Neurochemically specified subsystems in the basal ganglia.

The fibre pathways associated with the basal ganglia include through-conduction lines and side-loops associated with the striatum, pallidum and substantia nigra. Each of these regions is now known to contain subdivisions differing from one another in the neurotransmitter-related compounds they contain. This paper includes an outline of these new findings and a commentary on some of their functional implications.