The crossed cortico-caudate projection in the rhesus monkey.

In the normal young adult rhesus monkey, reduced silver staining of degenerating axons revealed that the lateral prefrontal cortex projects to the caudate nucleus of the contralateral hemisphere. This crossed prefronto-caudate projection provides a means whereby the prefrontal cortex can affect the neuronal activity of the extrapyramidal motor systems in both hemispheres. These findings also support the concept that apparent neuronal plasticity in this primate telencephalic system is a result of expanded projections of axons that normally issue a minor projection to the contralateral caudate nucleus.