Stanford University researchers have written a mathematical analysis of how neurons in the brain control planned and unplanned arm movements, in an effort to advance brain-controlled prosthetic devices.
The researchers recorded the electrical activity of neurons in monkeys making anticipated and unanticipated reaching motions. When the monkeys anticipated an arm movement, the neurons went into a prepare-and-hold state. However, this state did not occur when the monkeys made unplanned movements, contrary to the researchers' initial theories that a readiness phase was necessary to precede movement.
In three variations of an experiment, the monkeys were trained to touch a target on a display screen, with neural activity measured for each arm motion. For the first experiment, the monkeys were shown the target but trained not to touch it until they received a signal. Next the monkeys were trained to touch the target as soon as it appeared. In the final experiment, the target moved, forcing the monkeys to change their action plan. In all three cases, awareness of the target was the first information to reach the neurons, and the prepare-and-hold state only occurred in the first experiment.
The study improves basic understanding of brain science and will inform the Stanford team's work on electronic systems that convert neural activity into electronic signals to control prosthetic arms or move cursors on a computer screen.
From Stanford Report (CA)
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