It is believed that the hippocampus and the neocortex are involved in several aspects of learning and memory. However, the relationship of the activities between the hippocampus and the neocortex are not well investigated. In the present study, we recorded the response to a sound stimuli in the auditory cortex of the anesthetized guinea pig by voltage sensitive optical recording. And we examined the effect of the hippocampal stimulation on the auditory cortex response by changing the stimulation current intensity. The results showed that the weak stimulation inhibits the auditory responses but the strong stimulation facilitates the responses. It means that the hippocampal activity can produce excitatory or inhibitory potentials, suggesting that it is an important neuronal basis of the memory consolidation process.
