Prsentation PowerPoint

1
The effect of varying the visual context on
trajectory planning and perceptual awareness of
ones own performance
1 Psychology and Neurocognition Laboratory (CNRS
UMR-5105), Grenoble, France
Richard Palluel-Germain1, Frederic Boy1,
Jean-Pierre Orliaguet1, 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
movements toward dots (19 mm circles) located at
20, 40, 60 and 80 to the right with respect
to the sagital axis and at 20 cm from the
starting position. Each subject performed
pointing movements in an Indirect and in a Direct
Visual Feedback condition (respectively, IVF and
DVF conditions). In the IVF condition direct
vision of the workspace was precluded. A video
camera recorded arm displacements (11 spatial
relationship) and transmitted continuously and in
real time movement images on a video screen
located 0.50 cm from the head. In the DVF
condition subjects directly viewed a similar
arrangement of the workspace. In each condition
ten pointing movements were performed toward each
target
A path curvature index (PCI) was calculted. A
significant interaction was observed between
visual feedback and target eccentricty Path
curvature was influenced by targets eccentricity
only in the DVF condition and trajectories are
straighter in the IVF Condition.
The effect of varying the visual context on
perceptual awareness of ones 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 disposed on the table in
two conditions of presentation of the visual
feedback

• Once subjects were adapted to the visual bias
• In the Spatial Evaluation task (SE), subjects
  were asked to point to the initial hand location
  and to trace on the table the direction of the
  movement they carried out (i.e. Evaluating Where
  the movement was performed).
• In the Movement Reproduction (MR) task, after
  being rapidly replaced on the starting position,
  they were asked to reach for the target in a
  single movement (i.e. Evaluating How the movement
  was performed)

In the 0 condition (control) the visual
hand-to-target gap was aligned with the actual gap
In the 45 condition the camera was rotated by
45 clockwise so that the hand and the target
appeared on the screen as displaced in opposite
direction
0
45
Spatial Evaluation task
Condition 45
Condition 0
In the 1st trials of the 45 condition motor
performance is influenced by the biased visual
feedback.
But, after 20 trials, motor performance is
adapted to the visual-kinesthetic discordance
(straight trajectories)
45
0
Conclusion (2)
Movement reproduction
We found dissociation in the influence of visual
information in two non-visual evaluations of
previous sensorimotor performance. We propose
that when judging ones own motor performance,
intrinsic (proprioception and efferent-copy
related signals) or extrinsic (visual) signals
are electively processed depending upon the
dimension of the movement that is evaluated
(spatial or dynamical aspects). Perceiving ones
own motor production relies on separate sensory
integration processes that depend on the
dimension of action that is judged, suggesting a
dissociation between perceptual and motor
awareness.
Ipsilat. Arm Similar pattern of error in both
45 0 conditions (4.7 deg 0.28 deg
respectively). Production of unbiased estimates
(i.e. close to the veridical direction). Contral.
Arm Different pattern of error for 45 (-26.8
deg) with respect 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.