Cell type-specific variation of somatotopic precision across corticostriatal projections

Abstract The striatum shows general topographic organization and regional differences in behavioral functions. How corticostriatal topography differs across cortical areas and cell types to support these distinct functions is unclear. This study contrasted corticostriatal projections from two layer 5 cell types, intratelencephalic (IT-type) and pyramidal tract (PT-type) neurons, using viral vectors expressing fluorescent reporters in Cre-driver mice. Long-range corticostriatal projections from sensory and motor cortex are somatotopic, with a decreasing somatotopic specificity as injections move from sensory to motor and frontal areas. Somatotopic organization differs between IT-type and PT-type neurons, including injections in the same site, with IT-type neurons having higher somatotopic stereotypy than PT-type neurons. Furthermore, IT-type projections from interconnected cortical areas have stronger correlations in corticostriatal targeting than PT-type projections do. Thus, as predicted by a long-standing basal ganglia model, corticostriatal projections of interconnected cortical areas form parallel circuits in basal ganglia-thalamus-cortex loops.