PHYSCHOPHYSIOLOGICAL FINDINGS 241 



PROCEDURE 



All but foul- of the 28 subjects were evaluated at the research unit at some time between 9 

 and 59 days before diving. The postdive examinations were done from 12 to 36 hours after 

 completion of approximately 30 hours of decompression. In addition to the neurological exam- 

 ination, EEG and autonomic variables (heart rate, HR, respiration rate, RR, finger pulse re- 

 sponse, FPR, galvanic skin response, GSR, and basal skin resistance) were obtained. The 

 autonomic variables were scored for basal levels, spontaneous fluctuations in basal activity, 

 and response to stimuli. The methods of recording and scoring these variables have been 

 previously reported (Johnson (9, 10). 



The pre and postdive neurological examinations included assessment of the cranial nerves, 

 motor system, sensory system, cerebellar function, gait, and station, and they also included a 

 screening test for aphasic signs. The subjects were also asked to subtract 7 serially from 

 100, repeat numbers both as read and in reverse, name the five most recent presidents and 

 vice-presidents, and interpret two proverbs. 



During the EEC, each subject was stimulated by means of a Grass Model PS-2C photic 

 stimulator from 5 to 20 ops and asked to breathe deeply and rapidly (hyperventilate) for three 

 minutes. The EEGs were interpreted by the neurologist as being either normal or abnormal. 

 A normal EEG record was defined as having: 



1. Rhythmic and arrhythmic activity at 8 to 13 cps with asymmetry up to one-half the volt- 

 age side 



2. Rhythmic beta activity regardless of the amplitude excepting focal beta 



3. Fronto-temporal theta of less than maximal alpha amplitude, occupying less than 2 per- 

 cent of recording time, but no focal theta or asymmetry of more than one-half the alpha 

 amplitude 



4. Variable low amplitude fast activity 



5. Any amount of drowsiness or sleep. 



RESULTS 



Electroencephalogram 



All predive EEGs during resting, waking, activation, and periods of sleep were interpreted 

 as being within the criteria for normal as defined above. The postdive records were distin- 

 guished by more rapid onset of sleep and the appearance of large amounts of spindle stage and 

 slow-wave sleep. One subject's postdive record, because of a marked buildup of slow waves 

 during hyperventilation, was read as abnormal. As this subject has not eaten in the six to 

 seven hours preceding the recording of his EEG, he was brought back to the laboratory after 

 fasting for some 15 hours to determine if the responses were due to hypoglycemia. The same 

 response to hyperventilation was observed. He was then given 25 grams of sugar in orange 

 juice. Hyperventilation 15 minutes after the ingestion of the glucose failed to produce the 

 slow-wave activity. It was therefore concluded that the response to overbreathing seen on his 

 postdive record was a result of fasting and not to his stay in Sealab n. 



Neurological 



Minor neurological abnormalities were found in seven individuals on initial examination. 

 In five men one of the following was found: (a) alternating exotropia and difficulty intei-preting 

 proverbs; (b) hyperactive left knee jerk (residual of a previous decompression left hemi- 

 paresis); (c) unilateral optic atrophy with an abnormal visual field in that eye; (d) cerebellar 

 ataxia of a mild degree with finger to nose intention tremor and ataxic handwriting; or (e) ex- 

 tremely slow mental responses with apparent confusion. Unilateral neurosensory hearing loss 



