Spatial memory and c-fos expression in supramammillary nucleus, anterior cingulated gyrus and entorhinal cortex

To investigate brain substrates of spatial memory, the cellular expression of c-Fos protein in mts was studied after training the animals to perform a spatial reference memory task and a working reference memory task in a Mor ris water maze. The number of c-Fos positive neuronal nuclei was quantified in several brain regions: entorhinal cortex, anterior cingulate gyrus, and supramammillary nucleus. The results showed that spatial training in refer ence and working memory tasks increased the number of entorhinal cortex act ivated neurons (c-Fos positive neurons). No clear association was found bet ween c-Sos activation in the anterior cingulate gyrus and either spatial re ference or working memory tasks. The number of c-Fos immunoreactive neurona l nuclei in the supramammillary neurons was greater in thr spatial working memory groups than in the spatial reference memory groups suggesting that n eurons of the supramammillary nucleus plays an important role in spatial pr ocessing.