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Chapitre III : mouvements oculaires - Coggle Diagram
Chapitre III : mouvements oculaires
Why do psychologists care ?
Du Laurens, 1596
The eyes are the "windows of the mind"
Eye-movements inform us of the functioning of the brain and the mind
Carpenter Roger, 1994
The oculomotor system provides researchers with "a microcosm of the brain"
Control of input
Precise output
Precise information about processes at play
Qu'est-ce qu'on peut apprendre ?
Les saccades <= variété de procssus cognitifs (Hutton, 2008)
Attention
Working memory
Learning
Long term memory
Decision making
Exemples
Lecture
Espaces de 8 caractères
Refixations présentes (jump backward)
Vitesse, efficacité de lecture <= endroit où les yeux se posent la 1ere fois
Location optimale : 3e - 5e lettre (O'Regan, 1984)
Gaze-contingent paradigms
Moving window ou fenêtre mouvante
Moving mask ou masque mouvant
"Perceptual span" +- 7 caractères, asymétrie (G << D)
Daily life activity
Préparer un thé : Land, 1999
Etapes précises dans un ordre précis
Les fixations qui précèdent une manipulation d'objet = +- 560ms
Move on to next object +- 610ms before manipulation 100%
Un tiers des fixations sur objets ont une des 4 fonctions de monitoring
Diriger (main ou objet) vers une autre location
Guider l'approche d'un objet vers un autre
Location des objets pour utilisation ultérieure
Checker l'état de l'objet (Ex : niveau d'eau dans un verre)
Study consciousness and visual processing of preverbal (infants) or non-verbal organisms (monkeys) ++
Eye-movement patterns can be the signature of certain conditions
Autism people have a different eye-movement pattern for faces
Recherche sérielle (lente et séquentielle)
Alfred Yarbus, 1967
Saccades and fixations are not arbitrary
Peinture "They did not expect him", Ilya Repin
La trajectoire de balayage <= tâche
Top-down influence
Vue libre ; estimer l'âge des personnes ; l'activité avant la peinture ; ...
Trajectoire très =/ en fonction de ce qu'on demande d'analyser
Castelhano et al.
Memorization task and visual search task
Why do we move the eyes ?
Chercher dans le détail
Collection d'informations
Structure de l'oeil et de la rétine DEFI PAPIER
Voir schéma
Cônes :détails plus précis, couleurs
Bâtonnets : vision plus globale
Acuité = abilité de distinguer les formes et détails des objets
Résolution spatiale = la plus petite distance à laquelle deux objets séparés peuvent être distingués
Faire le test de l'étoile dans le ciel
Magnification corticale
Reduction of the number of neurons processing a visual stimulus of a given size as a function of its peripheral position in the visual field
Anstis, 1974 : illustration lettres de + en + grandes
The homogeneity of the visual field is an illusion
If we had the same high resolution as in the fovea in the whole field, our "brain would be some hundreds of thousands toimes larger than our current brain and so would weight perhaps ten tons"
"A mobile eye constructed on the principles of the vertebrate eye is not a co-incidence or a luxury but is very probably the only way in xhoch a visual system can combine high resolution with the ability to monitor the whole vidual field"
How do we move the eyes ?
Muscles de l'oeil
Primary position = eye is central in the socket
Tertiary position = all other oblique directions
Secondary position = single horizontal or vertical rotation
Les muscles bougent les yeux mais servent aussi à les maintenir
SCHEMA PAPIER DIAPO 37/38
Brain and spatial attention
The spotlight analogy for spatial attention taps into the very functioning of the eye (F. & G., 2003)
3 components of a shift (covert) attention
Shift-movement (superior colliculus
Engagement (pulvinar in the thalamus)
Disengagement (parietal cortex)
=> Controlled by 3 distinct brain centres
Car difficultés =/ selon le dommage cérébral
Posner, Peterson, 1990
Système oculo-moteur
REFAIRE SCHEMA PAPIER
Links between covert and overt attention
Covert attention = DEFINITION PAPIER
Precedes overt attention ; provide cues as to what is interesting to orient to
Overt attention = DEFINITION PAPIER
needed to extract precise visual information, to identify objects
G. Rizzolatti, 1977
Pre-motor theory of attention
Strong links between covert <=> saccade trajectories
Moore & Fallah, 2001
Electric stimulation of a motor map (FEF)
Eyes move to the corresponding location
Subthreshold stimulation : eyes don't move
Target is detected more easily (lower change in luminance required) when presented in the MF (motor field)
Recherche visuelle
Recherche parallèle (chiffre rouge présent-absent ?)
