Fig. 2.

The localisation of ECoG electrodes in standardised image space. A) The patient electrode grid on cortical surface during surgical implantation. B) The lateral and coronal views showing the position of these electrodes in MRI (greyscale) overlaid with the coregistered CT image (red) in native space. The CT image is masked and thresholded to show just the densities corresponding to the electrodes. C) Coronal view of the patient's normalised MRI and coregistered CT. D & E) Electrode localisation and selection for the two patients, L1 and R2. Left column: CT image thresholded to show voxel densities corresponding to electrodes. The centre of each electrode voxel cluster is taken as the coordinate for that electrode and is shown overlaid on a MNI template brain in the centre column. Here electrodes are labelled according to the temporal (green) or frontal (blue) region of interest. The electrodes which disappear between the voxel clusters (left) and localised coordinates (centre) were either not recorded from or we removed them due to high epileptiform activity. Right column: Mean CNRs for each electrode in the regions of interest between 150 and 250 msec. The electrodes with highest mean CNR are circled in red and have the following MNI coordinates: Patient L1 STG [−69, −35, 7] and IFG [−63, 8, −1], patient R2 STG [71, −37, 14] and IFG [68, 0, 17].