Degraded vision affects mental representations of the body

ABSTRACT The mental representations of the body depend on current perceptions, building on more reliable sensory inputs and decreasing the weight of less reliable afferences. While somatosensory manipulations have been repeatedly investigated, less is known about vision. We hypothesized that a decrease in visual input may result in an augmented relevance of somatosensation to mentally represent the body. 29 neurotypical participants performed mental rotation of hand images, while image visibility was manipulated: keeping the same background (grey), the contrast was decreased by 60% (Degraded Vision) with respect to Baseline. Results showed that Degraded Vision (1) slowed down the mental rotation of hand images typically sensitive to degrees of rotation (dorsum), and (2) established a rotation-dependent latency profile for the mental rotation of hand images that are not typically affected by rotation (little finger). Since the sensitivity to rotation indicates the recruitment of visual or somatosensory strategies to mentally represent the body, our findings indicate that in presence of degraded visual input, somatosensation had a heavier weight than vision in mental rotation. This suggests a relative shift from a pictorial representation of the body (body image) to a somatosensory one (body schema) as a function of the most reliable/available sensory input.