States of consciousness detectable just from a scalp EEG
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.
BPoD stands for Biomedical Picture of the Day. Managed by the MRC London Institute of Medical Sciences the website aims to engage everyone, young and old, in the wonders of biomedicine. Images are kindly provided for inclusion on this website through the generosity of scientists across the globe.
BPoD is also available in Catalan at www.bpod.cat with translations by the University of Valencia.