ABSTRACT
This chapter shows that basalo-cortical projection neurons are comprised by cholinergic and other non-cholinergic neurons, particularly GABAergic neurons, and that these neurons are collectively but differentially influenced by multiple afferents from the brainstem. The cholinergic neurons of the basal forebrain are distributed in a continuum extending from the septum, diagonal band of Broca, magnocellular preoptic nucleus, and substantia innominata into the globus pallidus. The basal cell complex lies within the ascending, as well as descending, fibers of the medial forebrain bundle. Accordingly, the large cholinergic and GABAergic neurons with long dendrites sit in a position to receive inputs from the passing fibers originating in the brainstem. GABAergic neurons also comprise a portion of the nucleus basalis and project in parallel with and in equal proportion to the cholinergic cells to widespread areas of the neocortex.
