台大心理系

Dynamic object manipulation involves tactile motion perceived through multiple fingerpads. Neuronal tuning properties to direction and orientation in the primary somatosensory (S1) cortex has been delineated but the integration of tactile motion across fingers is not yet known. To this end, we used a multi-digit tactile motion stimulator with scanning balls engraved with square-wave gratings to present tactile motion to two nearby fingerpads and recorded the neuronal responses in areas 3b, 1 and 2 of anesthetized monkeys using multi-channel microelectrode arrays. Specifically, either one (one-finger condition) or both (two-finger condition) of the two fingers were presented with the stimuli, yielding a variety of combination of stimulus direction presented to the two fingers. We found that a proportion of motion-sensitive neurons have two-finger receptive fields. Comparing the activities obtained in one- and two-finger conditions in motion-sensitive neurons, a majority of neurons showed enhancement or suppression of feature selectivity in the two-finger condition. These results indicate that motion integration across fingers is commonly observed in S1 neurons and can be accounted for by nonlinear processing mechanisms.