Role of septal and entorhinal inputs in the generation of hippocampal electrical activity in the cat sleep-wake cycle

Abstract

The effects of septal lesion and entorhinal cortex section on hippocampal electrical activity during the cat sleep-wake cycle were investigated in chronic experiments. The medial portion of the septum only was found to participate in generation of this activity. Complete suppression of hippocampal theta rhythm during active wakefulness and paradoxical sleep were the main effects of septal lesion. In slow-wave sleep, the effects of septal lesion manifested in a slight attenuation of the intensity of the dominant frequency (of 1 Hz). Widespread septal lesion does not add to the changes occurring when the medial portion of the septum is so isolated. Section of the entorhinal cortex produces a sharp increase in hippocampal theta rhythm during waking and paradoxical sleep. Clearcut attenuation of delta and subdelta rhythm intensities were observed in slowwave sleep. It is postulated that under normal conditions hippocampal entorhinal input exerts a modulating effect on the genesis of hippocampal theta rhythm.