Earth horizontal axis rotational responses in patients with unilateral peripheral vestibular deficits

    NASA Technical Reports Server (NTRS)

    Furman, Joseph M. R.; Kamerer, Donald B.; Wall, Conrad, III

    1989-01-01

    The vestibulo-ocular reflex (VOR) of five patients with surgically confirmed unilateral peripheral vestibular lesions is evaluated. Testing used both earth vertical axis (EVA) and earth horizontal axis (EHA) yaw rotation. Results indicated that the patients had short VOR time constants, asymmetric responses to both EVA and EHA rotation, and normal EHA modulation components. These findings suggest that unilateral peripheral vestibular loss causes a shortened VOR time constant even with the addition of dynamic otolithic stimulation and causes an asymmetry in semicircular canal-ocular reflexes and one aspect of otolith-ocular reflexes.

  19. 76 FR 21622 - IFR Altitudes; Miscellaneous Amendments

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-04-18

    ... ``significant rule'' under DOT Regulatory Policies and Procedures (44 FR 11034; February 26, 1979); and (3) does... 17500 THEDFORD, NE VOR/DME MARSS, NE FIX 4900 17500 MARSS, NE FIX VALENTINE, NE NDB 4800 17500...

  20. Quantifying the vestibulo-ocular reflex with video-oculography: nature and frequency of artifacts.

    PubMed

    Mantokoudis, Georgios; Saber Tehrani, Ali S; Kattah, Jorge C; Eibenberger, Karin; Guede, Cynthia I; Zee, David S; Newman-Toker, David E

    2015-01-01

    Video-oculography devices are now used to quantify the vestibulo-ocular reflex (VOR) at the bedside using the head impulse test (HIT). Little is known about the impact of disruptive phenomena (e.g. corrective saccades, nystagmus, fixation losses, eye-blink artifacts) on quantitative VOR assessment in acute vertigo. This study systematically characterized the frequency, nature, and impact of artifacts on HIT VOR measures. From a prospective study of 26 patients with acute vestibular syndrome (16 vestibular neuritis, 10 stroke), we classified findings using a structured coding manual. Of 1,358 individual HIT traces, 72% had abnormal disruptive saccades, 44% had at least one artifact, and 42% were uninterpretable. Physicians using quantitative recording devices to measure head impulse VOR responses for clinical diagnosis should be aware of the potential impact of disruptive eye movements and measurement artifacts.

  1. Vortioxetine

    MedlinePlus

    (vor'' tye ox' e teen)A small number of children, teenagers, and young adults (up to 24 years of age) who took antidepressants ('mood elevators') such as vortioxetine during clinical studies became suicidal (thinking about ...

  2. Evaluation of Microwave Landing System (MLS) effect on the delivery performance of a fixed-path metering and spacing system

    NASA Technical Reports Server (NTRS)

    Credeur, L.; Davis, C. M.; Capron, W. R.

    1981-01-01

    Metering and spacing (M & S) system's algorithms described assume an aircraft two dimensional are navigation capability. The three navigation systems compared were: very high frequency omnidirectional range/distance measuring equipment (VOR/DME) and ILS, VOR/DME and + or - 40 MLS, and VOR/DME and + or - 60 MLS. Other factors studied were M & S tentative schedule point location, route geometry effects, and approach gate location effects. Summarized results are: the MLS offers some improvement over VOR/DME and ILS if all approach routes contain computer assisted turns; pilot reaction to moving the gate closer to the runway threshold may adversely affect M & S performance; and coupling en route metering to terminal scheduling transfers most of the terminal holding to more full efficient, higher altitude en route delay.

  3. The vasomotor component of the orienting response in man related to spontaneous fluctuation of vasomotor activity in the acral skin zone.

    PubMed

    Kellerová, E; Ruttkay-Nedecký, I

    1978-10-01

    A plethymographic study of the effect of a weak indifferent light or sound stimulus and of a physically identical light stimulus with signal meaning on vasomotor activity in the acral skin zone of man has shown that during stimulus presentation there was a significant rise in the percent of occurrence of vasmotor waves corresponding to the criteria for the vasomotor orienting response (VOR). VOR is elicited significantly more often by stimuli with signal meaning than by physically identical indifferent stimuli. After the acute extinction or VOR disinhibition followed in all cases, and after 40--60 repeated stimuli the occurrence of VOR was still significant. Repeated stimuli had a significant effect on the course of the plethysmographic curve, especially on the component of waves of third order, changing the frequency spectrum and time contingency of waves.

  4. 76 FR 30534 - Standard Instrument Approach Procedures, and Takeoff Minimums and Obstacle Departure Procedures...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-05-26

    ... Procedures (44 FR 11034; February 26,1979); and (3) does not warrant preparation of a regulatory evaluation.... Timmerman, VOR RWY 15L, Amdt 14 Oconto, WI, J Douglas Bake Memorial, Takeoff Minimums and Obstacle DP,...

  5. Spatial Transformation of the Vestibulo-Ocular Reflex during Spaceflight

    NASA Technical Reports Server (NTRS)

    Clement, Gilles; Wood, Scott J.; Reschke, Millard F.

    1996-01-01

    It was hypothesized that the absence of the gravitational reference cues may be responsible for adaptive changes in the vestibulo-ocular reflex (VOR). These changes result in the alteration of the direction of the compensatory slow phase (SP) eye movements in microgravity. In order to test this hypothesis, the direction of the VOR SP relative to head motion was investigated in three astronauts during and after an eight-day orbital flight by passive sinusoidal pitch or yaw angular motion at two frequencies. The results of the inflight and postflight testing are considered. The observed deviation between VOR SP and head motion suggests that spatial transformation in the VOR occurred during adaptation to microgravity. It is considered that, although this spatial transformation might be due to a sensory bias, it may reflect central changes in the reference system used for spatial orientation in microgravity.

  6. Neural substrates underlying vestibular compensation: contribution of peripheral versus central processing.

    PubMed

    Cullen, Kathleen E; Minor, Lloyd B; Beraneck, Mathieu; Sadeghi, Soroush G

    2009-01-01

    The vestibulo-ocular reflex (VOR), which functions to stabilize gaze and ensure clear vision during everyday activities, shows impressive adaptation in response to environmental requirements. In particular, the VOR exhibits remarkable recovery following the loss of unilateral labyrinthine input as a result of injury or disease. The relative simplicity of the pathways that mediate the VOR, make it an excellent model system for understanding the changes (learning) that occur in the brain following peripheral vestibular loss to yield adaptive changes. This mini review considers the findings of behavioral, single unit recording and lesion studies of VOR compensation. Recent experiments have provided evidence that the brain makes use of multiple plasticity mechanisms (i.e., changes in peripheral as well as central processing) during the course of vestibular compensation to accomplish the sensory-motor transformations required to accurately guide behavior.

  7. 78 FR 64172 - Standard Instrument Approach Procedures, and Takeoff Minimums and Obstacle Departure Procedures...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-10-28

    ... ``significant rule'' under DOT Regulatory Policies and Procedures (44 FR 11034; February 26,1979); and (3) does... Muni, VOR/DME RWY 15, Amdt 8 Savanna, IL, Tri-Township, RNAV (GPS) RWY 13, Orig-A Rocky Mount,...

  8. Unfälle mit Pkw

    NASA Astrophysics Data System (ADS)

    Burg, Heinz

    Der Verkehrsunfall ereignete sich innerorts auf einer Kreuzung mit rechts vor links Regelung. Es galt dort die allgemeine Geschwindigkeitsbegrenzung auf 50 km/h. Zur Unfallzeit war es hell und trocken. Die Fahrbahn hatte eine Schwarzdecke.

  9. 14 CFR 105.3 - Definitions.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ...-23 series), or a personnel-carrying U.S. military parachute (other than a high altitude, high speed... World Aeronautical Chart or Sectional Aeronautical Chart, when the nearest VOR facility is more than...

  10. 76 FR 43580 - Standard Instrument Approach Procedures, and Takeoff Minimums and Obstacle Departure Procedures...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-07-21

    ... Policies and Procedures (44 FR 11034; February 26,1979); and (3) does not warrant preparation of a... Harbor, MI, Southwest Michigan Rgnl, VOR RWY 28, Amdt 19 Holland, MI, Tulip City, RNAV (GPS) RWY 8,...

  11. Modulation of the human vestibuloocular reflex during saccades: probing by high-frequency oscillation and torque pulses of the head.

    PubMed

    Tabak, S; Smeets, J B; Collewijn, H

    1996-11-01

    1. We probed the gain and phase of the vestibuloocular reflex (VOR) during the execution of voluntary gaze saccades, with continuous oscillation or acceleration pulses, applied through a torque helmet. 2. Small-amplitude (< 1 degree), high-frequency (10-14 Hz) head oscillations in the horizontal or vertical plane were superimposed on ongoing horizontal gaze saccades (40-100 degrees). Torque pulses to the head ("with" or "against" gaze) were superimposed on 40 degrees horizontal saccades. Eye and head movements were precisely measured with sensor coils in magnetic fields. 3. Techniques were developed to separate the oscillatory (horizontal or vertical) component from the gaze shift and obtain VOR gain and phase with Fourier techniques from the relation between eye-in-head and head oscillations. These involved either subtraction of exactly matching saccades with and without oscillation (drawback: low yield) or time shifting of successive trials to synchronize the oscillations (drawback: slight time blurring of saccades). 4. The results of these matching and synchronization methods were essentially identical and consistent. Presaccadic gain values of the horizontal VOR (typically about unity) were reduced by, on average, approximately 20 and 50% during horizontal saccades of 40 and 100 degrees, respectively. These percentages may be truncated because of methodological limitations, but even after taking these into account (on the basis of simulation experiments with 2 different, theoretical profiles of suppression) our results do not support a complete saccadic VOR suppression for any substantial fraction of saccadic duration. Qualitatively similar changes were found when the vertical VOR was probed during 100 degrees horizontal saccades. 5. Concomitantly with the reductions in gain, VOR phase was advanced by approximately 20 degrees during the saccade. 6. In the wake of gaze saccades, VOR gain was consistently elevated (to approximately 1.0) above the presaccadic

  12. An Investigation of Horizontal Combined Eye-Head Tracking in Patients with Abnormal Vestibular and Smooth Pursuit Eye Movements

    NASA Technical Reports Server (NTRS)

    Huebner, William P.; Leigh, R. John; Seidman, Scott H.; Billian, Carl

    1993-01-01

    We investigated the interaction of smooth ocular pursuit (SP) and the vestibulo-ocular reflex (VOR) during horizontal, combined eye-head tracking (CEHT) in patients with abnormalities of either the VOR or SP movements. Our strategy was to apply transient stimuli that capitalized on the different latencies to onset of SP and the VOR. During CEHT of a target moving at 15 deg/sec, normal subjects and patients with VOR deficits all tracked the target with a gain close to 1.O. When the heads of normal subjects were suddenly and unexpectedly braked to a halt during CEHT, the eye promptly began to move in the orbit to track the target, but eye-in-orbit velocity transiently fell to about 60-70% of target velocity. In patients with deficient labyrinthine function, following the onset of the head brake, eye movements to track the target were absent, and SP movements were not generated until about 100 msec later. In patients with deficient SP, CEHT was superior to SP tracking with the head stationary; after the onset of the head brake, tracking eye movements were initiated promptly, but eye velocity was less than 50% of target velocity and increased only slightly thereafter. These results indicate that at least two mechanisms operate to overcome the VOR and allow gaze to track the target during CEHT: (1) the SP system provides a signal to cancel a normally-operating VOR (this cancellation signal is not needed by labyrinthine-deficient patients who have no VOR to cancel), and (2) a reduction of the gain of the VOR is achieved, an ability that is preserved even in patients with cerebral lesions that impair SP.

  13. 76 FR 11944 - Standard Instrument Approach Procedures, and Takeoff Minimums and Obstacle Departure Procedures...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-03-04

    ... Policies and Procedures (44 FR 11034; February 26, 1979); and (3) does not warrant preparation of a... Isabel--Cameron 1/3406 2/7/11 VOR A, Amdt 6 County. 7-Apr-11 FL Apalachicola........ Apalachicola 1/3488...--Cameron 1/3668 2/8/11 VOR/DME B, Amdt 3 County. 7-Apr-11 CO Aspen Aspen-Pitkin Co/ 1/3699 2/7/11 LOC/DME...

  14. Vestibulo-ocular response and balance control in children and young adults with mild-to-moderate intellectual and developmental disability: a pilot study.

    PubMed

    Zur, Oz; Ronen, Ayelet; Melzer, Itshak; Carmeli, Eli

    2013-06-01

    The vestibulo-ocular response (VOR) may not be fully developed in children with an intellectual and developmental disability (IDD). This study aimed to identify the presence of VOR deficit in children and young adults with unspecified mild-to-moderate intellectual and developmental disability and its effect on balance control. Twenty-one children and young adults with IDD ranging in age from 8 to 22 years (mean 17.5 ± 3.9 years) were included in the study. The VOR was evaluated with the Head Impulse Test and the Static and Dynamic Visual Acuity Test (S&D-VAT). Postural stability was measured in an upright standing position by the Clinical Test for Sensory Interaction in Balance (CTSIB), single leg stance (SLS) during eyes open and eyes closed, and Romberg stance under eyes open and eyes closed conditions using a force platform. Reduced vestibulo-ocular responses were found in 13 of 21 (62%) participants who were able to complete testing. In the fifth condition of the CTSIB (standing on foam with eyes closed), those without VOR deficit were able to maintain balance longer than those with VOR deficit (29 s [median 30] vs. 12s [median 7.3], respectively; p=0.03). The study demonstrates potential effects of VOR deficit in children and young adults with IDD and some significant differences in balance control between those with and without a VOR deficit. VOR function in children and young adults with IDD should be routinely tested to enable early detection of deficits.

  15. Vestibulo-ocular reflex of the squirrel monkey during eccentric rotation with centripetal acceleration along the naso-occipital axis.

    PubMed

    Merfeld, D M

    1996-01-01

    The vestibulo-ocular reflexes (VOR) are determined not only by angular acceleration, but also by the presence of gravity and linear acceleration. This phenomenon was studied by measuring three-dimensional nystagmic eye movements, with implanted search coils, in four male squirrel monkeys. Monkeys were rotated in the dark at 200 degrees/s, centrally or 79 cm off-axis, with the axis of rotation always aligned with gravity and the spinal axis of the upright monkeys. The monkey's position relative to the centripetal acceleration (facing center or back to center) had a dramatic influence on the VOR. These studies show that a torsional response was always elicited that acted to shift the axis of eye rotation toward alignment with gravito-inertial force. On the other hand, a slow phase downward vertical response usually existed, which shifted the axis of eye rotation away from the gravito-inertial force. These findings were consistent across all monkeys. In another set of tests, the same monkeys were rapidly tilted about their interaural (pitch) axis. Tilt orientations of 45 degrees and 90 degrees were maintained for 1 min. Other than a compensatory angular VOR during the rotation, no consistent eye velocity response was ever observed during or following the tilt. The absence of any response following tilt proves that the observed torsional and vertical responses were not a positional nystagmus. Model simulations qualitatively predict all components of these eccentric rotation and tilt responses. These simulations support the conclusion that the VOR during eccentric rotation may consist of two components: a linear VOR and a rotational VOR. The model predicts a slow phase downward, vertical, linear VOR during eccentric rotation even though there was never a change in the force aligned with monkey's spinal (Z) axis. The model also predicts the torsional components of the response that shift the rotation axis of the angular VOR toward alignment with gravito-inertial force

  16. Behavioral analysis of signals that guide learned changes in the amplitude and dynamics of the vestibulo-ocular reflex

    NASA Technical Reports Server (NTRS)

    Raymond, J. L.; Lisberger, S. G.

    1996-01-01

    We characterized the dependence of motor learning in the monkey vestibulo-ocular reflex (VOR) on the duration, frequency, and relative timing of the visual and vestibular stimuli used to induce learning. The amplitude of the VOR was decreased or increased through training with paired head and visual stimulus motion in the same or opposite directions, respectively. For training stimuli that consisted of simultaneous pulses of head and target velocity 80-1000 msec in duration, brief stimuli caused small changes in the amplitude of the VOR, whereas long stimuli caused larger changes in amplitude as well as changes in the dynamics of the reflex. When the relative timing of the visual and vestibular stimuli was varied, brief image motion paired with the beginning of a longer vestibular stimulus caused changes in the amplitude of the reflex alone, but the same image motion paired with a later time in the vestibular stimulus caused changes in the dynamics as well as the amplitude of the VOR. For training stimuli that consisted of sinusoidal head and visual stimulus motion, low-frequency training stimuli induced frequency-selective changes in the VOR, as reported previously, whereas high-frequency training stimuli induced changes in the amplitude of the VOR that were more similar across test frequency. The results suggest that there are at least two distinguishable components of motor learning in the VOR. One component is induced by short-duration or high-frequency stimuli and involves changes in only the amplitude of the reflex. A second component is induced by long-duration or low-frequency stimuli and involves changes in the amplitude and dynamics of the VOR.

  17. Physik gestern und heute Von der Metallstange zum Hochenergielaser

    NASA Astrophysics Data System (ADS)

    Heering, Peter

    2002-05-01

    Im Mai 1752 wurde in Marly bei Paris auf Anregung des amerikanischen Forschers und Politikers Benjamin Franklin erstmals die elektrische Natur des Blitzes nachgewiesen. Damals beschrieb Franklin auch eine technische Vorrichtung, die als Schutz von Gebäuden vor Blitzschlägen dienen sollte: den Blitzableiter. Diese aus heutiger Sicht scheinbar triviale Vorrichtung wurde aber keineswegs unmittelbar akzeptiert. Und bis heute ist die Forschung zum Schutz von Einrichtungen vor Blitzschlägen nicht abgeschlossen.

  18. Vestibulo-ocular reflex of the squirrel monkey during eccentric rotation with centripetal acceleration along the naso-occipital axis

    NASA Technical Reports Server (NTRS)

    Merfeld, D. M.; Paloski, W. H. (Principal Investigator)

    1996-01-01

    The vestibulo-ocular reflexes (VOR) are determined not only by angular acceleration, but also by the presence of gravity and linear acceleration. This phenomenon was studied by measuring three-dimensional nystagmic eye movements, with implanted search coils, in four male squirrel monkeys. Monkeys were rotated in the dark at 200 degrees/s, centrally or 79 cm off-axis, with the axis of rotation always aligned with gravity and the spinal axis of the upright monkeys. The monkey's position relative to the centripetal acceleration (facing center or back to center) had a dramatic influence on the VOR. These studies show that a torsional response was always elicited that acted to shift the axis of eye rotation toward alignment with gravito-inertial force. On the other hand, a slow phase downward vertical response usually existed, which shifted the axis of eye rotation away from the gravito-inertial force. These findings were consistent across all monkeys. In another set of tests, the same monkeys were rapidly tilted about their interaural (pitch) axis. Tilt orientations of 45 degrees and 90 degrees were maintained for 1 min. Other than a compensatory angular VOR during the rotation, no consistent eye velocity response was ever observed during or following the tilt. The absence of any response following tilt proves that the observed torsional and vertical responses were not a positional nystagmus. Model simulations qualitatively predict all components of these eccentric rotation and tilt responses. These simulations support the conclusion that the VOR during eccentric rotation may consist of two components: a linear VOR and a rotational VOR. The model predicts a slow phase downward, vertical, linear VOR during eccentric rotation even though there was never a change in the force aligned with monkey's spinal (Z) axis. The model also predicts the torsional components of the response that shift the rotation axis of the angular VOR toward alignment with gravito-inertial force.

  19. Electrical Vestibular Stimulation after Vestibular Deafferentation and in Vestibular Schwannoma

    PubMed Central

    Aw, Swee Tin; Todd, Michael John; Lehnen, Nadine; Aw, Grace Elizabeth; Weber, Konrad Peter; Eggert, Thomas; Halmagyi, Gabor Michael

    2013-01-01

    Background Vestibular reflexes, evoked by human electrical (galvanic) vestibular stimulation (EVS), are utilized to assess vestibular function and investigate its pathways. Our study aimed to investigate the electrically-evoked vestibulo-ocular reflex (eVOR) output after bilateral and unilateral vestibular deafferentations to determine the characteristics for interpreting unilateral lesions such as vestibular schwannomas. Methods EVOR was recorded with dual-search coils as binocular three-dimensional eye movements evoked by bipolar 100 ms-step at EVS intensities of [0.9, 2.5, 5.0, 7.5, 10.0]mA and unipolar 100 ms-step at 5 mA EVS intensity. Five bilateral vestibular deafferented (BVD), 12 unilateral vestibular deafferented (UVD), four unilateral vestibular schwannoma (UVS) patients and 17 healthy subjects were tested with bipolar EVS, and five UVDs with unipolar EVS. Results After BVD, bipolar EVS elicited no eVOR. After UVD, bipolar EVS of one functioning ear elicited bidirectional, excitatory eVOR to cathodal EVS with 9 ms latency and inhibitory eVOR to anodal EVS, opposite in direction, at half the amplitude with 12 ms latency, exhibiting an excitatory-inhibitory asymmetry. The eVOR patterns from UVS were consistent with responses from UVD confirming the vestibular loss on the lesion side. Unexpectedly, unipolar EVS of the UVD ear, instead of absent response, evoked one-third the bipolar eVOR while unipolar EVS of the functioning ear evoked half the bipolar response. Conclusions The bidirectional eVOR evoked by bipolar EVS from UVD with an excitatory-inhibitory asymmetry and the 3 ms latency difference between normal and lesion side may be useful for detecting vestibular lesions such as UVS. We suggest that current spread could account for the small eVOR to 5 mA unipolar EVS of the UVD ear. PMID:24349188

  20. 76 FR 70055 - Standard Instrument Approach Procedures, and Takeoff Minimums and Obstacle Departure Procedures...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-11-10

    .../11 VOR RWY 28, Amdt 19 Rgnl. 15-Dec-11 CQ Agana Guam Intl 1/3566 9/30/11 VOR A, Orig-D 15-Dec-11 CQ... Policies and Procedures (44 FR 11034; February 26, 1979); and (3) does not warrant preparation of a...) Z RWY 24L, Orig-D 15-Dec-11 CA Oakland Metropolitan Oakland 1/0581 10/24/11 RNAV (RNP) Z RWY...

  1. Readaptation of the vestibuloocular reflex to 1g-Condition in immature lower vertebrates ( Xenopus laevis) after micro- or hypergravity exposure

    NASA Astrophysics Data System (ADS)

    Sebastian, C.; Horn, E.; Eβeling, K.; Neubert, J.

    The effects of altered gravitational conditions (AGC) on the development of the static vestibulo-ocular reflex (VOR) and readaptation to 1g were investigated in the amphibian Xenopus laevis. Tadpoles were exposed to microgravity (μg) during the German Space Mission D-2 for 10 days, using the STATEX closed survival system, or to 3g for 9 days during earth-bound experiments. At the beginning of AGC, the tadpoles had not yet developed the static VOR. The main results were: (i) Tadpoles with ug- or 3g-experience had a lower gain of the static VOR than the 1g-controls during the 2nd and 5th post-AGC days, (ii) Readaptation to response levels of 1g-reared controls usually occurred during the following weeks, except in slowly developing tadpoles with 3g-experience. Readaptation was less pronounced if, during the acute VOR test, tadpoles were rolled from the inclined to the normal posture than in the opposite test situation. It is postulated that (i) gravity is necessarily involved in the development of the static VOR, but only during a period including the time before onset of the first behavioural response; and (ii) readaptation which is superimposed by the processes of VOR development depends on many factors including the velocity of development, the actual excitation level of the vestibular systems and the neuroplastic properties of its specific pathways.

  2. Visual and vestibular determinants of the translational vestibulo-ocular reflex.

    PubMed

    Liao, Ke; Schneider, Rosalyn M; Yaniglos, Stacia S; Bertolini, Giovanni; Glendinning, Paul; Sawyer, Robert N; Reschke, Millard; Leigh, R John

    2011-09-01

    Prior studies indicate that the human translational vestibulo-ocular reflex (tVOR) generates eye rotations approximately half the magnitude required to keep the line of sight pointed at a stationary object--a compensation ratio (CR) of ∼0.5. We asked whether changes of visual or vestibular stimuli could increase the CR of tVOR. First, subjects viewed their environment through an optical device that required eye movements to increase by ∼50% to maintain fixation of a stationary visual target. During vertical translation, eye movements did increase, but tVOR CR remained at ∼0.5. Second, subjects viewed through LCD goggles providing 4 Hz strobe vision that minimized retinal image motion; this reduced tVOR CR. Finally, subjects were rotated in roll while they translated vertically; no increase in tVOR occurred. Taken with prior studies, we conclude that tVOR is optimally set to generate eye rotations that are about 50% of those required to stabilize the line of sight.

  3. A Reevaluation of the Vestibulo-Ocular Reflex: New Ideas of its Purpose, Properties, Neural Substrate, and Disorders

    NASA Technical Reports Server (NTRS)

    Leigh, R. John; Brandt, Thomas

    1992-01-01

    Conventional views of the Vestibulo-Ocular Reflex (VOR) have emphasized testing with caloric stimuli and by passively rotating patients at low frequencies in a chair. The properties of the VOR tested under these conditions differ from the performance of this reflex during the natural function for which it evolved-locomotion. Only the VOR (and not visually mediated eye movements) can cope with the high-frequency angular and linear perturbations of the head that occur during locomotion; this is achieved by generating eye movements at short latency (less than 16 msec). Interpretation of vestibular testing is enhanced by the realization that, although the di- and trisynaptic components of the VOR are essential for this short-latency response, the overall accuracy and plasticity of the VOR depend upon a distributed, parallel network of neurons involving the vestibular nuclei. Neurons in this network variously encode inputs from the labyrinthine semicircular canals and otoliths, as well as from the visual and somatosensory systems. The central vestibular pathways branch to contact vestibular cortex (for perception) and the spinal cord (for control of posture). Thus, the vestibular nuclei basically coordinate the stabilization of gaze and posture, and contribute to the perception of verticality and self-motion. Consequently, brainstem disorders that disrupt the VOR cause not just only nystagmus, but also instability of posture (eg, increased fore-aft sway in patients with downbeat nystagmus) and disturbance of spatial orientation (eg, tilt of the subjective visual vertical in Wallenberg's syndrome).

  4. Context-specific adaptation of the gain of the vestibulo-ocular reflex in humans.

    PubMed

    Shelhamer, M; Robinson, D A; Tan, H S

    1992-01-01

    Previous experiments show that altered visual feedback can change VOR gain. Such changes also presumably occur when eyeglasses are donned and doffed, or when bifocals are worn. In these cases, a nonvisual cue accompanies the required gain adjustment (frames on/off for eyeglasses, looking up/down for bifocals). We set out to show that a subject can establish two VOR gains, and to determine if one of the associated nonvisual cues alone is sufficient to subsequently determine which gain to employ. Each of three subjects sat in a rotating chair inside an OKN drum during 2 hours of sinusoidal rotation at 0.2 Hz, 30 degrees/s peak. For 10 minutes the chair and drum counterrotated , driving VOR gain toward 1.7, while subjects looked up 20 degrees. Chair and drum were then coupled for 10 minutes, driving gain toward zero, during which subjects looked down 20 degrees. This sequence was repeated for 2 hours. Immediately thereafter, VOR gains were measured while subjects looked alternately up and down, using 20 degrees to 40 degrees step rotations. A fixation target, presented before and after each step, provided accurate gain determination by measuring the size of the re-fixation saccade. Results show a consistent reduced VOR gain looking downward (average 6%) and increased gain looking upward (average 6%) and increased gain looking upward (average 8%). We conclude that humans can adjust their VOR gain dependent on a situational context; we speculate that this context can take many forms. PMID:1342386

  5. A prospective feasibility study of primary prophylaxis against invasive fungal disease with voriconazole following umbilical cord blood transplantation with fludarabine-based conditioning.

    PubMed

    Takagi, Shinsuke; Araoka, Hideki; Uchida, Naoyuki; Uchida, Yumiko; Kaji, Daisuke; Ota, Hikari; Nishida, Aya; Ishiwata, Kazuya; Tsuji, Masanori; Yamamoto, Hisashi; Ito, Tadaaki; Matsuno, Naofumi; Yamamoto, Go; Asano-Mori, Yuki; Hayashi, Masahiro; Izutsu, Koji; Masuoka, Kazuhiro; Wake, Atsushi; Makino, Shigeyoshi; Yoneyama, Akiko; Taniguchi, Shuichi

    2014-01-01

    Despite the recent introduction of a new class of anti-Aspergillus agents, no standard regimen for the prevention of invasive fungal disease (IFD) following allogeneic hematopoietic stem cell transplantation has been shown to be superior to fluconazole. The present prospective, single-arm study investigated the feasibility of voriconazole (VOR) administration as primary prophylaxis in 52 recipients of umbilical cord blood transplantation (CBT) with fludarabine-based conditioning, who had no previous IFD episodes. Proven or probable IFD was determined using the European Organization for Research and Treatment of Cancer/Invasive Fungal Infections Cooperative Group, and the National Institute of Allergy and Infectious Diseases Mycoses Study Group (EORTC/MSG) criteria were considered as breakthrough infections. VOR was administered as prophylaxis for a total of 6884 patient-days following CBT. The mean duration of VOR administration after transplantation was 132 days (range, 1-769); 44 patients (85 %) had advanced disease, 15 (29 %) had a history of allogeneic HSCT, and 29 (56 %) received systemic corticosteroid therapy for allogeneic immune-mediated complications. Under the prophylaxis with VOR, one patient developed probable invasive aspergillosis on day 71, and the cumulative incidence of IFD was 4.5 % at day 180. None of the patients developed breakthrough candida or zygomycetes infections. Under the extensive therapeutic dose monitoring, VOR was safely administered with a calcineurin inhibitor and was well tolerated. These results suggest that VOR represents a feasible primary prophylactic agent for IFD after CBT with fludarabine-based conditioning.

  6. Changes in gain of the vestibulo-ocular reflex induced by combined visual and vestibular stimulation in goldfish.

    PubMed

    Schairer, J O; Bennett, M V

    1986-05-14

    Adaptive changes in the vestibulo-ocular reflex (VOR) of goldfish were produced in a few hours by sinusoidally rotating restrained fish in the horizontal plane inside a vertically striped drum. The drum could also be sinusoidally rotated so that the gain of the VOR (the ratio of eye to head angular velocity) would have to increase to two or decrease to zero in order to maintain a stable retinal image. During 'training' towards two VOR gain measured at the stimulation frequency of 0.125 Hz increased rapidly over 6 h of stimulation to about 1.5 from an initial gain of 0.7. Half of that change occurred in the first 30 min. During training towards zero VOR gain measured at the stimulation frequency decreased to 0.15. About one-third of that change occurred in the first 30 min. Testing at different sinusoidal frequencies after 6 h stimulation showed that increases in VOR gain were generated across a 6-octave range; however, reductions in gain were produced over a narrow frequency range close to the training frequency. Gain reductions occurred more rapidly on a second day of stimulation. In a paradigm simulating reversing prisms, partial reversal of the VOR was observed in some fish. However, these fish also demonstrated spontaneous slow sinusoidal eye movements that may have represented a different means of adjusting eye movements to stabilize the retinal image. Goldfish provide a useful preparation for the study of adaptive gain changes in vertebrate oculomotor systems.

  7. Three-dimensional organization of otolith-ocular reflexes in rhesus monkeys. II. Inertial detection of angular velocity

    NASA Technical Reports Server (NTRS)

    Angelaki, D. E.; Hess, B. J.

    1996-01-01

    1. The dynamic contribution of otolith signals to three-dimensional angular vestibuloocular reflex (VOR) was studied during off-vertical axis rotations in rhesus monkeys. In an attempt to separate response components to head velocity from those to head position relative to gravity during low-frequency sinusoidal oscillations, large oscillation amplitudes were chosen such that peak-to-peak head displacements exceeded 360 degrees. Because the waveforms of head position and velocity differed in shape and frequency content, the particular head position and angular velocity sensitivity of otolith-ocular responses could be independently assessed. 2. During both constant velocity rotation and low-frequency sinusoidal oscillations, the otolith system generated two different types of oculomotor responses: 1) modulation of three-dimensional eye position and/or eye velocity as a function of head position relative to gravity, as presented in the preceding paper, and 2) slow-phase eye velocity as a function of head angular velocity. These two types of otolith-ocular responses have been analyzed separately. In this paper we focus on the angular velocity responses of the otolith system. 3. During constant velocity off-vertical axis rotations, a steady-state nystagmus was elicited that was maintained throughout rotation. During low-frequency sinusoidal off-vertical axis oscillations, dynamic otolith stimulation resulted primarily in a reduction of phase leads that characterize low-frequency VOR during earth-vertical axis rotations. Both of these effects are the result of an internally generated head angular velocity signal of otolithic origin that is coupled through a low-pass filter to the VOR. No change in either VOR gain or phase was observed at stimulus frequencies larger than 0.1 Hz. 4. The dynamic otolith contribution to low-frequency angular VOR exhibited three-dimensional response characteristics with some quantitative differences in the different response components. For

  8. Velocity storage in the human vertical rotational vestibulo-ocular reflex.

    PubMed

    Bertolini, G; Ramat, S

    2011-03-01

    Human horizontal rotational vestibulo-ocular reflex (rVOR) has been extensively investigated: the horizontal semicircular canals sense yaw rotations with high-pass filter dynamics and a time constant (TC) around 5 s, yet the rVOR response shows a longer TC due to a central processing stage, known as velocity storage mechanism (VSM). It is generally assumed that the vertical rVOR behaves similarly to the horizontal one; however, VSM processing of the human vertical rVOR is still to be proven. We investigated the vertical rVOR in eight healthy human subjects using three experimental paradigms: (1) per- and post-rotatory around an earth-vertical axis (ear down rotations, EDR), (2) post-rotatory around an earth-horizontal axis with different stopping positions (static otolith stimulation), (3) per-rotatory around an earth-horizontal axis (dynamic otolith stimulation). We found that the TC of vertical rVOR responses ranged 3-10 s, depending both on gravity and on the direction of rotation. The shortest TC were found in response to post-rotatory earth-horizontal stimulation averaging 3.6 s, while they were prolonged in EDR stimulation, i.e. when the head angular velocity vector is aligned with gravity, with a mean value of about 6.0 s. Overall, the longest TC were observed in per-rotatory earth-horizontal stimulation, averaging 7.8 s. The finding of longer TC in EDR than in post-rotatory earth-horizontal stimulation indicates a role for the VSM in the vertical rVOR, although its contribution appears to be weaker than on the horizontal rVOR and may be directionally asymmetric. The results from per-rotatory earth-horizontal stimulation, instead, imply a role for the otoliths in controlling the duration of the vertical rVOR response. We found no reorientation of the response toward earth horizontal, indicating a difference between human and monkey rVOR.

  9. Unilateral adaptation of the human angular vestibulo-ocular reflex.

    PubMed

    Migliaccio, Americo A; Schubert, Michael C

    2013-02-01

    A recent study showed that the angular vestibulo-ocular reflex (VOR) can be better adaptively increased using an incremental retinal image velocity error signal compared with a conventional constant large velocity-gain demand (×2). This finding has important implications for vestibular rehabilitation that seeks to improve the VOR response after injury. However, a large portion of vestibular patients have unilateral vestibular hypofunction, and training that raises their VOR response during rotations to both the ipsilesional and contralesional side is not usually ideal. We sought to determine if the vestibular response to one side could selectively be increased without affecting the contralateral response. We tested nine subjects with normal vestibular function. Using the scleral search coil and head impulse techniques, we measured the active and passive VOR gain (eye velocity / head velocity) before and after unilateral incremental VOR adaptation training, consisting of self-generated (active) head impulses, which lasted ≈ 15 min. The head impulses consisted of rapid, horizontal head rotations with peak-amplitude 15°, peak-velocity 150°/s and peak-acceleration 3,000°/s(2). The VOR gain towards the adapting side increased after training from 0.92 ± 0.18 to 1.11 ± 0.22 (+22.7 ± 20.2 %) during active head impulses and from 0.91 ± 0.15 to 1.01 ± 0.17 (+11.3 ± 7.5 %) during passive head impulses. During active impulses, the VOR gain towards the non-adapting side also increased by ≈ 8 %, though this increase was ≈ 70 % less than to the adapting side. A similar increase did not occur during passive impulses. This study shows that unilateral vestibular adaptation is possible in humans with a normal VOR; unilateral incremental VOR adaptation may have a role in vestibular rehabilitation. The increase in passive VOR gain after active head impulse adaptation suggests that the training effect is robust.

  10. Experimental tests of a superposition hypothesis to explain the relationship between the vestibuloocular reflex and smooth pursuit during horizontal combined eye-head tracking in humans

    NASA Technical Reports Server (NTRS)

    Huebner, W. P.; Leigh, R. J.; Seidman, S. H.; Thomas, C. W.; Billian, C.; DiScenna, A. O.; Dell'Osso, L. F.

    1992-01-01

    1. We used a modeling approach to test the hypothesis that, in humans, the smooth pursuit (SP) system provides the primary signal for cancelling the vestibuloocular reflex (VOR) during combined eye-head tracking (CEHT) of a target moving smoothly in the horizontal plane. Separate models for SP and the VOR were developed. The optimal values of parameters of the two models were calculated using measured responses of four subjects to trials of SP and the visually enhanced VOR. After optimal parameter values were specified, each model generated waveforms that accurately reflected the subjects' responses to SP and vestibular stimuli. The models were then combined into a CEHT model wherein the final eye movement command signal was generated as the linear summation of the signals from the SP and VOR pathways. 2. The SP-VOR superposition hypothesis was tested using two types of CEHT stimuli, both of which involved passive rotation of subjects in a vestibular chair. The first stimulus consisted of a "chair brake" or sudden stop of the subject's head during CEHT; the visual target continued to move. The second stimulus consisted of a sudden change from the visually enhanced VOR to CEHT ("delayed target onset" paradigm); as the vestibular chair rotated past the angular position of the stationary visual stimulus, the latter started to move in synchrony with the chair. Data collected during experiments that employed these stimuli were compared quantitatively with predictions made by the CEHT model. 3. During CEHT, when the chair was suddenly and unexpectedly stopped, the eye promptly began to move in the orbit to track the moving target. Initially, gaze velocity did not completely match target velocity, however; this finally occurred approximately 100 ms after the brake onset. The model did predict the prompt onset of eye-in-orbit motion after the brake, but it did not predict that gaze velocity would initially be only approximately 70% of target velocity. One possible

  11. Transactivation of bad by vorinostat-induced acetylated p53 enhances doxorubicin-induced cytotoxicity in cervical cancer cells.

    PubMed

    Lee, Sook-Jeong; Hwang, Sung-Ook; Noh, Eun Joo; Kim, Dong-Uk; Nam, Miyoung; Kim, Jong Hyeok; Nam, Joo Hyun; Hoe, Kwang-Lae

    2014-02-14

    Vorinostat (VOR) has been reported to enhance the cytotoxic effects of doxorubicin (DOX) with fewer side effects because of the lower DOX dosage in breast cancer cells. In this study, we investigated the novel mechanism underlying the synergistic cytotoxic effects of VOR and DOX co-treatment in cervical cancer cells HeLa, CaSki and SiHa cells. Co-treatment with VOR and DOX at marginal doses led to the induction of apoptosis through caspase-3 activation, poly (ADP-ribose) polymerase cleavage and DNA micronuclei. Notably, the synergistic growth inhibition induced by the co-treatment was attributed to the upregulation of the pro-apoptotic protein Bad, as the silencing of Bad expression using small interfering RNA (siRNA) abolished the phenomenon. As siRNA against p53 did not result in an increase in acetylated p53 and the consequent upregulation of Bad, the observed Bad upregulation was mediated by acetylated p53. Moreover, a chromatin immunoprecipitation analysis showed that the co-treatment of HeLa cells with VOR and DOX increased the recruitment of acetylated p53 to the bad promoter, with consequent bad transactivation. Conversely, C33A cervical cancer cells containing mutant p53 co-treated with VOR and DOX did not exhibit Bad upregulation, acetylated p53 induction or consequent synergistic growth inhibition. Together, the synergistic growth inhibition of cervical cancer cell lines induced by co-treatment with VOR and DOX can be attributed to the upregulation of Bad, which is induced by acetylated p53. These results show for the first time that the acetylation of p53, rather than histones, is a mechanism for the synergistic growth inhibition induced by VOR and DOX co-treatments.

  12. Three-dimensional ocular kinematics during eccentric rotations: evidence for functional rather than mechanical constraints

    NASA Technical Reports Server (NTRS)

    Angelaki, Dora E.

    2003-01-01

    Previous studies have reported that the translational vestibuloocular reflex (TVOR) follows a three-dimensional (3D) kinematic behavior that is more similar to visually guided eye movements, like pursuit, rather than the rotational VOR (RVOR). Accordingly, TVOR rotation axes tilted with eye position toward an eye-fixed reference frame rather than staying relatively fixed in the head like in the RVOR. This difference arises because, contrary to the RVOR where peripheral image stability is functionally important, the TVOR like pursuit and saccades cares to stabilize images on the fovea. During most natural head and body movements, both VORs are simultaneously activated. In the present study, we have investigated in rhesus monkeys the 3D kinematics of the combined VOR during yaw rotation about eccentric axes. The experiments were motivated by and quantitatively compared with the predictions of two distinct hypotheses. According to the first (fixed-rule) hypothesis, an eye-position-dependent torsion is computed downstream of a site for RVOR/TVOR convergence, and the combined VOR axis would tilt through an angle that is proportional to gaze angle and independent of the relative RVOR/TVOR contributions to the total eye movement. This hypothesis would be consistent with the recently postulated mechanical constraints imposed by extraocular muscle pulleys. According to the second (image-stabilization) hypothesis, an eye-position-dependent torsion is computed separately for the RVOR and the TVOR components, implying a processing that takes place upstream of a site for RVOR/TVOR convergence. The latter hypothesis is based on the functional requirement that the 3D kinematics of the combined VOR should be governed by the need to keep images stable on the fovea with slip on the peripheral retina being dependent on the different functional goals of the two VORs. In contrast to the fixed-rule hypothesis, the data demonstrated a variable eye-position-dependent torsion for the

  13. Age-related changes in human vestibulo-ocular reflexes: Sinusoidal rotation and caloric tests

    NASA Technical Reports Server (NTRS)

    Peterka, R. J.; Black, F. O.; Schoenhoff, M. B.

    1989-01-01

    The dynamic response properties of horizontal vestibulo-ocular reflex (VOR) were characterized in 216 human subjects ranging in age from 7 to 81 years. The object of this cross-sectional study was to determine the effects of aging on VOR dynamics, and to identify the distributions of parameters which describe VOR responses to caloric and to sinusoidal rotational stimuli in a putatively normal population. Caloric test parameters showed no consistent trend with age. Rotation test parameters showed declining response amplitude and slightly less compensatory response phase with increasing age. The magnitudes of these changes were not large relative to the variability within the population. The age-related trends in VOR were not consistent with the anatomic changes in the periphery reported by others which showed an increasing rate of peripheral hair cell and nerve fiber loss in subjects over 55 years. The poor correlation between physiological and anatomical data suggest that adaptive mechanisms in the central nervous system are important in maintaining the VOR.

  14. Influence of stimulus interval on the habituation of vestibulo-ocular reflex and sensation of rotation in humans.

    PubMed

    Clément, Gilles; Tilikete, Caroline; Courjon, Jean-Hubert

    2013-08-01

    Previous studies in cats revealed that vestibular habituation of the vestibulo-ocular reflex (VOR) only occurs when velocity steps are delivered during the secondary phase nystagmus, suggesting that the presence of anti-compensatory slow phases may trigger the habituation process. We verified this property in humans by comparing vestibular habituation of VOR and sensation of rotation when steps were delivered either immediately after the perception of self-rotation had stopped, which is shortly before the nystagmus reverses direction; or when steps were delivered 60s later, i.e. during the secondary phase. Vestibular habituation of the VOR occurred in both instances. However, the decrease in VOR peak slow phase velocity and time constant was larger when steps were delivered after nystagmus reversal compared to before nystagmus reversal. The duration of the perception of self-rotation habituated equally for both conditions. These results confirm that VOR habituation fully develops only when velocity steps are delivered after the primary phase nystagmus. This finding may be helpful for minimizing the impact of repetitive vestibular stimuli in protocols using crossover design for drug studies, testing recovery in vestibular patients, or training people for different gravitoinertial environments.

  15. Influence of gravity on cat vertical vestibulo-ocular reflex

    NASA Technical Reports Server (NTRS)

    Tomko, D. L.; Wall, C., III; Robinson, F. R.; Staab, J. P.

    1988-01-01

    The vertical vestibulo-ocular reflex (VOR) was recorded in cats using electro-oculography during sinusoidal angular pitch. Peak stimulus velocity was 50 deg/s over a frequency range from 0.01 to 4.0 Hz. To test the effect of gravity on the vertical VOR, the animal was pitched while sitting upright or lying on its side. Upright pitch changed the cat's orientation relative to gravity, while on-side pitch did not. The cumulative slow component position of the eye during on-side pitch was less symmetric than during upright pitch. Over the mid-frequency range (0.1 to 1.0 Hz), the average gain of the vertical VOR was 14.5 percent higher during upright pitch than during on-side pitch. At low frequencies (less than 0.05 Hz) changing head position relative to gravity raised the vertical VOR gain and kept the reflex in phase with stimulus velocity. These results indicate that gravity-sensitive mechanisms make the vertical VOR more compensatory.

  16. Vergence-dependent adaptation of the vestibulo-ocular reflex

    NASA Technical Reports Server (NTRS)

    Lewis, Richard F.; Clendaniel, Richard A.; Zee, David S.; Shelhamer, M. J. (Principal Investigator)

    2003-01-01

    The gain of the vestibulo-ocular reflex (VOR) normally depends on the distance between the subject and the visual target, but it remains uncertain whether vergence angle can be linked to changes in VOR gain through a process of context-dependent adaptation. In this study, we examined this question with an adaptation paradigm that modified the normal relationship between vergence angle and retinal image motion. Subjects were rotated sinusoidally while they viewed an optokinetic (OKN) stimulus through either diverging or converging prisms. In three subjects the diverging prisms were worn while the OKN stimulus moved out of phase with the head, and the converging prisms were worn when the OKN stimulus moved in-phase with the head. The relationship between the vergence angle and OKN stimulus was reversed in the fourth subject. After 2 h of training, the VOR gain at the two vergence angles changed significantly in all of the subjects, evidenced by the two different VOR gains that could be immediately accessed by switching between the diverged and converged conditions. The results demonstrate that subjects can learn to use vergence angle as the contextual cue that retrieves adaptive changes in the angular VOR.

  17. Generalized Hamiltonian point vortex dynamics on arbitrary domains using the method of fundamental solutions

    NASA Astrophysics Data System (ADS)

    Ashbee, T. L.; Esler, J. G.; McDonald, N. R.

    2013-08-01

    A new algorithm (VOR-MFS) is presented for the solution of a generalized Hamiltonian model of point vortex dynamics in an arbitrary two-dimensional computational domain. The VOR-MFS algorithm utilizes the method of fundamental solutions (MFS) to obtain an approximation to the model Hamiltonian by solution of an appropriate boundary value problem. Unlike standard point vortex methods, VOR-MFS requires knowledge only of the free-space (R2) Green's function for the problem as opposed to the domain-adapted Green's function, permitting solution of a much wider range of problems. VOR-MFS is first validated against a vortex image model for the case of (2D Euler) multiple vortex motion in both circular and 'Neumann-oval' shaped domains. It is then demonstrated that VOR-MFS can solve for quasi-geostrophic shallow water point vortex motion in the same domains. The exponential convergence of the MFS method is shown to lead to good conservation properties for each of the solutions presented.

  18. Signals and learning rules guiding oculomotor plasticity.

    PubMed

    Shin, Soon-Lim; Zhao, Grace Q; Raymond, Jennifer L

    2014-08-01

    The learning of motor skills is thought to occur largely through trial and error; however, the error signals and rules controlling the induction of motor learning have not been fully elucidated. We evaluated the learning rules that translate the sensory and motor cues available during training into learned changes in the gain and phase of the vestibulo-ocular reflex (VOR) of mice. Contrary to previous theories, neither the phase of retinal image motion relative to head motion nor the phase of retinal image motion relative to eye movement could consistently predict the direction of the learned change in the gain of the VOR across all training conditions tested. Instead, the phase of the gaze movement relative to head motion during training was the best predictor of whether learning would increase or decrease the gain of the VOR. Learned changes in the phase of the VOR were best predicted by a different cue--the phase of the eye movement relative to head motion during training. These results provide new constraints on the neural mechanisms implementing the adaptive calibration of the VOR by cerebellum-dependent motor learning.

  19. Integument und Anhangsorgane

    NASA Astrophysics Data System (ADS)

    Schliemann, Harald

    Das Integument umhüllt den Wirbeltierkörper lückenlos. In der embryonalen Mundbucht (Stomodaeum) und der Afterbucht (Proctodaeum) grenzt es an die Auskleidung des Darmrohres. Über die generelle Bedeutung einer Haut als Abgrenzung zwischen Körperinnenraum und Außenmedium hinaus hat es bei Schädeltieren ein breites Spektrum von Funktionen. Die wichtigsten sind: Mechanischer Schutz durch Verhornungen und Verknöch erungen; Wundheilung; Schutz vor Wasserverlust; Schutz vor Infektionen durch bakterizide Drüsensekrete und immunkompetente Zellen; Schutz vor kurzwelliger Strahlung durch Pigmente; Schutz vor Überwärmung durch Schweißdrüsensekrete und Schutz vor Wärmeverlust durch Federn und Haare; Ausbildung lokomotorisch wichtiger Strukturen wie Federn, Flug- und Schwimmhäute, Krallen und Hufe; Redukt ion des Strömungswiderstandes durch Dämpfungshaut; Abgabe von Sekreten zur Ernährung (Milch); Ausbildung von Strukturen zu Nahrungserwerb und_-bearbeitung, z. B. Zähne, Barten;

  20. What is the minimal vestibular function required for compensation?

    NASA Technical Reports Server (NTRS)

    Black, F. O.; Wade, S. W.; Nashner, L. M.

    1996-01-01

    Living with an uncompensated, abnormal vestibular system requires oppressive modification of life style and often prevents return to work and activities of daily living. Patients with vestibular abnormalities were studied to determine the minimal residual vestibular function required to achieve compensation. Three groups of patients with (a) complete unilateral loss of vestibular function with normal horizontal canal-vestibulo-ocular (HCVOR) function in the opposite ear, (b) complete unilateral loss with abnormal HCVOR function in the opposite ear, and (c) bilateral reduction of vestibular function from aminoglycoside toxicity underwent vestibuloocular (VOR), optokinetic (OKN), visual-VOR (VVOR), and computerized dynamic posturography (CDP) tests before and after therapeutic procedures. Results suggest that a minimal VOR response amplitude must be present for compensation of VVOR function to occur. The roles of VOR and OKN phase shifts in vestibular compensation are more complicated and require further study. Compensation of vestibulospinal function does not necessarily accompany VOR or VVOR compensation. Ascending and descending vestibular compensatory mechanisms may involve different spatial sensory inputs. Results of these studies have important implications for the diagnosis and treatment of patients with vestibular disorders, including selection and monitoring of patients for therapeutic regimens such as vestibular nerve section and streptomycin therapy.

  1. Vestibulo-ocular responses evoked via bilateral electrical stimulation of the lateral semicircular canals

    PubMed Central

    Gong, Wangsong; Haburcakova, Csilla; Merfeld, Daniel M.

    2008-01-01

    We investigated the vestibulo-ocular responses (VOR) evoked by bilateral electrical stimulation of the nerves innervating horizontal semicircular canals in squirrel monkeys and compared these responses to those evoked by unilateral stimulation. In response to sinusoidal modulation of the electrical pulse rate, the VOR for bilateral stimulation roughly equals the addition of the responses evoked by unilateral right ear and unilateral left ear stimulation; the VOR time constants were about the same for bilateral and unilateral stimulation and both were much shorter than for normal animals. In response to individual pulse stimulation, the VOR evoked by bilateral stimulation closely matches the point-by-point addition of responses evoked by unilateral right ear and unilateral left ear stimulation. We conclude that, to first order, the VOR responses evoked by bilateral stimulation are the summation of the responses evoked by unilateral stimulation. These findings suggest that – from a physiologic viewpoint – unilateral and bilateral vestibular prostheses are about equally viable. Given these findings, one possible advantage of a bilateral prosthesis is higher gain. However, at least for short-term stimulation like that studied herein, no inherent advantage in terms of the response time constant (“velocity storage”) was found. PMID:18990631

  2. Note: high frequency vibration rejection using a linear shaft actuator-based image stabilizing device via vestibulo-ocular reflex adaptation control method.

