THE NEURAL SIGNATURES OF TACTILE ATTENUATION AND UNCERTAINTY DURING MOVEMENT

Tactile perception changes when stimuli are applied on moving limbs, leading to a reduction in both, accuracy and precision. Here, we combined electroencephalography (EEG) with psychophysics to assess the neural correlates of tactile attenuation (accuracy) and sensory uncertainty (precision).
Participants completed a two-alternative forced-choice task in which they compared two vibrotactile stimuli: a fixed 55-Hz reference delivered either during movement or, in a Control condition, without movement, and a variable comparison stimulus presented after movement. Experimental conditions included Active, Passive Predictable, and Passive Unpredictable movement. Psychometric functions were used to estimate the point of subjective equality (PSE) and just noticeable difference (JND). Somatosensory event-related potentials (ERPs) at electrode Cz were quantified using peak-to-peak amplitudes (50–300 ms) as well as component-specific amplitudes (P50, N80, P100). Time–frequency analyses over central–parietal channels assessed trial-to-trial variability in THETA, ALPHA, BETA, and GAMMA bands.
Movement robustly reduced PSEs and attenuated somatosensory ERPs relative to Control. ERP attenuation was absent at P50 but pronounced at N80 and P100, suggesting predictive modulation at later stages of cortical processing. Crucially, neural signatures dissociated perceptual bias and precision: PSE shifts covaried with low-frequency activity (THETA/ALPHA/BETA), whereas agency-related differences were most pronounced in BETA and GAMMA bands. Notably, increased GAMMA-band variability selectively predicted larger JNDs under conditions of uncertainty.
Together, these findings demonstrate that tactile attenuation and sensory uncertainty are supported by distinct neural mechanisms and support a hierarchical model in which later somatosensory stages integrate predictive and agency-related signals to shape both perceptual bias and precision.