Time course of cardiac conditioned responses in restrained rats as a function of the trace CS-US interval

Author(s): Kamper, E.

Journal/Book: J Exp Psychol Anim Behav Proc. 2000; 26: 750 First St NE, Washington, DC 20002-4242, USA. Amer Psychological Assoc. 385-398.

Abstract: Two experiments aimed at understanding the temporal characteristics of trace-conditioned heart-rate responses to a 0.5-s tone (conditioned stimulus [CS]) in restrained rats. A CS paired with a tail-shock (unconditioned stimulus [US]) elicited lasting bradycardiac responses. The magnitude and extinction rate of conditioned responses (CR) were independent of the CS-US interval (interstimulus interval [ISI], 3 s to 20 s). Unreinforced test trials were analyzed for CR topogaphy. Responding was delayed in groups with longer ISIs, but CR latencies, peak and decay times were not proportional to the ISI. Response peaks tended to cluster either about 6 s after CS onset, or about 10 s with a slow decay, depending on the ISI. The authors postulated 2 components of auditory stimulus traces involved in cardiac conditioning, maximally active 6 s and 10 s respectively after CS onset. The topography of the CR could be constrained to combinations of associative strength and instantaneous activity of these 2 components.

Note: Article Marchand AR, Univ Strasbourg 1, CNRS, Lab Neurosci Comportementales & Cognit, UMR 7521, 12 Rue Goethe, F-67000 Strasbourg, FRANCE

Keyword(s): SCALAR TIMING THEORY; HEART-RATE; TEMPORAL DISCRIMINATION; REAL-TIME; MODEL; FEAR; STIMULUS; DURATION; MEMORY; HIPPOCAMPAL

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