Skin feel in the brain: Oscillatory dynamics of active touch are modulated by commercial soap products.

Abstract

Previous research has demonstrated changes in neural oscillations associated with varying levels of roughness during active-touch exploration of surfaces. In the present study, we aimed to investigate changes in neural oscillatory activity and softness perception during touch exploration of skin. Two experiments were conducted. Study 1 evaluated active touch of artificial skin samples mounted to a purpose-built touch sensor, whereas Study 2 investigated active stroking of one's own forearm. In both experiments, the substrates were treated with commercially available bar soaps to deliver either a soft or draggy skin feel. Oscillatory brain activity was measured using a 129-channel electroencephalography system. In 31 participants, changes in oscillatory band power were evaluated in relevant frequency bands during touch exploration periods. For the artificial skin study, the soft condition led to lower alpha-band power over bilateral somatosensory cortices, which has previously been proposed as a marker of reduced roughness, compared to the draggy condition. Similar results were obtained during the self-touch paradigm, which additionally led to reduced theta-band changes over the frontal and central-parietal electrodes indicating modulation of activity involved in affective (pleasant) touch. Using a novel and highly controlled experimental approach using a novel artificial skin paradigm and active exploration during self-touch of participants own skin, we were able to demonstrate for the first time the neural correlates associated with softness perception of skin and their impact on brain activity associated with affective touch, thereby advancing our understanding of brain oscillatory activity during active-touch exploration of skin. (PsycInfo Database Record (c) 2026 APA, all rights reserved).