This chapter describes how the barrel cortex processes sensory information from a systems viewpoint. Several questions are addressed, such as how information is coded, what processing a cortical column performs and how active touch might work. While considerable progress has been made in recent years in tackling these questions, it is not yet possible to answer them fully. Here we approach sensory processing from the viewpoint that it is possible to shed light on several classic questions in the general field of sensory physiology by studying the barrel system.

One of the classic questions in sensory physiology concerns how information is coded and whether information travels in specialized channels that form labeled lines of information. The issue is particularly pertinent in the barrel system where the very purpose of the anatomical pattern of the whiskers and barrels seems to indicate an affirmative answer. However, while labeled-line processing is a good first-order approximation for the barrel system (Section 5.1), many studies in recent years show how barrel cortex integrates information from different whiskers. The tension between these two ideas has driven many studies in this field and they are treated from two complementary but inverse viewpoints in Section 5.2, which deals with cortical domains driven by single whiskers, and Section 5.3, which deals with receptive fields.

Section 5.4 on dynamic sensory processing looks at the question of how active touch can be understood and the degree to which studies on passive touch (treated in earlier sections of the chapter) can inform this understanding.