Figure 1: Failure of propagation of full ictal events in mouse brain slices.

(a) Five successive ictal events (shown left to right) recorded in two layer 5 pyramidal cells (PCs) 600 μm apart. Only in the last three events, does PC 1 make the transition from inhibitory to excitatory barrages, which is indicative of being incorporated into the ictal event. A very important point arising from a previous study¹⁰ is that the upward deflections are not purely inhibitory, merely predominantly so. The level of inhibition simply occludes the very large concurrent excitatory drive at this time, which can be seen instead if the cell is clamped close to the GABAergic reversal potential. (b–f) Another example of δ-frequency, interictal-like activity, with concurrent low magnification Ca²⁺ network imaging. The more extended field of view allows us to visualize the failure of propagation, as the view incorporates territories that are recruited to the ictal event and other regions that resist recruitment. (b) Schematic showing the field of view in the brain slice. (c) Field of view; the two electrodes are visible, located in layer 5. (d) Eight minute recording showing two full ictal events, the first of which is only manifest as δ-frequency interictal activity in electrode 2. (e,f) Detailed views of the two ictal events, showing the time period of two Ca²⁺ network imaging movies (Supplementary Movies 1 and 2).