A near extinction. Spreading depolarization is a slowly propagating wave of cortical depression occuring during strokes, cerebral hemorrhages, epilepsy or migraines. It was assumed that during such episode the shutdown of activity was general. Here the authors describe a more complex aethiology characterized by a myriad of profiles in the vertical propagation to deep cortical layers and, in relation to these, either a depressed, spared or even enhanced activity observed at the surface.      (IB)

The authors: Azat Nasretdinov, Daria Vinokurova, Coline Lemale, Gulshat Burkhanova-Zakirova, Ksenia Chernova, Julia Makarova, Oscar Herreras, Jens Dreier & Roustem Khazipov

Scientific abstract: Spreading depolarizations (SDs) are classically thought to be associated with spreading depression of cortical activity. Here, we found that SDs in patients with subarachnoid hemorrhage produce variable, ranging from depression to booming, changes in electrocorticographic activity, especially in the delta frequency band. In rats, depression of activity was characteristic of high-potassium-induced full SDs, whereas partial superficial SDs caused either little change or a boom of activity at the cortical vertex, supported by volume conduction of signals from spared delta generators in the deep cortical layers. Partial SDs also caused moderate neuronal depolarization and sustained excitation, organized in gamma oscillations in a narrow sub-SD zone. Thus, our study challenges the concept of homology between spreading depolarization and spreading depression by showing that SDs produce variable, from depression to booming, changes in activity at the cortical surface and in different cortical layers depending on the depth of SD penetration.

published in Nature Communications, 2023

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