Evaluating dipolar source localization feasibility from intracerebral SEEG recordings

Abstract

Stereo-electroencephalography (SEEG) is considered as the golden standard for exploring targeted structures during pre-surgical evaluation in drug-resistant partial epilepsy. The depth electrodes, inserted in the brain, consist of several collinear measuring contacts (sensors). Clinical routine analysis of SEEG signals is performed on bipolar montage, providing a focal view of the explored structures, thus eliminating activities of distant sources that propagate through the brain volume. We propose in this paper to exploit the common reference SEEG signals. In this case, the volume propagation information is preserved and electrical source localization (ESL) approaches can be proposed. Current ESL approach used to localize and estimate the activity of the neural generators are mainly based on surface EEG/MEG signals, but very few studies exist on real SEEG recordings, and the case of equivalent current dipole source localization has not been explored yet in this context. In this study, we investigate the influence of volume conduction model, spatial configuration of SEEG sensors and level of noise on the ESL accuracy, using a realistic simulation setup. Localizations on real SEEG signals recorded during intracerebral electrical stimulations (ICS, known sources) as well as on epileptic interictal spikes are carried out. Our results show that, under certain conditions, a straightforward approach based on an equivalent current dipole model for the source and on simple analytical volume conduction models yields sufficiently precise solutions (below 10mm) of the localization problem. Thus, electrical source imaging using SEEG signals is a promising tool for distant brain sources investigation and might be used as a complement to routine visual interpretations.

A Multi-Channel Approach for Cortical Stimulation Artefact Suppression in Depth EEG Signals Using Time-Frequency and Spatial Filtering

“…A five compartiment finite element modelling (FEM) is used to compute realistic lead-field (LF) matrix which represents the volume conduction forward model. For a more detailed description of the simulation setup, see [27]. As for every position we can have 3 elementary orthogonal dipoles orientated as, Ax: inion-nasion, Ay: right-left and Az: bottom-up, the final dimension of the LF matrix is 186 × 1569 (number of channels by number of elementary dipoles).…”

Data integration: Combined imaging and electrophysiology data in the cloud

“…These gold standard EEG datasets can validate inverse problem methods that users can run using the available APIs. Such methods already exist for iEEG [21], [22], which can be further developed and validated on the patients currently on the portal.…”

Assessing human brain impedance using simultaneous surface and intracerebral recordings

“…Pettersen et al, 2012)) and at macroscopic scale (dipolar fit, e.g. (Caune et al, 2014)). Direct confirmation of the dominantly resistive environment was provided by (Logothethis et al, 2007), who used an injected controlled current source in a particular geometrical setup in order to asses brain tissue impedance (which was found to have a rather insignificant frequency dependency, at about 1dB per decade).…”