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Abstract #0210

fMRI post-stimulus undershoots in visual cortex are neuronal in origin

Karen J Mullinger 1,2 , Matthew Cherukara 1 , Susan T Francis 1 , and Stephen D Mayhew 2

1 SPMIC, School of Physics and Astronomy, University of Nottingham, Nottingham, Nottinghamshire, United Kingdom, 2 BUIC, School of Psychology, University of Birmingham, Birmingham, West Midlands, United Kingdom

The fMRI post-stimulus undershoot is widely observed but its origins remain unclear. We recorded EEG-BOLD-ASL responses to 10s-duration flickering and static visual checkerboard stimuli and show that the amplitude of both the BOLD and CBF post-stimulus undershoots in V1 are negatively correlated with the 10-20s post-stimulus power of the occipital EEG alpha (8-13Hz) oscillation. In addition, flicker trials resulted in both significantly larger fMRI undershoots and significantly higher post-stimulus alpha power responses than static trials. These results provide further evidence that the fMRI undershoot arises from a neuronal mechanism and comprises a unique feature of brain activity.

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