The cholinergic system in the basal forebrain of the Atlantic white-sided dolphin (Lagenorhynchus acutus)

The basal forebrain (BFB) cholinergic neurotransmitter system is important in a number of brain functions including attention, memory, and the sleep-wake cycle. The size of this region has been linked to the increase in encephalization of the brain in a number of species. Cetaceans, particularly those belonging to the family Delphinidae, have a relatively large brain compared to its body size and it is expected that the cholinergic BFB in the dolphin would be a prominent feature. However, this has not yet been explored in detail. This study examines and maps the neuroanatomy and cholinergic chemoarchitecture of the BFB in the Atlantic white-sided dolphin (Lagenorhynchus acutus). As in some other mammals, the BFB in this species is a prominent structure along the medioventral surface of the brain. The parcellation and distribution of cholinergic neural elements of the dolphin BFB was comparable to that observed in other mammals in that it has a medial septal nucleus, a nucleus of the vertical limb of the diagonal band of Broca, a nucleus of the horizontal limb of the diagonal band of Broca, and a nucleus basalis of Meynert. The observed BFB cholinergic system of this dolphin is consistent with evolutionarily conserved and important functions for survival.