1. The presence of a form stretch reflex, previously described in the arm by other authors, has been confirmed gastrocnemius muscle human leg. electromyographic (e.m.g.) manifestation this reflex occurred 120 msec (S.E. mean = 3.5 msec) following sharply applied, and maintained, dorsiflexing force to foot. This response is referred article as Functional Stretch Reflex (FSR).2. To determine contribution FSR control normal leg movement, e.m.g. activity above was monitored during single...

1. These experiments investigated plastic changes in the vestibulo‐ocular reflex (VOR) of human subjects consequent to long‐term optical reversal vision during free head movement. Horizontal vision‐reversal was produced by head‐mounted dove prisms. Four normal adults were continuously exposed these conditions 2, 6, 7 and 27 days respectively. 2. A sinusoidal rotational stimulus, previously shown be nonhabituating (1/6 Hz; 60°/sec amplitude), used test VOR dark at frequent intervals both...

1. It was previously shown that the controlled landing from single steps to ground is typically brought about by accurately timed motor activity, commencing before actual landing, and completed time would permit participation of a useful stretch reflex response.2. To investigate further validity this conclusion, subjects were dropped an electromagnetic suspension at unexpected moments. Their gastrocnemius electromyographic (e.m.g.) responses forces applied their feet recorded throughout.3....

1. Two sets of experiments have examined the vestibulo‐ocular response (VOR) to repeated sinusoidal rotation ( A ) in dark and B after attempting visual tracking a mirror‐reversed image surround. 2. In both horizontal rotational stimulus 1/6 Hz 60°/sec angular velocity amplitude was employed, specifically chosen lie within presumed range natural stimulation semicircular canals. 3. each seven subjects underwent ten 2‐min runs standard on three consecutive days, with 3‐min rest periods between...

The physiological processes concerned with the difficult dynamic task of fixating retinal image during normal body and head movement are examined a control engineering perspective. Spatial relationships between two main system inputs (visual vestibular) three outputs (operating on eye-in-skull, skull-on-body, body-in-space platforms) in context geometry environment aid an information flow diagram. From considerations picture emerges which visual tracking has adequate accuracy range for...

1. The neural response of semicircular canal‐dependent units in the vestibular nuclei cats has been examined over a frequency range sinusoidal rotation extending from 0·004 to 0·9 Hz. 2. Frequency—response analysis indicates that, examined, information contained signal received by brain stem was similar that expected mechanical end‐organ. 3. Over experimental range, relation between and stimulus found be dominated single time constant about 4 sec, such two regions can defined above below ¼...

Human subjects were vertically oscillated in the dark over a frequency range of 1–0.02 Hz at peak-to-peak acceleration amplitudes 0.2–0.6 g, using both vertical movement simulator and real flight. Subjective tracking was unreliable showed no systematic dependence phase upon frequency. In contrast, reflex oculomotor response, although weak, clearly demonstrated progressive substantial lag with increasing The similarity this characteristic to that previously obtained from brainstem neural...

1. The characteristics of the dynamic response specifically canal‐dependent neural units in cat vestibular nuclei have been examined during sinusoidal rotation head decerebrate cats over narrow frequency range 0·–1·7 Hz. 2. Unit action potential frequencies were averaged on line from extracellular steel micro‐electrodes stereotaxically located through intact cerebellum. 3. Action was approximately phase with stimulus angular velocity, mean for forty‐six being + 11·° S.E. ± 2·2°). Correction...

Recent experimental observations indicate that pathways interconnecting the bilateral vestibular nuclei (VN) may provide positive-feedback loops for signals across midline. The implications of such positive feedback are considered in context compensation. A simple conceptual model interconnected VN is studied analytically, based on hypothesis restoration central symmetry achieved via changes neural gain closed commissural loops. wide variety conditions related to compensation investigated....

A mathematical model for short-term adaptation to vestibular stimuli is presented. transfer function derived relating slow phase angular velocity of resulting nystagmus the head rotation. The has been tested by comparing its responses controlled step and ramp with those 8 human subjects, in all cases a close match was obtained. mean time constant adaptive term 82 sec (S.E.±6.5) cupular restoration (Tc) 21 (S.E.±1.5). It suggested that previous values quoted Tc represent underestimates true...