EFFECTS OF DISCRETE KAINIC ACID-INDUCED HIPPOCAMPAL-LESIONS ON SPATIAL AND CONTEXTUAL LEARNING AND MEMORY IN RATS

Substantial information is available concerning the influence of globa l hippocampal lesions on spatial learning and memory, however the cont ributions of discrete subregions within the hippocampus to these funct ions is less well understood. The present investigation utilized kaini c acid to bilaterally lesion specific areas of the rat hippocampus. Th ese animals were subsequently tested on a spatial orientation task usi ng a circular water maze, and on an associative/contextual task using passive avoidance conditioning. The results indicate that both the dor sal CA1 and the ventral CA3 subregions play important roles in learnin g. Specifically, CA1 lesions produced a deficit in the acquisition of the water maze task and a significant memory impairment on the passive avoidance task. CA3 lesions also caused learning deficits in the acqu isition of the water maze task, and produced even greater impairments in performance on the passive avoidance task. We conclude that CA1 and CA3 hippocampal subregions each play significant roles in the overall integration of information concerning spatial and associative learnin g.