AP Photo/Remy de la Mauviniere (Remy de la Mauviniere) In his
new book, "Power Foods for the Brain" ($27), and his PBS
special, "Protect Your Memory" (debuting on public television on
Saturday; check local listings), he outlines his nutrition plan
to stave off Alzheimer's and dementia. Barnard took us shopping
to point out some smart choices. And, no, chopped liver wasn't
one of them.   Blueberries: "None of these have any
cholesterol," he says, waving at the produce display. And that's
important for the brain because clogged-up arteries translate
into reduced mental function. But he's particularly fond of this
antioxidant-rich fruit that's been shown (in a small study) to
help people with memory problems.  Broccoli: Folate sounds like
foliage, which is what it is, Barnard says. And in combination
with vitamins B6 and B12 (which he recommends taking supplements
of), it can eliminate homocysteine -- a destructive molecule
that messes with the heart and brain.  Sweet Potatoes: Wondering
how to get your B6? Thro