Thalamocortical connectivity for multisensory and motor integration in the macaque monkey

Céline Cappe, University of Fribourg, Switzerland and University of Toulouse, France

Abstract
Although mutisensory integration has been shown to take place essentially in the cerebral cortex and the superior colliculus, the thalamus may play a role as well. To address this question, seven neuroanatomical tracers were injected in one monkey in the auditory cortex (rostral (RP) and caudal (CP) parabelt areas), the posterior parietal cortex (areas MIP and PEC), the prefrontal cortex (area 46) and the premotor cortex (PMd-c and PMv-c) to assess their thalamocortical connectivity.
Thalamocortical projections, distinct from specific unimodal sensory ones, were observed from motor thalamic nuclei, such as the ventroanterior nucleus (VA) and the medial part of the ventrolateral nucleus (VLM) to CP and RP. These territories of projections in VA and VLM were adjacent or partly overlapping clusters of thalamocortical cells projecting to PMd-c, MIP and PEC (only in VLM). The anterior pulvinar nucleus projects to MIP, the lateral pulvinar nucleus projects to MIP and PEC and the medial pulvinar nucleus projects strongly to CP and RP and weakly to MIP.
These data suggest the presence of thalamic territories integrating different sensory modalities with motor attributes. Furthermore, considering the corticothalamic projections, the thalamus may also represent a pathway of communication between cortical areas of different modalities.

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