Mechanisms of tactile sensory deterioration amongst the elderly

Abstract

It is known that roughness-smoothness, hardness-softness, stickiness-slipperiness and warm-cold are predominant perceptual dimensions in macro-, micro- and nano- texture perception. However, it is not clear to what extent active tactile texture discrimination remains intact with age. The general decrease in tactile ability induces physical and emotional dysfunction in elderly, and has increasing significance for an aging population. We report a method to quantify tactile acuity based on blinded active exploration of systematically varying micro-textured surfaces and a same-different paradigm. It reveals that elderly participants show significantly reduced fine texture discrimination ability. The elderly group also displays statistically lower finger friction coefficient, moisture and elasticity, suggesting a link. However, a subpopulation of the elderly retains discrimination ability irrespective of cutaneous condition and this can be related to a higher density of somatosensory receptors on the finger pads. Skin tribology is thus not the primary reason for decline of tactile discrimination with age. The remediation of cutaneous properties through rehydration, however leads to a significantly improved tactile acuity. This indicates unambiguously that neurological tactile loss can be temporarily compensated by restoring the cutaneous contact mechanics. Such mechanical restoration of tactile ability has the potential to increase the quality of life in elderly.

Biotribology of the ageing skin—Why we should care

“…Furthermore, the flattening of the DEJ appears to redistribute these stresses away from the junction [180], which is the location of many mechanoreceptors. This result would suggest that changes in skin geometry may play an important part in the deterioration of tactical perception experienced by the elderly described by Skedung et al [178]. Earlier, similar findings were obtained in a comparable three-dimensional finite element study conducted by Garcia-Martinez and Limbert [181] which was later extended [182].…”

“…Tactile perceptual ability is known to decline with age [177][178][179]. As pointed out by Skedung et al [178], besides physical dysfunction, the loss of tactile ability for the elder ly also features an important emotional dimension, and both aspects will gain increasing importance as populations continue to age. As people age and aspire to remain active longer, it is likely that the role of skin-to-skin contact in intimate physical relationships will become an area of importance for many more individuals.…”

“…A precise mechanistic understanding of the already proven influence of physical properties such as surface roughness, texture anisotropy or elastic modulus on tactile perception remains to be established [178]. The basis of sensory tactile perception could be simply described as the conversion of a mechanical stimulus into a neural response which is interpreted by the brain.…”

“…In a systematic experimental study using psychophysical testing, Skedung and colleagues investigated the role of physical surface characteristics of various grades of paper [184] and calibrated wrinkled polymeric surfaces [187] on tactile perception. It was shown that although the coefficient of friction induced by the finger sliding over a surface was dependent upon the surface characteristics, the applied load was unconsciously modulated by human participants to maintain a constant friction force [178,184,187]. In their recent experimental study investigating the mechanisms of tactile sensory deterioration in elderly subjects, Skedung et al [178] suggested that, despite being correlated with reduced elasticity, moisture content and finger friction coefficient, the diminished tactile sensory perception is primarily explained by neural factors through agerelated decline in receptor sensitivity, signal transmission or density.…”

EEG alpha activity increased in response to transcutaneous electrical nervous stimulation in young healthy subjects but not in the healthy elderly

“…Increased brain metabolites of the white matter are related to altered energy metabolism. Previous studies suggested that, along with aging, there was a reduction in the number of nerve cells in the brain and the number of receptors under the skin (Nalbant, 2008;Kalisch, Tegenthoff & Dinse, 2008;Skedung et al, 2018). Most of the studies showed that functional and structural changes in the nerve fibers, thalamus, and cortex occur with aging (Sato, Sato & Suzuki, 1985;Katzman, 1992;Verdú et al, 2000;Kemp et al, 2014).…”