Figure 5. Voltage changes in SWDs and myoclonic seizures.

Panel A shows EEG samples from spontaneous SWDs (spikes 1-4, N = 33) and PTZ-evoked myoclonic seizures (spikes 1 and 2, N = 23). The EEG channels from the left anterior motor cortex (aM1, blue), posterior motor cortex (pM1, green), and somatosensory cortex (S1, red) are overlaid to demonstrate the similarities in spike duration and the differences in voltage. The plots in panel B depict the mean voltages (± 5-95% CI) from SWD spikes 1-4 and from myoclonic seizure spikes 1-2 in the left and right hemispheres. Graph bars are colored in sections corresponding to the voltages in aM1 (blue), pM1 (green), and S1 (red). A two-factor ANOVA compared the effects of spike (SWD spike 1-4 and myoclonic spikes 1-2) and brain region (aM1, pM1, S1) on voltage. Although there was no significant interaction between spike type with brain region on voltage (P ≥ 0.177), there were large independent effects (P < 0.001). In both hemispheres, myoclonic seizure spike 2 had higher voltage than SWD spikes 1-4 and myoclonic seizure spike 1 (P < 0.001). Myoclonic spike 1 also had greater voltage than the first two SWD spikes (P < 0.004) and, on the right, had greater voltage than the third and fourth SWD spike (P ≤ 0.011). SWD spike 1 had significantly lower voltage than spike 3 or 4 (P ≤ 0.007). For both SWD and myoclonic seizure spikes, the voltage in aM1 was significantly greater than that in pM1 or S1 (P ≤ 0.005). Panel C depicts the median voltage ratio between aM1 and S1 (top) and between pM1 and S1 (bottom). The ratio between pM1 and S1 was greater in myoclonic spike 2 than the first two SWD spikes in both hemispheres and the ratio between aM1 and S1 was greater in myoclonic spikes 1 and 2 than the first two SWD spikes on the left. Differences in the aM1 to S1 voltage ratios between the myoclonic and SWD seizure spikes on the right were not statistically significant (# P = 0.081).