Repetitive somatosensory stimulation shrinks the body image

Current models of mental body representations (MBRs) indicate that tactile inputs feed some of them for different functions, implying that altering tactile inputs may affect mental body representations differently. Here, we tested this hypothesis by leveraging repetitive somatosensory stimulation (RSS), known to improve tactile perception by modulating primary somatosensory cortex (SI) activity, and measured its effects over the body image, body model and superficial schema in a randomized sham-controlled, double-blind crossover study. Results show that repetitive somatosensory stimulation affected the body image, participants perceiving their finger size as being smaller after repetitive somatosensory stimulation. While previous work showed an increase in finger size perception after tactile anaesthesia, these findings reveal that tactile inputs can diametrically modulate the body image. In contrast, repetitive somatosensory stimulation did not seem to alter the body model or superficial schema. In addition, we report a novel mislocalization pattern, with a bias towards the middle finger in the distal phalanges that reverses towards the thumb in the proximal phalanx, enriching the known distortions of the superficial schema. Overall, these findings provide novel insights into the functional organization of mental body representations and their relationships with somatosensory information. Reducing the perceived body size through repetitive somatosensory stimulation could be useful in helping treat body image disturbances.