Vestibular, somatosensory, and auditory input to the thalamus of the cat

Responses were recorded and analyzed for 334 single units in the ventral, posterior, and intralaminar groups of thalamic nuclei of the cat. Units were tested for a response after (i) electrical stimulation of the vestibular nerve: (ii) electrical stimulation of the four paw pads and natural stimulation of joint, muscle, and cutaneous receptors of the limbs, trunk, and head (somatic stimulation); and (iii) electrical stimulation of the cochlear nerve and sound (auditory stimuli). Forty-one percent of the units responded to these stimuli. Vestibular stimulation activated 16% of the responsive units. These units were found primarily in the posterior nucleus and the border region between it and the ventral posterolateral nucleus. Seventy-three percent of vestibular-activated units also responded to at least one other modality of sensory stimuli. No evidence was found for a thalamic region where the majority of units responded at short latency to vestibular nerve stimulation. Ninety percent of the responsive units were activated by somatic stimuli. These units could be divided into two groups. One group was composed of units that were activated exclusively by somatic stimuli and had a small contralateral receptive field. These units were found primarily in the ventral posterolateral nucleus. The other group had a bilateral receptive field or was activated by more than one modality of sensory stimuli. These units were found primarily in the posterior nucleus and the border area of the ventral posterolateral nucleus. Units that responded to auditory stimulation (10% of responsive units) were found in the posterior nucleus and the medial geniculate nucleus.