    PubMed

    Koh, Doo-Yeol; Kim, Young-Kook; Kim, Kyung-Soo; Kim, Soohyun

    2013-08-01

    In mobile robotics, obtaining stable image of a mounted camera is crucial for operating a mobile system to complete given tasks. This note presents the development of a high-speed image stabilizing device using linear shaft actuator, and a new image stabilization method inspired by human gaze stabilization process known as vestibulo-ocular reflex (VOR). In the proposed control, the reference is adaptively adjusted by the VOR adaptation control to reject residual vibration of a camera as the VOR gain converges to optimal state. Through experiments on a pneumatic vibrator, it will be shown that the proposed system is capable of stabilizing 10 Hz platform vibration, which shows potential applicability of the device to a high-speed mobile robot.

  3. Note: High frequency vibration rejection using a linear shaft actuator-based image stabilizing device via vestibulo-ocular reflex adaptation control method

    NASA Astrophysics Data System (ADS)

    Koh, Doo-Yeol; Kim, Young-Kook; Kim, Kyung-Soo; Kim, Soohyun

    2013-08-01

    In mobile robotics, obtaining stable image of a mounted camera is crucial for operating a mobile system to complete given tasks. This note presents the development of a high-speed image stabilizing device using linear shaft actuator, and a new image stabilization method inspired by human gaze stabilization process known as vestibulo-ocular reflex (VOR). In the proposed control, the reference is adaptively adjusted by the VOR adaptation control to reject residual vibration of a camera as the VOR gain converges to optimal state. Through experiments on a pneumatic vibrator, it will be shown that the proposed system is capable of stabilizing 10 Hz platform vibration, which shows potential applicability of the device to a high-speed mobile robot.

  4. Voluntary presetting of the vestibular ocular reflex permits gaze stabilization despite perturbation of fast head movements

    NASA Technical Reports Server (NTRS)

    Zangemeister, Wolfgang H.

    1989-01-01

    Normal subjects are able to change voluntarily and continuously their head-eye latency together with their compensatory eye movement gain. A continuous spectrum of intent-latency modes of the subject's coordinated gaze through verbal feedback could be demonstrated. It was also demonstrated that the intent to counteract any perturbation of head-eye movement, i.e., the mental set, permitted the subjects to manipulate consciously their vestibular ocular reflex (VOR) gain. From the data, it is inferred that the VOR is always on. It may be, however, variably suppressed by higher cortical control. With appropriate training, head-mounted displays should permit an easy VOR presetting that leads to image stabilization, perhaps together with a decrease of possible misjudgements.

  5. The horizontal angular vestibulo-ocular reflex: a nonlinear mechanism for context-dependent responses.

    PubMed

    Ranjbaran, Mina; Galiana, Henrietta L

    2013-11-01

    Studies of the vestibulo-ocular reflex (VOR) have revealed that this type of involuntary eye movement is influenced by viewing distance. This paper presents a bilateral model for the horizontal angular VOR in the dark based on realistic physiological mechanisms. It is shown that by assigning proper nonlinear neural computations at the premotor level, the model is capable of replicating target-distance-dependent VOR responses that are in agreement with geometrical requirements. Central premotor responses in the model are also shown to be consistent with experimental observations. Moreover, the model performance after simulated unilateral canal plugging also reproduces experimental observations, an emerging property. Such local nonlinear computations could similarly generate context-dependent behaviors in other more complex motor systems.

  6. High-fidelity pulse density modulation in neuromorphic electric circuits utilizing natural heterogeneity

    NASA Astrophysics Data System (ADS)

    Utagawa, Akira; Asai, Tetsuya; Amemiya, Yoshihito

    Hospedales et al. have recently proposed a neural network model of the “vestibulo-ocular reflex” (VOR) in which a common input was given to multiple nonidentical spiking neurons that were exposed to uncorrelated temporal noise, and the output was represented by the sum of these neurons. Although the function of the VOR network is equivalent to pulse density modulation, the neurons' non-uniformity and temporal noises given to the neurons were shown to improve the output spike's fidelity to the analog input. In this paper, we propose a CMOS analog circuit for implementing the VOR network that exploits the non-uniformity of real MOS devices. Through extensive laboratory experiments using discrete MOS devices, we show that the output's fidelity to the input pulses is clearly improved by using multiple neuron circuits, in which the non-uniformity is naturally embedded into the devices.

  7. Note: high frequency vibration rejection using a linear shaft actuator-based image stabilizing device via vestibulo-ocular reflex adaptation control method.

    PubMed

    Koh, Doo-Yeol; Kim, Young-Kook; Kim, Kyung-Soo; Kim, Soohyun

    2013-08-01

    In mobile robotics, obtaining stable image of a mounted camera is crucial for operating a mobile system to complete given tasks. This note presents the development of a high-speed image stabilizing device using linear shaft actuator, and a new image stabilization method inspired by human gaze stabilization process known as vestibulo-ocular reflex (VOR). In the proposed control, the reference is adaptively adjusted by the VOR adaptation control to reject residual vibration of a camera as the VOR gain converges to optimal state. Through experiments on a pneumatic vibrator, it will be shown that the proposed system is capable of stabilizing 10 Hz platform vibration, which shows potential applicability of the device to a high-speed mobile robot. PMID:24007125

  8. Alexander's law during high-acceleration head rotations in humans.

    PubMed

    Anagnostou, Evangelos; Heimberger, Joachim; Sklavos, Sokratis; Anastasopoulos, Dimitri

    2011-03-30

    Alexander's law states that the amplitude of the spontaneous nystagmus grows with increasing gaze in the direction of the fast phase. Using the search-coil method we employed head impulses at various eye-in-orbit azimuth angles to test (i) whether the normal vestibulo-ocular reflex (VOR) in the behaviorally relevant high-frequency range has intrinsic properties that could account for Alexander's law and (ii) whether such properties can also be shown in patients with unilateral vestibulopathy. We showed that the gain of the VOR remained unaffected by eye-in-orbit position in contols and in patients, both on ipsilesional and contralesional stimuli. These findings suggest that eye-in-orbit position does not directly modulate the activity in VOR pathways, neither during unbalanced but reciprocal (in controls), nor during unbalanced and nonreciprocal natural vestibular stimulation (in patients).

  9. Herausforderungen für künftige Lernumgebungen am Beispiel der Fakultät für Medizin

    NASA Astrophysics Data System (ADS)

    Gergintchev, Ivan; Graf, Stephan

    Nach der weit reichenden Etablierung von eLearning in den letzten Jahren stehen nahezu alle deutschen Hochschulen vor der Aufgabe, wettbewerbsfähige hochschulübergreifende Mechanismen sowie entsprechende organisatorische Rahmenbedingungen zu schaffen. Vor allem die Umsetzung von EBologna und die Unterstützung kooperativer Bildungsangebote verstärken diese Notwendigkeit. Motiviert durch die Veränderungen im Bereich der Hochschullehre und die Herausforderungen für künftige Lernumgebungen schlagen wir eine Integrationslösung im Sinne eines Learning Gateway vor, die zur webgestützten Abwicklung von kooperativen Bildungsangeboten in heterogen Lernumgebungen eingesetzt werden kann. Ihre Praxisanwendung verdeutlichen wir anschließend im komplexen Szenario der Medizin an der TUM. Die Evaluierung der Umsetzung belegt den deutlichen Mehrwert des Ansatzes.

  10. Eye and head motion during head turns in spaceflight

    NASA Technical Reports Server (NTRS)

    Thornton, William E.; Uri, John J.; Moore, Thomas P.; Pool, Sam L.

    1988-01-01

    Eye-head motion was studied pre-, in- and postflight during single voluntary head turns. A transient increase in vestibulo-ocular reflex (VOR) gain occurred early in the flight, but later trended toward normal. This increased gain was produced by a relative increase in eye counterrotation velocity. Asymmetries in gain with right and left turns also occurred, caused by asymmetries in eye counterrotation velocities. These findings were remarkably similar to those from Soviet primate studies using gaze fixation targets, except the human study trended more rapidly toward normal. These findings differ substantially from those measuring VOR gain by head oscillation, in which no significant changes were found inflight. No visual disturbances were noted in either test condition or in normal activities. These head turn studies are the only ones to date documenting any functional change in VOR in weightlessness.

  11. Comparison of smooth pursuit and combined eye-head tracking in human subjects with deficient labyrinthine function

    NASA Technical Reports Server (NTRS)

    Leigh, R. J.; Thurston, S. E.; Sharpe, J. A.; Ranalli, P. J.; Hamid, M. A.

    1987-01-01

    The effects of deficient labyrinthine function on smooth visual tracking with the eyes and head were investigated, using ten patients with bilateral peripheral vestibular disease and ten normal controls. Active, combined eye-head tracking (EHT) was significantly better in patients than smooth pursuit with the eyes alone, whereas normal subjects pursued equally well in both cases. Compensatory eye movements during active head rotation in darkness were always less in patients than in normal subjects. These data were used to examine current hypotheses that postulate central cancellation of the vestibulo-ocular reflex (VOR) during EHT. A model that proposes summation of an integral smooth pursuit command and VOR/compensatory eye movements is consistent with the findings. Observation of passive EHT (visual fixation of a head-fixed target during en bloc rotation) appears to indicate that in this mode parametric gain changes contribute to modulation of the VOR.

  12. Density and success of bird nests relative to grazing on western Montana grasslands

    USGS Publications Warehouse

    Fondell, T.F.; Ball, I.J.

    2004-01-01

    Grassland birds are declining at a faster rate than any other group of North American bird species. Livestock grazing is the primary economic use of grasslands in the western United States, but the effects of this use on distribution and productivity of grassland birds are unclear. We examined nest density and success of ground-nesting birds on grazed and ungrazed grasslands in western Montana. In comparison to grazed plots, ungrazed plots had reduced forb cover, increased litter cover, increased litter depth, and increased visual obstruction readings (VOR) of vegetation. Nest density among 10 of 11 common bird species was most strongly correlated with VOR of plots, and greatest nest density for each species occured where mean VOR of the plot was similar to mean VOR at nests. Additionally, all bird species were relatively consistent in their choice of VOR at nests despite substantial differences in VOR among plots. We suggest that birds selected plots based in part on availability of suitable nest sites and that variation in nest density relative to grazing reflected the effect of grazing on availability of nest sites. Nest success was similar between grazed plots and ungrazed plots for two species but was lower for nests on grazed plots than on ungrazed plots for two other species because of increased rates of predation, trampling, or parasitism by brown-headed cowbirds (Molothrus ater). Other species nested almost exclusively on ungrazed plots (six species) or grazed plots (one species), precluding evaluation of the effects of grazing on nest success. We demonstrate that each species in a diverse suite of ground-nesting birds preferentially used certain habitats for nesting and that grazing altered availability of preferred nesting habitats through changes in vegetation structure and plant species composition. We also show that grazing directly or indirectly predisposed some bird species to increased nesting mortality. Management alternatives that avoid intensive

  13. Velocity-selective adaptation of the horizontal and cross-axis vestibulo-ocular reflex in the mouse.

    PubMed

    Hübner, Patrick P; Khan, Serajul I; Migliaccio, Americo A

    2014-10-01

    One commonly observed phenomenon of vestibulo-ocular reflex (VOR) adaptation is a frequency-selective change in gain (eye velocity/head velocity) and phase (relative timing between the vestibular stimulus and response) based on the frequency content of the adaptation training stimulus. The neural mechanism behind this type of adaptation is not clear. Our aim was to determine whether there were other parameter-selective effects on VOR adaptation, specifically velocity-selective and acceleration-selective changes in the horizontal VOR gain and phase. We also wanted to determine whether parameter selectivity was also in place for cross-axis adaptation training (a visual-vestibular training stimulus that elicits a vestibular-evoked torsional eye movement during horizontal head rotations). We measured VOR gain and phase in 17 C57BL/6 mice during baseline (no adaptation training) and after gain-increase, gain-decrease and cross-axis adaptation training using a sinusoidal visual-vestibular (mismatch) stimulus with whole-body rotations (vestibular stimulus) with peak velocity 20 and 50°/s both with a fixed frequency of 0.5 Hz. Our results show pronounced velocity selectivity of VOR adaptation. The difference in horizontal VOR gain after gain-increase versus gain-decrease adaptation was maximal when the sinusoidal testing stimulus matched the adaptation training stimulus peak velocity. We also observed similar velocity selectivity after cross-axis adaptation training. Our data suggest that frequency selectivity could be a manifestation of both velocity and acceleration selectivity because when one of these is absent, e.g. acceleration selectivity in the mouse, frequency selectivity is also reduced.

  14. Prolonged vestibular stimulation induces homeostatic plasticity of the vestibulo-ocular reflex in larval Xenopus laevis.

    PubMed

    Dietrich, Haike; Straka, Hans

    2016-07-01

    Vestibulo-ocular reflexes (VOR) stabilise retinal images during head/body motion in vertebrates by generating spatio-temporally precise extraocular motor commands for corrective eye movements. While VOR performance is generally robust with a relatively stable gain, cerebellar circuits are capable of adapting the underlying sensory-motor transformation. Here, we studied cerebellum-dependent VOR plasticity by recording head motion-induced lateral rectus and superior oblique extraocular motor discharge in semi-intact preparations of Xenopus laevis tadpoles. In the absence of visual feedback, prolonged sinusoidal rotation caused either an increase or decrease of the VOR gain depending on the motion stimulus amplitude. The observed changes in extraocular motor discharge gradually saturated after 20 min of constant rotation and returned to baseline in the absence of motion stimulation. Furthermore, plastic changes in lateral rectus and superior oblique motor commands were plane-specific for horizontal and vertical rotations, respectively, suggesting that alterations are restricted to principal VOR connections. Comparison of multi- and single-unit activity indicated that plasticity occurs in all recorded units of a given extraocular motor nucleus. Ablation of the cerebellum abolished motoneuronal gain changes and prevented the induction of plasticity, thus demonstrating that both acquisition and retention of this type of plasticity require an intact cerebellar circuitry. In conclusion, the plane-specific and stimulus intensity-dependent modification of the VOR gain through the feed-forward cerebellar circuitry represents a homeostatic plasticity that likely maintains an optimal working range for the underlying sensory-motor transformation.

  15. The mammalian efferent vestibular system plays a crucial role in the high-frequency response and short-term adaptation of the vestibuloocular reflex.

    PubMed

    Hübner, Patrick P; Khan, Serajul I; Migliaccio, Americo A

    2015-12-01

    Although anatomically well described, the functional role of the mammalian efferent vestibular system (EVS) remains unclear. Unlike in fish and reptiles, the mammalian EVS does not seem to play a role in modulation of primary afferent activity in anticipation of active head movements. However, it could play a role in modulating long-term mechanisms requiring plasticity such as vestibular adaptation. We measured the efficacy of vestibuloocular reflex (VOR) adaptation in α9-knockout mice. These mice carry a missense mutation of the gene encoding the α9 nicotinic acetylcholine receptor (nAChR) subunit. The α9 nAChR subunit is expressed in the vestibular and auditory periphery, and its loss of function could compromise peripheral input from the predominantly cholinergic EVS. We measured the VOR gain (eye velocity/head velocity) in 26 α9-knockout mice and 27 cba129 control mice. Mice were randomly assigned to one of three groups: gain-increase adaptation (1.5×), gain-decrease adaptation (0.5×), or no adaptation (baseline, 1×). After adaptation training (horizontal rotations at 0.5 Hz with peak velocity 20°/s), we measured the sinusoidal (0.2-10 Hz, 20-100°/s) and transient (1,500-6,000°/s(2)) VOR in complete darkness. α9-Knockout mice had significantly lower baseline gains compared with control mice. This difference increased with stimulus frequency (∼ 5% <1 Hz to ∼ 25% >1 Hz). Moreover, vestibular adaptation (difference in VOR gain of gain-increase and gain-decrease adaptation groups as % of gain increase) was significantly reduced in α9-knockout mice (17%) compared with control mice (53%), a reduction of ∼ 70%. Our results show that the loss of α9 nAChRs moderately affects the VOR but severely affects VOR adaptation, suggesting that the EVS plays a crucial role in vestibular plasticity. PMID:26424577

  16. Effects of GABAergic and noradrenergic injections into the cerebellar flocculus on vestibulo-ocular reflexes in the rabbit.

    PubMed

    van Neerven, J; Pompeiano, O; Collewijn, H

    1991-01-01

    The role of the vesitibulo-cerebellum of the rabbit in the control of the vestibulo-ocular response (VOR) and optokinetic response (OKR) reflexes was investigated by bilateral microinjections, into the flocculus, of substances affecting GABAergic or noradrenergic neurotransmission. GABA, the main transmitter through which cerebellar interneurons inhibit Purkinje cells directly or indirectly, acts normally through GABAA receptors (mainly located in the granular layer) and GABAB receptors (predominantly located in the molecular layer). Despite this different distribution, floccular injections of the GABAA agonist muscimol and of the GABAB agonist baclofen had a similar effect, presumably by profound inhibition of Purkinje cells. This effect consisted of a reduction in the gain of the VOR (in darkness and in light) as well as of the OKR by at least 50%. This provides firm evidence that the net effect of normal Purkinje-cell activity in the flocculus is to enhance the VOR and OKR, rather than to inhibit these responses, as is sometimes supposed. Intrafloccular injections of the beta-noradrenergic agonist isoproterenol or the beta-noradrenergic antagonist sotalol did not affect the basic magnitude of the VOR and OKR. However, these substances markedly affected the adaptive processes, which cause the VOR and OKR to change its magnitude when this is no longer adequate in stabilizing the retinal image. By a suitable combination of vestibular and optokinetic stimuli, consistent upward changes in the gain of these reflexes could be reliably and reproducibly induced in uninjected animals. Floccular injections of sotalol impaired these adaptive changes markedly, whereas injections of isoproterenol enhanced the adaptation, particularly of the VOR measured in darkness. These findings strongly suggest that the effectuation of adaptive changes of vestibular, and possibly other, motor control systems is strongly facilitated by the noradrenergic innervation of the flocculus, which

  17. A reevaluation of the vestibulo-ocular reflex: new ideas of its purpose, properties, neural substrate, and disorders

    NASA Technical Reports Server (NTRS)

    Leigh, R. J.; Brandt, T.

    1993-01-01

    Conventional views of the vestibulo-ocular reflex (VOR) have emphasized testing with caloric stimuli and by passively rotating patients at low frequencies in a chair. The properties of the VOR tested under these conditions differ from the performance of this reflex during the natural function for which it evolved--locomotion. Only the VOR (and not visually mediated eye movements) can cope with the high-frequency angular and linear perturbations of the head that occur during locomotion; this is achieved by generating eye movements at short latency (< 16 msec). Interpretation of vestibular testing is enhanced by the realization that, although the di- and trisynaptic components of the VOR are essential for this short-latency response, the overall accuracy and plasticity of the VOR depend upon a distributed, parallel network of neurons involving the vestibular nuclei. Neurons in this network variously upon a distributed, parallel network of neurons involving the vestibular nuclei. Neurons in this network variously encode inputs from the labyrinthine semicircular canals and otoliths, as well as from the visual and somatosensory systems. The central vestibular pathways branch to contact vestibular cortex (for perception) and the spinal cord (for control of posture). Thus, the vestibular nuclei basically coordinate the stabilization of gaze and posture, and contribute to the perception of verticality and self-motion. Consequently, brainstem disorders that disrupt the VOR cause not just only nystagmus, but also instability of posture (eg, increased fore-aft sway in patients with downbeat nystagmus) and disturbance of spatial orientation (eg, tilt of the subjective visual vertical in Wallenberg's syndrome).

  18. Modification of the Passive Vestibulo-Ocular Reflex During and After Short-Duration Spaceflight

    NASA Technical Reports Server (NTRS)

    Wood, S. J.; Reschke, M. F.

    2011-01-01

    The vestibulo-ocular reflex (VOR) is mediated by integration of canal and otolith inputs to generate compensatory eye movements during head movements. We hypothesized that adaptive change in vestibular processing of gravitoinertial cues would be reflected by plane specific modification of the VOR during passive whole-body rotation during and after spaceflight. Using a repeated measures design, the VOR was assessed in four payload crewmembers in yaw, pitch and roll planes during multiple sessions before, during and after an 8 day orbital mission (STS-42). Rotation was about an earth-vertical axis during ground tests, with the head located off-axis by up to 45cm during pitch and roll rotation (peak acceleration less than 0.2g). The motion profiles included sum-of-sinusoids between 0.02 - 1.39 Hz (yaw), single sinusoids between 0.05-1.25 Hz (yaw and pitch) and velocity steps (yaw, pitch and roll). Eye movements were recorded with both video and electro-oculographic techniques. As expected, VOR gain changes were greater in pitch than in yaw. During pitch rotation, there was a progressive shift in the axis of eye movements during the flight, which was also present during the early post-flight period. This increased horizontal component during pitch, most prevalent at 0.2 Hz, was interpreted as an increase in a translational vergence response elicited during eccentric rotation as subjects imagined a wall fixed target. There was also an increased horizontal component during the eccentric roll step runs performed on flight day 7. These results are consistent with a frequency-dependent increase in otolith-mediated translational VOR responses following adaptation to microgravity. We conclude that the adaptive changes in the VOR are likely to be greatest in the frequency range where there is a cross-over of otolith-mediated tilt and translation responses.

  19. Prolonged vestibular stimulation induces homeostatic plasticity of the vestibulo-ocular reflex in larval Xenopus laevis.

    PubMed

    Dietrich, Haike; Straka, Hans

    2016-07-01

    Vestibulo-ocular reflexes (VOR) stabilise retinal images during head/body motion in vertebrates by generating spatio-temporally precise extraocular motor commands for corrective eye movements. While VOR performance is generally robust with a relatively stable gain, cerebellar circuits are capable of adapting the underlying sensory-motor transformation. Here, we studied cerebellum-dependent VOR plasticity by recording head motion-induced lateral rectus and superior oblique extraocular motor discharge in semi-intact preparations of Xenopus laevis tadpoles. In the absence of visual feedback, prolonged sinusoidal rotation caused either an increase or decrease of the VOR gain depending on the motion stimulus amplitude. The observed changes in extraocular motor discharge gradually saturated after 20 min of constant rotation and returned to baseline in the absence of motion stimulation. Furthermore, plastic changes in lateral rectus and superior oblique motor commands were plane-specific for horizontal and vertical rotations, respectively, suggesting that alterations are restricted to principal VOR connections. Comparison of multi- and single-unit activity indicated that plasticity occurs in all recorded units of a given extraocular motor nucleus. Ablation of the cerebellum abolished motoneuronal gain changes and prevented the induction of plasticity, thus demonstrating that both acquisition and retention of this type of plasticity require an intact cerebellar circuitry. In conclusion, the plane-specific and stimulus intensity-dependent modification of the VOR gain through the feed-forward cerebellar circuitry represents a homeostatic plasticity that likely maintains an optimal working range for the underlying sensory-motor transformation. PMID:27152983

  20. Enhanced vestibulo-ocular reflex to electrical vestibular stimulation in Meniere's disease.

    PubMed

    Aw, Swee T; Aw, Grace E; Todd, Michael J; Halmagyi, G Michael

    2013-02-01

    Meniere's disease is characterized by sporadic episodes of vertigo, nystagmus, fluctuating sensorineural hearing loss, tinnitus and aural pressure. Since Meniere's disease can affect different regions of the vestibular labyrinth, we investigated if electrical vestibular stimulation (EVS) which excites the entire vestibular labyrinth may be useful to reveal patchy endorgan pathology. We recorded three-dimensional electrically evoked vestibulo-ocular reflex (eVOR) to transient EVS using bilateral, bipolar 100-ms current steps at intensities of 0.9, 2.5, 5.0, 7.5 and 10.0 mA with dual-search coils in 12 unilateral Meniere's patients. Their results were compared to 17 normal subjects. Normal eVOR had tonic and phasic spatiotemporal properties best described by the torsional component, which was four times larger than horizontal and vertical components. At EVS onset and offset of 8.9 ms latency, there were phasic eVOR initiation (M = 1,267 °/s(2)) and cessation (M = -1,675 °/s(2)) acceleration pulses, whereas during the constant portion of the EVS, there was a maintained tonic eVOR (M = 9.1 °/s) at 10 mA. However in Meniere's disease, whilst latency of EVS onset and offset was normal at 9.0 ms, phasic eVOR initiation (M = 1,720 °/s(2)) and cessation (M = -2,523 °/s(2)) were enlarged at 10 mA. The initiation profile was a bimodal response, whilst the cessation profile frequently did not return to baseline. The tonic eVOR (M = 20.5 °/s) exhibited a ramped enhancement of about twice normal at 10 mA. Tonic eVOR enhancement was present for EVS >0.9 mA and disproportionately enhanced the torsional, vertical and horizontal components. These eVOR abnormalities may be a diagnostic indicator of Meniere's disease and may explain the vertigo attacks in the presence of declining mechanically evoked vestibular responses.

  1. Directional plasticity rapidly improves 3D vestibulo-ocular reflex alignment in monkeys using a multichannel vestibular prosthesis.

    PubMed

    Dai, Chenkai; Fridman, Gene Y; Chiang, Bryce; Rahman, Mehdi A; Ahn, Joong Ho; Davidovics, Natan S; Della Santina, Charles C

    2013-12-01

    Bilateral loss of vestibular sensation can be disabling. We have shown that a multichannel vestibular prosthesis (MVP) can partly restore vestibular sensation as evidenced by improvements in the 3-dimensional angular vestibulo-ocular reflex (3D VOR). However, a key challenge is to minimize misalignment between the axes of eye and head rotation, which is apparently caused by current spread beyond each electrode's targeted nerve branch. We recently reported that rodents wearing a MVP markedly improve 3D VOR alignment during the first week after MVP activation, probably through the same central nervous system adaptive mechanisms that mediate cross-axis adaptation over time in normal individuals wearing prisms that cause visual scene movement about an axis different than the axis of head rotation. We hypothesized that rhesus monkeys would exhibit similar improvements with continuous prosthetic stimulation over time. We created bilateral vestibular deficiency in four rhesus monkeys via intratympanic injection of gentamicin. A MVP was mounted to the cranium, and eye movements in response to whole-body passive rotation in darkness were measured repeatedly over 1 week of continuous head motion-modulated prosthetic electrical stimulation. 3D VOR responses to whole-body rotations about each semicircular canal axis were measured on days 1, 3, and 7 of chronic stimulation. Horizontal VOR gain during 1 Hz, 50 °/s peak whole-body rotations before the prosthesis was turned on was <0.1, which is profoundly below normal (0.94 ± 0.12). On stimulation day 1, VOR gain was 0.4-0.8, but the axis of observed eye movements aligned poorly with head rotation (misalignment range ∼30-40 °). Substantial improvement of axis misalignment was observed after 7 days of continuous motion-modulated prosthetic stimulation under normal diurnal lighting. Similar improvements were noted for all animals, all three axes of rotation tested, for all sinusoidal frequencies tested (0.05-5 Hz), and for

  2. Chronic stimulation of the semicircular canals using a multichannel vestibular prosthesis: effects on locomotion and angular vestibulo-ocular reflex in chinchillas.

    PubMed

    Sun, Daniel Q; Rahman, Mehdi A; Fridman, Gene; Dai, Chenkai; Chiang, Bryce; Della Santina, Charles C

    2011-01-01

    Bilateral loss of vestibular sensation causes difficulty maintaining stable vision, posture and gait. An implantable prosthesis that partly restores vestibular sensation could significantly improve quality of life for individuals disabled by this disorder. We have developed a head-mounted multichannel vestibular prosthesis (MVP) that restores sufficient semicircular canal function to recreate a 3D angular vestibulo-ocular reflex (aVOR). In this study, we evaluated effects of chronic MVP stimulation on locomotion in chinchillas. Two of three animals examined exhibited significant improvements in both locomotion and aVOR.

  3. Vestibulo-ocular, optokinetic and postural function in humans with rheumatoid arthritis.

    PubMed

    King, Jaimee; Young, Calvin; Highton, John; Smith, Paul F; Darlington, Cynthia L

    2002-08-01

    The present study investigated vestibulo-ocular reflex (VOR), optokinetic reflex (OKR) and postural function in patients with rheumatoid arthritis (RA). Compared with controls, no differences in gaze-holding, VOR gain or phase, OKR slow phase velocity (SPV) or quick phase amplitude, optokinetic afternystagmus SPV or duration, or latency to the illusion of circularvection, were found. RA patients did exhibit greater sway in the leftward direction (P<0.01), however, this was no greater in the conditions of the Clinical Test of Sensory Interaction and Balance that increase reliance upon vestibular information. We conclude that RA patients do not exhibit substantial deficits in visual-vestibular function.

  4. Kernschmelze Der nachhaltige Einfluss von Nuklearwaffen auf Politik und Wirtschaft

    NASA Astrophysics Data System (ADS)

    Greiner, Bernd

    "Was sollen wir von einer Kultur halten, der die Ethik stets als wesentliches Element des menschlichen Lebens galt, die aber - außer in fachlicher oder spieltheoretischer Terminologie - nicht in der Lage war, über die Möglichkeit zu sprechen, nahezu alle Menschen zu töten?" Der Fragesteller gehört zu den berühmtesten Physikern des 20. Jahrhunderts und zu den nach wie vor Umstrittensten. über ihn wurde in den 1960er Jahren ein international viel beachtetes Theaterstück geschrieben, vor wenigen Jahren gar eine Oper.

  5. Herausforderungen durch die deutsche Wiedervereinigung

    NASA Astrophysics Data System (ADS)

    Stäglin, Reiner

    Die Wiedervereinigung stellte auch die Statistik vor große Aufgaben. Die als Organ der staatlichen Planung staatsnah orientierte Statistik der DDR musste auf das zur Neutralität und wissenschaftlichen Unabhängigkeit verpflichtete System der Bundesrepublik umgestellt werden. Ebenso verlangten die Universitäten eine Neuorientierung. Die Deutsche Statistische Gesellschaft hat sich vor allem dreier Aufgaben mit großem Engagement, aber auch mit Bedachtsamkeit angenommen: Aufnahme und Integration der Statistiker aus den neuen Bundesländern in die Gesellschaft, Begleitung der Neuausrichtung des Faches Statistik an deren Hochschulen und Sicherung sowie Nutzung von Datenbeständen der ehemaligen DDR.

  6. Tantal

    NASA Astrophysics Data System (ADS)

    Dettner, H. W.; Franssen, H.; Giesen, K.; Hayes, E. T.; Holetzko, H.; Keysselitz, B.; Loebich, O.; Pelzel, E.; Reinsch, W.; Rostoker, W.; Saur, G.; Volk, K. E.; Wallbaum, H. J.; Borchers, Heinz; Schmidt, Ernst

    Tantal gehört zu den seltenen Metallen. In der Erdrinde kommt es in geringeren Mengen vor als Platin oder Uran. Die Welterzeugung an Tantal betrug 1957 etwa 400 t [K 2]. Tantal kommt in der Natur — wie das Schwestermetall Niob, mit dem es immer vergesellschaftet ist und von dem es nur sehr schwierig getrennt werden kann — fast ausschließlich in Form von Oxyden vor. Die wertvollsten Erze sind Tantalit (Eisen-Mangan-Tantalat mit 42...84% Ta2O5), Niob-Tantalit und Tantal-Niobit (25...40% Ta2O5).

  7. Einparksysteme

    NASA Astrophysics Data System (ADS)

    Knoll, Peter

    Bei nahezu allen Fahrzeugen ist die Sicht beim Rangieren stark eingeschränkt. Dies liegt vor allem an den modernen Fahrzeugkarosserien, mit denen möglichst niedrige Luftwiderstandsbeiwerte erreicht werden, um den Kraftstoffverbrauch zu reduzieren. In der Regel entsteht dadurch eine leichte Keilform. Vorhandene Hindernisse sind somit häufig nur schlecht oder überhaupt nicht erkennbar. So sieht der Durchschnittsfahrer beim Blick durch die Heckscheibe die Straßenoberfläche erst in einem Abstand von 8…10 m. Auch direkt vor dem Fahrzeug befindliche Hindernisse entziehen sich dem Blick des Fahrers, da sie durch den Fahrzeugvorbau verdeckt werden.

  8. Visual contribution to the high-frequency human angular vestibulo-ocular reflex.

    PubMed

    Chim, Daniel; Lasker, David M; Migliaccio, Americo A

    2013-09-01

    The vestibulo-ocular reflex (VOR) acts to maintain images stable on the retina by rotating the eyes in exactly the opposite direction, but with equal magnitude, to head velocity. When viewing a near target, this reflex has an increased response to compensate for the translation of the eyes relative to the target that acts to reduce retinal image slip. Previous studies have shown that retinal velocity error provides an important visual feedback signal to increase the low-frequency (<1 Hz) VOR response during near viewing. We sought to determine whether initial eye position and retinal image position error could provide enough information to substantially increase the high-frequency VOR gain (eye velocity/head velocity) during near viewing. Ten human subjects were tested using the scleral search coil technique during horizontal head impulses under different lighting conditions (constant dark, strobe light at 0.5, 1, 2, 4, 10, 15 Hz, constant light) while viewing near (9.5 ± 1.3 cm) and far (104 cm) targets. Our results showed that the VOR gain increased during near viewing compared to far viewing, even during constant dark. For the near target, there was an increase in VOR gain with increasing strobe frequency from 1.17 ± 0.17 in constant dark to 1.36 ± 0.27 in constant light, a 21 ± 9 % increase. For the far target, strobe frequency had no effect. Presentation order of strobe frequency (i.e. 0.5-15 vs. 15-0.5 Hz) did not affect the gain, but it did affect the vergence angle (angle between the two eye's lines of sight). The VOR gain and vergence angles were constant during each trial. Our findings show that a retinal position error signal helps increase the vergence angle and could be invoking vestibular adaptation mechanisms to increase the high-frequency VOR response during near viewing. This is in contrast to the low-frequency VOR that depends more on retinal velocity error and predictive adaptation mechanisms.

  9. Renaturierung von Fließgewässern

    NASA Astrophysics Data System (ADS)

    Lüderitz, Volker; Jüpner, Robert

    Beim Umgang mit den Gewässern wurde der wasserbaulichen Durchsetzung bestimmter Nutzungsansprüche, vor allem der Landwirtschaft, dem Hochwasserschutz, der Wassergewinnung, der Schifffahrt und der Energiegewinnung über Jahrhunderte absoluter Vorrang vor den Belangen des ökologischen Zustandes der Gewässer selbst und damit auch ihrer multifunktionalen Nutzbarkeit eingeräumt. Die daraus resultierenden Umweltauswirkungen wurden oft billigend in Kauf genommen. Gezielte Verbesserungen der ökologischen Situation von Gewässern bzw. Gewässerabschnitten, wie z.B. der Einsatz ingenieurbiologischer Bauweisen oder der Einbau von Fischwanderhilfen an Mühlenstauen, blieben auf Ausnahmen beschränkt.

  10. A brief review of the clinical anatomy of the vestibular-ocular connections—how much do we know?

    PubMed Central

    Bronstein, A M; Patel, M; Arshad, Q

    2015-01-01

    The basic connectivity from the vestibular labyrinth to the eye muscles (vestibular ocular reflex, VOR) has been elucidated in the past decade, and we summarise this in graphic format. We also review the concept of ‘velocity storage', a brainstem integrator that prolongs vestibular responses. Finally, we present new discoveries of how complex visual stimuli, such as binocular rivalry, influence VOR processing. In contrast to the basic brainstem circuits, cortical vestibular circuits are far from being understood, but parietal-vestibular nuclei projections are likely to be involved. PMID:25412719

  11. 76 FR 28171 - Standard Instrument Approach Procedures, and Takeoff Minimums and Obstacle Departure Procedures...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-05-16

    ... Policies and Procedures (44 FR 11034; February 26, 1979); and (3) does not warrant preparation of a..., Cheboygan County, RNAV (GPS) RWY 10, Amdt 2 Spearfish, SD, Black Hills-Clyde Ice Field, Takeoff Minimum and... 12, Amdt 15 Bozeman, MT, Gallatin Field, VOR/DME RWY 12, Amdt 4 Devil's Lake, ND, Devil's Lake...

  12. 76 FR 30753 - Agency Information Collection Activities: Requests for Comments; Clearance of Renewed Approval of...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-05-26

    ... collection requirement was published on August 12, 2008 (73 FR 46797). The collection of information is... CFR 91.161 in order to fly within 50 nautical miles (NM) of the Washington, DC omni-directional range... receive training and be tested for flying in the airspace that is within 60 NM of the DCA VOR/DME....

  13. Effect of the slow transient phenomenon of a synaptic modification on vestibulo-ocular reflex adaptation

    NASA Astrophysics Data System (ADS)

    Tsusaka, K.

    1998-05-01

    According to the experimental studies, the duration of the transient phenomenon of the synaptic modification involved in vestibulo-ocular reflex (VOR) adaptation lasts considerably long after the synaptic inputs. In the present article, effect of the transient phenomenon on VOR adaptation is studied by incorporating the transient phenomenon into the cerebellar model proposed by Fujita. In the present extended model, it is assumed that the synaptic modification is a modification of the concentrations of reactants and products for a certain reaction. The synaptic efficacy is given by the concentration of products. The model of reaction includes the supply of reactants and flux of reactants and products out of the reaction system. The supply of reactants is induced by correlation between two different types of input signals, which has been considered to be proportional to the amount of the synaptic modification at the moment. The flux produces natural recovery of the synaptic modification, which was observed in experiments. The simulation results suggest that VOR adaptation takes two types of courses according to the efficiency of the reactant supply to the synaptic inputs under the slow transient phenomenon of the synaptic modification. The present extended model gives approaches to control mechanisms of VOR adaptation.

  14. The horizontal angular vestibulo-ocular reflex: a non-linear mechanism for context-dependent responses.

    PubMed

    Ranjbaran, Mina; Galiana, Henrietta L

    2012-01-01

    A bilateral model for the horizontal angular vestibulo-ocular reflex (AVOR) is presented in this paper. It is shown that by assigning proper non-linear neural computations at the premotor level, the model is capable of replicating target-distance dependent VOR responses. Moreover, the model behavior in case of sensory plugging is also consistent with reported experimental observations.

  15. Artificial balance: restoration of the vestibulo-ocular reflex in humans with a prototype vestibular neuroprosthesis.

    PubMed

    Perez Fornos, Angelica; Guinand, Nils; van de Berg, Raymond; Stokroos, Robert; Micera, Silvestro; Kingma, Herman; Pelizzone, Marco; Guyot, Jean-Philippe

    2014-01-01

    The vestibular system plays a crucial role in the multisensory control of balance. When vestibular function is lost, essential tasks such as postural control, gaze stabilization, and spatial orientation are limited and the quality of life of patients is significantly impaired. Currently, there is no effective treatment for bilateral vestibular deficits. Research efforts both in animals and humans during the last decade set a solid background to the concept of using electrical stimulation to restore vestibular function. Still, the potential clinical benefit of a vestibular neuroprosthesis has to be demonstrated to pave the way for a translation into clinical trials. An important parameter for the assessment of vestibular function is the vestibulo-ocular reflex (VOR), the primary mechanism responsible for maintaining the perception of a stable visual environment while moving. Here we show that the VOR can be artificially restored in humans using motion-controlled, amplitude modulated electrical stimulation of the ampullary branches of the vestibular nerve. Three patients received a vestibular neuroprosthesis prototype, consisting of a modified cochlear implant providing vestibular electrodes. Significantly higher VOR responses were observed when the prototype was turned ON. Furthermore, VOR responses increased significantly as the intensity of the stimulation increased, reaching on average 79% of those measured in healthy volunteers in the same experimental conditions. These results constitute a fundamental milestone and allow us to envision for the first time clinically useful rehabilitation of patients with bilateral vestibular loss.

  16. Automatic Classification of the Vestibulo-Ocular Reflex Nystagmus: Integration of Data Clustering and System Identification.

    PubMed

    Ranjbaran, Mina; Smith, Heather L H; Galiana, Henrietta L

    2016-04-01

    The vestibulo-ocular reflex (VOR) plays an important role in our daily activities by enabling us to fixate on objects during head movements. Modeling and identification of the VOR improves our insight into the system behavior and improves diagnosis of various disorders. However, the switching nature of eye movements (nystagmus), including the VOR, makes dynamic analysis challenging. The first step in such analysis is to segment data into its subsystem responses (here slow and fast segment intervals). Misclassification of segments results in biased analysis of the system of interest. Here, we develop a novel three-step algorithm to classify the VOR data into slow and fast intervals automatically. The proposed algorithm is initialized using a K-means clustering method. The initial classification is then refined using system identification approaches and prediction error statistics. The performance of the algorithm is evaluated on simulated and experimental data. It is shown that the new algorithm performance is much improved over the previous methods, in terms of higher specificity.

  17. Vestibulo-ocular reflex suppression during head-fixed saccades reveals gaze feedback control.

    PubMed

    Daye, Pierre M; Roberts, Dale C; Zee, David S; Optican, Lance M

    2015-01-21

    Previous experiments have shown that the vestibulo-ocular reflex (VOR) is partially suppressed during large head-free gaze (gaze = eye-in-head + head-in-space) shifts when both the eyes and head are moving actively, on a fixed body, or when the eyes are moving actively and the head passively on a fixed body. We tested, in human subjects, the hypothesis that the VOR is also suppressed during gaze saccades made with en bloc, head and body together, rotations. Subjects made saccades by following a target light. During some trials, the chair rotated so as to move the entire body passively before, during, or after a saccade. The modulation of the VOR was a function of both saccade amplitude and the time of the head perturbation relative to saccade onset. Despite the perturbation, gaze remained accurate. Thus, VOR modulation is similar when gaze changes are programmed for the eyes alone or for the eyes and head moving together. We propose that the brain always programs a change in gaze using feedback based on gaze and head signals, rather than on separate eye and head trajectories.

  18. Neural correlates of motor learning in the vestibulo-ocular reflex: dynamic regulation of multimodal integration in the macaque vestibular system.

    PubMed

    Sadeghi, Soroush G; Minor, Lloyd B; Cullen, Kathleen E

    2010-07-28

    Motor learning is required for the reacquisition of skills that have been compromised as a result of brain lesion or disease, as well as for the acquisition of new skills. Behaviors with well characterized anatomy and physiology are required to yield significant insight into changes that occur in the brain during motor learning. The vestibulo-ocular reflex (VOR) is well suited to establish connections between neurons, neural circuits, and motor performance during learning. Here, we examined the linkage between neuronal and behavioral VOR responses in alert behaving monkeys (Macaca mulatta) during the impressive recovery that occurs after unilateral vestibular loss. We show, for the first time, that motor learning is characterized by the dynamic reweighting of inputs from different modalities (i.e., vestibular vs extravestibular) at the level of the single neurons that constitute the first central stage of vestibular processing. Specifically, two types of information, which did not influence neuronal responses before the lesion, had an important role during compensation. First, unmasked neck proprioceptive inputs played a critical role in the early stages of this process demonstrated by faster and more substantial recovery of vestibular responses in proprioceptive sensitive neurons. Second, neuronal and VOR responses were significantly enhanced during active relative to passive head motion later in the compensation process (>3 weeks). Together, our findings provide evidence linking the dynamic regulation of multimodal integration at the level of single neurons and behavioral recovery, suggesting a role for homeostatic mechanisms in VOR motor learning.

  19. Studies of the vestibulo-ocular reflex on STS 4, 5 and 6

    NASA Technical Reports Server (NTRS)

    Thornton, William E.; Pool, Sam L.; Moore, Thomas P.; Uri, John J.

    1988-01-01

    The vestibulo-ocular reflex (VOR) may be altered by weightlessness. Since this reflex plays a large role in visual stabilization, it was important to document any changes caused by space flight. This is a report on findings on STS-4 through 6 and is part of a larger study of neurosensory adaptation done on STS-4 through 8. Voluntary horizontal head oscillations at 1/3 Hz with amplitude of 30 deg right and left of center were recorded by a potentiometer and compared to eye position recorded by electroculography under the following conditions: eyes open, head fixed, tracking horizontal targets switched 0, 15, and 30 degrees right and left (optokinetic reflex - OKR - and calibration); eyes open and fixed on static external target with oscillation, (vestibulo ocular reflex, eyes closed - VOR EC); eyes open and wearing opaque goggles with target fixed in imagination (vestibulo-ocular reflex, eyes shaded - VOR ES); and eyes open and fixed on a head synchronized target with head oscillation (VOR suppression). No significant changes were found in voluntary head oscillation frequency or amplitude in those with (n=5), and without (n=3), space motion sickness (SMS), with phase of flight or test condition. Variations in head oscillation were too small to have produced detectable changes in test results.

  20. Amplitude and frequency prediction in the translational vestibulo-ocular reflex.

    PubMed

    Schneider, Rosalyn; Walker, Mark F

    2014-01-01

    The goal of this study was to assess the effect of amplitude and frequency predictability on the performance of the translational vestibulo-ocular reflex (tVOR). Eye movements were recorded in 5 subjects during continuous vertical translation that consisted of a series of segments with: 1) 3 amplitudes at constant frequency (2 Hz) or 2) 3 different frequencies (1.6, 2, 2.5 Hz). Stimulus changes were presented in a pseudo-random order. We found that there was little change in the tVOR immediately after an unexpected stimulus change, as if eye velocity were being driven more by an expectation based on previous steady-state motion than by current head translation. For amplitude transitions, only about 30% of the eventual response change was seen in the first half cycle. Similarly, a sudden change in translation frequency did not appear in eye velocity for 70 ms, compared to a 8 ms lag during similar yaw rotation. Finally, after a sudden large decrease in frequency, the eyes continued to track at the original higher frequency, resulting initially in an anti-compensatory tVOR acceleration. Our results elucidate further the complexity of the tVOR and show that motion prediction based on prior experience plays an important role in its response.

  1. 76 FR 65106 - Amendment of Federal Airways; Alaska

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-10-20

    ... No. FAA-2011-0010, Airspace Docket No. 11- AAL-1 published on April 28, 2011 (76 FR 23687), amends... subsequently delayed the effective date from June 30, 2011, until further notice (76 FR 35097; June 16, 2011... of effective date published in the Federal Register on June 16, 2011 (76 FR 35097). VOR...

  2. 77 FR 67782 - Proposed Amendment of Class E Airspace; Casper, WY

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-11-14

    ... ``significant rule'' under DOT Regulatory Policies and Procedures (44 FR 11034; February 26, 1979); and (3) does....S.C. 106(g), 40103, 40113, 40120; E.O. 10854, 24 FR 9565, 3 CFR, 1959-1963 Comp., p. 389. Sec. 71.1...) traffic from en route airspace to the airport. Decommissioning of the Muddy Mountain VOR...

  3. 77 FR 23171 - Proposed Amendment of Class E Airspace; Fairfield, CA

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-04-18

    ... 12866; (2) is not a ``significant rule'' under DOT Regulatory Policies and Procedures (44 FR 11034..., 40113, 40120; E.O. 10854, 24 FR 9565, 3 CFR, 1959-1963 Comp., p. 389. Sec. 71.1 2. The incorporation by... proposed decommissioning of the Travis VHF Omni-Directional Radio Range (VOR) has made this...

  4. 76 FR 53361 - Proposed Revocation and Amendment of Class E Airspace; Olathe, KS

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-08-26

    ... Regulatory Policies and Procedures (44 FR 11034; February 26, 1979); and (3) does not warrant preparation of... read as follows: Authority: 49 U.S.C. 106(g); 40103, 40113, 40120; E.O. 10854, 24 FR 9565, 3 CFR, 1959... Range/ Distance Measuring Equipment (VOR/DME) at Johnson County Executive Airport, Olathe, KS, has...

  5. 77 FR 23172 - Proposed Amendment of Class E Airspace; Woodland, CA

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-04-18

    ... Executive Order 12866; (2) is not a ``significant rule'' under DOT Regulatory Policies and Procedures (44 FR...: Authority: 49 U.S.C. 106(g), 40103, 40113, 40120; E.O. 10854, 24 FR 9565, 3 CFR, 1959-1963 Comp., p. 389... decommissioning of the Travis VHF Omni-Directional Radio Range (VOR) has made this action necessary for the...

  6. Tipps und Tricks

    NASA Astrophysics Data System (ADS)

    Häger, Wolfgang; Bauermeister, Dirk

    Hier wollen wir einige uns nützlich erscheinende Hinweise zur Arbeit mit dem Inventor geben. Dabei geht es vor allem darum, das Arbeiten mit dem Inventor zu vereinfachen. Die Beispiele stellen eine unvollständige Aufzählung dar und sollen dazu anregen, nach alternativen Vorgehensweisen zu suchen (hier sei noch einmal ausdrücklich auf das Internet verwiesen).

  7. 75 FR 20321 - Proposed Amendment of Class E Airspace; Bozeman, MT

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-04-19

    ... Executive Order 12866; (2) is not a ``significant rule'' under DOT Regulatory Policies and Procedures (44 FR... follows: Authority: 49 U.S.C. 106(g), 40103, 40113, 40120; E.O. 10854, 24 FR 9565, 3 CFR, 1959-1963 Comp... aircraft using a new VHF Omni-Directional Radio Range (VOR) Standard Instrument Approach Procedure...

  8. Automatic Classification of the Vestibulo-Ocular Reflex Nystagmus: Integration of Data Clustering and System Identification.

    PubMed

    Ranjbaran, Mina; Smith, Heather L H; Galiana, Henrietta L

    2016-04-01

    The vestibulo-ocular reflex (VOR) plays an important role in our daily activities by enabling us to fixate on objects during head movements. Modeling and identification of the VOR improves our insight into the system behavior and improves diagnosis of various disorders. However, the switching nature of eye movements (nystagmus), including the VOR, makes dynamic analysis challenging. The first step in such analysis is to segment data into its subsystem responses (here slow and fast segment intervals). Misclassification of segments results in biased analysis of the system of interest. Here, we develop a novel three-step algorithm to classify the VOR data into slow and fast intervals automatically. The proposed algorithm is initialized using a K-means clustering method. The initial classification is then refined using system identification approaches and prediction error statistics. The performance of the algorithm is evaluated on simulated and experimental data. It is shown that the new algorithm performance is much improved over the previous methods, in terms of higher specificity. PMID:26357393

  9. Gravity-dependent nystagmus and inner-ear dysfunction suggest anterior and posterior inferior cerebellar artery infarct.

    PubMed

    Shaikh, Aasef G; Miller, Benjamin R; Sundararajan, Sophia; Katirji, Bashar

    2014-04-01

    Cerebellar lesions may present with gravity-dependent nystagmus, where the direction and velocity of the drifts change with alterations in head position. Two patients had acute onset of hearing loss, vertigo, oscillopsia, nausea, and vomiting. Examination revealed gravity-dependent nystagmus, unilateral hypoactive vestibulo-ocular reflex (VOR), and hearing loss ipsilateral to the VOR hypofunction. Traditionally, the hypoactive VOR and hearing loss suggest inner-ear dysfunction. Vertigo, nausea, vomiting, and nystagmus may suggest peripheral or central vestibulopathy. The gravity-dependent modulation of nystagmus, however, localizes to the posterior cerebellar vermis. Magnetic resonance imaging in our patients revealed acute cerebellar infarct affecting posterior cerebellar vermis, in the vascular distribution of the posterior inferior cerebellar artery (PICA). This lesion explains the gravity-dependent nystagmus, nausea, and vomiting. Acute onset of unilateral hearing loss and VOR hypofunction could be the manifestation of inner-ear ischemic injury secondary to the anterior inferior cerebellar artery (AICA) compromise. In cases of combined AICA and PICA infarction, the symptoms of peripheral vestibulopathy might masquerade the central vestibular syndrome and harbor a cerebellar stroke. However, the gravity-dependent nystagmus allows prompt identification of acute cerebellar infarct.

  10. 14 CFR 171.7 - Performance requirements.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 14 Aeronautics and Space 3 2010-01-01 2010-01-01 false Performance requirements. 171.7 Section 171...) NAVIGATIONAL FACILITIES NON-FEDERAL NAVIGATION FACILITIES VOR Facilities § 171.7 Performance requirements. (a...-service test evaluation period, for calibration and stability The tests are made with a...

