Compliant head probe for positioning electroencephalography electrodes and near-infrared spectroscopy optodes

Abstract

Abstract. A noninvasive head probe that combines near-infrared spectroscopy (NIRS) and electroencephalography (EEG) for simultaneous measurement of neural dynamics and hemodynamics in the brain is presented. It is composed of a compliant expandable mechanism that accommodates a wide range of head size variation and an elastomeric web that maintains uniform sensor contact pressure on the scalp as the mechanism expands and contracts. The design is intended to help maximize optical and electrical coupling and to maintain stability during head movement. Positioning electrodes at the inion, nasion, central, and preauricular fiducial locations mechanically shapes the probe to place 64 NIRS optodes and 65 EEG electrodes following the 10-5 scalp coordinates. The placement accuracy, precision, and scalp pressure uniformity of the sensors are evaluated. A root-mean-squared (RMS) positional precision of 0.89 AE 0.23 mm, percent arc subdivision RMS accuracy of 0.19 AE 0.15%, and mean normal force on the scalp of 2.28 AE 0.88 N at 5 mm displacement were found. Geometric measurements indicate that the probe will accommodate the full range of adult head sizes. The placement accuracy, precision, and uniformity of sensor contact pressure of the proposed head probe are important determinants of data quality in noninvasive brain monitoring with simultaneous NIRS-EEG.

Algorithm to find high density EEG scalp coordinates and analysis of their correspondence to structural and functional regions of the brain

“…Digitization methods (He and Estepp, 2013) and custom electrode designs (Koessler et al, 2008) are often used to translate the locations of measurement from the subject to the software analysis tools and methods. Head probes and caps can also be used to provide accurate and precise positioning of electrodes in a fast and convenient way (Giacometti and Diamond, 2013). However, the need for localization of scalp coordinates is still necessary for EEG data analysis.…”

Hemodynamic correlates of spontaneous neural activity measured by human whole-head resting state EEG + fNIRS

“…Technical progress has also made it possible to combine EEG with functional NIRS (fNIRS), another non-invasive method. This method, we refer to as EEG+fNIRS, yields similar measurements with lower space but higher time resolution, in a far more practical and cost-effective arrangement (Buccino et al, 2016;Giacometti and Diamond, 2013;Keles et al, 2014;Koch et al, 2006Koch et al, , 2008Koch et al, , 2009Roche-Labarbe et al, 2008;Safaie et al, 2013). The utility of fNIRS as an independent modality for investigating the adult brain hemodynamics (Gentili et al, 2013;Mesquita et al, 2010;White et al, 2009) as well as infant development (Lloyd-Fox et al, 2010) is already well established.…”

Correspondence of electroencephalography and near-infrared spectroscopy sensitivities to the cerebral cortex using a high-density layout

“…The positions chosen follow the layout of the NIRS–EEG head probe developed by our lab. 50 The source-detector pairs chosen have a mean separation distance of 42.30 ± 7.48 mm, as shown in Fig. 2.…”

“…A subset of 65 EEG electrode positions, corresponding to the 10-10 positioning layout, was chosen from the 329 positions for displaying the tabulated results in order to follow the layout of the NIRS-EEG head probe we use in our lab. 50 The electrodes selected for Table 2 are indicated in Fig. 1.…”