Perseveration as a sign of diffuse and focal brain damage. I.
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Brain Diseases↗
Biomedical subjects
R S Allison
Publications and source records attributed to R S Allison.
"On nervous disease in Thailand".
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Humans↗
The relative role of visual and non-visual cues in determining the perceived direction of "up": experiments in parabolic flight.
In order to measure the perceived direction of "up", subjects judged the three-dimensional shape of disks shaded to be compatible with illumination from particular directions. By finding which shaded disk appeared most convex, we were able to infer the perceived direction of illumination. This provides an indirect measure of the subject's perception of the direction of "up". The different cues contributing to this percept were separated by varying the orientation of the subject and the orientation of the visual background relative to gravity. We also measured the effect of decreasing or increasing gravity by making these shape judgements throughout all the phases of parabolic flight (0 g, 2 g and 1 g during level flight). The perceived up direction was modeled by a simple vector sum of "up" defined by vision, the body and gravity. In this model, the weighting of the visual cue became negligible under microgravity and hypergravity conditions.
Cues↗
Vestibulo-ocular reflex deficits to rapid head turns following intratympanic gentamicin instillation.
The response of the vestibulo-ocular reflex following unilateral vestibular deafferentation by gentamicin ablation was studied using transient stimuli. The response to these rapid passive head turns showed a strong asymmetry with permanent, reduced gains toward the side of lesion. These gain reductions have large variation (gains of 0.26 to 0.83), which may result from preferential sparing of regularly firing afferent fibers following gentamicin ablation. Based on the size and nature of the nonlinearity, an explanation based on Ewald's second law was discounted.
Adult↗
Post-rotatory nystagmus and turning sensations after active and passive turning.
We measured post-rotatory nystagmus and sensations of body rotation in standing subjects brought to rest in the dark after 3 minutes of each of the following conditions: 1) passive turning about the mid-body axis, involving only vestibular stimulation, 2) active turning about the mid-body axis, involving both vestibular stimulation and motor-proprioceptive activity in the legs, and 3) stepping round while remaining facing in the same direction on the center of a rotating platform with the head held in a stationary holder (apparent turning), involving only motor-proprioceptive activity. The same acceleration-velocity profile was used in all conditions. Post-rotatory nystagmus (slow phase) occurred in the same direction to passive body turning and was reduced in velocity after active body turning. After apparent turning, nystagmus was in the opposite direction as attempted body turning. Our theoretical analysis suggests that nystagmus after active turning should conform to the mean of the responses after passive and apparent turning rather than to their sum. The results conform more closely to the mean than to the sum, but with greater weight given to vestibular inputs than to motor-proprioceptive inputs. Post-rotatory sensations of self-rotation were in the expected opposite direction after passive turning and were lower in magnitude after active turning. After apparent turning, sensations of self-rotation were in the same direction as those after attempted turning--an effect known as the antisomatogyral illusion.
Adult↗