ARID1B and Hydrocephalus: The rates in this study were based on mice that had severe hydrocephaly and thus were excluded from the behavioural outcomes; however, as described in more detail below, it should be noted that the ventricular system as a whole was enlarged in Arid1b+/− mice throughout development (q = 0.005), particularly the lateral ventricles (q = 2.0 × 10−12).