Perirhinal cortex damage and anterograde object-recognition in rats after long retention intervals.

Damage to the perirhinal cortex (PRh) in rats impairs anterograde object-recognition memory after retention intervals of up to several hours, but there is little direct evidence to link PRh function to object-recognition abilities after substantially longer intervals that span several days or weeks. We assessed the effects of PRh lesions on anterograde object recognition using a novel-object preference test, with retention intervals lasting 24 h and 3 weeks. The rats received multiple exposures to the sample object during the learning phase--5 min per day on 5 consecutive days.

Enhanced context-dependency of object recognition in rats with hippocampal lesions.

Object recognition memory was assessed on a novel-object preference (NOP) task in rats with lesions of the hippocampal formation (HPC). The learning and test phases of NOP trials occurred in either the same context or in different contexts. When the learning and test contexts were the same, rats with HPC lesions performed like control rats, displaying a significant tendency to investigate a novel object more than a familiar sample object.

Retrograde amnesia following hippocampal lesions in the shock-probe conditioning test.

The present experiment examined the role of the hippocampal formation (HPC) in long-term memory of an association between an object and a fear-eliciting event. Rats either received sham or neurotoxic lesions of the HPC 1 or 14 days after learning that contacting a wire-wrapped probe (i.e.

Hippocampal damage and anterograde object-recognition in rats after long retention intervals.

Although several studies in rats have found that hippocampal damage has negligible effects on anterograde object-recognition memory, the findings are not entirely conclusive, because most studies have used retention intervals lasting only a few hours. We assessed the effects of neurotoxic hippocampal lesions on anterograde object recognition, using a novel-object preference test, with retention intervals that were considerably longer than in previous studies-24 h, 1 week, and 3 weeks. To promote object recognition after such long intervals, rats were familiarized with a sample object in an open field for 5 min/day for 5 consecutive days.