Using a novel brain-machine interface linking neurons with a visual display, researchers at California Institute of Technology (California, USA) reveal how humans pay attention to certain information while ignoring other input.
Moran Cerf and colleagues studied neurons firing in live human brains, connecting patients with intractable epilepsy seizures to electrodes, to monitor activity in the brain’s temporal lobe.
They invited the patients to play a game in which they would control computer images by focusing their attention.
With 12 volunteers, the researchers first established links between specific neurons and familiar images, by showing people pictures and noting which specific neurons became active.
Once they identified at least four images that activated specific neurons, the researchers challenged the patients by showing a target image, then asked the patient to pay attention to the target image and faded-out the competing image.
The team designed an automated system to relay neuron impulses to a computer controlling the images, the first of its kind.
Hooked up to the machine, patients were able to enhance the target image onscreen in real time simply by directing their thoughts. In 69% of the images, patients successfully enhanced the target picture, fading out the competing image.
Supporting the prevailing model of how selective attention works in the brain, the researchers found that when attention is focused, the neuron related to a target image was firing and the neuron associated with the competing image was inhibited -- a mechanism known as biased competition.
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