Dipole Source Localization of Mouse Electroencephalogram Using the Fieldtrip Toolbox

Abstract

The mouse model is an important research tool in neurosciences to examine brain function and diseases with genetic perturbation in different brain regions. However, the limited techniques to map activated brain regions under specific experimental manipulations has been a drawback of the mouse model compared to human functional brain mapping. Here, we present a functional brain mapping method for fast and robust in vivo brain mapping of the mouse brain. The method is based on the acquisition of high density electroencephalography (EEG) with a microarray and EEG source estimation to localize the electrophysiological origins. We adapted the Fieldtrip toolbox for the source estimation, taking advantage of its software openness and flexibility in modeling the EEG volume conduction. Three source estimation techniques were compared: Distribution source modeling with minimum-norm estimation (MNE), scanning with multiple signal classification (MUSIC), and single-dipole fitting. Known sources to evaluate the performance of the localization methods were provided using optogenetic tools. The accuracy was quantified based on the receiver operating characteristic (ROC) analysis. The mean detection accuracy was high, with a false positive rate less than 1.3% and 7% at the sensitivity of 90% plotted with the MNE and MUSIC algorithms, respectively. The mean center-to-center distance was less than 1.2 mm in single dipole fitting algorithm. Mouse microarray EEG source localization using microarray allows a reliable method for functional brain mapping in awake mouse opening an access to cross-species study with human brain.

A Novel Visualization Method for Sleep Spindles Based on Source Localization of High Density EEG

“…We followed the procedures for the dipole source localizations described in our previous work ( Fig. 1 in [ 11 ]). Briefly, the boundary element model for the mouse brain was built based on mouse MRI to compute the leadfield matrix.…”

“…The LORETA or modified LORETA algorithms estimated the source deeper compared to MN. In our previous study based on optogenetic stimulation, the LORETA algorithm estimated the source deeper than the real source position [ 11 ]. On the other hand, the minimum norm algorithm estimated the sources successfully confined to the cortex.…”

“…However, for mice, the comprehensive method for neuroimaging and EEG topographic measure is limited due to the small size of mouse brain. Recently, we established the source localization technique [ 11 ] in mice with the developed high density EEG [ 12 13 ].…”

Pharmaco-EEG Studies in Animals: A History-Based Introduction to Contemporary Translational Applications

“…Source localisation of EEG effects in animals is more difficult in most species compared to humans due to the smaller size of the brain, which is also more embedded in the skull, making it more difficult to use a 3D EEG imaging methodology such as LORETA. However, a new spatial mapping technique for modelling large-scale neuronal networks in mouse brains equivalent to human neuroimaging has been recently developed [90,91,92]. A polyimide-based array of 32 or 40 EEG microelectrodes was implemented to detect the location of the sources underlying EEG activation of depth brain structure by optogenetics or epileptic seizure loci in mice, which opens a new avenue of linking human brain mapping with aberrant molecular neuronal processes and circuits in animal models of diseases.…”

A non-invasive flexible multi-channel electrode for in vivo mouse EEG recording

“…We provided electrical stimulation (intensity 1.5 mA, pulse width 300 usec, frequency: 4 Hz) on the right hindlimb using external device (NI cDAQ 9265) synchronized with recording device through fieldtrip [10]. In this case, every session was made up of 20 trials and each trial was composed of 20 seconds (baseline 5 secconds, stimulation 2 seconds, and poststimulation 13 seconds) within the mouse was electrically stimulated 8 times.…”