Neural mechanisms of feature-based attention

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Neural mechanisms of feature-based attention

• Taosheng Liu

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What is attention?
Everyone knows what attention is. It is the
taking possession by the mind in clear and vivid
form, of one out of what seem several
simultaneously possible objects or trains of
thought. -William James (1890)?

• Types of visual attention
• Overt attention
• Covert attention
• Spatial
• Feature-based
• Object-based

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Attention and the brain

• Effects vs. control

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Outline

• The effect of feature-based attention on visual
  cortex
• How does attention modulate sensory
  representations?
• The control of feature-based attention
• What is the source of control and how is control
  implemented?
• Attention and object recognition

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The effect of FB attention to motion
Treue Martinez-Trujillo, 1999, Nature

• Questions
• Does feature-based attention modulate neuronal
  subpopulations in the attended location?
• If so, how does it correlate with behavior?

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Use adaptation to assess feature selectivity
More adaptation for a upward test stimulus when
attending up vs. down
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fMRI adaptation

• A voxel contains many neurons.
• fMRI adaptation can assess feature selectivity
  within a voxel.

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Adapting stimulus
play demo
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Behavior tilt aftereffect (n8)?
Attend -20
Attend -20
Attend 20
Attend 20
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fMRI adaptation protocol
Task inside the scanner report the orientation
of the test stimulus.
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fMRI details

• Siemens 3T Allegra
• Surface coil
• 21 coronal/oblique slices
• 3 mm isotropic voxels
• TE 30 ms, FA 75º
• TR 1.2 s
• Bite bar to minimize head motion

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Surface reconstruction and retinotopic mapping
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Retinotopic mapping and localizer
real data (TL)?
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fMRI response to the test stimulus
adapter
test
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Attention modulation index
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Correlation between behavioral and imaging results
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A model relating psychophysical and imaging data
Psychophysics
Neural response
fMRI
Neural response
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Summary conclusion

• Feature-based attention enhances activity of
  neuronal subpopulations when the attended and
  unattended features are processed in the same
  retinotopic region.
• Attentional modulation of orientation-selective
  fMRI response adaptation.
• Attentional modulation constant across visual
  areas, suggesting a feed-forward mechanism.
• Significant correlation between TAE and AMI only
  in V1.

Liu etal, 2007, Neuron
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The control of feature-based attention

• Components of attentional control
• Disengage/shift
• Engage/maintain
• Goal
• Separate different components
• Feature-based attention

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Task and design
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Sustained effect for motion
FEF, SPL/IPL sustained attentional control for
motion.
MT effects of attention for motion.
color to motion
motion to color
hold motion
hold color
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Transient shift activity
Precu, IPS, PCG transient control of attention
shift.
color to motion motion to color hold
motion hold color
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Summary

• Effects of attention
• MT (motion) and V4 (color)?
• Attentional control
• Transient control disengage/shift (superior
  parietal lobule, left intra-parietal sulcus, left
  pre-central gyrus).
• Sustained control engage/maintain (frontal eye
  fields, superior-inferior parietal lobule for
  motion superior frontal gyrus for color).

Liu etal, 2003, Cerebral Cortex
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Current and future plans

• Attentional control within feature dimensions
• What are the shift regions?
• What are the hold regions?--attentional priority

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The representation of attentional priority

• Spatial attention
• Higher areas with a spatiotopic map send feedback
  signals
• Feature-based attention
• Are there neurons that encode the attended
  direction in higher areas?

FEF
LIP
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Decoding of brain activity Kamitani Tong
(2007)?

• Classifier scheme
• Classifier can reliably decode orientation
  information in early visual cortex

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Learning sequence of views of three-dimensional
objects

• The effect of temporal coherence on object memory

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How do we recognize shapes?
Temporal association object views appearing
close in time are associated. Wallis
Bulthoff (1999)?
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Harman Humphrey (1999)?
No accuracy effects
Attention? Effort? ???
7 views x 1 s/view x 3 repeats
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Exp 1 - replication
stimuli
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Exp 1 - method
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Exp 1 - results
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Exp 2 test novel views
Test views 1,3,5,7
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Exp 3 method
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Exp 3 - results
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Exp 4
Encoding task preference rating rate how much
you like each sequence on a 3-point scale
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Exp 4 - results
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Summary

• RR always the worst
• temporal association works
• SS never exceeds SR
• temporal vs. spatiotemporal coherence
• SS depends on study time and intention
• potential confound