Approximating Signal Sources in Stereo-EEG Single Pulse Electrical Stimulation using Re-referencing and Spectral Analysis

Abstract Stereoelectroencephalography (sEEG) is a method of epilepsy monitoring that uses stereotactically placed depth electrodes. Connectivity between brain regions may be assessed by delivering a current pulse from sEEG electrode(s) and monitoring all other electrodes for Brain Stimulation-Evoked Potentials (BSEPs). However, the shape, magnitude, and spectral content of BSEPs are sensitive to the analysis approaches used to study them. In order to understand the nuance between analysis and interpretation of BSEP data, we carefully apply and contrast modified common average & bipolar re-referencing techniques, combined with wavelet-based spectral analysis on measured data from 4 human subjects. Comparison between analysis approaches allows us to identify recording sites within, near, or far from the tissue source of the BSEPs they record. We further explore the interaction between re-referencing techniques and dipole source orientation, providing methods to estimate source location and upper bound of far field recordings. This systematic application and comparison of different analysis tools can enable those who study BSEPs to localize potential sources within, near, or far from measurement sites, and more accurately constrain how brain connectivity is understood from stimulation experiments. Author summary Brain stimulation evoked potentials can be driven by sources at, near, or far from the recording site. Classification of these evoked potentials into one of these domains can be done using established re-referencing and spectral analysis techniques. Specifically, modified common average and bipolar re-referencing allow delineation of near and far field boundaries while spectral analysis allows for identification of channels within active tissue. Competing Interest Statement The authors have declared no competing interest.