Hi ThisType,
Interesting information.
I don't have speech problems while in POIS, and have no memory or cognitive problems neither - I have very severe emotional symptoms, akin to a personality change ( I am a kind a werewolf....) , and have also fatigue and hypotension.
However, you mention rehydration with electrolytes solution as helping, For me, I have been using magnesium, potassium, and also salt (sodium chloride) to help me with POIS. Those electrolytes has been helpful against hypotension and fatigue. ( I still take magnesium and potassium in my pre-pack, along with many other things, and this pre-pack still helps me a lot after over 2 years).
I do not know what may be the link between what you have as relief with an electrolytes solution, and what I get as relief from electrolytes supplements, though.