As an MD/PhD, now an intern but looking towards a future in clinical research, I would say that if you are interested in neuroscience research (and not in seeing patients) I would focus on getting a PhD.
If you are interested in seeing patients, then you can do an MD with some research electives, an MD with a research track (usually a 5 year program), or an MD/PhD, but I have a sour taste for the whole MD/PhD thing. That is a subject for its own thread. Crescend, I hope it doesn’t leave you with the same.
BTW Qadgop, the Hopkins MD/PhDs that I work with almost uniformly took 8 years to finish. Better than my 9, but hey. 6 year MD/PhDs are very few and very far between nowadays.
The people who entered medical school late that I know have had one of two things happen to them: a) they were engineers/lawyers/teachers/nurses who were not happy and had a clear vision of where they wanted to go. b) they had life changing, powerful experiences which gave them a clear vision of where they wanted to go.
Note the similarity between the two. The path to medical school is hard. Big choke points on the biology classes and the organic chem. More choke points on the MCATs. The weed out a huge percentage of It doesn’t get easier once you get in. Luckily, med schools are pretty good at selecting those who are going to get through, and there is around a 90% graduation rate once you get started. But that only buys you at least 3 years of residency, which is just as much of a bitch. I know this as well as anyone on the planet right now (q3 in the Hopkins CCU, carrying the code pager, etc. living the dream, baby).
Grad school, OTOH, while not without its stresses, is a lot easier to get into (especially for US citizens), although probably harder to get out of and harder to land an academic (or high paying job) once you do.
With all honesty, a 25 year old unemployed bartender who seems to be have a very tenuous grasp on the whole educational system has quite a way to go before that clear vision thing. It is like an asthmatic double amputee posting “I want to climb Everest without supplemental oxygen. How do I do that?” Although becoming an MD, a PhD, or an MD/PhD requires probably more overall effort and tenacity.
My advice. Start college, any accredited program will do. Do what you think is interesting but take lots of bio, psychology, and neuroscience classes. Find a mentor that you can research with. Volunteer some time in your local hospitals. Get back to us when you are a sophomore and still sticking with it when you have formulated a clear vision.