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Biomedical subjects

W R Adey

Publications and source records attributed to W R Adey.

At least 91 records · Page 5Linked to original sources
PubMed1973

Influence of eye movements on geniculo-striate excitability in the cat.

1. The excitability of the geniculo-striate pathway during a saccadic eye movement was studied in alert cats with chronically implanted electrodes. Excitability was assessed by the amplitude of post-synaptic components of field responses in both lateral geniculate nucleus and visual cortex to electrical stimulation of the optic chiasm. Modifications in amplitude were evaluated during the period following eye movements, by triggering a stimulator from potential shifts in the electrooculograms and altering delays in the stimulus pulse.2. The post-synaptic component of the geniculate response was markedly depressed for about 150 msec, reaching a trough at approximately 100 msec after the initiation of an eye movement. This effect was dependent on the visual environment and was not observed in complete darkness. A similar depression occurred when the visual field was abruptly moved by retinal impulses generated by a quick displacement of the image of the visual world associated with an eye movement. The depression reflected a reduction of cellular discharge to the orthodromic volley and hence a suppression of the transmission of visual information through the lateral geniculate nucleus. This may be a mechanism for saccadic suppression.3. The post-synaptic components of the cortical response were enhanced for about 200 msec, reaching a peak at approximately 150 msec after the initiation of an eye movement. Although this facilitation occurred also in complete darkness, it did not occur when the visual field was abruptly shifted while the eyes were stationary. The fact that it occurred with eye movements and exclusively in the post-synaptic components suggests that it was caused by signals from a system closely related to eye movements. This may be a manifestation of the corollary mechanism.

Action Potentials↗
PubMed1972

Studies on weightlessness in a primate in the Biosatellite 3 experiment.

In June 1969 a male Macaca nemestrina (pigtail macaque) was flown in earth orbit for 8.8 days in NASA Biosatellite 3. The experiment examined in detail central nervous and cardiovascular functions, and included pre- and post-flight whole body metabolic assessment, in-flight urine analysis, and pre-and post-flight bone density measurements. Although the sleep/wake cycle was 24 hr, a phase angle lag of 2 hr from the imposed night/day mode occurred. A definite desynchronosis occurred, with rhythms longer than 24 hr in pCO2, brain and body temperature and heart rate, although arterial blood pressure remained at 24 hr. Sleep states were remarkably fragmented and unusually brief in duration. Vestibular and ocular disturbances were evident. These changes began concurrently with onset of weightlessness and were not secondary to altered fluid balance or body temperature. Sleep patterns lie between those of normal man and man with high cervical cord transection. There was an immediate and sustained increase in central venous pressure in weightlessness and this is considered to have initiated a Henry-Gauer reflex which initially maintained a high urine volume. This, coupled with a high evaporative fluid loss, produced an early dehydration probably associated with electrolyte imbalances. Body weight was 20% lower at recovery than at launch. Ventricular fibrillation supervened 8 hr after recovery.

Adaptation, Physiological↗