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Dr. Universe

Determining brain death


Dr. Universe:

What does it mean to go brain dead?

Noelle, 10, Sumner, Wash.


Dear Noelle,

Let’s say we wanted to find out what kind of electrical activity was happening inside your brain at this very moment. Yep, you read that right: Your brain is full of electricity. It actually generates enough electricity to power a lightbulb.

In fact, the tiny cells in your body use electricity to send messages to each other. That’s part of what helps the brain and body communicate. I decided to visit my friend Samantha Gizerian, a neuroscientist at Washington State University, to find out more about our brains.

She said if we wanted to observe activity in a human brain, we could do a test called an electroencephalogram (uh-lek-trow-uhn-seh-ful-luh-gram), or EEG for short. We’d attach some small discs with thin wires, or electrodes, to a person’s head.

Then we could watch as a computer translated that brain activity into spikes and dips on a screen. Scientists can look for patterns on the screen to learn more about our active brains. But we also can use this test to help us find out if someone is “brain dead.”

Perhaps you’ve heard a person say that they were feeling “brain dead” if they made a mistake or maybe forgot to do something. But when someone is actually “brain dead” it means that the electrical connections between cells have stopped working altogether. We wouldn’t see any spikes and dips from the EEG on the computer screen.

That’s a lot different from a coma. A person in a coma is alive, but unable to respond to or interact with the environment around them. Brain death usually happens when the brain stem at the bottom of the brain dies. If the brain stem isn’t functioning anymore, a person can’t survive.

Along with EEG tests, doctors also will test patients’ reflexes to see if they respond to pain, if their pupils move when doctors shine light on their eyes, or if their heart rate and body temperature start to drop when they remove some of the technology that helps keep the lungs breathing or the heart beating.

The reason they do all these tests is because any one of these functions, on its own, could still happen when the patient is alive, she said.

Gizerian said these tests are really important for making sure people follow medical laws, too. When doctors first started doing surgeries to take out people’s organs for transplants, they wanted to make certain a person’s brain was no longer working. It turns out the term “brain dead” actually has more to do with laws than anatomy.

When someone dies, the organs in their body can sometimes still help other people who need an organ survive. A lot of organs have been transplanted over the years — hearts, liver, lungs, kidneys. But we’ve still yet to learn how to transplant the brain.

In fact, there’s still quite a lot we don’t know about the brain. Who knows, maybe one day you will use your own brain to investigate all kinds of questions about that three-pound organ between our ears.


Dr. Universe


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