Contribution of tactile information to accuracy in pointing movements

We examined the contribution of tactile cues to accuracy during point-to-po int movements. We used a task in which the experimenter guided either the l eft or right hand of the subject to a spatial location during the reference movement. During the subsequent test movement subjects were asked to point with the right hand to the remembered location without vision. Subjects co ntacted the target with their fingertip either during the reference movemen t, both the reference and test movements, or neither movement (i.e., the fi ngertip was held above the target surface). To differentiate between the co ntribution of tactile and proximal deep pressure information, the left inde x finger was anesthetized in a subsequent experiment. When subjects contact ed the surface with the fingertip of the reference hand alone, error in mov ement direction decreased. When subjects made fingertip contact during the reference and test movements, gain error also decreased. Anesthesia of the fingertip degraded accuracy, suggesting that tactile information, independe nt of information from proximal deep pressure receptors, influenced movemen t accuracy. Thus, tactile information contributed to accuracy in pointing m ovements. We suggest that forces at fingertip contact may provide informati on regarding the orientation of the finger and forearm in space, which is u sed to replicate final arm posture. In addition, tactile cues at the beginn ing and end of the movement may be used to scale movement amplitude.