Matthew Walker
Matthew Walker is a sleep scientist at the University of California, Berkeley, and the senior author on the 2007 study that scanned people after a night without sleep and found the amygdala's response to negative images amplified, with its connection to the front of the brain reduced. It is the most cited piece of evidence for the ordinary observation that everything feels worse when you have not slept.
Who they are
Credit the first author for the study. The paper is Yoo and colleagues. Walker is the senior name on it, and it circulates under his.
What this page will and will not print. The widely quoted figure of sixty per cent greater reactivity, routinely attached to this paper, could not be confirmed against the source, and it is therefore not printed here. The qualitative finding is safe. The number is not. The study is small and of 2007 vintage, so it should be treated as suggestive rather than settled. His affiliation is recorded as it stands in the vault's verification file and was not independently searched.
Key papers
Yoo, S.-S., Gujar, N., Hu, P., Jolesz, F. A., & Walker, M. P. (2007). "The human emotional brain without sleep, a prefrontal amygdala disconnect", Current Biology, 17(20), R877 to R878. Walker is senior author. First author is Yoo.
Key ideas
The finding is easy to state and easy to overstate. After a night without sleep, the brain's alarm response to unpleasant images was larger, and its link to the regions that normally moderate that response was weaker.
No figure from this study is quoted here, because the one in circulation could not be traced to the paper. An unverifiable number is worse than no number.
A small scanning study from 2007 is a starting point, not a conclusion. It is worth citing for the direction of the effect and not for its size.
It is the mechanism most often reached for behind the experience of lying awake and finding everything worse, and the honest version of that sentence has to say "suggests" rather than "shows".
Concepts on this site
Diurnal Variation in Rumination
Sources
- Yoo, S.-S., Gujar, N., Hu, P., Jolesz, F. A., & Walker, M. P. (2007). Current Biology, 17(20), R877 to R878.
- Vault note, 2026-09-11. The sixty per cent figure could not be confirmed and is held unprinted. Affiliation as recorded in the verification file, not independently searched.