Ammonia-related changes in cerebral electrogenesis in healthy subjects and patients with cirrhosis

► Ammonia, a cause of hepatic encephalopathy, influences the electroencephalogram (EEG). ► Differential effects occur on the wake EEG, depending on baseline/peak ammonia levels. ► Chronic (patients) or acutely induced hyperammonaemia (healthy volunteers) increase EEG power. ► This occurs especially over posterior-central areas of the scalp. ► Severe 'acute on chronic' induced hyperammonaemia (patients) reduces dominant EEG frequency.