I've been discussing the Tufts Study with David Mendosa and he's sent me a reply from Bernstein himself.
I'm waiting on permission to post it.
However essentially Bernstein says that all his patients improve cognitive function on low carb.
David says he too has sharpened up.
I however, locked myself and my dog out by forgetting to take my keys with me this afternoon. So I'm maybe "the exception that proves the rule."