336 Information Storage and Neural Control 



does this well on a simple wave, what may be expected from the 

 rather more complex signal of the electroencephalogram? 



Figure 4 shows that the electroencephalogram is not recon- 

 stituted as successfully as the simple mixed sine waves. Some of 

 the amplitude modulation features are lost, the envelope is not 

 as clearly evident on the reconstituted signal, and some phase 

 shift is apparent as distortion in a number of the waves. Here again, 

 however, the resemblance of the reconstituted wave to the original 

 one is rather striking. The clinical electroencephalographer would 

 probably interpret the reconstituted EEG in much the same way 

 as he would the original, and would render much the same clinical 

 impression after reading the reconstituted forms. 



Interpretation of the major and minor periods may be accom- 

 plished in the same way as interpretation of an EEG but with 

 less equivocation. Anyone who has attempted to reduce, quantita- 

 tively, long stretches of EEG record by any form of hand analysis 

 will appreciate the significance of this. The square waves may be 

 further processed and displayed in several difTerent ways, depending 

 on the physiological event under investigation. One system we 

 have used quite extensively distributes the major and minor 

 periods in a ten second epoch over ten bands in the major period 

 and ten bands in the minor period. Table I defines the bands we 

 are currently using in terms of equivalent frequency. A square 

 wave of the same duration as the square wave generated by an 

 eight cycle per second sine wave falls into band 4 of the major 

 period and band 1 of the minor period. The major period bands 



TABLE I 



Band Distribution (As Equivalent FREquENCv) Currently Being Used 



IN "Spectral Display" of the Square Wave Trains Generated by the 



Process of Period Analysis 



