There are research residencies available in every specialty. In the brain this could mean anything from Neurology, Psychiatry, ENT, Neurosurgery, Radiology, Ophthamology, and more...
Hey, thanks everyone for all of the responses. Just to clarify something for me (not related to the original question really), but do you still do a post-doctoral fellowship after you complete your medical residency and fellowship? I'm still a bit confused on this.
It is much more common for a MD or MD/PhD trained researcher to remain a fellow for some period of time. Many fellowships have 1 year of research time, but you can elect to do more depending on the funding situation, job market, and career goals. There are only a few differences between a post-doc and research fellowship, which leads to the confusion between them. Fellows typically have some amount of clinical duty. The notion of "post-doc" typically implies 100% research. Those early in their careers nowadays are typically uncomfortable moving to 100% research because of the uncertain job market within research. By keeping your fellowship 80% research and 20% clinical or so, you retain the flexibility to go 100% clinical if necessary. Also, fellowships pay around $10k more than post-docs with the same amount of post-graduate training.
Also, I see that there are some Forensic Pathologists who are MD/PhD and do research attached to hospital/universities or have faculty positions. How does this work if they are employed by the government? Do they just have two different jobs/employers? Thanks!
You can have multiple academic appointments. This is negotiated between the faculty and the numerous employers. The structure of how you get paid and by whom and how much each demands of you and what each gives you... It's all very flexible. In the case of the medical examiner, they may get paid some salary by the government for doing autopsies and then receive money from grants and receive lab space from an academic institution.
Do you think attending medical school for 4 years will help your research, or make you a better scientist?
Will it help you get hired? Definitely. Will it make you a better scientist? It depends on the science you do. Do I
think attending medical school will help my research? Of course, or I wouldn't have done it

This is a question with only subjective answers. Keep that in mind when evaluating responses. One way to get
objective on this point would be to look at success rates in applying for grants between MD/PhDs and PhDs. I will likely have to dig out this data, but if I recall the rates are the same between the two groups, only PhDs get their first grants at an earlier age.
few weeks ago I sat down with an md/phd dropout (phd only) with a professorship at a top 5 medical school who said that md/phd is a huge waste of time because you can learn all the medical/human bio yourself.
You also have to keep in mind in this discussion that things are changing with the times. As funding gets harder to get, fewer students are going straight to post-doc and the idea of dropping out to PhD, while rare to begin with, has gotten even rarer. It was much easier to get a career going in research during the boom years of the 90s. In my opinion, the career uncertainty now combined with the increased demands for faculty to get research grants and research-based positions explains the shift. This is in part as well because most hospitals are losing money by practicing medicine, and this trend into the red is increasing with time. Thus all faculty are expected to generate the revenue required to keep things afloat, whereas more resources were available in past times to keep non-practicing researchers going or to get them started.
Someone who didn't like medical school now may hang in there and do Radiology or Pathology where maybe they wouldn't in the past. Someone who may have had a career in research decides the increasing demands are not worth it, and goes 100% clinical. All the data I've seen indicates there's an increasing trend towards clinical work for MD/PhDs, and my guess is this will continue until funding gets better or there's a better emphasis on making research careers attractive.
Thus, I say take any well-established professor's advice with a grain of salt. Many, though of course not all, started their careers in more bountiful times. Now you can of course be an idealist, an optimist, or just plain arrogant and say "I AM THE BADDEST MOFO ON THE PLANET!" and you might be right, lucky, or work hard enough to be successful regardless. The decision you make on how to train now all depends on how optimistic/idealistic vs. pragmatic you are.
In other words, you may identify with: "When push comes to shove you have to do what you love. Even if it's not a good idea." or you might think it's incredibly naive. It's up to you. sluox obviously thinks a PhD isn't a good idea these days. Do you believe him? Should you do it anyways? Only you can answer that.
Of course, this doesn't apply to many (most?) graduate students who didn't give any of this serious thought and just floated their way into grad school not knowing what else to do with life. But, I think since we are discussing this topic, it's worth it to give the full story.
I get it, that's a popular opinion, but I have yet to be convinced that it's SUCH a terrible existence. The PhD's I know seem happy. Yes, there's frustrations, but there are in every job imaginable.
Also remember that you are speaking to a very select group of PhDs. Most MD/PhDs do mostly clinical. You won't meet them when you interview for MD/PhD programs. Unless you try hard to seek them out, you won't meet the 15% or so who went to private practice. You won't meet half of the MD/PhDs at big name academic center who do 80-100% clinical or administrative work and almost no research. In academia, you won't meet the vast majority of PhDs who found the obstacles to a research career too great or found it unappealing and went off and did something else. Those advisors would likely have different advice for you. Always keep in mind who you're talking to in this business, how they chose to do their career, what their own goals are (i.e. MD/PhD program = produce researchers), any objective criteria you can, and your own goals.
Personally, the flexibility inherent in MD/PhD always strongly attracted me to do the combined degree program, and just because I'm almost done doesn't mean I have any clue how I'm going to use it

. With the long training pathways and the very defocused undergraduate programs, I'm not sure how anyone can really know what they're going to enjoy doing at 35 when they're 22. But that's another issue for another time.
(Unless the PhD is @ Harvard, and the MD/PhD is at podunk...or something like that.)
I don't think this is true at all. I still think the MD/PhD is going to have a much easier time getting a job. The MD/PhD will still likely get a top residency in the typical research fields as long as they do well in medical school. As far as a research career goes, both will probably get the same post-doc, as it seems that all fields are like mine in that it's almost impossible to find American post-docs. Nobody wants to do one because it feels like a long trap with no job on the other side. So labs are either stuck picking between those who are unqualified, those who can't speak English, or just not having post-docs. Those qualified who are stalwart enough to stick it out go to the top labs, but it's hardly competitive.
Well, yes, but PhD's at Harvard are supposed to be brutal black holes where you're dumped for 4-5 years and then spend the next 2-3 years crawling back out to the light.
How is this any different from any other successful grad student

You may think I'm joking, but I'm not.