A, An individual spontaneous KC shows quasi-synchrony over frontal, central, and occipital scalp EEG channels. Overlaid channels participating in the KC are color-coded by scalp position: frontal channels in green, central in pink, and occipital in purple. There is no evidence of a systematic propagation of green frontal to purple posterior channels. The vertical black line is plotted at the time point where there is a 0 ms delay in the timing of the most negative peak of the KC in channels across the anterior to posterior axis: Fp1, Fpz, F1, Fc2, C4, Po3, and Po8. B, Almost all ECOG channels show a quasi-synchronous surface negative potential at the time of a single spontaneous KC detected at the scalp. The left plot depicts the color coded local field potentials while the right plot depicts the waveforms of this KC. Regions listed are: temporal pole (TempPole), lateral occipital (LatOc), anterior orbitofrontal (antOrbF), anterior prefrontal (antPreF), and ventral occipital (VenOc). C, Both spontaneous (black) and evoked (red) KCs in ECOG are characterized by a quasi-synchronous and widespread surface negativity. KCs were averaged over trials on the most negative peak of the KC as detected at the pictured scalp EEG electrode, C4. Waveforms are the average of 86 spontaneous (black) and 42 evoked (red) KCs. Patient is the same as in B. D, Traces of KC averages from all channels pictured in C are superimposed to demonstrate the regularity of the waveforms across sites. E, On both an average and single trial basis, spontaneous and evoked KCs show similar topographical profiles that are quasi-synchronous across the cortex. The scalp EEG electrode and ECOG channels from across the cortex (selected to be maximally far apart) are pictured for the averaged spontaneous or evoked KC, as depicted in C & D, as well as a single trial. The vertical black line indicates time zero of the most negative peak of the scalp KC on the average (left) and the single trial (right). Channel location regions listed are the same as in B.