Researchers Illuminate the Science of Split-second Decisions

Indiana Jones was the master at making good split-second decisions. Murray Close/Getty Images

You're in a temple when suddenly you notice that a boulder is barreling down toward you. In a moment, you outrun the boulder and jump out of the way. What just happened?

Well, apart from finding yourself in an Indiana Jones movie, your brain just sprang into high gear. It allowed you to recognize a threat and move you into action. If you had looked up and noticed it was a balloon drifting toward you, you would have likely continued on your way without a fuss. But in both cases, your brain had to assess a situation quickly.

Neurologists believe that the thalamus is responsible for getting your brain to concentrate on life-or-death decisions rapidly. The thalamus is nestled between the cerebral cortex and the midbrain. One of its jobs is to take in the information we encounter through our senses and send it to the cerebral cortex for processing. With these life-or-death moments, it does that very quickly through what neurologists call “bursting.”

Bursting describes a process in which cells in the thalamus all start firing simultaneously in order to alert the cortex that something hinky is going down. It's sort of like getting a crowd of people to shout at someone to warn them of an oncoming disaster. Once the moment has passed, the thalamus goes back to normal operations.

The bursting is necessary in the first place because the cortex is constantly at work on higher-level activity. The interruption caused by the burst prompts the cortex to analyze data with a high priority so that you can recognize that object coming toward you is a boulder and not a balloon.

Recently, a Georgia Tech grad student named Clarissa Whitmire used optogenetics to manipulate the bursting activity of the thalamus in test rats. Optogenetics involves introducing light-sensitive proteins into neural cells. Then, fiber-optic wires are surgically implanted into the brains of test animals. By firing light at the appropriate cells, scientists can change how those cells behave.

Whitmire was able to not only turn off or on the bursting activity, she could also dial the activity in like a dimmer switch. What she learns may help us gain a deeper understanding of the relationship between the external world and our brains, not to mention how our senses affect our gray matter.

So the next time you see that there's a boulder rolling toward you, move out of the way. But afterward, consider how amazing it is that your thalamus just gave your cortex a shout.

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