Effect of spatial smoothing on task fMRI ICA and functional connectivity

Zikuan Chen, Vince Calhoun

Research output: Contribution to journalArticlepeer-review

20 Scopus citations


Spatial smoothing is a widely used preprocessing step in functional magnetic resonance imaging (fMRI) data analysis. In this work, we report on the spatial smoothing effect on task-evoked fMRI brain functional mapping and functional connectivity. Initially, we decomposed the task fMRI data into a collection of components or networks by independent component analysis (ICA). The designed task paradigm helps identify task-modulated ICA components (highly correlated with the task stimuli). For the ICA-extracted primary task component, we then measured the task activation volume at the task response foci. We used the task timecourse (designed) as a reference to order the ICA components according to the task correlations of the ICA timecourses. With the re-ordered ICA components, we calculated the inter-component function connectivity (FC) matrix (correlations among the ICA timecourses). By repeating the spatial smoothing of fMRI data with a Gaussian smoothing kernel with a full width at half maximum (FWHM) of (1, 3, 6, 9, 12, 15, 20, 25, 30, 35) mm, we measured the spatial smoothing effects. Our results show spatial smoothing reveals the following effects: (1) It decreases the task extraction performance of single-subject ICA more than that of multi-subject ICA; (2) It increases the task volume of multi-subject ICA more than that of single-subject ICA; (3) It strengthens the functional connectivity of single-subject ICA more than that of multi-subject ICA; and (4) It impacts the positive-negative imbalance of single-subject ICA more than that of multi-subject ICA. Our experimental results suggest a 2~3 voxel FWHM spatial smoothing for single-subject ICA in achieving an optimal balance of functional connectivity, and a wide range (2~5 voxels) of FWHM for multi-subject ICA.

Original languageEnglish (US)
Article number15
JournalFrontiers in Neuroscience
Issue numberFEB
StatePublished - Feb 2 2018


  • Correlation scale invariance
  • Function connectivity (FC)
  • Independent component analysis (ICA)
  • Spatial correlation (scorr)
  • Spatial smoothing
  • Task correlation
  • Task fMRI
  • Task function mapping

ASJC Scopus subject areas

  • Neuroscience(all)


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