  11. Reduction of ocular counter-rolling by adaptation to space

    NASA Technical Reports Server (NTRS)

    Dai, Mingjia; Mcgarvie, Leigh; Kozlovskaya, Inessa; Sirota, Mischa; Raphan, Theodore; Cohen, Bernard

    1993-01-01

    We studied the three-dimensional vestibulo-ocular reflex (VOR) of rhesus monkeys before and after the COSMOS Biosatellite 2229 Mission of 1992-1993. This included tests of ocular counter-rolling (OCR), the gain of the vestibulo-ocular reflex (VOR), and spatial orientation of velocity storage. A four-axis vestibular and oculomotor stimulator was transported to the Institute of Biomedical Problems in Moscow for the pre- and postflight ground-based testing. Twelve normal juvenile male rhesus monkey were implanted surgically with eye coils and tested 60-90 days before spaceflight. Two monkey (7906 and 6151), selected from the twelve as flight animals, flew from 12/29/92 to 1/10/93. Upon recovery, they were tested for 11 days postflight along with three control animals. Compensatory ocular torsion was produced in two ways: (1) Lateral head tilts evoked OCR through otolith-ocular reflexes. OCR was also measured dynamically during off-vertical axis rotation (OVAR). (2) Rotation about a naso-occipital axis that was either vertical of horizontal elicited torsional nystagmus through semicircular canal-ocular reflexes (roll VOR). OCR from the otoliths was substantially reduced (70 percent) for 11 days after reentry on both modes of testing. The gain of the roll VOR was also decreased, but less than OCR. These data demonstrate that there was a long-lasting depression of torsional or roll eye movements after adaptation to microgravity in these monkeys, especially those movements produced by the otolith organs.

  12. 14 CFR 93.350 - Definitions.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... AND GENERAL OPERATING RULES SPECIAL AIR TRAFFIC RULES New York Class B Airspace Hudson River and East... Exclusion, as defined in paragraph (d) of this section, from one end to the other. (c) New York Class B... the LGA VOR/DME 6-mile arc to the north tip of Roosevelt Island. (d) New York Class B airspace...

  13. 14 CFR 93.350 - Definitions.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... AND GENERAL OPERATING RULES SPECIAL AIR TRAFFIC RULES New York Class B Airspace Hudson River and East... Exclusion, as defined in paragraph (d) of this section, from one end to the other. (c) New York Class B... the LGA VOR/DME 6-mile arc to the north tip of Roosevelt Island. (d) New York Class B airspace...

  14. 14 CFR 93.350 - Definitions.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... AND GENERAL OPERATING RULES SPECIAL AIR TRAFFIC RULES New York Class B Airspace Hudson River and East... Exclusion, as defined in paragraph (d) of this section, from one end to the other. (c) New York Class B... the LGA VOR/DME 6-mile arc to the north tip of Roosevelt Island. (d) New York Class B airspace...

  15. Astrophysik Spuren einer Sternenexplosion

    NASA Astrophysics Data System (ADS)

    Knie, Klaus

    2005-01-01

    Münchner Physikern ist es gelungen, mit einem Tandembeschleuniger radioaktive 60Fe-Atome in einer Tiefseeprobe nachzuweisen. Wahrscheinlich wurde dieser radioaktive Stoff vor drei Millionen Jahren von einer etwa hundert Lichtjahre entfernten Supernova erzeugt, durch das Weltall geschleudert und schließlich auf der Erde abgelagert.

  16. 75 FR 32096 - Standard Instrument Approach Procedures, and Takeoff Minimums and Obstacle Departure Procedures...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-06-07

    ... Regulatory Policies and Procedures (44 FR 11034; February 26, 1979); and (3) does not warrant preparation of... 1A, CANCELLED Barrow, AK, Wiley Post-Will Rogers Memorial, VOR/DME RWY 25, Orig Muscle Shoals, AL, Northwest Alabama Rgnl, ILS OR LOC RWY 29, Amdt 5 Muscle Shoals, AL, Northwest Alabama Rgnl, RNAV (GPS)...

  17. 75 FR 19541 - Standard Instrument Approach Procedures, and Takeoff Minimums and Obstacle Departure Procedures...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-04-15

    ... Policies and Procedures (44 FR 11034; February 26, 1979); and (3) does not warrant preparation of a..., Amdt 10 Leonardtown, MD, St. Mary's County Rgnl, VOR OR GPS RWY 29, Amdt 6A, CANCELLED Flint, MI... (GPS) RWY 34, Amdt 1 Minneapolis, MN, Anoka County-Blaine Arpt (Janes Field), Takeoff Minimums...

  18. 78 FR 59805 - Establishment of Class E Airspace; Cody, WY

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-09-30

    ..., Cody, WY, to facilitate vectoring of Instrument Flight Rules (IFR) aircraft under control of Salt Lake...) to establish controlled airspace at Cody, WY (78 FR 40078). Interested parties were invited to... VOR/DME navigation aid, Cody, WY, to accommodate IFR aircraft under control of Salt Lake City ARTCC...

  19. 78 FR 29613 - Modification and Revocation of Air Traffic Service Routes; Jackson, MS

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-05-21

    ... airways; and cancel two VOR Federal airways in the vicinity of Jackson, MS (78 FR 10560, February 14, 2013... Transportation (DOT) Regulatory Policies and Procedures (44 FR 11034; February 26, 1979); and (3) does not..., 40113, 40120; E.O. 10854, 24 FR 9565, 3 CFR, 1959-1963 Comp., p. 389. Sec. 71.1 0 2. The...

  20. 77 FR 35836 - Amendment of Air Traffic Service Routes; Southwestern United States

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-06-15

    ... routes in the southwestern United States (78 FR 24156). An NPRM correction published in the Federal Register of May 23, 2012 (77 FR 30437) corrected the description of VOR Federal airway V-16. Interested... and Procedures (44 FR 11034; February 26, 1979); and (3) does not warrant preparation of a...

  1. Reversal of Motor Learning in the Vestibulo-Ocular Reflex in the Absence of Visual Input

    ERIC Educational Resources Information Center

    Cohen, Marlene R.; Meissner, Geoffrey W.; Schafer, Robert J.; Raymond, Jennifer L.

    2004-01-01

    Motor learning in the vestibulo-ocular reflex (VOR) and eyeblink conditioning use similar neural circuitry, and they may use similar cellular plasticity mechanisms. Classically conditioned eyeblink responses undergo extinction after prolonged exposure to the conditioned stimulus in the absence of the unconditioned stimulus. We investigated the…

  2. Learning in a Simple Motor System

    ERIC Educational Resources Information Center

    Broussard, Dianne M.; Kassardjian, Charles D.

    2004-01-01

    Motor learning is a very basic, essential form of learning that appears to share common mechanisms across different motor systems. We evaluate and compare a few conceptual models for learning in a relatively simple neural system, the vestibulo-ocular reflex (VOR) of vertebrates. We also compare the different animal models that have been used to…

  3. 78 FR 78794 - Proposed Establishment of Class E Airspace; Flagstaff, AZ

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-12-27

    ... route domestic airspace extending upward from 1,200 feet above the surface at the Flagstaff VOR/DME... ``significant rule'' under DOT Regulatory Policies and Procedures (44 FR 11034; February 26, 1979); and (3) does..., 40113, 40120; E.O. 10854, 24 FR 9565, 3 CFR, 1959-1963 Comp., p. 389. Sec. 71.1 0 2. The...

  4. 76 FR 77939 - Proposed Provision of Navigation Services for the Next Generation Air Transportation System...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-12-15

    ... over the conterminous US (CONUS) and terminal operations at the Core 30 airports.\\2\\ The FAA is also... (VORTAC), VOR/DME, Non-Directional Beacon (NDB) operated by the FAA. \\2\\ Core 30 airports are those with... http://aspmhelp.faa.gov/index.php/Core_30 . In addition, the FAA plans to satisfy any new...

  5. Molekularbiologische Speziesdifferenzierung

    NASA Astrophysics Data System (ADS)

    Mäde, Dietrich

    Der Speziesnachweis in Lebensmitteln dient der Analyse, aus welchen Tier- und Pflanzenarten die Erzeugnisse hergestellt wurden. Die Information darüber ist sowohl für den Gesundheitsschutz als auch für den Schutz vor Täuschungspraktiken und zur Information des Verbrauchers wichtig.

  6. 77 FR 50420 - Proposed Provision of Navigation Services for the Next Generation Air Transportation System...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-08-21

    ... published a Federal Register Notice (76 FR 77939) requesting comments on the FAA's plans for providing PBN... coordination process, the FAA plans to develop a schedule showing the requisite activities associated with the discontinuance of VOR services. These activities will include timely notification for individual facilities...

  7. 77 FR 51896 - Standard Instrument Approach Procedures, and Takeoff Minimums and Obstacle Departure Procedures...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-08-28

    ... Policies and Procedures (44 FR 11034; February 26, 1979); and (3) does not warrant preparation of a... Alice Intl 2/1083 8/9/12 VOR RWY 31, Amdt 13B. 20-Sep-12 TX Alice Alice Intl 2/1085 8/9/12 LOC/DME...

  8. 77 FR 24369 - Standard Instrument Approach Procedures, and Takeoff Minimums and Obstacle Departure Procedures...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-04-24

    ... ``significant rule'' under DOT Regulatory Policies and Procedures (44 FR 11034; February 26, 1979); and (3) does... Muni, RNAV (GPS) RWY 15, Orig Pocatello, ID, Pocatello Rgnl, VOR RWY 3, Amdt 17 Savanna, IL, Tri-Township, GPS RWY 13, Orig, CANCELLED Savanna, IL, Tri-Township, RNAV (GPS) RWY 13, Orig Savanna, IL,...

  9. 78 FR 47047 - Proposed Policy for Discontinuance of Certain Instrument Approach Procedures

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-08-02

    ... outlined below. This Notice is not a part of the FAA's VOR minimum operating network (MON) initiative... Statement can be found in the Federal Register published on April 11, 2000 (65 FR 19477-19478), as well as at http://DocketsInfo.dot.gov . Docket: Background documents or comments received may be read at...

  10. Vier Jahrhunderte Spannung

    NASA Astrophysics Data System (ADS)

    Loos, Andreas

    2000-06-01

    Im Jahre 1600 begründete William Gilbert die Elektrizitätslehre. Seitdem versuchten die Naturforscher dieses merkwürdige Phänomen zu ergründen und vor allem in Maschinen zu bändigen. Ein an Irrwegen und Gefahren reiches Zeitalter begann.

  11. The human torsional vestibulo-ocular reflex during rotation about an earth-vertical axis.

    PubMed

    Seidman, S H; Leigh, R J

    1989-12-18

    Using the magnetic search coil technique, we have measured the gain and time constant (Tvor) of the torsional vestibulo-ocular reflex (VOR) in 4 subjects who were rotated about an earth-vertical axis with their necks extended and faces supine. Following a 1-min period of rotation in darkness at 50 degrees/s, the post-rotational response to a velocity off-step had a group mean gain of 0.43 and Tvor of 3.7 s. Following a 1-min period of rotation in the light at 50 degrees/s, the post-rotational response in darkness had a group mean gain of 0.29 and Tvor of 4.1 s. Following rotation in darkness with the neck flexed and head prone, the post-rotational response, measured in two subjects, had a mean gain of 0.39 and Tvor of 5.7 s. Similar results were obtained with 100 degrees/s stimuli. In all subjects, the gain and Tvor of the torsional VOR were smaller than corresponding values for their horizontal VOR; these smaller values can be related to the different visual demands made of the torsional VOR.

  12. 76 FR 57902 - Amendment and Establishment of Air Traffic Service Routes; Northeast United States

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-09-19

    ... route J-60, area navigation (RNAV) route Q-42, and VOR Federal airways V-16, V-229 and V-449 (76 FR... noise analysis is required. (See 65 FR 76339; December 6, 2000.) Route Q-62 is a new high altitude route... analysis is required.\\3\\ (See 65 FR 76339; December 6, 2000.) \\2\\ These five ATS routes were studied in...

  13. [Activities of Psychology Dept., California Univ.

    NASA Technical Reports Server (NTRS)

    Bridgeman, Bruce

    1998-01-01

    We have completed two studies during the grant period, with manuscripts published or ready for submission for publication: (1) Dual adaptation and adaptive generalization in the human vestibuloocular reflex and (2) Frequency vs. acceleration specificity in human VOR adaptation. In the 1st study two studies examined the possibility that rotational VOR plasticity is subject to dual adaptation and adaptive generalization. Subjects in the experimental condition were exposed to an altered visual-vestibular environment for about four minutes every day for five consecutive days. The working hours between these testing sessions constituted re-exposure to the normal visual environment. Thus, subjects were repeatedly adapting and re-adapting to both environments which is a condition designed to produce dual adaptation. In each training session a measure of baseline VOR gain was obtained (in the dark). A small laser spot (the only visual stimulus) was systematically moved in the same direction as the subject's head, but by half the angle of rotation (target/head gain = 0.5). This resulted in adaptation values relativized to the non-adapted gain of each subject. These values were then analyzed using an analysis of variance with day and session (within a day) as factors. In the 2nd study human VOR adaption has been assumed to be frequency specific, despite the fact that the semicircular canals are simulated by rotational acceleration and not frequency per se.

  14. Low-frequency otolith and semicircular canal interactions after canal inactivation

    NASA Technical Reports Server (NTRS)

    Angelaki, D. E.; Merfeld, D. M.; Hess, B. J.

    2000-01-01

    During sustained constant velocity and low-frequency off-vertical axis rotations (OVAR), otolith signals contribute significantly to slow-phase eye velocity. The adaptive plasticity of these responses was investigated here after semicircular canal plugging. Inactivation of semicircular canals results in a highly compromised and deficient vestibulo-ocular reflex (VOR). Based on the VOR enhancement hypothesis, one could expect an adaptive increase of otolith-borne angular velocity signals due to combined otolith/canal inputs after inactivation of the semicircular canals. Contrary to expectations, however, the steady-state slow-phase velocity during constant velocity OVAR decreased in amplitude over time. A similar progressive decrease in VOR gain was also observed during low-frequency off-vertical axis oscillations. This response deterioration was present in animals with either lateral or vertical semicircular canals inactivated and was limited to the plane(s) of the plugged canals. The results are consistent with the idea that the low-frequency otolith signals do not simply enhance VOR responses. Rather, the nervous system appears to correlate vestibular sensory information from the otoliths and the semicircular canals to generate an integral response to head motion.

  15. 78 FR 40381 - Establishment of Class E Airspace; Grand Canyon, AZ

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-07-05

    ...) to establish controlled airspace at Grand Canyon, AZ (78 FR 25404). Interested parties were invited... Administration 14 CFR Part 71 Establishment of Class E Airspace; Grand Canyon, AZ AGENCY: Federal Aviation... Canyon VHF Omni-Directional Radio Range/Distance Measuring Equipment (VOR/DME) navigation aid,...

  16. 78 FR 75455 - Standard Instrument Approach Procedures, and Takeoff Minimums and Obstacle Departure Procedures...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-12-12

    ..., Gatlinburg-Pigeon Forge, VOR/DME RWY 10, Amdt 6A Nacogdoches, TX, A L Mangham JR. Rgnl, ILS OR LOC RWY 36... ``significant rule'' under DOT Regulatory Policies and Procedures (44 FR 11034; February 26,1979); and (3)...

  17. Visual Vestibular Interaction in the Dynamic Visual Acuity Test during Voluntary Head Rotation

    NASA Technical Reports Server (NTRS)

    Lee, Moo Hoon; Durnford, Simon; Crowley, John; Rupert, Angus

    1996-01-01

    Although intact vestibular function is essential in maintaining spatial orientation, no good screening tests of vestibular function are available to the aviation community. High frequency voluntary head rotation was selected as a vestibular stimulus to isolate the vestibulo-ocular reflex (VOR) from visual influence. A dynamic visual acuity test that incorporates voluntary head rotation was evaluated as a potential vestibular function screening tool. Twenty-seven normal subjects performed voluntary sinusoidal head rotation at frequencies from 0.7-4.0 Hz under three different visual conditions: visually-enhanced VOR, normal VOR, and visually suppressed VOR. Standardized Baily-Lovie chart letters were presented on a computer monitor in front of the subject, who then was asked to read the letters while rotating his head horizontally. The electro-oculogram and dynamic visual acuity score were recorded and analyzed. There were no significant differences in gain or phase shift among three visual conditions in the frequency range of 2.8 to 4.0 Hz. The dynamic visual acuity score shifted less than 0.3 logMAR at frequencies under 2.0 Hz. The dynamic visual acuity test at frequencies a round 2.0 Hz can be recommended for evaluating vestibular function.

  18. Development of visual-display aid to air navigation

    NASA Technical Reports Server (NTRS)

    Matcovich, T. J.

    1973-01-01

    The developments are discussed in the design of a liquid-crystal, visual display, air navigation aid, which uses two VOR signals to locate the aircraft. The system concepts, liquid crystal materials, stability tests, and the electronic system are described. It is concluded that a navigational aid of this type is technically feasible, but not at the projected low cost.

  19. Vestibulo-Ocular Responses to Vertical Translation using a Hand-Operated Chair as a Field Measure of Otolith Function

    NASA Technical Reports Server (NTRS)

    Wood, S. J.; Campbell, D. J.; Reschke, M. F.; Prather, L.; Clement, G.

    2016-01-01

    The translational Vestibulo-Ocular Reflex (tVOR) is an important otolith-mediated response to stabilize gaze during natural locomotion. One goal of this study was to develop a measure of the tVOR using a simple hand-operated chair that provided passive vertical motion. Binocular eye movements were recorded with a tight-fitting video mask in ten healthy subjects. Vertical motion was provided by a modified spring-powered chair (swopper.com) at approximately 2 Hz (+/- 2 cm displacement) to approximate the head motion during walking. Linear acceleration was measured with wireless inertial sensors (Xsens) mounted on the head and torso. Eye movements were recorded while subjects viewed near (0.5m) and far (approximately 4m) targets, and then imagined these targets in darkness. Subjects also provided perceptual estimates of target distances. Consistent with the kinematic properties shown in previous studies, the tVOR gain was greater with near targets, and greater with vision than in darkness. We conclude that this portable chair system can provide a field measure of otolith-ocular function at frequencies sufficient to elicit a robust tVOR.

  20. Radio direction finder

    NASA Technical Reports Server (NTRS)

    Hershey, L. M.

    1972-01-01

    Three-antenna interferometric system is described for homing on very high frequency transmitters. Antenna signals are sequentially sampled with single receiver and receiver output pulses are held for comparison of signals from outermost antennas with those of center antenna. System can be installed as redundant navigation system in case of failure of VOR receivers.

  1. 78 FR 57472 - IFR Altitudes; Miscellaneous Amendments

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-09-19

    ... ``significant rule'' under DOT Regulatory Policies and Procedures (44 FR 11034; February 26, 1979); and (3) does... Sec. 95.6002 VOR Federal Airway V2 Is Amended To Read in Part BADGER, WI VORTAC SUDDS, WI FIX 2900... BADGER, WI VORTAC MUSKEGON, MI VORTAC 56 BADGER. V216 Is Amended To Delete Changeover Point...

  2. 76 FR 6053 - Standard Instrument Approach Procedures, and Takeoff Minimums and Obstacle Departure Procedures...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-02-03

    ... Policies and Procedures (44 FR 11034; February 26, 1979); and (3) does not warrant preparation of a... 34, Amdt 1 Richmond, VA, Richmond Intl, VOR RWY 2, Amdt 6 On January 10, 2011 (76 FR 06) the FAA... and Obstacle DP, Amdt 2 Berlin, NH, Berlin Rgnl, Takeoff Minimums and Obstacle DP, Amdt 1 Berlin,...

  3. 75 FR 65940 - Standard Instrument Approach Procedures, and Takeoff Minimums and Obstacle Departure Procedures...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-10-27

    ... Policies and Procedures (44 FR 11034; February 26,1979); and (3) does not warrant preparation of a... Intl, VOR RWY 3, Amdt 13 On September 15, 2010 (75 FR 178) the FAA published an Amendment in Docket No... (GPS) RWY 22L, Amdt 1 San Jose, CA, Norman Y. Mineta San Jose Intl, RNAV (RNP) Z RWY 30R, Orig-A...

  4. Neural processing of gravito-inertial cues in humans. I. Influence of the semicircular canals following post-rotatory tilt

    NASA Technical Reports Server (NTRS)

    Zupan, L. H.; Peterka, R. J.; Merfeld, D. M.; Peterson, B. W. (Principal Investigator)

    2000-01-01

    Sensory systems often provide ambiguous information. Integration of various sensory cues is required for the CNS to resolve sensory ambiguity and elicit appropriate responses. The vestibular system includes two types of sensors: the semicircular canals, which measure head rotation, and the otolith organs, which measure gravito-inertial force (GIF), the sum of gravitational force and inertial force due to linear acceleration. According to Einstein's equivalence principle, gravitational force is indistinguishable from inertial force due to linear acceleration. As a consequence, otolith measurements must be supplemented with other sensory information for the CNS to distinguish tilt from translation. The GIF resolution hypothesis states that the CNS estimates gravity and linear acceleration, so that the difference between estimates of gravity and linear acceleration matches the measured GIF. Both otolith and semicircular canal cues influence this estimation of gravity and linear acceleration. The GIF resolution hypothesis predicts that inaccurate estimates of both gravity and linear acceleration can occur due to central interactions of sensory cues. The existence of specific patterns of vestibuloocular reflexes (VOR) related to these inaccurate estimates can be used to test the GIF resolution hypothesis. To investigate this hypothesis, we measured eye movements during two different protocols. In one experiment, eight subjects were rotated at a constant velocity about an earth-vertical axis and then tilted 90 degrees in darkness to one of eight different evenly spaced final orientations, a so-called "dumping" protocol. Three speeds (200, 100, and 50 degrees /s) and two directions, clockwise (CW) and counterclockwise (CCW), of rotation were tested. In another experiment, four subjects were rotated at a constant velocity (200 degrees /s, CW and CCW) about an earth-horizontal axis and stopped in two different final orientations (nose-up and nose-down), a so

  5. The vestibulo-ocular reflex of the squirrel monkey during eccentric rotation and roll tilt.

    PubMed

    Merfeld, D M; Young, L R

    1995-01-01

    The vestibulo-ocular reflexes (VOR) are determined not only by angular acceleration, but also by the presence of gravity and linear acceleration. This phenomenon was studied by measuring three-dimensional nystagmic eye movements, with implanted search coils, in six male squirrel monkeys during eccentric rotation. Monkeys were rotated in the dark at a constant velocity of 200 degrees/s (centrally or 79 cm off axis) with the axis of rotation always aligned with gravity and the spinal axis of the upright monkeys. The monkey's orientation (facing-motion or back-to-motion) had a dramatic influence on the VOR. These experiments show that: (a) the axis of eye rotation always shifted toward alignment with gravito-inertial force; (b) the peak value of horizontal slow phase eye velocity was greater with the monkey facing-motion than with back-to-motion; and (c) the time constant of horizontal eye movement decay was smaller with the monkey facing-motion than with back-to-motion. All of these findings were statistically significant and consistent across monkeys. In another set of tests, the same monkeys were rapidly tilted about their naso-occipital (roll) axis. Tilted orientations of 45 degrees and 90 degrees were maintained for 1 min. Other than a compensatory angular VOR during the angular rotation, no consistent eye velocity response was observed during or following the tilt for any of the six monkeys. The absence of any eye movement response following tilt weighs against the possibility that translational linear VOR responses are due to simple high-pass filtering of the otolith signals. The VOR response during eccentric rotation was divided into the more familiar angular VOR and linear VOR components. The angular component is known to depend upon semicircular canal dynamics and central influences. The linear component of the response decays rapidly with a mean duration of only 6.6 s, while the axis of eye rotation rapidly aligns (< 10 s) with gravito-inertial force. These

  6. The vestibulo-ocular reflex of the squirrel monkey during eccentric rotation and roll tilt

    NASA Technical Reports Server (NTRS)

    Merfeld, D. M.; Young, L. R.

    1995-01-01

    The vestibulo-ocular reflexes (VOR) are determined not only by angular acceleration, but also by the presence of gravity and linear acceleration. This phenomenon was studied by measuring three-dimensional nystagmic eye movements, with implanted search coils, in six male squirrel monkeys during eccentric rotation. Monkeys were rotated in the dark at a constant velocity of 200 degrees/s (centrally or 79 cm off axis) with the axis of rotation always aligned with gravity and the spinal axis of the upright monkeys. The monkey's orientation (facing-motion or back-to-motion) had a dramatic influence on the VOR. These experiments show that: (a) the axis of eye rotation always shifted toward alignment with gravito-inertial force; (b) the peak value of horizontal slow phase eye velocity was greater with the monkey facing-motion than with back-to-motion; and (c) the time constant of horizontal eye movement decay was smaller with the monkey facing-motion than with back-to-motion. All of these findings were statistically significant and consistent across monkeys. In another set of tests, the same monkeys were rapidly tilted about their naso-occipital (roll) axis. Tilted orientations of 45 degrees and 90 degrees were maintained for 1 min. Other than a compensatory angular VOR during the angular rotation, no consistent eye velocity response was observed during or following the tilt for any of the six monkeys. The absence of any eye movement response following tilt weighs against the possibility that translational linear VOR responses are due to simple high-pass filtering of the otolith signals. The VOR response during eccentric rotation was divided into the more familiar angular VOR and linear VOR components. The angular component is known to depend upon semicircular canal dynamics and central influences. The linear component of the response decays rapidly with a mean duration of only 6.6 s, while the axis of eye rotation rapidly aligns (< 10 s) with gravito-inertial force. These

  7. Characterization of the 3D angular vestibulo-ocular reflex in C57BL6 mice.

    PubMed

    Migliaccio, Americo A; Meierhofer, Robert; Della Santina, Charles C

    2011-05-01

    We characterized the three-dimensional angular vestibulo-ocular reflex (3D aVOR) of adult C57BL6 mice during static tilt testing, sinusoidal, and high-acceleration rotations and compared it with that of another lateral-eyed mammal with afoveate retinae (chinchilla) and two primate species with forward eye orientation and retinal foveae (human and squirrel monkey). Noting that visual acuity in mice is poor compared to chinchillas and even worse compared to primates, we hypothesized that the mouse 3D aVOR would be relatively low in gain (eye-velocity/head-velocity) compared to other species and would fall off for combinations of head rotation velocity and frequency for which peak-to-peak position changes fall below the minimum visual angle resolvable by mice. We also predicted that as in chinchilla, the mouse 3D aVOR would be more isotropic (eye/head velocity gain independent of head rotation axis) and better aligned with the axis of head rotation than the 3D aVOR of primates. In 12 adult C57BL6 mice, binocular 3D eye movements were measured in darkness during whole-body static tilts, 20-100°/s whole-body sinusoidal rotations (0.02-10 Hz) and acceleration steps of 3,000°/s² to a 150°/s plateau (dominant spectral content 8-12 Hz). Our results show that the mouse has a robust static tilt counter-roll response gain of ~0.35 (eye-position Δ/head-position Δ) and mid-frequency aVOR gain (~0.6-0.8), but relatively low aVOR gain for high-frequency sinusoidal head rotations and for steps of head rotation acceleration (~0.5). Due to comparatively poor static visual acuity in the mouse, a perfectly compensatory 3D aVOR would confer relatively little benefit during high-frequency, low-amplitude movements. Therefore, our data suggest that the adaptive drive for maintaining a compensatory 3D aVOR depends on the static visual acuity in different species. Like chinchillas, mice have a much more nearly isotropic 3D aVOR than do the primates for which comparable data are

  8. Effects of 4-aminopyridine on nystagmus and vestibulo-ocular reflex in ataxia-telangiectasia.

    PubMed

    Shaikh, Aasef G; Marti, Sarah; Tarnutzer, Alexander A; Palla, Antonella; Crawford, Thomas O; Zee, David S; Straumann, Dominik

    2013-11-01

    Ataxia-telangiectasia (A-T) is a progressive neurodegenerative disorder with prominent eye movement deficits localizing to the cerebellum. We sought to determine if 4-aminopyridine (4-AP), which putatively enhances the precision of Purkinje neurons, could improve the disorders of eye movements and vestibular function in A-T. The influence of 4-AP on disorders of eye movements and vestibular function was studied in four A-T patients. The effects on the cerebellar control of vestibulo-ocular reflex (VOR) was quantitatively assessed by the decay time constant of per- and post-rotational nystagmus during constant velocity en bloc rotations. The length of the VOR time constant determines the fidelity of the vestibular velocity storage, a neural mechanism that increases the bandwidth of VOR under cerebellar control. The VOR time constant was not increased in A-T patients. The latter is explained by the extent of cerebellar lesion as previously described in A-T and other cerebellar disorders. Nevertheless, 4-AP shortened the VOR time constant during horizontal rotations. Severe disinhibition of velocity storage in subjects with putatively profound cerebellar degeneration manifest periodic alternating nystagmus (PAN). Among two A-T subjects who manifested PAN, 4-AP reduced the peak slow phase velocity of the more severely affected individual and abrogated the PAN in the other. Two A-T subjects manifested horizontal and vertical spontaneous nystagmus (SN) in primary gaze, 4-AP reduced its slow phase velocity. We conclude that in subjects with A-T 4-AP has a prominent effect on the ocular motor and vestibular deficits that are ascribed to the loss of cerebellar Purkinje neurons.

  9. Glycine receptor deficiency and its effect on the horizontal vestibulo-ocular reflex: a study on the SPD1J mouse.

    PubMed

    Hübner, Patrick P; Lim, Rebecca; Brichta, Alan M; Migliaccio, Americo A

    2013-04-01

    Inhibition is critical in the pathways controlling the vestibulo-ocular reflex (VOR) and plays a central role in the precision, accuracy and speed of this important vestibular-mediated compensatory eye movement. While γ-aminobutyric acid is the common fast inhibitory neurotransmitter in most of the VOR microcircuits, glycine is also found in key elements. For example, the omnidirectional pause neurons (OPNs) and inhibitory burst neurons in the horizontal VOR both use glycine as their preferred inhibitory neurotransmitter. Determining the precise contribution of glycine to the VOR pathway has been difficult due to the lack of selective tools; however, we used spasmodic mice that have a naturally occurring defect in the glycine receptor (GlyR) that reduces glycinergic transmission. Using this animal model, we compared the horizontal VOR in affected animals with unaffected controls. Our data showed that initial latency and initial peak velocity as well as slow-phase eye movements were unaffected by reduced glycinergic transmission. Importantly however, there were significant effects on quick-phase activity, substantially reducing their number (30-70 %), amplitude (~55 %) and peak velocity (~38 %). We suggest that the OPNs were primarily responsible for the reduced quick-phase properties, since they are part of an unmodifiable, or more 'hard-wired', microcircuit. In contrast, the effects of reduced glycinergic transmission on slow-phases were likely ameliorated by the intrinsically modifiable nature of this pathway. Our results also suggested there is a 'threshold' in GlyR-affected animals, below which the effects of reduced glycinergic transmission were undetected.

  10. The video head impulse test during post-rotatory nystagmus: physiology and clinical implications.

    PubMed

    Mantokoudis, Georgios; Tehrani, Ali S Saber; Xie, Li; Eibenberger, Karin; Eibenberger, Bernhard; Roberts, Dale; Newman-Toker, David E; Zee, David S

    2016-01-01

    The aim of this study was to test the effects of a sustained nystagmus on the head impulse response of the vestibulo-ocular reflex (VOR) in healthy subjects. VOR gain (slow-phase eye velocity/head velocity) was measured using video head impulse test goggles. Acting as a surrogate for a spontaneous nystagmus (SN), a post-rotatory nystagmus (PRN) was elicited after a sustained, constant-velocity rotation, and then head impulses were applied. 'Raw' VOR gain, uncorrected for PRN, in healthy subjects in response to head impulses with peak velocities in the range of 150°/s-250°/s was significantly increased (as reflected in an increase in the slope of the gain versus head velocity relationship) after inducing PRN with slow phases of nystagmus of high intensity (>30°/s) in the same but not in the opposite direction as the slow-phase response induced by the head impulses. The values of VOR gain themselves, however, remained in the normal range with slow-phase velocities of PRN < 30°/s. Finally, quick phases of PRN were suppressed during the first 20-160 ms of a head impulse; the time frame of suppression depended on the direction of PRN but not on the duration of the head impulse. Our results in normal subjects suggest that VOR gains measured using head impulses may have to be corrected for any superimposed SN when the slow-phase velocity of nystagmus is relatively high and the peak velocity of the head movements is relatively low. The suppression of quick phases during head impulses may help to improve steady fixation during rapid head movements. PMID:26449967

  11. Translational Vestibulo-Ocular Reflexes During Off-Vertical Axis Rotation

    NASA Technical Reports Server (NTRS)

    Wood, Scott J.; Clement, Gilles

    2009-01-01

    The translational vestibulo-ocular reflex (tVOR) is an otolith-mediated response that stabilizes near vision during linear acceleration at higher frequencies where visually mediated reflexes are not adequate. The modulation of horizontal and vergence eye movements during Off-Vertical Axis Rotation (OVAR) are presumed to reflect the tVOR in response to the continuously varying linear acceleration in the interaural and nasooccipital axes, respectively. The purpose of this study was to examine the effect of frequency and fixation distance on the modulation of slow phase eye velocity (SPV) as further evidence that the tVOR is elicited during OVAR. Eighteen subjects were rotated about their longitudinal axis tilted by 30 deg off-vertical. Rotational velocities varied between 18 and 288 deg/sec corresponding to a frequency range of 0.05 to 0.8 Hz. Fixation distance was altered by asking subjects to imagine stationary targets that were briefly presented at 0.5, 1 and 2 m during some rotation cycles. The target flash was 40 msec in the nose-up position at eye level. Oculomotor responses were recorded in the dark using infrared binocular videography. Sinusoidal curve fits were used to derive amplitude, phase and bias velocity of the eye movements across multiple rotation cycles. Consistent with previous studies, the modulation of both horizontal and vergence SPV increased with stimulus frequency. The effect of fixation distance was negligible at lower frequencies. The modulation of horizontal and vergence SPV was; however, proportional to fixation distance during OVAR at 0.8 Hz. This increasing sensitivity and dependence on fixation distance of horizontal and vergence SPV during OVAR is consistent with tVOR characteristics measured during other types of linear motion. We conclude that the modulation of horizontal and vergence SPV will be diagnostically more useful at higher stimulus frequencies where the tVOR is more robust.

  12. Dynamic properties of the human vestibulo-ocular reflex during head rotations in roll

    NASA Technical Reports Server (NTRS)

    Seidman, S. H.; Leigh, R. J.; Tomsak, R. L.; Grant, M. P.; Dell'Osso, L. F.

    1995-01-01

    We investigated the dynamic properties of the human vestibulo-ocular reflex (VOR) during roll head rotations in three human subjects using the magnetic search coil technique. In the first of two experiments, we quantify the behavior of the ocular motor plant in the torsional plane. The subject's eye was mechanically displaced into intorsion, extorsion or abduction, and the dynamic course of return of the eye to its resting position was measured. The mean predominant time constants of return were 210 msec from intorsion, 83 msec from extorsion, and 217 msec from abduction, although there was considerable variability of results from different trials and subjects. In the second experiment, we quantify the efficacy of velocity-to-position integration of the vestibular signal. Position-step stimuli were used to test the torsional or horizontal VOR, being applied with subjects heads erect or supine. After a torsional position-step, the eye drifted back to its resting position, but after a horizontal position-step the eye held its new horizontal position. To interpret these responses we used a simple model of the VOR with parameters of the ocular motor plant set to values determined during Exp 1. The time constant of the velocity-to-position neural integrator was smaller (typically 2 sec) in the torsional plane than in the horizontal plane (> 20 sec). No disconjugacy of torsional eye movements was observed. Thus, the dynamic properties of the VOR in roll differ significantly from those of the VOR in yaw, reflecting different visual demands placed on this reflex in these two planes.

  13. Characterization of 2-ketoisovalerate ferredoxin oxidoreductase, a new and reversible coenzyme A-dependent enzyme involved in peptide fermentation by hyperthermophilic archaea.

    PubMed Central

    Heider, J; Mai, X; Adams, M W

    1996-01-01

    Cell extracts of the proteolytic and hyperthermophilic archaea Thermococcus litoralis, Thermococcus sp. strain ES-1, Pyrococcus furiosus, and Pyrococcus sp. strain ES-4 contain an enzyme which catalyzes the coenzyme A-dependent oxidation of branched-chain 2-ketoacids coupled to the reduction of viologen dyes or ferredoxin. This enzyme, termed VOR (for keto-valine-ferredoxin oxidoreductase), has been purified from all four organisms. All four VORs comprise four different subunits and show amino-terminal sequence homology. T. litoralis VOR has an M(r) of ca. 230,000, with subunit M(r) values of 47,000 (alpha), 34,000 (beta), 23,000 (gamma), and 13,000 (delta). It contains about 11 iron and 12 acid-labile sulfide atoms and 13 cysteine residues per heterotetramer (alpha beta gamma delta), but thiamine pyrophosphate, which is required for catalytic activity, was lost during purification. The most efficient substrates (kcat/Km > 1.0 microM-1 s-1; Km < 100 microM) for the enzyme were the 2-ketoacid derivatives of valine, leucine, isoleucine, and methionine, while pyruvate and aryl pyruvates were very poor substrates (kcat/Km < 0.2 microM-1 s-1) and 2-ketoglutarate was not utilized. T. litoralis VOR also functioned as a 2-ketoisovalerate synthase at 85 degrees C, producing 2-ketoisovalerate and coenzyme A from isobutyryl-coenzyme A (apparent Km, 250 microM) and CO2 (apparent Km, 48 mM) with reduced viologen as the electron donor. The rate of 2-ketoisovalerate synthesis was about 5% of the rate of 2-ketoisovalerate oxidation. The optimum pH for both reactions was 7.0. A mechanism for 2-ketoisovalerate oxidation based on data from substrate-induced electron paramagnetic resonance spectra is proposed, and the physiological role of VOR is discussed. PMID:8550513

  14. Ocular motor responses to abrupt interaural head translation in normal humans

    NASA Technical Reports Server (NTRS)

    Ramat, Stefano; Zee, David S.; Shelhamer, M. J. (Principal Investigator)

    2003-01-01

    We characterized the interaural translational vestibulo-ocular reflex (tVOR) in 6 normal humans to brief (approximately 200 ms), high-acceleration (0.4-1.4g) stimuli, while they fixed targets at 15 or 30 cm. The latency was 19 +/- 5 ms at 15-cm and 20 +/- 12 ms at 30-cm viewing. The gain was quantified using the ratio of actual to ideal behavior. The median position gain (at time of peak head velocity) was 0.38 and 0.37, and the median velocity gain, 0.52 and 0.62, at 15- and 30-cm viewing, respectively. These results suggest the tVOR scales proportionally at these viewing distances. Likewise, at both viewing distances, peak eye velocity scaled linearly with peak head velocity and gain was independent of peak head acceleration. A saccade commonly occurred in the compensatory direction, with a greater latency (165 vs. 145 ms) and lesser amplitude (1.8 vs. 3.2 deg) at 30- than 15-cm viewing. Even with saccades, the overall gain at the end of head movement was still considerably undercompensatory (medians 0.68 and 0.77 at 15- and 30-cm viewing). Monocular viewing was also assessed at 15-cm viewing. In 4 of 6 subjects, gains were the same as during binocular viewing and scaled closely with vergence angle. In sum the low tVOR gain and scaling of the response with viewing distance and head velocity extend previous results to higher acceleration stimuli. tVOR latency (approximately 20 ms) was lower than previously reported. Saccades are an integral part of the tVOR, and also scale with viewing distance.

  15. Effect of viewing distance on the generation of vertical eye movements during locomotion

    NASA Technical Reports Server (NTRS)

    Moore, S. T.; Hirasaki, E.; Cohen, B.; Raphan, T.

    1999-01-01

    Vertical head and eye coordination was studied as a function of viewing distance during locomotion. Vertical head translation and pitch movements were measured using a video motion analysis system (Optotrak 3020). Vertical eye movements were recorded using a video-based pupil tracker (Iscan). Subjects (five) walked on a linear treadmill at a speed of 1.67 m/s (6 km/h) while viewing a target screen placed at distances ranging from 0.25 to 2.0 m at 0. 25-m intervals. The predominant frequency of vertical head movement was 2 Hz. In accordance with previous studies, there was a small head pitch rotation, which was compensatory for vertical head translation. The magnitude of the vertical head movements and the phase relationship between head translation and pitch were little affected by viewing distance, and tended to orient the naso-occipital axis of the head at a point approximately 1 m in front of the subject (the head fixation distance or HFD). In contrast, eye velocity was significantly affected by viewing distance. When viewing a far (2-m) target, vertical eye velocity was 180 degrees out of phase with head pitch velocity, with a gain of 0. 8. This indicated that the angular vestibulo-ocular reflex (aVOR) was generating the eye movement response. The major finding was that, at a close viewing distance (0.25 m), eye velocity was in phase with head pitch and compensatory for vertical head translation, suggesting that activation of the linear vestibulo-ocular reflex (lVOR) was contributing to the eye movement response. There was also a threefold increase in the magnitude of eye velocity when viewing near targets, which was consistent with the goal of maintaining gaze on target. The required vertical lVOR sensitivity to cancel an unmodified aVOR response and generate the observed eye velocity magnitude for near targets was almost 3 times that previously measured. Supplementary experiments were performed utilizing body-fixed active head pitch rotations at 1 and 2 Hz

  16. Non-linear eye movements during visual-vestibular interaction under body oscillation with step-mode lateral linear acceleration.

    PubMed

    Mori, Shigeo; Katayama, Naomi

    2005-02-01

    We investigated visual-vestibular interactions in normal humans, where a constant speed of optokinetic stimulation was combined with whole body oscillation of lateral linear acceleration (10 m stroke). The acceleration mode was not sinusoidal, but rectangular (step). The pure optokinetic reflex (reference OKR) and the OKR under combined stimulation (combined OKR) were induced by a random-dot pattern projected onto a hemispherical dome-screen affixed to a chair on a linear accelerator. The translational vestibulo-ocular reflex (tVOR) was determined separately in the dark during acceleration-step oscillation. Since the tVOR was masked by the OKR under combined stimulation, the interaction was assessed as changes in combined-OKR velocity at two segments of opposing acceleration; in other words, tVOR directions identical to (agonistic) and opposite to (antagonistic) the OKR direction. When a moderate optokinetic stimulus-speed of 40 deg/s was combined with a moderate acceleration of 0.3 G (3.0 m/s2) as in Experiment 1 (N=10), the combined-OKR velocity always increased during the agonistic condition, and the motion of the visual pattern was perceived as slow and clear in this segment. On the other hand, during the antagonistic condition, the combined-OKR velocity either remained unchanged or increased moderately, and the motion of the visual pattern was sensed as fast and unclear. Notably, in most subjects, the velocity difference in combined-OKR between the agonistic and antagonistic conditions was around the value of the tVOR velocity. In five of the ten subjects who completed an additional test session with the acceleration level increased from 0.3 to 0.5 G (4.9 m/s2), similar findings were maintained individually, suggesting independent behavior of tVOR. Therefore, we hypothesized that the interaction could be direction-selective; in other words, both tVOR and OKR are additive during the agonistic condition, but tVOR is suppressed during the antagonistic condition

  17. Flexibility of vestibulo-ocular reflex adaptation to modified visual input in human.

    PubMed

    Watanabe, Shoji; Hattori, Kosuke; Koizuka, Izumi

    2003-02-01

    The vestibulo-ocular reflex (VOR) serves to keep images relatively stable on the retina. To maintain appropriate performance and minimize image slip throughout life, VOR is subjected to long-term adaptive regulation by visual input. It has been reported that adaptive changes in VOR gain (eye velocity/head velocity) are evoked either by fitting subjects with magnifying, miniaturizing, or reversing spectacles during normal behavior, or by moving a large visual field in or out of phase relative to the subject's head movement. The changes in VOR gain are frequency selective. Here, we examine the extent of VOR gain flexibility by causing VORs of similar direction to undergo different behavioral gain changes. Nine healthy adults participated in the study, ranging in age from 24 to 38 years (mean: 26 years) and with no history of neurotological symptoms. All subjects were clinically normal according to a screening battery that included combined neurologic and otologic physical examinations. Horizontal and vertical eye positions were recorded by bitemporal DC-coupled electro-oculography (EOG). The subject sat in a rotating chair. The axis of rotation of the body was always earth-vertical, with the interaural axis crossing the axis of rotation of the chair. The head was pointed 20 degrees downwards in all experiments and stabilized in this position using a chin rest. The chair was surrounded by a half-cylindrical optokinetic screen (78 cm in diameter) placed in front of the subject, onto which random dot patterns were projected. Goggles were used to ensure that the subject was in complete darkness during both pre- and postadaptation periods. The chair was rotated sinusoidally at maximum amplitude of 30 degrees or 60 degrees : for 30 degrees the stimulation was at 0.1, 0.2, 0.3, and 0.4 Hz; for 60 degrees it was at 0.1, 0.2, and 0.3 Hz. VOR adaptation was obtained by inducing a retinal slip velocity by short-term alteration of the visual input of the large field; this change

  18. Characterizing high-velocity angular vestibulo-ocular reflex function in service members post-blast exposure.

    PubMed

    Scherer, Matthew R; Shelhamer, Mark J; Schubert, Michael C

    2011-02-01

    Blasts (explosions) are the most common mechanism of injury in modern warfare. Traumatic brain injury (TBI) and dizziness are common sequelae associated with blasts, and many service members (SMs) report symptoms worsen with activity. The purpose of this study was to measure angular vestibulo-ocular reflex gain (aVOR) of blast-exposed SMs with TBI during head impulse testing. We also assessed their symptoms during exertion. Twenty-four SMs recovering from TBI were prospectively assigned to one of two groups based on the presence or absence of dizziness. Wireless monocular scleral search coil and rate sensor were used to characterize active and passive yaw and pitch head and eye rotations. Visual analog scale (VAS) was used to monitor symptoms during fast walking/running. For active yaw head impulses, aVOR gains were significantly lower in the symptomatic group (0.79 ± 0.15) versus asymptomatic (0.87 ± 0.18), but not for passive head rotation. For pitch head rotation, the symptomatic group had both active (0.915 ± 0.24) and passive (0.878 ± 0.22) aVOR gains lower than the asymptomatic group (active 1.03 ± 0.27, passive 0.97 ± 0.23). Some SMs had elevated aVOR gain. VAS scores for all symptoms were highest during exertion. Our data suggest symptomatic SMs with TBI as a result of blast have varied aVOR gain during high-velocity head impulses and provide compelling evidence of pathology affecting the vestibular system. Potential loci of injury in this population include the following: disruption of pathways relaying vestibular efference signals, differential destruction of type I vestibular hair cells, or selective damage to irregular afferent pathways-any of which may explain the common discrepancy between reports of vestibular-like symptoms and laboratory testing results. Significantly reduced pitch aVOR in symptomatic SMs and peak symptom severity during exertional testing support earlier findings in the chronic blast-exposed active duty SMs.

  19. The effect of vestibulo-ocular reflex deficits and covert saccades on dynamic vision in opioid-induced vestibular dysfunction.

    PubMed

    Ramaioli, Cecilia; Colagiorgio, Paolo; Sağlam, Murat; Heuser, Fabian; Schneider, Erich; Ramat, Stefano; Lehnen, Nadine

    2014-01-01

    Patients with bilateral vestibular dysfunction cannot fully compensate passive head rotations with eye movements, and experience disturbing oscillopsia. To compensate for the deficient vestibulo-ocular reflex (VOR), they have to rely on re-fixation saccades. Some can trigger "covert" saccades while the head still moves; others only initiate saccades afterwards. Due to their shorter latency, it has been hypothesized that covert saccades are particularly beneficial to improve dynamic visual acuity, reducing oscillopsia. Here, we investigate the combined effect of covert saccades and the VOR on clear vision, using the Head Impulse Testing Device-Functional Test (HITD-FT), which quantifies reading ability during passive high-acceleration head movements. To reversibly decrease VOR function, fourteen healthy men (median age 26 years, range 21-31) were continuously administrated the opioid remifentanil intravenously (0.15 µg/kg/min). VOR gain was assessed with the video head-impulse test, functional performance (i.e. reading) with the HITD-FT. Before opioid application, VOR and dynamic reading were intact (head-impulse gain: 0.87±0.08, mean±SD; HITD-FT rate of correct answers: 90±9%). Remifentanil induced impairment in dynamic reading (HITD-FT 26±15%) in 12/14 subjects, with transient bilateral vestibular dysfunction (head-impulse gain 0.63±0.19). HITD-FT score correlated with head-impulse gain (R = 0.63, p = 0.03) and with gain difference (before/with remifentanil, R = -0.64, p = 0.02). One subject had a non-pathological head-impulse gain (0.82±0.03) and a high HITD-FT score (92%). One subject triggered covert saccades in 60% of the head movements and could read during passive head movements (HITD-FT 93%) despite a pathological head-impulse gain (0.59±0.03) whereas none of the 12 subjects without covert saccades reached such high performance. In summary, early catch-up saccades may improve dynamic visual function. HITD-FT is an appropriate method

  20. A critical period for functional vestibular development in zebrafish

    NASA Technical Reports Server (NTRS)

    Moorman, Stephen J.; Cordova, Rodolfo; Davies, Sarah A.

    2002-01-01

    We have determined a critical period for vestibular development in zebrafish by using a bioreactor designed by NASA to simulate microgravity for cells in culture. A critical period is defined as the briefest period of time during development when stimulus deprivation results in long lasting or permanent sensory deficits. Zebrafish eggs were collected within 3 hours of being laid and fertilized. In experiment 1, eggs were placed in the bioreactor at 3, 24, 30, 36, 48, or 72 hours postfertilization (hPF) and maintained in the bioreactor until 96 hPF. In experiment 2, eggs were placed in the bioreactor immediately after they were collected and maintained in the bioreactor until 24, 36, 48, 60, 66, 72, or 96 hPF. Beginning at 96 hPF, all larvae had their vestibulo-ocular reflexes (VOR) evaluated once each day for 5 days. Only larvae that hatched from eggs that were placed in the bioreactor before 30 hPF in experiment 1 or removed from the bioreactor later than 66 hPF in experiment 2 had VOR deficits that persisted for at least 5 days. These data suggest a critical period for vestibular development in the zebrafish that begins before 30 hPF and ends after 66 hPF. To confirm this, zebrafish eggs were placed in the bioreactor at 24 hPF and removed at 72 hPF. VORs were evaluated in these larvae once each day for 5 days beginning at 96 hPF. These larvae had VOR deficits that persisted for at least 5 days. In addition, larvae that had been maintained in the bioreactor from 24 to 66 hPF or from 30 to 72 hPF, had only temporary VOR deficits. In a final experiment, zebrafish eggs were placed in the bioreactor at 3 hPF and removed at 96 hPF but the bioreactor was turned off from 24 hPF to 72 hPF. These larvae had normal VORs when they were removed from the bioreactor at 96 hPF. Taken as a whole, these data support the idea that there is a critical period for functional maturation of the zebrafish vestibular system. The developmental period identified includes the timeframe

  1. Characterizing high-velocity angular vestibulo-ocular reflex function in service members post-blast exposure

    PubMed Central

    Scherer, Matthew R.; Shelhamer, Mark J.; Schubert, Michael C.

