Well I spent ££££s on Omega 3 and a host of other pills that were supposed to help memory and brain function..
But do you not what helped?
Stopping myself from living inside my own head (e.g. trying to focus inwardly on how I was feeling constantly) actively trying to stop myself focusing on health related anxiety issues, a good restful nights sleep.. Doing things I enjoy and trying to focus on the outside world and other people abit more. Along with walking, exercise, leafy green veg and restrictions on junk food, coffee and booze. helped This helped me more a heck of alot more than a fish oil pill ever did.
With illness like diabetes I personally think it is very easy to become too inwardly focused on how we are feeling (i know it is necessary at times), I think this in turn can spill over into anxiety and stress and a cycle of obsessive thoughts can begin quite easily.
As people have said, the human body is amazing, I very much doubt that an A1c in the 11 would cause lasting brain damage in the short term, although logic suggests that as the brain runs likes to use glucose as its primary fuel, you would be wise to start working on lowering your HbA1c and focus on achieving more stable blood sugars. I know that severe blood sugar swings cost me two personal relationships, due to volatility and mood swings.
I would bet my motorbike that stress and anxiety have come into play here.. Focus on relaxing and looking after yourself. I am one of the least hippy men you can imagine, but these issues had me switching from Whiskey to Camille tea and from rock and roll, to mindful mediation sessions ha.