Transcript Chapter 21: Attention - Biology Courses Server

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Neuroscience: Exploring the
Brain, 3e
Chapter 21: Attention
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Introduction
• Attention:
• State of selectively processing simultaneous sources of
information
• Benefits performance of behavioral tasks
• Importance emphasized by attention-deficit hyperactivity
disorder
• Brain Imaging – changes in cortical activity
• Study attention by examining behavioral manifestations,
e.g., visual attention
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Behavioral Consequences
of Attention
• Attention enhances visual
detection
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Behavioral Consequences of Attention
• Attention Decreases Reaction Times
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Physiological Effects of Attention
• Shifting Attention
– What happens to neural activity?
– What brain areas are involved?
• Observed in high-level cognitive and numerous
sensory areas
• e.g., Area V1 to visual cortical areas in the
parietal and temporal lobes
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Physiological Effects of Attention
• Functional MRI Imaging of
Attention to Location
– Subjects view stimulus
– Change location of
attended sector
– Brain activity shifts
retinotopically
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Physiological Effects of Attention
• PET Imaging Attention to Features
– Same-different discrimination task:
Color, shape, speed
– (A) Selective attention: one feature
– (B) Divided attention: all features
– Subtract B from A shows brain
activity associated with attention to
one feature V4, IT and other visual
areas in temporal lobe Color &
shape
– Area MT Speed of motion
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Physiological Effects of Attention
• PET Imaging of Attention to Features (Cont’d)
Color
Shape
Motion
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Physiological Effects of Attention
• Enhanced Neuronal Responses in Parietal Cortex
– Attention: Experimental vs. Normal conditions
– What happens to attention under normal conditions?
– Assumption: Attention changes location prior to eye
movement
– Wurtz, Goldberg, and Robinson
• Record neural activity from several brain regions
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Physiological Effects of
Attention
• Enhanced Neuronal Responses in
Parietal Cortex
–
Wurtz, Goldberg, and
Robinson
• Implications of Superior
Colliculus work for explaining
these findings
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Physiological Effects of Attention
• Enhanced Neuronal Responses in Parietal Cortex (Cont’d)
– Posterior parietal cortex neurons
– Directing eye movements
– Response significantly enhanced neuronal response
when eyes went to target
• Spatially selective effect – not a general increase
in excitability
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Physiological Effects of Attention
• Receptive Field Changes in Area V4
(Response to effective stim.
But attention directed at
location of ineffective stim.)
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How is Attention Directed?
• Cortical, subcortical areas
– Modulate the activity of neurons in sensory cortex
areas
• The Pulvinar Nucleus
– Guiding attention
– Muscimol
• GABA agonist
• Neuron activity
suppressed
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How is Attention Directed?
• Attention and Eye Movements
– Eye moves to attended object
– Eye movements & attention closely related
– Recent experiments
• Brain circuitry: Directing eyes to objects of
interest
– Frontal Eye Fields (FEF)
• Cortical area
• FEF neurons
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How is Attention Directed?
• Attention and Eye Movements (Cont’d)
– Experiment
• Train monkeys to look at display of small light spots
• Place electrode in FEF and determine motor field of
neurons at the tip
• Small electrical stimulation enhancement?
– Results
• FEF involved in directing attention; Enhancing visual
performance
• V4 activity increased
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How is Attention Directed?
• Attention and Eye Movements
– Results (Cont’d)
• FEF stimulation mimics physiological and
behavioral effects of attention
• Electrical stimulation of superior colliculus
– Conclusion
• Guidance of attention
• Integrated with system to move eyes
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Physiological Effects
of Attention
Copyright © 2007 Wolters Kluwer Health | Lippincott Williams & Wilkins
Concluding Remarks
• Studies of attention point to flexibility of the human brain
• More mental energy to one location
– Enhanced sensitivity & reaction time
– Ignore competing stimuli
– Can be seen in brain imaging studies
– Effects receptive field properties
• Why do we need attention?
– Cannot process all information simultaneously
– Selects what information should access the limited
processing resources
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End of Presentation
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Behavioral Consequences of Attention
• Neglect Syndrome as an Attentional
Disorder
–
Person ignores objects, people,
and their own body to one side of
the center of the gaze
–
Associated with right-sided lesions
–
Hypothesis: Left hemisphere
attends to right hemifield whereas
right hemisphere attends to both
right and left hemifields
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