Immediate-startle stimulus presentation fails to condition freezing responses to contextual cues.

Placed 28 male Wistar rats in a novel and distinctive environment. 18 of these received an intense startle-eliciting white noise stimulus. Animals that experienced a 60-sec delay between placement and the startle stimulus demonstrated significant freezing in the context, both poststartle (Session 1) and on a later startle-free test (Session 2). Animals that received immediate startle, however, did not differ on either occasion from animals that did not experience the startle stimulus. The amplitude of the startle response was not affected by this manipulation, which indicates a dissociation between freezing and startle responses with immediate- vs delay-startle presentation. The findings are consistent with M. S. Fanselow's (1986) conditioned stimulus (CS)-based associative explanation of the immediate-shock freezing deficit. (PsycINFO Database Record (c) 2010 APA, all rights reserved)