Surface based electrode localization and standardized regions of interest for intracranial EEG

Abstract

Intracranial recordings captured from subdural electrodes in patients with drug resistant epilepsy offer clinicians and researchers a powerful tool for examining neural activity in the human brain with high spatial and temporal precision. There are two major challenges, however, to interpreting these signals both within and across individuals. Anatomical distortions following implantation make accurately identifying the electrode locations difficult. In addition, because each implant involves a unique configuration, comparing neural activity across individuals in a standardized manner has been limited to broad anatomical regions such as cortical lobes or gyri. We address these challenges here by introducing a semi-automated method for localizing subdural electrode contacts to the unique surface anatomy of each individual, and by using a surface-based grid of regions of interest (ROIs) to aggregate electrode data from similar anatomical locations across individuals. Our localization algorithm, which uses only a postoperative CT and preoperative MRI, builds upon previous spring-based optimization approaches by introducing manually identified anchor points directly on the brain surface to constrain the final electrode locations. This algorithm yields an accuracy of 2 mm. Our surface-based ROI approach involves choosing a flexible number of ROIs with different spatial resolutions. ROIs are registered across individuals to represent identical anatomical locations while accounting for the unique curvature of each brain surface. This ROI based approach therefore enables group level statistical testing from spatially precise anatomical regions.

Attention improves memory by suppressing spiking-neuron activity in the human anterior temporal lobe

“…Pre-operative MRIs were used when post-operative MRIs were not available. The electrode locations were projected to the cortical surface of a Montreal Neurological Institute N27 standard brain, and atlas information for each electrode was obtained using a Talairach daemon 12 , 13 .…”

Spatial Localization of EEG Electrodes in a TOF+CCD Camera System

“…Assume that the electrode cap has a 30-channel EEG amplified signal recorder (Trotta et al, 2018). The electrode dot distribution diagram, provided by the electrode cap manufacturers, is typically shown in Figure 8.…”

Memorability of words in arbitrary verbal associations modulates memory retrieval in the anterior temporal lobe

“…We used the behavioural data from all 30 participants for the group-level analysis of memorability estimates. Inclusion criteria for the analysis of neural data were more restrictive: 1) each participant should have a structural MRI (Magnetic Resonance Imaging) scan to allow proper electrode localization 55 , 2) each participant should have at least 3 electrode contacts in the brain regions of interest (anterior and posterior temporal lobes; ATL and PTL) after removal of noisy electrodes (see Pre-processing steps below); 3) each participant should complete more than 10 correct trials 33 of the paired associates memory task across experimental sessions to ensure reasonable signal stability for the neural reinstatement analysis (see Extended Data Fig. 3 ); and 4) each participant should have no prior resection of brain regions.…”