Xiao
Liu1,2, Xiao-Hong Zhu1, Wei Chen1,2
1CMRR, radiology, University of
Minnesota, Minneapolis, MN, United States; 2Biomedical
Engineering, University of Minnesota, Minneapolis, MN, United States
To
investigate whether subjects ongoing brain activity can affect their
response to external stimulation, fMRI BOLD signals were acquired from human
visual cortex under conditions with/without visual stimulation. It was found
that correlation strength but not fluctuation magnitude of spontaneous
(baseline) BOLD signals is positively correlated (R2 = 0.68, p-value = 2.3 10-4) with
the amplitude of evoked BOLD responses to visual stimulus. This finding
suggests that synchronization strength of ongoing brain activity may have an
important effect on evoked brain activity, even at the early stage of sensory
systems. Moreover, this study provides a neurophysiology basis for
quantitatively understanding large inter-subject BOLD variability commonly
observed in many fMRI studies.