    2011-01-01

    Blasts (explosions) are the most common mechanism of injury in modern warfare. Traumatic brain injury (TBI) and dizziness are common sequelae associated with blasts, and many service members (SMs) report symptoms worsen with activity. The purpose of this study was to measure angular vestibulo-ocular reflex gain (aVOR) of blast-exposed SMs with TBI during head impulse testing. We also assessed their symptoms during exertion. Twenty-four SMs recovering from TBI were prospectively assigned to one of two groups based on the presence or absence of dizziness. Wireless monocular scleral search coil and rate sensor were used to characterize active and passive yaw and pitch head and eye rotations. Visual analog scale (VAS) was used to monitor symptoms during fast walking/running. For active yaw head impulses, aVOR gains were significantly lower in the symptomatic group (0.79 ± 0.15) versus asymptomatic (0.87 ± 0.18), but not for passive head rotation. For pitch head rotation, the symptomatic group had both active (0.915 ± 0.24) and passive (0.878 ± 0.22) aVOR gains lower than the asymptomatic group (active 1.03 ± 0.27, passive 0.97 ± 0.23). Some SMs had elevated aVOR gain. VAS scores for all symptoms were highest during exertion. Our data suggest symptomatic SMs with TBI as a result of blast have varied aVOR gain during high-velocity head impulses and provide compelling evidence of pathology affecting the vestibular system. Potential loci of injury in this population include the following: disruption of pathways relaying vestibular efference signals, differential destruction of type I vestibular hair cells, or selective damage to irregular afferent pathways—any of which may explain the common discrepancy between reports of vestibular-like symptoms and laboratory testing results. significantly reduced pitch aVOR in symptomatic SMs and peak symptom severity during exertional testing support earlier findings in the chronic blast-exposed active duty SMs. PMID:21113582

  2. Visually induced adaptation in three-dimensional organization of primate vestibuloocular reflex

    NASA Technical Reports Server (NTRS)

    Angelaki, D. E.; Hess, B. J.

    1998-01-01

    The adaptive plasticity of the spatial organization of the vestibuloocular reflex (VOR) has been investigated in intact and canal-plugged primates using 2-h exposure to conflicting visual (optokinetic, OKN) and vestibular rotational stimuli about mutually orthogonal axes (generating torsional VOR + vertical OKN, torsional VOR + horizontal OKN, vertical VOR + horizontal OKN, and horizontal VOR + vertical OKN). Adaptation protocols with 0.5-Hz (+/-18 degrees ) head movements about either an earth-vertical or an earth-horizontal axis induced orthogonal response components as high as 40-70% of those required for ideal adaptation. Orthogonal response gains were highest at the adapting frequency with phase leads present at lower and phase lags present at higher frequencies. Furthermore, the time course of adaptation, as well as orthogonal response dynamics were similar and relatively independent of the particular visual/vestibular stimulus combination. Low-frequency (0. 05 Hz, vestibular stimulus: +/-60 degrees ; optokinetic stimulus: +/-180 degrees ) adaptation protocols with head movements about an earth-vertical axis induced smaller orthogonal response components that did not exceed 20-40% of the head velocity stimulus (i.e., approximately 10% of that required for ideal adaptation). At the same frequency, adaptation with head movements about an earth-horizontal axis generated large orthogonal responses that reached values as high as 100-120% of head velocity after 2 h of adaptation (i.e., approximately 40% of ideal adaptation gains). The particular spatial and temporal response characteristics after low-frequency, earth-horizontal axis adaptation in both intact and canal-plugged animals strongly suggests that the orienting (and perhaps translational) but not inertial (velocity storage) components of the primate otolith-ocular system exhibit spatial adaptability. Due to the particular nested arrangement of the visual and vestibular stimuli, the optic flow pattern

  3. Horizontal vestibuloocular reflex evoked by high-acceleration rotations in the squirrel monkey. III. Responses after labyrinthectomy

    NASA Technical Reports Server (NTRS)

    Lasker, D. M.; Hullar, T. E.; Minor, L. B.; Shelhamer, M. J. (Principal Investigator)

    2000-01-01

    The horizontal angular vestibuloocular reflex (VOR) evoked by high-frequency, high-acceleration rotations was studied in four squirrel monkeys after unilateral labyrinthectomy. Spontaneous nystagmus was measured at the beginning and end of each testing session. During the period that animals were kept in darkness (4 days), the nystagmus at each of these times measured approximately 20 degrees /s. Within 18-24 h after return to the light, the nystagmus (measured in darkness) decreased to 2.8 +/- 1.5 degrees /s (mean +/- SD) when recorded at the beginning but was 20.3 +/- 3.9 degrees /s at the end of the testing session. The latency of the VOR measured from responses to steps of acceleration (3,000 degrees /s(2) reaching a velocity of 150 degrees /s) was 8.4 +/- 0.3 ms for responses to ipsilesional rotations and 7.7 +/- 0.4 ms for contralesional rotations. During the period that animals were kept in darkness after the labyrinthectomy, the gain of the VOR measured during the steps of acceleration was 0.67 +/- 0.12 for contralesional rotations and 0.39 +/- 0.04 for ipsilesional rotations. Within 18-24 h after return to light, the VOR gain for contralesional rotations increased to 0.87 +/- 0.08, whereas there was only a slight increase for ipsilesional rotations to 0.41 +/- 0. 06. A symmetrical increase in the gain measured at the plateau of head velocity was noted after the animals were returned to light. The VOR evoked by sinusoidal rotations of 2-15 Hz, +/-20 degrees /s, showed a better recovery of gain at lower (2-4 Hz) than at higher (6-15 Hz) frequencies. At 0.5 Hz, gain decreased symmetrically when the peak amplitude was increased from 20 to 100 degrees /s. At 10 Hz, gain was decreased for ipsilesional half-cycles and increased for contralesional half-cycles when velocity was raised from 20 to 50 degrees /s. A model incorporating linear and nonlinear pathways was used to simulate the data. Selective increases in the gain for the linear pathway accounted for the

  4. Horizontal vestibuloocular reflex evoked by high-acceleration rotations in the squirrel monkey. I. Normal responses

    NASA Technical Reports Server (NTRS)

    Minor, L. B.; Lasker, D. M.; Backous, D. D.; Hullar, T. E.; Shelhamer, M. J. (Principal Investigator)

    1999-01-01

    The horizontal angular vestibuloocular reflex (VOR) evoked by high-frequency, high-acceleration rotations was studied in five squirrel monkeys with intact vestibular function. The VOR evoked by steps of acceleration in darkness (3,000 degrees /s(2) reaching a velocity of 150 degrees /s) began after a latency of 7.3 +/- 1.5 ms (mean +/- SD). Gain of the reflex during the acceleration was 14.2 +/- 5.2% greater than that measured once the plateau head velocity had been reached. A polynomial regression was used to analyze the trajectory of the responses to steps of acceleration. A better representation of the data was obtained from a polynomial that included a cubic term in contrast to an exclusively linear fit. For sinusoidal rotations of 0.5-15 Hz with a peak velocity of 20 degrees /s, the VOR gain measured 0.83 +/- 0.06 and did not vary across frequencies or animals. The phase of these responses was close to compensatory except at 15 Hz where a lag of 5.0 +/- 0.9 degrees was noted. The VOR gain did not vary with head velocity at 0.5 Hz but increased with velocity for rotations at frequencies of >/=4 Hz (0. 85 +/- 0.04 at 4 Hz, 20 degrees /s; 1.01 +/- 0.05 at 100 degrees /s, P < 0.0001). No responses to these rotations were noted in two animals that had undergone bilateral labyrinthectomy indicating that inertia of the eye had a negligible effect for these stimuli. We developed a mathematical model of VOR dynamics to account for these findings. The inputs to the reflex come from linear and nonlinear pathways. The linear pathway is responsible for the constant gain across frequencies at peak head velocity of 20 degrees /s and also for the phase lag at higher frequencies being less than that expected based on the reflex delay. The frequency- and velocity-dependent nonlinearity in VOR gain is accounted for by the dynamics of the nonlinear pathway. A transfer function that increases the gain of this pathway with frequency and a term related to the third power of head

  5. Neural basis for motor learning in the vestibuloocular reflex of primates. III. Computational and behavioral analysis of the sites of learning.

    PubMed

    Lisberger, S G

    1994-08-01

    1. We have used a combination of eye movement recordings and computer modeling to study long-term adaptive modification (motor learning) in the vestibuloocular reflex (VOR). The eye movement recordings place constraints on possible sites for motor learning. The computer model abides by these constraints, as well as constraints provided by data in previous papers, to formalize a new hypothesis about the sites of motor learning. The model was designed to reproduce as much of the existing neural and behavioral data as possible. 2. Motor learning was induced in monkeys by fitting them with spectacles that caused the gain of the VOR (eye speed divided by head speed) to increase to values > 1.6 or to decrease to values < 0.4. We elicited pursuit by providing ramp motion of a small target at 30 degrees/s along the horizontal axis. Changes in the gain of the VOR caused only small and inconsistent changes in the eye acceleration in the first 100 ms after the onset of pursuit and had no effect on the eye velocity during tracking of steady target motion. Electrical stimulation in the flocculus and ventral paraflocculus with single pulses or trains of pulses caused smooth eye movement toward the side of stimulation after latencies of 9-11 ms. Neither the latency, the peak eye velocity, nor the initial eye acceleration varied as a consistent function of the gain of the VOR. 3. The computer model contained nodes that represented position-vestibular-pause cells (PVP-cells) and flocculus target neurons (FTNs) in the vestibular nucleus, and horizontal gaze-velocity Purkinje cells (HGVP-cells) in the cerebellar flocculus and ventral paraflocculus. Node FTN represented only the "E-c FTNs," which show increased firing for eye motion away from the side of recording. The transfer functions in the model included dynamic elements (filters) as well as static elements (summing junctions, gain elements, and time delays). Except for the transfer functions that converted visual motion inputs

  6. Latency and initiation of the human vestibuloocular reflex to pulsed galvanic stimulation.

    PubMed

    Aw, Swee T; Todd, Michael J; Halmagyi, G Michael

    2006-08-01

    Cathodal galvanic currents activate primary vestibular afferents, whereas anodal currents inhibit them. Pulsed galvanic vestibular stimulation (GVS) was used to determine the latency and initiation of the human vestibuloocular reflex. Three-dimensional galvanic vestibuloocular reflex (g-VOR) was recorded with binocular dual-search coils in response to a bilateral bipolar 100-ms rectangular pulse of current at 0.9 (near-threshold), 2.5, 5.0, 7.5, and 10.0 mA in 11 normal subjects. The g-VOR consisted of three components: conjugate torsional eye rotation away from cathode toward anode; vertical divergence (skew deviation) with hypertropia of the eye on the cathodal and hypotropia of the eye on the anodal sides; and conjugate horizontal eye rotation away from cathode toward anode. The g-VOR was repeatable across all subjects, its magnitude a linear function of the current intensity, its latency about 9.0 ms with GVS of >or=2.5 mA, and was not suppressed by visual fixation. At 10-mA stimulation, the g-VOR [x, y, z] on the cathodal side was [0.77 +/- 0.10, -0.05 +/- 0.05, -0.18 +/- 0.06 degrees ] (mean +/- 95% confidence intervals) and on the anodal side was [0.79 +/- 0.10, 0.16 +/- 0.05, -0.19 +/- 0.06 degrees ], with a vertical divergence of 0.20 degrees . Although the horizontal g-VOR could have arisen from activation of the horizontal semicircular canal afferents, the vertical-torsional g-VOR resembled the vestibuloocular reflex in response to roll-plane head rotation about an Earth-horizontal axis and might be a result of both vertical semicircular canal and otolith afferent activations. Pulsed GVS is a promising technique to investigate latency and initiation of the human vestibuloocular reflex because it does not require a large mechanical apparatus nor does it pose problems of head inertia or slippage.

  7. The Chinchilla's vestibulo-ocular reflex

    NASA Technical Reports Server (NTRS)

    Merwin, W. H., Jr.; Wall, Conrad, III; Tomko, D. L.

    1989-01-01

    The horizontal vestibulo-ocular reflex (VOR) was measured and characterized in seven adult chinchillas using 0.01 to 1.0 Hz angular velocity sinusoids. Gains were less than compensatory, and were variable from day to day, but phases were highly repeatable both within and between animals. The best fitting transfer function to the average data of all animals had a dominant time constant of 7.5 sec, and an adaptation operator with a time constant of 24.0 sec. There were certain nonlinearities in the horizontal VOR of this animal, and it was difficult to elicit a robust optokinetic response. Results are discussed in relation to similar measurements in other species.

  8. Simulation und virtuelle Realität

    NASA Astrophysics Data System (ADS)

    von Estorff, Otto; Markiewicz, Marian; Özkan, Ali; Zaleski, Olgierd; Blumrich, Reinhard; Genuit, Klaus; Fiebig, André

    Mit Hilfe akustischer Berechnungen ist es möglich, aufwendige Messungen an Fahrzeugprototypen deutlich zu reduzieren. Dieses Kapitel gibt einen kurzen Überblick über die wichtigsten derzeit verfügbaren Methoden. Dabei wird zunächst auf Elementverfahren, wie die Finite-Elemente-Methode (FEM) und die Boundary-Elemente-Methode (BEM), näher eingegangen. Während diese vor allem im tieffrequenten Bereich eingesetzt werden, kommen bei höheren Frequenzen vermehrt Verfahren zum Einsatz, die auf Energieformulierungen beruhen. Exemplarisch wird hier die Funktionsweise und der Einsatz der Statistischen-Energie-Analyse (SEA) erläutert. Anhand von repräsentativen Beispielen werden die Einsatzmöglichkeiten und Grenzen der verschiedenen Verfahren aufgezeigt, wobei vor allem auch auf Vergleiche zwischen Rechnung und Messung eingegangen wird.

  9. Etiologic Agents and Antifungal Susceptibility of Oral Candidosis from Romanian patients with HIV-infection or type 1 diabetes mellitus.

    PubMed

    Minea, Bogdan; Nastasa, Valentin; Kolecka, Anna; Mares, Magdalena; Marangoci, Narcisa; Rosca, Irina; Pinteala, Mariana; Hancianu, Monica; Mares, Mihai

    2016-01-01

    This is the first Romanian investigation of oral candidosis in patients suffering of HIV-infection or type 1 diabetes mellitus (T1DM). Candida albicans was the dominant species in both types of isolates: n = 14 (46.7%) in T1DM, n = 60 (69.8%) in HIV. The most frequent non-albicans Candida spp. were Candida kefyr (n = 6; 20%) in T1DM and Candida dubliniensis (n = 8; 9.3%) in HIV. Resistance to fluconazole was detected only in the HIV non-albicans Candida group (n = 8; 9.3%). All isolates were susceptible to VOR. The experimental drug MXP had MIC values equal or close to the ones of VOR. Echinocandin resistance was more frequent than azole resistance. PMID:27282005

  10. SARCOPTERYGII, Fleischflosser

    NASA Astrophysics Data System (ADS)

    Schultze, Hans-Peter

    Unter den rezenten und fossilen Fischen sind die Sarcopterygier durch fleischige Loben an den paarigen Flossen charakterisiert. Fossil gehen sie bis in das Obere Silur (vor 420 Mio. Jahren) zurück. Einige Gruppen (†Onychodontida, †Porolepiformes, †Elpistostegalia) waren auf das Devon beschränkt, andere verschwanden gegen Ende des Paläozoikums (†Rhizodontida, †Osteolepiformes). Nur wenige Arten der Dipnoi (Lungenfische) und Actinistia (Hohlstachler) haben überlebt; aus einer ausgestorbenen Teilgruppe evolvierten die erfolgreichen Tetrapoda. Im Devon waren die Sarcopterygier weltweit verbreitet; ihre rezenten fischartigen Formen sind dagegen auf die Südkontinente bzw. den Indischen Ozean beschränkt. Ursprünglich waren alle Formen marin. Mehrmals unabhängig wurde von ihnen das Süßwasser und innerhalb der Tetrapoden vor allem das Land erobert.

  11. "Das Konkrete ist das Abstrakte, an das man sich schließlich gewöhnt hat." (Laurent Schwartz) Über den Ablauf des mathematischen Verstehens

    NASA Astrophysics Data System (ADS)

    Lowsky, Martin

    Die im Titel genannte Aussage findet sich in den Lebenserinnerungen von Laurent Schwartz (1915-2002), einem der fruchtbarsten Mathematiker, Mitglied der Gruppe Bourbaki. Im Original lautet die Aussage: "un objet concret est un objet abstrait auquel on a fini par s'habituer." Schwartz erläutert sie am Beispiel des Integrals über {e^{-1/2{x^2}}} , das den Wert Wurzel aus 2π hat und in dem sich also die Zahlen e und π verknüpfen. Was Schwartz aber vor allem ausdrücken will, ist dies: Das mathematische Verständnisd geht langsam vor sich und es bedarf der Anstrengung. "Es ist eine Frage der Zeit und der Energie", sagt Schwartz, und gerade dies mache es so schwer, die höhere Mathematik unter das Volk zu bringen. Das Lernen und Lehren von Mathematik laufe eben mühevoll und langsam ab.

  12. Navigation Signal Disturbances by Multipath Propagation - Scaled Measurements with a Universal Channel Sounder Architecture

    NASA Astrophysics Data System (ADS)

    Geise, Robert; Neubauer, Bjoern; Zimmer, Georg

    2015-11-01

    The performance of navigation systems is always reduced by unwanted multipath propagation. This is especially of practical importance for airborne navigation systems like the instrument landing system (ILS) or the VHF omni directional radio range (VOR). Nevertheless, the quantitative analysis of corresponding, potentially harmful multipath propagation disturbances is very difficult due to the large parameter space. Experimentally difficulties arise due to very expensive, real scale measurement campaigns and numerical simulation techniques still have shortcomings which are briefly discussed. In this contribution a new universal approach is introduced on how to measure very flexibly multipath propagation effects for arbitrary navigation systems using a channel sounder architecture in a scaled measurement environment. Two relevant scenarios of multipath propagation and the impact on navigation signals are presented. The first describes disturbances of the ILS due to large taxiing aircraft. The other example shows the influence of rotating wind turbines on the VOR.

  13. Effects of digital altimetry on pilot workload

    NASA Technical Reports Server (NTRS)

    Harris, R. L., Sr.; Glover, B. J.

    1985-01-01

    A series of VOR-DME instrument landing approaches was flown in the DC-9 full-workload simulator to compare pilot performance, scan behavior, and workload when using a computer-drum-pointer altimeter (CDPA) and a digital altimeter (DA). Six pilots executed two sets of instrument landing approaches, with a CDPA on one set and a DA on the other set. Pilot scanning parameters, flight performance, and subjective opinion data were evaluated. It is found that the processes of gathering information from the CDPA and the DA are different. The DA requires a higher mental workload than the CDPA for a VOR-DME type landing approach. Mental processing of altitude information after transitioning back to the attitude indicator is more evident with the DA than with the CDPA.

  14. Victim-Offender Relationship Status Moderates the Relationships of Peritraumatic Emotional Responses, Active Resistance, and Posttraumatic Stress Symptomatology in Female Rape Survivors

    PubMed Central

    Feinstein, Brian A.; Humphreys, Kathryn L.; Bovin, Michelle J.; Marx, Brian P.; Resick, Patricia A.

    2010-01-01

    This study examined whether the level of victim-offender relationship (VOR) moderated the relationship between peritraumatic fear and active resistance as well as the relationship between peritraumatic fear and posttraumatic stress symptom severity in a community sample of female rape survivors. One hundred thirty-five participants were interviewed about their emotional and behavioral responses during the rape and assessed for posttraumatic stress symptomatology within one month of the assault. Results indicated that peritraumatic fear was positively associated with active resistance, but only among survivors of acquaintance rape. Additionally, peritraumatic fear was positively associated with posttraumatic stress symptom severity, but only among survivors of intimate partner rape. These results suggest that VOR may be an important contextual factor that influences emotional and behavioral responses during rape as well as posttraumatic stress symptomatology in its aftermath. PMID:21731797

  15. Lack of effects of astemizole on vestibular ocular reflex, motion sickness, and cognitive performance in man

    NASA Technical Reports Server (NTRS)

    Kohl, Randall L.; Homick, Jerry L.; Cintron, Nitza; Calkins, Dick S.

    1987-01-01

    Astemizole was orally administered to 20 subjects in a randomized, double-blind design to assess the efficacy of this peripherally active antihistamine as an antimotion sickness drug possessing no central side-effects. Measures of vestibular ocular reflex (VOR) were made to evaluate the agent as a selective vestibular depressant. Following one week of orally administered astemizole (30 mg daily), a Staircase Profile Test, a VOR test, and a variety of tests of cognitive performance were administered. These tests revealed no statistically significant effects of astemizole. This leads to the conclusion that, although the drug probably reaches the peripheral vestibular apparatus in man by crossing the blood-vestibular barrier, a selective peripheral antihistamine (H1) action is inadequate to control motion sickness induced through cross-coupled accelerative semicircular canal stimulation in a rotating chair.

  16. Loran-C flight data base

    NASA Technical Reports Server (NTRS)

    Lilley, R. W.

    1979-01-01

    Loran-C time-difference data were collected on January 9, 1979 during a flight from Athens, Ohio to Madison VOR in Connecticut, thence to Millville VOR in New Jersey, and a landing at Atlantic City NAFEC. Portions of the return trip to Athens, Ohio were also recorded. Loran-C GRI data frames were recorded using the 99600 U. S. Northeast Loran chain stations Seneca/Nantucket (TDA) and Seneca/Carolina Beach (TDB). The GRI sequence number TDA and TDB were recorded as integer numbers, with the TD's in integer microseconds. Actual time-of-day can be determined from the data start time, plus the time per GRI and the sequence number. The low cost Loran-C receiver was used to obtain the time-difference data for each GRI. Data was recorded on digital magnetic tape and post-processed into latitude and longitude using an IBM system/370 computer.

  17. Adaptation of primate vestibuloocular reflex to altered peripheral vestibular inputs. II Spatiotemporal properties of the adapted slow-phase eye velocity

    NASA Technical Reports Server (NTRS)

    Angelaki, D. E.; Hess, B. J.

    1996-01-01

    1. The ability of the vestibuloocular reflex (VOR) to undergo adaptive modification after selective changes in the peripheral vestibular system was investigated in rhesus monkeys by recording three-dimensional eye movements before and after inactivation of selective semicircular canals. In the preceding paper we showed that the horizontal VOR gain evoked by passive yaw oscillations after lateral semicircular canal inactivation recovers gradually over time in a frequency-specific manner. Here we present the spatial tuning of the adapted slow-phase eye velocity and describe its spatiotemporal properties as a function of time after canal inactivation. 2. The spatial organization of the VOR was investigated during oscillations at different head positions in the pitch, roll, and yaw planes, as well as in the right anterior/left posterior and left anterior/right posterior canal planes. Acutely after bilateral inactivation of the lateral semicircular canals, a small horizontal response could still be elicited that peaked during rotations in pitched head positions that would maximally stimulate vertical semicircular canals. In addition, the phase of horizontal slow-phase velocity abruptly reversed through 180 degrees at positions close to upright, similarly to torsional slow-phase velocity. These spatial response properties suggest that the small, residual horizontal response components that are present acutely after plugging of both lateral canals originate from vertical semicircular canal signals. 3. As the horizontal response amplitude increased over time, consistent changes were also observed in the spatiotemporal tuning of horizontal slow-phase velocity. 1) The spatiotemporal response properties of horizontal slow-phase velocity acquired noncosine tuning characteristics, primarily in the pitch plane, in the right anterior/left posterior and left anterior/right posterior canal planes. Accordingly, horizontal response amplitude was nonzero during rotation in any head

  18. Multiple subclasses of Purkinje cells in the primate floccular complex provide similar signals to guide learning in the vestibulo-ocular reflex

    NASA Technical Reports Server (NTRS)

    Raymond, J. L.; Lisberger, S. G.

    1997-01-01

    The neural "learning rules" governing the induction of plasticity in the cerebellum were analyzed by recording the patterns of neural activity in awake, behaving animals during stimuli that induce a form of cerebellum-dependent learning. We recorded the simple- and complex-spike responses of a broad sample of Purkinje cells in the floccular complex during a number of stimulus conditions that induce motor learning in the vestibulo-ocular reflex (VOR). Each subclass of Purkinje cells carried essentially the same information about required changes in the gain of the VOR. The correlation of simple-spike activity in Purkinje cells with activity in vestibular pathways could guide learning during low-frequency but not high-frequency stimuli. Climbing fiber activity could guide learning during all stimuli tested but only if compared with the activity present approximately 100 msec earlier in either vestibular pathways or Purkinje cells.

  19. Development of the Roll-Induced Vestibuloocular Reflex in the Absence of Vestibular Experience in Salamander Tadpoles (Pleurodeles Waltl)

    NASA Astrophysics Data System (ADS)

    Horn, Eberhard R.; Gabriel, Martin; Frippiat, Jean-Pol

    2008-06-01

    The macula organ of the labyrinth is stimulated by body roll or translatory movements. Due to its slow development, the salamander Pleurodeles waltl is an excellent model to study the impact of microgravity on the development of the roll-induced vestibuloocular reflex (rVOR) in the absence of any macular stimulation. The experiment was performed during the Soyuz mission TMA8 (return flight TMA7) in 2006 as part of the experiment AMPHIBODY. It was supplemented by a 3g-hypergravity experiment. It was shown, that microgravity retards the over-all development of Pleurodeles tadpoles but not specifically functional development of the vestibular system; normalization took place within 3 to 4 weeks after landing. Hypergravity accelerated rVOR development in the long-term frame.

  20. Einführung in die Renaturierungsökologie

    NASA Astrophysics Data System (ADS)

    Zerbe, Stefan; Wiegleb, Gerhard; Rosenthal, Gert

    Durch die übernutzung der Naturressourcen sind heute weltweit viele natürliche wie auch durch Kultur entstandene ökosysteme und Landschaften in ihren Funktionen und Leistungen stark beeinträchtigt oder sogar völlig zerstört. Bereits vor mehr als einem Jahrzehnt konstatierte (1995), dass ca. 45 % der terrestrischen Landoberfläche nur eine reduzierte Kapazität für die zukünftige Landnutzung haben. Als Grund hob er eine in der Vergangenheit nicht nachhaltige Landbewirtschaftung hervor. Mit einer gezielten Renaturierung der betroffenen ökosysteme soll dieser Trend umgekehrt werden (Harris und van Diggelen 2006). Vor diesem Hintergrund ist die ökosystemrenaturierung (ecological restoration) wichtiger Bestandteil der Planungs- und Naturschutzpraxis in Mitteleuropa und die Renaturierungsökologie (restoration ecology) zu einer eigenen wissenschaftlichen Arbeitsrichtung geworden.

  1. Regenerative Energieträger im Aufwind: Entwicklung der erneuerbaren Energien

    NASA Astrophysics Data System (ADS)

    Kohl, Harald

    2006-05-01

    2005 kam 4,6 % des deutschen Primär-Energieverbrauchs aus erneuerbaren Energiequellen, bei der Stromproduktion lag ihr Anteil bei 10,2 %. Wesentliche Ursache ist der Boom bei der Windkraft, die vor allem durch Offshore-Windparks auf See weiter ausbaubar ist. Die Wasserkraft lieferte in Deutschland traditionell einen großen Beitrag zur Stromerzeugung, doch ihr Ausbaupotenzial ist gering. Die Photovoltaik, die solar- und die geothermische Stromerzeugung spielen derzeit noch eine kleine Rolle. Den deutschen Bedarf an Wärmeenergie deckten 2004 die erneuerbaren Energien zu 5,4 %, vor allem aus Biomasse. Die solarthermische Wärmeerzeugung hat sich gegenüber 2000 mehr als verdoppelt. Im Straßenverkehr spielen biogene Kraftstoffe mit 5,4 % noch eine untergeordnete Rolle. Bis 2050 könnte in Deutschland der Anteil regenerativer Energien am Primär-Energieverbrauch die Fünfzigprozentmarke überschreiten.

  2. Motor function in microgravity: movement in weightlessness

    NASA Technical Reports Server (NTRS)

    Lackner, J. R.; DiZio, P.

    1996-01-01

    Microgravity provides unique, though experimentally challenging, opportunities to study motor control. A traditional research focus has been the effects of linear acceleration on vestibular responses to angular acceleration. Evidence is accumulating that the high-frequency vestibulo-ocular reflex (VOR) is not affected by transitions from a 1 g linear force field to microgravity (<1 g); however, it appears that the three-dimensional organization of the VOR is dependent on gravitoinertial force levels. Some of the observed effects of microgravity on head and arm movement control appear to depend on the previously undetected inputs of cervical and brachial proprioception, which change almost immediately in response to alterations in background force levels. Recent studies of post-flight disturbances of posture and locomotion are revealing sensorimotor mechanisms that adjust over periods ranging from hours to weeks.

  3. Atomic Basic Blocks

    NASA Astrophysics Data System (ADS)

    Scheler, Fabian; Mitzlaff, Martin; Schröder-Preikschat, Wolfgang

    Die Entscheidung, einen zeit- bzw. ereignisgesteuerten Ansatz für ein Echtzeitsystem zu verwenden, ist schwierig und sehr weitreichend. Weitreichend vor allem deshalb, weil diese beiden Ansätze mit äußerst unterschiedlichen Kontrollflussabstraktionen verknüpft sind, die eine spätere Migration zum anderen Paradigma sehr schwer oder gar unmöglich machen. Wir schlagen daher die Verwendung einer Zwischendarstellung vor, die unabhängig von der jeweils verwendeten Kontrollflussabstraktion ist. Für diesen Zweck verwenden wir auf Basisblöcken basierende Atomic Basic Blocks (ABB) und bauen darauf ein Werkzeug, den Real-Time Systems Compiler (RTSC) auf, der die Migration zwischen zeit- und ereignisgesteuerten Systemen unterstützt.

  4. Design of a Miniaturized Meandered Line Antenna for UHF RFID Tags

    PubMed Central

    Islam, Mohammad Tariqul; Rowe, Wayne S. T.; Kibria, Salehin; Jit Singh, Mandeep; Misran, Norbahiah

    2016-01-01

    A semi-circle looped vertically omnidirectional radiation (VOR) patterned tag antenna for UHF (919–923 MHz for Malaysia) frequency is designed to overcome the impedance mismatch issue in this paper. Two impedance matching feeding strips are used in the antenna structure to tune the input impedance of the antenna. Two dipole shaped meandered lines are used to achieve a VOR pattern. The proposed antenna is designed for 23-j224 Ω chip impedance. The antenna is suitable for ‘place and tag’ application. A small size of 77.68×35.5 mm2 is achieved for a read range performance of 8.3 meters using Malaysia regulated maximum power transfer of 2.0 W effective radiated power (ERP). PMID:27533470

  5. Anatomical and Physiological Considerations in Vestibular Dysfunction and Compensation

    PubMed Central

    Jones, Sherri M.; Jones, Timothy A.; Mills, Kristal N.; Gaines, G. Christopher

    2010-01-01

    Sensory information from the vestibular, visual, and somatosensory/proprioceptive systems are integrated in the brain in complex ways to produce a final motor output to muscle groups for maintaining gaze, head and body posture, and controlling static and dynamic balance. The balance system is complex, which can make differential diagnosis of dizziness quite challenging. On the other hand, this complex system is organized anatomically in a variety of pathways and some of these pathways have been well studied. The vestibulo-ocular reflex (VOR) is one such pathway. Understanding the anatomy and physiology of the VOR facilitates our understanding of normal and abnormal eye movements and research is advancing our understanding of the plasticity of the vestibular system. This review highlights anatomical and physiological features of the normal vestibular system, applies these concepts to explain some clinical findings in some common peripheral vestibular disorders, and discusses some of the research investigating the anatomical and physiological basis for vestibular compensation. PMID:21072129

  6. Design of a Miniaturized Meandered Line Antenna for UHF RFID Tags.

    PubMed

    Rokunuzzaman, Md; Islam, Mohammad Tariqul; Rowe, Wayne S T; Kibria, Salehin; Jit Singh, Mandeep; Misran, Norbahiah

    2016-01-01

    A semi-circle looped vertically omnidirectional radiation (VOR) patterned tag antenna for UHF (919-923 MHz for Malaysia) frequency is designed to overcome the impedance mismatch issue in this paper. Two impedance matching feeding strips are used in the antenna structure to tune the input impedance of the antenna. Two dipole shaped meandered lines are used to achieve a VOR pattern. The proposed antenna is designed for 23-j224 Ω chip impedance. The antenna is suitable for 'place and tag' application. A small size of 77.68×35.5 mm2 is achieved for a read range performance of 8.3 meters using Malaysia regulated maximum power transfer of 2.0 W effective radiated power (ERP). PMID:27533470

  7. The expenditures related to the use of antifungal drugs in patients with hematological cancers: a cost analysis

    PubMed Central

    Gedik, Habip

    2015-01-01

    Objective The aim of this study is to analyze the expenditures related to the use of antifungal drugs in patients with hematological malignancies. Methods In this retrospective study, the expenditures related to use of antifungal drugs for treatment of invasive fungal infections in patients with hematological malignancies between November 2010 and November 2012 were analyzed. Expenditures of antifungal drugs were calculated by converting the price billed to the Republic of Turkey Social Security Institution per patient using the US dollar ($) exchange rate. Results We retrospectively analyzed the expenditures related to the use of antifungal drugs in 282 febrile episodes of 126 neutropenic patients. Voriconazole (VOR), caspofungin, and liposomal amphotericin B (L-AmB) were administered as a first-line antifungal therapy to treat 72 febrile episodes of 65 neutropenic patients, 45 febrile episodes of 37 neutropenic patients, and 34 febrile episodes of 32 neutropenic patients, respectively. The expenditures related to the use of antifungal drugs per febrile neutropenic episode were $3,857.85 for VOR; $15,783.34 for caspofungin, and $21,561.02 for L-AmB, respectively. The expenditure related to the use of posaconazole (POS) was $32,167.39 per patient for primary or secondary prophylaxis. Conclusion Improving conditions in the patient’s room, choosing pre-emptive antifungal treatment instead of empirical antifungal treatment, switching to tablet form of VOR after initiation of its intravenous form, secondary prophylaxis with VOR against invasive aspergillosis, primary prophylaxis with POS in high-risk patients, and choosing less L-AmB as being an alternative to other antifungal drugs, may reduce expenditures related to the use of antifungal drugs in the treatment of invasive fungal infections during febrile neutropenic episodes of patients with hematological malignancies. PMID:26622185

  8. Modeling gravity-dependent plasticity of the angular vestibuloocular reflex with a physiologically based neural network.

    PubMed

    Xiang, Yongqing; Yakushin, Sergei B; Cohen, Bernard; Raphan, Theodore

    2006-12-01

    A neural network model was developed to explain the gravity-dependent properties of gain adaptation of the angular vestibuloocular reflex (aVOR). Gain changes are maximal at the head orientation where the gain is adapted and decrease as the head is tilted away from that position and can be described by the sum of gravity-independent and gravity-dependent components. The adaptation process was modeled by modifying the weights and bias values of a three-dimensional physiologically based neural network of canal-otolith-convergent neurons that drive the aVOR. Model parameters were trained using experimental vertical aVOR gain values. The learning rule aimed to reduce the error between eye velocities obtained from experimental gain values and model output in the position of adaptation. Although the model was trained only at specific head positions, the model predicted the experimental data at all head positions in three dimensions. Altering the relative learning rates of the weights and bias improved the model-data fits. Model predictions in three dimensions compared favorably with those of a double-sinusoid function, which is a fit that minimized the mean square error at every head position and served as the standard by which we compared the model predictions. The model supports the hypothesis that gravity-dependent adaptation of the aVOR is realized in three dimensions by a direct otolith input to canal-otolith neurons, whose canal sensitivities are adapted by the visual-vestibular mismatch. The adaptation is tuned by how the weights from otolith input to the canal-otolith-convergent neurons are adapted for a given head orientation.

  9. Readaptation of the vestibulo-ocular reflex relieves the mal de debarquement syndrome.

    PubMed

    Dai, Mingjia; Cohen, Bernard; Smouha, Eric; Cho, Catherine

    2014-01-01

    The mal de debarquement syndrome (MdDS), a continuous feeling of swaying, rocking, and/or bobbing, generally follows travel on the sea. The associated symptoms cause considerable distress. The underlying neural mechanisms are unknown, and to date there have been no effective treatments for this condition. Results in monkeys and humans suggested that MdDS was caused by maladaptation of the vestibulo-ocular reflex (VOR) to roll of the head during rotation. We studied 24 subjects with persistent MdDS (3 males, 21 females; 19.1 ± 33 months). Physical findings included body oscillation at 0.2 Hz, oscillating vertical nystagmus when the head was rolled from side-to-side in darkness, and unilateral rotation during the Fukuda stepping test. We posited that the maladapted rocking and the physical symptoms could be diminished or extinguished by readapting the VOR. Subjects were treated by rolling the head from side-to-side while watching a rotating full-field visual stimulus. Seventeen of the 24 subjects had a complete or substantial recovery on average for approximately 1 year. Six were initially better, but the symptoms recurred. One subject did not respond to treatment. Thus, readaptation of the VOR has led to a cure or substantial improvement in 70% of the subjects with MdDS. We conclude that the adaptive processes associated with roll-while-rotating are responsible for producing MdDS, and that the symptoms can be reduced or resolved by readapting the VOR.

  10. Chronic symptoms after vestibular neuritis and the high velocity vestibulo-ocular reflex

    PubMed Central

    Patel, Mitesh; Arshad, Qadeer; Roberts, R Edward; Ahmad, Hena; Bronstein, Adolfo M.

    2015-01-01

    Hypothesis As the anterior and posterior semicircular canals are vital to the regulation of gaze stability, particularly during locomotion or vehicular travel, we tested whether the high velocity vestibulo-ocular reflex (VOR) of the three ipsilesional semicircular canals elicited by the modified Head Impulse Test would correlate with subjective dizziness or vertigo scores after vestibular neuritis (VN). Background Recovery following acute VN varies with around half reporting persistent symptoms long after the acute episode. However, an unanswered question is whether chronic symptoms are associated with impairment of the high velocity VOR of the anterior or posterior canals. Methods Twenty patients who had experienced an acute episode of VN at least three months earlier were included in this study. Participants were assessed with the video head impulse test (vHIT) of all six canals, bithermal caloric irrigation, the Dizziness Handicap Inventory (DHI) and the Vertigo Symptoms Scale short-form (VSS). Results Of these 20 patients, 12 felt that they had recovered from the initial episode whereas 8 did not and reported elevated DHI and VSS scores. However, we found no correlation between DHI or VSS scores and the ipsilesional single or combined vHIT gain, vHIT gain asymmetry or caloric paresis. The high velocity VOR was not different between patients who felt they had recovered and patients who felt they had not. Conclusions Our findings suggest that chronic symptoms of dizziness following VN are not associated with the high velocity VOR of the single or combined ipsilesional horizontal, anterior or posterior semicircular canals. PMID:26719963

  11. 76 FR 72613 - Standard Instrument Approach Procedures, and Takeoff Minimums and Obstacle Departure Procedures...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-11-25

    ... Policies and Procedures (44 FR 11034; February 26, 1979); and (3) does not warrant preparation of a... Lincoln 1/8699 10/31/11 VOR/DME RWY 22, Capital. Orig-A 15-Dec-11......... NC Jacksonville..... Albert J Ellis... 1/8737 10/24/11 NDB RWY 5, Amdt 8 15-Dec-11......... GA Athens Athens/Ben Epps.. 1/8738...

  12. 77 FR 14269 - IFR Altitudes; Miscellaneous Amendments

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-03-09

    ... BILLINGS, MT VORTAC..... W BND 9700 E BND 6400 Sec. 95.681 VOR Federal Airway V81 Is Amended to Read in... Amended to Read in Part REEPO, MT FIX COLUS, MT FIX W BND 9700 ] E BND 7000 COLUS, MT FIX BILLINGS, MT... *BILLINGS, MT VORTAC.... S BND 17000 N BND 6000 *7000--MCA BILLINGS, MT VORTAC, S BND Sec. 95.6320......

  13. 78 FR 59810 - Standard Instrument Approach Procedures, and Takeoff Minimums and Obstacle Departure Procedures...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-09-30

    ... Policies and Procedures (44 FR 11034; February 26, 1979); and (3) does not warrant preparation of a... CAT I), Amdt 7 10/17/13 AK Savoonga Savoonga 3/3472 8/29/13 VOR/DME RWY 23, Amdt 1A 10/17/13 AK... City Intl. 3/4342 8/29/13 ILS OR LOC RWY 16R, ILS RWY 16R (SA CAT I), ILS RWY 16R (CAT II & III),...

  14. 78 FR 40385 - Standard Instrument Approach Procedures, and Takeoff Minimums and Obstacle Departure Procedures...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-07-05

    ... regulatory Policies and Procedures (44 FR 11034; February 26, 1979); and (3) does not warrant preparation of... RNAV (GPS) RWY Intl. 34, Amdt 2A. 7/25/13 AR Lake Village.... Lake Village 3/0451 6/13/13 VOR-A, Amdt 8. Muni. 7/25/13 AR Lake Village.... Lake Village 3/0452 6/13/13 RNAV (GPS) RWY Muni. 1, Orig. 7/25/13...

  15. Was wissen wir über Information?

    NASA Astrophysics Data System (ADS)

    Engelmann, Florian; Großmann, Christoph

    Der Begriff Information stammt aus dem Lateinischen. Von der Antike bis in das 20. Jahrhundert war Information ein kaum verwendetes und unspektakuläres Wort. ZEMANEK belegt diese Hypothese mit dem Verweis auf ein Häufigkeitswörterbuch der deutschen Sprache aus dem Jahre 1897. Dort kommt in ca. 11 Millionen Wörten nur 55 mal das Wort Information vor [Zemanek 1986, S. 19].

  16. Alternative Nachweisverfahren - nicht PCR-basierende Schnellmethoden

    NASA Astrophysics Data System (ADS)

    Schalch, Barbara; Wagner, Martin

    Die Erfolge moderner mikrobiologischer Schnellmethoden stellen Sensitivität und Spezifität vieler konventioneller mikrobiologischer Kultivierungsmethoden in Frage. Konventionell ermittelte Keimzahlen und -gruppen pro Untersuchungseinheit scheinen mehr oder weniger unter den realen Gegebenheiten zu liegen. Andererseits schreibt beispielsweise die EU-weit geltende Verordnung (EG) Nr. 2073/2005 über mikrobiologische Kriterien für Lebensmittel den Einsatz einiger dieser Nachweismethoden verbindlich vor.

  17. Führungs- und Teamverhalten

    NASA Astrophysics Data System (ADS)

    Ebermann, Hans-Joachim; Scheiderer, Joachim

    Mc. Broom war ein tyrannischer Chef, der seine Mitarbeiter mit seiner Launenhaftigkeit einschüchterte. Das wäre vielleicht nicht aufgefallen, hätte Mc. Broom in einem Büro oder in einer Fabrik gearbeitet. Aber Mc. Broom war Flugkapitän. <¼> Seine Copiloten fürchteten sich so sehr vor seinem Zorn, dass sie nichts sagten. Nicht einmal als die Katastrophe absehbar war. Beim Absturz der Maschine kamen zehn Menschen zu Tode (Goleman 2001).

  18. Ausbildung als zentrale Aufgabe

    NASA Astrophysics Data System (ADS)

    Krämer, Walter; Schmerbach, Sibylle

    Anders als Lesen und Schreiben zählen Grundkenntnisse in Statistik heute noch nicht zu den Voraussetzungen einer sinnvollen Teilhabe am Sozialgeschehen. Und auch in der akademischen Statistik-Ausbildung gibt es noch einiges zu tun. Das vorliegende Kapitel zeichnet die Geschichte dieser akademischen Ausbildung an deutschen Universitäten nach dem zweiten Weltkrieg nach, stellt aktuelle Defizite vor und weist auf mögliche Verbesserungen hin.

  19. Optimierung von Kommunikationsnetzen

    NASA Astrophysics Data System (ADS)

    Eberspächer, Jörg; Kiese, Moritz; Wessäly, Roland

    Die weltweiten Telekommunikationsnetze (Telefon-, Mobilfunknetze, Internet) bilden heute das Nervensystem von Wirtschaft und Gesellschaft. Durch den anhaltenden technologischen Fortschritt in der Elektronik, der Computer- und Kommunikationstechnik steigt nicht nur die Zahl der Teilnehmer in den Netzen ständig, sondern es entstehen auch laufend neue Anwendungen, wie Radio und Fernsehen im Internet, elektronischer Handel und interaktive Spiele im Internet. Auf den Kupfer- und Glasfaserkabeln sowie den Funkstrecken werden gigantische Informationsmengen transportiert. Das Verkehrs-wachstum ist nach wie vor exponentiell.

  20. Effects of vestibular rotatory accelerations on covert attentional orienting in vision and touch.

    PubMed

    Figliozzi, Francesca; Guariglia, Paola; Silvetti, Massimo; Siegler, Isabelle; Doricchi, Fabrizio

    2005-10-01

    Peripheral vestibular organs feed the central nervous system with inputs favoring the correct perception of space during head and body motion. Applying temporal order judgments (TOJs) to pairs of simultaneous or asynchronous stimuli presented in the left and right egocentric space, we evaluated the influence of leftward and rightward vestibular rotatory accelerations given around the vertical head-body axis on covert attentional orienting. In a first experiment, we presented visual stimuli in the left and right hemifield. In a second experiment, tactile stimuli were presented to hands lying on their anatomical side or in a crossed position across the sagittal body midline. In both experiments, stimuli were presented while normal subjects suppressed or did not suppress the vestibulo-ocular response (VOR) evoked by head-body rotation. Independently of VOR suppression, visual and tactile stimuli presented on the side of rotation were judged to precede simultaneous stimuli presented on the side opposite the rotation. When limbs were crossed, attentional facilitatory effects were only observed for stimuli presented to the right hand lying in the left hemispace during leftward rotatory trials with VOR suppression. This result points to spatiotopic rather than somatotopic influences of vestibular inputs, suggesting that cross-modal effects of these inputs on tactile ones operate on a representation of space that is updated following arm crossing. In a third control experiment, we demonstrated that temporal prioritization of stimuli presented on the side of rotation was not determined by response bias linked to spatial compatibility between the directions of rotation and the directional labels used in TOJs (i.e., "left" or "right" first). These findings suggest that during passive rotatory head-body accelerations, covert attention is shifted toward the direction of rotation and the direction of the fast phases of the VOR.

  1. Physiology of Developing Gravity Receptors and Otolith-Ocular Reflexes in Rat

    NASA Technical Reports Server (NTRS)

    Blanks, Robert H.

    1997-01-01

    This proposal had the long-term objective of examining the effects of microgravity on the physiology of the adult and developing mammalian gravity receptors. The grant outlined three-years of ground-based studies to examine. 1) the physiologic responses or otolith afferents in the adult rat and during postnatal development, and 2) the otolith organ contributions to the vertical vestibulo-ocular (VOR) and postural reflexes.

  2. Readaptation of the Vestibulo-Ocular Reflex Relieves the Mal De Debarquement Syndrome

    PubMed Central

    Dai, Mingjia; Cohen, Bernard; Smouha, Eric; Cho, Catherine

    2014-01-01

    The mal de debarquement syndrome (MdDS), a continuous feeling of swaying, rocking, and/or bobbing, generally follows travel on the sea. The associated symptoms cause considerable distress. The underlying neural mechanisms are unknown, and to date there have been no effective treatments for this condition. Results in monkeys and humans suggested that MdDS was caused by maladaptation of the vestibulo-ocular reflex (VOR) to roll of the head during rotation. We studied 24 subjects with persistent MdDS (3 males, 21 females; 19.1 ± 33 months). Physical findings included body oscillation at 0.2 Hz, oscillating vertical nystagmus when the head was rolled from side-to-side in darkness, and unilateral rotation during the Fukuda stepping test. We posited that the maladapted rocking and the physical symptoms could be diminished or extinguished by readapting the VOR. Subjects were treated by rolling the head from side-to-side while watching a rotating full-field visual stimulus. Seventeen of the 24 subjects had a complete or substantial recovery on average for approximately 1 year. Six were initially better, but the symptoms recurred. One subject did not respond to treatment. Thus, readaptation of the VOR has led to a cure or substantial improvement in 70% of the subjects with MdDS. We conclude that the adaptive processes associated with roll-while-rotating are responsible for producing MdDS, and that the symptoms can be reduced or resolved by readapting the VOR. PMID:25076935

  3. 14 CFR 93.350 - Definitions.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... drawn direct to the southwestern tip of Governors Island, thence north along a line direct to the southwest tip of Manhattan Island, thence north along the west bank of the East River to the LGA VOR/DME 6... along the east bank of the East River to the point of beginning at lat. 40°38′39″ N., long 74°02′03″...

  4. Johannes Kepler

    NASA Astrophysics Data System (ADS)

    Bialas, Volker

    Johannes Kepler (1571 - 1630) gilt zurecht als einer der bedeutendsten Mathematiker und Astronomen der frühen Neuzeit, doch wurde das Philosophische in seinem Werk bislang kaum in angemessener Weise gewürdigt. Volker Bialas legt eine fundierte und anregende Einführung in Leben, Werk und Weltanschauung Keplers vor und setzt dabei durch die Akzentuierung des philosophisch-ganzheitlichen Denkens bewußt einen Kontrapunkt zum herkömmlichen Kepler-Bild.

  5. 75 FR 76626 - Standard Instrument Approach Procedures, and Takeoff Minimums and Obstacle Departure Procedures...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-12-09

    ..., RNAV (GPS) RWY 36, Orig Childress, TX, Childress Muni, VOR RWY 36, Amdt 10A Salt Lake City, UT, Salt Lake City Intl, ILS OR LOC RWY 16L, ILS RWY 16L (CAT II), ILS RWY 16L (CAT III), Amdt 3 Salt Lake City, UT, Salt Lake City Intl, ILS OR LOC RWY 16R, ILS RWY 16R (CAT II), ILS RWY 16R (CAT III), Amdt 3...

  6. Modeling the vestibulo-ocular reflex of the squirrel monkey during eccentric rotation and roll tilt

    NASA Technical Reports Server (NTRS)

    Merfeld, D. M.; Paloski, W. H. (Principal Investigator)

    1995-01-01

    Model simulations of the squirrel monkey vestibulo-ocular reflex (VOR) are presented for two motion paradigms: constant velocity eccentric rotation and roll tilt about a naso-occipital axis. The model represents the implementation of three hypotheses: the "internal model" hypothesis, the "gravito-inertial force (GIF) resolution" hypothesis, and the "compensatory VOR" hypothesis. The internal model hypothesis is based on the idea that the nervous system knows the dynamics of the sensory systems and implements this knowledge as an internal dynamic model. The GIF resolution hypothesis is based on the idea that the nervous system knows that gravity minus linear acceleration equals GIF and implements this knowledge by resolving the otolith measurement of GIF into central estimates of gravity and linear acceleration, such that the central estimate of gravity minus the central estimate of acceleration equals the otolith measurement of GIF. The compensatory VOR hypothesis is based on the idea that the VOR compensates for the central estimates of angular velocity and linear velocity, which sum in a near-linear manner. During constant velocity eccentric rotation, the model correctly predicts that: (1) the peak horizontal response is greater while "facing-motion" than with "back-to-motion"; (2) the axis of eye rotation shifts toward alignment with GIF; and (3) a continuous vertical response, slow phase downward, exists prior to deceleration. The model also correctly predicts that a torsional response during the roll rotation is the only velocity response observed during roll rotations about a naso-occipital axis. The success of this model in predicting the observed experimental responses suggests that the model captures the essence of the complex sensory interactions engendered by eccentric rotation and roll tilt.

  7. Ist da jemand? Wie Außerirdische uns entdecken können

    NASA Astrophysics Data System (ADS)

    Heller, R.

    2016-06-01

    Astronomen schlagen vor, sich bei der Suche nach Signalen außerirdischer Zivilisationen auf einen schmalen Bereich am Himmel zu konzentrieren. Von Planeten um Sterne, die in diesem Streifen liegen, würde sich die Erde vergleichsweise leicht entdecken lassen. Sollte es dort intelligentes Leben geben, könnte uns dieses schon längst aufgespürt und eine Botschaft Richtung Erde geschickt haben.

  8. 75 FR 8243 - Standard Instrument Approach Procedures, and Takeoff Minimums and Obstacle Departure Procedures...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-02-24

    ... Policies and Procedures (44 FR 11034; February 26, 1979); and (3) does not warrant preparation of a... date Subject 11-Mar-10 IL FLORA FLORA MUNI 0/1005 1/22/10 RNAV (GPS) RWY 3, AMDT 1. 11-Mar-10 IN... MUNI......... 0/2083 1/22/10 VOR RWY 4, AMDT 13. 11-Mar-10 IL FLORA FLORA MUNI 0/2119 1/22/10...

