Effects of time uncertainty on the time-course of preparatory processes in cats performing a RT task

Abstract

The temporal distribution of preparatory patterns for action has been studied in 8 cats which performed a reaction time (RT) task. The signal for the response (SR) occured after one of four equiprobable preparatory periods (PPs) of variable duration (0.5 sec, 1.0 sec, 1.5 sec, 2.0 sec). The RTs and the “anticipatory responses” (ARs) preceding the SR occurence are analysed in two different procedures in order to compare the performances obtained with and without a clock functioning during the PP. The results are interpreted in terms of a descriptive model according to which the preparatory level is related to the conditional probability of the SR occurence. In the procedure without a clock, both a negative slope of the RT—PP length relation and a positive slope of the AR—PP length relation generally appear in the course of learning. The clock leads to a decrease of the slope of the RT—PP length relation on the one hand, and to a multimodal distribution of the ARs from the preparatory signal to the end of the longest possible PP duration on the other hand. The strategies used by the animals to perform the RT task, and the differences as compared to human performances are discussed.