Being awake and being asleep are two fundamentally different states of consciousness. Neuroscientists have found that they correspond to two different patterns of activity in the brain. One way that researchers can monitor the human brain safely, without surgery, is to attach electrodes to a person’s scalp and monitor the electrical signals that leak out through the skull from the brain. This technique is called electroencephalography, or EEG. In the brain, billions of nerve cells exchange electrochemical signals across trillions of connections. EEGs provide a crude but usable window into this activity.
It has shown that, in the human brain, sleep involves slow rhythmical waves of electrical activity on a timescale as long as ten seconds. Wakefulness has been found to involve more complicated wave patterns on somewhat shorter timescales.
In 2025 a team of American researchers reported their surprising finding that sleep and wakefulness involve sorts of distinctive flickering EEG wave patterns operating on much shorter timescales than those previously known.
The researchers made their discovery by attaching sophisticated lightweight EEG headsets to the heads of mice. They monitored ten different brain regions with microsecond precision. Because the headsets didn’t interfere with the natural behavior of the mice, they could monitor the animals’ brains continuously for months at a time, gathering petabytes of data.
The researchers used artificial intelligence to search this vast body of data for new patterns. To their surprise, the algorithm could distinguish the sleeping from the waking brain using brain patterns lasting only milliseconds. The researchers think the recently discovered fast patterns will provide powerful insights into how sleep and wakefulness work in the brain.
A special thanks goes to Seralynne D. Vann, School of Psychology, Cardiff University, Cardiff, UK, for reviewing today's episode.
Further Reading
- Scientists find that small regions of the brain can take micro-naps while the rest of the brain is awake and vice versa | ScienceDaily
- Some brain regions sleep while others stay awake - Earth.com
- Surprising Sleep Discovery Suggests We've Been Missing The Brain's Micro-Naps : ScienceAlert
- Our brains take naps while we're awake – and wake when we're asleep
- The human brain is taking micro-naps throughout the day - The Brighter Side of News
David F. Parks et al. 2024 A non-oscillatory millisecond scale embedding of brain state provides insight into behavior, Nature Neuroscience, 27:1829-1843. https://doi.org/10.1038/s41593-024-01715-2.