How Touch Triggers Mechanotransduction in Cutaneous Mechanoreceptors

Understanding the mechanotransduction mechanisms underlying the tactile dimension of skin aging remains an underexplored aspect of dermatological and neurosciences. This investigation introduces a novel mechanosensory responsiveness index, tactile acuity index (TAI), derived from a time-frequency analysis of friction-induced vibrations recorded during controlled touch interactions utilizing the wearable tactile acquisition device (WTAD). By decomposing tactile signals across frequency bands specific to Merkel, Meissner, Ruffini, and Pacinian mechanoreceptors, TAI quantifies both the amplitude and spectral organization of vibrational energy transmitted through the skin.In a first experimental phase, TAI exhibited a clear monotonic decline across seven grades of paper textures, confirming that smoother surfaces produce weaker and spectrally narrower mechanical stimulation, thereby reducing mechanoreceptor recruitment. The strongest correlations were observed for Ruffini (R² = 0.89) and Pacinian (R² = 0.95) receptors, reflecting their sensitivity to macroscopic strain and high-frequency vibration. In an ensuing aging study involving 40 women aged 20-65, TAI revealed a pronounced reduction in mechanosensory activity across all receptor types, with the largest declines in deep mechanotransductive pathways. The associated time-frequency spectrograms further highlighted shorter, lower-amplitude bursts and restricted spectral bandwidths in older skin, indicating a progressive simplification of tactile encoding with age.Together, these findings validate TAI as a quantitative biomarker of tactile vitality, capable of distinguishing between textural and biological sources of sensory decline. By providing receptor-specific insights into mechanotransduction efficiency, this approach establishes a novel framework for diagnosing, monitoring, and potentially restoring tactile function through targeted cosmetic or therapeutic interventions.