The Tail of the Striatum: From Anatomy to Connectivity and Function

Despite the striatum’s large extension along the rostro-caudal brain axis, current knowledge on the functions of the striatum rely mostly on its rostral sectors. Emerging evidence reveals a peculiar anatomo-functional organization of the tail of the striatum (TS). The TS, characterized by specific corticostriatal, thalamostriatal, and nigrostriatal converging projections, represents a key sensory-related striatal area. According to the spatial distribution of cell-type-specific neuronal populations and inputs connectivity, distinct TS domains can be distinguished across various mammalian species. Spiny projection neurons (SPNs) expressing dopamine D1 and D2 receptors (D1R and D2R) in the TS, show specific and unique spatio-molecular heterogeneity, and are highly reactive to dopamine-evoked stimuli. Understanding the anatomo-functional organization of the TS may lead to a more comprehensive view of striatal heterogeneity in physiology and pathology. The dorsal striatum, the largest subcortical structure of the basal ganglia, is critical in controlling motor, procedural, and reinforcement-based behaviors. Although in mammals the striatum extends widely along the rostro-caudal axis, current knowledge and derived theories about its anatomo-functional organization largely rely on results obtained from studies of its rostral sectors, leading to potentially oversimplified working models of the striatum as a whole. Recent findings indicate that the extreme caudal part of the striatum, also referred to as the tail of striatum (TS), represents an additional functional domain. Here, we provide an overview of past and recent studies revealing that the TS displays a heterogeneous cell-type-specific organization, and a unique input–output connectivity, which poises the TS as an integrator of sensory processing. The dorsal striatum, the largest subcortical structure of the basal ganglia, is critical in controlling motor, procedural, and reinforcement-based behaviors. Although in mammals the striatum extends widely along the rostro-caudal axis, current knowledge and derived theories about its anatomo-functional organization largely rely on results obtained from studies of its rostral sectors, leading to potentially oversimplified working models of the striatum as a whole. Recent findings indicate that the extreme caudal part of the striatum, also referred to as the tail of striatum (TS), represents an additional functional domain. Here, we provide an overview of past and recent studies revealing that the TS displays a heterogeneous cell-type-specific organization, and a unique input–output connectivity, which poises the TS as an integrator of sensory processing.