I am now 15 months out and this aspect of the injury has not really improved much at all for me. I HATE it.

I completely understand what you guys are going through, and it is one of the most unsettling aspects of this whole thing. It reminds me of the old axiom "I think, therefor I am."

Well the sad fact now confronts me that because my thinker is diminished, my existence itself is diminished in that I feel less present, almost as though I exist less. The crispness of reality that I once took for granted seems gone for now. Reality is less sharp, less vivid, less convincing.

It is very similar to the effect of taking dissociative drugs. So I hypothesize that this aspect of the injury may be due to a reduction of glutamate neurotransmission, reflecting white matter damage in particular. This is based on my experience taking these drugs in the past where the same sort of feeling has occurred, but of course always resolving spontaneously. TBIs sadly do not.