HIGHLY RESTRICTED ORIGIN OF PREFRONTAL CORTICAL INPUTS TO STRIOSOMES IN THE MACAQUE MONKEY

The prefrontal cortex is made up of neocortical areas thought to media te aspects of the temporal and spatial organization of behavior. One o f the prime output targets of the prefrontal cortex is the striatum, w hich is thought to operate in series with the prefrontal cortex in som e neural computations. We have analyzed this prefrontostriatal project ion in cynomolgus monkeys by combining anterograde neuronal tract trac ing methods with neurochemical markers for the striosome and matrix co mpartments of the striatum. Our results single out two parts of the fr ontal cortex as projecting densely to the striosome compartment of the striatum: the posterior orbitofrontal/ anterior insular cortex and th e mediofrontal prelimbic/anterior cingulate cortex. These areas jointl y innervated striosomes in the anterior and ventromedial striatum, mai nly in the caudate nucleus. Striosomes in the dorsolateral striatum we re never labeled. Thus, the anatomical subsystem defined by striosome affiliation includes three cortical and striatal regions that, in huma ns, have been implicated in obsessive-compulsive disorder. Nearly all of the remaining parts of the prefrontal cortex studied projected pref erentially to the matrix compartment. Most of these prefrontal inputs were also patchy, and many of the patches (matrisomes) were selectivel y paired with nearby striosomes. The highly fractionated organization of prefrontal inputs to striosomes and matrisomes could form a templat e for computational networks in the striatum that redistribute prefron tal corticostriatal inputs to serve in context-dependent behavioral pl anning.