[Characteristics of the neuronal activity of structures of the hippocampal formation (subiculum)].

Spontaneous and evoked neuronal activity of subiculum was investigated in chronic unanaesthetized rabbits. Rhythmic components of two different types were observed in the spontaneous activity of 58% of units: 4.5-6.0 cps bursts (13%) and 2.0-3.8 cps (45%). Besides their basic frequency, these types of rhythmic activity were differentiated by several additional criteria. 63% of the cells responded to applied sensory stimuli, among which auditory stimuli were the most effective. Multimodal units were slightly more numerous (59%) than unimodal ones. In 50% of the recorded units responses were of tonic type, in 31%--of phasic type, and in 19%--specific on-off responses were observed. In majority of units with repeated stimulations relatively rapid process of habituation developed after a short incremental phase. Interruption of septal afferents resulted in disappearence of 4.5-6.0 cps (theta) bursts, in reduction in the number of tonic responses and in absence of habituation. Similarity of neuronal characteristics in the field CA1 and subiculum is discussed.