Institute of Cognitive Neuroscience Department of Psychology
de s T IN SI TU
Manos Tsakiris†, Patrick Haggard†, Nicolas Franck‡, Nelly Mainy‡ & Angela Sirigu‡
COGNITIVES
This study was funded by the Experimental Psychology Society, UK
† Institute of Cognitive Neuroscience, UCL, London, ‡ Institut des Sciences Cognitives, CNRS, Lyon
Abstract We manipulated efferent information in order to investigate the relative contributions of efferent and afferent (proprioceptive) information to self-recognition. Self-recognition was significantly more accurate when participants were the authors of the action, even though there was a perfect matching between the proprioception and the visual feedback across conditions. Efferent information therefore plays a key role in self-recognition, even when subjects judge the effect of an action on a spatially remote body part.
I. Introduction How Do We Recognize Ourselves ?
The “Williams” Debate
Past & Present
Body (peripheral or afferent)
(see Petit, 2002)
Daprati et al. (1997) Æ Self-Recognition in Schizophrenics
W James : Knowledge of our movements originates from peripheral information
Sirigu et al. (1999) Æ Self-Recognition in Apraxics
W Wundt : Central efferent copy of the motor command
In these studies, afference and efference were present across all conditions, and therefore, it was not possible to establish their respective roles. The question whether the performances observed were due to a better integration of visuo-proprioceptive information or due to use of fine efferent information could not be conclusively answered.In the present study, efferent information was manipulated by design!
The respective roles of afferent and efferent information in self-recognition are yet to be determined…
Methods & Materials Both hands were covered with identical gloves Participants and experimenter always performed the same movement. 4 blocks, each block with 30 trials, 15 trials for each visual feedback condition (own/other), randomized Image duration = 2000ms (go-signal at 500ms) N=18 right-handed (+0.87), mean age 24.1
Cam 1
Cam 2
Image
Subject
Experimenter
What the subject sees, looks like her right hand, and what she feels, looks like what the hand on the screen feels. Afferent information originating from their right hand was identical, but the efferent information was manipulated by design.
Image
Subject
Externally-generated Action
“Whose hand did you see?”
Experimenter
2000ms
Cam 1
Go-Signal : Action Cam 1
d lf ate Se ener n G ctio A ly al rn d te rate x e E en n G ctio A
View Other’s Hand
Cam 2
Visual Feedback Own Hand Other’s Hand
Cam 1
Self-generated Action
(2x2 Factorial)
Authorship of Action
Across conditions and trials :
View Own Hand
II. Experimental Design
Image
Own hand
or
Other’s hand
Image
500ms
Image Onset : Rest Own hand
Subject
Experimenter
Subject
or Other’s hand
Experimenter
0
tim e
Intention Efference copy Predictions of the motor system
van den Bos & Jeannerod (2003) Æ Self-Recognition in Normals
Cam 2
Action (central or efferent)
Cam 2
Proprioception : sense of the self par excellence Multisensory integration
III. Results & Analysis 0.96 0.91
The d’ primes were submitted to the non-parametric Wilcoxon matched-pairs-tests.
View OWN Hand Condition
**
0.8
Self-generated vs. Externally-generated
Z=-2.062, p<0.05
0.6
0.62
View Other's Hand Condition 0.4
Control Experiment
0.45
Self-generated vs. Externally-generated
Z=-2.635, p<0.01
0.2
externally-generated action
"view own hand"
self-generated action
Could the visual stimulus carry information which is confounded with efference? Visual differences between the kinematics of a self-generated displacement vs. an externally-generated displacement were not significant.
0
self-generated action
Differences between self-generated and externally-generated conditions were significant (Z=2.635, p<0.005, 1-tailed)
externally-generated action
"view other's hand"
IV. Discussion
The Specific Role of Efference
Differential contribution of afferent and efferent information in self-recognition.
Efference & Time : Advantage in Monitoring the Timing of SensoryMotor Events
Self-recognition was significantly better when efferent information was present, for both the “view own hand” and “view other’s hand” conditions.
The “raw” efferent information provides significant timing information, even before it is processed by the forward model (point 1).
By comparing only visual and proprioceptive signals, participants were unable to accurately discriminate between self and other, and they performed at chance! Participants over-recognized themselves in the case of an externally-generated action, by misattributing the other’s hand to themselves.
The specific processing of efference within the forward model generates accurate predictions for the kinematic parameters of the movement. These predictions facilitate and improve the integration of visual and proprioceptive afference (point 2). Motor Plan
Passive Displacement
Motor Command
V. Conclusion
Efference Forward Model 2
Self-recognition was significantly more accurate when efferent information was present, even though there was
1 Proprioceptive Afference
References Daprati et al. (1997). Looking for the agent : an investigation into consciousness of action and selfconsciousness in schizophrenic patients. Cognition, 65, 71-87. Sirigu et al. (1999). Perception of self-generated movement following left parietal lesion. Brain, 122, 1867-74. Tsakiris et al. A specific role for efferent information in self-recognition. Cognition, under revision. van den Bos E & Jeannerod M (2002). Sense of body and sense of action both contribute to selfrecognition. Cognition, 85, 177-187.
Parmigianino, Self-Portrait in a Convex Mirror, c. 1524
Efference & Kinematics : Modulation of the On-line Comparison of Vision and Proprioception, by providing fine temporal and kinematic details
ICS, Lyon, September, 2002
mean correct rate
Signal Detection Analysis
Non-parametric Wilcoxon matched-pairs-tests
**
1
congruent visual-proprioceptive feedback across conditions, and despite the fact that it was the effect, and
Visual Afference
ES NC IE SC
Afferent and Efferent Contributions To Self-Recognition
not the action per se, that the subjects were watching.
