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.