Retrograde amnesia and selective damage to the hippocampal formation: memory for places and object discriminations.
Using a within-subjects design, rats were trained on two place-memory problems and five object-discrimination problems at different intervals prior to receiving either ibotenate lesions of the hippocampal formation or sham surgery. Places # 1 and 2 were fixed-platform water-maze tasks that were run in different rooms and they were learned during the 14th and 2nd week before surgery, respectively. Object-discrimination problems # 1-5 were learned during the 13th, 10th, 7th, 4th, and 1st week before surgery, respectively. Rats with hippocampal lesions displayed impaired retention of both Place problems with no evidence of a temporal gradient to the impairment. In contrast to their retrograde place-memory deficits, the hippocampal rats displayed normal retention of the five object-discriminations that were learned before surgery. Hippocampal lesions had similar consequences for anterograde learning, as the lesioned rats were impaired in acquisition of a new water-maze problem that was run in a third room (Place #3), whereas they showed normal acquisition of two new object-discriminations. The findings indicate that the hippocampal formation is not required for long-term consolidation of information underlying accurate performance of object-discriminations, and that its critical role in memory for places persists for at least 14 weeks, and probably for as long as those memories exist.
Mumby
D G
DG
Department of Psychology, Concordia University, Montreal Que, Canada. mumby@vax2.concordia.ca
Astur
R S
RS
Weisend
M P
MP
Sutherland
R J
RJ
D000648:Amnesia, Retrograde / Q000139:chemically induced / Q000523:psychology*; D000818:Animals; D018891:Dentate Gyrus / Q000187:drug effects / Q000502:physiology; D004192:Discrimination, Psychological / Q000187:drug effects / Q000502:physiology*; D018690:Excitatory Amino Acid Agonists / Q000633:toxicity; D006624:Hippocampus / Q000187:drug effects / Q000502:physiology*; D007051:Ibotenic Acid / Q000633:toxicity; D008297:Male; D008568:Memory / Q000502:physiology*; D051381:Rats; D020318:Rats, Long-Evans
D018690:Excitatory Amino Acid Agonists; D007051:Ibotenic Acid