CS duration and reinforcement schedule effects on conditioned enhancement and positive conditioned suppression

Abstract

Two groups of rats learned a discrimination in which responses were reinforced on a variableinterval (VI) schedule during one stimulus and extinguished during another. Eight conditioned stimuli (CSs), each followed by a food unconditioned stimulus (US), were presented during each session: four during the VI component and four during the extinction component. CS duration was 2 min for Group L and 30 sec for Group S. Subjects in both groups responded at higher rates during CSs presented in the extinction component. Group L subjects also responded at higher rates during VI-component CSs, but Group S subjects responded at lower rates during VI-component CSs. These data indicate that reinforcement schedules may affect rate changes during CSs only within a limited range of CS durations.