Extended temporal gradient for the retrograde and anterograde amnesia produced by ibotenate entorhinal cortex lesions in mice.
Effects of ibotenic entorhinal cortex (EC) lesions on both retrograde and anterograde amnesia in mice were assessed using two-choice discrimination tasks learned at different intervals before surgery in two eight-arm radial mazes. The results indicated that EC-lesioned mice were severely impaired in postoperative retention of discrimination problems learned 3 d or 2 weeks prior to surgery, but showed no deficit on problems learned between 4, and up to 6 weeks before surgery, as compared to sham-operated controls. When trained on a novel two-choice discrimination problem (not acquired preoperatively), experimental subjects demonstrated quite normal rates of acquisition, but were impaired in learning its reversal. Furthermore, they exhibited a faster rate of forgetting (anterograde amnesia) relative to controls over a 2-week retention interval. These results indicate that approximately 4 weeks is required before memory for a two-choice spatial discrimination problem no longer depends on the integrity of the entorhinal cortex, and suggests that, beyond this time, an EC-independent memory storage system is capable of supporting the retrieval of information. The data, together with complementary behavioral results, are discussed in the context of current theories of memory storage.
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Laboratoire de Neurosciences Comportementales et Cognitives, CNRS URA 339, Université de Bordeaux I, Talence, France.
Beracochea
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Jaffard
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D000647:Amnesia / Q000145:classification / Q000209:etiology* / Q000523:psychology; D000818:Animals; D001522:Behavior, Animal / Q000502:physiology; D002755:Choice Behavior / Q000502:physiology; D003463:Cues; D004192:Discrimination, Psychological / Q000502:physiology; D007051:Ibotenic Acid / Q000494:pharmacology*; D007858:Learning / Q000502:physiology; D008032:Limbic System / Q000187:drug effects*; D051379:Mice; D008807:Mice, Inbred BALB C; D009043:Motor Activity / Q000502:physiology; D012153:Retention, Psychology; D013997:Time Factors
D007051:Ibotenic Acid