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Metamers of the ventral stream

Abstract

The human capacity to recognize complex visual patterns emerges in a sequence of brain areas known as the ventral stream, beginning with primary visual cortex (V1). We developed a population model for mid-ventral processing, in which nonlinear combinations of V1 responses are averaged in receptive fields that grow with eccentricity. To test the model, we generated novel forms of visual metamers, stimuli that differ physically but look the same. We developed a behavioral protocol that uses metameric stimuli to estimate the receptive field sizes in which the model features are represented. Because receptive field sizes change along the ventral stream, our behavioral results can identify the visual area corresponding to the representation. Measurements in human observers implicate visual area V2, providing a new functional account of neurons in this area. The model also explains deficits of peripheral vision known as crowding, and provides a quantitative framework for assessing the capabilities and limitations of everyday vision.

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Figure 1: Physiological measurements of receptive field size in macaque.
Figure 2: Mid-ventral model, example metameric stimuli and experimental task.
Figure 3: Metamer experiment results.
Figure 4: Metamer control experiments.
Figure 5: Summary of fitted critical scaling parameters for all experiments.
Figure 6: Crowding experiment.
Figure 7: Effects of crowding on reading and searching.

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Acknowledgements

We would like to thank R. Rosenholtz for early inspiration and discussions regarding the relationship between texture and crowding, N. Rust for discussions about the nature of information represented in the ventral stream, C. Anderson for discussions about the scaling of receptive fields with eccentricity, M. Landy, A. Girshick and R. Goris for advice on experimental design, C. Ekanadham and U. Rajashaker for advice on the model and analysis, and D. Ganguli, D. Heeger, J. McDermott, E. Merriam and C. Ziemba for comments on the initial manuscript. This work was supported by a National Science Foundation Graduate Student Fellowship to J.F. and a Howard Hughes Medical Institute Investigatorship to E.P.S.

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J.F. and E.P.S. conceived the project and designed the experiments. J.F. implemented the model, performed the experiments and analyzed the data. J.F. and E.P.S. wrote the manuscript.

Corresponding author

Correspondence to Jeremy Freeman.

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The authors declare no competing financial interests.

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Freeman, J., Simoncelli, E. Metamers of the ventral stream. Nat Neurosci 14, 1195–1201 (2011). https://doi.org/10.1038/nn.2889

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