Margie, Iain does at times have trouble formulating his thoughts and does sometimes go blank in conversation. I wouldn't say that this happens any more often when under stress - I can't really see any correlation with anything external: it can happen at a quiet supper or when leisurely talking with friends. When having one of these troubling episodes, he will often start stuttering. One correspondent to this list called it "mental festination" which is the best description I can think of. I don't know if this is precisely what you were asking about, but it is what we have observed with Iain. Barb Bates