Презентация на тему Attention - Dependent Representation of a Size Illusion in Human V1

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2. Working definitionsPonzo illusionSize constancy is phenomenal rescaling
3. Psychophysical task: Adjust the size of the
4. fMRI data collectionData about apparent sizesFixate spokes
5. fMRI image differences
6. Activation is shifted away from the center
7. fMRI differences correlate with perceptual difference (illusion magnitude) but only in the ‘attend-to-fixation’ task.
8. Additional low-resolution fMRI sessionActivation in LOC and
9. How does V1 rescale the size?Bonus material
11. PsychophysicsMonkeys (n = 2) were trained to
12. PredictionsThe edge (ring) of a far object
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Working definitionsPonzo illusionSize constancy is phenomenal rescaling of the retinal size of an object to match distance at which it is perceivedAttention is a set of mechanisms providing a selective access for a part of the

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Attention - Dependent Representation of a Size Illusion in Human V1

Presented at Cognitive Neuroscience Journal Club byIgor Utochkin (HSE)e-mail: isutochkin@inbox.ru

Working definitionsPonzo illusionSize constancy is phenomenal rescaling of the retinal size of

Psychophysical task: Adjust the size of the probe ring to match the

fMRI data collectionData about apparent sizesFixate spokes intersection of a still ring

Activation is shifted away from the center at the ‘back’ conditionThe change

fMRI differences correlate with perceptual difference (illusion magnitude) but only in the ‘attend-to-fixation’ task.

Additional low-resolution fMRI sessionActivation in LOC and PPA were found to be

How does V1 rescale the size?Bonus material

Attention - Dependent Representation of a Size Illusion in Human V1

PsychophysicsMonkeys (n = 2) were trained to fixate a larger ring (on

PredictionsThe edge (ring) of a far object should cause more activation in

Слайды презентации

Слайд 2 Working definitions
Ponzo illusion
Size constancy is phenomenal rescaling of

Working definitionsPonzo illusionSize constancy is phenomenal rescaling of the retinal size

the retinal size of an object to match distance

at which it is perceived
Attention is a set of mechanisms providing a selective access for a part of the input to deeper perceptual processing

Слайд 3 Psychophysical task: Adjust the size of the probe

Psychophysical task: Adjust the size of the probe ring to match

ring to match the size of either the front,

or the back ring

Слайд 4 fMRI data collection
Data about apparent sizes
Fixate spokes intersection

fMRI data collectionData about apparent sizesFixate spokes intersection of a still

of a still ring (baseline, 20 s) followed by

phase flicker (10 s)
Move to another ring

Attentional manipulation
Attention towards rings: Detect a 250-ms flicker pause on a fixated ring
Attention away from rings: Detect a small luminance change at a fixation point

Слайд 5 fMRI image differences

Слайд 6 Activation is shifted away from the center at

Activation is shifted away from the center at the ‘back’ conditionThe

the ‘back’ condition
The change in activation is substantially weaker
Attentional

effects

Слайд 7 fMRI differences correlate with perceptual difference (illusion magnitude)

but only in the ‘attend-to-fixation’ task.

Слайд 8 Additional low-resolution fMRI session
Activation in LOC and PPA

Additional low-resolution fMRI sessionActivation in LOC and PPA were found to

were found to be decreased under ‘attend-to-fixation’. This suggests

that V1 size rescaling is modulated by feedback from higher-level visual fields (presumably associated with representing the properties of objects and scenes)

Слайд 9 How does V1 rescale the size?
Bonus material

Слайд 10

Слайд 11 Psychophysics
Monkeys (n = 2) were trained to fixate

PsychophysicsMonkeys (n = 2) were trained to fixate a larger ring

a larger ring (on a gray background)
They were then

tested both with the gray and with a corridor background

Single-unit recordings
V1 cell responses were recorded
For each cell 7 ring sizes were tested eliciting firing rates around an optimum for their receptive fields (RF)

Optimum (“preferred” size)