FMR1 and fragile X syndrome: We tested the hypothesis that the absence of FMRP has different effects on the function of a single type of ion channel in PFC, a brain region containing a heterogeneous neuron population and that is implicated in behavioral deficits associated with FXS (Menon et al., 2004; Krueger et al., 2011; Wang et al., 2012; Dembrow and Johnston, 2014).