EEG, EOG and EMG electrodes were checked, and electrodes reapplied to achieve impedances below 5 kΩ. Respiratory signals included a nasal pressure cannula and oronasal thermister, thoracoabdominal bands to assess chest and abdominal movement, and finger pulse oximetry to determine arterial blood oxygen (O2) saturation.

All measurements were continuously recorded from lights-out (approximately 22:30 h) until the end of the study the following morning (approximately 06:00 h). Sleep and respiratory signals were analysed by Cabozantinib price an accredited sleep technician, blinded to group allocation, and according to current internationally agreed standards (Iber et al., 2007). AHI was determined using American Academy of Sleep Medicine ‘alternative’ criteria (Iber et al., 2007; Ruehland et al., 2009). Within these criteria, respiratory events are scored as an apnoea following complete cessation of airflow for Roxadustat research buy ≥ 10 s, whereas hypopnoeas are scored based on a 50% reduction in airflow with an associated 3% reduction in O2-saturation, or an arousal from sleep (Iber et al., 2007). An AHI of < 10 events/h was used to rule out OSA. The arousal index (AI; number of arousals per hour of sleep) was calculated to produce an index of sleep fragmentation, and sleep efficiency was obtained by dividing the amount of time spent

asleep by the total amount of time available for sleep (i.e. the lights-out duration). On a separate day, subjects not attended the University of Adelaide for neurophysiological testing. This session took place in the afternoon or evening to avoid time of day effects (Sale et al., 2007). During testing, subjects were seated in a comfortable chair with their right forearm resting on a padded arm-rest and right hand in a pronated position. Surface EMG was recorded from the first dorsal interosseous (FDI) and abductor digiti minimi muscles of the right hand. Two Ag–AgCl electrodes arranged in a belly-tendon montage were used. EMG signals were amplified (1000 ×), filtered (20 Hz–1 kHz), digitised at 2 kHz using a CED1401 interface (Cambridge Electronic

Design, Cambridge, UK) and stored offline for analysis. TMS was applied to the left primary motor cortex using a figure-of-eight coil (external wing diameter 9 cm) with two Magstim 200 magnetic stimulators connected through a Bistim unit (Magstim, Dyfed, UK). The coil was held tangentially to the scalp at an angle of 45° to the sagittal plane with the handle pointed backwards, producing a current flow in the brain with a posterior to anterior direction. The coil was positioned on the scalp over the location producing an optimum response in the relaxed FDI muscle. This location was marked on the scalp for future reference and continually checked throughout the experiment. Stimuli were delivered at a rate of 0.