  9. 78 FR 18803 - Standard Instrument Approach Procedures, and Takeoff Minimums and Obstacle Departure Procedures...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-03-28

    ... Policies and Procedures (44 FR 11034; February 26, 1979); and (3) does not warrant preparation of a... OR LOC/DME RWY 7, Amdt 5D. Saipan Intl. 2-May-13 CA Daggett Barstow-Daggett...... 3/0199 3/6/2013 VOR OR TACAN RWY 22, Amdt 10. 2-May-13 CA Daggett Barstow-Daggett...... 3/0200 3/6/2013 RNAV (GPS) RWY...

  10. Modeling the vestibulo-ocular reflex of the squirrel monkey during eccentric rotation and roll tilt.

    PubMed

    Merfeld, D M

    1995-01-01

    Model simulations of the squirrel monkey vestibulo-ocular reflex (VOR) are presented for two motion paradigms: constant velocity eccentric rotation and roll tilt about a naso-occipital axis. The model represents the implementation of three hypotheses: the "internal model" hypothesis, the "gravito-inertial force (GIF) resolution" hypothesis, and the "compensatory VOR" hypothesis. The internal model hypothesis is based on the idea that the nervous system knows the dynamics of the sensory systems and implements this knowledge as an internal dynamic model. The GIF resolution hypothesis is based on the idea that the nervous system knows that gravity minus linear acceleration equals GIF and implements this knowledge by resolving the otolith measurement of GIF into central estimates of gravity and linear acceleration, such that the central estimate of gravity minus the central estimate of acceleration equals the otolith measurement of GIF. The compensatory VOR hypothesis is based on the idea that the VOR compensates for the central estimates of angular velocity and linear velocity, which sum in a near-linear manner. During constant velocity eccentric rotation, the model correctly predicts that: (1) the peak horizontal response is greater while "facing-motion" than with "back-to-motion"; (2) the axis of eye rotation shifts toward alignment with GIF; and (3) a continuous vertical response, slow phase downward, exists prior to deceleration. The model also correctly predicts that a torsional response during the roll rotation is the only velocity response observed during roll rotations about a naso-occipital axis. The success of this model in predicting the observed experimental responses suggests that the model captures the essence of the complex sensory interactions engendered by eccentric rotation and roll tilt. PMID:8542968

  11. Ein Framework für echtzeitfähige Ethernet-Netzwerke

    NASA Astrophysics Data System (ADS)

    Dopatka, Frank

    Im Rahmen dieser Arbeit wird die Entwicklung eines formalen Framewoks vorgestellt, mit dessen Hilfe zwischen der Kompatibilität zum verbreiteten baumförmigen Standard-Ethernet und der Einhaltung von Echtzeitanforderungen einer automatisierten Anlage variiert werden kann. Damit kann bereits vor der Auswahl einer bestimmten Technologie eine Schedule der Echtzeit-Übertragungen offline kalkuliert und simuliert werden, sobald die Anforderungen der Geräte im industriellen Echtzeit-Netzwerk bekannt sind.

  12. In vitro evaluation of Malassezia pachydermatis susceptibility to azole compounds using E-test and CLSI microdilution methods.

    PubMed

    Cafarchia, Claudia; Figueredo, Luciana A; Iatta, Roberta; Colao, Valeriana; Montagna, Maria T; Otranto, Domenico

    2012-11-01

    Dermatitis caused by Malassezia spp., one of most common skin disease in dogs, requires prolonged therapy and/or high doses of antifungal agents. In the present study, the antifungal susceptibility of M. pachydermatis to ketoconazole (KTZ), fluconazole (FLZ), itraconazole (ITZ), posaconazole (POS) and voriconazole (VOR) was evaluated in vitro using both CLSI reference broth microdilution (CLSI BMD) and E-test. A total of 62 M. pachydermatis strains from dogs with and without skin lesions were tested. M. pachydermatis strains were susceptible to ITZ, KTZ and POS using both test methods, with the highest MIC found in tests of FLZ. Essential agreement between the two methods ranged from 87.1% (VOR) to 91.9% (ITZ), and categorical agreement from 74.2% (FLZ) to 96.8% (ITZ). Minor error discrepancies were observed between the two methods, with major discrepancies observed for KTZ. A higher MIC(50) value for FLZ was noted with M. pachydermatis genotype B. The MICs(50) of M. pachydermatis genotype B for KTZ, VOR and POS were higher in isolates from dogs with skin lesions than those in isolates from animals without skin lesions. The results suggest a link between genotypes of M. pachydermatis and in vitro drug susceptibility. The categorical agreement for both E-test and CLSI BMD methods found in this investigation confirms the E-test as a reliable diagnostic method for routine use in clinical mycology laboratories. PMID:22471886

  13. Self-motion perception and vestibulo-ocular reflex during whole body yaw rotation in standing subjects: the role of head position and neck proprioception.

    PubMed

    Panichi, Roberto; Botti, Fabio Massimo; Ferraresi, Aldo; Faralli, Mario; Kyriakareli, Artemis; Schieppati, Marco; Pettorossi, Vito Enrico

    2011-04-01

    Self-motion perception and vestibulo-ocular reflex (VOR) were studied during whole body yaw rotation in the dark at different static head positions. Rotations consisted of four cycles of symmetric sinusoidal and asymmetric oscillations. Self-motion perception was evaluated by measuring the ability of subjects to manually track a static remembered target. VOR was recorded separately and the slow phase eye position (SPEP) was computed. Three different head static yaw deviations (active and passive) relative to the trunk (0°, 45° to right and 45° to left) were examined. Active head deviations had a significant effect during asymmetric oscillation: the movement perception was enhanced when the head was kept turned toward the side of body rotation and decreased in the opposite direction. Conversely, passive head deviations had no effect on movement perception. Further, vibration (100 Hz) of the neck muscles splenius capitis and sternocleidomastoideus remarkably influenced perceived rotation during asymmetric oscillation. On the other hand, SPEP of VOR was modulated by active head deviation, but was not influenced by neck muscle vibration. Through its effects on motion perception and reflex gain, head position improved gaze stability and enhanced self-motion perception in the direction of the head deviation.

  14. Inertial processing of vestibulo-ocular signals

    NASA Technical Reports Server (NTRS)

    Hess, B. J.; Angelaki, D. E.

    1999-01-01

    New evidence for a central resolution of gravito-inertial signals has been recently obtained by analyzing the properties of the vestibulo-ocular reflex (VOR) in response to combined lateral translations and roll tilts of the head. It is found that the VOR generates robust compensatory horizontal eye movements independent of whether or not the interaural translatory acceleration component is canceled out by a gravitational acceleration component due to simultaneous roll-tilt. This response property of the VOR depends on functional semicircular canals, suggesting that the brain uses both otolith and semicircular canal signals to estimate head motion relative to inertial space. Vestibular information about dynamic head attitude relative to gravity is the basis for computing head (and body) angular velocity relative to inertial space. Available evidence suggests that the inertial vestibular system controls both head attitude and velocity with respect to a gravity-centered reference frame. The basic computational principles underlying the inertial processing of otolith and semicircular canal afferent signals are outlined.

  15. Ethanol consumption impairs vestibulo-ocular reflex function measured by the video head impulse test and dynamic visual acuity.

    PubMed

    Roth, Thomas N; Weber, Konrad P; Wettstein, Vincent G; Marks, Guy B; Rosengren, Sally M; Hegemann, Stefan C A

    2014-01-01

    Ethanol affects many parts of the nervous system, from the periphery to higher cognitive functions. Due to the established effects of ethanol on vestibular and oculomotor function, we wished to examine its effect on two new tests of the vestibulo-ocular reflex (VOR): the video head impulse test (vHIT) and dynamic visual acuity (DVA). We tested eight healthy subjects with no history of vestibular disease after consumption of standardized drinks of 40% ethanol. We used a repeated measures design to track vestibular function over multiple rounds of ethanol consumption up to a maximum breath alcohol concentration (BrAC) of 1.38 per mil. All tests were normal at baseline. VOR gain measured by vHIT decreased by 25% at the highest BrAC level tested in each subject. Catch-up saccades were negligible at baseline and increased in number and size with increasing ethanol consumption (from 0.13° to 1.43° cumulative amplitude per trial). DVA scores increased by 86% indicating a deterioration of acuity, while static visual acuity (SVA) remained unchanged. Ethanol consumption systematically impaired the VOR evoked by high-acceleration head impulses and led to a functional loss of visual acuity during head movement.

  16. The bidirectionality of motor learning in the vestibulo-ocular reflex is a function of cerebellar mGluR1 receptors.

    PubMed

    Titley, Heather K; Heskin-Sweezie, Raquel; Broussard, Dianne M

    2010-12-01

    Bidirectional changes in synaptic transmission have the potential to optimize the control of movement. However, it can be difficult to establish a causal relationship between the bidirectionality of synaptic plasticity and bidirectional changes in the speed of actual movements. We asked whether metabotropic glutamate receptor 1 (mGluR1) receptors, which participate in cerebellar long-term depression (LTD), are necessary for bidirectional motor learning in the vestibulo-ocular reflex (VOR). Cerebellar LTD and long-term potentiation (LTP) are thought to cause increases and decreases, respectively, in the gain of the VOR; the direction of learning depends on the behavioral protocol. We injected either the mGluR1 agonist (S)-DHPG or the antagonist YM 298198 bilaterally into the flocculus of alert cats, and then induced motor learning. In the presence of YM 298198, the VOR gain decreased in gain-up, as well as in gain-down protocols. (S)-DHPG augmented gain-up learning. Gain-down learning was not significantly affected by either drug. These results supported the hypothesis that gain-up learning relies on cerebellar LTD, but gain-down learning relies on a different mechanism. In the absence of mGluR1 activity, cerebellar LTD may be replaced with LTP, permitting learning in only one direction.

  17. The human translational vestibulo-ocular reflex in response to complex motion.

    PubMed

    Walker, Mark; Liao, Ke

    2011-09-01

    We studied the translational vestibulo-ocular reflex (tVOR) in four healthy human subjects during complex, unpredictable sum-of-sines head motion (combination of 0.73, 1.33, 1.93, and 2.93 Hz), while subjects viewed a target 15 cm away. Ideal eye velocity was calculated from recorded head motion; actual eye velocity was measured with scleral coils. The gain and phase for each frequency component was determined by least-squares optimization. Gain averaged approximately 40% and did not change with frequency; phase lag increased with frequency to a maximum of 66°. Fitting actual to ideal eye velocity predicted a tVOR latency of 48 m/s for vertical and 38 m/s for horizontal translation. These findings provide further evidence that the normal tVOR is considerably undercompensatory, even at low frequencies if the stimulus is not predictable. The similarity of this behavior to that of pursuit suggests that these two eye movements may share some aspects of neural processing.

  18. An internal model of head kinematics predicts the influence of head orientation on reflexive eye movements

    NASA Astrophysics Data System (ADS)

    Zupan, L. H.; Merfeld, D. M.

    2005-09-01

    Our sense of self-motion and self-orientation results from combining information from different sources. We hypothesize that the central nervous system (CNS) uses internal models of the laws of physics to merge cues provided by different sensory systems. Different models that include internal models have been proposed; we focus herein on that referred to as the sensory weighting model (Zupan et al 2002 Biol. Cybern. 86 209-30). For simplicity, we isolate the portion of the sensory weighting model that estimates head angular velocity: it includes an inverse internal model of head kinematics and an 'idiotropic' vector aligned with the main body axis. Following a post-rotatory tilt in the dark, which is a rapid tilt following a constant-velocity rotation about an earth-vertical axis, the inverse internal model is applied to conflicting vestibular signals. Consequently, the CNS computes an inaccurate estimate of head angular velocity that shifts toward alignment with an estimate of gravity. Since reflexive eye movements known as vestibulo-ocular reflexes (VOR) compensate for this estimate of head angular velocity, the model predicts that the VOR rotation axis shifts toward alignment with this estimate of gravity and that the VOR time constant depends on final head orientation. These predictions are consistent with experimental data.

  19. A combination approach to treating fungal infections

    PubMed Central

    Shrestha, Sanjib K.; Fosso, Marina Y.; Garneau-Tsodikova, Sylvie

    2015-01-01

    Azoles are antifungal drugs used to treat fungal infections such as candidiasis in humans. Their extensive use has led to the emergence of drug resistance, complicating antifungal therapy for yeast infections in critically ill patients. Combination therapy has become popular in clinical practice as a potential strategy to fight resistant fungal isolates. Recently, amphiphilic tobramycin analogues, C12 and C14, were shown to display antifungal activities. Herein, the antifungal synergy of C12 and C14 with four azoles, fluconazole (FLC), itraconazole (ITC), posaconazole (POS), and voriconazole (VOR), was examined against seven Candida albicans strains. All tested strains were synergistically inhibited by C12 when combined with azoles, with the exception of C. albicans 64124 and MYA-2876 by FLC and VOR. Likewise, when combined with POS and ITC, C14 exhibited synergistic growth inhibition of all C. albicans strains, except C. albicans MYA-2876 by ITC. The combinations of FLC-C14 and VOR-C14 showed synergistic antifungal effect against three C. albicans and four C. albicans strains, respectively. Finally, synergism between C12/C14 and POS were confirmed by time-kill and disk diffusion assays. These results suggest the possibility of combining C12 or C14 with azoles to treat invasive fungal infections at lower administration doses or with a higher efficiency. PMID:26594050

  20. Voriconazole treatment of Candida tropicalis meningitis: persistence of (1,3)-β-d-glucan in the cerebrospinal fluid is a marker of clinical and microbiological failure

    PubMed Central

    Ceccarelli, Giancarlo; Ghezzi, Maria Cristina; Raponi, Giammarco; Brunetti, Grazia; Marsiglia, Carolina; Fallani, Stefania; Novelli, Andrea; Venditti, Mario

    2016-01-01

    Abstract Introduction: Infections are still the most common complications of cerebral shunt procedures. Even though fungal etiologies are considered to be rare, they are associated with significant morbidity and mortality. Due to their uncommonness, diagnostic procedures and optimal therapy are poorly defined. We report a case of Candida tropicalis infection of ventriculo-peritoneal cerebrospinal fluid (CSF) shunt in a 49-year-old immune competent male treated with voriconazole (VOR). Methods: Microbiological and CSF markers (1,3-b-D-glucan-BDG) of fungal infection, biofilm production capacity, sensitivity of serial isolates of the pathogen, and the concentration of the antifungal drug have been monitored and related to the clinical course of this infection. Results: Despite appropriate treatment with VOR, in terms of adequate achieved CSF drug concentrations and initial effective therapeutic response, loss of VOR susceptibility of the C tropicalis and treatment failure were observed. Conclusion: Biofilm production of the C. tropicalis isolate might have had a significant role in treatment failure. Of interest, clinical and microbiological unfavorable outcome was anticipated by persistence of BDG in CSF. Rising titers of this marker were associated with relapse of fungal infection. PMID:27495087

  1. A combination approach to treating fungal infections.

    PubMed

    Shrestha, Sanjib K; Fosso, Marina Y; Garneau-Tsodikova, Sylvie

    2015-01-01

    Azoles are antifungal drugs used to treat fungal infections such as candidiasis in humans. Their extensive use has led to the emergence of drug resistance, complicating antifungal therapy for yeast infections in critically ill patients. Combination therapy has become popular in clinical practice as a potential strategy to fight resistant fungal isolates. Recently, amphiphilic tobramycin analogues, C12 and C14, were shown to display antifungal activities. Herein, the antifungal synergy of C12 and C14 with four azoles, fluconazole (FLC), itraconazole (ITC), posaconazole (POS), and voriconazole (VOR), was examined against seven Candida albicans strains. All tested strains were synergistically inhibited by C12 when combined with azoles, with the exception of C. albicans 64124 and MYA-2876 by FLC and VOR. Likewise, when combined with POS and ITC, C14 exhibited synergistic growth inhibition of all C. albicans strains, except C. albicans MYA-2876 by ITC. The combinations of FLC-C14 and VOR-C14 showed synergistic antifungal effect against three C. albicans and four C. albicans strains, respectively. Finally, synergism between C12/C14 and POS were confirmed by time-kill and disk diffusion assays. These results suggest the possibility of combining C12 or C14 with azoles to treat invasive fungal infections at lower administration doses or with a higher efficiency. PMID:26594050

  2. Evaluation of the Effects of Ketoconazole and Voriconazole on the Pharmacokinetics of Oxcarbazepine and Its Main Metabolite MHD in Rats by UPLC-MS-MS.

    PubMed

    Chen, Xinxin; Gu, Ermin; Wang, Shuanghu; Zheng, Xiang; Chen, Mengchun; Wang, Li; Hu, Guoxin; Cai, Jian-ping; Zhou, Hongyu

    2016-03-01

    Oxcarbazepine (OXC), a second-generation antiepileptic drug, undergoes rapid reduction with formation of the active metabolite 10,11-dihydro-10-hydroxy-carbazepine (MHD) in vivo. In this study, a method for simultaneous determination of OXC and MHD in rat plasma using ultra-performance liquid chromatography with tandem mass spectrometry (UPLC-MS-MS) was developed and validated. Under given chromatographic conditions, OXC, MHD and internal standard diazepam were separated well and quantified by electrospray positive ionization mass spectrometry in the multiple reaction monitoring transitions mode. The method validation demonstrated good linearity over the range of 10-2,000 ng/mL for OXC and 5-1,000 ng/mL for MHD. The lower limit of quantification was 5 ng/mL for OXC and 2.5 ng/mL for MHD, respectively. The method was successfully applied to the evaluation of the pharmacokinetics of OXC and MHD in rats, with or without pretreatment by ketoconazole (KET) and voriconazole (VOR). Statistics indicated that KET and VOR significantly affected the disposition of OXC and MHD in vivo, whereas VOR predominantly interfered with the disposition of MHD. This method is suitable for pharmacokinetic study in small animals. PMID:26499119

  3. The statistical uncertainty of changes in winter storms over the North Atlantic and Europe in an ensemble of transient climate simulations

    NASA Astrophysics Data System (ADS)

    Della-Marta, Paul M.; Pinto, Joaquim G.

    2010-05-01

    Winter storms are among the most important natural hazards affecting Europe. We quantify changes in storm frequency and intensity over the North Atlantic and Europe under future climate scenarios in terms of return periods (RP) considering uncertainties due to both sampling and methodology. With this aim, ensemble simulations with the coupled ECHAM5/MPI-OM1 GCM for recent climate conditions (20C, 1960-2000) and future climate scenarios (SRES A1B and A2, 2001-2100) are analyzed. RPs of North Atlantic storms' minimum central pressure (CP) and maximum vorticity (VOR) remain unchanged by 2100 for both the A1B and A2 SRES scenarios compared to the recent climate (1960-2000). Whereas shortened RPs for VOR of all intensities are detected for the area between British Isles/North-Sea/western Europe as early as 2040. CP RP of future storms in this area are significant shorter only for lower intensity events. These results indicate that storms could become more intense during the 21st century. However, the changes in storm VOR RP may be unrealistically large: a present day 50 (20) year event becomes approximately a 9 (5.5) year event in both A1B and A2 scenarios by 2100. The detected shortened RPs of storms implies a higher risk of occurrence of damaging wind events over Europe.

  4. Multisensory integration in balance control.

    PubMed

    Bronstein, A M

    2016-01-01

    This chapter provides an introduction to the topic of multisensory integration in balance control in, both, health and disease. One of the best-studied examples is that of visuo-vestibular interaction, which is the ability of the visual system to enhance or suppress the vestibulo-ocular reflex (VOR suppression). Of clinical relevance, examination of VOR suppression is clinically useful because only central, not peripheral, lesions impair VOR suppression. Visual, somatosensory (proprioceptive), and vestibular inputs interact strongly and continuously in the control of upright balance. Experiments with visual motion stimuli show that the visual system generates visually-evoked postural responses that, at least initially, can override vestibular and proprioceptive signals. This paradigm has been useful for the study of the syndrome of visual vertigo or vision-induced dizziness, which can appear after vestibular disease. These patients typically report dizziness when exposed to optokinetic stimuli or visually charged environments, such as supermarkets. The principles of the rehabilitation treatment of these patients, which use repeated exposure to visual motion, are presented. Finally, we offer a diagnostic algorithm in approaching the patient reporting oscillopsia - the illusion of oscillation of the visual environment, which should not be confused with the syndrome mentioned earlier of visual vertigo. PMID:27638062

  5. Resolution of sensory ambiguities for gaze stabilization requires a second neural integrator

    NASA Technical Reports Server (NTRS)

    Green, Andrea M.; Angelaki, Dora E.

    2003-01-01

    The ability to simultaneously move in the world and maintain stable visual perception depends critically on the contribution of vestibulo-ocular reflexes (VORs) to gaze stabilization. It is traditionally believed that semicircular canal signals drive compensatory responses to rotational head disturbances (rotational VOR), whereas otolith signals compensate for translational movements [translational VOR (TVOR)]. However, a sensory ambiguity exists because otolith afferents are activated similarly during head translations and reorientations relative to gravity (i.e., tilts). Extra-otolith cues are, therefore, necessary to ensure that dynamic head tilts do not elicit a TVOR. To investigate how extra-otolith signals contribute, we characterized the temporal and viewing distance-dependent properties of a TVOR elicited in the absence of a lateral acceleration stimulus to the otoliths during combined translational/rotational motion. We show that, in addition to otolith signals, angular head position signals derived by integrating sensory canal information drive the TVOR. A physiological basis for these results is proposed in a model with two distinct integration steps. Upstream of the well known oculomotor velocity-to-position neural integrator, the model incorporates a separate integration element that could represent the "velocity storage integrator," whose functional role in the oculomotor system has so far remained controversial. We propose that a key functional purpose of the velocity storage network is to temporally integrate semicircular canal signals, so that they may be used to extract translation information from ambiguous otolith afferent signals in the natural and functionally relevant bandwidth of head movements.

  6. Evaluation of the otolith function using sinusoidal off-vertical axis rotation in patients with benign paroxysmal positional vertigo.

    PubMed

    Sugita-Kitajima, Akemi; Azuma, Miki; Hattori, Kosuke; Koizuka, Izumi

    2007-07-01

    The vestibulo-ocular reflex (VOR) was studied via sinusoidal off-vertical axis rotation (OVAR) to evaluate the otolith function in patients with benign paroxysmal positional vertigo (BPPV). Subjects were sinusoidally rotated with eyes open in complete darkness at frequencies of 0.4 and 0.8 Hz with a maximum angular velocity of 60 degrees s(-1) in earth-vertical axis rotation (EVAR) and OVAR. Twenty-three controls and 24 BPPV patients were investigated. Results showed that VOR gain during OVAR at 0.8 Hz in a 30 degrees nose-up position in BPPV patients was significantly less than the gain during EVAR, whereas the gain was not significantly different between EVAR and OVAR in the controls in each condition. In addition, to examine each type of BPPV, we also investigated whether there were any differences between the patients who suffered from dizziness and those who did not. VOR gain in OVAR of BPPV patients who were suffering from dizziness was significantly less than that of BPPV patients without dizziness. Not only cupulolithiasis or canalolithiasis, but also otolith dysfunction was considered to be the possible origin of BPPV. Because sinusoidal OVAR produced minimal nausea compared to constant velocity OVAR, the stimulation of 0.8 Hz nose-up in sinusoidal OVAR may be used to evaluate otolith function without discomfort for patients. PMID:17597299

  7. Interaction of spatial perception, vestibular function, and exercise in young school age boys with learning disabilities.

    PubMed

    Byl, N N; Byl, F M; Rosenthal, J H

    1989-06-01

    Form rotation, figure directionality, and figure-ground discrimination were evaluated before and after 10 days of vestibular or aerobic exercises for 30 boys (7 to 12 yr.) who showed problems in learning, reading, and inattention. Eight subjects had normal vestibulo-ocular reflex (VOR) responses as determined by caloric and rotational testing. They were assigned to a vestibular program (Control Group I). The 22 subjects with abnormal VOR test responses were randomly assigned to either aerobic exercises (Experimental Group II) or a vestibular program (Experimental Group III). Spatial perceptual test scores varied widely, with the majority performing below age-expected norms but no significant differences on vestibular status appeared. Postexercise, only subjects completing the vestibular program made significant gains: Experimental Group III (abnormal VOR) made significant gains in accuracy and normal test responses compared to the other groups, and Control Group I made significantly greater gains in speed of spatial perceptual processing. For boys with problems in learning, reading, inattention, and vestibular function, a vestibular exercise program complementing a traditional or special educational program may enhance the spatial perceptual skills needed for reading.

  8. Destruction of Alicyclobacillus acidoterrestris spores in apple juice on stainless steel surfaces by chemical disinfectants.

    PubMed

    Podolak, Richard; Elliott, Philip H; Taylor, Bradley J; Khurana, Aakash; Black, Darryl G

    2009-03-01

    A study was conducted to determine the effects of three commercially available disinfectants on the reduction of Alicyclobacillus acidoterrestris spores in single-strength apple juice applied to stainless steel surfaces. Apple juice was inoculated with A. acidoterrestris spores, spread onto the surface of stainless steel chips (SSC), dried to obtain spore concentrations of approximately 10(4) CFU/cm2, and treated with disinfectants at temperatures ranging from 40 to 90 degrees C. The concentrations of disinfectants were 200, 500, 1,000, and 2,000 ppm of total chlorine for Clorox (CL) (sodium hypochlorite); 50, 100, and 200 ppm of total chlorine for Carnebon 200 (stabilized chlorine dioxide); and 1,500, 2,000, and 2,600 ppm for Vortexx (VOR) (hydrogen peroxide, peroxyacetic acid, and octanoic acid). For all temperatures tested, VOR at 2,600 ppm (90 degrees C) and CL at 2,000 ppm (90 degrees C) were the most inhibitory against A. acidoterrestris spores, resulting in 2.55- and 2.32-log CFU/cm2 reductions, respectively, after 2 min. All disinfectants and conditions tested resulted in the inactivation of A. acidoterrestris spores, with a maximum reduction of > 2 log CFU/cm2. Results from this study indicate that A. acidoterrestris spores, in single-strength apple juice, may be effectively reduced on stainless steel surface by VOR and CL, which may have practical applications in the juice industry.

  9. Dissociation of locomotor and cerebellar deficits in a murine Angelman syndrome model

    PubMed Central

    Bruinsma, Caroline F.; Schonewille, Martijn; Gao, Zhenyu; Aronica, Eleonora M.A.; Judson, Matthew C.; Philpot, Benjamin D.; Hoebeek, Freek E.; van Woerden, Geeske M.; De Zeeuw, Chris I.; Elgersma, Ype

    2015-01-01

    Angelman syndrome (AS) is a severe neurological disorder that is associated with prominent movement and balance impairments that are widely considered to be due to defects of cerebellar origin. Here, using the cerebellar-specific vestibulo-ocular reflex (VOR) paradigm, we determined that cerebellar function is only mildly impaired in the Ube3am–/p+ mouse model of AS. VOR phase-reversal learning was singularly impaired in these animals and correlated with reduced tonic inhibition between Golgi cells and granule cells. Purkinje cell physiology, in contrast, was normal in AS mice as shown by synaptic plasticity and spontaneous firing properties that resembled those of controls. Accordingly, neither VOR phase-reversal learning nor locomotion was impaired following selective deletion of Ube3a in Purkinje cells. However, genetic normalization of αCaMKII inhibitory phosphorylation fully rescued locomotor deficits despite failing to improve cerebellar learning in AS mice, suggesting extracerebellar circuit involvement in locomotor learning. We confirmed this hypothesis through cerebellum-specific reinstatement of Ube3a, which ameliorated cerebellar learning deficits but did not rescue locomotor deficits. This double dissociation of locomotion and cerebellar phenotypes strongly suggests that the locomotor deficits of AS mice do not arise from impaired cerebellar cortex function. Our results provide important insights into the etiology of the motor deficits associated with AS. PMID:26485287

  10. Kultivierungsverfahren für Bakterien

    NASA Astrophysics Data System (ADS)

    Messelhäußer, Ute

    Lange Zeit war die Isolierung bakterieller pathogener Mikroorganismen mithilfe von entsprechenden Nährmedien die einzige Möglichkeit zum Nachweis der Erreger in Lebensmittel-, Human- und Veterinärproben. Diese Vorgehensweise wurde Mitte des 19. Jahrhunderts entwickelt. Damals gehörte Louis Pasteur zu den ersten Mikrobiologen, die es für notwendig erachteten, Krankheitserreger auch außerhalb des menschlichen Körpers kultivieren zu können und entwickelte deshalb 1861 die erste flüssige Anreicherungsbouillon [7]. Er legte damit einen der Grundsteine für die heutige mikrobiologische Diagnostik und alle weiteren, darauf aufbauenden Disziplinen. Grundlage der modernen bakteriellen Lebensmittelsuntersuchung sind, im Gegensatz zur viralen Diagnostik, nach wie vor entsprechende Anreicherungsschritte. Vor allem die oftmals sehr geringe Infektionsdosis der unterschiedlichen lebensmittelrelevanten Infektionserreger bedingt eine Nulltoleranz derartiger Mikroorganismen in verzehrfertigen Lebensmitteln und somit die Notwendigkeit einer Kultivierung mittels unterschiedlicher Anreicherungsmethoden vor dem Einsatz molekularer Nachweisverfahren, wie z. B. PCR und Real-Time-PCR. Nach den derzeitigen gesetzlichen Vorgaben ist zusätzlich zu dem molekularbiologischen Nachweis von Infektions- und Intoxikationserregern in der Lebensmittelanalytik der kulturelle Keimnachweis zwingend notwendig. Molekulare Nachweisverfahren können somit entweder als Screeningmethoden für einen schnellen und hohen Probendurchsatz oder nach entsprechenden Kultivierungsschritten zur Bestätigung bestimmter genetischer Eigenschaften von Isolaten herangezogen werden [12].

  11. Active linear head motion improves dynamic visual acuity in pursuing a high-speed moving object.

    PubMed

    Hasegawa, Tatsuhisa; Yamashita, Masayuki; Suzuki, Toshihiro; Hisa, Yasuo; Wada, Yoshiro

    2009-04-01

    We usually move both our eyes and our head when pursuing a high-speed moving object. However, the vestibulo-ocular reflex (VOR), evoked by head motion, seems to disturb smooth pursuit eye movement because the VOR stabilizes the gaze against head motion. To determine whether head motion is advantageous for pursuing a high-speed moving object, we examined dynamic visual acuity (DVA) for a high-speed (80 degrees /s) rightward moving object with and without active linear rightward head motion (HM) at a maximum of 50 cm/s in nine healthy subjects. Furthermore, we analyzed eye and head movements to investigate the contribution of linear VOR (LVOR) and smooth eye movement under these conditions. In most subjects, active linear head motion improved DVA for a high-speed moving object. Subjects with higher DVA scores under HM had robust rightward gaze (eye + head) velocities (>60 cm/s), i.e., rightward smooth eye movements (>10 degrees /s). With the head stationary (HS), faster smooth eye movements (>40 degrees /s) were generated when the subjects pursued a high-speed moving object. They also showed anticipatory smooth eye movements under conditions HM and HS. However, the level of suppression of their LVOR abilities was equal to that of the others. These results suggest that the ability to generate anticipatory smooth pursuit eye movements for following a high-speed moving object against the LVOR is a determining factor for improvement of DVA under HM.

  12. Effect of vestibular rehabilitation on passive dynamic visual acuity.

    PubMed

    Scherer, Matthew; Migliaccio, Americo A; Schubert, Michael C

    2008-01-01

    While active dynamic visual acuity (DVA) has been shown to improve with gaze stabilization exercises, we sought to determine whether DVA during passive head impulses (pDVA) would also improve following a rehabilitation course of vestibular physical therapy (VPT) in patients with unilateral and bilateral vestibular hypofunction. VPT consisted of gaze and gait stabilization exercises done as a home exercise program. Scleral search coil was used to characterize the angular vestibulo-ocular reflex (aVOR) during pDVA before and after VPT. Mean duration of VPT was 66 +/- 24 days, over a total of 5 +/- 1.4 outpatient visits. Two of three subjects showed improvements in pDVA with a mean reduction of 43% (LogMAR 0.58 to 0.398 and 0.92 to 0.40). Our data suggest improvements in pDVA may be due in part to improvements in aVOR velocity and acceleration gains or reduced latency of the aVOR. Each subject demonstrated a reduction in the ratio of compensatory saccades to head impulses after VPT. Preliminary data suggest that active gaze stability exercises may contribute to improvements in pDVA in some individuals.

  13. Primate translational vestibuloocular reflexes. I. High-frequency dynamics and three-dimensional properties during lateral motion

    NASA Technical Reports Server (NTRS)

    Angelaki, D. E.; McHenry, M. Q.; Hess, B. J.

    2000-01-01

    The dynamics and three-dimensional (3-D) properties of the primate translational vestibuloocular reflex (trVOR) for high-frequency (4-12 Hz, +/-0.3-0.4 g) lateral motion were investigated during near-target viewing at center and eccentric targets. Horizontal response gains increased with frequency and depended on target eccentricity. The larger the horizontal and vertical target eccentricity, the steeper the dependence of horizontal response gain on frequency. In addition to horizontal eye movements, robust torsional response components also were present at all frequencies. During center-target fixation, torsional response phase was opposite (anticompensatory) to that expected for an "apparent" tilt response. Instead torsional response components depended systematically on vertical-target eccentricity, increasing in amplitude when looking down and reversing phase when looking up. As a result the trVOR eye velocity vector systematically tilted away from a purely horizontal direction, through an angle that increased with vertical eccentricity with a slope of approximately 0.7. This systematic dependence of torsional eye velocity tilt on vertical eye position suggests that the trVOR might follow the 3-D kinematic requirements that have been shown to govern visually guided eye movements and near-target fixation.

  14. Primate translational vestibuloocular reflexes. III. Effects of bilateral labyrinthine electrical stimulation

    NASA Technical Reports Server (NTRS)

    Angelaki, D. E.; McHenry, M. Q.; Dickman, J. D.; Perachio, A. A.

    2000-01-01

    The effects of functional, reversible ablation and potential recruitment of the most irregular otolith afferents on the dynamics and sensitivity of the translational vestibuloocular reflexes (trVORs) were investigated in rhesus monkeys trained to fixate near and far targets. Translational motion stimuli consisted of either steady-state lateral and fore-aft sinusoidal oscillations or short-lasting transient lateral head displacements. Short-duration (usually <2 s) anodal (inhibitory) and cathodal (excitatory) currents (50-100 microA) were delivered bilaterally during motion. In the presence of anodal labyrinthine stimulation, trVOR sensitivity and its dependence on viewing distance were significantly decreased. In addition, anodal currents significantly increased phase lags. During transient motion, anodal stimulation resulted in significantly lower initial eye acceleration and more sluggish responses. Cathodal currents tended to have opposite effects. The main characteristics of these results were simulated by a simple model where both regularly and irregularly discharging afferents contribute to the trVORs. Anodal labyrinthine currents also were found to decrease eye velocity during long-duration, constant velocity rotations, although results were generally more variable compared with those during translational motion.

  15. Dual adaptation and adaptive generalization of the human vestibulo-ocular reflex

    NASA Technical Reports Server (NTRS)

    Welch, R. B.; Bridgeman, B.; Williams, J. A.; Semmler, R.

    1998-01-01

    In two experiments, we examined the possibility that the human vestibulo-ocular reflex (VOR) is subject to dual adaptation (the ability to adapt to a sensory rearrangement more rapidly and/or more completely after repeated experience with it) and adaptive generalization (the ability to adapt more readily to a novel sensory rearrangement as a result of prior dual adaptation training). In Experiment 1, the subjects actively turned the head during alternating exposure to a visual-vestibular rearrangement (target/head gain = 0.5) and the normal situation (target/head gain = 0.0). These conditions produced both adaptation and dual adaptation of the VOR but no evidence of adaptive generalization when tested with a target/head gain of 1.0. Experiment 2, in which exposure to the 0.5 gain entailed externally controlled (i.e., passive) whole body rotation, resulted in VOR adaptation but no dual adaptation. As in Experiment 1, no evidence of adaptive generalization was found.

  16. Primate translational vestibuloocular reflexes. IV. Changes after unilateral labyrinthectomy

    NASA Technical Reports Server (NTRS)

    Angelaki, D. E.; Newlands, S. D.; Dickman, J. D.

    2000-01-01

    The effects of unilateral labyrinthectomy on the properties of the translational vestibuloocular reflexes (trVORs) were investigated in rhesus monkeys trained to fixate near targets. Translational motion stimuli consisted of either steady-state lateral and fore-aft sinusoidal oscillations or short-lasting transient displacements. During small-amplitude, steady-state sinusoidal lateral oscillations, a small decrease in the horizontal trVOR sensitivity and its dependence on viewing distance was observed during the first week after labyrinthectomy. These deficits gradually recovered over time. In addition, the vertical response component increased, causing a tilt of the eye velocity vector toward the lesioned side. During large, transient lateral displacements, the deficits were larger and longer lasting. Responses after labyrinthectomy were asymmetric, with eye velocity during movements toward the side of the lesion being more compromised. The most profound effect of the lesions was observed during fore-aft motion. Whereas responses were kinematically appropriate for fixation away from the side of the lesion (e.g., to the left after right labyrinthectomy), horizontal responses were anticompensatory during fixation at targets located ipsilateral to the side of the lesion (e.g., for targets to the right after right labyrinthectomy). This deficit showed little recovery during the 3-mo post-labyrinthectomy testing period. These results suggest that inputs from both labyrinths are important for the proper function of the trVORs, although the details of how bilateral signals are processed and integrated remain unknown.

  17. The human vestibulo-ocular reflex during linear locomotion

    NASA Technical Reports Server (NTRS)

    Moore, S. T.; Hirasaki, E.; Raphan, T.; Cohen, B.

    2001-01-01

    During locomotion, there is a translation and compensatory rotation of the head in both the vertical and horizontal planes. During moderate to fast walking (100 m/min), vertical head translation occurs at the frequency of stepping (2 Hz) and generates peak linear acceleration of 0.37 g. Lateral head translation occurs at the stride frequency (1 Hz) and generates peak linear acceleration of 0.1 g. Peak head pitch and yaw angular velocities are approximately 17 degrees/s. The frequency and magnitude of these head movements are within the operational range of both the linear and angular vestibulo-ocular reflex (IVOR and aVOR). Vertical eye movements undergo a phase reversal from near to far targets. When viewing a far (>1 m) target, vertical eye velocity is typical of an aVOR response; that is, it is compensatory for head pitch. At close viewing distances (<1 m), vertical eye velocity is in phase with head pitch and is compensatory for vertical head translation, suggesting that the IVOR predominantly generates the eye movement response. Horizontal head movements during locomotion occur at the stride frequency of 1 Hz, where the IVOR gain is low. Horizontal eye movements are compensatory for head yaw at all viewing distances and are likely generated by the aVOR.

  18. Next Generation Life Support Project Status

    NASA Technical Reports Server (NTRS)

    Barta, Daniel J.; Chullen, Cinda; Pickering, Karen D.; Cox, Marlon; Towsend, Neil; Campbell, Colin; Flynn, Michael; Wheeler, Raymond

    2012-01-01

    Next Generation Life Support (NGLS) is one of several technology development projects sponsored by NASA s Game Changing Development Program. The NGLS Project is developing life support technologies (including water recovery and space suit life support technologies) needed for humans to live and work productively in space. NGLS has three project tasks: Variable Oxygen Regulator (VOR), Rapid Cycle Amine (RCA) swing bed, and Alternative Water Processor (AWP). The RCA swing bed and VOR tasks are directed at key technology needs for the Portable Life Support System (PLSS) for an Advanced Extravehicular Mobility Unit, with focus on test article development and integrated testing in an Advanced PLSS in cooperation with the Advanced Extra Vehicular Activity (EVA) Project. An RCA swing-bed provides integrated carbon dioxide removal and humidity control that can be regenerated in real time during an EVA. The VOR technology will significantly increase the number of pressure settings available to the space suit. Current space suit pressure regulators are limited to only two settings whereas the adjustability of the advanced regulator will be nearly continuous. The AWP effort, based on natural biological processes and membrane-based secondary treatment, will result in the development of a system capable of recycling wastewater from sources expected in future exploration missions, including hygiene and laundry water. This paper will provide a status of technology development activities and future plans.

  19. Renaturierung von Sandökosystemen im Binnenland

    NASA Astrophysics Data System (ADS)

    Schwabe-Kratochwil, Angelika; Kratochwil, Anselm

    Das Vorkommen von Sandökosystemen im Binnenland (Flugsand- und Decksandfelder, Dünen) ist vor allem an Sand-Akkumulationen der vorletzten Eiszeit (in Nordeuropa: Saaleeiszeit und Sand-Ablagerungen an größeren Flüssen gebunden. So finden wir die Verbreitungsschwerpunkte von binnenländischen Sandökosystemen in Mitteleuropa einerseits vor allem im Bereich der flächenhaften saalezeitlichen Ablagerungen in den Niederlanden und in Norddeutschland (Castel et al. 1989), andererseits kommen Sandökosysteme des Binnenlandes linear in den Flussgebieten z.B. von Maas, Rhein, Ems, Elbe, Oder und Regnitz vor. In Niederösterreich fanden sich einst großflächige Dünen- und Flugsandgebiete im Marchfeld östlich von Wien (Wiesbauer et al. 1997). Die Flugsandbildung setzte bereits im Spätglazial ca. 11000 v. Chr. ein, als eine den Sand fixierende Vegetation noch fehlte. Es bildeten sich im norddeutschen Raum aus den leicht verwehbaren Talsanden bereits um 9000 v. Chr.

  20. Vestibuloocular reflex of rhesus monkeys after spaceflight

    NASA Technical Reports Server (NTRS)

    Cohen, Bernard; Kozlovskaia, Inessa; Raphan, Theodore; Solomon, David; Helwig, Denice; Cohen, Nathaniel; Sirota, Mikhail; Iakushin, Sergei

    1992-01-01

    The vestibuloocular reflex (VOR) of two rhesus monkeys was recorded before and after 14 days of spaceflight. The gain (eye velocity/head velocity) of the horizontal VOR, tested 15 and 18 h after landing, was approximately equal to preflight values. The dominant time constant of the animal tested 15 h after landing was equivalent to that before flight. During nystagmus induced by off-vertical axis rotation (OVAR), the latency, rising time constant, steady-state eye velocity, and phase of modulation in eye velocity and eye position with respect to head position were similar in both monkeys before and after flight. There were changes in the amplitude of modulation of horizontal eye velocity during steady-state OVAR and in the ability to discharge stored activity rapidly by tilting during postrotatory nystagmus (tilt dumping) after flight: OVAR modulations were larger, and tilt dumping was lost in the one animal tested on the day of landing and for several days thereafter. If the gain and time constant of the horizontal VOR exchange in microgravity, they must revert to normal soon after landing. The changes that were observed suggest that adaptation to microgravity had caused alterations in way that the central nervous system processes otolith input.

  1. Three dimensional eye movements of squirrel monkeys following postrotatory tilt

    NASA Technical Reports Server (NTRS)

    Merfeld, D. M.; Young, L. R.; Paige, G. D.; Tomko, D. L.

    1993-01-01

    Three-dimensional squirrel monkey eye movements were recorded during and immediately following rotation around an earth-vertical yaw axis (160 degrees/s steady state, 100 degrees/s2 acceleration and deceleration). To study interactions between the horizontal angular vestibulo-ocular reflex (VOR) and head orientation, postrotatory VOR alignment was changed relative to gravity by tilting the head out of the horizontal plane (pitch or roll tilt between 15 degrees and 90 degrees) immediately after cessation of motion. Results showed that in addition to post rotatory horizontal nystagmus, vertical nystagmus followed tilts to the left or right (roll), and torsional nystagmus followed forward or backward (pitch) tilts. When the time course and spatial orientation of eye velocity were considered in three dimensions, the axis of eye rotation always shifted toward alignment with gravity, and the postrotatory horizontal VOR decay was accelerated by the tilts. These phenomena may reflect a neural process that resolves the sensory conflict induced by this postrotatory tilt paradigm.

  2. Dissociation of locomotor and cerebellar deficits in a murine Angelman syndrome model.

    PubMed

    Bruinsma, Caroline F; Schonewille, Martijn; Gao, Zhenyu; Aronica, Eleonora M A; Judson, Matthew C; Philpot, Benjamin D; Hoebeek, Freek E; van Woerden, Geeske M; De Zeeuw, Chris I; Elgersma, Ype

    2015-11-01

    Angelman syndrome (AS) is a severe neurological disorder that is associated with prominent movement and balance impairments that are widely considered to be due to defects of cerebellar origin. Here, using the cerebellar-specific vestibulo-ocular reflex (VOR) paradigm, we determined that cerebellar function is only mildly impaired in the Ube3am-/p+ mouse model of AS. VOR phase-reversal learning was singularly impaired in these animals and correlated with reduced tonic inhibition between Golgi cells and granule cells. Purkinje cell physiology, in contrast, was normal in AS mice as shown by synaptic plasticity and spontaneous firing properties that resembled those of controls. Accordingly, neither VOR phase-reversal learning nor locomotion was impaired following selective deletion of Ube3a in Purkinje cells. However, genetic normalization of αCaMKII inhibitory phosphorylation fully rescued locomotor deficits despite failing to improve cerebellar learning in AS mice, suggesting extracerebellar circuit involvement in locomotor learning. We confirmed this hypothesis through cerebellum-specific reinstatement of Ube3a, which ameliorated cerebellar learning deficits but did not rescue locomotor deficits. This double dissociation of locomotion and cerebellar phenotypes strongly suggests that the locomotor deficits of AS mice do not arise from impaired cerebellar cortex function. Our results provide important insights into the etiology of the motor deficits associated with AS. PMID:26485287

  3. Effects of long-duration space flights on characteristics of the vertical gaze fixation reaction.

    PubMed

    Tomilovskaya, E S; Berger, M; Gerstenbrand, F; Kozlovskaya, I B

    2013-01-01

    The aim of the study was to examine effects of long-duration exposure to weightlessness on characteristics of the vertical gaze fixation reaction (GFR). The subjects were to perform the target acquisition task on visual stimuli that appeared at a distance of 16 deg. up- and down from the primary position in a random order. Experiments were performed before launch, during flight and after landing. Before flight time of gaze fixation reaction did not exceed 650 ms. During space flight (SF) it extended up to 900-1000 ms and more. The velocities of head movement in space decreased, but the velocities of eye counterrotation decreased to a lesser degree. This difference resulted in sharp increase of vertical vestibular ocular reflex (VOR) gain (up to 4.3 values in one of the cosmonauts) during the 1st month of flight; further it decreased reaching the values of 0.5-0.7 on the 5th month of SF. After landing vertical VOR gain increased greatly again. These results in the vertical axis are in agreement with the data of Kozlovskaya et al., which showed in experiments with monkeys that horizontal VOR gain increased together with redundant inadequate responses of vestibular nucleus on vestibular stimulation and that in the course of adaptation to these conditions central nervous system inhibited vestibular input from the motor control system.

  4. Vestibular Performance During High-Acceleration Stimuli Correlates with Clinical Decline in SCA6.

    PubMed

    Huh, Young Eun; Kim, Ji-Soo; Kim, Hyo-Jung; Park, Seong-Ho; Jeon, Beom Seok; Kim, Jong-Min; Cho, Jin Whan; Zee, David S

    2015-06-01

    In spinocerebellar ataxia type 6 (SCA6), the vestibular dysfunction and its correlation with other clinical parameters require further exploration. We determined vestibular responses over a broad range of stimulus acceleration in 11 patients with SCA6 (six men, age range=33-72 years, mean age±SD=59±12 years) using bithermal caloric irrigations, rotary chair, and head impulse tests. Correlations were also pursued among disability scores, as measured using the International Cooperative Ataxia Rating Scale, disease duration, age at onset, cytosine-adenine-guanine (CAG) repeat length, and the gain of the vestibulo-ocular reflex (VOR). In response to relatively low-acceleration, low-frequency rotational and bithermal caloric stimuli, the VOR gains were normal or increased regardless of the severity of disease. On the other hand, with relatively high-acceleration, high-frequency head impulses, there was a relative increase in gain in the mildly affected patients and a decrease in gain in the more severely affected patients and gains were negatively correlated with the severity of disease (Spearman correlation, R=-0.927, p<0.001). Selective decrease of the vestibular responses during high-acceleration, high-frequency stimuli may be ascribed to degeneration of either the flocculus or vestibular nuclei. The performance of the VOR during high-acceleration, high-frequency head impulses may be a quantitative indicator of clinical decline in SCA6.

  5. Effect of vestibular rehabilitation on passive dynamic visual acuity

    PubMed Central

    Scherer, Matthew; Migliaccio, Americo A.; Schubert, Michael C.

    2010-01-01

    While active dynamic visual acuity (DVA) has been shown to improve with gaze stabilization exercises, we sought to determine whether DVA during passive head impulses (pDVA) would also improve following a rehabilitation course of vestibular physical therapy (VPT) in patients with unilateral and bilateral vestibular hypofunction. VPT consisted of gaze and gait stabilization exercises done as a home exercise program. Scleral search coil was used to characterize the angular vestibulo-ocular reflex (aVOR) during pDVA before and after VPT. Mean duration of VPT was 66 ± 24 days, over a total of 5 ± 1.4 outpatient visits. Two of three subjects showed improvements in pDVA with a mean reduction of 43% (LogMAR 0.58 to 0.398 and 0.92 to 0.40). Our data suggest improvements in pDVA may be due in part to improvements in aVOR velocity and acceleration gains or reduced latency of the aVOR. Each subject demonstrated a reduction in the ratio of compensatory saccades to head impulses after VPT. Preliminary data suggest that active gaze stability exercises may contribute to improvements in pDVA in some individuals. PMID:19126985

  6. Entwicklung und methodische Verbesserung der Arbeitssicherheit in der Instandhaltung

    NASA Astrophysics Data System (ADS)

    Galinski, Marek

    Die Hüttenwerke Krupp Mannesmann gehören zu den führenden Stahlherstellern in Europa. Die Instandhaltung ist einerseits den Anlagen vor Ort zugeordnet, andererseits gibt es für werksweite bzw. spezielle Themen eine zentrale Instandhaltung. Die im Folgenden beschriebenen Methoden wurden für das gesamte Unternehmen entwickelt, jedoch je nach Organisationseinheit unterschiedlich adaptiert und unterschiedlich intensiv verfolgt. Die zentrale Instandhaltung hat insbesondere in den letzten 12 Jahren der Arbeitssicherheit einen hohen Stellenwert beigemessen, und hervorragende Ergebnisse erzielt. So ist die Unfallhäufigkeit in der zentralen Instandhaltung von ca. 30 anzeigepflichtigen Unfällen pro eine Million verfahrener Stunden vor ca. 15 Jahren auf Null in 2007 gesunken! In 2008 konnte dieses hervorragende Ergebnis gehalten werden. Zwei Jahre unfallfrei! Wer hätte das vor 15 Jahren gedacht? Der Schwerpunkt des Beitrags liegt auf der Erläuterung der Ansatzpunkte mit denen dieses Ergebnis erreicht wurde und der Darstellung der Methoden incl. der Anpassung an die veränderten Ansatzpunkte in den betroffenen Bereichen. Die beschriebenen Methoden sind in der zentralen Instandhaltung so angewendet worden.

  7. An internal model of head kinematics predicts the influence of head orientation on reflexive eye movements.

    PubMed

    Zupan, L H; Merfeld, D M

    2005-09-01

    Our sense of self-motion and self-orientation results from combining information from different sources. We hypothesize that the central nervous system (CNS) uses internal models of the laws of physics to merge cues provided by different sensory systems. Different models that include internal models have been proposed; we focus herein on that referred to as the sensory weighting model. For simplicity, we isolate the portion of the sensory weighting model that estimates head angular velocity: it includes an inverse internal model of head kinematics and an 'idiotropic' vector aligned with the main body axis. Following a post-rotatory tilt in the dark, which is a rapid tilt following a constant-velocity rotation about an earth-vertical axis, the inverse internal model is applied to conflicting vestibular signals. Consequently, the CNS computes an inaccurate estimate of head angular velocity that shifts toward alignment with an estimate of gravity. Since reflexive eye movements known as vestibulo-ocular reflexes (VOR) compensate for this estimate of head angular velocity, the model predicts that the VOR rotation axis shifts toward alignment with this estimate of gravity and that the VOR time constant depends on final head orientation. These predictions are consistent with experimental data. PMID:16135883

  8. Anatomical segregation of different adaptative processes within the vestibulocerebellum of the cat.

    PubMed

    Torte, M P; Courjon, J H; Flandrin, J M; Magnin, M; Magenes, G

    1994-01-01

    Bilateral surgical lesions of the flocculus or the nodulo-uvular lobes were performed in the cat. Effects of these lesions on optokinetic and optokinetic afternystagmus OKAN), vestibulo-ocular reflex (VOR), visual suppression, and adaptation and habituation of VOR were studied using an identical experimental protocol. After flocculectomy, all these functions were impaired, except for habituation. Long-term postoperative recordings only revealed a recovery of the suppression of VOR, suggesting a limited contribution of the flocculus to this function. After nodulo-uvulectomy, only habituation and OKAN were modified. When the lesion was restricted to part of the uvula, OKAN duration was decreased. For other lesions involving the uvula together with the nodulus and/or the lobules VII-VIII,OKAN duration was increased. Habituation was lost after destruction of the nodulo-uvular lobes. When this latter structure was damaged, the retention component of habituation was selectively impaired, sparing the acquisition. Additional lesions outside the vestibulocerebellum appeared necessary to suppress the two components. Comparison of results obtained after flocculectomy and after nodulouvulectomy confirms and extends to non-primate species the concept of a "differential control" of adaptation and habituation by distinct vestibulocerebellar structures. PMID:7957724

  9. Gravity-specific adaptation of the angular vestibuloocular reflex: dependence on head orientation with regard to gravity.

