Surround modulation (Series et al. 2003) Modeling Adult Visual - PowerPoint PPT Presentation

Surround modulation (Series et al. 2003) Modeling Adult Visual Function Dr. James A. Bednar jbednar@inf.ed.ac.uk http://homepages.inf.ed.ac.uk/jbednar Apparent contrast Detection facilitated Contour pops out reduces Many types of contextual interactions are known CNV Spring 2008: Modeling adult function 1 CNV Spring 2008: Modeling adult function 2 Surround modulation Proposed model circuit From Schwabe Effects et al. (2006): depend High-threshold strongly on inhibitory distance and interneurons (Schwabe et al. 2006) contrast (Schwabe et al. 2006) Long-range Distance- excitatory lateral connections related effects match both Long-range lateral and excitatory feedback feedback connections connections CNV Spring 2008: Modeling adult function 3 CNV Spring 2008: Modeling adult function 4

LESI circuit Effective lateral inhibition At high contrasts, the activity in the From Law & inhibitory sheet has wider radius than Bednar (2006): the activity in the excitatory sheet. High-threshold Result: Acts like Mexican-hat lateral (Law & Bednar 2006) inhibitory interaction function, but using Excitatory activity interneurons (Law & Bednar 2006) long-range excitatory connections. Long-range excitatory lateral Self-organization thus works as usual connections (since Hebbian learning is dominated by No feedback the high-contrast inputs), but circuitry is connections yet correct and low-contrast behavior can Inhibitory activity be correct. CNV Spring 2008: Modeling adult function 5 CNV Spring 2008: Modeling adult function 6 Stable development The Tilt Aftereffect (TAE) Standard LISSOM (Law & Bednar 2006) Homeostatic no-shrinking laminar LISSOM If the manual thresholds of standard LISSOM are replaced • Bias in orientation perception after prolonged exposure with homeostatic plasticity, excitatory radius shrinking can • Allows model structure to be related to adult function be eliminated. Result: map shape remains stable over time. CNV Spring 2008: Modeling adult function 7 CNV Spring 2008: Modeling adult function 8

TAE in Humans and LISSOM TAE Adaptation in LISSOM o 4 • Direct effect for • Adaptation : More Aftereffect Magnitude Adaptation + small angles inhibition, but no net o 2 − change in perception • Indirect effect for 0 ◦ o 0 larger angles • Direct effect: More inhibition for angles < 10 ◦ + o Direct −2 • Model − – Perception shifts perception: 10 ◦ o −4 from 10 to 14 ◦ vector average o o o o o o o −90 −60 −30 0 30 60 90 Angle on Retina of orientations + Indirect • Indirect effect: Less − inhibition for angles < 60 ◦ • Human, model 60 ◦ Mitchell & Muir 1976 – Perception shifts match closely HLISSOM from 60 to 58 ◦ Input Histogram V1 Activity pattern difference CNV Spring 2008: Modeling adult function 9 CNV Spring 2008: Modeling adult function 10 McCollough effect test pattern Adaptation pattern Before adaptation, this pattern should appear monochrome Stare alternately at the two patterns for 3 minutes, moving your gaze to avoid developing strong afterimages CNV Spring 2008: Modeling adult function 11 CNV Spring 2008: Modeling adult function 12

McCollough effect McCollough effect: data • Effect measured in (McCollough 1965) humans at each After adaptation: angle between (Ellis 1977) • Vertical bars adaptation and test should be slightly • Strength falls off magenta smoothly with angle (Landisman & Ts’o 2002) • Horizontal bars should be slightly • V1 is earliest green possible substrate – first area showing • The effect should reverse if you tilt your head 90 ◦ , OR selectivity; has and disappear if you tilt 45 ◦ . 2.3 × 5.3mm macaque V1 color map CNV Spring 2008: Modeling adult function 13 CNV Spring 2008: Modeling adult function 14 LISSOM Color V1 Model LISSOM OR + Color map • Input: RGB V1 images (Bednar et al. 2005) LGN • Decomposed into Red, Green Luminosity channels Green/Red (no blue in central (Bednar et al. 2005) Red/Green fovea, Calkins 2001 ) ON OFF Retina • Processed by color opponent Red Green • Orientation map similar to animal maps Channel Channel retinal ganglia • Color-selective cells occur in blobs Color Image • Each blob prefers either red or green CNV Spring 2008: Modeling adult function 15 CNV Spring 2008: Modeling adult function 16

Calculating McCollough Effect Model McCollough Effect • Perceived color estimated as a vector average of all units 6 4 • Vector direction: + for red-selective units, - for strength of the ME (in the model) 2 green-selective units 0 • Weighted by activation level and amount of color −2 selectivity −4 Result is a number from extreme red (positive) to extreme −6 green (negative), with approximately 0 being −45 −30 −15 0 15 30 45 60 75 90 105 120 135 orientation of the test pattern monochrome. CNV Spring 2008: Modeling adult function 17 CNV Spring 2008: Modeling adult function 18 Compared with human Summary • LISSOM can be compatible with actual circuit 1.2 simulated ME human data • May explain surround modulation 1 • Afteffects arise from Hebbian adaptation of lateral 0.8 strength of the ME inhibitory connections 0.6 0.4 • The same self-organizing processes can drive both 0.2 development and adaptation: both structure and 0 function −0.2 −45 −30 −15 0 15 30 45 • Novel prediction: Indirect effect due to weight orientation of the test pattern normalization CNV Spring 2008: Modeling adult function 19 CNV Spring 2008: Modeling adult function 20

McCollough Effect References Bednar, J. A., De Paula, J. B., & Miikkulainen, R. (2005). Self- organization of color opponent receptive fields and laterally con- nected orientation maps. Neurocomputing , 65–66 , 69–76. Is the effect still Calkins, D. J. (2001). Seeing with S cones. Progress in Retinal and Eye Research , 20 (3), 255–287. present? Ellis, S. R. (1977). Orientation selectivity of the McCollough effect: Anal- ysis by equivalent contrast transformation. Perception and Psy- chophysics , 22 (6), 539–544. Landisman, C. E., & Ts’o, D. Y. (2002). Color processing in macaque CNV Spring 2008: Modeling adult function 21 CNV Spring 2008: Modeling adult function 21 striate cortex: Relationships to ocular dominance, cytochrome ox- Mitchell, D. E., & Muir, D. W. (1976). Does the tilt aftereffect occur in the idase, and orientation. Journal of Neurophysiology , 87 (6), 3126– oblique meridian?. Vision Research , 16 , 609–613. 3137. Schwabe, L., Obermayer, K., Angelucci, A., & Bressloff, P . C. (2006). Law, J. S., & Bednar, J. A. (2006). Surround modulation by long-range The role of feedback in shaping the extra-classical receptive field lateral connections in an orientation map model of primary visual of cortical neurons: A recurrent network model. The Journal of cortex development and function. In Society for Neuroscience Neuroscience , 26 (36), 9117–9129. Abstracts . Society for Neuroscience, www.sfn.org. Program No. Series, P ., Lorenceau, J., & Fregnac, Y. (2003). The “silent” surround of 546.4. V1 receptive fields: Theory and experiments. Journal of Physiol- McCollough, C. (1965). Color adaptation of edge-detectors in the human ogy (Paris) , 97 (4–6), 453–474. visual system. Science , 149 (3688), 1115–1116. CNV Spring 2008: Modeling adult function 21 CNV Spring 2008: Modeling adult function 21