Transcript 2320Lecture26.ppt

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Feature Integration Theory
• What term does Treisman use to describe
the bundle of features at a specific location?
Feature Integration Theory
• Object Files are mental (neural?)
representations of the features associated
with an object
– whenever an object is selected by attention its
features are bound and an object file is opened
– when the features of that object change, the
object file is updated
Feature Integration Theory
• How did Treisman et al. test whether the
visual system uses object files?
Feature Integration Theory
• Priming: observers are faster to respond to
something they’ve just seen
Feature Integration Theory
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Feature Integration Theory
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Feature Integration Theory
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Feature Integration Theory
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Feature Integration Theory
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Feature Integration Theory
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Feature Integration Theory
What Letter?
Feature Integration Theory
• What was the result?
Feature Integration Theory
• What was the result?
– Naming was faster if the prime occurred in the
same object, even though the object had moved
Feature Integration Theory
• What was the result?
– Naming was faster if the prime occurred in the
same object, even though the object had moved
• Interpretation?
Feature Integration Theory
• What was the result?
– Naming was faster if the prime occurred in the
same object, even though the object had moved
• Interpretation?
– visual system establishes object files and
updates them as the location and features of the
object change
The Physiology of Attention
Physiology of Attention
• Neural systems involved in orienting
• Neural correlates of selection
Disorders of Orienting
• Lesions to parietal cortex can produce some
strange behavioural consequences
Parietal
Lobe
Disorders of Orienting
• Lesions to parietal cortex can produce some
strange behavioural consequences
– patients fail to notice events on the
contralesional side
– Patients behave as if they are blind in the
contralesional hemifield
Disorders of Orienting
• Lesions to parietal cortex can produce some
strange behavioural consequences
– patients fail to notice events on the
contralesional side
– Patients behave as if they are blind in the
contralesional hemifield but they are not blind
• Called Hemispatial Neglect
Disorders of Orienting
• Patients will often
“neglect” half of
their visual field
Disorders of Orienting
• Hypothesis: Parietal cortex somehow
involved in orienting attention into
contralesional space
Disorders of Orienting
• Posner and colleagues
– Use cue-target paradigm to investigate
attentional abilities of parietal lesion patients
Disorders of Orienting
• Posner and colleagues
– Use cue-target paradigm to investigate
attentional abilities of parietal lesion patients
– Prediction ?
Disorders of Orienting
• Posner and colleagues
– Use cue-target paradigm to investigate
attentional abilities of parietal lesion patients
– Prediction: stimuli in ipsilesional field always
faster than stimuli in contralesional field and
cues don’t matter
Disorders of Orienting
A PREDICTION:
invalid - contralesional target
valid - contralesional target
invalid - ipsilesional target
valid - ipsilesional target
Disorders of Orienting
invalid- contralesional target
Results: Severe difficulty with
invalidly cued contralesional
target
invalid - ispilesional target
valid - contralesional target
valid - ipsilesional target
Results: Valid cue in
contralesional field is effective
Disorders of Orienting
• Interpretation:
– Patients have difficulty disengaging attention
from good hemifield so that it can be shifted to
contralesional hemifield
Disorders of Orienting
• Interpretation:
– Patients have difficulty disengaging attention
from good hemifield so that it can be shifted to
contralesional hemifield
– Parietal cortex is somehow involved in
disengaging attention
Disorders of Orienting
• Disengage - Shift - Engage Model
– Parietal Cortex notices events and disengages
attention
Disorders of Orienting
• Disengage - Shift - Engage Model
– Parietal Cortex notices events and disengages
attention
– Superior Colliculus moves attention
Disorders of Orienting
• Disengage - Shift - Engage Model
– Parietal Cortex notices events and disengages
attention
– Superior Colliculus moves attention
– Pulvinar Nucleus reengages attention
Disorders of Orienting
• Disengage - Shift - Engage Model
– Parietal Cortex notices events and disengages
attention
– Superior Colliculus moves attention
– Pulvinar Nucleus reengages attention
– Entire process is under some top-down control
from Frontal Cortex
Disorders of Orienting
• Orienting mechanism can be interfered with in
normal brains
Disorders of Orienting
• Orienting mechanism can be interfered with in
normal brains
– changes that are not accompanied by transients are hard
to detect
Disorders of Orienting
• Orienting mechanism can be interfered with in
normal brains
– changes that are not accompanied by transients are hard
to detect
• e.g. building appearing slowly
• orienting mechanism scans the scene aimlessly
Disorders of Orienting
• Orienting mechanism can be interfered with in
normal brains
– changes that are not accompanied by transients are hard
to detect
• e.g. building appearing slowly
• orienting mechanism scans the scene aimlessly
– changes accompanied by full-field transients are hard to
detect
• e.g. change blindness
• orienting mechanism is blinded by the transient
Next Time:
• Neural correlates of selective attention