8 - Object-Based Attention & Cogn. Neuropsychology of Attention Flashcards
What is Tipper’s (1985) Negative priming effect? (Super-imposed shapes)
- super-imposed coloured items to be overlapping with one another
- Pairs of red-green figures: trumpet-kite, anchor-trumpet etc.
- Ignore green name red (e.g., ignore trumpet name kite)
- What happens when trumpet must be named?
- RT to name trumpet is slower if ignored on the previous trial
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“Negative priming” (regular priming produces speed up).
- Means ignored shape must have been perceived to produce effect on subsequent trial (cf. late selection)
How did Duncan (1984) stimuli differing on four attributes task offer evidence for object-based attention?
- Stimuli differing on four attributes: box size, gap side, line slant, dotted or dashed line
- Flash briefly, ask to report two of the attributes (e.g., line slant, gap side).
Results:
- More accurate if the two attributes belonged to the same object than different objects.
- Same: box size and gap side or line slant and line style (dotted/dashed)
- Different: box size and line slant, etc.
Evidence of object-focused selective attention… selecting for the object has benefits (accuracy)
How does Cuing Object-Based Attention tasks (Egly, Driver, & Rafal, 1994) provide evidence for object-based attention, over space-based attention? (hint: Same object advantage)
- Cuing task in which miscued locations could in same object - e.g. at the top & target presents at bottom.
- Or in a different object.
- Importantly, it is always the same distance from each cued location to target.
- Space-based theories says miscuing costs should be the same - i.e. switching costs.
Results
- Same object advantage: Mean RTs faster to miscued stimuli if in same object.
Evidence that cuing effect spreads to encompass cued objects.
How did Moore, Yantis, & Vaughan (1998) manipulate the original cuing object-based task with an Occluding Bar?
- Occluding bar in stereo space: still find same object advantage
- Not related to crossing edges or boundaries; agrees with the percept of continuous objects.
Attention is selecting the ‘perceptual object’ crossing perhaps arbitrary boundaries.
What is the neuroimaging evidence for object-based attention? (fMRI house/faces).
- Selective fMRI activation when viewing houses and faces.
- Fusiform face area –active when viewing faces
- Parahippocampal place area –active when viewing houses
- Superimpose: attend to face or house
- Face: FFA up, PPA down
- House PPA up, FFA down
- BOLD signal change greater for each area, relative to the other.
What constitutes visual neglect?
- Failure to focus and failure to disengage and reorient both found in clinical cases.
- Damage to the right parietal lobe.
What are the two pathways for processing visual information? Which pathway is disrupted by parietal lobe damage?
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Ventral (belly) pathway, temporal lobe: form, colour – what pathway.
- ty-wot-time-what = ventral
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Dorsal (top) pathway, parietal lobe: the direction of motion, spatial location – the where pathway -
- periscope-parietal-where = dorsal.
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Parietal lobe damage disrupts “where” pathway.
- damage to right lobe impairs left field.
How did Posner show that difficulties in disengaging and shifting attention underly Cuing Deficits with Right Parietal Damage ppl?
- Compared intact and damaged hemispheres, use intact hemisphere as a control.
- normal attention involves engagement, disengagement, and shift (reorienting) of attention
- So damange & control pts show similar performance on valid trials - where no disengaging & shift is requried.
- But differences on invalid trial - where disengagement & shift is required.
Conclusion: Ability to voluntarily engage attention not impaired; difficulties in disengaging and shifting in response to new information impaired.
Attention phenomenon!
How is extinction, a symptom of neglect, proposed to work? (hint: left visual field deficit with two simultaneous stimuli presented). Why does extincntion occur?
- Presentation of only one stimulus is unimpaired for pts w/ neglect.
- Presence of two stimuli - attention on one seems to suppress or extinguish the other.
- Sounds like late-selection theory:
- Only one signal can get through filter to consciousness at a time.
- Extinction: Two competing perceptual representations can’t co-exist
Reason for extinction:
- recognition & identification require activation of neural structure, which if damaged will be chronically underactive in one h/sphere. -
- Stimuli don’t provide activation they should.
- Effects strongest with activity in other hemisphere (invalid cue, competing stimulus)
What is Balint’s Syndrome (patient RM)?
- Bilateral lesions in parietal and/or occipital cortex.
- Inability to focus on individual objects and to see more than one object at a time (Simultanagnosia)–prone to illusory conjunctions (Blue T - see image)
- Occurs even when objects overlap (Object based!)
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Reminder: how does inhibition of return (IOR) benefits but also impair target location? And what is Object-Based Inhibition of Return (Tipper, 1991)?
Hint: benefit-cost depends on SOA presentation timing.
- IOR: peripheral cue & target at same location after long SOA = slower RT = cost.
- space has been tagged as “searched” no need to search again
- Object-based IOR = peripheral cue of the objects then rotate objects in the display (in view) > new position & long SOA = slower RT at previously cued marker
- IOR tracks cued marker to new locatio.
- IOR follows the cued object, not confined to one region of space
How did Behrmann & Tipper ( 1994) show that neglect has a strong Object-Based component? hint: Barbell-stimulus / rotation cuing task.
Design:
- Neglect: left visual field deficit with right parietal damage.
- Barbell stimulus: two location markers + connector, combine into one perceptual object.
- Longer detection RT on left
- THEN ROTATED BARBELL: Longer RTs on right
Takeaway:
- Neglect tracks marker to the opposite visual field!
- Neglect of left side of objects, not just left side of space
- Allows space-based and object-based effects to be distinguished
