Tactile functions of mechanoreceptive afferents innervating the hand.

Four types of mechanoreceptive afferents innervate the glabrous skin of the hand. Evidence from more than three decades of combined psychophysical and neurophysiological research supports the idea that each afferent type serves a distinctly different sensory function and that these functions explain most of tactual perceptual function. The available evidence supports the following hypotheses: (1) The slowly adapting type 1 system provides the information on which form and texture perception are based. (2) The cutaneous rapidly adapting system provides information about minute skin motion and, thereby, plays a critical role in grip control. (3) The Pacinian system is responsible for the detection and perception of distant events by vibrations transmitted through objects, probes, and tools held in the hand. (4) The slowly adapting type 2 system provides information for the perception of hand conformation and for the perception of forces acting on the hand. The authors review the evidence on which these hypotheses are based. They also review the role of proprioceptive afferents in the perception of hand conformation because they appear to play a significant role along with cutaneous afferents.