Revisiting Amplitude of Low-Frequency Fluctuations (ALFF) in Resting-state fMRI: Clarifications and Improvements
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Summary
This summary is machine-generated.This study clarifies amplitude of low-frequency fluctuations (ALFF) and fractional ALFF (fALFF) measures in resting-state fMRI. It introduces new variants and shows that z-scoring impacts some metrics, aiding standardized analysis of neural activity.
Area Of Science
- Neuroimaging
- Functional Magnetic Resonance Imaging (fMRI)
- Signal Processing
Background
- Amplitude of Low-Frequency Fluctuations (ALFF) and fractional ALFF (fALFF) are key resting-state fMRI metrics for spontaneous neural activity.
- Existing inconsistencies in ALFF definitions and implementations create field-wide confusion.
- Clarifying these metrics is crucial for reliable interpretation of brain activity.
Purpose Of The Study
- To mathematically clarify ALFF and fALFF by introducing arithmetic mean (am) and quadratic mean (qm) defined variants.
- To investigate the relationship between Mean BOLD Intensity (MBI), amALFF, and qmALFF.
- To assess the impact of BOLD signal z-scoring on ALFF and fALFF metrics.
Main Methods
- Introduced arithmetic mean-defined ALFF/fALFF (amALFF/amfALFF) and quadratic mean-defined ALFF/fALFF (qmALFF/qmfALFF).
- Analyzed relationships between MBI, amALFF, and qmALFF across subjects and voxels using two independent fMRI datasets.
- Evaluated the effect of z-scoring the BOLD signal on ALFF and fALFF calculations.
Main Results
- MBI positively correlates with both amALFF and qmALFF, indicating a need for subject-level mean normalization.
- Normalized qmALFF/qmfALFF strongly correlate with normalized amALFF/amfALFF at subject and voxel levels.
- Z-scoring the BOLD signal does not alter amfALFF/qmfALFF but significantly changes amALFF/qmALFF.
Conclusions
- Proposed a standardized flowchart for temporal domain (f)ALFF calculation.
- Mathematical clarification and variant introduction aid in resolving ALFF/fALFF definition inconsistencies.
- Findings guide standardized resting-state fMRI analysis for spontaneous neural activity quantification.
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