P1254325689kwTpz - PowerPoint PPT Presentation

Title: P1254325689kwTpz


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 The self and its brain  Marc
Jeannerod Institut des Sciences Cognitives,
Lyon jeannerod_at_isc.cnrs.fr
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Humans are both conscious and unconscious
beings. Can we consciously control our
behavior? How is this possible if part of our
behavior is generated unconsciously? If our
consciousness does not control our behavior, what
is it for? Here I will describe experiments
illustrating the difference between several
modalities of our self the automatic self and
the cognitive self, and will try to bridge the
gap between the two
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1. Conscious vs unconscious processing of visual
stimuli. Processing the same visual stimulus
yields widely different results whether the
task consists in conscious visual perception or
in automatic visuomotor interaction.
The Titchener illusion
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2. Conscious vs unconscious processing of ones
own actions What do we know about the actions we
perform? Here I will show an experiment where
the subject consciously performs a goal-directed
action, but remains unaware of the movements he
makes for achieving the goal
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The visuomotor conflict paradigm
Fourneret et Jeannerod, 1998
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error
verbal response
A2
0 20
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These experiments by Fourneret and his
colleagues make three important points - What
the agent believes does not correspond to the
movements he actually produces. - As the
discordance between the conscious content and the
unconscious performance increases, the agent
suddenly becomes aware of his motor
performance - The  consciously controlled 
performance is less accurate than the unconscious
one.
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A model for explaining unconscious visuomotor
performance An anticipation of the final outcome
(predicted state) is used for matching the actual
state with the desired state. In case of
mismatch, automatic adjustments are made. If the
mismatch becomes too large, the system shifts to
the conscious mode
Desired state
Inverse model
Predicted state
Movement
Actual state
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3. The next question is about the role of
consciousness (when it happens) Can
consciousness be used for controlling our
behavior? This is a highly debated topic, which
concerns issues such as free will, for
example. Here I will describe the classical
Libet experiment (1983) which represents another
demonstration of the dissociation
between conscious and unconscious modalities of
functionning
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The readiness potential, an index of covert brain
activity preceding the performance of a willed
movement
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In the Libet experiment, the subject is
instructed to willingly move one finger and to
indicate when he becomes aware of having intended
to move (W)
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4. What is the brain signature of the conscious
will? Many experimental data point to the
prefrontal cortex as the prime mover in voluntary
actions
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Activation of left dorsolateral prefrontal cortex
during voluntary action
Spence, S.A. Frith, C.D. ( 1999) Journal of
Consciousness Studies Frith, C. D. et al (1991)
Proceedings of the Royal Society
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Impairment of voluntary actions following frontal
lobe lesion or dysfunction Athymhormia, abulia,
loss of self-activation Utilization
and imitation behavior Hysterical
paralysis
Loss of control of utilization tendencies in a
patient with lesion of prefrontal cortex
Lhermitte, F. (1983) Brain, 106, 237
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Hysterical paralysis of the left leg
Neuroimagery of (normal) voluntary movements of
the right leg
Marshall, J.C. et al (1997) Cognition, 64, B1-B8
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Hysterical paralysis of the left leg attempt to
move the left leg
Marshall, J.C. et al (1997) Cognition, 64, B1-B8
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5. Consciousness is a delayed phenomenon. It
arrives too late for influencing behavior on
line The role of consciousness might be to fill
the cognitive gap between covert and overt
aspects of our behavior - To establish a
narrative continuity across time frames - To
provide a narrative coherence between previous
and present actions - To establish a cognitive
consonance - To endorse decisions which have been
taken automatically - To provide a sense of
agency, even if illusory In that sense, the
causal connection between our thoughts and our
behaviour is only apparent, it is a cognitive
illusion. Like visual illusions, the illusion of
causal consciousness contradicts reality
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D. Wegner, 2001
Action
Thought
Cause of thought
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Cause of action
Time
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An illustration of this concept of an illusion
of free will is provided by recent neuroimaging
experiments in normal subjects. The example of
moral judgements
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The time taken to give a response to a moral
dilemma depends on the emotional content of the
situation. This time is longer when the dilemma
directly involves the participation of the
subject.
Greene et al, Science, 2001, 293, 2105
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Greene et al, Science, 2001, 293, 2105
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The automatic self is subpersonal its operations
are little if at all accessible to conscious
report. It is based on procedures which operate
implicitly By contrast, the narrative self is
personal. Its operations can be verbalised and
described explicitly Where is the real self? In
the brain which does the task, or in the subject
who ignores the procedure and believes something
else? What is the real self the automatic one,
or the conscious one?