Connections from the neocortex to the vestibular brain stem nuclei in the common marmoset

MONOSYNAPTIC projections from the cerebral cortex to the vestibular nuclei were studied in the common marmoset monkey (Callithrix jacchus) by injecting fluorescent dextranes into the brain stem vestibular nuclei. The injection sites were determined by single unit vestibular responses identified later histologically. During the recordings sinewave rotation in pitch, roll or yaw or steady tilt was applied. The most notable loci of labelling were found inside the primary sensory cortex, the cortex deep down along the posterior lateral sulcus, the premotor region and the anterior cingulate cortex. From studies in other primates these cortical areas are known to process vestibular information. Their connections with the vestibular nuclei may serve as an internal feedback modulating the vestibular brain stem activity.