252 ANNUAL REPORT SMITHSONIAN INSTITUTION, 195 



disturbed, near the site of a lesion, even when the resting activity 

 appears normal. 



In normal subjects, bright rhythmic flashes of light have been 

 found to evoke peculiar sensations at certain frequencies. All subjects 

 describe checkered, whirling patterns of light and shade when the 

 stimulus frequency is between 7 and 30 flashes per second, and most 

 see brilliant and ever-changing colors with white light. Some people, 

 again, describe vivid hallucinations and dreamlike experiences of 

 flying or of distortion of the time sense. Most interestingly, when- 

 ever a peculiar sensation is experienced, some part of the brain dis- 

 plays at the same time an unusual and exaggerated degree of electrical 

 activity at the frequency of the stimulus or a multiple of it. Further- 

 more, when, during an episode of this sort, the subject is encouraged 

 to submit to the sensation and to reinforce it with memories of a 

 similar type, both the sensation and its associated electrical discharge 

 are augmented. Conversely, when the subject is distracted by another 

 stimulus or, by an effort of will, refuses to accept the vision or state of 

 mind induced by the stimulus, both the subjective and electrical 

 phenomena subside. 



In some of the most striking examples of this effect, vivid and 

 emotionally powerful feelings have been correlated with electrical 

 responses in the temporal and frontal lobes, not at the stimulus fre- 

 quency itself, but at harmonics of it. In general terms, complex 

 individual mental disturbances can be set up by an apparently neutral 

 physiological stimulus when this is rhythmic and powerful enough, 

 and these mental states are strictly correlated with electrical events 

 in parts of the brain which have nothing to do with the reception of 

 visual stimuli. 



It will be recalled that unhappy children and bad-tempered adults 

 often show discharges at about 6 cycles per second in the temporal 

 lobes. It is at least very suggestive that when similar electrical dis- 

 charges are evoked in normal people by rhythmic stimulation, a feel- 

 ing of emotional discomfort and irritability appears. It would seem 

 logical to adopt, as a working hypothesis, the notion that certain 

 temperaments and states of mind are associated with electrical activity 

 at a particular frequency in certain nervous circuits within the brain, 

 and one can foresee a new meaning of the word "temper" as a strictly 

 scientific term to describe the tuning and resonance of these circuits. 

 In the testing of working hypotheses "the road of excess leads to the 

 palace of wisdom," and it may be necessary to develop a complete 

 theory of the relation between brain and mind in these electrical 

 terms before the appearance of absurd conclusions or predictions sig- 

 nals the inadequacy of our ideas. Even at the present time the in- 

 troduction of electrical terms and analogies has accelerated advance, 

 for it is now possible to use the methods of electrical engineers in the 



