AICHA: An atlas of intrinsic connectivity of homotopic areas

J Neurosci Methods. 2015 Oct 30;254:46-59. doi: 10.1016/j.jneumeth.2015.07.013. Epub 2015 Jul 23.

Abstract

Background: Atlases of brain anatomical ROIs are widely used for functional MRI data analysis. Recently, it was proposed that an atlas of ROIs derived from a functional brain parcellation could be advantageous, in particular for understanding how different regions share information. However, functional atlases so far proposed do not account for a crucial aspect of cerebral organization, namely homotopy, i.e. that each region in one hemisphere has a homologue in the other hemisphere.

New method: We present AICHA (for Atlas of Intrinsic Connectivity of Homotopic Areas), a functional brain ROIs atlas based on resting-state fMRI data acquired in 281 individuals. AICHA ROIs cover the whole cerebrum, each having 1-homogeneity of its constituting voxels intrinsic activity, and 2-a unique homotopic contralateral counterpart with which it has maximal intrinsic connectivity. AICHA was built in 4 steps: (1) estimation of resting-state networks (RSNs) using individual resting-state fMRI independent components, (2) k-means clustering of voxel-wise group level profiles of connectivity, (3) homotopic regional grouping based on maximal inter-hemispheric functional correlation, and (4) ROI labeling.

Results: AICHA includes 192 homotopic region pairs (122 gyral, 50 sulcal, and 20 gray nuclei). As an application, we report inter-hemispheric (homotopic and heterotopic) and intra-hemispheric connectivity patterns at different sparsities.

Comparison with existing method: ROI functional homogeneity was higher for AICHA than for anatomical ROI atlases, but slightly lower than for another functional ROI atlas not accounting for homotopy.

Conclusion: AICHA is ideally suited for intrinsic/effective connectivity analyses, as well as for investigating brain hemispheric specialization.

Keywords: Atlas; Brain parcellation; Homotopy; Intrinsic connectivity; Resting state; fMRI.

MeSH terms

  • Adolescent
  • Adult
  • Atlases as Topic*
  • Brain / anatomy & histology
  • Brain / physiology*
  • Brain Mapping* / methods
  • Female
  • Functional Laterality
  • Humans
  • Imaging, Three-Dimensional / methods
  • Magnetic Resonance Imaging* / methods
  • Male
  • Middle Aged
  • Neural Pathways / anatomy & histology
  • Neural Pathways / physiology
  • Rest
  • Signal Processing, Computer-Assisted
  • Young Adult