Brain Computer Interface

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Brain Current
A single thought triggers a veritable fireworks of electrical signals in the brain. This is how nerve cells (neurons) communicate with each other. There’s an especially large number of neurons in the cerebral cortex, the brain’s outermost layer featuring numerous grooves and folds. The EEG (Electroencephalography) “eavesdrops on” the neurons’ conversations. A high-performance computer is able to recognize patterns in the signals and to classify them as having to do with particular brain functions.

Messages from the Brain
To perform an EEG, small metal plates (electrodes) are applied to the scalp. They measure the electrical activity of the nerve cells. These data are the basis for a so-called electroencephalogram, consisting of fast brain waves as well as slow ones.

Revolution in Neuroscience
About 80 years ago, the EEG revolutionized research on the brain. It thus became possible to investigate a living brain without performing surgery. This has many applications in modern medicine including diagnosis of brain injuries and tumors, epilepsy, brain death, and depth of a coma or anesthesia, and is also used in sleep research.

Controlling a Computer with the Power of Thought?
The so-called brain-computer interface conveys information directly from the brain to the computer. Serving as the interface is usually an EEG cap placed on the subject’s head. Electrodes implanted directly into the brain enable, for example, severely physically handicapped persons to use a computer and to communicate more easily. Now, scientists are investigating methods to make thoughts and dreams visible via EEG.

Fireworks of Concentration
Every day, our brain processes millions of images. In doing so, the brain’s nerve cells emit a wide array of signals. As soon as we concentrate on something-for example, a light blinking at regular intervals-these signals change drastically. They actually assume the rhythm of the blinking light. This is referred to as steady state visual evoked potential (SSVEP). The signal triggered in the brain by a persistent visual impression is highly conspicuous on the electroencephalogram.

Controlling the actions of a robot utilizes SSVEP. Each of the directional keys on a remote control unit blinks with a different frequency at a different speed. When we concentrate on one of the directions, the signals emitted by our nerve cells “blink” in the same pattern as the light. With this input, the computer recognizes which direction we meant and steers the robot accordingly.

Write a Letter Using Only the Power of Thought!
The so-called P300 wave is what makes this possible.
When an anticipated event finally takes place, our brain does not fail to take note of this. Neurons in our cerebral cortex proceed to trigger a fireworks-like signal that the EEG recognizes as a wave. P300 occurs approximately 300 milliseconds after the anticipated event.

The Computer that Reads Thoughts?
First, think of a word-ARS, for instance. The computer then shows you individual letters. When you’re shown the letter A, the brain’s neurons fire. About 300 milliseconds later, a P300 wave occurs. The process is repeated with the remaining letters in the word. Finally, the computer determines which letters your neurons reacted to, and concludes from this information which word you meant.
But letters on a keyboard aren’t all you can control with this technique; you can also use it to operate devices such as a household appliance.

Ars Electronica Futurelab, Courtesy g.tec medical engineering GmbH