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John Serences; EEG and fMRI provide different insights into the link between attention and behavior in human visual cortex. Journal of Vision 2015;15(12):1413. doi: 10.1167/15.12.1413.
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© 2017 Association for Research in Vision and Ophthalmology.
A fMRI study by Pestilli et al. (2011) established a method for modeling links between attention-related changes in BOLD activation in visual cortex and changes in behavior. The study found that models based on sensory gain and noise reduction could not explain the relationship between attention-related changes in behavior and attention-related additive shifts of the BOLD contrast-response function (CRF). However, a model based on efficient post-sensory read-out successfully linked BOLD modulations and behavior.
We performed a similar study but used EEG instead of fMRI as a measure of neural activity in visual cortex (Itthipuripat et al., 2014). Instead of additive shifts in the BOLD response, attention induced a temporally early multiplicative gain of visually evoked potentials over occipital electrodes, and a model based on sensory gain sufficiently linked attention-induced changes in EEG responses and behavior, without the need to incorporate efficient read-out. We also observed differences between attention-induced changes in EEG-based CRFs (multiplicative gain) and fMRI-based CRFs (additive shift) within the same group of subjects who performed an identical spatial attention task. These results suggest that attentional modulation of EEG responses interacts with the magnitude of sensory-evoked responses, whereas attentional modulation of fMRI signals is largely stimulus-independent. This raises the intriguing possibility that EEG and fMRI signals provide complementary insights into cortical information processing, and that these complementary signals may help to better constrain quantitative models that link neural activity and behavior.
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