Post on 07-Jan-2016
description
Global visual perceptionGlobal visual perception
Velitchko ManahilovVelitchko Manahilov
Uma ShahaniUma Shahani
Gael GordonGael Gordon
William SimpsonWilliam Simpson
Outline
Reverse correlation analysis Classification image approach Perceptive fields for global motion in individuals with:
- normal vision
- amblyopia
- dyslexia
- persistent migraine aura Conclusions
Reverse correlation technique
Visual neurons are stimulated by noise images and the spike output is cross-correlated with the input.
What is a classification image?
The classification image shows how the observer weights the information
in the image to reach a decision.
Signal Detection Theory
Noise+Signal
0 2 4 6 8 10
Internal response
Pro
ba
bili
ty
MISS HIT
Criterion response
Signal
Noise
Signal + Noise
Signal
Noise
Signal + Noise
+
+
+
+
<M>
+
+
+
+
<H>
Noise
0 2 4 6 8 10
Internal response
Pro
ba
bili
ty
Corr rej False alarm
Criterion response
+
+
+
+
<CR>
+
+
+
+
<FA>
Signal
Noise
Signal + Noise
Signal
Noise
Signal + Noise
Classification imageClassification image
+
+
+
+
<M>
+
+
+
+
<H>
+
+
+
+
<CR>
+
+
+
+
<FA>
CI = <H> - <M> + <FA> - <CR> =
Gold, J.M., Murray, R.F., Bennett, P.J., & Sekuler, A.B. Current Biology 2000.
Gosselin F. & Schyns P. Psychological Science, 14, 504-509, 2003.
Internal representation?Internal representation?
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”.
Black discsdisc diameter - 20’
speed - 5 deg/s4 frames of 50 ms
display size - 10x10 deg
Global motion direction
SignalSignal
Response Response RightRight LeftLeft
RightRight RR (NRR (NRRRR)) LR (NLR (NLRLR))
LeftLeft RL (NRL (NRLRL)) LL (NLL (NLLLL))
RLLLLRRR N
ii
RL
N
ii
LL
N
ii
LR
N
ii
RR
RLN
LLN
LRN
RRN
imagetionClassifica1111
)(1
)(1
)(1
)(1
Perceptive field of ideal observerif MDi> 0 => Right if MDi< 0 => Left
Global motion directionnormal observers
Subj. DD
-100
10
-10
0
10-10
0
10
20
Distance (deg)
(a) Classification Image
Distance (deg)
Am
plit
ude
-100
10
-10
0
100
10
20
Distance (deg)
(b) Classification Image p<0.001
Distance (deg)
Am
plit
ude
Perc Correct: 84 %
Distance (deg)
Dis
tanc
e (d
eg)
-5 0 5
-5
0
5
-10
0
10
Trials: 600
Distance (deg)-5 0 5
-5
0
5
-10
0
10
Global motion directionnormal observers
Subj. JPK
-100
10
-10
0
10-20
0
20
40
Distance (deg)
(a) Classification Image
Distance (deg)
Am
plit
ude
-100
10
-10
0
100
20
40
Distance (deg)
(b) Classification Image p<0.001
Distance (deg)
Am
plit
ude
Perc Correct: 88 %
Distance (deg)
Dis
tanc
e (d
eg)
-5 0 5
-5
0
5
-20
0
20
Trials: 600
Distance (deg)-5 0 5
-5
0
5
-20
0
20
Global motion directionnormal observers
Subj. IMK
-100
10
-10
0
10-20
0
20
40
Distance (deg)
(a) Classification Image
Distance (deg)
Am
plit
ude
-100
10
-10
0
100
10
20
30
Distance (deg)
(b) Classification Image p<0.001
Distance (deg)
Am
plit
ude
Perc Correct: 81 %
Distance (deg)
Dis
tanc
e (d
eg)
-5 0 5
-5
0
5
-20
-10
0
10
20
Trials: 600
Distance (deg)-5 0 5
-5
0
5
-20
-10
0
10
20
Global motion directionnormal observers
Subj. LS
-100
10
-10
0
10-10
0
10
20
Distance (deg)
(a) Classification Image
Distance (deg)
Am
plit
ude
-100
10
-10
0
100
10
20
Distance (deg)
(b) Classification Image p<0.001
Distance (deg)
Am
plit
ude
Perc Correct: 83 %
Distance (deg)
Dis
tanc
e (d
eg)
-5 0 5
-5
0
5
-15
-10
-5
0
5
10
15Trials: 600
Distance (deg)-5 0 5
-5
0
5
-15
-10
-5
0
5
10
15
Global motion directionnormal observers
Average
-100
10
-10
0
10-20
0
20
40
Distance (deg)
(a) Classification Image
Distance (deg)
Am
plit
ude
-100
10
-10
0
100
10
20
30
Distance (deg)
(b) Classification Image p<0.001
