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Global visual perception. Velitchko Manahilov Uma Shahani Gael Gordon William Simpson. Outline. Reverse correlation analysis Classification image approach Perceptive fields for global motion in individuals with: - normal vision - amblyopia - dyslexia - persistent migraine aura

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Global visual perception

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Global visual perception
Global visual perception

Velitchko Manahilov

Uma Shahani

Gael Gordon

William Simpson


Outline
Outline

  • Reverse correlation analysis

  • Classification image approach

  • Perceptive fields for global motion in individuals with:

    - normal vision

    - amblyopia

    - dyslexia

    - persistent migraine aura

  • Conclusions


Global visual perception

Reverse correlation technique

Visual neurons are stimulated by noise images

and the spike output is cross-correlated with the input.


Global visual perception

Reverse correlation technique

Multifocal ERG & VEP


Global visual perception

What is a classification image?

The classification image shows

how the observer weights the information

in the image to reach a decision.



Global visual perception

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<M>

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<H>

Criterion

Noise+Signal

response

Probability

MISS

HIT

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Internal response


Global visual perception

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<CR>

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<FA>

Criterion

Noise

response

Probability

Corr rej

False alarm

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Internal response


Classification image

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<M>

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<H>

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<CR>

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<FA>

CI = <H> - <M> + <FA> - <CR> =

Classification image



Global visual perception

H-MF-C

Beard & Ahumada, JOSA, 1999.



Global visual perception

Internal representation? Current Biology 2000.

Observers were presented with 20,000 noise samples. They were told that the letter “S” was present on 50% of the trials. No more detail was given regarding the shape of the letter.

No signal was ever presented.

The classification image resembles the letter “S”.

Gosselin F. & Schyns P. Psychological Science, 14, 504-509, 2003.


Global visual perception

Global motion direction Current Biology 2000.

Black discsdisc diameter - 20’speed - 5 deg/s4 frames of 50 msdisplay size - 10x10 deg


Perceptive field of ideal observer if s md i 0 right if s md i 0 left
Perceptive field of ideal observer Current Biology 2000.if SMDi> 0 => Right if SMDi< 0 => Left


Global motion direction normal observers subj dd
Global motion direction Current Biology 2000.normal observersSubj. DD


Global motion direction normal observers subj jpk
Global motion direction Current Biology 2000.normal observersSubj. JPK


Global motion direction normal observers subj imk
Global motion direction Current Biology 2000.normal observersSubj. IMK


Global motion direction normal observers subj ls
Global motion direction Current Biology 2000.normal observersSubj. LS


Global motion direction normal observers average
Global motion direction Current Biology 2000.normal observersAverage


Amblyopia
Amblyopia Current Biology 2000.

Amblyopia (lazy eye) is the loss or lack of development of central vision in one eye.

It is unrelated to any eye health problem and is not correctable with lenses.

It can result from a failure to use both eyes together.

Lazy eye is often associated with crossed-eyes or a large difference in the refractive errors between the two eyes.

It usually develops before the age of 6, and it does not affect side vision.


Global motion direction subj ch amblyopic eye fellow eye
Global motion direction Current Biology 2000.Subj. CHAmblyopiceye Fellow eye


Global motion direction subj kh amblyopic eye fellow eye
Global motion direction Current Biology 2000.Subj. KHAmblyopiceye Fellow eye


Global motion direction subj lw amblyopic eye fellow eye
Global motion direction Current Biology 2000.Subj. LWAmblyopiceye Fellow eye


Global motion direction average amblyopic eye fellow eye
Global motion direction Current Biology 2000.AverageAmblyopiceye Fellow eye


Global motion direction subj dd subj jpk va 6 18
Global motion direction Current Biology 2000. Subj. DD Subj. JPK VA 6/18


Global motion direction
Global motion direction Current Biology 2000.


Global motion direction1
Global motion direction Current Biology 2000.


Global motion direction2
Global motion direction Current Biology 2000.


Global motion direction3
Global motion direction Current Biology 2000.


Dyslexia
Dyslexia Current Biology 2000.

Developmental dyslexia is manifested as

a difficulty with reading given normal individual intelligence

that cannot be explained by other factors such as

sensory acuity, learning opportunities or brain injuries.


Global motion direction dyslexia
Global motion direction Current Biology 2000. Dyslexia


Global motion direction dyslexia1
Global motion direction Current Biology 2000. Dyslexia


Global motion direction dyslexia2

Average Current Biology 2000.

Global motion direction Dyslexia


Persistent migraine aura
Persistent Migraine Aura Current Biology 2000.

Persistent migraine aura is a rare but well documented complication of migraine.

Patients experience continuous aura lasting weeks or months.

These patients offer a unique opportunity to examine the migraineous brain during the aura phase of the attack.


Global motion direction persistent migraine aura
Global motion direction Current Biology 2000.Persistent Migraine Aura


Global motion direction persistent migraine aura1
Global motion direction Current Biology 2000.Persistent Migraine Aura


Global motion direction persistent migraine aura2

Average Current Biology 2000.

Global motion directionPersistent Migraine Aura


Global visual perception

SUMMARY Current Biology 2000.1. Classification image technique provides a new powerful tool for estimating the observers’ behavioural template for detecting objects.

2. Normal observers use localised perceptive fields when integrate global motion information. They extract motion information from central moving discs and suppress peripheral items.

3. The perceptive fields of individuals with amblyopia, dyslexia and persistent migraine aura are wider than the perceptive fields of normal observers.

4. The wider perceptive fields of these individuals may be related to reduced suppression of global (attentional) mechanisms which allows integrating motion information over a much larger field.

5. In the presence of environmental noise, these individuals may have deficits in exclusion of unwanted distractors.


Thank you
Thank you. Current Biology 2000.


Perceptual noise exclusion deficits in dyslexia
Perceptual noise-exclusion deficits Current Biology 2000.in dyslexia

Sperling et al., (2005). Nature Neuroscience, 8, 862-863.


Perceptual noise exclusion deficits in dyslexia1
Perceptual noise-exclusion deficits Current Biology 2000.in dyslexia


Global motion direction persistent migraine aura3
Global motion direction Current Biology 2000. Persistent Migraine Aura


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