I 5 82 



IIVMHiOOK OF PHYSIOLOGY 



NEUROPHYSIOLOGY III 



blocked, until very large slow waves developed a 

 locked pattern. The return of consciousness was 

 correlated with the breaking up of the slow wave 

 pattern, but did not become clear until some alpha 

 waves returned. 



Voluntary overbreathing or hyperventilation car- 

 ried on from 2 to 4 min. will often induce delta 

 waves of increasing magnitude in normal subjects. 

 In 15 experiments the Davises reported consistent 

 results, with modification of consciousness as the 

 high-voltage delta waxes became persistent. Subjects 

 failed to respond to commands, although one reported 

 hearing the command and said afterward he was 

 unable to comply. If hyperventilation were carried 

 further, it is quite likely that a complete loss of con- 

 sciousness would occur. 



In connection with Metrazol seizures which had 

 been induced in a schizophrenic patient who had a 

 normal control EEC), it was found that the patient be- 

 came unconscious when convulsions associated with 

 high-voltage fast waves set in. Lack of consciousness 

 persisted through the subsequent low-voltage, rela- 

 tively isoelectric period following the cessation of clonic 

 convulsions, and through the high-voltage delta wave 

 period in which waves gradually became better 

 organized and more regular. Consciousness was re- 

 Stored when the electrical activity finally returned to 

 normal frequency ranges. Thus unconsciousness oc- 

 curred in this instance during high-voltage fast waves, 

 but continued through two or more patterns of slow 

 waves of diverse type. There is always the possibility, 

 however, that unconsciousness which occurs during 

 the fast high-voltage stage in a major seizure shifts into 

 a prolonged period of sleep with slow waves from 

 which the patient eventually arouses. Thus, the slow 

 w.imn following a convulsion may literally be deep 

 sleep waves which are also accompanied by uncon- 

 sciousness. But some patients cannot be as readily 

 aroused from such ,1 stage as can a normal person 

 with similar patterns in .1 stage of deep sleep. 



following coma-producing injections of insulin in a 

 schizophrenic patient, it required better than an 

 hour before all alpha waves disappeared and low - 



voltage delta waves replaced them Ai this point the 

 patient was asleep with obvious loss of const lonsness 



In about >, hr. verv large I -to-j-per-sec. slow waves 

 in a lot ked pattern appeared and continued dining 

 the remainder ol the coma, which was cleared in 1 1 

 min. bv an injection of glucose. Forty min. following 

 glucose the EEG was approaching normal and con- 

 st iousness w as restored. 



|)eep ether and deep alcoholic intoxication both 



produce large slow delta waves in their unconscious 

 anesthetic and stuporous phases, respectively. Ether 

 initially produces a shift from alpha waves to a fast 

 activity before giving way to delta wave activity of 

 larger and slower nature. Alcohol initially enhances 

 alpha activity, then diminishes and slows it; but no 

 marked changes occur until deep intoxication is 

 reached when the pattern becomes a more or less 

 continuous moderate to high-voltage delta wave 

 activity. 



SEIZURE PATTERNS Willi MODIFICATION OF CONSCIOUS- 

 NESS. Figure 12 illustrates a spontaneous grand mal 

 or major seizure pattern in a young man 19 years of 

 age. The entire seizure is shown except for the pro- 

 longed terminal sleep phase. The attack began with 

 an increase in the voltage of alpha and other activity 

 (at arrow, fig. 12). At the point marked tomi phase the 

 patient's limbs and body assumed a rigid extensor 

 position, and his EEG showed a further increase in 

 voltage and amount of fast activity. About 5 sec. 

 after the onset of the tonic phase, when high-voltage 

 fast activity was still marked, consciousness was lost. 

 The tonic phase gradually shifted to a clonic jerking 

 phase, and as this subsided there was a period of flat, 

 isoelectric record which ushered in the complete 

 relaxation of the comatose phase. Alter some seconds 

 random slow waves began to return and this picture 

 persisted for some time, gradually forming more 

 regular delta waves which eventually disappeared in 

 about 30 min., the EEG returning to near normal. 



Figure [3 shows a major seizure induced bv electro- 

 shock in which essentiallv the same pattern is exhibited 

 as in the naturally occurring grand mal seizure shown 

 above Again consciousness was lost at or near the 

 start of the tonic phase. The sequence of tonic extensor 

 phase with high-voltage fast activity, followed bv 

 clonic convulsions with slowing of waves 10 correspond 

 to rate of jerking, isoelectric record corresponding to 

 the relaxed comatose phase, and finally continued 

 relaxation with development of random slow waves, 

 is characteristic of both the induced and natural 

 major attacks. Unconsciousness merges with sleep 

 at the end, ami the arousal and preseizure EEG 



pattern ina\ not return for 1 ;, min. to an hour or 

 more. 



In contrast to the major seizures, figure 1 1 shows a 

 petit mal or minor attack, with characteristic spike 

 and slow wave pattern lasting u to [5 sec. with no 

 behavioral change other than opening of the eves and 

 staring straight ahead. Such an attack usually 

 indicates an 'absence' or momentarv 'blank-out,' 



