Nocturnal Arousals: Stirred, Not Shaken: A consideration of the EEG and sleep

Where are ‘we’ when we sleep? Does any part of us remains cognizant of the external environment in which our body rests? The closest we can come to approaching this quasi-psychophilosophical enigma is through monitoring the neuro-electrical activity of our brains during this time. This activity is categorized into high-amplitude and low-amplitude frequency waves visible on the electroencephalogram (EEG). This paper reviews the evolution of the EEG as it is has been utilized to inform our knowledge of the stages of, and transient emergences from, sleep. There is discussion distinguishing sleep from other semi/unconscious states such as anaesthesia or coma while the primary focus is on the detection, aetiology and purpose of ‘arousals’ – both cortical and somatic – and where these feature in the Cyclic Alternating Pattern of normal and disordered sleep. The sequelae of aberrant arousals is also considered in relation to daytime hypersomnolence and apneas with a reiteration of the importance of combining academic tools with clinical practice.