[Compartmentalized organization of human corpus striatum]

The compartmentalization of the human striatum was first established thanks to the pioneer work of Graybiel and Ragsdale in 1978. These authors described in the human striatum, as well as in the cats and primates, zones poorly stained for the enzyme acetylcholinesterase, which they termed striosomes, that lie in more intensely stained matrix. The striosome/matrix subdivision of the striatum is supported by the distribution of a wide variety of transmitter-related substances and by the organization of striatal afferent and efferent connections.

The results of many studies performed in different species in the last twenty years have indicated that the chemical heterogeneity of striatum is more complex than the simple subdivision into striosomes and matrix compartments. Thus, a further subdivisions of the dual striosome/matrix system has been proposed on the basis of the results of a huge amount of works combining tract tracing methods with histochemical techniques. The matrix has been demonstrated to be heterogeneous by containing numerous functional modules that were termed matrisomes. Furthermore, the most recent study of the distribution of a wide variety of neurochemical markers in the striosomal compartment of the human striatum, has revealed that the striosomes are themselves heterogeneous, being composed of a central core and a peripheral region.

Since it is now twenty years from the first description of the striosome/matrix organization of the striatum, in this review we intend to summarize the major finding regarding the compartmental organization of this subcortical structure that have been obtained during this period of time.