The entorhinal cortex and a delayed non-matching-to-place task in mice: emphasis on preoperative training and...

This study examined the effects of ibotenate lesions of the entorhinal cortex (EC) on performance of a spatial recognition memory task, the delayed non-matching-to-place task (DNMTP), varying in level of difficulty according to the number of interpolated arm visits between sample-place presentation and subsequent recognition in mice. Results of experiment 1, designed to test the rate of acquisition of the task, showed that experimental animals were impaired in the basic non-matching task. However, with further training they were able to learn the task. Impairments were also observed when the amount of interpolating information inserted was gradually increased, and then all problem difficulties were pseudorandomly tested. There was no measurable recovery of function over time when the animals were retested on the task approximately 1 month later. Experiment 2 showed that the animals that received extensive training on the task prior to lesions of the EC were only transiently impaired in the DNMTP task. These data suggest that the EC plays an important role in acquisition rather than retention of the spatial recognition memory task.