Effects of prediction and attention on tactile precision in somatosensory gating.

Tactile sensitivity is reduced when the limb is in motion, a phenomenon known as somatosensory gating. In a previous study, we demonstrated that discrimination precision but not perceived intensity differed between active and passive movements. Here, we asked whether and how spatial attention modulates tactile precision in active and passive movements. Participants judged the relative intensity of two vibrations while the arm was still, actively moved, or passively transported by a movable platform. Visual attention was directed either to the movement start or goal position. Perceptual bias was reduced during both active and passive movement, independent of attentional allocation. In contrast, precision remained stable during active movement but declined during passive movement when attention was directed to the movement start. However, when attention was focused on the movement goals, precision was also high when doing passive movements. These findings indicate that during active movements, predictions based, likely on an efference copy, ensure tactile precision, whereas passive movements require spatial attention directed to the movement goal.