This paper uses social network analysis to evaluate how the formation of an interdisciplinary brain research institute affected interaction and collaboration among neuroscientists at one Canadian university. The research institute, formed in 2004, has about 100 members representing ten different departments across the university campus. We conducted a whole network survey of the members in 2010, asking them to report on their professional interactions (advice seeking, co-supervising, co-teaching, co-authorship, holding grants, and organizing conferences together) with each of the other members during the five years before and the five years since the foundation of the Institute. Whole network measures examined include density, isolates, average degree and multiplexity. We compared these measures over time. Our findings indicate that professional interactions among the neuroscientists have increased since the founding of the Institute. The main networks of collaborators are now clustered around the three organizational themes of the Institute, which were formalized in 2010. We also examined how individual-level characteristics of the scientists affected professional interaction. We show that departmental co-membership, office co-location and Institute themes are all significant predictors of interaction among neuroscientists at this university since the foundation of the Institute. Social network analysis is a useful tool for evaluating the impact of the establishment of an interdisciplinary institute on scientists' relationships.