Recherche sérielle (chiffre "4" présent-absent ?)
Examples of paradigms and mesures
DEFINITIONS DIAPO 2 PAPIER
Oculomotor capture paradigm
Do angry faces capture and/or guide the eyes >> neutral ?
Role of low-level features ?
1) Upright angry and neutral faces
2) Inverted angry and neutral faces
Stimuli display
One critical object (angry - neutral - butterfly) + 5 filler objects
Capture by emotional expressions ?
Irrelevant faces drive oculomotor behaviour
Advantage of selection for prototypical features - upright / neutral
Angry faces aren't selected more than neutral faces
Do they retain the eyes ? => "disengagement task" = they delay disengagement
Disengagement task
Upright faces VS inverted faces
Saccades beaucoup plus longues pour visages à l'envers
Petite /> pour les visages fâchés à l'endroit
Anti-saccade paradigm
Oculomotor control
Impaired in conditions implying dysfunction of the frontal lobe
Attentional biases towards socio-biologically relevant stimuli
Face recognition
Fixations sur les yeux, la bouche et le nez >>> reste du visage
Gaze-contingent paradigms
Events contingent to gaze position (visual display changes)
Reading
Visual search
Face recognition
Images : full view (face) + central mask + central window
Can simulate some conditions
Mascular degeneration (central mask)
View with retinitis pigmentosa (central window)
Saccade curvature
Types of eye-movements
Collection d'informations
Saccades = rotation of the eyes to bring a target into fovea
The 2 eyes turn in the same direction
Up to 3 ou 4 per second (> 150 000 a day)
30-40ms
A few degrees in size, larger during active tasks
Fast & stereotyped movements
Smooth pursuit : to maintain a moving target into fovea or a stationary target while we are moving
The two eyes turn in the same direction, relatively slow
Vergence : focus of the 2 eyes on a target moving in depth or 2 objects at =/ distances
The 2 eyes move in opposite (disjunction) or in the same direction (convergence)
Slower
Fixations : "stationary" periods between saccades
200-300ms
Drifts (dérives), tremors (tremblements) and micro-saccades prevent adaptation and unresponsiveness of the photoreceptors and galgion cells
Stabilised retinal image technique --> loss of vision
Fixational eye movements
Ces micro-mouvements sont ignorés dans la plupart des tâches cognitives
Saccadic eye movement
Ballistic movement : the eye is stationary, it accelerates, reaches a maximum velocity and decelerates rapidly
Ballistic movement of saccades cannot be change once initiated
Goal of a saccade <= at its onset
We can measure the angular rotation -> amplitude (distance travelled from A to B)
Amplitude <=> trajectoire ==> saccades stéréotypées
Velocity = rate of change of position with respect to time
Oblique saccades are not simple rotations, they show a systematic curvature (courbure)
Saccadic suppression
Visual thresholds are increased during saccades
Relative "loss" of vision
Contributes to the stable representation we have of the world
Masking machanism that prevents interference from the representation acquired during one fixation to the next
Saccadic suppression and latencies
The more saccades, the more suppression and the less fixations
Decision on what to look and wether it's worth it : cost-benefit analysis, even for the simpliest responses
In theory, saccade initiation +- 60ms (40 from retina to /> colliculus / 20 of stimulation of the SC to trigger the saccade)
In practice, a saccade responding to a sudden onset ("reflexive" takes +- 200ms
Saccades, pursuit and vergence
Pursuit movement <= target movement
Saccade driven by target position
Crosstalk between the 2 systems
Pursuit system can adapt to eyes lagging or leading the target
Saccade system can anticipate the position of the target
Reflex - stabilisation
VOR = vestibulo-ocular reflex
Reacts to inputs from the vestibular system
Compensates brief head movements (rotation or translation)
In >< direction to head rotations to maintain fixation on the object of interest
Latency < 15ms - one of the fastest
Ex : secouer la t^te en fixant sa main immobile
OKR = optokinetic reflex
Reacts to optic flow on the retina
Latency +- 100-130ms (Ex : only works when you move your hand slowly in front of your still face, the hand becomes blurry when it moves faster
Involuntary and automatic, nystagmus (DEFINITION ??)