Evaluating Methods for Constructing Average High-Density Electrode Positions

Abstract

Accurate analysis of scalp-recorded electrical activity requires the identification of electrode locations in 3D space. For example, source analysis of EEG/ERP (electroencephalogram, EEG; event-related-potentials, ERP) with realistic head models requires the identification of electrode locations on the head model derived from structural MRI recordings. Electrode systems must cover the entire scalp in sufficient density to discriminate EEG activity on the scalp and to complete accurate source analysis. The current study compares techniques for averaging electrode locations from 86 participants with the 128 channel “Geodesic Sensor Net” (GSN; EGI, Inc.), 38 participants with the 128 channel “Hydrocel Geodesic Sensor Net” (HGSN; EGI, Inc.), and 174 participants with the 81 channels in the 10-10 configurations. A point-set registration between the participants and an average MRI template resulted in an average configuration showing small standard errors, which could be transformed back accurately into the participants’ original electrode space. Average electrode locations are available for the GSN (86 participants), Hydrocel-GSN (38 participants), and 10-10 and 10-5 systems (174 participants)

Development of infant sustained attention and its relation to EEG oscillations: an EEG and cortical source analysis study

“…An anatomical MRI close in head size and age was selected for each infant from the Neurodevelopmental MRI Database (Richards et al, 2016; Richards & Xie, 2015) to create the realistic head models. MRIs were segmented into component materials and the gray matter and eyes were used as source volumes.…”

“…Cortical source analysis of the scalp-level PSD was conducted for these frequency rhythms with the CDR technique and realistic head models obtained from the Neurodevelopmental MRI Database (Richards, Sanchez, Phillips-Meek, & Xie 2016; Richards & Xie, 2015; Xie & Richards, 2016b). An accurate MRI model that describes the materials inside the head and their relative conductivity is beneficial for source analysis of EEG and ERPs (Michel et al, 2004; Reynolds & Richards, 2009).…”

Development of the error-monitoring system from ages 9–35: Unique insight provided by MRI-constrained source localization of EEG

“…Seven anatomical fiducials that are commonly used for the 10–10 system were digitized on each participant; these locations were the naision (Nz), the inion (Iz), the left mastoid (LMA), the right mastoid (RMA), the left pre-auricular (LPA), the right pre-auricular (RPA), and the vertex (Vz). Additionally, seven electrodes of the Hydrocel Geodesic Sensor Net 128 (HGSN128) that are located near the anatomical fiducials were digitized; the electrode numbers and their approximate corresponding anatomical landmarks were 17-Nz, 75-Oz, 57-LMA, 100-RMA, 44-LPA, 115-RPA, 129-Vz (see Richards et al, 2015). The following head measurements were also taken for each participant: front and rear semi-circumferences (LMA to RMA), top circumferences (Nz to Iz, and LMA to RMA), and lateral diameters (Nz to Iz, and LMA to RMA).…”

“…The electrode locations were then fit to the scalp by identifying the point of the scalp nearest to the transformed electrode locations and these locations were referenced to the individualized AC-coordinate system using the previously identified AC/PC locations. For more details on the electrode localization procedure see Richards and colleagues (2015).…”

The Relation between Infant Covert Orienting, Sustained Attention and Brain Activity

“…The segmented MRIs were then transformed to wireframes to complete the finite element method (FEM) models. Finally, an electrode placement map was constructed for each participant’s head model with methods that have been recently developed for adults (Richards, Boswell, Stevens, & Vendemia 2015a; Supplemental Information Figure 1). …”