Qihong Zou1,2, Wanyong Shin1,3, Hong Gu1, Xiujuan Geng1, Wang Zhan4, Yufeng Zang2, Yihong Yang1
1Neuroimaging Research Branch, National Institute on Drug Abuse, National Institutes of Health, Baltimore, MD, United States; 2State Key Laboratory of Cognitive Neuroscience & Learning, Beijing Normal University, Beijing, China, People's Republic of; 3Imaging Institute, Cleveland Clinic, Cleveland, OH, United States; 4Center of Imaging for Neurodegenerative Diseases, University of California San Francisco, San Francisco, CA, United States
Fractional amplitude of low-frequency fluctuations (fALFF) has been used to measure the strength of spontaneous fluctuations of resting-state fMRI signal. However, its underlying mechanisms and inter-subject variations are unknown. In this study, voxel-wise correlations between fALFF and fractional volume of gray matter (fv,GM) across subjects are investigated. Our results show that fALFF and fv,GM are positively correlated over large parts of the brain and fv,GM can be used as a covariate to remarkably reduce inter-subject variations. These findings suggest that fALFF is related to tissue fraction and its inter-subject variations can be reduced by including fv,GM in group analyses.