Multisensory modulations of bodily senses

The human perceptual system is essentially multisensory. I studied how vision modulates the bodily senses, particularly the multisensory modulation of the visual context on touch and pain. I used a combination of behavioural, neurostimulation and electro-physiological techniques to investigate the neural correlates of contextual multisensory interactions. I first demonstrated that the visual context modulates touch: task-irrelevant visual arrowheads influence spatial representations of stimuli perceived by touch, depending on the spatial coincidence between visual and tactile sensory inputs (Chapter 1). These visuo-tactile interactions do not require spatial attention to occur, being preserved in brain-damaged patients with attentional deficits (Chapter 2). Importantly, the occipito-temporal cortex is causally involved in merging visual and tactile inputs in multisensory representations of shape (Chapter 3). I then showed that the visual context can also modulate pain perception: in particular, I demonstrated that viewing one's own body in comparison to viewing an object is analgesic, increasing contact heat-pain thresholds of 3.2 °C (Chapter 4). This 'visually-induced analgesia' is reflected in enhancements of sensory cortical rhythms, possibly due to active inhibition of somatosensory processing (Chapter 5). In addition, changes in the excitability of the extrastriate visual cortex are involved in multisensory modulation of pain (Chapter 6). Taken together, these results indicate that the visual context modulates the processing of touch and pain. Visual cortical areas mediate visual-somatosensory contextual interactions.