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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
ParietalLobe
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
valid - contralesional target
valid - ipsilesional target
invalid - contralesional target
invalid - ipsilesional target
A PREDICTION:
Disorders of Orienting
Results: Valid cue in contralesional field is effective
invalid- contralesional target
valid - contralesional target
invalid - ispilesional target
valid - ipsilesional target
Results: Severe difficulty with invalidly cued contralesional target
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
