Cholinergic Systems in the Brain and Spinal Cord: Anatomic Organization and Overview of Functions

Abstract

A cartoon in a recent issue of the Los Angeles Times newspaper bore the interesting caption “How the brain works.” A cut-away depiction of a human head was shown, and, inside it, a workman was busily plugging and unplugging various wires and cords. What the cartoonist was suggesting, we believe, is that when we understand how the brain is wired, we will have taken a necessary step in understanding how it works, and this viewpoint, in our opinion, has considerable merit. Regardless of the particular communication system under consideration, information transmission always occurs within a physical framework consisting essentially of a sender, a communication channel, and a receiver (Shannon, 1948). In the nervous system the sender may be a neuron, the communication channel a synaptic cleft or other conduit of information (e.g., circulatory system) between two or more cells, and the receiver a particular target structure such as another neuron or a gland or muscle cell. The data neuroanatomy provides is relevant to understanding the matrix within which information transmission in the nervous system occurs, and, if neurons containing particular transmitters are demonstrated, neuroanatomy can indicate what chemical messengers are used to transmit information at certain loci.