Mentally controlled prosthetic limbs have been available for several years, but they don't provide the smooth, natural movement of natural limbs. Now, researchers believe they have found a way to carry out better operations — by connecting the artificial limb to a different part of the brain.
The motor cortex and premotor cortex are responsible for sending signals to the limbs from the neural center. Previously, that made this the obvious part of the brain to sync with prosthetic devices.
For a new study, researchers connected an artificial arm to the posterior parietal cortex, which formulates the strategy for voluntary movements. For instance — reaching out to grasp a beer begins with the formation of a plan in the posterior parietal cortex. It is relayed to the motor cortex, which distributes orders to the arm and hand for obtaining the beverage.
"The [posterior parietal cortex] forms the initial plans to make movements... Instead of 'I want to control muscles,' we can use smart robotics to work out the fine details [of movement]," said Richard Andersen from the California Institute of Technology.
The new technology prosthetic limb was test-fitted on a patient named Erik G. Sorto, who is paralyzed from the neck down. By connecting the arm directly to the posterior parietal cortex of his brain, the research team was able to bypass the motor cortex to directly translate intentions into actions.
A video shows Sorto picking up a beer using his new artificial arm. This was the first time in a decade that he had been able to get a drink for himself. Unfortunately, the arm is still being tested, so Sorto cannot yet be permanently fitted with the device.
Other researchers are developing a prosthetic limb that provides a sense of touch to the wearer. This feeling is essential in tasks involving fine motor control, as it's difficult to perform detailed tasks with cold, numb fingers.
Future development of the thought-controlled prosthesis will be aimed at providing greater capabilities to its users. One possible advance would be the ability to move individual fingers.
"When you move your arm, you really don't think about which muscles to activate and the details of the movement-such as lift the arm, extend the arm, grasp the cup, close the hand around the cup, and so on," Anderson said. "Instead, you think about the goal of the movement. For example, 'I want to pick up that cup of water.'"
Some researchers question the degree of improvement in motor skills over previous devices, but welcome the research into utilizing different areas of the brain for such connections.
The development of this new artificial arm that utilizes more natural thought patterns was detailed in the journal Science.