Carnegie Mellon University, Pittsburgh, PA

V1 interactions reduce local uncertainty about binocular disparity over time

Jason M. Samonds, Ben Poole, Tai Sing Lee

Carnegie Mellon University, Pittsburgh, PA

V1 perspective of incoming visual information

Noise and background add uncertainty

Uncertainty in corresponding features between the eyes

left eye right eye

percept

stereo correspondence problem

Computer vision solution: sharing information

Recording & Stimulation

100μV

0.2ms

5mm

Medial - Lateral

Pos

terio

r - A

nter

ior

1°

Samonds et al., J Neurosci (2009)

Recording & Stimulation

A

P

1°

Disparity Tuning Similarity (rdisp)

ΔR

F D

ista

nce

(°) r = 0.32

p = 0.01

0.0

0.5

1.0

1.5

-1.0 -0.5 0.0 0.5 1.0

A n = 63 Pairs

Evidence of disparity-dependent neuronal interactions

Samonds et al., J Neurosci (2009)

Evidence of disparity-dependent neuronal interactions

Disparity Tuning Similarity (rdisp)-0.1

0

0.1

0.2

0.3

-1.0 -0.5 0.0 0.5 1.0

Spik

e C

orre

latio

nr = 0.50p < 0.001

0.4

Samonds et al., J Neurosci (2009)

Binocular disparity tuning sharpens over time

Binocular Disparity (±1°)

Firin

g R

ate

Response Onset End of Stimulation

Samonds et al., J Neurosci (2009)

How do we quantify sharpening?

0

25

50

75

100

0 500 1000

Firin

g R

ate

(sps

)

preferred disparity2nd preferred3rd preferredleast preferred

Time (ms)

Measure sharpening with skewness

3

1

2

1

3

33

1

))((1

))((1

N

d

N

d

fdfN

fdfN

skewness << 0

skewness << 0

skewness = 0

skewness = 0

skewness >> 0

skewness >> 0disparity

meanfiring rate

firin

g ra

teSamonds et al., J Neurosci (2009)

Measure sharpening with skewness

skewness = 0.5 skewness = 2.0

Measure sharpening with skewness

0.0

0.5

1.0

1.5

2.0

2.5

Skew

ness

1.5

0.0

0.3

0.6

0.91.2

Skew

ness

200 400 600 800 1000Time (ms)

-100 00.0

0.3

0.6

0.91.2

1.5

Skew

ness

200 400 600 800 1000Time (ms)

-100 0

Measure sharpening with skewness

0

0.2

0.4

0.6

0.8

-100 0 100 200 300 400 500 600 700 800 900 1000

Time (ms)

Skew

ness

0

10

20

30

40

50Fi

ring

Rat

e (s

ps)

n = 41 neurons

-100 0 100 200 300 400 500 600 700 800 900 1000

Time (ms)

Increasing uncertainty – reduced binocular correspondence

100% correspondence 50% correspondence

Increasing uncertainty – reduced binocular correspondence

-0.20.00.20.40.60.81.01.21.4

0 200 400 600 800 1000Time (ms)

Skew

ness

n = 14 neurons

0

10

20

30

40

50

0 200 400 600 800 1000Time (ms)

Firin

g R

ate

(sps

) 100% correspondence 50% correspondence

0

10

20

30

40

50

0 200 400 600 800 1000Time (ms)

Firin

g R

ate

(sps

)

-0.20.00.20.40.60.81.01.21.4

0 200 400 600 800 1000Time (ms)

Skew

ness

A B A B A B B A B A B A

Ambiguous Stereogram

0°A B A B A

B A B A B

-0.188°

+0.188°

left eye right eye25% unambiguous random dots

Increasing uncertainty – correspondence ambiguity

Julesz & Chang, Biol Cybern (1976)

1°

0

10

20

30

-1.0 -0.5 0.0 0.5 1.0

Horizontal Disparity (°)

Firin

g R

ate

(sps

)

25% unambiguous random dots

1°

Increasing uncertainty – correspondence ambiguity

-100 0 100 200 300 400 500 600 700 800 900 1000Time (ms)

0

10

20

30

40

50

Firin

g R

ate

(sps

)

far vs. near disparity (center)

0

10

20

30

40

50

-100 0 100 200 300 400 500 600 700 800 900 1000Time (ms)

Firin

g R

ate

(sps

)

far vs. near disparity (surround)1°

25% unambiguous random dots

1°

Increasing uncertainty – correspondence ambiguity

10

Time (ms)0 200 400 600 800 1000

0

10

20

30

40

50 far vs. near disparity (center)

Firin

g R

ate

(sps

)

Increasing uncertainty – correspondence ambiguity

0

10

20

30

40

50

0 200 400 600 800 1000

Firin

g R

ate

(sps

)

Time (ms)

n = 36 neurons

far vs. near disparity (surround)

Summary

Spike correlation in V1 depends on spatial and binocular disparity tuning relationships.

Binocular disparity tuning sharpens over time.

Binocular disparity tuning sharpening is clearer when stimuli arepresented with reduced or ambiguous stereo correspondence.

Conclusion

Recurrent interactions within and/or with V1 share binoculardisparity information across space to reduce local uncertainty within individual V1 receptive fields.

Thank you for your attention!

Brian Potetz, Karen McCracken, Matt Smith, Ryan Poplin, and Nicholas Hatsopoulos for assistance.

Supported by: NEI F32 EY017770, NSF CISE IIS 0713206, AFOSR FA9550-09-1-0678 and a grant from Pennsylvania Department of Health through the Commonwealth Universal Research Enhancement Program.

Acknowledgements