[Neuronal activity of the "isolated hippocampus"].

Spontaneous and evoked activity of the field CA1 neurones were investigated in long-lasting experiments on unanesthetized rabbits with "isolated hippocampus" (destruction of both septal and perforant path's afferents). Testing by various sensory stimuli as well as by electrical stimulation of Schaffer's collateral's, subiculum, posterior cingulate cortex, neocortex and midbrain reticular formation was used. The sensory reactions were virtually absent during first 1--2 weeks after the operation, but by the 4--6th week the level of reactivity became normal (65--70%). The first sensory reactions encountered were of diffuse tonic type; later on complex patterned on-responses appeared. The sources of hippocampal reactions, the possibility of plastic rearrangement of synapses and the absence of intrinsinc ability for generation of the theta-activity are discussed.