Distance (deg)
Am
plit
ude
Perc Correct: 83 %
Distance (deg)
Dis
tanc
e (d
eg)
-5 0 5
-5
0
5
-20
-10
0
10
20
Trials: 2400
Distance (deg)-5 0 5
-5
0
5
-20
-10
0
10
20
AmblyopiaAmblyopia (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
-100
10
-10
0
10-10
0
10
20
30
Distance (deg)
(a) Classification Image
Distance (deg)
Am
plit
ude
-100
10
-10
0
100
10
20
30
Distance (deg)
(b) Classification Image p<0.001
Distance (deg)
Am
plit
ude
Perc Correct: 76 %
Distance (deg)
Dis
tanc
e (d
eg)
-5 0 5
-5
0
5
-30
-20
-10
0
10
20
30Trials: 600
Distance (deg)-5 0 5
-5
0
5
-20
0
20
-100
10
-10
0
10-10
0
10
20
30
Distance (deg)
(a) Classification Image
Distance (deg)
Am
plit
ude
-100
10
-10
0
100
10
20
30
Distance (deg)
(b) Classification Image p<0.001
Distance (deg)
Am
plit
ude
Perc Correct: 88 %
Distance (deg)
Dis
tanc
e (d
eg)
-5 0 5
-5
0
5
-30
-20
-10
0
10
20
30Trials: 600
Distance (deg)-5 0 5
-5
0
5
-10
-5
0
5
10
Global motion direction
Subj. KH Amblyopic eye Fellow eye
Global motion direction
Subj. LW Amblyopic eye Fellow eye
-100
10
-10
0
10-10
0
10
20
Distance (deg)
(a) Classification Image
Distance (deg)
Am
plit
ude
-100
10
-10
0
100
10
20
Distance (deg)
(b) Classification Image p<0.001
Distance (deg)
Am
plit
ude
Perc Correct: 72 %
Distance (deg)
Dis
tanc
e (d
eg)
-5 0 5
-5
0
5
-20
-10
0
10
20Trials: 600
Distance (deg)-5 0 5
-5
0
5
-10
-5
0
5
10
-100
10
-10
0
10-10
0
10
20
Distance (deg)
(a) Classification Image
Distance (deg)
Am
plit
ude
-100
10
-10
0
100
10
20
Distance (deg)
(b) Classification Image p<0.001
Distance (deg)
Am
plit
ude
Perc Correct: 73 %
Distance (deg)
Dis
tanc
e (d
eg)
-5 0 5
-5
0
5
-20
-10
0
10
20Trials: 600
Distance (deg)-5 0 5
-5
0
5
-20
0
20
Global motion direction
Average Amblyopic eye Fellow eye
Global motion direction
Subj. DD Subj. JPK VA 6/18
Global motion direction
CH
0.5
0.6
0.7
0.8
0.9
1
0 5 10 15 20
Relative motion direction (deg)
Pro
po
rtio
n c
orr
ect
re
spo
nse
s
AE 9x9
Global motion direction
CH
0.5
0.6
0.7
0.8
0.9
1
0 5 10 15 20
Relative motion direction (deg)
Pro
po
rtio
n c
orr
ect
re
spo
nse
s
FE 9x9
AE 9x9
Global motion direction
CH
0.5
0.6
0.7
0.8
0.9
1
0 5 10 15 20
Relative motion direction (deg)
Pro
po
rtio
n c
orr
ect
re
spo
nse
s
FE 9x9
AE 9x9
FE 3x3
Global motion direction
CH
0.5
0.6
0.7
0.8
0.9
1
0 5 10 15 20
Relative motion direction (deg)
Pro
po
rtio
n c
orr
ect
re
spo
nse
s
FE 9x9AE 9x9FE 3x3AE 3x3
Dyslexia
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
Dyslexia
Global motion direction
Dyslexia
Average
Persistent Migraine Aura
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
Persistent Migraine Aura
Global motion direction
Persistent Migraine Aura
Average
SUMMARY
1. Classification image technique provides a new powerful tool for estimating the observers’ behavioural template for detecting objects.
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.
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.
5. In the presence of environmental noise, these individuals may have deficits in exclusion of unwanted distractors.
Thank you.Thank you.
Perceptual noise-exclusion deficits Perceptual noise-exclusion deficits in dyslexiain dyslexia
Sperling et al., (2005). Nature Neuroscience, 8, 862-863.
Perceptual noise-exclusion deficits Perceptual noise-exclusion deficits in dyslexiain dyslexia
0.0
0.3
0.6
0.9
1.2
No Noise High Noise
Co
ntr
ast
thre
sho
ld (
%)
Non-dyslexics Dyslexics16
8
4
2
1
Global motion direction
Persistent Migraine Aura
0
0.05
0.1
0.15
0.2
0.25
Control (n=7) Persistent Aura (n=5)
Effi
cien
cy
2
2
ideald
realdEfficiency