Hippocampal cytochrome oxidase activity of rats in easy and difficult visual discrimination learning

The present study investigated the functional involvement of the rat hippocampal formation in easy and difficult visual discrimination learning by measuring regional brain cytochrome oxidase (C.O.) activity, an index of neuronal metabolic activity. The results showed that learning was related to C.O. activity in the CA field and the dentate gyrus of the hippocampal formation of rats in the difficult discrimination, whereas learning was related to C.O. activity only in the dentate gyrus of rats in the easy discrimination. The results suggest that difficult visual discrimination learning required greater involvement of the hippocampal formation than easy visual discrimination learning.