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)