Abstract
The open field behavior of Sprague-Dawley rats and mongrel cats was tested daily prior to and following bilateral entorhinal cortical lesions. The subjects were tested postoperatively from Days 2 to 17 and the time course of behavioral changes following the lesions was assessed. Total activity and decline (habituation) in activity across successive minutes of each test session were recorded as the measures of open field behavior. Rats with bilateral entorhinal cortex lesions exhibited a dramatic increase in total activity which peaked on Day 4, paralleled by a slower habituation of activity within single test sessions. The increased total activity and slower habituation across minutes were most pronounced during the early postlesion interval, exhibiting some return toward control levels with time, but never attaining control values. To determine whether the return toward control levels was time dependent or a result of the repeated testing design, other groups of rats with bilateral EC lesions were tested beginning 10 and 14 days postlesion. These rats exhibited lower levels of total activity and a more rapid habituation across minutes than was observed in the group tested between 2 and 8 days postlesion. Thus, the return toward control levels was time dependent and not a result of the repeated testing. Cats with bilateral entorhinal cortex lesions also exhibited an increase in total activity and a slower habituation in successive minutes of a test session. Again, both effects were most pronounced during early postoperative intervals, approaching but not attaining control levels with time. The nature and time course of these changes were virtually identical in the two species. The similarities in the nature and time course of the behavioral changes in the rat and the cat are discussed with regard to the possible relationship between reactive changes in the brain and the time-dependent behavioral changes.
Published Version
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