Fast and fine-tuned corrections when the target of a hand movement is displaced

Abstract

To study the strategy in responding to target displacements during fast goal-directed arm movements, we examined how quickly corrections are initiated and how vigorously they are executed. We perturbed the target position at various moments before and after movement initiation. Corrections to perturbations before the movement started were initiated with the same latency as corrections to perturbations during the movement. Subjects also responded as quickly to a second perturbation during the same reach, even if the perturbations were only separated by 60 ms. The magnitude of the correction was minimized with respect to the time remaining until the end of the movement. We conclude that despite being executed after a fixed latency, these fast corrections are not stereotyped responses but are suited to the circumstances.

Movement Adjustments Have Short Latencies Because There is No Need to Detect Anything

“…It also explains why movement selection does not play a role in generating adjustments: the response is fully determined by the gain and actual positions. The assumed flexibility of the gain is in line with results showing that the initial adjustment is to some extent under voluntarily control (Day & Lyon, 2000), and later perturbations result in more vigorous adjustments (Liu & Todorov, 2007;Oostwoud Wijdenes et al, 2011). More complicated responses such as moving in the opposite direction than the jump (Day & Lyon, 2000;Johnson et al, 2002) or stopping the movement as soon as the target jumps (Pisella et al, 2000) are possible, but their latency is longer; they only kick in after the initial adjustment in the direction in which the target jumped.…”

“…Oostwoud Wijdenes et al (2011) tested whether the latency depended on the timing of the perturbation in a fast pointing movement, and found that the timing of the perturbation did not influence the response latency (which was always about 100 ms). The earliest perturbations occurred about 70 ms before movement initiation (100 ms after initial target appearance), so the agonist will have been active at the time of the adjustment.…”

“…The goal location is continuously updated on the basis of visual information . The gain is to some extent under voluntarily control (Day & Lyon, 2000), and increases during the movement so that later perturbations result in more vigorous adjustments (Oostwoud Wijdenes et al, 2011).…”

Gravity Affects the Vertical Curvature in Human Grasping Movements

“…This reasoning assumes that a possible decrease in precision during the early phase of the movement, caused by the higher muscle force needed to launch the hand upward, does not outweigh the increase in precision gained at the end of the movement. We base this assumption on the finding that movements are constantly adjusted on the basis of feedback (Oostwoud Wijdenes, Brenner, & Smeets, 2011;Paulignan, Mackenzie, Marteniuk, & Jeannerod, 1991;Saunders & Knill, 2003) and there is much more time to compensate for errors that occur in the early phase of the movement than for ones that occur in a late phase of the movement.…”

Automatic Correction of Hand Pointing in Stereoscopic Depth

“…The hand grip aperture was also shown to make smooth modifications when the target's size changed2021. Particularly, the automatic adjustments of hand reaching and pointing movements were observed in the studies on lateral jumps34141516171819. Pisella et al3 studied the “GO” and “STOP” tasks in response to location jumps and found that the movement time of full corrections could occur within a time range of 200 ms to 240 ms despite task types.…”