338 Information Storage and Neural Control 



to the percentage time occupied during the previous ten seconds 

 by square waves which fell into a particular band. Reading" from 

 left to right between epoch markers, the first band of the minor 

 period is the percentage time of all minor period square waves 

 from one and one-half to ten cycles per second (equivalent fre- 

 quency). The second band of ten to twenty cycles per second has 

 been reduced from as high as 30 per cent time (full scale equals 

 50 per cent of full time) in portions of the pre-drug record to an 

 insignificant percentage during the epinephrine effect. The higher 

 frequency bands on the right of the spectrum have increased in 

 amplitude some 30 to 50 per cent. This sort of change we refer 

 to as a "shift to the right." It is characteristic of mild arousal 

 such as may be simulated by five micrograms intravenous epi- 

 nephrine per minute. The major period clearly shows a decrease 

 in band 4 as the alpha activity is suppressed and replaced by 

 higher frequencies and some delta activity. 



We suspect that level of sleep can be followed quantitatively 

 by a simple measure of the percentage delta time as well as more 

 precisely by the spectral epochs. We say "suspect," since to prove 

 that sleep can be fractionated into, say, fifty distinct levels would 

 require an independent measure of the state of consciousness having 

 the same order of resolution as the variable we are trying to 

 demonstrate. Unfortunately, we are unaware of a performance 

 measure or any other measure that allows quantitation of the 

 state of consciousness or state of arousal with as high resolution 

 as we think is possible with period analysis of the EEG. 



Several bioelectronic measures other than EEG may be amen- 

 able to period analysis or to some modification of the process. 

 Figure 6 shows the first derivative of the galvanic skin response 

 (GSR) signal as it is employed to generate square waves coinci- 

 dent with the onset-to-peak-amplitude time in the primary wave. 

 We regard the onset-to-peak-amplitude time as "active GSR 

 time" since it is the time of depolarization of the membrane which 

 is the effector site of this phenomenon. Automatic analysis of the 

 GSR produces two parameters of real importance in psycho- 

 physiological interpretation. The number of square waves gen- 

 erated per epoch, perhaps ten seconds or perhaps five minutes, 

 and the duration of the active GSR time for the given epoch are 

 partially independent parameters which seem worth considering 



