Touch

Touch is the sense by which the body perceives mechanical contact, texture, and pressure through skin and related tissues. It provides information about object properties, location, and contact dynamics and supports motor control, perception, learning, and social interaction.

Physiology: The skin contains mechanoreceptors that transduce mechanical stimuli into neural signals. Meissner corpuscles (rapidly adapting, FA I) detect light touch and low-frequency vibration; Merkel cells (slowly adapting, SA I) respond to sustained pressure and fine details; Pacinian corpuscles (FA II) sense high-frequency vibration; Ruffini endings (SA II) respond to skin stretch. Temperature is detected by thermoreceptors, while nociceptors signal potential damage. Afferent fibers convey information to the spinal cord and brain, with touch primarily carried by the dorsal column–medial lemniscus pathway, processed in the primary somatosensory cortex, and integrated with other senses in multisensory areas.

Modalities: Touch covers pressure, texture, roughness, vibration, spatial contours, and proprioceptive feedback from muscles and joints. The brain constructs percepts of shape and texture (stereognosis) and estimates contact location and force. Tactile acuity varies across skin regions and with attention.

Social and developmental aspects: Affective or social touch engages C-tactile afferents and is linked to mood and bonding. In early development, touch supports growth, attachment, and sensorimotor learning; in adults, it modulates stress and social communication.

Applications: In technology, haptic feedback aims to reproduce tactile sensations in devices such as smartphones, prosthetics, and virtual reality interfaces, enabling more interactive and intuitive interfaces.