Visual Perception, Attention & Action
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Attention1) Visual Spotlight
X ♥
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Attention2) Visual Short Term Memory
For items not presently in the perceptual stream
Capacity depends upon familiarity and item complexity
• Delayed match to sample• N-back task• Interaction of Dorsolateral Frontal System and
Posterior Parietal System
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Attention2) Visual Short Term Memory
For items not presently in the perceptual stream
Capacity depends upon familiarity and item complexity
• Delayed match to sample• N-back task• Interaction of Dorsolateral Frontal System and
Posterior Parietal System
5 3 9 533
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Attention2) Visual Short Term Memory
For items not presently in the perceptual stream
Capacity depends upon familiarity and item complexity
• Delayed match to sample• N-back task• Interaction of Dorsolateral Frontal System and
Posterior Parietal System
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Attention
3) Hemi-field Neglect as an Atttention Disorder
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Eye Movements
1) Smooth Pursuit Eye Movement
2) Vergence Eye Movements
3) Saccades
4) Microsaccades
5) Vestibular Eye Movements
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1) Smooth Pursuit Eye Movement
Volitional eye movements for tracking laterally moving objects
• Dynamic visual acuity is less than static acuity because of image slip.
• DUI
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2) Vergence Eye Movements
Volitional eye movements for tracking approaching or receding objects
• Conjugate vs. Discongugate
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3) Saccades
Volitional eye movements for gaze shift
• Change point of fixation
• Up to 6/sec.
• Role of motor efferents in perceptual stability
• Saccadic suppression
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4) Microsaccades
Nonvolitional eye movements
• Prevent receptor fatigue
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5) Vestibular Eye Movements
Nonvolitional eye movements to compensate for head motion
• The semicircular canals of the inner ear detect head position and motion
• What if vestibular information does not match visual information?
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Balance & Posture
• Interaction of visual, proprioceptive and vestibular systems
• Depends heavily on vision
• Afferents from perceptual systems are processed very quickly to produce the correct efferents to the musculature
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Dynamic Balance
• Running in the dark
• Postural Sway
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Visual Control of Locomotion• Simple Updating
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Visual Control of Locomotion
• Complex Brains Allow Complex Strategies
• Motor learning allows strategies to become adaptive
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Action Observation & Imitation• Neurons of macaques respond to visual
recognition of hand actions performed by others.
• Response of these cells is dependent upon the interrelation of hand and object movements.
• Lack of response when the object is grasped with a tool.
Motor properties of a typical F5 motor neuron:
• is active specifically during a particular grasping
• action phase (opening, closing, holding)
Area F5 may be considered a storage of motor plans (“vocabulary”)
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• An F5 “mirror” neuron fires during initial observation and then similarly during action
• However, it only fires during initial observation if the task is to be copied
Monkey grasps
Monkey looks
Monkey See, Monkey Do
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F5 Neuron While Monkey Observes Grasping
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Same Motor Neuron During Grasping
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• Experimental situation:• Observation of mouth grasping vs
observation of static mouth • Observation of hand grasping vs
observation of static hand• Observation of foot pressing vs
observation of static foot
The human mirror system: fMRI
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The human mirror system: fMRI
OBSERVATION OF:
MOUTH MOVEMENTS HAND MOVEMENTSFOOT MOVEMENTS
Buccino et al. 2001, Europ. J. Neurosci.
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MELTZOFF
Imitation based on the neonate's capacity to represent visually and proprioceptively perceived information in a form common to both modalities. Observations in six newborns- one only 60 minutes old - suggest that the ability to use intermodal equivalences is innate (Meltzoff and Moore 1977)
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Imitation• Normal development
– Neonates can imitate a range of facial expression (Meltzoff & Moore, 1970).
• Tongue protrusion• Lip protrusion• Mouth opening
– Toddlers imitate movements that they believe to have been performed intentionally by the model (Meltzoff, 1995).
• Imitation deficits in autism• Impairment in spontaneous imitation of action on novel objects.• Impairment in instructed imitation
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ImitationEvidence of imitation in birds.
• Pigeon and Quail• Imitate the appendage (beak or feet) used to depress
a lever.
• Carib grackles• Imitate features of beak (closed pecking versus open
prying).
• Imitate features of head (down vs up)
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