Acetylcholinesterase staining in human auditory and language cortices: Regional variation of structural features

Cholinergic innovation of the cerebral neocortex arises from the basal forebrain and projects to all cortical regions. Acetylcholinesterase (AChE), the enzyme responsible for deactivating acetylcholine, is found within both cholinergic axons arising from the basal forebrain and a subgroup of pyramidal cells in layers III and V of the cerebral cortex. This pattern of staining varies with cortical location and may contrib-ute uniquely to cortical microcircuhry within functionally distinct regions. To explore this issue further, we examined the pattern of AChE staining within auditory, auditory association, and putative language regions of whole, postmortem human brains. The density and distribution of acetylcholine-containing axons and pyramidal cells vary systematically as a function of auditory process-ing level. Within primary auditory regions AChE-containing axons are dense and pyramidal cells are largely absent Adjacent cortical regions show a decrease in the density of AChE-containing axons an