Search PubMed⌕ Search

Biomedical subjects

J R Lackner

Publications and source records attributed to J R Lackner.

At least 127 records · Page 7Linked to original sources
PubMed1976

Influence of abnormal postural and sensory conditions on human sensorimotor localization.

A wide range of experiments exposing subjects to unusual postural, sensory, and gravitational conditions have been discussed. In general, regardless of the nature of the experimental intervention, changes in sensory localization and sensorimotor coordination resulted. After prolonged exposure to the abnormal stimulus situation, sensory localization as well as sensorimotor coordination showed evidence of compensation, with performance returning toward normal. Our characterization and understanding of these experimental situations has only begun. Similar principles appear, however, to underlie many of these studies. Changes in interpreted posture induced by angular and linear acceleration are accompanied by changes in visual and auditory localization of comparable size. Rearrangement of the visual array by prism spectacles causes errors in sensorimotor coordination that are later eliminated by postural adjustments. Thus, in general, exposure to visual orientation, results in errors insensory localization; exposure to these abnormal states leads to compensatory alterations in postural and sensory mechanisms by a systematic modification of their interrelationship.

Adaptation, Physiological↗
PubMedDate not supplied

Influence of voluntary ocular deviation on vestibular nystagmus.

We examined the influence of voluntary gaze deviation on per-rotary vestibular nystagmus during trapezoidal velocity profiles. Gaze deviation in the direction of the fast-phase component of nystagmus significantly increased slow-phase amplitude, fast-phase amplitude and slow-phase velocity; gaze deviation in the direction of the slow phase marginally decreased these three properties. Schlagfeld deviation and beat frequency were unaffected by per-rotary ocular deviation in either direction. The observed changes in per-rotary eye movements are consistent with post-rotary observations first described by Alexander which later became known as "Alexander's Law".

Adult↗
PubMedDate not supplied

Stabilization of posture by precision contact of the index finger.

Postural sway during quiet stance increases if sight of the surroundings is denied. We studied how sensory-motor information about body displacement provided by contact of the index finger with a stationary bar can be used to stabilize balance in the absence of vision. Stabilization equivalent to the contribution conferred by vision was achieved at contact force levels less than 1 N. This value is much below that necessary to provide significant physical stabilization of the body. We interpret our findings in relation to tactile thresholds for motion detection, "precision grip," and proprioceptive and sensory-motor information about the configuration of the arm to the torso. In conditions allowing higher force levels at the fingertip (5-8 N), subjects assumed a passively stable state to stabilize their stance.

Adult↗