Biomedical subjects
Publications and source records attributed to S M Luria.
The effects of q.i.d. administration of 60 mg pseudoephedrine (Sudafed) tablets or pseudoephedrine-triprolidine (Actifed) tablets after 5 d of medication were measured on tests of night vision, color perception, stereopsis, and reaction time. Neither drug appeared to impair performance.
Eye movements were recorded while subjects viewed ordinary portraits and photographic negatives of those portraits. Under both conditions they first studied sixteen portraits and then tried to decide which of forty-eight portraits they had just seen. They made more errors of recognition while viewing negatives, and their fixation patterns were significantly altered: there was a decrease in the percentage of fixations directed to the eyes, nose, and mouth, and an increase for such details as the ears, cheeks, chin, cap, and necktie. There was also a decrease in the ratio of fixations to the most fixated detail compared to the least fixated detail.
Luminance thresholds were measured for the water-immersed eye as a function of adaptation level, viewing distance, and turbidity of the water, and compared to standard adaptation curves. In water, thresholds varied as a function of initial adaptation level, and the rate of adaptation paralleled that for the eye in air. However, thresholds were about 1-2 log units higher for the water-immersed eye than for the eye in air at all adaptation levels.
Thresholds for letters were measured with and without a masking stimulus (presented either to the same eye as the letters or to the other eye) before and after exposure of smokers and nonsmokers to 500 ppm carbon monoxide (CO) in air for 1 hr. Identification of the unmasked letters was not degraded by CO but a number of thresholds of the masked letters were significantly affected among the smokers. The effects of the CO on binocular and interocular masking were similar. These results suggest that the first effects of CO toxicity are neither on the receptors nor central but on the transmission lines in between and that smokers are more susceptible than nonsmokers to short-term increases in the level of CO. The masking phenomenon, however, does not appear to be an unusually sensitive measure of CO toxicity.
This study is an assessment of individual differences in electrophysiological response under diving conditions normally conducive to nitrogen narcosis. A group of 16 men made two dives each to approximately 200 ft in a pressure chamber while breathing air. The visual evoked response of the men at depth revealed several decrements; in the response to a slow rate of stimulation, there was a highly significant reduction in a component around 160 ms, and in the response to a rapid rate of stimulation, marked losses in amplitude and increases in variability were found. The latter changes were related to diving experience while the former were not. No significant changes were found in alpha or theta activity in the EEG.
Three Navy divers were exposed to a normoxic breathing mixture at 7.0 ATA for seven consecutive days. Visual evoked responses (VER's), electroencephalograms (EEG's) and simple reaction time (RT) were measured. Previously reported amplitude decreases in a VER to a flash rate of 1 Hz (VER 1) and to a flash rate of 16 Hz (VER 16) were again found during this dive. The variability of the VER 16 and the latency of the VER 1 also increased during the saturation period. In the EEG analysis, changes in the amplitude of both alpha and theta were found, as were decreases in alpha frequency. The RT task showed a marked elevation of response time at the beginning of the dive period which gradually returned to predive levels. Latency of the VER 160-180 ms component was highly correlated with the changes in RT. The results are discussed in terms of information processing and cerebral dysfunction.
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Distance and size estimates and stereoacuity judgments were made in water by divers, both with and without facemasks. Without the mask, only stereoacuity was markedly degraded. Distance estimates were slightly more accurate, despite a great decrease in the range of visibility. Size estimates were slightly too small. Divers with refractive errors did not appear to be more handicapped than those with normal vision.
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