Figure 6: Electrophysiological indicators of non-participating cortical territories in human seizures.

(a) Multiunit activity and (b) 2–50 Hz signal during a seizure in patient C4. Although some electrodes clearly show firing activity, this was at a low level, with no obvious spatial pattern or wave of recruitment. (c) Action potential—field potential phase plots showing that the firing phase of the units remains in the 'pre-recruitment' pattern throughout the event, at no time showing any significant phase angle preference (note different radial scales in early and late seizures). (d) The inter-electrode coherence measure shows a minimal increase from early to late seizure periods, in marked contrast to the striking increase in coherence associated with ictal invasion of the MEA territory (see Fig. 5b).