Explore how 24 hours without sleep transforms neural activity, cognitive performance, and brain connectivity.
What actually happens when you stay awake for 24 hours straight?
We looked at real data from a neuroscience study that recorded brain activity and cognitive performance
before and after sleep deprivation using something called fNIRS
(functional near-infrared spectroscopy).
Basically, scientists tracked blood flow in the brain while people did tasks like tapping their fingers and reacting to visual prompts. They also ran detailed memory and reaction tests using a touchscreen device.
The result? Sleep-deprived brains struggle — especially in areas that control decision-making, memory, and attention.
So before you flex that all-nighter, maybe take a look at what it does to your brain.
A circle will light up randomly. Press the corresponding key (S D F J K) on your keyboard as fast as you can.
Negative values show how much worse people performed after sleep deprivation. Memory and attention suffer the most.
Play around with the toggles. See how the oxygenated (HbO) and deoxygenated (HbR) hemoglobin levels differ before and after sleep deprivation.
Your brain needs oxygen to think, move, and process information. HbO (oxygenated hemoglobin) delivers oxygen to active brain areas, while HbR (deoxygenated hemoglobin) is what’s left after that oxygen is used up.
By tracking HbO and HbR, we can observe which brain regions are more active. During tasks like finger tapping, HbO typically increases, while HbR decreases slightly or follows a mirrored pattern. This change—called a neurovascular response—signals healthy oxygen flow and brain activation.
After 24 hours without sleep, we saw a consistent increase in HbO and more erratic HbR fluctuations. In the plots, red lines (after SD) rise above blue lines (before SD), reflecting this shift.
The rise in HbO means the brain is pushing harder—it's trying to stay engaged, but with less efficiency. Meanwhile, the unstable HbR response shows that while the system is still delivering and removing blood, it’s doing so less effectively.
In simpler terms: your brain is still doing the work, but it takes more "fuel" to get the same job done. Think of it like riding a bike with a flat tire—possible, but harder, slower, and more exhausting.
In short: Higher HbO = more effort. Fluctuating HbR = reduced efficiency. These patterns reflect a tired brain working overtime just to keep up.
TL;DR: Your brain still functions after sleep loss—but it’s running on low power. These signals explain why sleep-deprived brains have trouble with focus, memory, and quick thinking. Be kind to your brain—sleep is non-negotiable.
Interactive plots showing changes in oxygenated (HbO) and deoxygenated (HbR) hemoglobin levels before and after sleep deprivation.
Blue lines = Before sleep deprivation
,Red lines = After sleep deprivation
. Hover over lines for exact values, zoom in/out, and click legend items to toggle traces.