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
SPMIC, School of Physics and Astronomy,
University of Nottingham, Nottingham, Nottinghamshire,
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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