AAV-orexin improved the diurnal rhythm of REM sleep. Nocturnality ratios (amount of a state occurring during the dark period / total amount in 24 h) show normal patterns for wake and NREM sleep in all groups. Atx mice treated with AAV-mCherry have an excessive proportion of REM sleep in the dark period, indicated by a nocturnality ratio close to 50%, but Atx mice injected with AAV-orexin show normal proportions. *P < 0.01 compared to WT mice injected with AAV-mCherry. AAV, adeno-associated viral vector; Atx, transgenic (ataxin); NREM, nonrapid eye movement; REM, rapid eye movement; WT, wild type.