Previously we reported a learned irrelevance-type retardation in appetitive signaled barpressing (SBP) that appeared to be dependent on the hippocampus and associated cortical structures (Miller, Doherty, Chapleau, & Allen, SFN Abstracts, 2000). Rats receiving hippocampal lesions followed by 10 d of 100 pre-exposures/d to a 1 sec tone that was uncorrelated with performance on a FR-8 reinforcement schedule showed a significant delay in learning to press a bar during the 1 sec tone presentation for food pellet reinforcement. This retardation was reversed in rats with non-selective hippocampal lesions. Allen and Gluck (SFN Abstracts, 1998) demonstrated that selective lesions of the entorhinal cortex but not the hippocampus abolished learned irrelevance in rabbit eyelid conditioning. In the current study we delivered the pre-exposure sessions prior to performing hippocampal lesions followed by SBP training after recovery from surgery. We hypothesized that tone pre-exposure with the hippocampus intact would all...