Corrective loops involved in fast aiming movements: effect of task and environment

Abstract

In daily living, we continuously interact with our environment. This environment is rarely stable and living beings show remarkable adaptive capacities. When we reach for an object, it is necessary to localize the position of this object with respect to our own body before programming an adequate arm movement. If the target remains stable, the programmed movement brings the hand near the target. However, what happens when the target suddenly jumps to another position in space? The aim of this work was to investigate how rapid aiming movements are corrected when the target is displaced close to movement onset. Our results reveal that rapid movements can be modified and that the efficiency of trajectory amendments vary according to task (directional or direction/amplitude pointings) and environment (structured or darkness). We were most interested in the specific role played by peripheral and/or central feedback information (efferent copy) in the control of aiming movements. The results suggest that the two types of loops are complementary in movement regulation. However, their predominance varies according to the nature of the task at hand.

Visual guidance of arm reaching: Online adjustments of movement direction are impaired by amplitude control

“…While movements were not particularly rapid in Liu and Todorov (600 to 900 ms), their findings are remarkably consistent with previous studies on fast arm movements (Blouin et al, 1995a(Blouin et al, , 1995bTurrell et al, 1998). Indeed, Blouin et al (1995a) observed large directional adjustments toward the displaced target when participants only had to control the direction of shooting, rapid movements (duration of È200 ms).…”

“…It should be noted that while movement duration and mean velocity matched those of Experiment 1, peak velocity was higher in Experiment 1 than in Experiment 2 because of different task constraints (respectively 2.8 m/s and 1.6 m/s as shown by off-line analyses). However, several studies have shown that online adjustments of movement trajectory can be made for movements whose peak velocity exceeds 2 m/s (e.g., Boulinguez & Nougier, 1999;Flanagan, Ostry, & Feldman, 1993;Turrell, Bard, Fleury, Teasdale, & Martin, 1998). Thus, we preferred similar movement durations (È350 ms) in both experiments rather than similar peak velocities, as the latter option would have yielded large differences in movement durations.…”

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

“…Our finding that the latency of the response is constant also implies that movements are not controlled by strategy 2, according to which adjustments are postponed to a late stage of the movement, as suggested by many who assume that the initial part of the movement is under open-loop control, with online control emerging during the deceleration phase (Elliott et al 2001; Komilis et al 1993; Turrell et al 1998; van der Meulen et al 1990; Woodworth 1899). We found movement corrections near movement initiation.…”

Large-Field Visual Motion Directly Induces an Involuntary Rapid Manual Following Response

“…3): the latency differences in the three subjects were 1, Ϫ1, Ϫ4 ms, respectively. These latency differences are, however, much shorter than the time differences between the ocular movement and hand movement reported in previous studies (Turrell et al, 1998;Engel et al, 2000;Soechting et al, 2001), in which efference copy of the ocular motor command is deemed to be used as an arm motor command. Moreover, considering the transmission time from the motor cortex to the arm muscles [11-12 ms for biceps brachii, 14 -15 ms for the brachioradialis, observed by transcranial magnetic stimulation (Abbruzzese et al, 1994)] and the delay from the oculomotor neuron activity to the eye movement [6 -7 ms, which is estimated from and Gomi et al (1998)], the motor command for the MFR would be generated simultaneously with that for the OFR or even earlier.…”

“…Recent eye-hand coordination studies (Prablanc et al, 1979;Herman and Maulucci, 1981;Biguer et al, 1982;Fischer and Rogal, 1986;Henriques et al, 1998Henriques et al, , 2003Turrell et al, 1998;Engel et al, 2000;Soechting et al, 2001;Ariff et al, 2002) suggest a couple of possibilities that the MFR could be affected by the OFR, both of which were indeed elicited by visual motion in our experimental setup.…”