Heart-Rate Conditioning in Rats as a Function of Interstimulus Interval

Abstract

Classical aversive conditioning of heart rate in rats was studied using a 2 × 6 factorial design involving comparisons of trace and delayed conditioning procedures and six CS-US intervals (.0, .1, .3, .5, 1.0, and 6.0 sec.). Positive evidence of decelerative HR CRs was obtained at the .5, 1.0 and 6.0 ISIs, with maximum conditioning occurring at the 6.0 value. The results supported a modified version of the temporal gradient of reinforcement theory of classical conditioning. Problems relating to the separation of true CRs from nonassociative reactions to the CS were also discussed.