[Background activity of neurons of the cortical portions of the limbic system of the rabbit brain].

Background activity recorded extracellularly in cortical limbic areas of unanesthetised rabbits was analyzed by means of a computer. Special attention was payed to the rhythmic components of the activity in theta- and delta-range. Only small proportion of units (5-12%) in various structures, except lateral entorhinal cortex possessed rhythmic modulation in theta-range. Delta-modulation was observed in all investigated areas, but had various characteristics. It was very prominent both in subiculum (45% of units) and in entorhinal cortex (22%). While in subiculum (as in other areas) it consisted of high-frequency short bursts with long interburst intervals, the opposite was typical of entorhinal cortex. Arousing stimuli increased frequency and regularity of theta-bursts and desynchronized delta-activity in majority of structures; in entorhinal cortex they increased intraburst frequency of discharges without influencing frequency or regularity of the bursts.