Reward magnitude shift effects in rats with hippocampal lesions.

Abstract

Studied 32 normal male hooded rats and 60 with either hippocampal or neocortical lesions. Ss received 60 runway training trials under 12- or 1-pellet reward and then 42 trials under the original or the opposite magnitude. Over the 1st 60 trials, performance levels increased reliably with reward magnitude for each surgical condition; no reliable differences occurred among conditions. Following reward change neocortical and normal ss showed reliable negative contrast effects under decreased reward and performance similar to 12-pellet controls under increased reward. Hippocampally damaged ss showed nonsignificant performance changes following reward change. Their postshift performance was a reliable direct function of initial reward magnitudes. (17 ref.) (PsycINFO Database Record (c) 2006 APA, all rights reserved)