Matthew Walker on science: what the evidence says · JRE #1109
“Some parts of your brain become 30% more active than when you're awake.”
What the evidence says
Walker claimed that during REM sleep some brain regions become 30% more active than during waking. Neuroimaging studies (PET and fMRI) do show that REM sleep is a highly active brain state, with certain regions, particularly limbic and paralimbic areas such as the amygdala, anterior cingulate, and visual association cortex, showing activation levels comparable to or exceeding wakefulness, while frontal regions show relative deactivation. An NIH-published clinical reference (StatPearls) describes overall brain metabolism during REM as increasing by 'up to 20%' relative to baseline, and a separate NIH patient-education page (NHLBI) describes REM-stage brain activity as 'similar to' waking brain activity, rather than citing a 30% figure. No neuroimaging literature retrieved in this review reports a standard, widely cited 30%-more-active statistic for any brain region in REM versus waking. The claim's general direction, that some brain areas are more active in REM than in waking, is consistent with established sleep neuroscience, but the specific 30% figure appears to be an imprecise or rounded approximation rather than a number drawn from a specific study.