The skin is the body’s largest organ, making up roughly 16% of its total weight. It serves as a barrier between the inside and outside of the body and performs a variety of tasks, including feeling, which is mediated by a range of sensory organs. Touch is arguably the most ancient sense in terms of evolutionary order, and it plays a huge role in both physical and mental health even in the most advanced species. Particularly newborns suffer greatly when they are deprived of touch interactions with other humans, other than their mother. Their progress, both physical and psychological, is impeded. Their immune systems, heart rate, body temperature, brainwaves, and sleep patterns all alter during deprivation. In addition, touch is essential to sexual activity and, thus, reproduction. Numerous idioms and proverbs in the English language attest to its significance in human life.
The function of skin receptors in humans and animals has been extensively studied, and much is known about how the information they provide is processed by the central nervous system, however how exactly this information is converted into sensations is still unknown. Basic information is provided by cutaneous afferent nerve fibers for several functions that operate at different levels of the central nervous system.
Arousal is arguably the most ancient and phylogenetically primitive function. An organism should be alerted to potentially harmful effects and directed toward their source by a touch on its body surface. Thus, the brainstem reticular formation—a phylogenetically ancient structure—mediates the arousal response. Second, cutaneous afferents influence motor control at the spinal, brainstem, cerebellar, and cortical levels of the neuraxis. Patients with reduced finger sensibility serve as examples of this. They have sloppy fine motor skills and frequently drop or crush precious objects. These deficiencies most likely result from disrupted short-latency corrective responses in addition to a flawed central object representation. The characteristics of the items to be manipulated as well as the culmination of several manipulative acts are reflected in the cutaneous deformations stimulating the mechanoreceptors.
Therefore, tactile information may play a role in the discontinuation of motor acts or the start of new ones. These statements alone demonstrate how closely motor control and the third function—tactile object perception and recognition—are related. In actuality, perception itself may be seen as a complex evolutionary product that was first driven by improved movement control during phylogenetic evolution. Nevertheless, perception has now partially detached itself from this supporting role while preserving it.
REFERENCES
Windhorst, U. (1996). Tactile Senses. In: Greger, R., Windhorst, U. (eds) Comprehensive Human Physiology. Springer, Berlin, Heidelberg. https://doi.org/10.1007/978-3-642-60946-6_33