Alterations of Na, K, Ca, and Mg concentration in the rat hippocampus were investigated with atomic-absorption method, in the process of learning and memory, following destruction of the medial septum and entorhinal cortex. These data were compared to those of the heavy metals, obtained in similar conditions. It was found that in learning and memory processes, after ablation of the main inputs of the hippocampus, sodium and potassium concentration remains relatively unaltered, while Mg and Ca undergo significant changes. In our opinion this fact is due to both increased compensatory synthesis processes induced by ablation of the main inputs of the hippocampus, and to participation of these elements in synthesis of specific proteins in a course of learning and memory and formation and retention of an engram. Increased concentration of zinc and copper certifies for important part of these metals during the above processes.