Tactile Innervation Densities Across the Whole Body

The study estimated that the skin of young adults is innervated by approximately 230,000 tactile afferent fibers, with a plausible range of 200,000–270,000, and noted a 5–8% decrease per decade due to aging. It found that 15% of these fibers innervate the palmar skin of the hands and 19% the region around the face and lips. The distribution of slowly and fast-adapting fibers varied by skin region. Innervation density correlated with psychophysical spatial acuity and, on hairy skin, with hair follicle density. However, it only weakly correlated with the size of the cortical somatotopic representation, not fully explaining the magnification of the hands and face.