5 



Electrical Potentials of 

 the Brain 



I. Electroencephalography 



Electroencephalography is a study (or graphing) of the electrical poten- 

 tials on the surface of the head. In terms of its derivation, electro- 

 encephalography (electro + encephalon + ography) could refer to any 

 electrical potentials of the head. Actually, it is restricted to those 

 potentials, other than neuron spikes, that are associated with the brain's 

 action. At the outer surface of the scalp, these electroencephalographic 

 (eeg) x potentials are small compared to the potentials due to the heart- 

 beat and are comparable to the potentials associated with the motion 

 of the muscles controlling the eye, jaw, neck, and so on. The small 



1 Throughout this chapter, the abbreviation "eeg" will be used as an adjective 

 or noun as appropriate, to refer either to these potentials, to the recording appara- 

 tus, or to the graphic record of these potentials as a function of time. The eeg 

 potentials arise from the action of nervous tissue. The student will find it profit- 

 able to have read thoroughly the preceding chapter before starting this one. A 

 knowledge of that material is presupposed in this chapter. 



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