PAK1 and brain disorder: Since all the animal models of brain disorders that are functionally rescued by manipulations of PAK1 share a common deficit in E/I balance (Braat and Kooy, 2015; Dolan et al., 2013; Eichler and Meier, 2008; Gao and Penzes, 2015; Hayashi et al., 2007; Kehrer et al., 2008; Lewis et al., 2005; Marín, 2012; Molosh et al., 2014; Yizhar et al., 2011), we therefore examined whether disrupting PAK1 would affect the E/I ratio by performing whole cell patch-clamp recordings in CA1 pyramidal neurons of hippocampal slices acutely prepared from PAK1 KO mice and their WT littermates (Figure 1a).