INTRINSIC RHYTHMS OF THE BRAIN 



283 



FIG. I. Spontaneous electrical discharges in single cells of lobster cardiac ganglion. The wave 

 form is suggestive of a relaxation oscillation vifith two separate time constants. .4 and B are from the 

 same cell in the lobster. It shows a large pacemaker potential, presumably arising nearby, and an- 

 other prepotential before the spike. This can fail to elicit a spike, can continue (end of .-1) or redevelop 

 (third spike of Bj after the spike, and can initiate repolarization almost as complete as a spike can. 

 Note the failure of the prepotential to arise following the third spike in B, with instead an undulation 

 leading to a new cycle. C, D and E are three different crab cells of type D, showing different forms 

 and permutations of pacemaker potential and repolarization. Scales: A, B, 500 msec; C, D and E, 

 50 mv, 200 msec. [From Bullock & Terzuolo (14).] 



confirmed the early olsservations of Pa ton (45) and 

 Wintrebert (68) that in embryonic clasmobranchs 

 spontaneous rhythmic activity of the mu.sculature is 

 entirely myogenic in origin. A tendency to repetitive 

 activity seems to be intrinsic in many excitable struc- 

 tures and, indeed, absence of spontaneous discharges 

 may be a special case of control or inhibition. In 

 primitive or embryonic organisms the intrinsic 

 rhythms are generally little affected by external 

 stimuli, whereas in more highly developed structures, 

 such as the human brain, responsiveness to stimula- 

 tion is the general rule. 



This difference suggests that, as in other living 

 structures and functions, a basic mechanism which 

 survived the first stages of evolution because of its 

 simple utility may, as it were, be exploited in the 

 later stages of specialization to fulfill a much more 



elaborate function. As a crude working hypothesis, we 

 may consider that the rhythinic properties of primi- 

 tive creatures and rudimentary organs, which at 

 first provided a simple means of propulsion, have in 

 our own brains assumed an essential role in the 

 systematic timing and distribution of information 

 within the neuronic network. 



Intrinsic Rhythms in the Human Brain 



For the purpose of this chapter, attention will be 

 directed mainly to the rhythmic activity of the human 

 brain. This has received the greatest attention since 

 the discovery of Hans Berger of the human electro- 

 encephalogram (9); the observation and measurement 

 of the rhythmic features of the human EEG have been 

 practised on an increasing scale for 20 years in several 