    PubMed

    Yakushin, Sergei B; Raphan, Theodore; Cohen, Bernard

    2003-01-01

    The gain of the vertical angular vestibuloocular reflex (aVOR) was adaptively altered by visual-vestibular mismatch during rotation about an interaural axis, using steps of velocity in three head orientations: upright, left-side down, and right-side down. Gains were decreased by rotating the animal and visual surround in the same direction and increased by visual and surround rotation in opposite directions. Gains were adapted in one head position (single-state adaptation) or decreased with one side down and increased with the other side down (dual-state adaptation). Animals were tested in darkness using sinusoidal rotation at 0.5 Hz about an interaural axis that was tilted from horizontal to vertical. They were also sinusoidally oscillated from 0.5 to 4 Hz about a spatial vertical axis in static tilt positions from yaw to pitch. After both single- and dual-state adaptation, gain changes were maximal when the monkeys were in the position in which the gain had been adapted, and the gain changes progressively declined as the head was tilted away from that position. We call this gravity-specific aVOR gain adaptation. The spatial distribution of the specific aVOR gain changes could be represented by a cosine function that was superimposed on a bias level, which we called gravity-independent gain adaptation. Maximal gravity-specific gain changes were produced by 2-4 h of adaptation for both single- and dual-state adaptations, and changes in gain were similar at all test frequencies. When adapted while upright, the magnitude and distribution of the gravity-specific adaptation was comparable to that when animals were adapted in side-down positions. Single-state adaptation also produced gain changes that were independent of head position re gravity particularly in association with gain reduction. There was no bias after dual-state adaptation. With this difference, fits to data obtained by altering the gain in separate sessions predicted the modulations in gain obtained

  10. Genotype-phenotype complexity of the TR46/Y121F/T289A cyp51A azole resistance mechanism in Aspergillus fumigatus.

    PubMed

    Snelders, Eveline; Camps, Simone M T; Karawajczyk, Anna; Rijs, Antonius J M M; Zoll, Jan; Verweij, Paul E; Melchers, Willem J G

    2015-09-01

    The Aspergillus fumigatus cyp51A gene TR46/Y121F/T289A mutation is a new emerging resistance mechanism with high-level voriconazole (VOR) resistance, and elevated MICs to all other medical azoles. This is highly worrisome as VOR is the primary drug for the treatment of many aspergillus diseases. The 46 base pair tandem repeat (TR46) is positioned at the same location of the cyp51A gene promoter region as has been described for other tandem repeats. The exact role of the TR46 in combination with the two amino acid changes (Y121F and T289A) in the CYP51A protein is unknown. In this study this azole resistance mechanism was investigated by recombinant analysis study combined with homology modelling. MICs of the TR46/Y121F/T289A recombinant corresponded to the MICs of the original clinical isolates containing the same mutations with high-level resistance to VOR. The TR46 or Y121F by itself has only a moderate effect on azole susceptibility. The combination of TR46/Y121F, however, appears to be highly resistant not only for VOR but also for itraconazole (ITZ). The genetic change of T289A in combination with TR46 or by itself has no significant effect on the phenotype but moderates the phenotype of the ITZ resistance only in the presence of Y121F. The striking resistant phenotype of the TR46/Y121F mutant is supported by the structural analysis of the CYP51A homology model. The A. fumigatus CYP51A Y121 residue forms an H-bond with the heme centre of the enzyme. Disruption of the H-bond by the Y121F substitution destabilizes the active centre of CYP51A which appears to be essential with respect to azole resistance. In CYP51A-azole complexes, residue T289 is in close proximity of the azole moiety of VOR. Replacement of the polar amino acid threonine by the more hydrophobic amino acid alanine might promote more stable drug-protein interactions and has thereby an impact on ITZ susceptibility, which is confirmed by the MICs of the genetic recombinants. PMID:26092193

  11. Constraints of subducted slab geometries on trench migration and subduction velocities: flat slabs and slab curtains in the mantle under Asia

    NASA Astrophysics Data System (ADS)

    Wu, J. E.; Suppe, J.; Renqi, L.; Lin, C.; Kanda, R. V.

    2013-12-01

    The past locations, shapes and polarity of subduction trenches provide first-order constraints for plate tectonic reconstructions. Analogue and numerical models of subduction zones suggest that relative subducting (Vs) and overriding (Vor) plate velocities may strongly influence final subducted slab geometries. Here we have mapped the 3D geometries of subducted slabs in the upper and lower mantle of Asia from global seismic tomography. We have incorporated these slabs into plate tectonic models, which allows us to infer the subducting and overriding plate velocities. We describe two distinct slab geometry styles, ';flat slabs' and ';slab curtains', and show their implications for paleo-trench positions and subduction geometries in plate tectonic reconstructions. When compared to analogue and numerical models, the mapped slab styles show similarities to modeled slabs that occupy very different locations within Vs:Vor parameter space. ';Flat slabs' include large swaths of sub-horizontal slabs in the lower mantle that underlie the well-known northward paths of India and Australia from Eastern Gondwana, viewed in a moving hotspot reference. At India the flat slabs account for a significant proportion of the predicted lost Ceno-Tethys Ocean since ~100 Ma, whereas at Australia they record the existence of a major 8000km by 2500-3000km ocean that existed at ~43 Ma between East Asia, the Pacific and Australia. Plate reconstructions incorporating the slab constraints imply these flat slab geometries were generated when continent overran oceanic lithosphere to produce rapid trench retreat, or in other words, when subducting and overriding velocities were equal (i.e. Vs ~ Vor). ';Slab curtains' include subvertical Pacific slabs near the Izu-Bonin and Marianas trenches that extend from the surface down to 1500 km in the lower mantle and are 400 to 500 km thick. Reconstructed slab lengths were assessed from tomographic volumes calculated at serial cross-sections. The ';slab

  12. Bilateral vestibulopathy.

    PubMed

    Strupp, M; Feil, K; Dieterich, M; Brandt, T

    2016-01-01

    The leading symptoms of bilateral vestibulopathy (BVP) are postural imbalance and unsteadiness of gait that worsens in darkness and on uneven ground. There are typically no symptoms while sitting or lying under static conditions. A minority of patients also have movement-induced oscillopsia, in particular while walking. The diagnosis of BVP is based on a bilaterally reduced or absent function of the vestibulo-ocular reflex (VOR). This deficit is diagnosed for the high-frequency range of the angular VOR by a bilaterally pathologic bedside head impulse test (HIT) and for the low-frequency range by a bilaterally reduced or absent caloric response. If the results of the bedside HIT are unclear, angular VOR function should be quantified by a video-oculography system (vHIT). An additional test supporting the diagnosis is dynamic visual acuity. Cervical and ocular vestibular-evoked myogenic potentials (c/oVEMP) may also be reduced or absent, indicating impaired otolith function. There are different subtypes of BVP depending on the affected anatomic structure and frequency range of the VOR deficit: impaired canal function in the low- and/or high-frequency VOR range only and/or otolith function only; the latter is very rare. The etiology of BVP remains unclear in more than 50% of patients: in these cases neurodegeneration is assumed. Frequent known causes are ototoxicity mainly due to gentamicin, bilateral Menière's disease, autoimmune diseases, meningitis and bilateral vestibular schwannoma, as well as an association with cerebellar degeneration (cerebellar ataxia, neuropathy, vestibular areflexia syndrome=CANVAS). In general, in the long term there is no improvement of vestibular function. There are four treatment options: first, detailed patient counseling to explain the cause, etiology, and consequences, as well as the course of the disease; second, daily vestibular exercises and balance training; third, if possible, treatment of the underlying cause, as in bilateral

  13. Thoracic cavity segmentation algorithm using multiorgan extraction and surface fitting in volumetric CT

    SciTech Connect

    Bae, JangPyo; Kim, Namkug Lee, Sang Min; Seo, Joon Beom; Kim, Hee Chan

    2014-04-15

    Purpose: To develop and validate a semiautomatic segmentation method for thoracic cavity volumetry and mediastinum fat quantification of patients with chronic obstructive pulmonary disease. Methods: The thoracic cavity region was separated by segmenting multiorgans, namely, the rib, lung, heart, and diaphragm. To encompass various lung disease-induced variations, the inner thoracic wall and diaphragm were modeled by using a three-dimensional surface-fitting method. To improve the accuracy of the diaphragm surface model, the heart and its surrounding tissue were segmented by a two-stage level set method using a shape prior. To assess the accuracy of the proposed algorithm, the algorithm results of 50 patients were compared to the manual segmentation results of two experts with more than 5 years of experience (these manual results were confirmed by an expert thoracic radiologist). The proposed method was also compared to three state-of-the-art segmentation methods. The metrics used to evaluate segmentation accuracy were volumetric overlap ratio (VOR), false positive ratio on VOR (FPRV), false negative ratio on VOR (FNRV), average symmetric absolute surface distance (ASASD), average symmetric squared surface distance (ASSSD), and maximum symmetric surface distance (MSSD). Results: In terms of thoracic cavity volumetry, the mean ± SD VOR, FPRV, and FNRV of the proposed method were (98.17 ± 0.84)%, (0.49 ± 0.23)%, and (1.34 ± 0.83)%, respectively. The ASASD, ASSSD, and MSSD for the thoracic wall were 0.28 ± 0.12, 1.28 ± 0.53, and 23.91 ± 7.64 mm, respectively. The ASASD, ASSSD, and MSSD for the diaphragm surface were 1.73 ± 0.91, 3.92 ± 1.68, and 27.80 ± 10.63 mm, respectively. The proposed method performed significantly better than the other three methods in terms of VOR, ASASD, and ASSSD. Conclusions: The proposed semiautomatic thoracic cavity segmentation method, which extracts multiple organs (namely, the rib, thoracic wall, diaphragm, and heart

  14. Predictive mechanisms of head-eye coordination and vestibulo-ocular reflex suppression in humans.

    PubMed

    Barnes, G R; Grealy, M A

    1992-01-01

    Head and eye movements of human subjects have been recorded during head-free pursuit in the horizontal plane of a target executing sinusoidal motion at a frequency of 0.26 to 0.78 Hz and a peak velocity of +/- 96 degrees/s. The target was not presented continuously but was exposed for brief durations of 120 to 320 ms as it passed through the centre of the visual field at peak velocity. This technique allowed the timing of each response to be assessed in relation to the onset of target appearance. During the first 3 to 4 target presentations, there was a progressive buildup of both head velocity and the smooth component of gaze velocity, while, simultaneously, the responses became more phase-advanced with respect to target onset. In the steady state, similar temporal response trajectories were observed for head and gaze velocity, which were initiated approximately 500 ms prior to target onset, rose to a peak that increased with the duration of target exposure, and then decayed with a time constant of 0.5 to 1 s. Whenever the target failed to appear as expected, the gaze and head velocity trajectories continued to be made, indicating that predictive suppression of the vestibulo-ocular reflex (VOR) was taking place in darkness. In a further experiment, subjects attempted to suppress the VOR during whole body oscillation at 0.2 or 0.4 Hz on a turntable by fixating a head-fixed target that appeared for 10 to 160 ms at the time of peak head velocity. Again, VOR suppression was initiated prior to target appearance in the same manner as for natural head movements, and when the target suddenly disappeared but rotation continued, predictive VOR suppression was observed in darkness. The similarity of these predictive effects to those obtained previously for head-fixed pursuit provides further support for the hypothesis that both pursuit and visual suppression of the VOR are controlled primarily by identical visual feedback mechanisms. PMID:1342395

  15. Horizontal vestibuloocular reflex evoked by high-acceleration rotations in the squirrel monkey. II. Responses after canal plugging

    NASA Technical Reports Server (NTRS)

    Lasker, D. M.; Backous, D. D.; Lysakowski, A.; Davis, G. L.; Minor, L. B.

    1999-01-01

    The horizontal angular vestibuloocular reflex (VOR) evoked by high-frequency, high-acceleration rotations was studied in four squirrel monkeys after unilateral plugging of the three semicircular canals. During the period (1-4 days) that animals were kept in darkness after plugging, the gain during steps of acceleration (3, 000 degrees /s(2), peak velocity = 150 degrees /s) was 0.61 +/- 0.14 (mean +/- SD) for contralesional rotations and 0.33 +/- 0.03 for ipsilesional rotations. Within 18-24 h after animals were returned to light, the VOR gain for contralesional rotations increased to 0. 88 +/- 0.05, whereas there was only a slight increase in the gain for ipsilesional rotations to 0.37 +/- 0.07. A symmetrical increase in the gain measured at the plateau of head velocity was noted after animals were returned to light. The latency of the VOR was 8.2 +/- 0. 4 ms for ipsilesional and 7.1 +/- 0.3 ms for contralesional rotations. The VOR evoked by sinusoidal rotations of 0.5-15 Hz, +/-20 degrees /s had no significant half-cycle asymmetries. The recovery of gain for these responses after plugging was greater at lower than at higher frequencies. Responses to rotations at higher velocities for frequencies >/=4 Hz showed an increase in contralesional half-cycle gain, whereas ipsilesional half-cycle gain was unchanged. A residual response that appeared to be canal and not otolith mediated was noted after plugging of all six semicircular canals. This response increased with frequency to reach a gain of 0.23 +/- 0.03 at 15 Hz, resembling that predicted based on a reduction of the dominant time constant of the canal to 32 ms after plugging. A model incorporating linear and nonlinear pathways was used to simulate the data. The coefficients of this model were determined from data in animals with intact vestibular function. Selective increases in the gain for the linear and nonlinear pathways predicted the changes in recovery observed after canal plugging. An increase in gain of

  16. Opioid-Induced Nausea Involves a Vestibular Problem Preventable by Head-Rest

    PubMed Central

    Sağlam, Murat; Schulz, Christian M.; Wagner, Klaus J.; Taki, Masakatsu; Kochs, Eberhard F.; Jahn, Klaus; Brandt, Thomas; Glasauer, Stefan; Schneider, Erich

    2015-01-01

    Background and Aims Opioids are indispensable for pain treatment but may cause serious nausea and vomiting. The mechanism leading to these complications is not clear. We investigated whether an opioid effect on the vestibular system resulting in corrupt head motion sensation is causative and, consequently, whether head-rest prevents nausea. Methods Thirty-six healthy men (26.6±4.3 years) received an opioid remifentanil infusion (45 min, 0.15 μg/kg/min). Outcome measures were the vestibulo-ocular reflex (VOR) gain determined by video-head-impulse-testing, and nausea. The first experiment (n = 10) assessed outcome measures at rest and after a series of five 1-Hz forward and backward head-trunk movements during one-time remifentanil administration. The second experiment (n = 10) determined outcome measures on two days in a controlled crossover design: (1) without movement and (2) with a series of five 1-Hz forward and backward head-trunk bends 30 min after remifentanil start. Nausea was psychophysically quantified (scale from 0 to 10). The third controlled crossover experiment (n = 16) assessed nausea (1) without movement and (2) with head movement; isolated head movements consisting of the three axes of rotation (pitch, roll, yaw) were imposed 20 times at a frequency of 1 Hz in a random, unpredictable order of each of the three axes. All movements were applied manually, passively with amplitudes of about ± 45 degrees. Results The VOR gain decreased during remifentanil administration (p<0.001), averaging 0.92±0.05 (mean±standard deviation) before, 0.60±0.12 with, and 0.91±0.05 after infusion. The average half-life of VOR recovery was 5.3±2.4 min. 32/36 subjects had no nausea at rest (nausea scale 0.00/0.00 median/interquartile range). Head-trunk and isolated head movement triggered nausea in 64% (p<0.01) with no difference between head-trunk and isolated head movements (nausea scale 4.00/7.25 and 1.00/4.5, respectively). Conclusions Remifentanil reversibly

  17. [Flexibility in the adaptation of the vestibulo-ocular reflex to modified visual inputs in humans].

    PubMed

    Hattori, K; Watanabe, S; Nakamura, T; Kato, I

    2000-10-01

    The vestibulo-ocular reflex (VOR) serves to stabilize images on the retina. To maintain appropriate performance and minimize image slippage throughout life, the VOR is subject to long-term adaptive regulation in response to visual input. Adaptive changes in VOR gain (eye velocity/head velocity) can be evoked either by fitting subjects with magnifying, miniaturizing, or reversing spectacles during normal behavior or by moving a large visual field in or out of phase relative to the subject's head movement. These changes exhibit frequency-selectivity. Here, we examine the flexibility of VOR gains by causing VOR in similar directions to undergo different behavioral gain changes. Nine healthy adults, ranging in age from 24 to 38 (mean 28.5) with no history of neurotological symptoms participated in the study. All subjects demonstrated clinically normal functioning on a screening battery of tests that included combined neurologic and otologic physical examinations. Horizontal and vertical eye positions were recorded by bitemporal DC coupled electrooculography (EOG). The subject sat in a rotating chair. The axis of rotation of the body was always earth-vertical, the interaural axis crossing the axis of rotation of the chair. The head was positioned at 20 degrees down in all experiments and was stabilized in this position using a chin rest. The chair was 78 cm in diameter and was shielded by a half-cylindrical optokinetic screen positioned in front of the subjects. Random dot patterns were projected onto this screen. During per- and post-adaptation periods, goggles were fitted to ensure that the subject was in complete darkness and the chair was rotated sinusoidally. The amplitude of the rotating chair was 30 degrees and 60 degrees. Frequencies of rotation were 0.1 Hz, 0.2 Hz, 0.3 Hz and 0.4 Hz for amplitudes of 30 degrees and 0.1 Hz, 0.2 Hz, and 0.3 Hz for amplitudes of 60 degrees. To induce VOR adaptation, the retinal slippage velocity caused by the visual input of a

  18. Progress Toward Development of a Multichannel Vestibular Prosthesis for Treatment of Bilateral Vestibular Deficiency

    PubMed Central

    FRIDMAN, GENE Y.; DELLA SANTINA, CHARLES C.

    2014-01-01

    This article reviews vestibular pathology and the requirements and progress made in the design and construction of a vestibular prosthesis. Bilateral loss of vestibular sensation is disabling. When vestibular hair cells are injured by ototoxic medications or other insults to the labyrinth, the resulting loss of sensory input disrupts vestibulo-ocular reflexes (VORs) and vestibulo-spinal reflexes that normally stabilize the eyes and body. Affected individuals suffer poor vision during head movement, postural instability, chronic disequilibrium, and cognitive distraction. Although most individuals with residual sensation compensate for their loss over time, others fail to do so and have no adequate treatment options. A vestibular prosthesis analogous to cochlear implants but designed to modulate vestibular nerve activity during head movement should improve quality of life for these chronically dizzy individuals. We describe the impact of bilateral loss of vestibular sensation, animal studies supporting feasibility of prosthetic vestibular stimulation, the current status of multichannel vestibular sensory replacement prosthesis development, and challenges to successfully realizing this approach in clinical practice. In bilaterally vestibular-deficient rodents and rhesus monkeys, the Johns Hopkins multichannel vestibular prosthesis (MVP) partially restores the three-dimensional (3D) VOR for head rotations about any axis. Attempts at prosthetic vestibular stimulation of humans have not yet included the 3D eye movement assays necessary to accurately evaluate VOR alignment, but these initial forays have revealed responses that are otherwise comparable to observations in animals. Current efforts now focus on refining electrode design and surgical technique to enhance stimulus selectivity and preserve cochlear function, optimizing stimulus protocols to improve dynamic range and reduce excitation–inhibition asymmetry, and adapting laboratory MVP prototypes into devices

  19. Getting ahead of oneself: anticipation and the vestibulo-ocular reflex.

    PubMed

    King, W M

    2013-04-16

    Compensatory counter-rotations of the eyes provoked by head turns are commonly attributed to the vestibulo-ocular reflex (VOR). A recent study in guinea pigs demonstrates, however, that this assumption is not always valid. During voluntary head turns, guinea pigs make highly accurate compensatory eye movements that occur with zero or even negative latencies with respect to the onset of the provoking head movements. Furthermore, the anticipatory eye movements occur in animals with bilateral peripheral vestibular lesions, thus confirming that they have an extra vestibular origin. This discovery suggests the possibility that anticipatory responses might also occur in other species including humans and non-human primates, but have been overlooked and mistakenly identified as being produced by the VOR. This review will compare primate and guinea pig vestibular physiology in light of these new findings. A unified model of vestibular and cerebellar pathways will be presented that is consistent with current data in primates and guinea pigs. The model is capable of accurately simulating compensatory eye movements to active head turns (anticipatory responses) and to passive head perturbations (VOR induced eye movements) in guinea pigs and in human subjects who use coordinated eye and head movements to shift gaze direction in space. Anticipatory responses provide new evidence and opportunities to study the role of extra vestibular signals in motor control and sensory-motor transformations. Exercises that employ voluntary head turns are frequently used to improve visual stability in patients with vestibular hypofunction. Thus, a deeper understanding of the origin and physiology of anticipatory responses could suggest new translational approaches to rehabilitative training of patients with bilateral vestibular loss.

  20. Yaw and pitch visual-vestibular interaction in weightlessness

    NASA Technical Reports Server (NTRS)

    Clement, G.; Wood, S. J.; Reschke, M. F.; Berthoz, A.; Igarashi, M.

    1999-01-01

    Both yaw and pitch visual-vestibular interactions at two separate frequencies of chair rotation (0.2 and 0.8 Hz) in combination with a single velocity of optokinetic stimulus (36 degrees/s) were used to investigate the effects of sustained weightlessness on neural strategies adopted by astronaut subjects to cope with the stimulus rearrangement of spaceflight. Pitch and yaw oscillation in darkness at 0.2 and 0.8 Hz without optokinetic stimulation, and constant velocity linear optokinetic stimulation at 18, 36, and 54 degrees/s presented relative to the head with the subject stationary, were used as controls for the visual-vestibular interactions. The results following 8 days of space flight showed no significant changes in: (1) either the horizontal and vertical vestibulo-ocular reflex (VOR) gain, phase, or bias; (2) the yaw visual-vestibular response (VVR); or (3) the horizontal or vertical optokinetic (OKN) slow phase velocity (SPV). However, significant changes were observed: (1) when during pitch VVR at 0.2 Hz late inflight, the contribution of the optokinetic input to the combined oculomotor response was smaller than during the stationary OKN SPV measurements, followed by an increased contribution during the immediate postflight testing; and (2) when during pitch VVR at 0.8 Hz, the component of the combined oculomotor response due to the underlying vertical VOR was more efficiently suppressed early inflight and less suppressed immediately postflight compared with preflight observations. The larger OKN response during pitch VVR at 0.2 Hz and the better suppression of VOR during pitch VVR at 0.8 Hz postflight are presumably due to the increased role of vision early inflight and immediately after spaceflight, as previously observed in various studies. These results suggest that the subjects adopted a neural strategy to structure their spatial orientation in weightlessness by reweighting visual, otolith, and perhaps tactile/somatic signals.

  1. Prevalence of Vestibular Disorder in Older People Who Experience Dizziness

    PubMed Central

    Chau, Allan T.; Menant, Jasmine C.; Hübner, Patrick P.; Lord, Stephen R.; Migliaccio, Americo A.

    2015-01-01

    Dizziness and imbalance are clinically poorly defined terms, which affect ~30% of people over 65 years of age. In these people, it is often difficult to define the primary cause of dizziness, as it can stem from cardiovascular, vestibular, psychological, and neuromuscular causes. However, identification of the primary cause is vital in determining the most effective treatment strategy for a patient. Our aim is to accurately identify the prevalence of benign paroxysmal positional vertigo (BPPV), peripheral, and central vestibular hypofunction in people aged over 50 years who had experienced dizziness within the past year. Seventy-six participants aged 51–92 (mean ± SD = 69 ± 9.5 years) were tested using the head thrust dynamic visual acuity (htDVA) test, dizziness handicap inventory (DHI), as well as sinusoidal and unidirectional rotational chair testing, in order to obtain data for htDVA score, DHI score, sinusoidal (whole-body, 0.1–2 Hz with peak velocity at 30°/s) vestibulo-ocular reflex (VOR) gain and phase, transient (whole-body, acceleration at 150°/s2 to a constant velocity rotation of 50°/s) VOR gain and time constant (TC), optokinetic nystagmus (OKN) gain, and TC (whole-body, constant velocity rotation at 50°/s). We found that BPPV, peripheral and central vestibular hypofunction were present in 38 and 1% of participants, respectively, suggesting a likely vestibular cause of dizziness in these people. Of those with a likely vestibular cause, 63% had BPPV; a figure higher than previously reported in dizziness clinics of ~25%. Our results indicate that htDVA, sinusoidal (particularly 0.5–1 Hz), and transient VOR testing were the most effective at detecting people with BPPV or vestibular hypofunction, whereas DHI and OKN were effective at only detecting non-BPPV vestibular hypofunction. PMID:26733940

  2. Contribution of the cerebellar flocculus to gaze control during active head movements

    NASA Technical Reports Server (NTRS)

    Belton, T.; McCrea, R. A.; Peterson, B. W. (Principal Investigator)

    1999-01-01

    The flocculus and ventral paraflocculus are adjacent regions of the cerebellar cortex that are essential for controlling smooth pursuit eye movements and for altering the performance of the vestibulo-ocular reflex (VOR). The question addressed in this study is whether these regions of the cerebellum are more globally involved in controlling gaze, regardless of whether eye or active head movements are used to pursue moving visual targets. Single-unit recordings were obtained from Purkinje (Pk) cells in the floccular region of squirrel monkeys that were trained to fixate and pursue small visual targets. Cell firing rate was recorded during smooth pursuit eye movements, cancellation of the VOR, combined eye-head pursuit, and spontaneous gaze shifts in the absence of targets. Pk cells were found to be much less sensitive to gaze velocity during combined eye-head pursuit than during ocular pursuit. They were not sensitive to gaze or head velocity during gaze saccades. Temporary inactivation of the floccular region by muscimol injection compromised ocular pursuit but had little effect on the ability of monkeys to pursue visual targets with head movements or to cancel the VOR during active head movements. Thus the signals produced by Pk cells in the floccular region are necessary for controlling smooth pursuit eye movements but not for coordinating gaze during active head movements. The results imply that individual functional modules in the cerebellar cortex are less involved in the global organization and coordination of movements than with parametric control of movements produced by a specific part of the body.

  3. Age-Related Neurochemical Changes in the Vestibular Nuclei.

    PubMed

    Smith, Paul F

    2016-01-01

    There is evidence that the normal aging process is associated with impaired vestibulo-ocular reflexes (VOR) and vestibulo-spinal reflexes, causing reduced visual acuity and postural instability. Nonetheless, the available evidence is not entirely consistent, especially with respect to the VOR. Some recent studies have reported that VOR gain can be intact even above 80 years of age. Similarly, although there is evidence for age-related hair cell loss and neuronal loss in Scarpa's ganglion and the vestibular nucleus complex (VNC), it is not entirely consistent. Whatever structural and functional changes occur in the VNC as a result of aging, either to cause vestibular impairment or to compensate for it, neurochemical changes must underlie them. However, the neurochemical changes that occur in the VNC with aging are poorly understood because the available literature is very limited. This review summarizes and critically evaluates the available evidence relating to the noradrenaline, serotonin, dopamine, glutamate, GABA, glycine, and nitric oxide neurotransmitter systems in the aging VNC. It is concluded that, at present, it is difficult, if not impossible, to relate the neurochemical changes observed to the function of specific VNC neurons and whether the observed changes are the cause of a functional deficit in the VNC or an effect of it. A better understanding of the neurochemical changes that occur during aging may be important for the development of potential drug treatments for age-related vestibular disorders. However, this will require the use of more sophisticated methodology such as in vivo microdialysis with single neuron recording and perhaps new technologies such as optogenetics. PMID:26973593

  4. Prevalence of Vestibular Disorder in Older People Who Experience Dizziness.

    PubMed

    Chau, Allan T; Menant, Jasmine C; Hübner, Patrick P; Lord, Stephen R; Migliaccio, Americo A

    2015-01-01

    Dizziness and imbalance are clinically poorly defined terms, which affect ~30% of people over 65 years of age. In these people, it is often difficult to define the primary cause of dizziness, as it can stem from cardiovascular, vestibular, psychological, and neuromuscular causes. However, identification of the primary cause is vital in determining the most effective treatment strategy for a patient. Our aim is to accurately identify the prevalence of benign paroxysmal positional vertigo (BPPV), peripheral, and central vestibular hypofunction in people aged over 50 years who had experienced dizziness within the past year. Seventy-six participants aged 51-92 (mean ± SD = 69 ± 9.5 years) were tested using the head thrust dynamic visual acuity (htDVA) test, dizziness handicap inventory (DHI), as well as sinusoidal and unidirectional rotational chair testing, in order to obtain data for htDVA score, DHI score, sinusoidal (whole-body, 0.1-2 Hz with peak velocity at 30°/s) vestibulo-ocular reflex (VOR) gain and phase, transient (whole-body, acceleration at 150°/s(2) to a constant velocity rotation of 50°/s) VOR gain and time constant (TC), optokinetic nystagmus (OKN) gain, and TC (whole-body, constant velocity rotation at 50°/s). We found that BPPV, peripheral and central vestibular hypofunction were present in 38 and 1% of participants, respectively, suggesting a likely vestibular cause of dizziness in these people. Of those with a likely vestibular cause, 63% had BPPV; a figure higher than previously reported in dizziness clinics of ~25%. Our results indicate that htDVA, sinusoidal (particularly 0.5-1 Hz), and transient VOR testing were the most effective at detecting people with BPPV or vestibular hypofunction, whereas DHI and OKN were effective at only detecting non-BPPV vestibular hypofunction. PMID:26733940

  5. Vestibulo-spinal and vestibulo-ocular reflexes are modulated when standing with increased postural threat.

    PubMed

    Naranjo, E N; Cleworth, T W; Allum, J H J; Inglis, J T; Lea, J; Westerberg, B D; Carpenter, M G

    2016-02-01

    We investigated how vestibulo-spinal reflexes (VSRs) and vestibulo-ocular reflexes (VORs) measured through vestibular evoked myogenic potentials (VEMPs) and video head impulse test (vHIT) outcomes, respectively, are modulated during standing under conditions of increased postural threat. Twenty-five healthy young adults stood quietly at low (0.8 m from the ground) and high (3.2 m) surface height conditions in two experiments. For the first experiment (n = 25) VEMPs were recorded with surface EMG from inferior oblique (IO), sternocleidomastoid (SCM), trapezius (TRP), and soleus (SOL) muscles in response to 256 air-conducted short tone bursts (125 dB SPL, 500 Hz, 4 ms) delivered via headphones. A subset of subjects (n = 19) also received horizontal and vertical head thrusts (∼150°/s) at each height in a separate session, comparing eye and head velocities by using a vHIT system for calculating the functional VOR gains. VEMP amplitudes (IO, TRP, SOL) and horizontal and vertical vHIT gains all increased with high surface height conditions (P < 0.05). Changes in IO and SCM VEMP amplitudes as well as horizontal vHIT gains were correlated with changes in electrodermal activity (ρ = 0.44-0.59, P < 0.05). VEMP amplitude for the IO also positively correlated with fear (ρ = 0.43, P = 0.03). Threat-induced anxiety, fear, and arousal have significant effects on VSR and VOR gains that can be observed in both physiological and functional outcome measures. These findings provide support for a potential central modulation of the vestibular nucleus complex through excitatory inputs from neural centers involved in processing fear, anxiety, arousal, and vigilance. PMID:26631147

  6. Eye movements of the murine P/Q calcium channel mutant tottering, and the impact of aging.

    PubMed

    Stahl, John S; James, Robert A; Oommen, Brian S; Hoebeek, Freek E; De Zeeuw, Chris I

    2006-03-01

    Mice carrying mutations of the gene encoding the ion pore of the P/Q calcium channel (Cacna1a) are an instance in which cerebellar dysfunction may be attributable to altered electrophysiology and thus provide an opportunity to study how neuronal intrinsic properties dictate signal processing in the ocular motor system. P/Q channel mutations can engender multiple effects at the single neuron, circuit, and behavioral levels; correlating physiological and behavioral abnormalities in multiple allelic strains will ultimately facilitate determining which alterations of physiology are responsible for specific behavioral aberrations. We used videooculography to quantify ocular motor behavior in tottering mutants aged 3 mo to 2 yr and compared their performance to data previously obtained in the allelic mutant rocker and C57BL/6 controls. Tottering mutants shared numerous abnormalities with rocker, including upward deviation of the eyes at rest, increased vestibuloocular reflex (VOR) phase lead at low stimulus frequencies, reduced VOR gain at high stimulus frequencies, reduced gain of the horizontal and vertical optokinetic reflex, reduced time constants of the neural integrator, and reduced plasticity of the VOR as assessed in a cross-axis training paradigm. Unlike rocker, young tottering mutants exhibited normal peak velocities of nystagmus fast phases, arguing against a role for neuromuscular transmission defects in the attenuation of compensatory eye movements. Tottering also differed by exhibiting directional asymmetries of the gains of optokinetic reflexes. The data suggest at least four pathophysiological mechanisms (two congenital and two acquired) are required to explain the ocular motor deficits in the two Cacna1a mutant strains.

  7. Investigations of the pathogenesis of acquired pendular nystagmus

    NASA Technical Reports Server (NTRS)

    Averbuch-Heller, L.; Zivotofsky, A. Z.; Das, V. E.; DiScenna, A. O.; Leigh, R. J.

    1995-01-01

    We investigated the pathogenesis of acquired pendular nystagmus (APN) in six patients, three of whom had multiple sclerosis. First, we tested the hypothesis that the oscillations of APN are due to a delay in visual feedback secondary, for example, to demyelination of the optic nerves. We manipulated the latency to onset of visually guided eye movements using an electronic technique that induces sinusoidal oscillations in normal subjects. This manipulation did not change the characteristics of the APN, but did superimpose lower-frequency oscillations similar to those induced in normal subjects. These results are consistent with current models for smooth (non-saccadic) eye movements, which predict that prolongation of visual feedback could not account for the high-frequency oscillations that often characterize APN. Secondly, we attempted to determine whether an increase in the gain of the visually-enhanced vestibulo-ocular reflex (VOR), produced by viewing a near target, was accompanied by a commensurate increase in the amplitude of APN. Increases in horizontal or vertical VOR gain during near viewing occurred in four patients, but only two of them showed a parallel increase in APN amplitude. On the other hand, APN amplitude decreased during viewing of the near target in the two patients who showed no change in VOR gain. Taken together, these data suggest that neither delayed visual feedback nor a disorder of central vestibular mechanisms is primarily responsible for APN. More likely, these ocular oscillations are produced by abnormalities of internal feedback circuits, such as the reciprocal connections between brainstem nuclei and cerebellum.

  8. Comparison of Predictable Smooth Ocular and Combined Eye-Head Tracking Behaviour in Patients with Lesions Affecting the Brainstem and Cerebellum

    NASA Technical Reports Server (NTRS)

    Grant, Michael P.; Leigh, R. John; Seidman, Scott H.; Riley, David E.; Hanna, Joseph P.

    1992-01-01

    We compared the ability of eight normal subjects and 15 patients with brainstem or cerebellar disease to follow a moving visual stimulus smoothly with either the eyes alone or with combined eye-head tracking. The visual stimulus was either a laser spot (horizontal and vertical planes) or a large rotating disc (torsional plane), which moved at one sinusoidal frequency for each subject. The visually enhanced Vestibulo-Ocular Reflex (VOR) was also measured in each plane. In the horizontal and vertical planes, we found that if tracking gain (gaze velocity/target velocity) for smooth pursuit was close to 1, the gain of combined eye-hand tracking was similar. If the tracking gain during smooth pursuit was less than about 0.7, combined eye-head tracking was usually superior. Most patients, irrespective of diagnosis, showed combined eye-head tracking that was superior to smooth pursuit; only two patients showed the converse. In the torsional plane, in which optokinetic responses were weak, combined eye-head tracking was much superior, and this was the case in both subjects and patients. We found that a linear model, in which an internal ocular tracking signal cancelled the VOR, could account for our findings in most normal subjects in the horizontal and vertical planes, but not in the torsional plane. The model failed to account for tracking behaviour in most patients in any plane, and suggested that the brain may use additional mechanisms to reduce the internal gain of the VOR during combined eye-head tracking. Our results confirm that certain patients who show impairment of smooth-pursuit eye movements preserve their ability to smoothly track a moving target with combined eye-head tracking.

  9. Binocular Coordination of the Human Vestibulo-Ocular Reflex during Off-axis Pitch Rotation

    NASA Technical Reports Server (NTRS)

    Wood, S. J.; Reschke, M. F.; Kaufman, G. D.; Black, F. O.; Paloski, W. H.

    2006-01-01

    Head movements in the sagittal pitch plane typically involve off-axis rotation requiring both vertical and horizontal vergence ocular reflexes to compensate for angular and translational motion relative to visual targets of interest. The purpose of this study was to compare passive pitch VOR responses during rotation about an Earth-vertical axis (canal only cues) with off-axis rotation (canal and otolith cues). Methods. Eleven human subjects were oscillated sinusoidally at 0.13, 0.3 and 0.56 Hz while lying left-side down with the interaural axis either aligned with the axis of rotation or offset by 50 cm. In a second set of measurements, twelve subjects were also tested during sinusoidally varying centrifugation over the same frequency range. The modulation of vertical and horizontal vergence ocular responses was measured with a binocular videography system. Results. Off-axis pitch rotation enhanced the vertical VOR at lower frequencies and enhanced the vergence VOR at higher frequencies. During sinusoidally varying centrifugation, the opposite trend was observed for vergence, with both vertical and vergence vestibulo-ocular reflexes being suppressed at the highest frequency. Discussion. These differential effects of off-axis rotation over the 0.13 to 0.56 Hz range are consistent with the hypothesis that otolith-ocular reflexes are segregated in part on the basis of stimulus frequency. At the lower frequencies, tilt otolith-ocular responses compensate for declining canal input. At higher frequencies, translational otolith-ocular reflexes compensate for declining visual contributions to the kinematic demands required for fixating near targets.

  10. Effects of spaceflight on ocular counterrolling and the spatial orientation of the vestibular system

    NASA Technical Reports Server (NTRS)

    Dai, M.; McGarvie, L.; Kozlovskaya, I.; Raphan, T.; Cohen, B.

    1994-01-01

    We recorded the horizontal (yaw), vertical (pitch), and torsional (roll) eye movements of two rhesus monkeys with scleral search coils before and after the COSMOS Biosatellite 2229 Flight. The aim was to determine effects of adaptation to microgravity on the vestibulo-ocular reflex (VOR). The animals flew for 11 days. The first postflight tests were 22 h and 55 h after landing, and testing extended for 11 days after reentry. There were four significant effects of spaceflight on functions related to spatial orientation: (1) Compensatory ocular counterrolling (OCR) was reduced by about 70% for static and dynamic head tilts with regard to gravity. The reduction in OCR persisted in the two animals throughout postflight testing. (2) The gain of the torsional component of the angular VOR (roll VOR) was decreased by 15% and 50% in the two animals over the same period. (3) An up-down asymmetry of nystagmus, present in the two monkeys before flight was reduced after exposure to microgravity. (4) The spatial orientation of velocity storage was shifted in the one monkey that could be tested soon after flight. Before flight, the yaw axis eigenvector of optokinetic afternystagmus was close to gravity when the animal was upright or tilted. After flight, the yaw orientation vector was shifted toward the body yaw axis. By 7 days after recovery, it had reverted to a gravitational orientation. We postulate that spaceflight causes changes in the vestibular system which reflect adaptation of spatial orientation from a gravitational to a body frame of reference. These changes are likely to play a role in the postural, locomotor, and gaze instability demonstrated on reentry after spaceflight.

  11. In Vitro Susceptibility and Trailing Growth Effect of Clinical Isolates of Candida Species to Azole Drugs

    PubMed Central

    Zomorodian, Kamiar; Bandegani, Azadeh; Mirhendi, Hossein; Pakshir, Keyvan; Alinejhad, Navvab; Poostforoush Fard, Ali

    2016-01-01

    Background: Emergence of resistance to respective antifungal drugs is a primary concern for the treatment of candidiasis. Hence, determining antifungal susceptibility of the isolated yeasts is of special importance for effective therapy. For this purpose, the clinical laboratory standard institute (CLSI) has introduced a broth microdilution method to determine minimum inhibitory concentration (MIC). However, the so-called “Trailing effect” phenomenon might sometimes pose ambiguity in the interpretation of the results. Objectives: The present study aimed to determine the in vitro susceptibility of clinical isolates of Candida against azoles and the frequency of the Trailing effect. Materials and Methods: A total of 193 Candida isolates were prospectively collected and identified through the polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) method. Using a broth microdilution test, according to the guidelines of CLSI M27-A3, antifungal susceptibilities of the isolated yeasts against Fluconazole (FLU), Itraconazole (ITR), Ketoconazole (KET) and Voriconazole (VOR) were assessed. Moreover, trailing growth was determined when a susceptible MIC was incubated for 24 hours, and turned into a resistant one after 48 hours of incubation. Results: Among the tested antifungal drugs in this study, the highest rate of resistance was observed against ITR (28.5%) followed by VOR (26.4%), FLU (20.8%) and KET (1.5%). The trailing effect was induced in 27 isolates (14.0%) by VOR, in 26 isolates (13.5%) by ITR, in 24 isolates (12.4%) by FLU, and in 19 isolates (9.8%) by KET. Conclusions: The monitoring of antifungal susceptibilities of Candida species isolated from clinical sources is highly recommended for the efficient management of patients. Moreover, the trailing effect should be taken into consideration once the interpretation of the results is intended. PMID:27127587

  12. Dynamic Visual Acuity: a Functionally Relevant Research Tool

    NASA Technical Reports Server (NTRS)

    Peters, Brian T.; Brady, Rachel A.; Miller, Chris A.; Mulavara, Ajitkumar P.; Wood, Scott J.; Cohen, Helen S.; Bloomberg, Jacob J.

    2010-01-01

    Coordinated movements between the eyes and head are required to maintain a stable retinal image during head and body motion. The vestibulo-ocular reflex (VOR) plays a significant role in this gaze control system that functions well for most daily activities. However, certain environmental conditions or interruptions in normal VOR function can lead to inadequate ocular compensation, resulting in oscillopsia, or blurred vision. It is therefore possible to use acuity to determine when the environmental conditions, VOR function, or the combination of the two is not conductive for maintaining clear vision. Over several years we have designed and tested several tests of dynamic visual acuity (DVA). Early tests used the difference between standing and walking acuity to assess decrements in the gaze stabilization system after spaceflight. Supporting ground-based studies measured the responses from patients with bilateral vestibular dysfunction and explored the effects of visual target viewing distance and gait cycle events on walking acuity. Results from these studies show that DVA is affected by spaceflight, is degraded in patients with vestibular dysfunction, changes with target distance, and is not consistent across the gait cycle. We have recently expanded our research to include studies in which seated subjects are translated or rotated passively. Preliminary results from this work indicate that gaze stabilization ability may differ between similar active and passive conditions, may change with age, and can be affected by the location of the visual target with respect to the axis of motion. Use of DVA as a diagnostic tool is becoming more popular but the functional nature of the acuity outcome measure also makes it ideal for identifying conditions that could lead to degraded vision. By doing so, steps can be taken to alter the problematic environments to improve the man-machine interface and optimize performance.

  13. Effect of Target Location on Dynamic Visual Acuity During Passive Horizontal Rotation

    NASA Technical Reports Server (NTRS)

    Appelbaum, Meghan; DeDios, Yiri; Kulecz, Walter; Peters, Brian; Wood, Scott

    2010-01-01

    The vestibulo-ocular reflex (VOR) generates eye rotation to compensate for potential retinal slip in the specific plane of head movement. Dynamic visual acuity (DVA) has been utilized as a functional measure of the VOR. The purpose of this study was to examine changes in accuracy and reaction time when performing a DVA task with targets offset from the plane of rotation, e.g. offset vertically during horizontal rotation. Visual acuity was measured in 12 healthy subjects as they moved a hand-held joystick to indicate the orientation of a computer-generated Landolt C "as quickly and accurately as possible." Acuity thresholds were established with optotypes presented centrally on a wall-mounted LCD screen at 1.3 m distance, first without motion (static condition) and then while oscillating at 0.8 Hz (DVA, peak velocity 60 deg/s). The effect of target location was then measured during horizontal rotation with the optotypes randomly presented in one of nine different locations on the screen (offset up to 10 deg). The optotype size (logMar 0, 0.2 or 0.4, corresponding to Snellen range 20/20 to 20/50) and presentation duration (150, 300 and 450 ms) were counter-balanced across five trials, each utilizing horizontal rotation at 0.8 Hz. Dynamic acuity was reduced relative to static acuity in 7 of 12 subjects by one step size. During the random target trials, both accuracy and reaction time improved proportional to optotype size. Accuracy and reaction time also improved between 150 ms and 300 ms presentation durations. The main finding was that both accuracy and reaction time varied as a function of target location, with greater performance decrements when acquiring vertical targets. We conclude that dynamic visual acuity varies with target location, with acuity optimized for targets in the plane of motion. Both reaction time and accuracy are functionally relevant DVA parameters of VOR function.

  14. Agitation during lipoplex formation improves the gene knockdown effect of siRNA.

    PubMed

    Barichello, Jose Mario; Kizuki, Shinji; Tagami, Tatsuaki; Asai, Tomohiro; Ishida, Tatsuhiro; Kikuchi, Hiroshi; Oku, Naoto; Kiwada, Hiroshi

    2011-05-30

    The successful delivery of therapeutic siRNA to the designated target cells and their availability at the intracellular site of action are crucial requirements for successful RNAi therapy. In the present study, we focused on the siRNA-lipoplex preparation procedure and its effect on the gene-knockdown efficiency of siRNA in vitro. Agitation (vortex-mixing) during siRNA-lipoplex (vor-LTsiR) preparation and its effect on the gene-knockdown efficiency of stably expressed cell GFP was investigated, and their efficiency was compared with that of spontaneously formed lipoplex (spo-LTsiR). A dramatic difference in size between lipoplexes was observed at the N/P ratio of 7.62 (siRNA dose of 30 nM), even though both lipoplexes were positively charged. With the siRNA dose of 30 nM, vor-LTsiR accomplished a 50% gene-knockdown, while spo-LTsiR managed a similar knockdown effect at the 120 nM level, suggesting that the preparation procedure remarkably affects the gene-knockdown efficacy of siRNA. The uptake of vor-LTsiR was mainly via clathrin-mediated endocytosis, whereas that of spo-LTsiR was via membrane fusion. In addition, by inhibiting clathrin-mediated endocytosis, the gene-knockdown efficiency was significantly lowered. The size of the lipoplex, promoted by the preparation procedure, is likely to define the entry pathway, resulting in an increased amount of siRNA internalized in cells and an enhanced gene-knockdown efficacy. The results of the present study definitively show that a proper siRNA-lipoplex preparation procedure makes a significant contribution to the efficiency of cellular uptake, and thereby, to the gene-knockdown efficiency of siRNA. PMID:21392562

  15. Age-Related Neurochemical Changes in the Vestibular Nuclei

    PubMed Central

    Smith, Paul F.

    2016-01-01

    There is evidence that the normal aging process is associated with impaired vestibulo-ocular reflexes (VOR) and vestibulo-spinal reflexes, causing reduced visual acuity and postural instability. Nonetheless, the available evidence is not entirely consistent, especially with respect to the VOR. Some recent studies have reported that VOR gain can be intact even above 80 years of age. Similarly, although there is evidence for age-related hair cell loss and neuronal loss in Scarpa’s ganglion and the vestibular nucleus complex (VNC), it is not entirely consistent. Whatever structural and functional changes occur in the VNC as a result of aging, either to cause vestibular impairment or to compensate for it, neurochemical changes must underlie them. However, the neurochemical changes that occur in the VNC with aging are poorly understood because the available literature is very limited. This review summarizes and critically evaluates the available evidence relating to the noradrenaline, serotonin, dopamine, glutamate, GABA, glycine, and nitric oxide neurotransmitter systems in the aging VNC. It is concluded that, at present, it is difficult, if not impossible, to relate the neurochemical changes observed to the function of specific VNC neurons and whether the observed changes are the cause of a functional deficit in the VNC or an effect of it. A better understanding of the neurochemical changes that occur during aging may be important for the development of potential drug treatments for age-related vestibular disorders. However, this will require the use of more sophisticated methodology such as in vivo microdialysis with single neuron recording and perhaps new technologies such as optogenetics. PMID:26973593

  16. Effects of body orientation and rotation axis on pitch visual-vestibular interaction

    NASA Technical Reports Server (NTRS)

    Clement, G.; Wood, S. J.; Lathan, C. E.; Peterka, R. J.; Reschke, M. F.

    1999-01-01

    Spatial transformations of the vestibular-optokinetic system must account for changes in head position with respect to gravity in order to produce compensatory oculomotor responses. The purpose of this experiment was to study the influence of gravity on the vestibulo-ocular reflex (VOR) in darkness and on visual-vestibular interaction in the pitch plane in human subjects using two different comparisons: (1) Earth-horizontal axis (EHA) rotation about an upright versus a supine body orientation, and (2) Earth-horizontal versus Earth-vertical (EVA) rotation axes. Visual-vestibular responses (VVR) were evaluated by measuring the slow phase velocity of nystagmus induced during sinusoidal motion of the body in the pitch plane (at 0.2 Hz and 0.8 Hz) combined with a constant-velocity vertical optokinetic stimulation (at +/- 36 degrees/s). The results showed no significant effect on the gain or phase of the VOR in darkness or on the VVR responses at 0.8 Hz between EHA upright and EHA supine body orientations. However, there was a downward shift in the VOR bias in darkness in the supine orientation. There were systematic changes in VOR and VVR between EHA and EVA for 0.2 Hz, including a reduced modulation gain, increased phase lead, and decreased bias during EVA rotation. The same trend was also observed at 0.8 Hz, but at a lesser extent, presumably due to the effects of eccentric rotation in our EVA condition and/or to the different canal input across frequencies. The change in the bias at 0.2 Hz between rotation in darkness and rotation with an optokinetic stimulus was greater than the optokinetic responses without rotation. During EHA, changes in head position relative to gravity preserve graviceptor input to the VVR regardless of body orientation. However, the modifications in VVR gain and phase when the rotation axis is aligned with gravity indicate that this graviceptive information is important for providing compensatory eye movements during visual

  17. Das menschliche Gehör und Grundlagen der Psychoakustik

    NASA Astrophysics Data System (ADS)

    Genuit, Klaus; Sottek, Roland

    Das menschliche Gehör ist ein äußerst komplexes Empfangs- und Signalverarbeitungssystem. Es ist als Schallanalysator in Leistungsfähigkeit und Vielseitigkeit von technisch-analytischen Verfahren nach wie vor unerreicht. Die Signalverarbeitung läuft auf Grundlage komplexer Prozesse ab, die in ihrer Gesamtheit bislang nicht vollständig erfasst sind. Verschiedene Modelle zur gehörgerechten Zeit- und Frequenzanalyse ahmen jene komplexen Prozesse und Verarbeitungsmechanismen nach, die im menschlichen Gehör vollzogen werden.

