Basal ganglia and cerebellar inputs to 'AIP'.

The anterior intraparietal area (AIP) is a subregion of area 7b in posterior parietal cortex. AIP neurons respond to the sight of objects, as well as to the act of grasping them. We used retrograde transneuronal transport of rabies virus to examine subcortical inputs to AIP in the monkey. Virus transport labeled substantial numbers of neurons in the substantia nigra pars reticulata (SNpr), as well as in the dentate nucleus of the cerebellum. The hotspots of labeled neurons in SNpr and in dentate after AIP injections were separate from those created by virus injections into several other parietal or frontal regions. These observations provide the first evidence that a major output nucleus of the basal ganglia, the SNpr, projects to a region of posterior parietal cortex. In addition, our findings provide further support for the concept that posterior parietal cortex is a target of cerebellar output.