Reconstructing neural representations of tactile space in the sensorimotor areas

Psychophysical experiments have demonstrated large and highly systematic perceptual distortions of tactile space. Several behavioural studies have investigated such distorted representations, however, the neural bases of such distortions are unknow. Here I will present a study in which we examined the neural basis of tactile distance perception by analysing activity patterns induced by tactile stimulation of nine points on a 3 x 3 square grid on the hand dorsum. I will describe empirical evidence showing that the primary somatosensory and motor cortices, rather than higher-level brain areas, are critical to estimating distances between tactile stimuli on the hand dorsum. By combining functional magnetic resonance, Procrustes alignment, and multidimensional scaling, we reconstructed the shape of skin space in the brain. Strikingly, the shape of the skin that we reconstructed from neural data matches the distortions we found at the behavioural level, providing strong evidence that early sensorimotor areas are critical for the construction of tactile space