Electrical Source Imaging in Freely Moving Rats: Evaluation of a 12-Electrode Cortical Electroencephalography System

Abstract

This work presents and evaluates a 12-electrode intracranial electroencephalography system developed at the National Institute of Mental Health (Klecany, Czech Republic) in terms of an electrical source imaging (ESI) technique in rats. The electrode system was originally designed for translational research purposes. This study demonstrates that it is also possible to use this well-established system for ESI, and estimates its precision, accuracy, and limitations. Furthermore, this paper sets a methodological basis for future implants. Source localization quality is evaluated using three approaches based on surrogate data, physical phantom measurements, and in vivo experiments. The forward model for source localization is obtained from the FieldTrip-SimBio pipeline using the finite-element method. Rat brain tissue extracted from a magnetic resonance imaging template is approximated by a single-compartment homogeneous tetrahedral head model. Four inverse solvers were tested: standardized low-resolution brain electromagnetic tomography, exact low-resolution brain electromagnetic tomography (eLORETA), linear constrained minimum variance (LCMV), and dynamic imaging of coherent sources. Based on surrogate data, this paper evaluates the accuracy and precision of all solvers within the brain volume using error distance and reliability maps. The mean error distance over the whole brain was found to be the lowest in the eLORETA solution through signal to noise ratios (SNRs) (0.2 mm for 25 dB SNR). The LCMV outperformed eLORETA under higher SNR conditions, and exhibiting higher spatial precision. Both of these inverse solvers provided accurate results in a phantom experiment (1.6 mm mean error distance across shallow and 2.6 mm across subcortical testing dipoles). Utilizing the developed technique in freely moving rats, an auditory steady-state response experiment provided results in line with previously reported findings. The obtained results support the idea of utilizing a 12-electrode system for ESI and using it as a solid basis for the development of future ESI dedicated implants.

Psilocin, LSD, mescaline, and DOB all induce broadband desynchronization of EEG and disconnection in rats with robust translational validity

“…Inasmuch it seems that the disruption of stability and integrity of major large-scale brain networks [ 24 , 75 ] is one of the typical signs having the same direction of changes as may be seen in our data. Future challenges using methods of source localization in rats [ 78 ] will bring us to a point where connectivity analyses will be more translational.…”

Anisotropic Conductivity of Rat Head Phantom and its Influence on Electroencephalogram Source Localization

“…The source localization grid contained 52367 points which corresponded to the 4 millimeter spacing between surrounding solution points. For comparison, in our previous papers [32] and [17], 1557 and 2346 dipoles were used, respectively. Further increase of the grid density would lead to the dramatic increase of computational demands because a total number of source dipoles is proportional to the cube of a number of samples per direction.…”

“…Both methods were implemented in the fieldtrip toolbox [33]. For a more detailed description of both methods [32]. Since the DICS and eLORETA methods resulted in the very same localization errors on both phantoms, only the eLORETA results are reported here for the sake of brevity.…”

Electroencephalographic Response of Brain Stimulation by Shock Waves From Laser Generated Carbon Nanotube Transducer

“…The OpenBCI EEG system has previously been used for brain-computer interfaces (BCIs) and drowsiness detection [31,32]. In this study, the three electrodes were placed at T6, T5 and Reference region [33] of the rat's head, and a ground electrode was on the ear. Data were acquired over Bluetooth using the OpenBCI GUI on a Windows 10 laptop [34].…”