<p>So, I choose biochemistry to help prep myself for med school. My true passion is neuroscience; I hope to be a neuroscientist. Should my essay be about why I like biochemistry, or why I like neuroscience? Can I talk about both?</p>
Certainly colleges would enjoy seeing passion, so I would make neuroscience the main topic. You’ll also want to describe why you’re studying biochemistry instead of neuroscience - whatever you think will give Columbia the “most complete view of you as an applicant.” These questions are ways to help you expand on stuff that’s meaningful to you. Just make sure they know the reasoning you used when you ticked off “biochemistry” on your application!