Lirong Yan1, Yan Zhuo1, Yongquan Ye1, Sharon Xie2, Jing An3, Geoffrey Aguirre4, Jiongjiong Wang5
1State Key Laboratory of Brain and Cognitive Science, Institute of Biophysics, CAS, Beijing, China; 2Department of Biostatistics & Epidemiology, University of Pennsylvania, Philadelphia, PA, USA; 3Siemens Mindit Magnetic Resonance Ltd., Shenzhen, China; 4Neurology, University of Pennsylvania, Philadelphia, PA, USA; 5Radiology, University of Pennsylvania, Philadelphia, PA, USA
We investigated the biophysical mechanism of low frequency drift in BOLD fMRI (0~0.01Hz), by exploring its dependence on TE and image intensity as well as relationship with task-induced BOLD activation. Cardiac and respiratory signals were concurrently recorded during MRI scanning and subsequently removed. Drifts followed a characteristic dependence on TE and signal intensity that was similar to the BOLD contrast. There was a strong positive correlation between drift effects at baseline and tasked induced BOLD activation. Our study supports brain physiology, as opposed to scanner instabilities or cardiac/respiratory pulsations, as the main source of low frequency drifts in BOLD fMRI.
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