Reward magnitude shift effects in rats with hippocampal lesions

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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)

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