The brain's nerve cells have a call-and-response relationship with the blood that sustains them
Ralph Hutchings/Visuals Unlimited, Inc.
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