Frequency-specific relation between hippocampal theta rhythm, behavior, and amobarbital action.

The frequency of the hippocampal theta rhythm in freely moving rats varies predictably in relation to behavior in a simple learning situation. The theta rhythm may be driven by electrical stimulation of the medial septal area at frequencies within the theta range. The threshold for septal driving is lowest at that frequency which the rat displays in response to frustrative nonreward; the driving threshold is selectively raised at this frequency by sodium amobarbital. It is suggested that the behavioral effects of amobarbital are due to a disruption of the theta frequency normally displayed in response to nonreward.