Figure 1

Graphs representing the entropy of the number of pairwise configurations of signals in epileptic patients during conscious (baseline) and unconscious (generalized seizure) states. Derived from MEG recordings in a patient with primary generalized epilepsy, (a) shows entropy associated with a normal alert period (baseline, Base) and a generalized absence seizure (Sz), estimated from synchrony values at two central frequencies (defined in Methods) of 5 and 12 Hz. The continuous curves, in this and other graphs here and in Fig. 2, are obtained from the equation shown in Methods, S = N ln ( N / N – p ) − p ln ( p / N − p ) , and represent the possible entropy values of all possible numbers of pairwise combinations, yielding an inverted U . Note that here as well as in all generalized seizures analyzed, the entropy values associated with alert, baseline conditions were closer to the maximum (top of the curve) than those associated with the seizures. (b) Entropy values of two seizures and their corresponding baseline (Base) activity (computed using a time period of 30–40 min before the ictus) in a patient with secondary (symptomatic) generalized epilepsy (MEG recordings). (c), derived from iEEG recordings in a patient with temporal lobe epilepsy, shows the entropy during the alert state (Baseline), during the initial 10 s of the seizure when the patient was still responsive and alert (10 s Sz), and during the rest of the seizure when it became generalized and the patient was unresponsive (Sz). Note that when the ictus has not yet generalized, the entropy is similar to that of normal alertness. (d), another example of a nongeneralized seizure in a patient with frontal lobe epilepsy (MEG recordings).