CORTICAL LOCALIZATION OF SYMBOLIC PROCESSES IN THE RAT: II. EFFECT OF CORTICAL LESIONS UPON DELAYED ALTERNATION IN THE RAT

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Abstract
The purpose was to determine whether or not there are limited areas in the cortex of the rat which subserve symbolic processes, and in particular recent memory, as has been found to be the case in primates. In a T-maze in which rats spontaneously alternate, 17 rats were run for 60 trials each, pre- and postoperatively. Between each trial there was an interval of 15 secs, and single alternation significantly greater than a chance level of 50% was taken as an index of recent memory. Following completion of postoperative tests brains were removed and the size and location of lesions reconstructed upon standard diagrams. The majority of the lesions were in either the prefrontal or the occipital areas. Animals with the prefrontal lesions, except for one with a superficial injury, lost their ability to use recent memory, whereas those with occipital lesions showed little difference in performance. Too few "pure" motor lesions were available to determine whether these also affect recent memory. Parietal lesions gave inconsistent results. Some "localization" of recent memory in the anterior cortical areas of the rat is definitely indicated by this study, but more work is required to tell how precise it is.