Just to chime in a bit late, but I stopped Cogentin for exactly that reason. It started to really beat up on my memory and cognitive ability. I was already in a bit of a whole because my kidney damage had caused me to score a "Mild Cognitive Impairment" diagnosis with the neurologist. Cogentin was not playing nicely with me given the circumstance.

B6 seems to be helping still, not complete relief, but it seems to be keeping the worst of it at bay. Maybe playing with my AP/AD combo would be better, but they work so well without being overpowering, I'd hate to have to start all over.