Figure 1

Macro- and microelectrodes. (a,b row1) Intraoperative photograph of a surface subdural grid electrode and two “thumbtack” multielectrode for LFP and SUA recordings (T1 and T2) in Pt1, Pt3. (a,b row2, c,d) Histological reconstruction of electrode penetration track with the position of each microelectrode contact co-registered to the individual cortical layers in Pt1, Pt2, Pt3 and Pt5. Note that all the histologically evaluated electrode tracks verified normal cortical lamination around the electrode trajectory. (e) Grid, strip and microelectrode array locations in seven patients included in the study. Surface electrode locations (red filled circle) are superimposed on the 3D reconstructions of preoperative magnetic resonance imaging (MRI) based on postoperative CT scans, locations of microelectrodes (green filled circle) and stimulated electrode contacts with best-response (yellow filled circle) relative to seizure onset zone (blue open circle) and the surface projection of morphologically pathological area on the MRI, i.e. MRI lesion (grey filled circle). Patients 2, 3, 4, 5 and 7 have a pathology of focal cortical dysplasia placed locally deep in sulci and gyri below the marked area. Pt1 is MRI negative and Pt6 has a midline pathology (see Table 1). Note that all the laminar electrodes fell outside the MRI lesion, but inside or very close to seizure onset zone. (f) Photo of a 24-contact intracortical laminar multielectrode.