Fig. 5.

Anteroposterior and dorsoventral propagation of reconstructed SWD-related impedance changes. Coronal slices were obtained for six time points from −4 to 16 ms, with respect to the peak EEG amplitude of the ictal SWD, at five distances in the anterioposterior direction relative to bregma: −1.0, −2.0, −3.0, −4.0 and − 5.0 mm. Slices obtained at −2.0 and − 4.0 mm transect the central portion of two distinct regions of maximal δσ. Movement of fast electrical activity in the posterior direction can be observed as the maximal δσ in anterior slices (−1.0 and − 2.0 mm) is achieved at an earlier time point (4 ms) compared to the three more posterior slices (−3.0, −4.0 and − 5.0 mm), in which the largest volume of cortical tissue is activated at 8 ms. Simultaneously, a general shift of δσ in the dorsovental direction can be observed over time: whereas early activity is concentrated in the superficial half of the cortex, the ensuing time period sees its gradual propagation to deeper cortical tissue. δσ represents t-score of conductivity changes. GM, grey matter; WM, white matter.