Harris Cs

Bio: Harris Cs is an academic researcher. The author has contributed to research in topics: Swing. The author has an hindex of 1, co-authored 1 publications receiving 17 citations.

Spatial memory of body linear displacement: what is being stored?

Abstract: The ability to evaluate traveled distance is common to most animal species. Head trajectory in space is measured on the basis of the converging signals of the visual, vestibular, and somatosensory systems, together with efferent copies of motor commands. Recent evidence from human studies has shown that head trajectory in space can be stored in spatial memory. A fundamental question, however, remains unanswered: How is movement stored? In this study, humans who were asked to reproduce passive linear whole-body displacement distances while blindfolded were also able to reproduce velocity profiles. This finding suggests that a spatiotemporal dynamic pattern of motion is stored and can be retrieved with the use of vestibular and somesthetic cues.

Orientation of the rotation-axis relative to gravity: its influence on nystagmus and the sensation of rotation.

Abstract: Subjective phenomena and nystagmus were compared under two conditions of rotation, one in which the axis of rotation was vertical, i.e., aligned with gravity, and one in which the rotation-axis was horizontal. When the axis of rotation was horizontal, normal subjects exhibited nystagmus and sensations of rotation for periods of three minutes (and longer); deceleration produced very brief post-rotational reactions. L-D subjects, men presumed to be without vestibular function, did not exhibit nystagmus or report sensations similar to those of normal subjects for either the vertical or horizontal axis of rotation. Because prolonged nystagmus occurred almost exclusively in normal subjects when the rotation axis was horizontal, it is concluded that vestibular function is a necessary condition for this response and that it may be dependent upon the continuous reorientation of the otolith system relative to gravity. The results emphasize the importance of increasing our range of experimental observations to chec...

Multimodal integration of self-motion cues in the vestibular system: active versus passive translations.

Abstract: The ability to keep track of where we are going as we navigate through our environment requires knowledge of our ongoing location and orientation. In response to passively applied motion, the otolith organs of the vestibular system encode changes in the velocity and direction of linear self-motion (i.e., heading). When self-motion is voluntarily generated, proprioceptive and motor efference copy information is also available to contribute to the brain's internal representation of current heading direction and speed. However to date, how the brain integrates these extra-vestibular cues with otolith signals during active linear self-motion remains unknown. Here, to address this question, we compared the responses of macaque vestibular neurons during active and passive translations. Single-unit recordings were made from a subgroup of neurons at the first central stage of sensory processing in the vestibular pathways involved in postural control and the computation of self-motion perception. Neurons responded far less robustly to otolith stimulation during self-generated than passive head translations. Yet, the mechanism underlying the marked cancellation of otolith signals did not affect other characteristics of neuronal responses (i.e., baseline firing rate, tuning ratio, orientation of maximal sensitivity vector). Transiently applied perturbations during active motion further established that an otolith cancellation signal was only gated in conditions where proprioceptive sensory feedback matched the motor-based expectation. Together our results have important implications for understanding the brain's ability to ensure accurate postural and motor control, as well as perceptual stability, during active self-motion.

Vestibular control of oculomotor and postural mechanisms

Abstract: The following subjects are considered in this review: anatomy and functional characteristics of the vestibular apparatus (including the semicircular canals; dynamics of otolith behaviour); the vestibulo-ocular reflex mechanisms (including; neurophysiology; dynamic response of the canal-occular reflex); the vestibulo-spinal reflex mechanisms (including: neurophysiology; the nature of vestibular myoneural control).