Medical Research Council - London Institute of Medical Sciences

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Wide Awake

States of consciousness detectable just from a scalp EEG

30 August 2020

Wide Awake

In the brain, neurons communicate by way of minute electrical signals, adding up to create distinctive patterns of electrical activity. Using electrodes, small metal discs placed on the scalp, we can monitor these patterns in a non-invasive way, to gain insights into the brain’s behaviour. The resulting recordings, called electroencephalograms (EEGs), can track differences in arousal, from wakefulness through the different phases of sleep, and help diagnose conditions like epilepsy. EEGs show brain activity as electrical waves of varying frequency and amplitude, or power: pictured, across a night’s sleep, higher peaks indicate higher frequency, and warmer colours greater power, with the white line representing overall changes in arousal. High frequency waves generally have lower power; recent research suggests measuring the relationship between these properties, known as spectral slope, can accurately determine patients’ level of wakefulness, a potentially valuable technique for monitoring responses to anaesthesia or patients in a coma.

Written by Emmanuelle Briolat

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