Thermal modulation of tactile perception in young and older adults: Local and remote effects

Thermal and tactile sensations interact in shaping how we perceive our environment. These interactions rely on the activity of distinct but converging somatosensory pathways and may be altered by aging. In this study, we investigated how innocuous thermal stimulation modulates tactile sensitivity in healthy young and older adults. Mechanical detection thresholds (MDTs) were measured on the dorsal hand using a standardized protocol, while non-painful thermal stimuli were applied as follows: cold (20 °C) and warm (40 °C) either ipsilaterally or contralaterally to the testing site, and a neutral temperature (32 °C) applied only ipsilaterally. Two thermal stimulation methods were used: a localized contact thermode and a global air-based thermal chamber. Results showed that cold stimulation applied ipsilaterally to the tested hand significantly increased MDTs in both age groups, indicating reduced tactile sensitivity. This effect was consistent across stimulation methods, but stronger with the thermode and more pronounced in older adults. Neither warm nor contralateral thermal stimulation produced significant modulation, and neutral temperature had no effect, confirming the specificity of the cold-induced modulation. These findings indicate that cold input inhibits tactile sensitivity in a spatially and modality-specific manner. The absence of contralateral effects supports a segmental, rather than supraspinal, mechanism of thermo-tactile interaction. These results contribute to our understanding of age-related changes in multisensory integration and may inform the development of sensory assessment tools and therapeutic approaches tailored for older individuals.