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Proc Natl Acad Sci U S A. 2017 Jul 24. pii: 201706183. doi: 10.1073/pnas.1706183114. [Epub ahead of print]

Interactions between feedback and lateral connections in the primary visual cortex.

Author information

1
School of Biomedical Engineering, Drexel University, Philadelphia, PA 19104.
2
State Key Laboratory of Cognitive Neuroscience and Learning, Beijing Normal University, Beijing 100875, China.
3
IDG/McGovern Institute for Brain Research, Beijing Normal University, Beijing 100875, China.
4
State Key Laboratory of Cognitive Neuroscience and Learning, Beijing Normal University, Beijing 100875, China; gilbert@rockefeller.edu liwu@bnu.edu.cn.
5
The Rockefeller University, New York, NY 10065 gilbert@rockefeller.edu liwu@bnu.edu.cn.

Abstract

Perceptual grouping of line segments into object contours has been thought to be mediated, in part, by long-range horizontal connectivity intrinsic to the primary visual cortex (V1), with a contribution by top-down feedback projections. To dissect the contributions of intraareal and interareal connections during contour integration, we applied conditional Granger causality analysis to assess directional influences among neural signals simultaneously recorded from visual cortical areas V1 and V4 of monkeys performing a contour detection task. Our results showed that discounting the influences from V4 markedly reduced V1 lateral interactions, indicating dependence on feedback signals of the effective connectivity within V1. On the other hand, the feedback influences were reciprocally dependent on V1 lateral interactions because the modulation strengths from V4 to V1 were greatly reduced after discounting the influences from other V1 neurons. Our findings suggest that feedback and lateral connections closely interact to mediate image grouping and segmentation.

KEYWORDS:

Granger causality; contour integration; feedback connection; horizontal connection; perceptual grouping

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