title: Low-Frequency Fluctuations of the Resting Brain: High Magnitude Does Not Equal High Reliability.
abstract: The amplitude of low-frequency fluctuation (ALFF) measures low-frequency oscillations of the blood-oxygen-level-dependent signal, characterizing local spontaneous activity during the resting state. ALFF is a commonly used measure for resting-state functional magnetic resonance imaging (rs-fMRI) in numerous basic and clinical neuroscience studies. Using a test-retest rs-fMRI dataset consisting of 21 healthy subjects and three repetitive scans, we found that several key brain regions with high ALFF intensities (or magnitude) had poor reliability. Such regions included the posterior cingulate cortex, the medial prefrontal cortex in the default mode network, parts of the right and left thalami, and the primary visual and motor cortices. The above finding was robust with regard to different sample sizes (number of subjects), different scanning parameters (repetition time) and variations of test-retest intervals (i.e., intra-scan, intra-session, and inter-session reliability), as well as with different scanners. Moreover, the qualitative, map-wise results were validated further with a region-of-interest-based quantitative analysis using "canonical" coordinates as reported previously. Therefore, we suggest that the reliability assessments be incorporated in future ALFF studies, especially for the brain regions with a large ALFF magnitude as listed in our paper. Splitting single data into several segments and assessing within-scan "test-retest" reliability is an acceptable alternative if no "real" test-retest datasets are available. Such evaluations might become more necessary if the data are collected with clinical scanners whose performance is not as good as those that are used for scientific research purposes and are better maintained because the lower signal-to-noise ratio may further dampen ALFF reliability.
authors.affiliation: Zhejiang Provincial People's Hospital, Hangzhou, Zhejiang Province, P. R. China.
authors.forename: Dewang
authors.initials: D
authors.lastname: Mao
authors.affiliation: Zhejiang Provincial People's Hospital, Hangzhou, Zhejiang Province, P. R. China.
authors.forename: Zhongxiang
authors.initials: Z
authors.lastname: Ding
authors.affiliation: Center for Cognition and Brain Disorders, Hangzhou Normal University, Hangzhou, Zhejiang Province, P. R. China; Zhejiang Key Laboratory for Research in Assessment of Cognitive Impairments, Hangzhou, Zhejiang Province, P. R. China.
authors.forename: Wenbin
authors.initials: W
authors.lastname: Jia
authors.affiliation: Center for Cognition and Brain Disorders, Hangzhou Normal University, Hangzhou, Zhejiang Province, P. R. China; Zhejiang Key Laboratory for Research in Assessment of Cognitive Impairments, Hangzhou, Zhejiang Province, P. R. China.
authors.forename: Wei
authors.initials: W
authors.lastname: Liao
authors.affiliation: Center for Cognition and Brain Disorders, Hangzhou Normal University, Hangzhou, Zhejiang Province, P. R. China; Zhejiang Key Laboratory for Research in Assessment of Cognitive Impairments, Hangzhou, Zhejiang Province, P. R. China.
authors.forename: Xun
authors.initials: X
authors.lastname: Li
authors.affiliation: Center for Cognition and Brain Disorders, Hangzhou Normal University, Hangzhou, Zhejiang Province, P. R. China; Zhejiang Key Laboratory for Research in Assessment of Cognitive Impairments, Hangzhou, Zhejiang Province, P. R. China.
authors.forename: Huiyuan
authors.initials: H
authors.lastname: Huang
authors.affiliation: Zhejiang Provincial People's Hospital, Hangzhou, Zhejiang Province, P. R. China.
authors.forename: Jianhua
authors.initials: J
authors.lastname: Yuan
authors.affiliation: Center for Cognition and Brain Disorders, Hangzhou Normal University, Hangzhou, Zhejiang Province, P. R. China; Zhejiang Key Laboratory for Research in Assessment of Cognitive Impairments, Hangzhou, Zhejiang Province, P. R. China.
authors.forename: Yu-Feng
authors.initials: YF
authors.lastname: Zang
authors.affiliation: Center for Cognition and Brain Disorders, Hangzhou Normal University, Hangzhou, Zhejiang Province, P. R. China; Zhejiang Key Laboratory for Research in Assessment of Cognitive Impairments, Hangzhou, Zhejiang Province, P. R. China.
authors.forename: Han
authors.initials: H
authors.lastname: Zhang
mesh_terms: D000328:Adult; D001921:Brain / Q000502:physiology*; D019992:Databases as Topic; D005260:Female; D006179:Gyrus Cinguli / Q000502:physiology; D006257:Head; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D009038:Motion; D015203:Reproducibility of Results; D012146:Rest / Q000502:physiology*; D055815:Young Adult