The neostriatal mosaic: striatal patch-matrix organization is related to cortical lamination

The basal ganglia, of which the striatum is the major component, process inputs from virtually all cerebral cortical areas to affect motor, emotional, and cognitive behaviors. Insights into how these seemingly disparate functions may be integrated have emerged from studies that have demonstrated that the mammalian striatum is composed of two compartments arranged as a mosaic, the patches and the matrix, which differ in their neurochemical and neuroanatomical properties. In this study, projections from prefrontal, cingulate, and motor cortical areas to the striatal compartments were examined with the Phaseolus vulgaris-leucoagglutinin (PHA-L) anterograde axonal tracer in rats. Each cortical area projects to both the patches and the matrix of the striatum; however, deep layer V and layer VI corticostriatal neurons project principally to the patches, whereas superficial layer V and layer III and II corticostriatal neurons project principally to the matrix. The relative contribution of patch and matrix corticostriatal projections varies among the cortical areas examined such that allocortical areas provide a greater number of inputs to the patches than to the matrix, whereas the reverse obtains for neocortical areas. These results demonstrate that the compartmental organization of corticostriatal inputs is related to their laminar origin and secondarily to the cytoarchitectonic area of origin.