  18. MYXINOIDA, Schleimaale, Inger

    NASA Astrophysics Data System (ADS)

    Rieger, Gunde; Maier, Wolfgang

    Schleimaale leben in Bodennähe bzw. im Schlamm eingegraben in allen Ozeanen bis in 2500 m Tiefe, bevorzugt in mehr als 30 m Tiefe in küstennahen Bereichen der gemäßigten Breiten. Geringere Salinität und vor allem Wassertemperaturen über 20°C sind limitierende Faktoren für ihr Vorkommen, das sich daher in wärmeren Zonen auf größere Tiefen beschränkt. Auch vom East Pacific Rise ist seit kurzem eine neue Art der Gattung Eptatretus bekannt (S. 198).

  19. Revival of the dark core in scattered optical vortices

    NASA Astrophysics Data System (ADS)

    Reddy, Salla G.; Kumar, Ashok; Prabhakar, Shashi; Singh, R. P.

    2013-09-01

    We have experimentally observed the revival of the dark core in the far field intensity distribution in optical vor­ tices after scattering through rotating ground glass plate. The diameter and darkness of the core is independent of the speed of the rotating ground glass plate. They depend on the spot size and azimuthal index of the beam incident on it. This shows that the spatial coherence of the scattered light is independent of the speed of the rotating ground glass plate. Our experimental results are in good agreement with the numerical results based on the theory given by Wang, Cai and Korotkova (Opt. Exp. 17, 22366 (2009)).

  20. Videobasierte Systeme

    NASA Astrophysics Data System (ADS)

    Knoll, Peter

    Videosensoren spielen für Fahrerassistenz systeme eine zentrale Rolle, da sie die Interpretation visueller Informationen (Objektklassifikation) gezielt unterstützen. Im Heckbereich kann die Video sensorik in der einfachsten Variante die ultraschallbasierte Einparkhilfe bei Einpark- und Rangiervorgängen unterstützen. Beim Nachtsichtsystem NightVision wird das mit Infrarotlicht angestrahlte Umfeld vor dem Fahrzeug mit einer Frontkamera aufgenommen und im Fahrzeugcockpit auf einem Display dem Fahrer angezeigt (s. Nachtsichtsysteme). Andere Fahrerassistenzsysteme verarbeiten die Videosignale und generieren daraus gezielt Informationen, die für eigenständige Funktionen (z. B. Spurverlassenswarner) oder aber als Zusatzinformation für andere Funktionen ausgewertet werden (Sensordatenfusion).

  1. Ein stochastisches Modell zur Beschreibung von Signalen in digitalen Schaltungen basierend auf quadratischer Optimierung

    NASA Astrophysics Data System (ADS)

    Kleeberger, V. B.; Maier, P.; Schlichtmann, U.

    2013-07-01

    Die kontinuierlich fortschreitende Miniaturisierung in integrierten Schaltungen führt zu einem erhöhten Modellierungsbedarf verschiedenster Effekte, wie z.B. Alterung oder Stromverbrauch. Diese hängen von den auftretenden Signalen innerhalb der Schaltung ab, wodurch deren statistische Modellierung ein zentrales Problem darstellt. Dieser Beitrag stellt eine neue Methode zur stochastischen Signalmodellierung basierend auf quadratischer Optimierung vor. Die Methode wird mit Hilfe von realen Daten mit existierenden Ansätzen verglichen. Die Testergebnisse zeigen hierbei im vorgestellten Modell einen Genauigkeitszuwachs von bis zu einem Faktor 10 im Vergleich zu bereits existierenden Modellen.

  2. Unidirectional abnormal eye movement without gaze nystagmus - Report of a case.

    PubMed

    Mizuno, Masahiro; Shibasaki, Osamu; Shindo, Susumu; Ito, Akinori; Kase, Yasuhiro

    2016-06-01

    We report here a case with unidirectional abnormalities of smooth eye movements without gaze nystagmus. Abnormalities of eye movements were confined to unidirectional (leftward) horizontal pursuit and slow phase of OKN; however, horizontal VOR (slow phase of caloric nystagmus) and saccade were normal, and vertical eye movements were also normal. No lesions were detected in the central nervous system, and any history of drug intake was denied. Although the cause of the unidirectional abnormality in eye movement of this case is still not clear, a congenital origin seems to be the most probable. PMID:26386498

  3. Required distribution of noise sources for Green's function recovery in diffusive fields

    NASA Astrophysics Data System (ADS)

    Shamsalsadati, S.; Weiss, C. J.

    2011-12-01

    In the most general sense, noise is the part of the signal of little or no interest, due to a multitude of reasons such as operator error, imperfect instrumentation, experiment design, or inescapable background interference. Considering the latter, it has been shown that Green's function can be extracted from cross-correlation of the ambient, diffusive wavefields arising from background random noise sources. Pore pressure and low-frequency electromagnetic induction are two such examples of diffusive fields. In theory, applying Green's function method in geophysical exploration requires infinity of volumetrically distributed sources; however, in the real world the number of noise sources in an area is limited, and furthermore, unevenly distributed in time, space and spectral content. Hence, quantification of the requisite noise sources that enable us to calculate Green's function acceptably well remains an open research question. The purpose of this study is to find the area of noise sources that contribute most to the Green's function estimation in diffusive systems. We call such a region the Volume of Relevance (VoR). Our analysis builds upon recent work in 1D homogeneous system where it was shown that sources located between two receivers positions are the most important ones for the purpose of Green's function recovery. Our results confirm the previous finding but we also examine the effect of heterogeneity, dimensionality and receiver location in both 1D and 2D at a fixed frequency. We demonstrate that for receivers located symmetrically across an interface between regions of contrasting diffusivity, the VoR rapidly shifts from one side of the interface to the other, and back again, as receiver separation increases. We also demonstrate that where the receiver pair is located on the interface itself, the shifting is less rapid, and for moderate to high diffusivity contrasts, the VoR remains entirely on the more diffusive side. In addition, because classical

  4. Supraleitung und Interkontinentalraketen „On-line computing“ zwischen Militär, Industrie und Wissenschaft

    NASA Astrophysics Data System (ADS)

    Knolle, Johannes; Joas, Christian

    Der zweite Weltkrieg und der Kalte Krieg veränderten nicht nur das Verhältnis zwischen Militär, Industrie und Wissenschaft, sondern auch die wissenschaftliche Praxis von Physikern und anderen Wissenschaftlern. In den 1950er Jahren stellte die Entwicklung von Interkontinentalraketen die Auftragnehmer des Militärs in der Industrie vor komplexe Fragestellungen, zu deren Lösung sie auf die Expertise von Wissenschaftlern angewiesen waren. Industrieunternehmen gründeten eigene Forschungseinheiten zur Lösung technischer und wissenschaftlicher Probleme.

  5. Empirical Green's function estimation for lossy systems: analysis of the volume of relevance for the origin of ambient fluctuations

    NASA Astrophysics Data System (ADS)

    Shamsalsadati, Sharmin; Weiss, Chester J.

    2012-09-01

    From a theoretical perspective, perfect Green's function recovery in diffusive systems is based on cross-correlation of time-series measured at distinct locations arising from background fluctuations from an infinite set of uncorrelated sources, either naturally occurring or engineered. Clearly such a situation is impossible in practice, and a relevant question to ask, then, is how does an imperfect set of noise sources affect the quality of the resulting empirical Green's function (EGF)? We narrow down this broad question by exploring the effect of source location and make no distinction between whether the noise sources are natural or man made. Following the theory of EGF recovery, the only requirement is that the sources are uncorrelated and endowed with the same (or nearly so) frequency spectrum and amplitude. As such, our intuition suggests that noise sources proximal to the observation points are likely to contribute more to the Green's function estimate than distal ones. However, in what manner and over what spatial extent our intuition is less clear. Thus, in this short note we specifically ask the question, 'Where are the noise sources that contribute most to the Green's function estimate in heterogeneous, lossy systems?' We call such a region the volume of relevance (VoR). Our analysis builds upon recent work on 1-D homogeneous systems by examining the effect of heterogeneity, dimensionality and receiver location in both one and two dimensions. Following the strategy of previous work in the field, the analysis is conducted out of mathematical convenience in the frequency domain although we stress that the sources need not be monochromatic. We find that for receivers located symmetrically across an interface between regions of contrasting diffusivity, the VoR rapidly shifts from one side of the interface to the other, and back again, as receiver separation increases. For the case where the receiver pair is located on the interface itself, the shifting is

  6. Messung und Analyse

    NASA Astrophysics Data System (ADS)

    Bathelt, Hartmut; Scheinhardt, Michael; Sell, Hendrik; Sottek, Roland; Guidati, Sandro; Helfer, Martin

    Für die Beurteilung von Akustik und Fahrkomfort eines Fahrzeugs gilt in der Fahrzeugentwicklung immer noch der alte Grundsatz: "Der Kunde fährt nicht am Prüfstand, sondern auf der Straße“. Daher werden Gesamtbeurteilungen des Entwicklungsstandes und Konkurrenzvergleiche (Benchmarking) nach wie vor auf der Straße durchgeführt, meist auf ausgewählten Fahrbahnen am Prüfgelände oder im Rahmen der regelmäßigen Winter- und Sommererprobungen unter extremen Witterungsverhältnissen.

  7. "Agnatha", Kieferlose

    NASA Astrophysics Data System (ADS)

    Rieger, Gunde; Maier, Wolfgang

    An der Basis der Wirbeltiere standen kieferlose Organismen, vermutlich mit Kiemendarm und noch filtrierender Lebensweise. Ihre wenigen heute noch lebenden Nachkommen sind die Myxinoida (Schleimaale) und die Petromyzontida (Neunaugen). Beide Taxa sind nur Relikte einer Vielzahl und Vielfalt im frühen Paläozoikum (Ordovizium bis ins Devon: vor 470-355 Mio. Jahren). Fossil traten die beiden heute lebenden Gruppen bereits im Karbon bzw. im Oberdevon auf. Obwohl diese rezenten Formen hoch spezialisiert sind, ermöglichen sie — zusammen mit den fossilen kieferlosen Formen (früher "†Ostracodermata") — Struktur und Lebensweise der frühen Craniota in Umrissen zu erkennen.

  8. Adaptive Cruise Control (ACC)

    NASA Astrophysics Data System (ADS)

    Reif, Konrad

    Die adaptive Fahrgeschwindigkeitsregelung (ACC, Adaptive Cruise Control) ist eine Weiterentwicklung der konventionellen Fahrgeschwindigkeitsregelung, die eine konstante Fahrgeschwindigkeit einstellt. ACC überwacht mittels eines Radarsensors den Bereich vor dem Fahrzeug und passt die Geschwindigkeit den Gegebenheiten an. ACC reagiert auf langsamer vorausfahrende oder einscherende Fahrzeuge mit einer Reduzierung der Geschwindigkeit, sodass der vorgeschriebene Mindestabstand zum vorausfahrenden Fahrzeug nicht unterschritten wird. Hierzu greift ACC in Antrieb und Bremse ein. Sobald das vorausfahrende Fahrzeug beschleunigt oder die Spur verlässt, regelt ACC die Geschwindigkeit wieder auf die vorgegebene Sollgeschwindigkeit ein (Bild 1). ACC steht somit für eine Geschwindigkeitsregelung, die sich dem vorausfahrenden Verkehr anpasst.

  9. System for providing an integrated display of instantaneous information relative to aircraft attitude, heading, altitude, and horizontal situation

    NASA Technical Reports Server (NTRS)

    James, R. (Inventor)

    1981-01-01

    A display device is disclosed which is particularly suited for providing the pilot of an aircraft with combined inflight attitude, heading, altitude, and horizontal situation information previously available only by using two or three devices providing separate displays. The preferred embodiment combines a commonly used and commercially available flight director-type device for providing a display in combination with a miniature aircraft supported for angular displacement from a vertical orientation to indicate heading error, or heading offset, and an extended course deviation indicator bar which projects into juxtaposition with the miniature aircraft for providing a true picture of the aircraft's horizontal situation relative to a selective VOR, ILS, or MLS course.

  10. Beschallungstechnik, Beschallungsplanung und Simulation

    NASA Astrophysics Data System (ADS)

    Ahnert, Wolfgang; Goertz, Anselm

    Die primäre Aufgabe einer Lautsprecheranlage ist es, Musik, Sprache oder auch Signaltöne und Geräusche wiederzugeben. Diese können von einem Tonträger kommen (CD, Sprachspeicher), von einem anderen Ort übertragen (Zuspielung über Radio, TV, Telefon) oder vor Ort erzeugt werden. Letzteres umfasst Konzerte, Ansprachen, Durchsagen oder künstlerische Darbietungen, bei denen es meist darum geht, eine bereits vorhandene Quelle einer größeren oder weiter verteilten Anzahl von Personen zugänglich zu machen.

  11. Automatic Navaids Checkout System. [for space shuttle electronics

    NASA Technical Reports Server (NTRS)

    Belver, T. L.; Junk, W. S.

    1974-01-01

    An automatic Navaids Checkout System for use in Space Shuttle development is discussed. The groundwork leading to the development is presented, followed by a description of the hardware. Finally, system utilization including operator interface and system software is discussed. The Navaids Checkout System is extremely flexible with capability to handle different test articles with a minimum of hardware reconfiguration. Application software is written in a high level user-oriented test language. The checkout system has been in operation for approximately one year with capability to handle VOR, ILS, TACAN, ATC Radar Beacon, and UHF/VHF communications equipment.

  12. Computational Aeroacoustic Analysis of Slat Trailing-Edge Flow

    NASA Technical Reports Server (NTRS)

    Singer, Bart A.; Lockhard, David P.; Brentner, Kenneth S.; Khorrami, Mehdi R.; Berkman, Mert E.; Choudhari, Meelan

    2000-01-01

    An acoustic analysis based on the Ffowcs Williams and Hawkings equation was performed for a high-lift system. As input, the acoustic analysis used un- steady flow data obtained from a highly resolved, time-dependent, Reynolds-averaged Navier-Stokes calculation. The analysis strongly suggests that vor- tex shedding from the trailing edge of the slat results in a high-amplitude, high-frequency acoustic signal, similar to that which was observed in a correspond- ing experimental study of the high-lift system.

  13. Konstruieren von Pkw-Karosserien: Grundlagen, Elemente und Baugruppen, Vorschriftenübersicht, Beispiele mit CATIA V4 und V5

    NASA Astrophysics Data System (ADS)

    Grabner, Jörg; Nothhaft, Richard

    Die Faszination, die vom Auto ausgeht, ist und bleibt ungebrochen. Entsprechend interessant ist es, sich vor dem Hintergrund konventioneller Konstruktionstechniken über die virtuelle Produktentwicklung von Pkw-Karosserien an modernen CAD-Arbeitsplätzen informieren zu können. Die Autoren führen in die Grundlagen ein und zeigen anhand von Beispielen und zahlreichen Abbildungen, wie mit dem System CATIA der Rohbau sowie die Ausstattung innen und au=C3=9Fen konstruiert werden. Darüber hinaus wird das so genannte "Package" an Beispielen beschrieben, also das Management und die Harmonisierung der Anforderungen an die Bauräume (z.

  14. Getreide, Brot und Feine Backwaren

    NASA Astrophysics Data System (ADS)

    von Grabowski, Hans-Uwe; Rolfe, Birgit

    Getreide und Getreideerzeugnisse sind ebenso wie Brot und Feine Backwaren nach dem Lebensmittel- und Futtermittel-Gesetzbuch (LFGB) [1] Lebensmittel im Sinne des Artikels 2 der VO (EG) Nr. 178/2002 (BasisVO) (s. auch Kap. 1.6/2.4.1/3.2). Gesetzlich festgelegte Begriffsbestimmungen gibt es für diese Lebensmittel nicht. Man muss sich daher allgemeiner Verkehrsauffassungen bedienen, wie sie von der Deutschen Lebensmittelbuch-Kommission in Form von Leitsätzen erarbeitet und veröffentlicht wurden [2]. Der Gesundheitsschutz und der Schutz des Verbrauchers vor Täuschung sind in der Basis-VO und dem LFGB geregelt.

  15. [Vestibular compensation studies]. [Vestibular Compensation and Morphological Studies

    NASA Technical Reports Server (NTRS)

    Perachio, Adrian A. (Principal Investigator)

    1996-01-01

    The following topics are reported: neurophysiological studies on MVN neurons during vestibular compensation; effects of spinal cord lesions on VNC neurons during compensation; a closed-loop vestibular compensation model for horizontally canal-related MVN neurons; spatiotemporal convergence in VNC neurons; contributions of irregularly firing vestibular afferents to linear and angular VOR's; application to flight studies; metabolic measures in vestibular neurons; immediate early gene expression following vestibular stimulation; morphological studies on primary afferents, central vestibular pathways, vestibular efferent projection to the vestibular end organs, and three-dimensional morphometry and imaging.

  16. Stabilization of gaze during circular locomotion in darkness. II. Contribution of velocity storage to compensatory eye and head nystagmus in the running monkey

    NASA Technical Reports Server (NTRS)

    Solomon, D.; Cohen, B.

    1992-01-01

    1. Yaw eye in head (Eh) and head on body velocities (Hb) were measured in two monkeys that ran around the perimeter of a circular platform in darkness. The platform was stationary or could be counterrotated to reduce body velocity in space (Bs) while increasing gait velocity on the platform (Bp). The animals were also rotated while seated in a primate chair at eccentric locations to provide linear and angular accelerations similar to those experienced while running. 2. Both animals had head and eye nystagmus while running in darkness during which slow phase gaze velocity on the body (Gb) partially compensated for body velocity in space (Bs). The eyes, driven by the vestibuloocular reflex (VOR), supplied high-frequency characteristics, bringing Gb up to compensatory levels at the beginning and end of the slow phases. The head provided substantial gaze compensation during the slow phases, probably through the vestibulocollic reflex (VCR). Synchronous eye and head quick phases moved gaze in the direction of running. Head movements occurred consistently only when animals were running. This indicates that active body and limb motion may be essential for inducing the head-eye gaze synergy. 3. Gaze compensation was good when running in both directions in one animal and in one direction in the other animal. The animals had long VOR time constants in these directions. The VOR time constant was short to one side in one animal, and it had poor gaze compensation in this direction. Postlocomotory nystagmus was weaker after running in directions with a long VOR time constant than when the animals were passively rotated in darkness. We infer that velocity storage in the vestibular system had been activated to produce continuous Eh and Hb during running and to counteract postrotatory afterresponses. 4. Continuous compensatory gaze nystagmus was not produced by passive eccentric rotation with the head stabilized or free. This indicates that an aspect of active locomotion, most

  17. Histone deacetylase inhibitor romidepsin induces HIV expression in CD4 T cells from patients on suppressive antiretroviral therapy at concentrations achieved by clinical dosing.

    PubMed

    Wei, Datsen George; Chiang, Vicki; Fyne, Elizabeth; Balakrishnan, Mini; Barnes, Tiffany; Graupe, Michael; Hesselgesser, Joseph; Irrinki, Alivelu; Murry, Jeffrey P; Stepan, George; Stray, Kirsten M; Tsai, Angela; Yu, Helen; Spindler, Jonathan; Kearney, Mary; Spina, Celsa A; McMahon, Deborah; Lalezari, Jacob; Sloan, Derek; Mellors, John; Geleziunas, Romas; Cihlar, Tomas

    2014-04-01

    Persistent latent reservoir of replication-competent proviruses in memory CD4 T cells is a major obstacle to curing HIV infection. Pharmacological activation of HIV expression in latently infected cells is being explored as one of the strategies to deplete the latent HIV reservoir. In this study, we characterized the ability of romidepsin (RMD), a histone deacetylase inhibitor approved for the treatment of T-cell lymphomas, to activate the expression of latent HIV. In an in vitro T-cell model of HIV latency, RMD was the most potent inducer of HIV (EC50 = 4.5 nM) compared with vorinostat (VOR; EC50 = 3,950 nM) and other histone deacetylase (HDAC) inhibitors in clinical development including panobinostat (PNB; EC50 = 10 nM). The HIV induction potencies of RMD, VOR, and PNB paralleled their inhibitory activities against multiple human HDAC isoenzymes. In both resting and memory CD4 T cells isolated from HIV-infected patients on suppressive combination antiretroviral therapy (cART), a 4-hour exposure to 40 nM RMD induced a mean 6-fold increase in intracellular HIV RNA levels, whereas a 24-hour treatment with 1 µM VOR resulted in 2- to 3-fold increases. RMD-induced intracellular HIV RNA expression persisted for 48 hours and correlated with sustained inhibition of cell-associated HDAC activity. By comparison, the induction of HIV RNA by VOR and PNB was transient and diminished after 24 hours. RMD also increased levels of extracellular HIV RNA and virions from both memory and resting CD4 T-cell cultures. The activation of HIV expression was observed at RMD concentrations below the drug plasma levels achieved by doses used in patients treated for T-cell lymphomas. In conclusion, RMD induces HIV expression ex vivo at concentrations that can be achieved clinically, indicating that the drug may reactivate latent HIV in patients on suppressive cART.

  18. Mathematik semantologisch verstehen

    NASA Astrophysics Data System (ADS)

    Wille, Rudolf

    Um zu verstehen, was Mathematik ist und bedeutet, reicht es nicht aus, mathematisches Denken und Wissen vielseitig zu erwerben. Hinzukommen muss stets ein angemessenes Verständnis der jeweiligen Bedeutungen mathematischer Denkformen, die in der aktual-realen Welt wirksam werden können. Beim Mathematik-Verstehen sollte es vor allem um ein Vermitteln des Selbstverständnisses der Mathematik, um ein Reflektieren des Bezugs der Mathematik zur realen Welt und um ein Beurteilen von Sinn, Bedeutung und Zusammenhang des Mathematischen in der Welt gehen.

  19. Flight evaluation of LORAN-C in the State of Vermont

    NASA Technical Reports Server (NTRS)

    Mackenzie, F. D.; Lytle, C. D.

    1981-01-01

    A flight evaluation of LORAN C as a supplement to existing navigation aids for general aviation aircraft, particularly in mountainous regions of the United States and where VOR coverage is limited was conducted. Flights, initiated in the summer months, extend through four seasons and practically all weather conditions typical of northeastern U.S. operations. Assessment of all the data available indicates that LORAN C signals are suitable as a means of navigation during enroute, terminal and nonprecision approach operations and the performance exceeds the minimum accuracy criteria.

  20. Kopf

    NASA Astrophysics Data System (ADS)

    Goldschmid, Alfred; Maier, Wolfgang; Olsson, Lennart; Piekarski, Nadine

    Die Evolution des Wirbeltierkopfes ist ein klassisches Problemfeld der vergleichend en Morphologie. Bereits J.W. von Goethe (1749-1832) und L. Oken (1779-1851) vertraten die Idee eines aus Segmenten bestehenden Schädels. Die Segmente sollten umgewandelten Wirbeln entsprechen; später wurden auch die Hirnnerven den segmentalen Spinalnerven des Rumpfes gleichgesetzt — Vorstellungen, die vor allem gegen Ende des 19. Jh. auf massive Ablehnung stießen. Die moderne Entwicklungsbiologie zei gt jedoch, dass zumindest Teile des Kopfes in ihrer Entwicklung eine deutliche Segmentierung aufweisen.

  1. Ländliche Entwicklung durch erneuerbare Energien - Das Beispiel Photovoltaik in Niederbayern

    NASA Astrophysics Data System (ADS)

    Zink, Roland

    2013-09-01

    Der Ausbau erneuerbarer Energien ist in Deutschland eine zentrale und politisch konsensfähige Forderung, um die Energieversorgung klimafreundlich und nachhaltig zu gestalten. Speziell ländliche Regionen rücken dabei in den Fokus, bieten sie doch aufgrund ihrer hohen Flächenverfügbarkeit große Potenziale für die flächenintensiven dezentralen Energieformen. Folglich erkennen Kommunen zunehmend das Entwicklungspotenzial dieser Technologien und sehen sie auch als Chance, neue wirtschaftliche Impulse vor Ort zu setzen. Der Beitrag skizziert die rasante Entwicklung der Photovoltaik im Regierungsbezirk Niederbayern und diskutiert anhand des Beispiels die Folgen für eine nachhaltige Regionalentwicklung.

  2. Altered resting-state functional connectivity in patients with chronic bilateral vestibular failure

    PubMed Central

    Göttlich, Martin; Jandl, Nico M.; Wojak, Jann F.; Sprenger, Andreas; der Gablentz, Janina von; Münte, Thomas F.; Krämer, Ulrike M.; Helmchen, Christoph

    2014-01-01

    Patients with bilateral vestibular failure (BVF) suffer from gait unsteadiness, oscillopsia and impaired spatial orientation. Brain imaging studies applying caloric irrigation to patients with BVF have shown altered neural activity of cortical visual–vestibular interaction: decreased bilateral neural activity in the posterior insula and parietal operculum and decreased deactivations in the visual cortex. It is unknown how this affects functional connectivity in the resting brain and how changes in connectivity are related to vestibular impairment. We applied a novel data driven approach based on graph theory to investigate altered whole-brain resting-state functional connectivity in BVF patients (n= 22) compared to age- and gender-matched healthy controls (n= 25) using resting-state fMRI. Changes in functional connectivity were related to subjective (vestibular scores) and objective functional parameters of vestibular impairment, specifically, the adaptive changes during active (self-guided) and passive (investigator driven) head impulse test (HIT) which reflects the integrity of the vestibulo-ocular reflex (VOR). BVF patients showed lower bilateral connectivity in the posterior insula and parietal operculum but higher connectivity in the posterior cerebellum compared to controls. Seed-based analysis revealed stronger connectivity from the right posterior insula to the precuneus, anterior insula, anterior cingulate cortex and the middle frontal gyrus. Excitingly, functional connectivity in the supramarginal gyrus (SMG) of the inferior parietal lobe and posterior cerebellum correlated with the increase of VOR gain during active as compared to passive HIT, i.e., the larger the adaptive VOR changes the larger was the increase in regional functional connectivity. Using whole brain resting-state connectivity analysis in BVF patients we show that enduring bilateral deficient or missing vestibular input leads to changes in resting-state connectivity of the brain

  3. Relation of motion sickness susceptibility to vestibular and behavioral measures of orientation

    NASA Technical Reports Server (NTRS)

    Peterka, Robert J.

    1995-01-01

    The objective is to determine the relationship of motion sickness susceptibility to vestibulo-ocular reflexes (VOR), motion perception, and behavioral utilization of sensory orientation cues for the control of postural equilibrium. The work is focused on reflexes and motion perception associated with pitch and roll movements that stimulate the vertical semicircular canals and otolith organs of the inner ear. This work is relevant to the space motion sickness problem since 0 g related sensory conflicts between vertical canal and otolith motion cues are a likely cause of space motion sickness.

  4. Von Donuts und Zucker: Mit Neutronen biologische Makromoleküle erforschen

    NASA Astrophysics Data System (ADS)

    May, Roland P.

    2003-05-01

    Für die Erforschung von Biomolekülen bieten Neutronen einzigartige Eigenschaften. Vor allem ihre unterschiedliche Wechselwirkung mit dem natürlichen Wasserstoff und seinem schweren Isotop Deuterium ermöglicht tiefe Einblicke in Struktur, Funktion und Dynamik von Proteinen, Nukleinsäuren und Biomembranen. Bei vielen Fragestellungen zur Strukturaufklärung gibt es kaum oder keine Alternative zum Neutron. Das Institut Laue-Langevin trägt Bahnbrechendes zum Erfolg der Neutronen-Methoden in der Biologie bei.

  5. Azole susceptibility of Malassezia pachydermatis and Malassezia furfur and tentative epidemiological cut-off values.

    PubMed

    Cafarchia, Claudia; Iatta, Roberta; Immediato, Davide; Puttilli, Maria Rita; Otranto, Domenico

    2015-09-01

    This study aims to determine the minimal inhibitory concentration (MIC) distribution and the epidemiological cut-off values (ECVs) of Malassezia pachydermatis and Malassezia furfur isolates for fluconazole (FLZ), itraconazole (ITZ), posaconazole (POS), and voriconazole (VOR). A total of 62 M. pachydermatis strains from dogs with dermatitis and 78 M. furfur strains from humans with bloodstream infections (BSI) were tested by a modified broth microdilution Clinical and Laboratory Standards Institute (CLSI) method. ITZ and POS displayed lower MICs than VOR and FLZ, regardless of the Malassezia species. The MIC data for azoles of M. pachydermatis were four two-fold dilutions lower than those of M. furfur. Based on the ECVs, about 94% of Malassezia strains might be categorized within susceptible population for all azoles, except for FLZ, and azole cross-resistance was detected in association with FLZ in M. pachydermatis but not in M. furfur.The study proposes, for the first time, tentative azole ECVs for M. pachydermatis and M. furfur for monitoring the emergence of isolates with decreased susceptibilities and shows that the azole MIC distribution varied according to the Malassezia species tested, thus suggesting the usefulness of determining the susceptibility profile for effective treatment of each species. PMID:26162472

  6. Relation between perception of vertical axis rotation and vestibulo-ocular reflex symmetry

    NASA Technical Reports Server (NTRS)

    Peterka, Robert J.; Benolken, Martha S.

    1992-01-01

    Subjects seated in a vertical axis rotation chair controlled their rotational velocity by adjusting a potentiometer. Their goal was to null out pseudorandom rotational perturbations in order to remain perceptually stationary. Most subjects showed a slow linear drift of velocity (a constant acceleration) to one side when they were deprived of an earth-fixed visual reference. The amplitude and direction of this drift can be considered a measure of a static bias in the subject's perception of rotation. The presence of a perceptual bias is consistent with a small, constant imbalance of vestibular function which could be of either central or peripheral origin. Deviations from perfect vestibulo-ocular reflex (VOR) symmetry are also assumed to be related to imbalances in either peripheral or central vestibular function. Researchers looked for correlations between perceptual bias and various measures of vestibular reflex symmetry that might suggest a common source for both reflective and perceptual imbalances. No correlations were found. Measurement errors could not account for these results since repeated tests on the same subjects of both perceptual bias and VOR symmetry were well correlated.

  7. Single motor unit activity in human extraocular muscles during the vestibulo-ocular reflex.

    PubMed

    Weber, Konrad P; Rosengren, Sally M; Michels, Rike; Sturm, Veit; Straumann, Dominik; Landau, Klara

    2012-07-01

    Motor unit activity in human eye muscles during the vestibulo-ocular reflex (VOR) is not well understood, since the associated head and eye movements normally preclude single unit recordings. Therefore we recorded single motor unit activity following bursts of skull vibration and sound, two vestibular otolith stimuli that elicit only small head and eye movements. Inferior oblique (IO) and inferior rectus (IR) muscle activity was measured in healthy humans with concentric needle electrodes. Vibration elicited highly synchronous, short-latency bursts of motor unit activity in the IO (latency: 10.5 ms) and IR (14.5 ms) muscles. The activation patterns of the two muscles were similar, but reciprocal, with delayed activation of the IR muscle. Sound produced short-latency excitation of the IO muscle (13.3 ms) in the eye contralateral to the stimulus. Simultaneous needle and surface recordings identified the IO as the muscle of origin of the vestibular evoked myogenic potential (oVEMP) thus validating the physiological basis of this recently developed clinical test of otolith function. Single extraocular motor unit recordings provide a window into neural activity in humans that can normally only be examined using animal models and help identify the pathways of the translational VOR from otoliths to individual eye muscles.

  8. Relation between perception of vertical axis rotation and vestibulo-ocular reflex symmetry

    NASA Technical Reports Server (NTRS)

    Peterka, Robert J.; Benolken, Martha S.

    1991-01-01

    Subjects seated in a vertical axis rotation chair controlled their rotational velocity by adjusting a potentiometer. Their goal was to null out pseudorandom rotational perturbations in order to remain perceptually stationary. Most subjects showed a slow linear drift of velocity (a constant acceleration) to one side when they were deprived of an earth-fixed visual reference. The amplitude and direction of this drift can be considered a measure of a static bias in the subject's perception of rotation. The presence of a perceptual bias is consistent with a small, constant imbalance of vestibular function which could be of either central or peripheral origin. Deviations from perfect vestibulocular reflex (VOR) symmetry are also assumed to be related to imbalances in either peripheral or central vestibular function. Researchers looked for correlations between perceptual bias and various measures of vestibular reflex symmetry that might suggest a common source for both reflective and perceptual imbalances. No correlations were found. Measurement errors could not account for these results since repeated tests on the same subjects of both perceptual bias and VOR symmetry were well correlated.

  9. Is German Medical Education Research on the rise? An analysis of publications from the years 2004 to 2013.

    PubMed

    Ackel-Eisnach, Kristina; Raes, Patricia; Hönikl, Lisa; Bauer, Daniel; Wagener, Stefan; Möltner, Andreas; Jünger, Jana; Fischer, Martin R

    2015-01-01

    Zielsetzung: Ausgangspunkt des vorliegenden Artikels ist die Feststellung, dass es aus Deutschland im Vergleich zu den angloamerikanischen Ländern oder den Niederlanden vor 2004 kaum internationale Publikationen im Bereich der medizinischen Ausbildungsforschung gab. In den letzten Jahren wurde jedoch eine steigende Bedeutung der medizinischen Ausbildungsforschung im deutschen Raum deutlich. Zielsetzung dieses Beitrags ist es zu prüfen, inwieweit sich in internationalen, englischsprachigen Fachzeitschriften im Themenfeld „Medizinische Ausbildungsforschung“ seit 2004 eine solche Entwicklung durch eine gesteigerte Publikationsaktivität belegen lässt. Methodik: Im Rahmen einer Literaturauswertung und Inhaltsanalyse wurden Artikel deutscher Autoren aus den Jahren 2004 bis 2013 in sechs internationalen englischsprachigen Fachzeitschriften der medizinischen Ausbildungsforschung analysiert. Um einen Überblick über die deutschen Forschungsaktivitäten in diesem Bereich zu bekommen, wurden alle Projekt- und Originalarbeiten deutscher Erst- und Letztautoren identifiziert und einer tiefergehenden inhaltlichen Analyse unterzogen. Ergebnisse: Insgesamt wurden 10.055 Artikel untersucht. Die Auswertung zeigt, dass zwischen 2004 und 2013 179 Artikel – hiervon 145 Projekt- und Originalarbeiten – deutscher Autoren in den betrachteten Zeitschriften publiziert wurden. Es zeigen sich Schwankungen im Zeitverlauf. Bei den Projekt- und Originalarbeiten handelt sich vor allem um Querschnitt- (27,8%) und randomisierte Kontrollstudien (25,6%) zum Thema „Lehr- und Lernmethoden“ (43,6%). Schlussfolgerung: Seit 2009 zeigt sich ein deutlicher Anstieg der Publikationszahlen deutscher Ausbildungsforscher in internationalen Fachzeitschriften im Vergleich zu den Jahren 2004-2008.

  10. Next Generation Life Support Project Status

    NASA Technical Reports Server (NTRS)

    Barta, Daniel J.; Chullen, Cinda; Vega, Leticia; Cox, Marlon R.; Aitchison, Lindsay T.; Lange, Kevin E.; Pensinger, Stuart J.; Meyer, Caitlin E.; Flynn, Michael; Jackson, W. Andrew; Abney, Morgan B.; Wheeler, Raymond M.

    2014-01-01

    Next Generation Life Support (NGLS) is one of over twenty technology development projects sponsored by NASA's Game Changing Development Program. The NGLS Project develops selected life support technologies needed for humans to live and work productively in space, with focus on technologies for future use in spacecraft cabin and space suit applications. Over the last three years, NGLS had five main project elements: Variable Oxygen Regulator (VOR), Rapid Cycle Amine (RCA) swing bed, High Performance (HP) Extravehicular Activity (EVA) Glove, Alternative Water Processor (AWP) and Series-Bosch Carbon Dioxide Reduction. The RCA swing bed, VOR and HP EVA Glove tasks are directed at key technology needs for the Portable Life Support System (PLSS) and pressure garment for an Advanced Extravehicular Mobility Unit (EMU). Focus is on prototyping and integrated testing in cooperation with the Advanced Exploration Systems (AES) Advanced EVA Project. The HP EVA Glove Element, new this fiscal year, includes the generation of requirements and standards to guide development and evaluation of new glove designs. The AWP and Bosch efforts focus on regenerative technologies to further close spacecraft cabin atmosphere revitalization and water recovery loops and to meet technology maturation milestones defined in NASA's Space Technology Roadmaps. These activities are aimed at increasing affordability, reliability, and vehicle self-sufficiency while decreasing mass and mission cost, supporting a capability-driven architecture for extending human presence beyond low-Earth orbit, along a human path toward Mars. This paper provides a status of current technology development activities with a brief overview of future plans.

  11. Caspase inhibitors promote vestibular hair cell survival and function after aminoglycoside treatment in vivo

    NASA Technical Reports Server (NTRS)

    Matsui, Jonathan I.; Haque, Asim; Huss, David; Messana, Elizabeth P.; Alosi, Julie A.; Roberson, David W.; Cotanche, Douglas A.; Dickman, J. David; Warchol, Mark E.

    2003-01-01

    The sensory hair cells of the inner ear undergo apoptosis after acoustic trauma or aminoglycoside antibiotic treatment, causing permanent auditory and vestibular deficits in humans. Previous studies have demonstrated a role for caspase activation in hair cell death and ototoxic injury that can be reduced by concurrent treatment with caspase inhibitors in vitro. In this study, we examined the protective effects of caspase inhibition on hair cell death in vivo after systemic injections of aminoglycosides. In one series of experiments, chickens were implanted with osmotic pumps that administrated the pan-caspase inhibitor z-Val-Ala-Asp(Ome)-fluoromethylketone (zVAD) into inner ear fluids. One day after the surgery, the animals received a 5 d course of treatment with streptomycin, a vestibulotoxic aminoglycoside. Direct infusion of zVAD into the vestibule significantly increased hair cell survival after streptomycin treatment. A second series of experiments determined whether rescued hair cells could function as sensory receptors. Animals treated with streptomycin displayed vestibular system impairment as measured by a greatly reduced vestibulo-ocular response (VOR). In contrast, animals that received concurrent systemic administration of zVAD with streptomycin had both significantly greater hair cell survival and significantly increased VOR responses, as compared with animals treated with streptomycin alone. These findings suggest that inhibiting the activation of caspases promotes the survival of hair cells and protects against vestibular function deficits after aminoglycoside treatment.

  12. The relationship between vestibular function and topographical memory in older adults

    PubMed Central

    Previc, Fred H.; Krueger, Wesley W.; Ross, Ruth A.; Roman, Michael A.; Siegel, Gregg

    2014-01-01

    Research during the past two decades has demonstrated an important role of the vestibular system in topographical orientation and memory and the network of neural structures associated with them. Almost all of the supporting data have come from animal or human clinical studies, however. The purpose of the present study was to investigate the link between vestibular function and topographical memory in normal elderly humans. Twenty-five participants aged 70 to 85 years who scored from mildly impaired to normal on the Montreal Cognitive Assessment (MoCA) received three topographical memory tests: the Camden Topographical Recognition Memory Test (CTMRT), a computerized topographical mental rotation test (TMRT), and a virtual pond maze (VPM). They also received six vestibular or oculomotor tests: optokinetic nystagmus (OKN), visual pursuit (VP), actively generated vestibulo-ocular reflex (VOR), the sensory orientation test (SOT) for posture, and two measures of rotational memory (error in degrees, or RM°, and correct directional recognition, or RM→). The only significant bivariate correlations were among the three vestibular measures primarily assessing horizontal canal function (VOR, RM°, and RM→). A multiple regression analysis showed significant relationships between vestibular and demographic predictors and both the TMRT (R = 0.78) and VPM (R = 0.66) measures. The significant relationship between the vestibular and topographical memory measures supports the theory that vestibular loss may contribute to topographical memory impairment in the elderly. PMID:24917795

  13. High-frequency dynamics of regularly discharging canal afferents provide a linear signal for angular vestibuloocular reflexes.

    PubMed

    Hullar, T E; Minor, L B

    1999-10-01

    Regularly discharging vestibular-nerve afferents innervating the semicircular canals were recorded extracellularly in anesthetized chinchillas undergoing high-frequency, high-velocity sinusoidal rotations. In the range from 2 to 20 Hz, with peak velocities of 151 degrees/s at 6 Hz and 52 degrees/s at 20 Hz, 67/70 (96%) maintained modulated discharge throughout the sinusoidal stimulus cycle without inhibitory cutoff or excitatory saturation. These afferents showed little harmonic distortion, no dependence of sensitivity on peak amplitude of stimulation, and no measurable half-cycle asymmetry. A transfer function fitting the data predicts no change in sensitivity (gain) of regularly discharging afferents over the frequencies tested but shows a phase lead with regard to head velocity increasing from 0 degrees at 2 Hz to 30 degrees at 20 Hz. These results indicate that regularly discharging afferents provide a plausible signal to drive the angular vestibuloocular reflex (VOR) even during high-frequency head motion but are not a likely source for nonlinearities present in the VOR. PMID:10515990

  14. A dynamic model of the eye nystagmus response to high magnetic fields

    NASA Astrophysics Data System (ADS)

    Glover, Paul M.; Li, Yan; Antunes, Andre; Mian, Omar S.; Day, Brian L.

    2014-02-01

    It was recently shown that high magnetic fields evoke nystagmus in human subjects with functioning vestibular systems. The proposed mechanism involves interaction between ionic currents in the endolymph of the vestibular labyrinth and the static magnetic field. This results in a Lorentz force that causes endolymph flow to deflect the cupulae of the semi-circular canals to evoke a vestibular-ocular reflex (VOR). This should be analogous to stimulation by angular acceleration or caloric irrigation. We made measurements of nystagmus slow-phase velocities in healthy adults experiencing variable magnetic field profiles of up to 7 T while supine on a bed that could be moved smoothly into the bore of an MRI machine. The horizontal slow-phase velocity data were reliably modelled by a linear transfer function incorporating a low-pass term and a high-pass adaptation term. The adaptation time constant was estimated at 39.3 s from long exposure trials. When constrained to this value, the low-pass time constant was estimated at 13.6 ± 3.6 s (to 95% confidence) from both short and long exposure trials. This confidence interval overlaps with values obtained previously using angular acceleration and caloric stimulation. Hence it is compatible with endolymph flow causing a cupular deflection and therefore supports the hypothesis that the Lorentz force is a likely transduction mechanism of the magnetic field-evoked VOR.

  15. [Cerebellar Control of Ocular Movements: Application to the Topographical Diagnosis of Cerebellar Lesions].

    PubMed

    Hirose, Genjiro

    2016-03-01

    Over the last decade, substantial information on cerebellar oculomotor control has been provided by the use of sophisticated neuroanatomical, neurophysiological, and imaging techniques. We now know that an intact cerebellum is a prerequisite for normal oculomotor performance. This review clarifies the current knowledge on structure-function correlations of the cerebellum in relation to ocular movements and allows them to be applied to topographical diagnosis of cerebellar lesions. The cerebellar regions most closely related to oculomotor function are: (1) the flocculus/paraflocculus for VOR suppression, cancellation, smooth pursuit eye movement and gaze-holding, (2) the nodulus/ventral uvula for velocity storage and low frequency prolonged vestibular response, and (3) the dorsal oculomotor vermis (declive VI, folium VII) and the posterior portion of the fastigial nucleus (fastigial oculomotor region) for saccades and smooth pursuit initiation. Symptomatically, defects in the flocculus/parflocculus cause saccadic pursuit, downbeat nystagmus, and impairments to visual suppression of the VOR. Lesions of the nodulus/uvula reveal as periodic alternating nystagmus. Lesions of the oculomotor vermis and the fastigial nucleus can induce saccadic dysmetria, while fastigial nucleus lesions may also cause ocular flutter/opsoclonus. A detailed knowledge of cerebellar anatomy and the physiology of eye movements enables localization of lesions to specific areas of the cerebellum. PMID:27001776

  16. Revealing the effects of the El Niño-southern oscillation on tropical cyclone intensity over the western north pacific from a model sensitivity study

    NASA Astrophysics Data System (ADS)

    Zhou, Yang; Jiang, Jing; Lu, Youyu; Huang, Anning

    2013-07-01

    Five sets of model sensitivity experiments are conducted to investigate the influence of tropical cyclone (TC) genesis location and atmospheric circulation on interannual variability of TC intensity in the western North Pacific (WNP). In each experiment, bogus TCs are placed at different initial locations, and simulations are conducted with identical initial and boundary conditions. In the first three experiments, the specified atmospheric and SST conditions represent the mean conditions of El Niño, La Niña, and neutral years. The other two experiments are conducted with the specified atmospheric conditions of El Niño and La Niña years but with SSTs exchanged. The model results suggest that TCs generated in the southeastern WNP incurred more favorable environmental conditions for development than TCs generated elsewhere. The different TC intensities between El Niño and La Niña years are caused by difference in TC genesis location and low-level vorticity (VOR). VOR plays a significant role in the intensities of TCs with the same genesis locations between El Niño and La Niña years.

  17. A Hydrogel-Based Hybrid Theranostic Contact Lens for Fungal Keratitis.

    PubMed

    Huang, Jian-Fei; Zhong, Jing; Chen, Guo-Pu; Lin, Zuan-Tao; Deng, Yuqing; Liu, Yong-Lin; Cao, Piao-Yang; Wang, Bowen; Wei, Yantao; Wu, Tianfu; Yuan, Jin; Jiang, Gang-Biao

    2016-07-26

    Fungal keratitis, a severe ocular disease, is one of the leading causes of ocular morbidity and blindness, yet it is often neglected, especially in developing countries. Therapeutic efficacy of traditional treatment such as eye drops is very limited due to poor bioavailability, whereas intraocular injection might cause serious side effects. Herein, we designed and fabricated a hybrid hydrogel-based contact lens which comprises quaternized chitosan (HTCC), silver nanoparticles, and graphene oxide (GO) with a combination of antibacterial and antifungal functions. The hydrogel is cross-linked through electrostatic interactions between GO and HTCC, resulting in strong mechanical properties. Voriconazole (Vor), an antifungal drug, can be loaded onto GO which retains the drug and promotes its sustained release from the hydrogel-based contact lenses. The contact lenses also exhibited good antimicrobial functions in view of glycidyltrimethylammonium chloride and silver nanoparticles. The results from in vitro and in vivo experiments demonstrate that contact lenses loaded with Vor have excellent efficacy in antifungal activity in vitro and could significantly enhance the therapeutic effects on a fungus-infected mouse model. The results indicate that this hydrogel contact lenses-based drug delivery system might be a promising therapeutic approach for a rapid and effective treatment of fungal keratitis. PMID:27244244

  18. Datenintegration und Deduplizierung

    NASA Astrophysics Data System (ADS)

    Bleiholder, Jens; Schmid, Joachim

    In Unternehmen liegen viele Daten heutzutage immer seltener vollständig an einem einzigen physikalischen Ort vor, sondern sind weltweit verteilt. Dies liegt zum einen an der immer besser gewordenen Infrastruktur, die eine solche Verteilung auf einfache Art und Weise ermöglicht, und zum anderen an der Tatsache, dass viele Unternehmen weltweit tätig sind. So fallen Daten weltweit an, werden aber jeweils lokal - vor Ort - gespeichert. Daher müssen oft mehrere Datenquellen genutzt werden, um einen aktuellen, vollständigen und genauen Überblick über die vorhandenen Daten zu gewinnen. Datenintegration hilft, indem sie Daten aus mehreren Quellen zusammenführt und einheitlich darstellt. Diese integrierten Daten können genutzt werden, um sich einen Überblick über das Unternehmen zu verschaffen, z.B. wenn Unternehmen fusionieren und nur noch eine Kundendatenbank bestehen bleiben soll, oder wenn zu einem Kunden die Daten aus den verschiedenen Fachabteilungen zusammengeführt werden sollen. Anhand eines solchen Beispiels, der Integration von Kundendaten zu Kfz- und Lebensversicherungen erläutern wir im Folgenden einzelne Techniken.

  19. Galvanic stimulation of the vestibular periphery in guinea pigs during passive whole body rotation and self-generated head movement

    PubMed Central

    Lim, K.; Dye, J.; King, W. M.

    2012-01-01

    Irregular vestibular afferents exhibit significant phase leads with respect to angular velocity of the head in space. This characteristic and their connectivity with vestibulospinal neurons suggest a functionally important role for these afferents in producing the vestibulo-collic reflex (VCR). A goal of these experiments was to test this hypothesis with the use of weak galvanic stimulation of the vestibular periphery (GVS) to selectively activate or suppress irregular afferents during passive whole body rotation of guinea pigs that could freely move their heads. Both inhibitory and excitatory GVS had significant effects on compensatory head movements during sinusoidal and transient whole body rotations. Unexpectedly, GVS also strongly affected the vestibulo-ocular reflex (VOR) during passive whole body rotation. The effect of GVS on the VOR was comparable in light and darkness and whether the head was restrained or unrestrained. Significantly, there was no effect of GVS on compensatory eye and head movements during volitional head motion, a confirmation of our previous study that demonstrated the extravestibular nature of anticipatory eye movements that compensate for voluntary head movements. PMID:22262827

  20. Postprandial decrease in vascular resistance correlated with change in second derivative of finger plethysmogram in young subjects.

    PubMed

    Tanaka, Kunihiko; Kamihira, Kimiko; Minoura, Fumie; Watanabe, Miyuki; Fujiyoshi, Emi; Nakamura, Koji; Katafuchi, Tetsuro

    2015-01-01

    Hintergrund: Die zweite Ableitung des Fingersplethysmogramms (ZAPTG) umfasst fünf Wellen, bezeichnet A bis E. Die Größen der Wellen B bis E werden für den intra- und interindividuellen Vergleich auf die der Welle A bezogen. In der vorliegenden Studie haben wir die Auswirkungen einer Mahlzeit auf ZAPTG bei jungen und älteren Probanden untersucht. Probanden und Methoden: Es wurde der mittlere arterielle Druck und ZAPTG vor und nach der Aufnahme einer Mahlzeit bei jungen und älteren Probanden gemessen. Für junge Probanden wurden Schlagvolumen und Pulsfrequenz bestimmt und die Summe des peripheren Widerstandes (SPW) der Blutgefäße wurde analysiert. Zudem wurde die Beziehung zwischen TPR und dem Verhältnis des Spitzenwerts ZAPTG in jungen Probanden bestimmt. Ergebnisse: Bei jungen Probanden war D / A postprandial deutlich größer und SPW kleiner als vor der Mahlzeit und war linear und signifikant mit TPR korreliert. Eine Erhöhung des postprandialen D / A wurde auch bei älteren nicht hypertensiven Menschen, nicht aber bei behandelten Hypertonikern beobachtet. Schlussfolgerungen: Eine Veränderung von D / A gilt als ein Index der Veränderung des SPW. SPW wird durch Antihypertensiva verringert. Eine Mahlzeit kann den SPW nicht weiter verringern. Diese Ergebnisse sind für das Verständnis der Hämodynamik nach Aufnahme einer Mahlzeit nützlich.

  1. Measurement of the vestibulo-ocular reflex by magnetometry during active head movement.

    PubMed

    Aldren, C P; FitzGerald, J E; Kelly, P; Birchall, J P; Murray, A

    1996-10-01

    A new method of measuring the vestibulo-ocular reflex (VOR) during active head movements is presented. Subjects sat and attempted to maintain their gaze upon a fixed point whilst turning their heads from side to side in response to an auditory cue, to attain frequencies of head rotation that increased from 1 Hz to 4 Hz during a 24 s period. Head movements were monitored by a small magnetic field detector worn on the subject's forehead and positioned a set distance from a magnetic field transmitter coil. Eye movements were monitored using the corneo-retinal potential. Gain (eye angle/head angle) and phase difference (eye phase-head phase) were calculated to define the VOR. Three repeat measurements were made on 20 normal subjects. Gain decreased significantly (P < 0.0001) with increasing frequency whilst the phase difference remained unchanged. The 95% prediction intervals were narrow for both gain (+/- 0.28) and phase (+/- 11 degrees). These data, together with the speed and ease of performance of the test, suggest that the test can provide valuable information on the performance of the vestibular system. PMID:8922697

  2. Kinematic principles of primate rotational vestibulo-ocular reflex. I. Spatial organization of fast phase velocity axes

    NASA Technical Reports Server (NTRS)

    Hess, B. J.; Angelaki, D. E.

