Non-random oscillation in the response-duration curve of electrographic activation

Abstract

The response-duration curve for the alpha-blocking response to a bright double flash of light was studied in 25 normal subjects. Each individual was subjected to 60 stimulus presentation on six separate occasions, five of them under various drugs and one under a placebo. Data for the placebo and for methamphetamine are presented. The curve of mean duration of alpha blocking (placebo) for 60 trials indicated a roughly exponential decrement between trials 1 and 29. From trial 30 on to 37 there was a steady increase in mean values, followed by a second decrease and then a second increase in the last five trials. The curves for individuals revealed more marked oscillation but slight differences in phasing and frequency resulted in a smoothed curve for the whole population. Nevertheless, 16 of the 25 subjects had a periodicity precisely concordant with that in the mean data. Amphetamine produced a striking increase in mean response duration with stimulus repetition. However, marked oscillations were observed in over one-third of the cases; the remainder showed changes in rate of increase which, on a mean plot, also suggested the presence of an oscillatory process. The data indicate that within the time and parametric limits of this experiment there is a non-random oscillatory process affecting alpha-blockade response duration which is superimposed upon the habituation curve. Recognition of this oscillation may be important in assessing the effect of drugs or other procedures on the pattern of habituation.