[Activity of neurons of the anterior thalamic nuclei after elimination of afferent pathways from the hippocampus and limbic cortex].

Neuronal activity of anterior thalamic nuclei AV and AD was analyzed in chronic rabbits after lesion of the fornix-fimbria or its combination with transection of the septum and capsula interna fibers at the rostral prethalamic level. The results were compared with previous data obtained in intact animals and after MTT lesion. Decrease of reactivity to sensory stimuli, "de-specialisation" of reactions (dominance of diffuse tonic effects and disappearance of patterned and phasic reactions) was observed in AV. The degree of the observed changes correlated with the volume of the lesioned limbic afferent pathways. Contrary to that, slight increase of reactivity to sensory stimuli was invariably present in AD. All characteristics of responses were preserved by the AD neurones after any type of limbic deafferentation. Only dynamic changes of reactions (gradual build-up and habituation) were absent in both nuclei after massive limbic deafferentations. The data support a previous conclusion that while AV is indeed an important integral link of the limbic circuit, AD should be regarded as relatively independent structure, introducing sensory information into limbic system and subjected to its secondary modulating influence.