Journal
CEREBRAL CORTEX
Volume 31, Issue 3, Pages 1622-1631Publisher
OXFORD UNIV PRESS INC
DOI: 10.1093/cercor/bhaa314
Keywords
gain; gamma-band oscillations; luminance contrast; MEG; motion coherence
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Funding
- European Research Council (ERC) [StG335880]
- Centre for Integrative Neuroscience (DFG) [EXC 307]
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Our study demonstrated that gamma-band activity acts as a cortical gain mechanism that nonlinearly combines the bottom-up drive of different visual features, as evidenced by multiplicative interaction between motion coherence and contrast in their joint drive of gamma-band activity.
Synchronized neuronal population activity in the gamma-frequency range (>30 Hz) correlates with the bottom-up drive of various visual features. It has been hypothesized that gamma-band synchronization enhances the gain of neuronal representations, yet evidence remains sparse. We tested a critical prediction of the gain hypothesis, which is that features that drive synchronized gamma-band activity interact super-linearly. To test this prediction, we employed whole-head magnetencephalography in human subjects and investigated if the strength of visual motion (motion coherence) and luminance contrast interact in driving gamma-band activity in visual cortex. We found that gamma-band activity (64-128 Hz) monotonically increased with coherence and contrast, while lower frequency activity (8-32 Hz) decreased with both features. Furthermore, as predicted for a gain mechanism, we found a multiplicative interaction between motion coherence and contrast in their joint drive of gamma-band activity. The lower frequency activity did not show such an interaction. Our findings provide evidence that gamma-band activity acts as a cortical gain mechanism that nonlinearly combines the bottom-up drive of different visual features.
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