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The effect of varying the visual context on trajectory planning
and perceptual awareness of one’s own performance 1 Psychology and Neurocognition
Laboratory (CNRS UMR-5105),
Grenoble, France
Richard Palluel-Germain1, Frederic Boy1, Jean-Pierre Orliaguet 1,
Y. Coello2 2 URECA, Université Lille3, 59653
Villeneuve d'Ascq, France.
The effect of varying the visual context on trajectory planning
In order to define the nature of the variables used by the motor system to plan goal directed movements, a large set of behavioral studies examined
trajectories carried out by the hand in a reaching movement. Concerning 3 dimensional (3D) movements it has been shown that the shape of the trajectory,
carried out by the hand, was curve and depended on movement direction (e.g., Atkenson & Hollerbach, 1995; Desmuget et al., 1997; Osu et al., 1997). This
suggests that 3D movements are planned in intrinsic space in which the control parameter is the position of each of the joints contributing to the movement.
The goal of the present study is to show that the visual constraints generated in situations of remote visual control could affect trajectory planning. More
precisely, we hypothesize that 3D movements executed with a 2D visual feedback are planned to be straight in extrinsic space.
Method Results
10 particpants were asked to perform 3D pointing A path curvature index (PCI) was calculted. A
movements toward dots (19 mm circles) located at Direct Visual Indirect Visual significant interaction was observed between visual
20°, 40°, 60° and 80° to the right with respect to the Feedback (DVF) Feedback (IVF) feedback and target eccentricty: Path curvature
sagital axis and at 20 cm from the starting position. was influenced by targets eccentricity only in the
DVF condition and trajectories are straighter in the
IVF Condition.
Each subject performed pointing movements in an
Indirect and in a Direct Visual Feedback condition Conclusion (1)
(respectively, IVF and DVF conditions). In the IVF Under direct vision, 3D pointing movements
condition direct vision of the workspace was evidenced a curvature that increased as a function
precluded. A video camera recorded arm of target eccentricity. when similar movements are
displacements (1:1 spatial relationship) and executed in a indirect visual feedback condition
transmitted continuously and in real time movement (video-controlled pointing movements), trajectories
images on a video screen located 0.50 cm from the tended to be straight whatever the direction of the
head. In the DVF condition subjects directly viewed movement, suggesting a control of hand
a similar arrangement of the workspace. In each displacement in extrinsic coordinates, as
condition ten pointing movements were performed movements performed in a two-dimensional space.
toward each target This variation of hand path, depending on the direct
or indirect feedback condition, suggests that
perceptual constraints may dominate
biomechanical constraints.
The effect of varying the visual context on perceptual awareness of one’s own performance
The goal of the present study is to show that the sensorimotor system makes a differential use of visual and internal (proprioception and efferent-copy) signals
when evaluating either the spatial or the dynamical components of our motor response carried out under a remote visual feedback. Visual bias is expected to be
more influential when evaluating the spatial aspect of the workspace than when evaluating the dynamical components of the response.
Method and results
I Sensorimotor adaptation II Evaluation Tasks
Participants had to perform 20 three-dimensional pointings to a target Once subjects were adapted to the visual bias :
disposed on the table in two conditions of presentation of the visual feedback: In the Spatial Evaluation task (SE), subjects were asked to point to the
In the 0° condition In the 45° condition the initial hand location and to trace on the table the direction of the movement
(control) the visual camera was rotated by 45° they carried out (i.e. Evaluating Where the movement was performed).
hand-to-target gap clockwise so that the hand and In the Movement Reproduction (MR) task, after being rapidly replaced on
was aligned with the the target appeared on the the starting position, they were asked to reach for the target in a single
actual gap screen as displaced in opposite
movement (i.e. Evaluating How the movement was performed)
0° 45° direction
Spatial Evaluation task
Condition 45° Condition 0°
In the 1st trials of the 45° condition motor
performance is influenced by the biased
Individual performance in the
5 cm visual feedback. evaluation of the starting
position
But, after 20 trials, motor performance is
adapted to the visual-kinesthetic Mean angular direction of the
45° movement evaluation
discordance (straight trajectories) 0°
45°
0°
In the 45° condition both starting position and movement direction are judged
according to visual signals.
Conclusion (2)
We found dissociation in the influence of visual information in two non-visual Movement reproduction
45°
evaluations of previous sensorimotor performance. We propose that when Ipsilat. Arm: Similar pattern of error 0°
judging one’s own motor performance, intrinsic (proprioception and efferent- in both 45° & 0° conditions (4.7 deg
copy related signals) or extrinsic (visual) signals are electively processed & 0.28 deg respectively). Production
of unbiased estimates (i.e. close to
depending upon the dimension of the movement that is evaluated (spatial or
the veridical direction).
dynamical aspects). Perceiving one’s own motor production relies on
separate sensory integration processes that depend on the dimension of Contral. Arm: Different pattern of
action that is judged, suggesting a dissociation between perceptual and error for 45° (-26.8 deg) with respect
motor awareness. to the 0° condition (3.85 deg)
References
Boy, F., Palluel-Germain, R., Orliaguet, J.P., Coello, Y.(2005). Dissociation between "where" and "how" judgements of one's own motor performance in a video-controlled reaching task., Neuroscience Letters, 386.
Palluel-Germain, R., Boy, F., Orliaguet, J.P., Coello, Y. (2004). Visual and motor constraints on trajectory plannig in pointing movements. Neuroscience Letters, 372.
