"Brain" in Dish Flies Simulated Fighter Jet
for National Geographic News
November 19, 2004
Scientists have grown a living "brain" that sits inside a petri dish and can fly a simulated F-22 fighter aircraft.
The brainchild of Thomas DeMarse, a biomedical engineer at the University of Florida in Gainesville, the "brain in a dish" is a collection of 25,000 neurons taken from the brain of a rat that are connected to a computer via 60 electrodes.
The experiment is an opportunity to study how brain cells function as a network and to learn more about one of the most complex devices in the known universe: the human brain.
By watching the brain cells interact, scientists hope to understand what causes neural disorders, such as epilepsy. The research may also help the researchers in their quest to build "living" computers that combine neural and silicon systems.
"We're hoping to find out exactly how the neurons do what they do and extract those rules and apply them in software or hardware for novel types of computing," DeMarse said.
When the neurons from a rat are put in a dish (filled with a specialized liquid to keep the neurons alive), they resemble grains of sand sprinkled in water. But the cells rapidly begin to connect with each other, forming a living neural network.
"I have a movie of the first eight hours [of this process], and you can literally watch the neurons extend connections to other neurons as they form their network," DeMarse said.
The 25,000 cells sit atop a grid of 60 electrodes, which is just one and a half millimeters (six-hundredths of an inch) wide.
"These electrodes allow us to literally listen to the 'conversations' among the neurons to find out how they are computing," DeMarse said. "By sending in [electronic] pulses to each electrode, we can also stimulate the network in 60 different locations."
To put the experimental brain to the test, the scientist has connected it to a jet flight simulator via the electrode grid and a desktop computer.
At first the brain does not know what to do.
"If you take these cells out of the cortex and you put them into one of these dishes, you remove all of the inputs—sensory systems like vision or hearing—that they would normally have," DeMarse said. "The only thing that's going on is the spontaneous activity of reconnecting."
But as the neurons begin to receive information from the computer about flight conditions—similar to how neurons receive and interpret signals from each other to control our bodies—the brain gradually learns to fly the aircraft.
"The neurons will analyze data from the computer, like whether the plane is flying level or is tilted to one side," DeMarse said. "The neurons respond by sending signals to the plane's controls to alter the flight path. New information is sent back to the neurons, creating a feedback system."
Neural network research may be setting the stage for the creation of so-called hybrid computers based on biological systems.
Silicon-based computers are very accurate and fast at processing some kinds of information, but they have none of the flexibility of the human brain.
"Despite the power of current digital technology, the adaptability of the neuron and its hybrid digital, analog, and chemical information representation may allow novel computing devices to be created," said George Wittenberg, an assistant professor of neurology at Wake Forest University in Winston-Salem, North Carolina.
Brains can easily make certain kinds of computations that computers are unable to do, such as answering open-ended questions about what happened sometime in the past.
"To do a search like that in silicon is pretty difficult, unless you program [a computer] to specifically answer that question," DeMarse said. "Yet these neurons are able to do this in rats and in humans all the time."
Understanding how neurons distribute information and encode it would allow scientists to take those rules and develop a silicon system that operates similar to the neurons, yet has the retention capacity of a silicon computer.
Such living computers may someday be used to fly unmanned airplanes or handle tasks that are dangerous for humans, such as search-and-rescue missions or bomb-damage assessments.
Neural-network research may also help scientists better understand what causes neural disorders. DeMarse's studies, for example, are investigating the evolution of epilepsy.
"We have bundles of electrodes that we insert into the rat brain," he said. "We can do treatment in the animals that [causes] epileptic seizures. It allows us to look at the neural activity over time to see what exactly is changing in terms of that activity leading up to the seizures."
While scientists know a lot about the neurons themselves, DeMarse says little is known about how neurons encode information, for example.
"We're really working at the basic level," he said, "trying to figure out what sort of computation is going on and how it might be occurring."