ENHANCED HIPPOCAMPAL THETA EEG DURING WHOLE-BODY ROTATIONS IN AWAKE RESTRAINED RATS

Hippocampal slow wave activity in the theta band was studied in awake restrained rats as they were rotated in the horizontal plane both in l ight and in darkness. Monopolar recordings were made with an insulated silver wire (200 mu m diameter) implanted in the dentate gyrus with r eference to the occipital bone. Fast Fourier transforms were made of d ata recorded when the rat was either rotated passively or remained imm obile. The power in the 6-9 Hz frequency band ('type I' theta) was sig nificantly increased during rotations. The same results were obtained in experiments performed in the light or in complete darkness. These r esults provide evidence for a role of inertial (possibly, vestibular) information in hippocampal spatial representations.