In order for devices controlled by a brain-machine interface to work, scientists must successfully acquire and decode a person’s brain signals. The technology can vary, but all systems require sensors to measure brain activity.
The brain has billions of neurons, and it’s impossible for scientists to collect signals from them all at once. Luckily, only a small fraction of the brain’s neurons need to activate to create signals that lead to physical movements.graphic4_bmi-mechanism
“Typically in these experiments we record 100 to 200 neurons,” said Lee Miller, a researcher and professor at Northwestern University, “which, it sounds funny to say, but are more than are needed to specify the movement.”
Researchers are looking at brain activity trying to predict what the brain is telling the body to do. In ongoing experimental work, scientists record signals from patients as they perform movements, like walking for example. They simultaneously record what the brain is doing and what the body is doing, so they can later match up the brain signals to that same movement. For paralyzed patients who cannot walk, scientists collect patients’ brain signals as they simply think about walking. Using the data, researchers can develop algorithms that predict the most likely movement the brain is calling for.
Some methods for collecting brain signals are considered invasive, meaning that they require surgery, while others are not.