A link on the same page as URL above, http://news.yahoo.com/s/hsn/20090505/hl_hsn/earlyalzheimershindersbrainsefforttosortinformation describes one of the problems that I noticed, the inability to determine relative importance. "The mail came", "the house is on fire" and "the dog wants to come in" all had the same wieght in DW's mind. That's why we get sucked into the tunnel. We cannot expect a reasonable response to anything. It was like holding your breath for as long as you can, then take a breath, then hold it again, looping forever. It turns out that forever is not as long as one might think.
""The mail came", "the house is on fire" and "the dog wants to come in" all had the same weight in DW's mind."
Yes, that would explain the exhaustion, the need to be constantly on guard, the inability to leave them alone, and there you have the pathway into the tunnel.