Amh, S. 5: SD is an "all-or-none" type process and propagates in the manner of a wave through gray matter.
Somjen 2001, S. 1066: At the core of SD is a rapid and nearly complete depolarization of a sizable population of brain cells with massive redistribution of ions between intracellular and extracellular compartments, which evolves as a regenerative, “all-or-none” type process and propagates in the manner of a wave through gray matter.
S. 8f: Processes similar to spreading depression [...] => Granz 2009, S. 8 (mit dem bekannten chronolog. Problem)
S. 13-15 => Granz, S. 16 (dto.)
Googling "Direct alterations of electrical activity" leads to GB. An earlier edition of this book might be the source (page 8 of the dissertation).