If you're more interested in Neuroscience, do that. Me, personally, I can't decide whether I want to go to Medical School, get a Ph.D. in Biology, Math or History.
As such, I'll just major in General Biology and make a decision later.
Basically, the MCAT has four sections, Physical Science, Verbal Reasoning, Writing and Biological Sciences.
So, definitely take a few math courses, a logic course, a few English courses and Physics.
Edit: The Physical Sciences sections has questions on both physics and chemistry.