Neuroscience or Psychology

I'm going to tag @bijalluhar and @PriyaDesai since they might be able to help talk about the specific differences of these majors at UCLA and I'll do what I can to provide you an answer with how these majors might differ in general.

It's going to depend on what exactly you study for psychology but in general it's the study of behavior and the mental thought processes which lead to certain behaviors. So things like thoughts, feelings, desires, etc. Neuroscience on the other hand, focuses much more on the brain itself and delves deeper into the processes the brain goes through. So you're going to be observing chemical processes going on in the brain and nervous system. There can obviously be a lot of overlap in these fields but neuroscience is going to more biology and hard science based compared to psych (in my opinion).

Have you looked into UCLA's psychobiology major? It might be something that interests you. Since you need a medical degree to be a psychiatrist I would recommend neuroscience or for you to look into the psychobiology major since I think you will feel more prepared. Psychology also works but you'd need to make sure you're also taking pre-reqs for med school like biology, chemistry, physics, math, etc.