Participation of the hippocampal theta rhythm in memory formation for an eight-arm radial maze task in rats.

Participation of the hippocampal theta rhythm in memory formation was studied using an eight-arm radial maze task in rats. The numbers of reference memory and working memory errors were decreased gradually by daily training from session 10 and 6, respectively. On the other hand, the decrease in running time per choice was recognized from session 3. Theta power in the hippocampal CA1 area was gradually decreased from session 9, and there is a close relationship between the changes in theta power in the hippocampus and the number of reference memory errors. Based on those observations, it can be concluded that the hippocampal theta wave is intimately associated with the reference memory of the eight-arm radial maze in rats.