Small electrodes placed on or
inside the brain allow patients to interact with computers or control robotic
limbs simply by thinking about how to execute those actions. This technology
could improve communication and daily life for a person who is paralyzed or has
lost the ability to speak from a stroke or neurodegenerative disease. Now,
University of Washington researchers have demonstrated that when humans use
this technology – called a brain-computer interface – the brain behaves much
like it does when completing simple motor skills such as kicking a ball, typing
or waving a hand. Learning to control a robotic arm or a prosthetic limb could
become second nature for people who are paralyzed. There’s a lot of engagement
of the brain’s cognitive resources at the very beginning, but as you get better
at the task, those resources aren’t needed anymore and the brain is freed up. In
this study, seven people with severe epilepsy were hospitalized for a
monitoring procedure that tries to identify where in the brain seizures
originate. Physicians cut through the scalp, drilled into the skull and placed
a thin sheet of electrodes directly on top of the brain. While they were watching for seizure signals,
the researchers also conducted this study. The patients were asked to move a
mouse cursor on a computer screen by using only their thoughts to control the
cursor’s movement.
Electrodes on their brains picked
up the signals directing the cursor to move, sending them to an amplifier and
then a laptop to be analyzed. Within 40 milliseconds, the computer calculated
the intentions transmitted through the signal and updated the movement of the
cursor on the screen. Researchers found that when patients started the task, a
lot of brain activity was centered in the prefrontal cortex. But after often as
little as 10 minutes, frontal brain activity lessened, and the brain signals
transitioned to patterns similar to those seen during more automatic actions. While
researchers have demonstrated success in using brain-computer interfaces in
monkeys and humans, this is the first study that clearly maps the neurological
signals throughout the brain. The researchers were surprised at how many parts
of the brain were involved. Several types of brain-computer interfaces are
being developed and tested. The least invasive is a device placed on a person’s
head that can detect weak electrical signatures of brain activity. Basic
commercial gaming products are on the market, but this technology isn’t very
reliable yet because signals from eye blinking and other muscle movements
interfere too much. A more invasive alternative is to surgically place
electrodes inside the brain tissue itself to record the activity of individual
neurons.
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