Blood exerts a powerful influence on the brain
The brain's nerve cells have a call-and-response relationship with the blood that sustains them
Blood tells a story about the body it inhabits. As it pumps through vessels, delivering nutrients and oxygen, the ruby red liquid picks up information. Hormones carried by blood can hint at how hungry a person is, or how scared, or how sleepy. Other messages in the blood can warn of heart disease or announce a pregnancy. Immune molecules can reveal an infection.
When it comes to the brain, blood also seems to be more than a traveling storyteller. In some cases, the blood may be writing the script.
A well-fed brain is crucial to survival. Blood ebbs and flows within the brain, moving into active areas in response to the brain’s demands for fuel. Now scientists have found clues that blood may have an even more direct and powerful influence. Early experiments suggest that, instead of being at the beck and call of nerve cells, blood can actually control them. This role reversal hints at an underappreciated layer of complexity — a layer that may turn out to be vital to how the brain works.
The give-and-take between brain and blood appears to change with age and with illness, researchers are finding. Just as babies aren’t born walking, their developing brain cells have to learn how to call for blood. And a range of age-related disorders, including Alzheimer’s disease, have been linked to dropped calls between blood and brain, a silence that may leave patches of brain unable to do their jobs.