I will speak to UMD as it’s a very popular school in my area. I don’t know much about GMU personally so I’ll defer to others.
UMD has a very strong CS program (it’s ranked in the top 20). It’s rigorous and provides a wide range of opportunities. Their neuro program is also very strong and the two students I know there who are neuro majors speak highly of their experience.
I believe double majoring in these two fields will be hard as they are both demanding majors. But that’s your call.