LAUSR

This study compared the receptive field (RF) properties and firing rates of neurones in the cutaneous hand representation of primary somatosensory cortex (areas 3b, 1 and 2) of 9 awake, adult macaques that were intensively trained in a texture discrimination task using active touch (fingertips scanned over the surfaces using a single voluntary movement), passive touch (surfaces displaced under the immobile fingertips) or both active and passive touch. Two control monkeys received passive exposure to the same textures in the context of a visual discrimination task. Training and recording extended over 1 - 2yr/animal. All neurones had a cutaneous RF that included the tips of the stimulated digits (D3 and/or 4). In area 3b, RFs were largest in monkeys trained with active touch, smallest in those trained with passive touch, and intermediate in those trained with both, i.e. the mode of touch differentially modified the cortical representation of the stimulated fingers. The same trends were seen in areas 1 and 2 but the changes were not significant, possibly because a second experience-driven influence was seen in areas 1 and 2, but not 3b: smaller RFs with passive exposure to irrelevant tactile inputs compared to recordings from one naïve hemisphere. We suggest that added feedback during active touch and higher cortical firing rates were responsible for the larger RFs with behavioural training; this influence was tempered by periods of more restricted sensory feedback during passive touch training in the active + passive monkeys.