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Published on: August 1, 2018
Contrast-dependent phase sensitivity in V1 but not V2 of macaque visual cortex
Shaun L Cloherty1, Michael R Ibbotson2
1National Vision Research Institute, Australian College of Optometry, Carlton, Victoria, Australia; ARC Centre of Excellence for Integrative Brain Function and Department of Optometry and Vision Sciences, University of Melbourne, Parkville, Victoria, Australia; and Department of Electrical and Electronic Engineering, University of Melbourne, Parkville, Victoria, Australia cloherty@nvri.org.au.
Complex cells in the visual cortex show altered phase sensitivity at low contrast. This suggests hierarchical processing differences between visual areas V1 and V2 in primates.
Area of Science:
- Neuroscience
- Visual Processing
- Primate Vision
Background:
- Neurons in the visual cortex exhibit varying selectivity for edge position (simple cells) versus position insensitivity (complex cells).
- Complex cells' phase sensitivity is contrast-dependent, suggesting receptive field structure changes with contrast.
- Visual areas V1 and V2 show distinct cell population balances and connectivity patterns.
Purpose of the Study:
- To investigate the relationship between contrast levels and spatial phase sensitivity in complex cells within primate V1 and V2.
- To explore potential hierarchical processing differences between V1 and V2 based on contrast-dependent phase sensitivity.
Main Methods:
- Electrophysiological recordings in macaque monkeys.
- Assessment of neuronal responses to moving sine-wave gratings at varying contrasts.
- Analysis of spatial phase sensitivity in V1 and V2 complex cells.
Main Results:
- A significant proportion of complex cells in V1 displayed increased phase sensitivity at low contrast.
- This phenomenon of increased phase sensitivity at low contrast was rarely observed in V2 complex cells.
- Findings suggest differential processing of visual information between V1 and V2.
Conclusions:
- Complex cells in V1 exhibit greater phase sensitivity at low contrast compared to V2.
- This contrast-dependent difference supports a hierarchical model of visual processing from V1 to V2.
- Differences may arise from V1's mixed subcortical and cortical inputs versus V2's purely cortical inputs.
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