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. 2022 Sep 12;146(2):561–575. doi: 10.1093/brain/awac319

Figure 1.

Figure 1

Recording of intracerebral signals with micro-wires at a high sampling rate reveals local FRs and action potentials. (A) Example of a hybrid electrode location in one subject (Subject 8). Coronal co-registration MRI CT scan (preoperative 3D T1 MRI with gadolinium and postoperative CT scan). Circles are macro-contacts; the arrow specifies the putative location of tetrodes between the two deepest macro-contacts of the hybrid electrode. (B) Locations of every tetrode included in the study, referenced in the MNI space. Colours indicate whether FRs, single units (neurons) or both were detected. See Table 1 for complete list of locations. (C) Schematic representation of the deepest macro-contacts and the three tetrodes and example LFP traces (broadband) from the three tetrodes of a hybrid electrode targeting the right anterior hippocampus (Subject 8). The IED (positive deflection) is associated with an FR. Note that both IED and FR amplitude are higher on the third tetrode. Black arrows indicate action potentials. (D) Left, Same signals as in C filtered in the FR frequency band (200–600 Hz). Note that FRs have the same morphological features on the four micro-wires of each tetrode. Right, Zoomed trace of the first micro-wire of each tetrode. Although FRs occur at the same time, moment-to-moment phase difference varies. (E) Subject’s upper body movement (see ‘Materials and methods’ section) and occurrence times of FRs on three hybrid electrodes during a 1-h long recording. (F) Top, Temporal zoom of the traces in E (delimited by vertical dotted lines). Bottom, Two video frames extracted at times indicated by the orange and purple arrows in the top panel. Note the markers on the head, shoulders and hands. Examples of micro-wire recordings from the three depth electrodes showing FRs, centred around the time of video frame, are shown below (same colour ticks depicting FR times). Scale bar = 100 ms. (G) FR occurrence rate during stillness and movement for all three subjects with video tracking. Horizontal bars indicate median values.