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Information Storage and Neural Control 



in the interpretation of states of arousal. Figure 6 also illustrates 

 the use of a "period filter" (digital filter), which is analogous to a 

 resonant frequency filter in the frequency domain, but which does 

 not have the inherent disadvantages of time lag for energy buildup 

 and decay. If the square wave is of less than five milliseconds dura- 

 tion in the case of EEG and of less than one second duration 

 for the GSR, the period filter will not "pass" it for further proces- 

 sing. The GSR recording is often plagued by relatively high 

 frequency noise from movement artifact. In a noisy record this 

 high frec^uency artifact may produce as much as 85 per cent of 

 the square waves. It is a great convenience to be able to "filter" 

 them out. 



While the system just described is of real practical value in the 

 analysis of the GSR activity of a single subject, it is indispensable 

 to the "coincidence" analysis of GSR's from four subjects in group 

 interaction. Figure 7 is a record of this type of analysis in which 



The ESToajNE-ANGus Co 



Fig. 7. Coincidence Analysis of Group GSR. Lines two through five show the square 

 wave trains generated by the baseline cross of the first derivative of the GSRs 

 recorded from Subjects A through D. The coincidence, or overlap, of "active" 

 GSR time between all pairs of subjects is shown in lines six through twelve. 

 Three of a "kind" and four of a "kind" can be seen in lines thirteen through 



seventeen. 



