Target and hand position information in the online control of goal-directed arm movements

Abstract

The present study compared the contribution of visual information of hand and target position to the online control of goal-directed arm movements. Their respective contributions were assessed by examining how human subjects reacted to a change of the position of either their seen hand or the visual target near the onset of the reaching movement. Subjects, seated head-fixed in a dark room, were instructed to look at and reach with a pointer towards visual targets located in the fronto-parallel plane at different distances to the right of the starting position. LEDs mounted on the tip of the pointer were used to provide true or erroneous visual feedback about hand position. In some trials, either the target or the pointer LED that signalled the actual hand position was shifted 4.5 cm to the left or to the right during the ocular saccade towards the target. Because of saccadic suppression, subjects did not perceive these displacements, which occurred near arm movement onset. The results showed that modifications of arm movement amplitude appeared, on average, 150 ms earlier and reached a greater extent (mean difference=2.7 cm) when there was a change of target position than when a change of the seen hand position occurred. These findings highlight the weight of target position information to the online control of arm movements. Visual information relative to hand position may be less contributive because proprioception also provides information about limb position.

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

“…This finding is all the more striking because control of hand orientation during reaching could be prone to execution errors due to inaccuracies in outgoing motor commands and to passive mechanical perturbations of the hand away from its desired orientation. Our findings are consistent with other studies that suggested a role for proprioception in the on-line correction of hand direction and distance in response to visual perturbations of target or hand position (Sarlegna et al, 2003(Sarlegna et al, , 2004Bagesteiro et al, 2006).…”

Can the Human Brain Predict the Consequences of Arm Movement Corrections When Transporting an Object? Hints from Grip Force Adjustments

“…In both situations, the large, consciously perceived target displacements resulted in arm movement corrections initiated with a similar latency. This latency, within the range of values reported previously (Georgopoulos et al, 1981;Sarlegna et al, 2003), presumably reflects voluntary rather than automatic modifications of the initial motor plan (Day and Lyon, 2000;Desmurget et al, 2004;Johnson and Haggard, 2005). We interpret the lack of grasp/no grasp difference as possible evidence that the predictive mechanisms engaged in the control of grip force are low-demanding processes.…”

“…This paradigm was selected because it elicits fast motor corrections that allow reaching the displaced target before movement offset (Day and Brown, 2001;Prablanc et al, 2003;Sarlegna et al, 2003). An original feature of the present study was that arm movements had to be performed while holding an object.…”

Reaching in Depth: Hand Position Dominates over Binocular Eye Position in the Rostral Superior Parietal Lobule

“…It has been suggested that the control of movement distance is mainly based on proprioceptive signals and less on visual information, which is regarded as more important for the control of movement direction (Sainburg et al, 2003;Sarlegna et al, 2003;Bagesteiro et al, 2005). This is consistent with the evidence that these two parameters seem to be specified separately in the brain (Flanders et al, 1992;Lacquaniti et al, 1995;Georgopoulos, 2000).…”