Vestibular, auditory, and somatic input to the posterior thalamus of the cat

Abstract

The responses of 157 neural units in the magnocellular (mc) and parvocellular (pc) components of the medial geniculate nucleus (MG) and other nuclei of the posterior (PO) thalamic group were recorded and analyzed. Units were tested for a response to electrical stimulation of the vestibular nerve, natural auditory and electrical cochlear nerve stimulation, and natural stimulation of joint, muscle, and cutaneous receptors of the limbs, trunk, and neck (somatic stimulation). Only 45% of the units responded to these stimuli. Twenty-four percent of the responsive units were multimodal, responding to more than one stimulus. All multimodal units were activated by auditory stimuli. More units responding to vestibular stimulation were found in mcMG than in pcMG or other components of the PO group. Potentials evoked by vestibular nerve stimulation were recorded in all 3 regions with latencies of 5--25 msec. No evidence was found for a thalamic relay from vestibular nerve to cortex in the area investigated, since the recorded latency for activity from vestibular nerve stimulation was longer than the latency of responses recorded in the cortex. This region of the thalamus appears to be important for reception of auditory information and integration with vestibular and somatic modalities.

The thalamocortical vestibular system in animals and humans

“…In the squirrel monkey, Akbarian et al (1992) proposed the MGmc to be the "caudal and inferior continuation of the "proprioceptive shell" of the ventroposterior thalamic complex", the VPP merging ventrally with the MGmc. Blum et al (1979a) demonstrated a larger proportion of vestibular-responsive neurons in the MGmc than in the parvocellular part of the MGN and than in other PO regions. Older observations also revealed that lesions of the MGmc and PO suppressed vestibular-evoked responses in the cerebral cortex (Potegal et al, 1971;Spiegel et al, 1965).…”

“…The medial geniculate nucleus (MGN) contains neurons activated by electrical stimulation of the vestibular nerve (Blum et al, 1979a(Blum et al, , 1979bMatsuo et al, 1999;Roucoux-Hanus and BoisacqSchepens, 1977), as confirmed by anatomical studies showing vestibular projections to the MGN in the cat (Kotchabhakdi et al, 1980;Mergner et al, 1981) and in the rat (Nagata, 1986). The MGN receives projections mainly originating from the DVN (Kotchabhakdi et al, 1980;Matsuo et al, 1995;Mergner et al, 1981;Nagata, 1986), the SVN (Shiroyama et al, 1999) and the MVN (Kotchabhakdi et al, 1980;Mergner et al, 1981).…”

“…The MGN receives projections mainly originating from the DVN (Kotchabhakdi et al, 1980;Matsuo et al, 1995;Mergner et al, 1981;Nagata, 1986), the SVN (Shiroyama et al, 1999) and the MVN (Kotchabhakdi et al, 1980;Mergner et al, 1981). In particular, the magnocellular division of the MGN, or MGmc (medial geniculate nucleus, pars magnocellularis), corresponding to the medial portion of the MGN and identified by its cellular morphology (Calford, 1983;Morest, 1964), has been involved in auditory, vestibular and somatosensory integration (Blum et al, 1979a). In the cat, the MGmc, together with other regions of the posterior group of the thalamus (PO), receives vestibular projections (Kotchabhakdi et al, 1980).…”

“…Older observations also revealed that lesions of the MGmc and PO suppressed vestibular-evoked responses in the cerebral cortex (Potegal et al, 1971;Spiegel et al, 1965). In addition to auditory afferents from the inferior colliculi and vestibular afferents from the vestibular nuclei, the MGmc receives afferents from the superior colliculi and the spinal cord, thus integrating multiple sensory signals (Blum et al, 1979a). The MGmc sends projections to the primary auditory cortex and to different sensory "association" areas surrounding the primary auditory cortex ("diffuse insular-temporal" cortical projections according to Jones, 1985;p.…”

Cross-Sensory Modulation of Primary Sensory Cortex Is Developmentally Regulated by Early Sensory Experience

“…What is the best explanation for such facilitation in an early response period dominated primarily by thalamocortical inputs? There is ample evidence that subcortical auditory structures such as the dorsal cochlear nucleus (DCN) (Zhou and Shore, 2004;Haenggeli et al, 2005;Shore, 2005;Shore et al, 2008), the inferior colliculus (IC) (Jain and Shore, 2006;Zhou and Shore, 2006), and the medial division of the thalamic medial geniculate nucleus (mMGN) (Poggio and Mountcastle, 1960;Blum et al, 1979;Nicolelis et al, 1991) all receive significant somatosensory inputs and show multisensory responses. Thus, these structures, in turn, may influence subcortical somatosensory structures such as the trigeminal nucleus (TN) and the thalamic ventral posterior medial nucleus (VPM).…”