I'm not sure this counts as a career change really, because they're somewhat related.

When I wasn't offered PhD funding for insane beaurocratic reasons, I decided to give up on my career in Neuroscience research and I am currently revising for the GAMSAT exam to get into Graduate entry medical school.
I started off in Psychology, then Cognitive Neuroscience, with my heart set in research, and have published one paper in that area (for the curious: http://www.nature.com/srep/2014/141118/srep07089/full/srep07089.html).

Now I've decided that my ultimate dream is Medicine (Surgery), and I'm looking to join the ADF as a Medical Officer.

Not quite the same as Cognitive Neuroscience research. :)