[Projections of the parietal cortex on the vestibular complex in Macaca]

Connections of parietal cortex (especially posterior part of area 7) with subcortical structures related with vestibular function were examined in four monkeys (Macaca Fascicularis), by means of anterograde labeling with HRP and tritated amino-acids tracers. Posterior parietal cortex was found to have direct efferent projections onto vestibular nuclei complex and prepositus hypoglossi nucleus. These efferences were distributed bilaterally with an ipsilateral preponderance. The labeled terminals were organized in precise patterns in vestibular nuclei in such a way that two groups of cortical efferences could be distinguished: the first one terminates on vestibular nuclei related with the cervico-spinal motor system and the second one terminates on both prepositus hypoglossi nucleus and vestibular nuclei involved in vestibulo-ocular functions. These latter efferent projections of parietal cortex onto vestibular nuclei complex could account for the role played by the posterior part of area 7 in the modulation of the vestibulo-ocular reflex.