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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.

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## Carnegie Mellon University, Pittsburgh, PA

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**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**Recording & Stimulation**Posterior - Anterior 5mm Medial - Lateral 100μV 1° 0.2ms Samonds et al., J Neurosci (2009)**Recording & Stimulation**A P 1°**Evidence of disparity-dependent neuronal interactions**n = 63 Pairs 1.5 A r = 0.32 p = 0.01 1.0 ΔRF Distance (°) 0.5 0.0 -1.0 -0.5 0.0 0.5 1.0 Disparity Tuning Similarity (rdisp) Samonds et al., J Neurosci (2009)**Evidence of disparity-dependent neuronal interactions**0.4 r = 0.50 p < 0.001 0.3 0.2 Spike Correlation 0.1 0 -1.0 -0.5 0.0 0.5 1.0 -0.1 Disparity Tuning Similarity (rdisp) Samonds et al., J Neurosci (2009)**Response Onset**End of Stimulation Firing Rate Binocular Disparity (±1°) Binocular disparity tuning sharpens over time Samonds et al., J Neurosci (2009)**How do we quantify sharpening?**100 75 Firing Rate (sps) 50 preferred disparity 25 2nd preferred 3rd preferred least preferred 0 0 500 1000 Time (ms)**skewness >> 0**skewness = 0 skewness = 0 skewness << 0 skewness << 0 Measure sharpening with skewness mean firing rate skewness >> 0 firing rate disparity Samonds et al., J Neurosci (2009)**Measure sharpening with skewness**skewness = 0.5 skewness = 2.0**200**400 600 800 1000 Time (ms) Measure sharpening with skewness 2.5 2.0 1.5 Skewness 1.0 0.5 0.0 1.5 1.2 0.9 Skewness 0.6 0.3 -100 0 200 400 600 800 1000 0.0 Time (ms) 1.5 1.2 0.9 Skewness 0.6 0.3 0.0 -100 0**Measure sharpening with skewness**n = 41 neurons 50 40 30 Firing Rate (sps) 20 10 0 0.8 0.6 Skewness 0.4 0.2 0 -100 -100 0 0 100 100 200 200 300 300 400 400 500 500 600 600 700 700 800 800 900 900 1000 1000 Time (ms) Time (ms)**Increasing uncertainty – reduced binocular correspondence**50% correspondence 100% correspondence**Increasing uncertainty – reduced binocular correspondence**n = 14 neurons 50% correspondence 100% correspondence 50 40 50 30 Firing Rate (sps) 40 20 30 Firing Rate (sps) 10 20 0 0 200 400 600 800 1000 10 Time (ms) 1.4 1.4 0 1.2 1.2 0 200 400 600 800 1000 Time (ms) 1.0 1.0 0.8 0.8 0.6 0.6 Skewness Skewness 0.4 0.4 0.2 0.2 0.0 0.0 0 200 400 600 800 1000 0 200 400 600 800 1000 -0.2 -0.2 Time (ms) Time (ms)**Ambiguous Stereogram**B A B A B +0.188° 0° A B A B A -0.188° A B A B A B right eye left eye B A B A B A Increasing uncertainty – correspondence ambiguity 25% unambiguous random dots Julesz & Chang, BiolCybern (1976)**30**20 Firing Rate (sps) 10 1° 1° 25% unambiguous random dots 0 -1.0 -0.5 0.0 0.5 1.0 Horizontal Disparity (°) Increasing uncertainty – correspondence ambiguity**50**40 30 Firing Rate (sps) 20 10 0 -100 0 100 200 300 400 500 600 700 800 900 1000 Time (ms) 50 1° 1° 40 25% unambiguous random dots 30 Firing Rate (sps) 20 10 0 -100 0 100 200 300 400 500 600 700 800 900 1000 Time (ms) Increasing uncertainty – correspondence ambiguity far vs. near disparity (center) 10 far vs. near disparity (surround)**Increasing uncertainty – correspondence ambiguity**far vs. near disparity (center) n = 36 neurons 50 50 40 30 40 Firing Rate (sps) 20 30 10 0 20 0 200 400 600 800 1000 Time (ms) 10 far vs. near disparity (surround) Firing Rate (sps) 0 0 200 400 600 800 1000 Time (ms)**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 are presented with reduced or ambiguous stereo correspondence. Conclusion Recurrent interactions within and/or with V1 share binocular disparity information across space to reduce local uncertainty within individual V1 receptive fields.**Thank you for your attention!**Acknowledgements • 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.

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