C9orf72 and amyotrophic lateral sclerosis: Notably, this dynamic time-dependent switch from hyper- to hypoactivity in MN cultures from ALS patients has been well described by Devlin and colleagues, who monitored the electrophysiological changes occurring over time in C9orf72- and TARDBP-mutant MN and described a progressive loss of excitability in mutant cultures (Devlin et al., 2015).