Structural basis for the functional specialization of the pallidal complex of the cat brain

Experiments carried out on 30 cats using retrograde axonal transport of markers (horseradish peroxidase and luminophores) were used to study the organization of the afferent projection system of the pallidal complex (the globus pallidum, the entopeduncular nucleus, the ventral pallidum) formed by fibers from functionally different cortical and subcortical structures (the ventral tegmental area, the substantia nigra, the amygdaloid body). The distribution of afferent projection fibers in this complex of nuclei led to identification of the following zones: a "limbic" zone, corresponding to the ventral pallidum, and a "motor" zone, corresponding to the caudal part of the globus pallidum. On the one hand, the features of the afferent organization as demonstrated here can be regarded as a structural basis for the functional heterogeneity of the pallidal complex; on the other, significant regions within these structures (the rostral part of the globus pallidum and the entopeduncular nucleus) were found to receive projection fibers from functionally different structures, suggesting the existence of convergence and integration processes in these regions.