Structural templates for imaging EEG cortical sources in infants

Abstract

Electroencephalographic (EEG) source reconstruction is a powerful approach that helps to unmix scalp signals, mitigates volume conduction issues, and allows anatomical localization of brain activity. Algorithms used to estimate cortical sources require an anatomical model of the head and the brain, generally reconstructed using magnetic resonance imaging (MRI). When such scans are unavailable, a population average can be used for adults, but no average surface template is available for cortical source imaging in infants. To address this issue, this paper introduces a new series of 12 anatomical models for subjects between zero and 24 months of age. These templates are built from MRI averages and volumetric boundary element method segmentation of head tissues available as part of the Neurodevelopmental MRI Database. Surfaces separating the pia mater, the gray matter, and the white matter were estimated using the Infant FreeSurfer pipeline. The surface of the skin as well as the outer and inner skull surfaces were extracted using a cube marching algorithm followed by Laplacian smoothing and mesh decimation. We post-processed these meshes to correct topological errors and ensure watertight meshes. The use of these templates for source reconstruction is demonstrated and validated using 100 high-density EEG recordings in 7-month-old infants. Hopefully, these templates will support future studies based on EEG source reconstruction and functional connectivity in healthy infants as well as in clinical pediatric populations. Particularly, they should make EEG-based neuroimaging more feasible in longitudinal neurodevelopmental studies where it may not be possible to scan infants at multiple time points. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=77 SRC="FIGDIR/small/162131v1_ufig1.gif" ALT="Figure 1"> View larger version (30K): org.highwire.dtl.DTLVardef@8d705dorg.highwire.dtl.DTLVardef@1cc0ac7org.highwire.dtl.DTLVardef@d791caorg.highwire.dtl.DTLVardef@a4707d_HPS_FORMAT_FIGEXP M_FIG C_FIG HighlightsO_LITwelve surface templates for infants in the 0-2 years old range are proposed C_LIO_LIThese templates can be used for EEG source reconstruction using existing toolboxes C_LIO_LIA relatively modest impact of age differences was found in this age range C_LIO_LICorrelation analysis confirms increasing source differences with age differences C_LIO_LISources reconstructed with infants versus adult templates significantly differ C_LI