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Optimizing the order of operations for movement scrubbing: Comment on Power et al
1Department of Psychology, 530 Church Street, Ann Arbor, MI 48109, USA. jmcarp@umich.edu
Abstract:
A recent study by Power and colleagues shows that BOLD artifacts induced by head movement can substantially alter patterns of resting-state functional connectivity and proposes a novel procedure for reducing these artifacts by deleting (or "scrubbing") movement-contaminated volumes. The authors acknowledge that this work is descriptive and not prescriptive, and note that future studies may refine the proposed scrubbing method. Nevertheless, it is worth pointing out that this method can be improved substantially by a single transposition in the order of operations. Temporal filtering is known to introduce ringing artifacts that emanate from sharp transitions in signal intensity. The method proposed in the target article applies temporal filtering before deleting contaminated volumes-in effect, spreading movement-related artifacts backwards and forwards in time, but deleting only the originally contaminated data. Using simulated data, we show that deleting and replacing contaminated volumes before temporal filtering removes a greater proportion of artifactual signal while retaining a greater proportion of the original data.
Insights
Head movement causes artifacts in resting-state functional connectivity (rsFC) data. Reordering operations by removing contaminated data before temporal filtering significantly improves artifact reduction in rsFC analysis.
Area of Science:
- Neuroimaging
- Cognitive Neuroscience
- Data Analysis
Background:
- Head movement during resting-state functional connectivity (rsFC) scans introduces artifacts.
- These artifacts can significantly distort observed rsFC patterns.
- Existing methods for artifact reduction, such as scrubbing, may be suboptimal.
Purpose of the Study:
- To evaluate and improve a novel procedure for reducing head movement artifacts in rsFC data.
- To propose an optimized order of operations for artifact removal.
- To compare the efficacy of the proposed method against the original scrubbing technique.
Main Methods:
- Simulated rsFC data were used to test artifact reduction strategies.
- The original method involved temporal filtering followed by scrubbing (removing contaminated volumes).
- The proposed improved method involves scrubbing contaminated volumes before temporal filtering.
Main Results:
- The improved method, scrubbing before temporal filtering, removed a greater proportion of artifactual signal.
- The improved method retained a greater proportion of the original, uncontaminated data.
- Temporal filtering before scrubbing can spread artifacts, reducing its effectiveness.
Conclusions:
- Reordering the artifact removal process (scrubbing before temporal filtering) substantially enhances artifact reduction in rsFC data.
- This optimized procedure offers a more effective way to mitigate head movement artifacts.
- The findings suggest a refinement to current rsFC data processing pipelines.
