Humans use continuous visual feedback from the hand to control fast reaching movements

Abstract

How visual feedback contributes to the on-line control of fast reaching movements is still a matter of considerable debate. Whether feedback is used continuously throughout movements or only in the "slow" end-phases of movements remains an open question. In order to resolve this question, we applied a perturbation technique to measure the influence of visual feedback from the hand at different times during reaching movements. Subjects reached to touch targets in a virtual 3D space, with visual feedback provided by a small virtual sphere that moved with a subject's fingertip. Small random perturbations were applied to the position of the virtual fingertip at two different points in the movement, either at 25% or 50% of the total movement extent. Despite the fact that subjects were unaware of the perturbations, their hand trajectories showed smooth and accurate corrections. Detectable responses were observed within an average of 160 ms after perturbations, and as early as 60% of the distance to the target. Response latencies were constant across different perturbation times and movement speed conditions, suggesting that a fixed sensori-motor delay is the limiting factor. The results provide direct evidence that the human brain uses visual feedback from the hand in a continuous fashion to guide fast reaching movements throughout their extent.

Evidence for a Proprioception-Based Rapid On-Line Error Correction Mechanism for Hand Orientation during Reaching Movements in Blind Subjects

“…Blind subjects must rely exclusively on proprioceptive and tactile inputs to guide their arm and hand movements, whereas normally sighted subjects would intuitively appear to rely mainly on visual feedback in most everyday situations (van Beers et al, 1999(van Beers et al, , 2002Ernst and Banks, 2002;Saunders and Knill, 2003, 2004Sabes, 2003, 2005). Nevertheless, our findings indicate that normally sighted subjects perform as well as blind subjects in these tasks when deprived of vision.…”

“…Human sensorimotor performance often seems introspectively to be dominated by vision, and proprioception appears to play a minor role. However, quantitative studies have shown that both contribute to movement control and that the relative contribution of each is determined by the relative reliability of the information provided by each modality about different aspects of the task (Rossetti et al, 1995;van Beers et al, 1999van Beers et al, , 2002Ernst and Banks, 2002;Sabes, 2003, 2005;Saunders and Knill 2003, 2004Bagesteiro et al, 2006;Sarlegna and Sainburg, 2007).…”

Manual aiming in healthy aging: does proprioceptive acuity make the difference?

“…The primary movement corresponds to the initial pulse toward the vicinity of target. Although this preprogrammed movement phase is traditionally associated with open-loop control (Woodworth 1899), recent work has shown that vision is being used more continuously for the planning and control of limb movements (i.e., impulse control; see also Heath 2005;Khan et al 2002Khan et al , 2006Saunders and Knill 2003). While corrections may occur very early in the movement, the main body of closed-loop control takes place during the homing-in phase.…”

A Structured Rehabilitation Protocol for Improved Multifunctional Prosthetic Control: A Case Study

“…Behavioral studies have shown that by observing the actions of others 7 or using visual cues 8 , able-bodied individuals learn and coordinate new movements. Through a process of observation, understanding and execution of an observed action, individuals are able to imitate the actions of others.…”