248 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1950 



though they are usually localized round the lesion, these slow, abnor- 

 mal delta waves are quite similar to those found in infants and deep 

 sleep, suggesting that they may have some function in assisting the 

 disturbed nervous tissue to rest from its labors, in the same way as 

 pain compels disuse of a broken limb — for the brain can feel no pain, 

 and has little power of healing itself. 



The most dramatic variations from the normal are seen in epileptics, 

 particularly during seizures. In petit mal, for example, when the 

 patient suddenly becomes unconscious for a short time, the whole 

 brain generates enormous regular slow waves a hundred times bigger 

 than any normal rhythm, each one with a short spike indenting its 

 crest (fig. 6). One may consider a patient generating these "wave 

 and spike" rhytlims, as they are called, as being electrocuted by his own 

 brain. 





Figuke 4. — Electroencephalogram from a S-year-old child showing prominent 

 theta activity combined with alpha. A similar record might be found in an 

 adult with marked aggressive tendencies. 



Though always interesting and sometimes useful in the study of 

 organic brain disease and epilepsy, the technique of electroencephal- 

 ography has been too crude to give much help in problems of mental 

 disorder, or in the investigation of the physiology of behavior. In 

 the last few years, however, the technical resources available to electro- 

 physiologists have been greatly extended by the adoption and adapta- 

 tion of devices developed during the war for radar or "servo" ma- 

 chinery. Some new instruments, on the other hand, have been 

 specially designed by those working in the field for their own peculiar 

 problems. 



The advance has been made on two fronts : first, the development of 

 elaborate and flexible methods of transformation and display of the 

 electrical data; second, the introduction of controlled stimulation of 

 the subject. It will be realized that the ordinary record is really a 

 graph of voltage against time, but since there are inevitably large 

 numbers of cell groups active at the same moment, this graph is nearly 

 always extremely complex and bewildering to the eye, which can pick 



