Tactile Innervation Densities Across the Whole Body

The study estimated that the skin across the whole body was innervated by approximately 230,000 tactile afferent fibers, with a plausible range of 200,000-270,000. 15% of these fibers innervated the palmar skin of both hands, and 19% innervated the region surrounding the face and lips. About 60% of all tactile fibers were slowly-adapting, while the rest were fast-adapting. Innervation density correlated well with psychophysical spatial acuity across different body regions and, on hairy skin, with hair follicle density. However, innervation density only weakly correlated with the size of the cortical somatotopic representation and could not fully account for the magnification of the hands and the face.