Projections of the temporo-parietal cortex on vestibular complex in the macaque monkey (Macaca fascicularis)

Connections of the posterior parietal cortex (area 7) with the vestibular complex have been studied in 4 macaque monkeys by anterograde axonal transport methods. WGA-HRP and tritiated amino-acids have been injected in the posterior part of area 7 including the caudal end of the superior bank of superior temporal sulcus and the lateral sulcus. Labeled terminals were observed in the vestibular nuclei complex and distributed bilaterally with a greater ipsilateral contribution. Two main groups of area 7 efferences were found to project to vestibular complex: a) A first group terminates on vestibular nuclei (the inferior vestibular nucleus and the caudal part of the medial nucleus) mainly connected with cerebello-spinal system. b) A second group terminates on vestibular nuclei (the medial and the superior vestibular nuclei and the y group) mainly involved in vestibulo-ocular mechanisms. The prepositus hypoglossi nucleus has also been found to receive area 7 projections. It is concluded that the possible control played by area 7 on the vestibulo-ocular reflex might be exerted through these direct cortico-vestibular projections.