Finding Brain Circuits Tied to Alertness

Everybody knows that it’s important to stay alert behind the wheel or while out walking on the bike path. But our ability to react appropriately to sudden dangers is influenced by whether we feel momentarily tired, distracted, or anxious. How is it that the brain can transition through such different states of consciousness while performing the same routine task, even as its basic structure and internal wiring remain unchanged?

A team of NIH-funded researchers may have found an important clue in zebrafish, a popular organism for studying how the brain works. Using a powerful new method that allowed them to find and track brain circuits tied to alertness, the researchers discovered that this mental state doesn’t work like an on/off switch. Rather, alertness involves several distinct brain circuits working together to bring the brain to attention. As shown in the video above that was taken at cellular resolution, different types of neurons (green) secrete different kinds of chemical messengers across the zebrafish brain to affect the transition to alertness. The messengers shown are: serotonin (red), acetylcholine (blue-green), and dopamine and norepinephrine (yellow).

What’s also fascinating is the researchers found that many of the same neuronal cell types and brain circuits are essential to alertness in zebrafish and mice, despite the two organisms being only distantly related. That suggests these circuits are conserved through evolution as an early fight-or-flight survival behavior essential to life, and they are therefore likely to be important for controlling alertness in people too. If correct, it would tell us where to look in the brain to learn about alertness not only while doing routine stuff but possibly for understanding dysfunctional brain states, ranging from depression to post-traumatic stress disorder (PTSD).

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Creative Minds: Meet a Theoretical Neuroscientist

Sean Escola

Sean Escola

Most neuroscientists make their discoveries in a traditional laboratory or clinical setting. Sean Escola, a theoretical neuroscientist at Columbia University in New York, just needs a powerful computer and, judging from his photo, a good whiteboard.

Using data that he and his colleagues have recorded from living brain cells, called neurons, Escola crunches numbers to develop rigorous statistical models that simulate the activity of neuronal circuits within the brain. He hopes his models will help to build a new neuroscience that brings into sharper focus how the brain’s biocircuitry lights up to generate sensations and thoughts—and how it misfires in various neurological disorders, particularly in mental illnesses.

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