ABSTRACT
Background Intracranial electrical recordings (iEEG) and brain stimulation (iEBS) are invaluable human neuroscience methodologies. However, much of the value of such data is unrealized as many labs lack tools for precisely localizing electrodes relative to anatomy and to other functional measures. To remedy this, we have developed a MATLAB toolbox for intracranial electrode localization and visualization, iELVis.
New Method The iELVis pipeline extends existing tools (BioImage Suite, FSL, and FreeSurfer) for localizing electrode locations in CT or MR scans. Once electrode locations are identified in postimplant neuroimaging, iELVis implements methods for correcting electrode locations for postimplant brain shift with millimeter-scale accuracy. iELVis then supports interactive visualization on 3D surfaces or in 2D slices alongside functional neuroimaging data. iELVis also localizes electrodes relative to FreeSurfer-based atlases and can combine data across subjects via the FreeSurfer average brain.
Results It takes 30-60 minutes of user time and 12-24 hours of computer time to localize and visualize electrodes from one brain. We demonstrate iELVis’s co-registered visualization functionality by overlaying concordant results from three methods for mapping primary hand somatosensory cortex (iEEG, iEBS, and fMRI).
Comparison with Existing Methods iELVis standardizes existing approaches within a common pipeline, while advancing and combining the state of the art techniques in (i) brain-shift correction, (ii) atlas functionality, and (iii) multimodal visualization for human intracranial data.
Conclusions iELVis promises to speed and enhance the robustness of intracranial electrode research. The software and extensive tutorial materials are freely available as part of the EpiSurg software project: https://github.com/episurg/episurg
