ABSTRACT
The fundamental design of the sensory system is described with various receptor organs for touch, vision, and hearing, for example, that signal to the central nervous system by the firing of impulses or messages that in the manner of a code transmit to the brain the place and intensity of the stimulus. The transmission is never direct but by synaptic relays (cp. Fig. E2–1) which act to modify the message so that in fact the central nervous system is given a very distorted “coded image” of the peripheral stimulus. It can be thought that these transmission lines are concerned in the conversion of the original stimulus into neuronal events which can be handled and interpreted in the cerebral cortex. Each sense has the primary receiving area laid out as a map in the cortex in the appropriate Brodmann areas. For example, cutaneous sense is laid out with the surface of the body arranged as a strip map from toes to tongue along Brodmann areas 3, 1, 2 (Figs. E1–1, 4).
