1.88 



II VNUBOOK Oh 1'IIVsIl il ( K.Y 



NKl'ROPHYSIOLOGY III 



SLIDING 

 DOOR 



PARTIALLY 

 RAISED 



TACHISTOSCOPE 



-V- \ — J ACTIVATES 

 \ \ TIMER 



40 30 20 10 40 30 



DURATION OF EXPOSURES (msec) 



fig. 17. Percentage of correct response and mean reaction 

 times as a function of tachistoscopic exposure duration. Cor- 

 rect responses increased and reaction times decreased during 

 reticular stimulation (solid lines). Each point represents 100 

 trials. [From Fustcr (83).] 



fig. 16. Visual-discrimination reaction-time apparatus. 

 Monkey is trained to discriminate objects for a reward, then 

 allowed to see the objects only during a brief tachistoscopic 

 flash. The light starts the clock timer; the monkey's choice and 

 reaching through the door stops the clock, so giving the reac- 

 tion time. [From Fuster (83).] 



Although comparatively few studies in the EEG 

 field deal with hypnosis, those that have been pub- 

 lished (15, 27, g8, 168, 171, 232) are in general 

 agreement for the most part. In a waking trance, the 

 EEG in hypnosis docs not differ significantly from 

 that of the same person in a normal waking slate. 

 The EEG does nol resemble the KEG in sleep unless 

 a subject in a trance has been allowed to sjo to sleep 

 or deliberately put to sleep by suggestion. With the 

 general relaxation which occurs during hypnotic 

 episodes, there is sometimes an increase in alpha 

 activity, or ,1 falling oil if slighl drowsiness supcrv cues. 

 Unless .1 special suggestion is made requiring efforl 

 mi tension, there is no tendency for the EEG to show 

 activation. In general then it can be said thai the 

 EEG in hypnosis is similar to that during waking. 

 Under hv pilosis the KE( • lends 10 parallel that during 

 normal stales and, if the hypnotic subject is required 



to sleep, he has a sleep EEG; if he is required to 

 soke a problem, his EEG resembles thai when he is 

 not under h\ pnotic influence. 



The efficacy of suppressing pain reactions under 

 hypnosis, or of obliterating cognizance to one scum- 

 mode in deference to another, suggests a similarity ol 



this aspect of hypnosis to selective attention under 

 normal conditions. Loomis et al. (168), however, 

 found that inserting a pin into the arm of a hypnotized 

 subject, after repeated suggestions that he would feel 

 nothing, produced effective alpha blocking lasting 28 

 sec. Repeated trials produced less effective blocking. 

 The threat to insert the pin into the arm but without 

 actually doing so had no effect on the alpha waves, 

 even when the suggestion was made that the pin was 

 in the arm and painful. Thev also observed that 

 alpha waves were present during hypnosis as before, 

 and that opening and closing the eyes caused alpha 

 blockade as prev iouslv . 1 lowcv er, w hen they suggested 

 that the subject was blind in the presence of Light, 

 the alpha waves were not blocked. This result differs 

 from that obtained by others (27, 171, 232), all of 

 whom found that negative suggestion was ineffective 

 in reversing the usual alpha-blocking reaction to Light. 

 Comparatively little progress has been made 

 electroencephalographically or neurophysiologically 

 in coming to grips with the mechanism which might 

 underlie hypnosis and hypnotic phenomena. Ac- 

 cording lo Barber (141 hvpnosis is not a "slate of 

 consciousness" Il is nol a •'thin',;" or an "entity." 

 "ilvpnosis is a descriptive abstraction referring 10 an 

 interpersonal relationship which i^ characterized by 

 a number of overlapping processes." 1 Le sees \w pnotic 

 phenomena as extensions of normal modes and man- 

 ners of behaving and reacting, but under the influence 

 of strong "belief" in the hypnotist's influence. Al- 

 though he strongly emphasizes that hvpnosis is not 



