How do fibers from the caudate nucleus and putamen reach the globus pallidus?

Fibers from the caudate nucleus and putamen—which together form the neostriatum—reach the globus pallidus via striatopallidal fibers. These fibers converge on the globus pallidus in a manner described as being like the spokes of a wheel.1

These projections originate from spiny striatal neurons that primarily utilize the neurotransmitter gamma-aminobutyric acid (GABA). The distribution of these fibers is specific: while both segments of the globus pallidus receive GABAergic terminals, the lateral segment specifically receives enkephalinergic projections, whereas the medial segment receives fibers containing substance P.1