Cognitive Neuroscience

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Cognitive Neuroscience
2011-03-31 00:23:21
Attention II

Exam #2
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  1. exogenous stimulus
    • blinking flash replaces the arrow
    • this shows the impact of attention at a cell's selected orientation (the attention increases the amplitude of the cell's response)
  2. increase baseline firing of cells by
    paying attention to the receptive field
  3. when attention is paid to the receptive field this causes
    • an increase in baseline firing which helps modulate the cell's response
    • as if that cell is getting ready
  4. Evoked Activity =
    • Phasic
    • 1. stimulus must be preferred by the cell
    • 2. must be time-locked to target
    • 3. will be greater when target is attended
  5. Sustained Activity=
    • Tonic
    • 1. Location must be preferred by the cell
    • 2. Time lock to cue
    • 3. Greater when attention is focussed within cells receptive field
  6. Early Selection
    Irrelevant inputs are gated at an early stage of visual processing, so that only hte to-be attended to elements are analyzed
  7. Late Selection
    Both attended and ignored elements are processed to a similar semantic level of analysis, selection for concious awareness therefore takes place at a late stage in processing
  8. Why is selection necessary?
    • We have limited ability to interact and respond to external stimuli
    • not able to process all stimuli
    • attentional systems allow us to select which information is processed
    • but early or late?
  9. Broadbent's Model is called
    Information Processing Bottleneck
  10. 4 stages of Broadbent's Info Processing Bottleneck
    • 1. Sensory Input
    • 2. Perceptual Analysis
    • 3. Semantic Analysis
    • 4. response Selection and Execution
  11. Filtering out of irrelevent info in support of early selection
    • 1. Dichotic Listening Studies
    • -unable to remember info presented to the irrelevant ear
    • 2. Posner cuing Paradigm
    • -slower to respond to the invalid cue (not attending to target area)
  12. Filtering out of irrelevant information support of late selection
    • 1. Dichotic Listening studies
    • -semantic train of thought followed from relevant to irrelevant ear
    • 2. Breakthrough Phenomenon and Cocktail Party Effect
  13. Limitation of Cognitive PsychologyApproach (box model)
    is information really irrelevant if we need to respond to it??
  14. Cog-Neuro Studies of Early-Late Selection Debate
    assess the fate of the unattended stimuli by measing neural responses to them (this does not require judgement from the subject)
  15. ERP Studies of Attention
    • Attend left or attend right- press the button when simuli are the same and are on the instructed attended side
    • Put an electrode in right hemisphere to index activity in the left visual field
    • Neural activity is greater when attention is directed to the left hemifield (see larger amplitude in P1 component), than when attention is directed towardsd the right hemifield)
    • This would be opposite if put electrode on left hemisphere- activity woudl be greater for right visual field than
  16. Summary of the P1 Component
    • 1. Generated in V4
    • 2. is a sensory-perceptual component
    • 3. amplitude will be greater for brighter stimuli (regardless of attention conditions)
    • 4. is the first visually-evoked ERP component that is modulated by attention
    • 5. amplitude is greater when attention is directed to the contralateral versus the ipsilateral hemifield
  17. Summary of the N170 Component
    • 1. is a face-sensitive component
    • 2. amplitude is grater for high versus low saliency faces
    • 3. amplitude is greater when attention is directed to face versus nonface stimuli (but effect is limited during conditions where face saliency is slow)
  18. N170 Attention Effect
    • for a high face saliency, no difference in N170 amplitude when attend to face vs attend to house
    • for a low face saliency, amplitude is greater for attend to face vs attend to house
  19. Neural response changes based on __ and not ___
    • amplitude (bigger or smaller spike)
    • NOT speed (not faster or slower)
  20. Support for Early Selection:
    • 1. Attention influences the sensory-perceptual processing of info
    • -attention to elicits bigger response
    • -attention away elicits smaller response
    • 2. Attention's effect is seen EARLY IN TIME in the visual processing stream, IN EARLY VISUAL AREAS
  21. Feature tuning
    • All visual areas code for SPATIAL LOCATION AND orientation or color or motion or shape or face
    • so attention to space may have a special status
  22. areas that code for orientation, color, motion, shape face
    • V2
    • V4
    • MT
    • IT
    • FFA
  23. FFA
    Fusiform face area
  24. The "spotlight metaphor"
    • Spatial attn is like a spotlight
    • 1. Indivisible
    • 2. moves spatially from one region to the next
    • 3. enhances regions within the spotlight
    • 4. size of the region may vary but capacity is limited
    • 5. independent of eye movements
  25. Components of Attentional Orienting
    • Disengage (from fixation or invalidly cued location)
    • Move (attention to relevant loc)
    • Engage (selective processing at location indicated by cue)
  26. Ned Neuropsych case
    • 1. pays attn to half of his body
    • 2. suffers from alien hand syndrome
    • 3. only eats off half of his plate
    • 4. ignores people sitting to his left
    • 5. when he hears a crash to his left he turns his head
  27. Is Ned's Problem:
    • sensory? no, can see fine in left visual field
    • Motor? no, can move his left side
    • Attentional- yes
  28. Neglect
    A failure to report, respond, or orient to novel or meaningul contralesional stimuli
  29. Most cases of neglect involve
    lesions to the right parietal lobe (more common with right vs. left hemisphere damage)
  30. Hemispatial Neglect
    failure to respond to objects or events presented in the contralesional hemifield
  31. Hemispatial Neglect usually occurs due to
    lesions in parietal cortex or frontal cortex (as wellas basal ganglia and thalamus)
  32. Other neglect terminology:
    • hemispatial neglect
    • hemineglect
    • hemi-inattention
    • hemisensory neglect
    • unilateral neglect
    • parietal neglect
  33. Hemispatial Neglect hypothesis
    • There is assymmetry in attentional orienting system
    • such that info from the left visual field is only attended to by the right hemisphere, where info from the right visual field is attended to by both the L and R visual fields
    • therefore- lesions on the left hemisphere will not cause hemineglect bc info is also being attended by the right visual field
    • but lesions on the right hemisphere will cause hemineglect bc info from LV is only being attended at right hemisphere
  34. Anton Raederscheidt
    his self portraits after stroke recovery didn't immediately incorporate the right side of his body
  35. Single unit studies of attention
    show that in both the valid and invalid conditions, the orientation of the bar modulated the the response of the cells activity