Les aires prémotrices - Neurosciences-comportement

Les aires prémotrices
Avant les années 2000 :
• aire motrice supplémentaire ;
• cortex pré-moteur.
Aujourd’hui, au moins 7 aires différentes, mais pas de consensus…
• 2 aires motrices supplémentaires (AMS et pré-AMS) ;
• 2 aires prémotrices (dorsale et ventrale) ;
• 3 aires motrices cingulaires.
Potentiel de préparation motrice
Average event-related potential (ERP) amplitude across all
electrodes as a function of time and group.
The gray area indicates the time
range during which the two
groups
started
to
differ
significantly
and
the
late
readiness potential began. The
red and the blue circles in the
ERP signals indicate the average
times at which the intention to
respond occurred in the two
groups. The topographical maps
beneath the graph show the
difference between the two
groups in pre-movement brain
activity.
Rigoni D et al. Psychological Science 2011;22:613-618
Copyright © by Association for Psychological Science
Les aires prémotrices
Set related neurons
Les neurones des aires prémotrices
Les neurones des aires prémotrices
Neurones bimodaux
Six examples of bimodal, visual-tactile neurons from PMv.
Graziano M S A et al. J Neurophysiol 1997;77:2268-2292
©1997 by American Physiological Society
Les neurones miroirs
Response properties of a mirror neuron.
(top row, right panel) Response of a neuron during active goal-directed motor acts of the monkey (e.g., grasping small objects of different shapes).
(bottom row, right panel) Response of the same neuron during the observation of the same goal-directed motor acts performed by the
experimenter.
In the two raster plots, each vertical bar signifies the occurrence of an action potential, and different lines refer to different trials. In both figures, time
t = 0 represents the moment of contact between the monkey’s (top panel) or experimenter’s (bottom panel) hand with the goal object.
Les neurones miroirs
Mirror neurons encoding the intention of the
actor.
The first two rows show the motor responses of a
neuron when the monkey grasped a piece of food to
eat it (first row) or to place it into a container (second
row). The third and fourth rows show the discharges
of the same neuron when the monkey was observing
the experimenter grasping a piece of food to bring it
to the mouth (third row) or to place it into a container
(fourth row).
During both action execution and observation, the
unit discharged selectively only when the piece of
food was grasped to eat it. It did not respond when
the same object was grasped to place it into a
container.
Les neurones miroirs
Exemplification of the proposed mechanism for the initial emergence of mirror neurons. At the beginning of
development, there is in the infant (human or monkey) no clear mapping between the observed motor act and its internal
motor representation (left panel). During development, the repeated synchronous coactivation of motor and visual
representations during observation of own movements leads to the emergence of neurons that exhibit a visuomotor
coupling between a specific action and its visual representation from an egocentric point of view (middle panel). These
visual representations are then generalized to the actions of others, which can be seen under a multiplicity of points of view
(right panel).
Les neurones miroirs
Schematic view of brain regions,
coding properties, and functional roles
of mirror neurons in the brain of
humans, monkeys. Cortical regions in
red identify the crucial nodes of the MN
system in the human and monkey
cerebral cortex. The regions in yellow
constitute the parietal node of the MN
system in the human and monkey brains.
43 VLPF, ventrolateral prefrontal cortex;
IFG, inferior frontal gyrus; PMv, ventral
premotor cortex; SMA, supplementary
motor area; IPL, inferior parietal lobule;
Cs, central sulcus; Ls, lateral sulcus; IPs,
intraparietal sulcus; rIPL, rostral inferior
parietal lobule. F5 and HVC are letterbased names.
Les neurones canoniques
« grasping neurons »
Cortex associatif
Hémi-négligence spatiale
Les projections descendantes
Les ganglions de la base
N. Caudé
Striatum
Putamen
GGB
P. Externe
Pallidum
P. Interne
Boucle cortico-striato-thalamo-corticale
La substance noire
Voie directe / voie indirecte
+
-
-
+
+
+
-
Parkinson
+
+
-
-
+
-
+
-
-
Cervelet
Apprentissage moteur
• Le système sensorimoteur contient une hiérarchie de programmes
sensorimoteur centraux. Les différents niveaux (sauf les plus hauts)
contiennent des ensembles d’activités programmées. Un mouvement
complexe résulte de combinaisons appropriées de ces programmes
• Notion d’équivalence motrice
• Contrôle visuel du comportement ≠ perception visuelle conscience
• Apprentissage : processus de regroupement & déplacement vers les
niveaux inférieurs
Perception consciente ≠ contrôle sensoriel
du comportement
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Pour en savoir plus :
http://neuroscience.uth.tmc.edu/s3/index.htm