Figure 2

CCEP components. (a) Components of CCEPs are consistent, regardless of signal processing method (i.e. averaging/ low pass filtering), both on ECoG and LME recordings. (b) Single-trial example (Pt7) of early components triggered from the vicinity of LME (Gr21-22) and of middle and late components triggered from more distant contacts (Gr13-14). (c) Laminar profile of CCEPs illustrated by the recordings of Pt1 (averaged across trials of a single stimulation site), aligned to stimulation: LFP data (c/1), CSD (c/2), MUA (c/3), TFR over 0–200 Hz (calculated for each channel, plotted on top of each other; c/4). (c/1) and (c/2) bottom row: zoomed in to make early components more visible. Note that zoomed-in figures are unfiltered (only notch filter is applied to remove power noise) to make P1 component visible, while those in the top row are filtered with 20 Hz (48 dB). White and black curves mark the activity on the max-amplitude channel. The early components consist of a surface positivity with lower-middle layer sink (P1) and surface negativity with superficial sink (N1), accompanied by elevated MUA. The middle components consist of surface positivity (P2) with superficial source and surface negativity (N2) with wide middle layer source, accompanied by marked decrease in MUA. P3 is characterised by surface positivity with middle layer sink and upper-middle layer increase in MUA. The spectral power shows increase during early and late components and decrease during P2 and N2. (d) Peak latencies of LFP components (n = 7): pooled over all LME channels (mean, median, 1st and 3rd quartiles; d/1); across LME channels with no significant depth-dependent change (d/2). Considering the total number of detected components, N2 is evoked at the highest rate (n = 7, d/3). Although statistically non-significant, N1 and P2 components tend to be evoked in middle-, while N2 and P3 in supragranular layers (n = 4, d/4). The appearance of components is distance-dependent: N1 and P2 are most likely evoked within 1 cm from LME, P3 rather from a distance and N2 both up close and from further away (n = 7, d/5). There are no significant differences between stimulation from SOZ vs. non-SOZ, regarding appearance of components, though there is a tendency that N1 and P2 can be better evoked from SOZ (n = 7, d/6) (see “Results” for details of statistics).