Topographic distribution of visual and somesthesic unitary responses in the Pul-LP complex of the cat.

An electrophysiological analysis of field potentials and unitary responses evoked by visual, acoustic and somesthesic stimuli in thalamic associative nuclei was performed in 'encéphale isolé' cats. Photic responses were particularly pronounced in the pulvinar nucleus (Pul) including its inferior division, while in lateralis posterior (LP) and, to a lesser extent, in the posterior nuclear group (PO) a prevalence of somesthesic responses was found. Only a few units were influenced by the acoustic (clicks) stimulation. Unitary convergence and interaction was a characteristic common to all divisions of Pul-LP complex. Areas of different functional significance can therefore be traced into the associative thalamic posterior nuclei, according to their modal sensitivity. The topographic functional organization is in partial agreement with the distribution of afferent connections shown by previous anatomical studies.