Spatial sensorimotor mismatch increases the excitability of the primary somatosensory cortex: Insight from an...

Under typical conditions, the somatosensory system maintains stable functionality. However, the somatosensory cortex can rapidly reorganize in response to sensory input changes, as demonstrated by studies on sensory deprivation and experience-dependent plasticity. Nevertheless, somatosensory plasticity related to unusual sensorimotor activation, such as spatial incongruence between motor commands and somatosensory feedback patterns during body-environment interactions, remains less investigated. This study aims to extend the evidence for functional reorganization of the somatosensory cortex by investigating the interdependency between motor and somatosensory activity during environmental interactions. We employed an innovative virtual reality (VR) paradigm to investigate the effects of spatial mismatch in sensorimotor loops, dissociating motor and somatosensory components in thespatial domain during sensorimotor interactions. Participants (n = 21) performed two experimental sessions composed of 10 minutes each, involving an interaction task in VR, whereby they interacted with a virtual object with their right hand and received either congruent (on the right hand) or incongruent (on their left ankle) sensory tactile feedback. To assess changes in somatosensory processing, we measured EEG-somatosensory evoked potentials elicited by right median nerve stimulation before and after the task. Our results evidenced increased excitability in the early component of somatosensory evoked potentials (P45) following the incongruent condition, with an opposite trend (decrease of excitability) on the congruent condition. These findings may suggest functional changes in the primary somatosensory cortex (SI), likely driven by the temporal coupling of neural activity from unrelated body parts during the task. However, attentional mechanisms may also contribute to this effect. While preliminary, these results open new avenues for investigating sensorimotor adaptation driven by repeated associative activity between motor and somatosensory cortices during active interactions.