Very technical. The research experience I wrote on my resume was their core interest, so the interviewer asked all the technical details about my research work. The questions could be answered only if you did the research from a to z. Parameters, the reason for choosing the parameters, training data, assumptions made for the research. Reasons for using the model compared to others, etc. Other than the research experience, the interviewer asked 1. my overall experience of graduate school, 2. the courses I took and what programming experience I have with the courses, 3. Some optimization methods for NNs.