    1997-01-01

    The spatial organization of fast phase velocity vectors of the vestibulo-ocular reflex (VOR) was studied in rhesus monkeys during yaw rotations about an earth-horizontal axis that changed continuously the orientation of the head relative to gravity ("barbecue spit" rotation). In addition to a velocity component parallel to the rotation axis, fast phases also exhibited a velocity component that invariably was oriented along the momentary direction of gravity. As the head rotated through supine and prone positions, torsional components of fast phase velocity axes became prominent. Similarly, as the head rotated through left and right ear-down positions, fast phase velocity axes exhibited prominent vertical components. The larger the speed of head rotation the greater the magnitude of this fast phase component, which was collinear with gravity. The main sequence properties of VOR fast phases were independent of head position. However, peak amplitude as well as peak velocity of fast phases were both modulated as a function of head orientation, exhibiting a minimum in prone position. The results suggest that the fast phases of vestibulo-ocular reflexes not only redirect gaze and reposition the eye in the direction of head motion but also reorient the eye with respect to earth-vertical when the head moves relative to gravity. As further elaborated in the companion paper, the underlying mechanism could be described as a dynamic, gravity-dependent modulation of the coordinates of ocular rotations relative to the head.

  3. Dynamics of the human linear vestibulo-ocular reflex at medium frequency and modification by short-term training

    NASA Technical Reports Server (NTRS)

    Shelhamer, M.; Roberts, D. C.; Zee, D. S.

    2000-01-01

    We study here the effect of a short-term training paradigm on the gain and phase of the human translational VOR (the linear VOR: LVOR). Subjects were exposed to lateral sinusoidal translations on a sled, at 0.5 Hz, 0.3 g peak acceleration. With subjects tracking a remembered target at 1.2 m, the LVOR (slow-phase) under these conditions typically has a phase lead or lag, and a gain that falls short of compensatory. To induce short-term adaptation (training), we presented an earth-fixed visual scene at 1.2 m during sinusoidal translation (x 1 viewing) for 20 minutes, so as to drive the LVOR toward compensatory phase and gain. We examined both the slow-phase and the saccadic responses to these stimuli. Testing after training showed changes in slow-component gain and phase which were mostly but not always in the compensatory direction. These changes were more consistent in naive subjects than in subjects who had previous LVOR experience. Changes in gain were seen with step as well as sinusoidal test stimuli; gain changes were not correlated with vergence changes. There was a strong correlation between gain changes and phase changes across subjects. Fast phases (catch-up saccades) formed a large component of the LVOR under our testing conditions (approximately 30% of the changes in gain but not in phase due to training.

  4. Coordination of Lower Limb Joints During Locomotion: The Effects of Vestibulo-Ocular Reflex Adaptation

    NASA Technical Reports Server (NTRS)

    Miller, Chris; Mulavara, Ajitkumar; Richards, Jason; Peters, Brian; Houser, Jeremy; Marshburn, Ann; Bloomberg, Jacob

    2003-01-01

    Controlling locomotion while maintaining a stable gaze requires precise coordination between several, interdependent full-body sensorimotor subsystems (Bloomberg and Mulavara, 2003; McDonald, et al., 1997). The overall goal of this study is to determine how this full-body gaze stabilization system responds to adaptive changes in vestibuloocular reflex (VOR) function. Locomotion involves cyclical physical interactions (impacts) with the environment. Hence, focusing on a target and maintaining visual acuity during this activity may require mechanisms to manage the energy flow, so it does not disrupt the visual and vestibular sensory information processing that stabilizes gaze. It has been shown that increasing the difficulty of a gaze task (reading numbers on a screen as opposed to simply focusing on a central dot pattern) resulted in an increase in the amount of knee flexion movement during the critical phase immediately following the heel strike event (Mulavara and Bloomberg, 2003). The increase in knee flexion during the stance phase of the gait cycle has been suggested to function as a shock absorbing mechanism associated with the rapid weight transfer from the trailing to the leading leg during walking. To understand this full-body coordination, the relative contributions of each component and the resulting effects should be assessed. In this study, we hypothesized that VOR adaptation would result in a reorganization of the lower limb joint coordination during treadmill walking in a manner to facilitate the gaze stabilization task and preserve locomotor function.

  5. Inactivation of Semicircular Canals Causes Adaptive Increases in Otolith-driven Tilt Responses

    NASA Technical Reports Server (NTRS)

    Angelaki, Dora E.; Newlands, Shawn D.; Dickman, J. David

    2002-01-01

    Growing experimental and theoretical evidence suggests a functional synergy in the processing of otolith and semicircular canal signals for the generation of the vestibulo-ocular reflexes (VORs). In this study we have further tested this functional interaction by quantifying the adaptive changes in the otolith-ocular system during both rotational and translational movements after surgical inactivation of the semicircular canals. For 0.1- 0.5 Hz (stimuli for which there is no recovery of responses from the plugged canals), pitch and roll VOR gains recovered during earth- horizontal (but not earth-vertical) axis rotations. Corresponding changes were also observed in eye movements elicited by translational motion (0.1 - 5 Hz). Specifically, torsional eye movements increased during lateral motion, whereas vertical eye movements increased during fore-aft motion. The findings indicate that otolith signals can be adapted according to compromised strategy that leads to improved gaze stabilization during motion. Because canal-plugged animals permanently lose the ability to discriminate gravitoinertial accelerations, adapted animals can use the presence of gravity through otolith-driven tilt responses to assist gaze stabilization during earth-horizontal axis rotations.

  6. Renaturierung von Tagebaufolgeflächen

    NASA Astrophysics Data System (ADS)

    Tischew, Sabine

    Der Abbau von Rohstoffen im Tagebauverfahren bedingt einen tief greifenden Landschafts- und Strukturwandel in den betroffenen Regionen. In der Abbauphase hat vor allem der Braunkohleabbau mit den tagebauübergreifenden Grundwasserabsenkungstrichtern, der Zerstörung oder Beeinträchtigung von ausgedehnten naturnahen Auenökosystemen sowie Wäldern und Elementen der Kulturlandschaft aus der Sicht des Naturschutzes überwiegend negative landschaftsökologische Folgen. Vor allem der Eingriff in Ökosysteme mit langen Entwicklungszeiten (alte Wälder, Moore) oder in die Dynamik von Auensystemen ist nicht oder nur in sehr langen Zeiträumen wieder ausgleichbar. Für letztere ist auch langfristig die Durchgängigkeit für viele Tierarten (Arten der Fließgewässer) nicht wieder vollständig herstellbar. Oft ist es zudem schwierig, traditionelle Landnutzungen (z. B. Wanderschäferei, Nutzung von Streuobstwiesen) nach der langen Abbauphase wieder aufzugreifen. Es ist deshalb eine wichtige Aufgabe, nach dem Abbauprozess auf der Grundlage der vorhandenen Potenziale eine nachhaltige Entwicklung der Bergbaufolgelandschaft zu unterstützen und von den Betreibern des Abbaus und von den Sanierungsgesellschaften auch einzufordern (z. B. Bauer 1998).

  7. Perception of self motion during and after passive rotation of the body around an earth-vertical axis.

    PubMed

    Sinha, N; Zaher, N; Shaikh, A G; Lasker, A G; Zee, D S; Tarnutzer, A A

    2008-01-01

    We investigated the perception of self-rotation using constant-velocity chair rotations. Subjects signalled self motion during three independent tasks (1) by pushing a button when rotation was first sensed, when velocity reached a peak, when velocity began to decrease, and when velocity reached zero, (2) by rotating a disc to match the perceived motion of the body, or (3) by changing the static position of the dial such that a bigger change in its position correlated with a larger perceived velocity. All three tasks gave a consistent quantitative measure of perceived angular velocity. We found a delay in the time at which peak velocity of self-rotation was perceived (2-5 s) relative to the beginning or to the end of chair rotation. In addition the decay of the perception of self-rotation was preceded by a sensed constant-velocity interval or plateau (9-14 s). This delay in the rise of self-motion perception, and the plateau for the maximum perceived velocity, contrasts with the rapid rise and the immediate decay of the angular vestibuloocular reflex (aVOR). This difference suggests that the sensory signal from the semicircular canals undergoes additional neural processing, beyond the contribution of the velocity-storage mechanism of the aVOR, to compute the percept of self-motion.

  8. HIV Latency-Reversing Agents Have Diverse Effects on Natural Killer Cell Function

    PubMed Central

    Garrido, Carolina; Spivak, Adam M.; Soriano-Sarabia, Natalia; Checkley, Mary Ann; Barker, Edward; Karn, Jonathan; Planelles, Vicente; Margolis, David M.

    2016-01-01

    In an effort to clear persistent HIV infection and achieve a durable therapy-free remission of HIV disease, extensive pre-clinical studies and early pilot clinical trials are underway to develop and test agents that can reverse latent HIV infection and present viral antigen to the immune system for clearance. It is, therefore, critical to understand the impact of latency-reversing agents (LRAs) on the function of immune effectors needed to clear infected cells. We assessed the impact of LRAs on the function of natural killer (NK) cells, the main effector cells of the innate immune system. We studied the effects of three histone deacetylase inhibitors [SAHA or vorinostat (VOR), romidepsin, and panobinostat (PNB)] and two protein kinase C agonists [prostratin (PROST) and ingenol] on the antiviral activity, cytotoxicity, cytokine secretion, phenotype, and viability of primary NK cells. We found that ex vivo exposure to VOR had minimal impact on all parameters assessed, while PNB caused a decrease in NK cell viability, antiviral activity, and cytotoxicity. PROST caused non-specific NK cell activation and, interestingly, improved antiviral activity. Overall, we found that LRAs can alter the function and fate of NK cells, and these effects must be carefully considered as strategies are developed to clear persistent HIV infection. PMID:27708642

  9. Kinetic analysis of [11C]vorozole binding in the human brain with positron emission tomography.

    PubMed

    Logan, Jean; Kim, Sung Won; Pareto, Deborah; Telang, Frank; Wang, Gene-Jack; Fowler, Joanna S; Biegon, Anat

    2014-01-01

    Using positron emission tomography, we investigated the kinetics of [11C]vorozole ([11C]VOR), a radiotracer for the enzyme aromatase that catalyzes the last step in estrogen biosynthesis. Six subjects were scanned under baseline conditions followed by retest 2 weeks later. The retest was followed by a blocking study with 2.5 mg of the aromatase inhibitor letrozole. The binding potential (BP(A)ND) was estimated from a Lassen plot using the total tissue distribution volume (VT) for baseline and blocked. for the thalamus was found to be 15 times higher than that for the cerebellum. From the letrozole studies, we found that [11C]VOR exhibits a slow binding compartment (small k4) that has a nonspecific and a blockable component. Because of the sensitivity of VT to variations in k4, a common value was used for the four highest binding regions. We also considered the tissue uptake to plasma ratio for 60 to 90 minutes as an outcome measure. Using the ratio method, the difference between the highest and lowest was 2.4 compared to 3.5 for the VT. The ratio method underestimates the high regions but is less variable and may be more suitable for patient studies. Because of its kinetics and distribution, this tracer is not a candidate for a bolus infusion or reference tissue methods.

  10. Oculomotor control of primary eye position discriminates between translation and tilt

    NASA Technical Reports Server (NTRS)

    Hess, B. J.; Angelaki, D. E.

    1999-01-01

    We have previously shown that fast phase axis orientation and primary eye position in rhesus monkeys are dynamically controlled by otolith signals during head rotations that involve a reorientation of the head relative to gravity. Because of the inherent ambiguity associated with primary otolith afferent coding of linear accelerations during head translation and tilts, a similar organization might also underlie the vestibulo-ocular reflex (VOR) during translation. The ability of the oculomotor system to correctly distinguish translational accelerations from gravity in the dynamic control of primary eye position has been investigated here by comparing the eye movements elicited by sinusoidal lateral and fore-aft oscillations (0.5 Hz +/- 40 cm, equivalent to +/- 0.4 g) with those during yaw rotations (180 degrees/s) about a vertically tilted axis (23.6 degrees). We found a significant modulation of primary eye position as a function of linear acceleration (gravity) during rotation but not during lateral and fore-aft translation. This modulation was enhanced during the initial phase of rotation when there was concomitant semicircular canal input. These findings suggest that control of primary eye position and fast phase axis orientation in the VOR are based on central vestibular mechanisms that discriminate between gravity and translational head acceleration.

  11. [Analysis of public quality reports for home care and long-term care with respect to their usefulness for the customer].

    PubMed

    Sünderkamp, Susanne; Weiß, Christian; Rothgang, Heinz

    2014-10-01

    Hintergrund: Seit dem Pflege-Weiterentwicklungsgesetz von 2008 und der Entwicklung der Pflegetransparenzvereinbarungen sollen Verbraucher die Möglichkeit erhalten, auf Basis einer flächendeckenden Qualitätsbeurteilung von ambulanten Pflegediensten und stationären Pflegeeinrichtungen eine informierte Wahl ihres Pflegeanbieters vorzunehmen. Ziel: Diese Studie prüft die Pflegenoten auf Basis einer empirischen Analyse der veröffentlichten MDK-Qualitätsberichte von 11 884 ambulanten Pflegediensten und 10 310 Pflegeheimen, was einer erstmaligen Vollerhebung aller bundesdeutschen Pflegeanbieter gleichkommt. Methoden: Auswertungen der deskriptiven Statistik und Diskussion der Ergebnisse in Hinblick auf die Nützlichkeit der Noten für den Verbraucher. Ergebnisse: Die Auswertungen zeigen eine begrenzte Aussagekraft der Pflegenoten für den Verbraucher. Ursächlich dafür sind insbesondere die durchschnittlich sehr guten Noten bei geringer Streuung und die großen Lücken in der Bewertung der einzelnen Kriterien, vor allem im ambulanten Bereich. Sie verstärken den Einfluss pflegeferner Kriterien auf die Gesamtnote und begünstigen den Ausgleich von Pflegemängeln durch guten Service. Dies kommt aber sehr selten vor. Eine stärkere Bewertung von Risikokriterien würde die Aussagekraft derzeit kaum erhöhen. Schlussfolgerungen: Die Konzeption der Pflegenoten bedarf einer gründlichen Optimierung, um die Nützlichkeit für den Verbraucher zu erhöhen.

  12. Peaks and troughs of three-dimensional vestibulo-ocular reflex in humans.

    PubMed

    Goumans, Janine; Houben, Mark M J; Dits, Joyce; van der Steen, Johannes

    2010-09-01

    The three-dimensional vestibulo-ocular reflex (3D VOR) ideally generates compensatory ocular rotations not only with a magnitude equal and opposite to the head rotation but also about an axis that is collinear with the head rotation axis. Vestibulo-ocular responses only partially fulfill this ideal behavior. Because animal studies have shown that vestibular stimulation about particular axes may lead to suboptimal compensatory responses, we investigated in healthy subjects the peaks and troughs in 3D VOR stabilization in terms of gain and alignment of the 3D vestibulo-ocular response. Six healthy upright sitting subjects underwent whole body small amplitude sinusoidal and constant acceleration transients delivered by a six-degree-of-freedom motion platform. Subjects were oscillated about the vertical axis and about axes in the horizontal plane varying between roll and pitch at increments of 22.5 degrees in azimuth. Transients were delivered in yaw, roll, and pitch and in the vertical canal planes. Eye movements were recorded in with 3D search coils. Eye coil signals were converted to rotation vectors, from which we calculated gain and misalignment. During horizontal axis stimulation, systematic deviations were found. In the light, misalignment of the 3D VOR had a maximum misalignment at about 45 degrees . These deviations in misalignment can be explained by vector summation of the eye rotation components with a low gain for torsion and high gain for vertical. In the dark and in response to transients, gain of all components had lower values. Misalignment in darkness and for transients had different peaks and troughs than in the light: its minimum was during pitch axis stimulation and its maximum during roll axis stimulation. We show that the relatively large misalignment for roll in darkness is due to a horizontal eye movement component that is only present in darkness. In combination with the relatively low torsion gain, this horizontal component has a relative

  13. High-Speed Video-Oculography for Measuring Three-Dimensional Rotation Vectors of Eye Movements in Mice

    PubMed Central

    Takeda, Noriaki; Uno, Atsuhiko; Inohara, Hidenori; Shimada, Shoichi

    2016-01-01

    Background The mouse is the most commonly used animal model in biomedical research because of recent advances in molecular genetic techniques. Studies related to eye movement in mice are common in fields such as ophthalmology relating to vision, neuro-otology relating to the vestibulo-ocular reflex (VOR), neurology relating to the cerebellum’s role in movement, and psychology relating to attention. Recording eye movements in mice, however, is technically difficult. Methods We developed a new algorithm for analyzing the three-dimensional (3D) rotation vector of eye movement in mice using high-speed video-oculography (VOG). The algorithm made it possible to analyze the gain and phase of VOR using the eye’s angular velocity around the axis of eye rotation. Results When mice were rotated at 0.5 Hz and 2.5 Hz around the earth’s vertical axis with their heads in a 30° nose-down position, the vertical components of their left eye movements were in phase with the horizontal components. The VOR gain was 0.42 at 0.5 Hz and 0.74 at 2.5 Hz, and the phase lead of the eye movement against the turntable was 16.1° at 0.5 Hz and 4.88° at 2.5 Hz. Conclusions To the best of our knowledge, this is the first report of this algorithm being used to calculate a 3D rotation vector of eye movement in mice using high-speed VOG. We developed a technique for analyzing the 3D rotation vector of eye movements in mice with a high-speed infrared CCD camera. We concluded that the technique is suitable for analyzing eye movements in mice. We also include a C++ source code that can calculate the 3D rotation vectors of the eye position from two-dimensional coordinates of the pupil and the iris freckle in the image to this article. PMID:27023859

  14. Prevention and control of catheter-associated urinary tract infections - implementation of the recommendations of the Commission for Hospital Hygiene and Infection Prevention (KRINKO) in nursing homes for the elderly in Frankfurt am Main, Germany.

    PubMed

    Heudorf, Ursel; Gasteyer, Stefanie; Müller, Maria; Samoiski, Yvonne; Serra, Nicole; Westphal, Tim

    2016-01-01

    Ziel: Nicht nur in Krankenhäusern, auch in Altenpflegeheimen zählen Harnwegsinfektionen zu den häufigsten nosokomialen Infektionen der Bewohner. Das größte Risiko für eine Harnwegsinfektion sind Harnwegskatheter. In den Empfehlungen „Infektionsprävention in Heimen“ (2005) und „Prävention und Kontrolle Katheter-assoziierter Harnwegsinfektionen“ (2015) hat die Kommission für Krankenhaushygiene und Infektionsprävention (KRINKO) geeignete Präventionsmaßnahmen empfohlen. Im Jahr 2015 wurde in allen Frankfurter Altenpflegeheimen die Umsetzung dieser KRINKO-Empfehlungen untersucht.Methode: Alle 40 Altenpflegeheime wurden anhand einer auf Grundlage dieser Empfehlungen erstellten Checkliste überprüft. Neben allgemeinen Arbeitsanweisungen, Indikationen etc. wurden bei allen Bewohnern mit Katheter Alter, Geschlecht, die Liegedauer des Katheters und Harnwegsinfekte aktuell und in den letzten 6 Monaten erfragt.Ergebnisse: In 35 (87,5%) der Altenpflegeheime lagen Arbeitsanweisungen zum Umgang mit Harnwegskathetern vor. Die Indikation für einen Harnwegskatheter wird von Ärzten gestellt, das Legen des Katheters wird häufig an den Pflegedienst delegiert; in aller Regel werden Silikonkatheter gelegt. In drei Viertel der Heime wurden feste Intervalle zum Katheterwechsel von 4–6 Wochen angegeben. Am jeweiligen Erhebungstag waren 7,3% der Bewohner mit einem Katheter versorgt. 3,6% (4,2%) von ihnen hatten am Erhebungstag, insgesamt 28% (28,9%) von ihnen in den vorangegangenen 6 Monaten eine Harnwegsinfektion (Prävalenz der Antibiotikatherapie in Klammern). Ciprofloxacin wurde am häufigsten eingesetzt, gefolgt von Cefuroxim und Cotrimoxazol.Diskussion: Bei der aktuellen Erhebung waren weniger Altenpflegeheimbewohner in Frankfurt mit Harnwegskathetern versorgt als in früheren Jahren und die Rate der Harnwegsinfektionen war niedrig. Dies spricht für einen zunehmend zurückhaltenderen und offenbar weitgehend sachgerechten Umgang mit Harnwegskathetern. Auch die

  15. Neural processing of gravito-inertial cues in humans. II. Influence of the semicircular canals during eccentric rotation.

    PubMed

    Merfeld, D M; Zupan, L H; Gifford, C A

    2001-04-01

    All linear accelerometers, including the otolith organs, respond equivalently to gravity and linear acceleration. To investigate how the nervous system resolves this ambiguity, we measured perceived roll tilt and reflexive eye movements in humans in the dark using two different centrifugation motion paradigms (fixed radius and variable radius) combined with two different subject orientations (facing-motion and back-to-motion). In the fixed radius trials, the radius at which the subject was seated was held constant while the rotation speed was changed to yield changes in the centrifugal force. In variable radius trials, the rotation speed was held constant while the radius was varied to yield a centrifugal force that nearly duplicated that measured during the fixed radius condition. The total gravito-inertial force (GIF) measured by the otolith organs was nearly identical in the two paradigms; the primary difference was the presence (fixed radius) or absence (variable radius) of yaw rotational cues. We found that the yaw rotational cues had a large statistically significant effect on the time course of perceived tilt, demonstrating that yaw rotational cues contribute substantially to the neural processing of roll tilt. We also found that the orientation of the subject relative to the centripetal acceleration had a dramatic influence on the eye movements measured during fixed radius centrifugation. Specifically, the horizontal vestibuloocular reflex (VOR) measured in our human subjects was always greater when the subject faced the direction of motion than when the subjects had their backs toward the motion during fixed radius rotation. This difference was consistent with the presence of a horizontal translational VOR response induced by the centripetal acceleration. Most importantly, by comparing the perceptual tilt responses to the eye movement responses, we found that the translational VOR component decayed as the subjective tilt indication aligned with the tilt of

  16. Kinematic principles of primate rotational vestibulo-ocular reflex. II. Gravity-dependent modulation of primary eye position

    NASA Technical Reports Server (NTRS)

    Hess, B. J.; Angelaki, D. E.

    1997-01-01

    The kinematic constraints of three-dimensional eye positions were investigated in rhesus monkeys during passive head and body rotations relative to gravity. We studied fast and slow phase components of the vestibulo-ocular reflex (VOR) elicited by constant-velocity yaw rotations and sinusoidal oscillations about an earth-horizontal axis. We found that the spatial orientation of both fast and slow phase eye positions could be described locally by a planar surface with torsional variation of <2.0 +/- 0.4 degrees (displacement planes) that systematically rotated and/or shifted relative to Listing's plane. In supine/prone positions, displacement planes pitched forward/backward; in left/right ear-down positions, displacement planes were parallel shifted along the positive/negative torsional axis. Dynamically changing primary eye positions were computed from displacement planes. Torsional and vertical components of primary eye position modulated as a sinusoidal function of head orientation in space. The torsional component was maximal in ear-down positions and approximately zero in supine/prone orientations. The opposite was observed for the vertical component. Modulation of the horizontal component of primary eye position exhibited a more complex dependence. In contrast to the torsional component, which was relatively independent of rotational speed, modulation of the vertical and horizontal components of primary position depended strongly on the speed of head rotation (i.e., on the frequency of oscillation of the gravity vector component): the faster the head rotated relative to gravity, the larger was the modulation. Corresponding results were obtained when a model based on a sinusoidal dependence of instantaneous displacement planes (and primary eye position) on head orientation relative to gravity was fitted to VOR fast phase positions. When VOR fast phase positions were expressed relative to primary eye position estimated from the model fits, they were confined

  17. Axis of eye rotation changes with head-pitch orientation during head impulses about earth-vertical.

    PubMed

    Migliaccio, Americo A; Schubert, Michael C; Clendaniel, Richard A; Carey, John P; Della Santina, Charles C; Minor, Lloyd B; Zee, David S

    2006-06-01

    The goal of this study was to assess how the axis of head rotation, Listing's law, and eye position influence the axis of eye rotation during brief, rapid head rotations. We specifically asked how the axis of eye rotation during the initial angular vestibuloocular reflex (VOR) changed when the pitch orientation of the head relative to Earth-vertical was varied, but the initial position of the eye in the orbit and the orientation of Listing's plane with respect to the head were fixed. We measured three-dimensional eye and head rotation axes in eight normal humans using the search coil technique during head-and-trunk (whole-body) and head-on-trunk (head-only) "impulses" about an Earth-vertical axis. The head was initially oriented at one of five pitch angles (30 degrees nose down, 15 degrees nose down, 0 degrees, 15 degrees nose up, 30 degrees nose up). The fixation target was always aligned with the nasooccipital axis. Whole-body impulses were passive, unpredictable, manual, rotations with peak-amplitude of approximately 20 degrees , peak-velocity of approximately 80 degrees /s, and peak-acceleration of approximately 1000 degrees /s2. Head-only impulses were also passive, unpredictable, manual, rotations with peak-amplitude of approximately 20 degrees , peak-velocity of approximately 150 degrees /s, and peak-acceleration of approximately 3000 degrees /s2. During whole-body impulses, the axis of eye rotation tilted in the same direction, and by an amount proportional (0.51 +/- 0.09), to the starting pitch head orientation (P < 0.05). This proportionality constant decreased slightly to 0.39 +/- 0.08 (P < 0.05) during head-only impulses. Using the head-only impulse data, with the head pitched up, we showed that only 50% of the tilt in the axis of eye rotation could be predicted from vectorial summation of the gains (eye velocity/head velocity) obtained for rotations about the pure yaw and roll head axes. Thus, even when the orientation of Listing's plane and eye

  18. H3K27 Demethylation at the Proviral Promoter Sensitizes Latent HIV to the Effects of Vorinostat in Ex Vivo Cultures of Resting CD4+ T Cells

    PubMed Central

    Tripathy, Manoj K.; McManamy, Mary E. M.; Burch, Brandon D.; Archin, Nancie M.

    2015-01-01

    ABSTRACT Histone methyltransferase inhibitors (HMTis) and histone deacetylase inhibitors (HDACis) are reported to synergistically induce the expression of latent human immunodeficiency virus type 1 (HIV-1), but studies have largely been performed with cell lines. As specific and potent HMTis directed at EZH1 (enhancer of zeste 2 Polycomb repressive complex 2 subunit 1)/EZH2 are now in human testing, we wished to rigorously test such an inhibitor in a primary resting T-cell model of HIV latency. We found that GSK343, a potent and selective EZH2/EZH1 inhibitor, reduced trimethylation of histone 3 at lysine 27 (H3K27) of the HIV provirus in resting cells. Remarkably, this epigenetic change was not associated with increased proviral expression in latently infected resting cells. However, following the reduction in H3K27 at the HIV long terminal repeat (LTR), subsequent exposure to the HDACi suberoylanilide hydroxamic acid or vorinostat (VOR) resulted in increases in HIV gag RNA and HIV p24 antigen production that were up to 2.5-fold greater than those induced by VOR alone. Therefore, in primary resting CD4+ T cells, true mechanistic synergy in the reversal of HIV latency may be achieved by the combination of HMTis and HDACis. Although other cellular effects of EZH2 inhibition may contribute to the sensitization of the HIV LTR to subsequent exposure to VOR, and to increase viral antigen production, this synergistic effect is directly associated with H3K27 demethylation at nucleosome 1 (Nuc-1). Based upon our findings, the combination of HMTis and HDACis should be considered for testing in animal models or clinical trials. IMPORTANCE Demethylation of H3K27 mediated by the histone methyltransferase inhibitor GSK343 in primary resting T cells is slow, occurring over 96 h, but by itself does not result in a significant upregulation of cell-associated HIV RNA expression or viral antigen production. However, following H3K27 demethylation, latent viral expression within

  19. General purpose algorithms for characterization of slow and fast phase nystagmus

    NASA Technical Reports Server (NTRS)

    Lessard, Charles S.

    1987-01-01

    In the overall aim for a better understanding of the vestibular and optokinetic systems and their roles in space motion sickness, the eye movement responses to various dynamic stimuli are measured. The vestibulo-ocular reflex (VOR) and the optokinetic response, as the eye movement responses are known, consist of slow phase and fast phase nystagmus. The specific objective is to develop software programs necessary to characterize the vestibulo-ocular and optokinetic responses by distinguishing between the two phases of nystagmus. The overall program is to handle large volumes of highly variable data with minimum operator interaction. The programs include digital filters, differentiation, identification of fast phases, and reconstruction of the slow phase with a least squares fit such that sinusoidal or psuedorandom data may be processed with accurate results. The resultant waveform, slow phase velocity eye movements, serves as input data to the spectral analysis programs previously developed for NASA to analyze nystagmus responses to pseudorandom angular velocity inputs.

  20. Molecular Identification and Susceptibility of Clinically Relevant Scedosporium spp. in China

    PubMed Central

    Wang, Hong; Wan, Zhe; Li, Ruoyu; Lu, Qiaoyun; Yu, Jin

    2015-01-01

    As various new sibling species within the Scedosporium spp. have been described recently, this study was conducted to investigate distribution and antifungal susceptibility profiles of the different species of Scedosporium spp. in China. Twenty-one clinical strains of Scedosporium from China and two strains from Japan were reidentified by MLSA. The analysis included BT2, CAL, RPB, SOD, and ACT and the combination of the five loci. Pseudallescheria boydii complex (17 strains) and S. apiospermum (6 strains) were identified. P. boydii complex included four closely related subgroups: P. boydii (9 strains), P. ellipsoidea (6 strains), P. fusoidea (1 strain), and P. angusta (1 strain). There were no significant differences in MICs for neither VOR, POS, nor AMB over all the five species in study. For itraconazole, intraspecific diversity was evident. PMID:26550562

  1. Computergestützte Patchplanung für Aortenerweiterungsplastiken

    NASA Astrophysics Data System (ADS)

    Rietdorf, Urte; Riesenkampff, Eugénie; Wolf, Ivo; Seitel, Mathias; Engel, Nicole; Kühne, Titus; Hübler, Michael; Schwarz, Tobias; Meinzer, Hans-Peter

    Stenosen der Aorta betreffen 5-8% aller Neugeborenen mit Herzfehlern und führen unbehandelt meist zum Tod. Liegt die Indikation für einen chirurgischen Eingriff vor, hängt die Wahl der Operationsmethode maßgeblich von der Anatomie der Aorta sowie dem Erfahrungsschatz des Operationsteams ab. Ein Verfahren hierbei ist die Patcherweiterungsplastik, bei der ein Patch in das Gefäß eingefügt wird, um das Lumen zu erweitern. Bisher erfolgt die Patchplanung intraoperativ auf Grundlage der Erfahrung des Operateurs. Wir haben eine Applikation entwickelt, mit der bereits präoperativ ein individueller Patchvorschlag angefertigt werden kann. Dadurch wird die Operationszeit verkürzt und postoperative Komplikationen wie Re-bzw. Reststenosen und Aneurysmen reduziert. Um die Applikation zu evaluieren wurde die Stenosenquantifizierung unseres Ansatzes mit der eines Kinderkardiologen verglichen und zeigt eine Abweichung im Durchmesser von lediglich (2,33 ±1,43) mm.

  2. Verbesserung der Prozessbedingungen beim Einlippentiefbohren durch unterschiedliche Formen der Vorschubmodulation

    NASA Astrophysics Data System (ADS)

    Eisseler, Rocco

    Das Tiefbohren mit Einlippenwerkzeugen ist bei vielen Anwendungen das Verfahren der ersten Wahl, vor allem wenn kleine und kleinste Bohrungsdurchmesser, ein sehr großes Verhältnis zwischen Bohrtiefe und Durchmesser (l/D) und eine hohe Bearbeitungsqualität gefordert werden. Der erreichbare Durchmesserbereich des Verfahrens liegt zwischen D = 0,5 mm und 40 mm, wobei die möglichen Bohrtiefen von l = 3 x D bis 250 x D reichen. Diese Werte beziehen sich auf das Vollbohren, beim Aufbohren können noch größere Durchmesser erreicht werden [1]. Die erreichbare Oberflächenqualität ist so hoch, dass in den meisten Fällen auf eine nachfolgende Feinbearbeitung verzichtet werden kann.

  3. Ganzheitliche Produktionssysteme

    NASA Astrophysics Data System (ADS)

    Korge, Axel; Lentes, Hans-Peter; Wengler, Michael; Hartmann, Thorsten; Röhrle, Josef; Kammüller, Mathias

    Erfolgreiche Unternehmer machen es vor: Mit einem Ganzheitlichen Produktionssystem (GPS) haben sie ihre Produktivität mehr als verdoppelt, die Durchlaufzeit bei verbesserter Termintreue halbiert und die Fehlerquote in den Promille-Bereich gedrückt [1]. Der Ansatz ist: Innovative Organisationsmethoden, die sich als Best-practice-Lösungen bewährt haben, werden zu einem in sich abgestimmten Gesamtsystem konfiguriert. Durch eine geeignete Auswahl und die gezielte Abstimmung geeigneter Methoden aufeinander können die drei Erfolgsfaktoren Qualität, Zeit und Kosten gleichzeitig erfüllt werden. Ein Ganzheitliches Produktionssystem versetzt die Produktionsmitarbeiter und Führungskräfte in die Lage, bessere Leistungsergebnisse mit weniger Stress zu erbringen. "Das ist nicht wirklich schwierig“, betont Josef Röhrle, der Werkleiter von Siemens Erlangen, Preisträger der Besten Fabrik 2004 und 2006, "denn alle Methoden sind bekannt und beschrieben.“

  4. Die Amtliche Sammlung von Untersuchungsverfahren nach § 64 LFGB, § 35 Vorläufiges Tabakgesetz und § 28b Gentechnikgesetz - ein Instrument der amtlichen Lebensmittelüberwachung

    NASA Astrophysics Data System (ADS)

    Renger, Silke; Stachel, Carolin

    Immer wieder werden Skandale in Zusammenhang mit Lebensmitteln bekannt. Schlagworte wie BSE, Gammelfleisch, Acrylamid, Cumarin oder auch Melamin, Dioxin sind den Verbrauchern geläufig und erschüttern das Vertrauen in ein gesundes und ernährungsphysiologisch wertvolles Lebensmittel. Das Bewusstsein des Verbrauchers hinsichtlich der Ernährung und der Auswahl beim Kauf der Lebensmittel hat sich in den vergangenen Jahren deutlich verändert. Bei der Auswahl seiner Lebensmittel liegt sein Augenmerk verstärkt auf gesunden, qualitativ hochwertigen und vor allem sicheren Lebensmitteln. Dies wurde insbesondere bei dem verhaltenen Kauf von Fleisch und Fleischerzeugnissen während der BSE-Krise oder auch dem kürzlich aufgetretenen Gammelfleischskandal deutlich.

  5. Modulare LDAP-Server-, -Protokoll und - Funktionserweiterungen am Beispiel von OpenLDAP

    NASA Astrophysics Data System (ADS)

    Pluta, Daniel

    In diesem Artikel wird ein Standardisierungsvorschlag für eine LDAP-Protokollerweiterung und deren Referenzimplementierung in Form einer modularen Erweiterung für die LDAP-Software-Suite des OpenLDAPProjektes vorgestellt. Nach einer Einführung in und einem Überblick über die wichtigsten OpenLDAP-Komponenten stellen wir unseren Lösungsansatz vor und gehen auf seine technischen Details ein. Ziel dieses Overlays ist die Implementierung einer neuen Funktionalität, die vom LDAP-Protokoll bisher nicht vorgesehen ist: Der Umfang der Suchergebnismenge soll serverseitig, dezentral und in der Granularität ganzer Objekte in Abhängigkeit von der aktuellen Serverzeit (konfigurierbar) eingeschränkt werden.

  6. Herausforderungen und Best Practices bei der Speicherung von multi-valued Attributen in LDAP-basierten Verzeichnisdiensten

    NASA Astrophysics Data System (ADS)

    Hommel, Wolfgang; Pluta, Daniel

    LDAP-basierte Verzeichnisdienste unterscheiden sich von relationalen Datenbankmanagementsystemen unter anderem stark bezüglich der Datenmodellierung. Dieser Artikel vertieft eingangs die Herausforderungen bei der LDAP-spezifischen Abbildung von Relationen zwischen mehreren multivalued Attributen. Die Diskussion erfolgt vor dem Hintergrund, dass einerseits Verzeichnisdienste generell nur bedingt zur Speicherung von Relationen geeignet sind und dass andererseits multi-valued Attribute ein mächtiges LDAP-Instrument sind, zu dem es in relationalen Datenbanksystemen keine direkte Entsprechung gibt. Anschließend werden Lösungskonzepte vorgestellt und mögliche Weiterentwicklungen des IntegraTUM-LDAP-Schemas zu deren Umsetzung skizziert, eine exemplarische Implementierung präsentiert und die Ergebnisse der bisherigen Entwicklung des IntegraTUM-Schemas gegenübergestellt.

  7. Kosteneffiziente Honbearbeitung durch intelligente und flexible Verknüpfung von autarken Honzentren

    NASA Astrophysics Data System (ADS)

    Roth, Günther

    Die Planungsabteilungen in der Automobilindustrie werden vor immer größere Herausforderungen gestsellt. Der zur Verfügung stehende Zeitraum zu einer seriensicheren Umsetzung der entwicklungs- und produktionstechnischen Forderungen wird von Projekt zu Projekt kürzer. Aufgrund des hohen Wettbewerbsdrucks und daraus resultierenden erforderlichen Kostenoptimierungen, die schnelleren Timeto-market-und Innovationszyklen und die vermeintlich zur Kundenbindung erforderlichen, kaum mehr überschaubaren Diversifizierungen in den Modellpaletten lassen den Planungshorizont immer kürzer werden. Die zu beschaffenden Fertigungsanlagen sollen aber in den nächsten 8-12 Jahren all die Varianten produzieren können, die heute nur teilweise oder noch gar nicht bekannt sind.

  8. Hochproduktive Werkzeugbeschichtungen

    NASA Astrophysics Data System (ADS)

    Kruszynski, Jacek

    Trotz vielfältiger Bemühungen, die Near Net Shape Technologie in weiten Produktionsbereichen zu etablieren, ist die spanabhebende Bearbeitung nach wie vor ein wesentlicher Faktor im Produktionsprozess und kann als solcher die Produktivität entscheidend beeinflussen. Allerdings haben sich die Anforderungen an den Zerspanungsprozess im Laufe der letzten Jahre stark gewandelt. Die Reduktion von Taktzeiten und die Erhöhung der Schnittgeschwindigkeiten bedeuten eine verstärkte mechanische und thermische Belastung für die Schneidstoffe. Hinzu kommt die Forderung nach Einengung der Toleranzen und Einsparung von Arbeitsgängen. Diese neuen Rahmenbedingungen führen dazu, dass eine stetige Anpassung der Werkzeuge sowohl hinsichtlich der Schneidengeometrie als auch im Bereich der Schneidstoffe selbst notwendig ist.

  9. Osteognathostomata

    NASA Astrophysics Data System (ADS)

    Schultze, Hans-Peter

    Noch häufig, vor allem im englischen Sprachraum, wird für die fischartigen Wirbeltiere mit Knochenskelett, also die Actinopterygii und Sarcopterygii, der Begriff "Osteichthyes" (Knochenfische) verwendet. Da sich jedoch aus einem Subtaxon der Sarcopterygier die Tet rapoda entwickelten (S. 322), würde diese Gruppierung ein paraphyletisches Taxon darstellen. Hier wird daher dem Vorschlag W. Hennigs (1983) gefolgt und die Schwestergruppe der Chondrichthyes Osteognathostomata genannt: Sie enthält alle weiteren kiefertragenden Wirbeltiere mit Knochenskelett (Name!) (Abb. 201). Die Sarcopterygii umfassen demnach verschiedene fossile Gruppen, die rezenten Reliktgruppen der Dipnoi (Lungenfische) und Actinistia (Hohlstachler) sowie die Tetrapoda und ihre Stammgruppenvertreter. (Neuerdings wird in der Literatur aus denselben Gründen einer konsequent phylogenetischen Systematisierung wieder die Gruppierung Osteichthyes, aber unter Einschluss der Tetrapoda, verwendet!).

  10. Wie alles begann

    NASA Astrophysics Data System (ADS)

    Steger, Almut

    An deutschen Universitäten entstand die Statistik als selbständige Wissenschaft vor gut 250 Jahren. Sie war zunächst reine Staatenbeschreibung. Erst im 19. Jahrhundert bildete sich der heutige Begriff von Statistik heraus. In mehreren Ländern gründete man damals statistische Vereine und länderübergreifend das Internationale Statistische Institut (ISI). Die deutschen Statistiker waren zwar ebenfalls national und international sehr aktiv, doch zur Gründung der Deutschen Statistischen Gesellschaft kam es erst 1911. Das Kapitel beschreibt diese Entwicklung, besonders ausführlich den Gründungsprozess. Danach wird über die schon mit der Gründung beginnenden, äußerst regen und zum Teil kontrovers ausgetragenen wissenschaftlichen Diskussionen berichtet, die jedoch mit dem Kriegsausbruch 1914 weitgehend zum Erliegen kamen.

  11. Molecular identification and susceptibility of clinically relevant Scedosporium spp. in China.

    PubMed

    Wang, Hong; Wan, Zhe; Li, Ruoyu; Lu, Qiaoyun; Yu, Jin

    2015-01-01

    As various new sibling species within the Scedosporium spp. have been described recently, this study was conducted to investigate distribution and antifungal susceptibility profiles of the different species of Scedosporium spp. in China. Twenty-one clinical strains of Scedosporium from China and two strains from Japan were reidentified by MLSA. The analysis included BT2, CAL, RPB, SOD, and ACT and the combination of the five loci. Pseudallescheria boydii complex (17 strains) and S. apiospermum (6 strains) were identified. P. boydii complex included four closely related subgroups: P. boydii (9 strains), P. ellipsoidea (6 strains), P. fusoidea (1 strain), and P. angusta (1 strain). There were no significant differences in MICs for neither VOR, POS, nor AMB over all the five species in study. For itraconazole, intraspecific diversity was evident. PMID:26550562

  12. IQM-Reifegradmodell für die Bewertung und Verbesserung des Information Lifecycle Management Prozesses

    NASA Astrophysics Data System (ADS)

    Baškarada, Saša; Gebauer, Marcus; Koronios, Andy; Gao, Jing

    Heutige Organisationen produzieren und speichern mehr Informationen als je zuvor. Der resultierende Informationsüberfluss, zusammen mit einem Mangel an Qualitätssicherung für das Information Lifecycle Management, führt zu einem unsicheren Status der Informationsqualität in vielen Organisationen. Weiterhin hat sich herausgestellt, dass das Bewerten, Verbessern und Steuern der Informationsqualität ein offenkundig schwieriges Unterfangen ist. Dieses Kapitel stellt ein Modell zur Bewertung und Verbesserung der Information Quality Management Capability Maturity (IQM-Reifegrad) vor. Es wird ein Satz von Kriterien vorgestellt, der aus Literaturrecherche und Fallstudien abgeleitet wurde. Die Reifegradindikatoren werden validiert und in einem mehrstufigen Reifegradmodell durch eine Delphi-Studie gruppiert. Das abgeleitete IQM-Reifegradmodell hilft Organisationen ihre bestehenden Praktiken im IQM zu bewerten und potentielle Lücken und Verbesserungsstrategien zu ermitteln.

  13. Qualität auf dem Prüfstand

    NASA Astrophysics Data System (ADS)

    Michaelis, Michael

    An einem Wochenende im Dezember 2009 beendete der chinesische Eisenbahn-Vizeminister Hu Yadong in Begleitung einer hochrangigen Delegation aus Experten des Department of Safety seines Ministeriums eine mehrtägige Europareise mit einem Besuch in der Konzernzentrale des weltweit führenden Herstellers von Bremssystemen für Schienen- und Nutzfahrzeuge in München. Schon in wenigen Jahren wird China über die weltweit größte Flotte an Hochgeschwindigkeitszügen verfügen und dabei sind Sicherheit und Qualität vorrangige Anforderungen. Knorr-Bremse liefert 100% der Bremsanlagen dieser Züge und hat vor kurzem mit rund 500 Millionen Euro den größten Auftrag in der Firmengeschichte erhalten. Das Unternehmen wird zusammen mit seinen chinesischen Partnern insgesamt 2.720 neue Wagen des chinesischen Hochgeschwindigkeitszuges CRH3 mit Brems- und Türsystemen ausrüsten.

  14. Niob

    NASA Astrophysics Data System (ADS)

    Dettner, H. W.; Franssen, H.; Giesen, K.; Hayes, E. T.; Holetzko, H.; Keysselitz, B.; Loebich, O.; Pelzel, E.; Reinsch, W.; Rostoker, W.; Saur, G.; Volk, K. E.; Wallbaum, H. J.; Borchers, Heinz; Schmidt, Ernst

    Niob — im angelsächsischen Schrifttum vielfach auch als "Columbium" (chemisches Zeichen "Cb") bezeichnet — wurde bis vor wenigen Jahren vorwiegend als Legierungselement in den sog. "Superalloys" oder zur Stabilisierung austenitischer Stähle verwendet. In neuerer Zeit wurden zahlreiche hochwarmfeste Legierungen auf Niobbasis für den Triebwerksbau und korrosionsbeständige Legierungen u. a. für die Verwendung als Hüllenwerkstoff im Reaktorbau entwickelt [D 2, G 1, H 2]. Niob-Uran-Legierungen scheinen sich zur Herstellung von Brennstoffelementen in Reaktoren zu bewähren. Vereinzelt wird Niob auch an Stelle des Tantals für hochwertige Senderöhren, Röntgenröhren und Hochspannungsgleichrichter verwendet. In der Vakuumtechnik dient es als wirksames "bulk getter" (nicht verdampfendes Getter) für den Temperaturbereich zwischen 400 und 900 °C [E 5].

  15. Demokrit - Planck

    NASA Astrophysics Data System (ADS)

    Rompe, Robert; Treder, Hans-Jürgen

    Es gibt eine Physik, die an die Konstante h gebunden ist und die mit der Atomistik zusammenhängt. Diese h-Physik geht eindeutig auf Planck zurück. Aber, aus dieser Physik folgt die Atomistik als Existenz lokalisierter geladener Teilchen unterschiedlichen Massen nicht, vor allem nicht die des Ladungsquants, so daß also Demokrit mehr behauptet hat, als die Quantenphysik zu beantworten kompetent ist.Translated AbstractDemokrit - PlanckA branch of physics exists closely linked to the constant h and associated with atomism. It is this h-physics that Planck originated. But atomism like existence of localized, charged particles with different masses does not follow from this physics, especially the charge quant. Hence Demokrit asserted more then quantum physics is competent to answer.

  16. Die Struktur von schlankem Materialfluss mit Lean Production Kanban und Innovationen

    NASA Astrophysics Data System (ADS)

    Scheid, Wolf-Michael

    In der Literatur wird Materialfluss überwiegend in Spezialdisziplinen betrachtet, etwa der Steuerungslogik, der Logistiktechnik oder dem Supply Chain Management. Ein charakterisierendes Merkmal des Materialflusses ist jedoch, dass er sich aus vielfältigen Einzelbausteinen zusammensetzt, die alle harmonisch abgestimmt sein müssen. Die maximal erreichbare Effizienz wird nicht durch Höchstleistungen in dem einen oder anderen Spezialthema bestimmt, sondern durch das schwächste Glied im gesamten komplexen Netzwerk. Den Schnittstellen zwischen den betroffenen Fachbereichen in einem Unternehmen kommt hier eine ganz besondere Bedeutung zu: Erst ein harmonischer Einklang ermöglicht hohe Effektivität. Dies setzt umfassendes Verständnis für interdisziplinäre Notwendigkeiten, ein hohes Maß an Abstimmung mit den operativen Prozessen und letztlich einen einvernehmlichen Umgang und den Respekt vor den Problemstellungen des Anderen voraus.

  17. [Educational competence of parents with children participating in youth welfare measures].

    PubMed

    Rücker, Stefan; Büttner, Peter; Petermann, Ulrike; Petermann, Franz

    2013-07-01

    Fragestellung: In der vorliegenden Studie wird der Einfluss ausgewählter Risiken auf das Erziehungsverhalten von Eltern am Beginn einer Jugendhilfe-Maßnahme analysiert. Methodik: Familiäre Belastungen sowie Erziehungsdimensionen wurden anhand standardisierter Erhebungsverfahren bei N = 74 Eltern erfasst. Ergebnisse: In Abhängigkeit des Belastungsausmaßes konnten drei Gruppen gebildet werden. Die Befragungsergebnisse wurden im Querschnitt varianzanalytisch ausgewertet. Familien mit spezifischen Risiken, wie materielle Belastungen, psychisch erkrankte Elternteile oder einen Alleinerziehendenstatus weisen signifikant ungünstigere Werte bei Erziehungsmerkmalen auf. In negativen Erziehungsmerkmalen kann der Einfluss spezifischer Risiken statistisch nicht abgesichert werden. Schlussfolgerungen: Spezifisch belastete Eltern in Jugendhilfe-Maßnahmen benötigen eventuell ein spezielles Training zur Steigerung ihrer Erziehungskompetenz. Dies gilt vor allem dann, wenn Prä-Post-Vergleiche am Ende der Maßnahme ein geringeres Erziehungs-Outcome in der spezifisch belasteten Gruppe offenbaren.

  18. Ejnar Hertzsprung

    NASA Astrophysics Data System (ADS)

    Herrmann, Dieter B.

    Mit diesem Werk von D.B. Herrmann, dem bekannten Astronomiehistoriker und Direktor der Archenhold-Sternwarte und des Zeiss-Großplanetariums in Berlin, liegt zum ersten Mal eine umfassende Biographie des großen Astronomen Ejnar Hertzsprung vor. Ejnar Hertzsprung (1873-1967) verdanken wir die Entdeckung der Riesen- und Zwergsterne, Grundlage für das sog. Hertzsprung-Russel-Diagramm, das eine zentrale Rolle bei der Erforschung der Sternentwicklung spielt. Er bearbeitete erfolgreich Doppelsterne und Veränderliche Sterne und trug Entscheidendes zur modernen Astrophysik bei. Wenig bekannt ist sein Leben, das hier unter Benutzung von Arbeitsmaterial, Interviews mit Zeitgenossen, des Familienarchivs und von Sekundärliteratur von einem kundigen Fachmann beschrieben wird. In D.B. Herrmanns Buch wird nicht nur Persönlichkeit und Werk von Hertzsprung lebendig, sondern auch die astronomische Forschung seiner Zeit. Dieser wertvolle Beitrag zur Wissenschaftsgeschichte wendet sich auch an eine breite allgemeine Leserschaft.

  19. [Bionic model for coordinated head-eye motion control].

    PubMed

    Mao, Xiaobo; Chen, Tiejun

    2011-10-01

    The relationships between eye movements and head movements of the primate during gaze shifts are analyzed in detail in the present paper. Applying the mechanisms of neurophysiology to engineering domain, we have improved the robot eye-head coordination. A bionic control strategy of coordinated head-eye motion was proposed. The processes of gaze shifts are composed of an initial fast phase followed by a slow phase. In the fast phase saccade eye movements and slow head movements were combined, which cooperate to bring gaze from an initial resting position toward the new target rapidly, while in the slow phase the gaze stability and target fixation were ensured by the action of the vestibulo-ocular reflex (VOR) where the eyes and head rotate by equal amplitudes in opposite directions. A bionic gaze control model was given. The simulation results confirmed the effectiveness of the model by comparing with the results of neurophysiology experiments.

  20. Gemeinsame Aspekte und Probleme in Physik und Geologie

    NASA Astrophysics Data System (ADS)

    Watznauer, A.

    Die griechische Naturphilosophie, vor allem Aristoteles, verstand unter Physik die Naturwissenschaft in toto. Die Aufspaltung dieser universellen Naturphilosophie in Fachdisziplinen betrifft sowohl den Gegenstand als auch, daraus abgeleitet, die Methodik der Darstellung. Die Physik, deren Gegenstand seit Galilei die reinen Fälle sind, ist ahistorisch. Die Geologie, die komplexe Systeme untersucht, ist dagegen eine historische Wissenschaft.Translated AbstractCommon Aspects and Problems in Physics and GeologyThe greek philosophers and above all Aristotle thougt in the physics about nature in toto. The splitting of this philosophy of nature into different sciences concerns both their topics and their methods. Since Galilei physics is concerned with pure cases, being an ahistorical science. On the contrary geology examines complex systems, being of historical character.