Perspectives on object-recognition memory following hippocampal damage: lessons from studies in rats

One of the routine memory abilities impaired in amnesic patients with tempo ral-lobe damage is object-recognition memory-the ability to discriminate th e familiarity of previously encountered objects. Reproducing this impairmen t has played a central role in animal models of amnesia during the past two decades, and until recent years most of the emphasis was on describing how hippocampal damage could impair object recognition. Today most investigato rs are looking outside the hippocampus to explain the impairment. This pape r reviews studies of object-recognition memory in rats with hippocampal dam age produced by ablation, fornix transection, or forebrain ischemia. Some n ew perspectives on previous findings reinforce the conclusion that damage t o the hippocampus has little if any impact on the ability to recognize obje cts, while damage in some areas outside the hippocampus is far more effecti ve. The few circumstances in which hippocampal damage can impair performanc e on object-recognition tasks are situations where ancillary abilities are likely to play a significant role in supporting task performance. Some of t he factors that contributed to the origins and persistence of the hippocamp alcentric view of object-recognition are considered, including lesion confo unds, failure to distinguish between impaired task performance and impairme nt of a memory ability, and disproportionate attention to a few lesion stud ies in monkeys, even though the hypothesis was tested far more times in rat s, under a greater variety of conditions, and rejected on nearly every occa sion. (C) 2001 Elsevier Science BN. All rights reserved.