ELECTROENCEPHALOGRAPHY 



By W. Grey Walter 



Director, Physiological Department 



Burden Neurological Institute 



Bristol, England 



[With 1 plate] 



The classical iDhilosophers took so little interest in the brain that 

 they referred to it merely as "the thing in the head." Until the last 

 century it was considered as providing a sort of radiator for over- 

 heated animal spirits; only in the last generation has the study of 

 brain function developed into a serious science. Microscopical ex- 

 amination of the brain tissue revealed that it contains about 10^° nerve 

 cells arranged in complex and systematic three-dimensional patterns. 

 Electrical stimulation of the exposed brain and observation of the 

 resulting movements and subjective sensations demonstrated the 

 anatomical connection betwen some parts of the brain and various 

 regions of the body, and it was found that, even when inactive, the 

 brain consumes an enormous quantity of energy in relation to its size. 

 Only in the last 20 years, however, has it been possible to study any 

 aspect of brain function directly in the intact human subject. It had 

 been known for a long time that communication between individual 

 nerve cells is maintained by brief electrochemical discharges along 

 nerve fibers, but it was not believed that electrical activity of the brain 

 could be detected without placing electrodes directly on the exposed 

 nerve tissue until Berger demonstrated this possibility in 1928. A 

 record of the electrical brain activity obtained in this way with elec- 

 trodes on the scalp is called the electroencephalogi-am or E. E. G. 



Such records show continuous electrical activity of an extremely 

 complex nature, consonant with the huge number of nerve cells and the 

 intricacy of behavior patterns. As recorded through the scalp and 

 skull, the potential differences of the electrical discharges are only a 

 few millionths of a volt and have to be amplified with specially de- 

 signed electronic devices that convert them into a continuous graph 

 drawn on paper. The possibility of studying the normal brain in this 

 way encouraged both clinical developments and the theoretical con- 



' Reprinted by permission from Endeavour, vol. 8, No. 32, October 1949 



243 



