Coding in the whisker sensory system

Our goal here is to characterize a chain of events that occurs when a rat acts upon signals received through the whiskers. We begin by describing the essential organization of the sensory pathway originating in the whiskers. Thereafter, our emphasis is on those aspects of neuronal activity that have been linked to observable behavior. Thus, we will give little space to neuronal response properties, such as the sensitivity to the orientation of deflections (Simons, 1978), that have not been shown to be behaviorally salient for the animal. We will outline the most effective ways of quantifying the rat’s sensory capacities. Then we address three questions: (i) What are the behavioral capacities that have, so far, been found to be supported by the whiskers? (ii) How does whisker motion specify the external stimulus? and (iii) What neuronal codes are present in sensory cortex?.