hey jayhawk,
it's not that hard to match adult neurology, esp as a us senior. as far as gpa: i dunno as my school doesn't keep them. but things like AOA, MD/PhD, and/or publications (esp in the neurosciences) will definitely help. as you can see from mpp's post, the average board score for step 1 for matched us senior was 218 this match, which is right around the mean.
also, check out your SIGN group at your med school (if you have one, if not then start one). if you're at U K then contact Dr. Slevin, if you're at U Louisville it's Dr. Remmel.
check out these websites:
http://aan.com/students/medical/index.cfm
http://www.aneuroa.org/residents-fellows/menu.shtml
you're doing the right thing by getting to know neuro attendings at your school early on, esp by shadowing/going to clinic. that will help you in at least three ways: 1. actually see what neurologists do; 2. having the neuro attendings get to know you (just think how it will be when you ask for letters, they'll have known you for much more than just your rotation during 3rd/4th year); 3. getting a leg up and clinical correlation early so that when you hit the floors you'll be ahead of the game.
i'd also recommend studying your bum off for step 1, good scores will always help and may even get you an interview call at a few places that love to preen about how high their average board scores are for their incoming residents... (more than a few of the "top ten places").
also, see if you can't write a review or work on a research project w/ a neuro attending (esp if they've been invited to write a review, b/c then you're much more likely to get published). remember: this is not necessary to match neuro, but it won't hurt.
try to do one or two away electives early in your fourth year (neuro is early match) so that you can get at least one letter from a well-known attending at a big department.
my naive, biased, and incomplete list of centers of dementia/behavioral (i haven't started residency yet, but i am quite interested in dementia/behavioral neurology):
Wash U (excellent and prolly the premier clinical Alzheimer's research center, the ppl there are soooo nice and friendly; awesome functional imaging)
Mayo (see above, also more broad into behavioral)
UCSF (a building program and potential to be the top behavioral)
UCLA (a behavioral mecca in the US, awesome imaging)
U Penn (quite strong in Cognitive and Behavioral, great imaging)
Baylor (another mecca for Alzheimers, esp basic sci)
Partners [MGH/BWH] (behavioral and alzheimers, awesome imaging)
BIDMC (more cognitive, will be building as build funding strength)
Columbia (well regarded dementia, esp minority populations)
i dunno bout Hopkins or Emory (didn't read up on them yet)
so this is not fair, above are most of the top recognized programs in the country...
also check out:
U Mich - Ann Arbor (strong in neurodegenerative dis)
U Pittsburg (?)
U Florida
Northwestern U
Cleveland Clinic - Florida (also will prolly recruit a big name basic sci/clinical dementia researcher w/in the next year)
link to AAN website for fellowship search (note: this is not a complete list either as one can often apply to work directly w/ individual attendings):
http://aan.com/students/awards/fellowship.cfm
good luck