How are the basal ganglia organized?
There are three levels of organization within the basal ganglia.
The first level consists of the two major striatal outputs:
(1) the indirect pathway to the external segment of the GP (GPe) and
(2) the direct pathway to the SNr and internal segment of the GP (GPi).
The second level of organization consists of pathways from the cerebral cortex (sublaminae of layer V) to the patch (striosome) and matrix compartments of the striatum (which are organized in a mosaic pattern).
The third level of organization is related to the topography of cortical projections to other regions of the striatum.
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Báez-Mendoza R, Schultz W: The role of the striatum in social behavior. Front Neurosci 7:233, 2013.