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Attention extracts signal in external noise: a BOLD fMRI study
Zhong-Lin Lu1, Xiangrui Li, Bosco S Tjan
1Department of Psychology, University of Southern California, SGM 501, 3620 McClintock Ave., Los Angeles, CA 90089-1061, USA. zhonglin@usc.edu
Journal of Cognitive Neuroscience
|May 4, 2010
Summary
Spatial attention enhances visual processing by reducing external noise. This study shows covert attention significantly lowers the impact of noise on brain activity in early visual areas, improving signal detection.
Area of Science:
- Neuroscience
- Visual Perception
- Cognitive Psychology
Background:
- Behavioral studies suggest spatial attention aids in excluding external noise.
- This implies a neural mechanism where attention modulates sensory processing in response to noise.
Purpose of the Study:
- To investigate if spatial attention reduces the impact of external noise on the Blood-Oxygen-Level-Dependent (BOLD) response in early visual cortical areas.
- To quantify the effect of covert attention on BOLD signal reduction and dynamic range under noisy conditions.
Main Methods:
- Functional magnetic resonance imaging (fMRI) was used to measure BOLD responses in visual areas.
- Participants performed a visual task under varying levels of external noise and signal contrast, with and without covert spatial attention.
Main Results:
- Covert attention reduced trial-by-trial BOLD responses by 15.5-18.9% in V1 under low signal contrast with external noise.
- Attention increased the BOLD dynamic range by at least threefold in V1-V4 and enhanced contrast gain by 2.6-3.8 fold.
- Overall, covert attention mitigated the impact of external noise by 73-85% in early visual areas.
Conclusions:
- Spatial attention effectively reduces the detrimental effects of external noise on neural processing in early visual cortex.
- Attentional modulation enhances the brain's ability to process visual signals by increasing dynamic range and contrast gain, even in the presence of noise.
