The large segment of the attempts to gain an appreciation for the functional organization of the somatosensory cortex is based on the study of responses expressed as electrical activity, and engendered under specific, operationally defined stimulus conditions. The expectation that motivates these efforts is that it will be possible to analyze the pattern of flow and distribution of activity elicited by stimuli of known properties; to characterize the qualitative and quantitative relations between the stimuli used and the electrical responses obtained; and to fractionate the complex neural system into functionally and operationally distinct, though interacting, subunits. This latter objective is closely allied with the neuroanatomist’s goal to describe and identify different morphological constituents and their geometric and possible synaptic relations to one another. Accordingly, the point of view that underlies the study of functional organization of neural systems is correlative in the sense of seeking to identify the role played by different structural components in the generation of the dynamic performance (i. e.: information flow) under controlled or natural perturbation by stimulus input.