[Characteristics of the cortical input of the hippocampus. Functional differences in the lateral and medial entorhinal cortex].

Extracellular investigation in unanaesthetized rabbits revealed low reactivity of the lateral entorhinal cortex neurones (lEC, field 28b) to visual and auditory stimuli. Only 25% of cells responded to them by diffuse long-latency reactions, while in medial EC (mEC, field 28a) 70% of neurones responded to these stimuli with short-latency patterned reactions. The neurones of lEC were selectively responsive to different somatosensory stimuli. Among reactions short-latency on-effects were observed. In some cells application of these stimuli switched on rhythmic bursts of spikes (frequency about 3-4 Hz) or regular activity of pacemaker type. The lEC neurones responded by short-latency driving to electrical stimulation of prefrontal cortex, while mEC neurones were responsive to stimulation of posterior non-primary neocortical areas. The data are discussed in the light of recent morphological findings on cortico-cortical connections of EC.