Hey, I felt that WUSTL neuroscience group is really nice overall.. I got my interview schedule on wednesday (last week) and so, I'm expecting that you'll get yours this wednesday.
None of the interviewers expect you to be thorough with their line of research. As long as you are comfortable explaining your past research experiences and career goals, it was totally fine.
From what I understand, they have around 25 people during each of their interview weekends and I'm assuming that they will send offers to around 30 of the 50 people. The class size is around 13-15. I was also told that they do not send offers/rejections to anyone from the first interview weekend, till they are done with the second set of people as well. So, yeah, all of us who interviewed during the first weekend do not hold any kind of advantage over you guys .