Thought-Controlled Machines May Be One Step Closer
for National Geographic News
|April 12, 2005|
Scientists have made a brain discovery that could help lead to thought- controlled machines. Recent experiments have shown that a little- understood part of the brain that we use to process information about objects also plays a role when we move a hand or other limb.
Researchers made the key discovery when they studied the brain activity of several patients with electrodes surgically implanted in their brains.
The scientists found that an area of the brain called the ventrolateral prefrontal cortex, located near our temples, processes spatial informationinformation related to movements that we are about to make.
The study could aid the development of prosthetics that are brain-controlled. One application might be a brain-machine interface that helps paralyzed people to move and communicate simply by thinking.
"It had been thought that this area [of the brain] was specialized for object processing [determining what an object is] and did not contribute to spatial processing at all," said Daniel Rizzuto, a postdoctoral neuroscience scholar at the California Institute of Technology in Pasadena.
"This result opens up the possibility of using these spatial signals to control a neural prosthetic device, which will eventually help paralyzed people to move again."
Rizzuto led the study, which was reported last month in the online edition of the research journal Nature Neuroscience.
In the future, neural prosthetic devices could allow paralyzed patients to move a computer cursor or a robotic arm using just their thoughts.
To identify the brain areas that could best control such movements, researchers have usually focused on the areas of the brain directly responsible for the movement of body parts, not the planning stages of the brain, such as the prefrontal cortex.
This brain region is thought to control goal-directed behavior. It selects useful sensory information and integrates it with our "goals" to direct our behavior.
To do so, it follows complex rules that helps us to act appropriately in various situations, Rizzuto explained. "For example, this area [of the brain] helps us to know not to pick up a ringing phone in someone else's house."
To find out exactly what happens in the prefrontal cortex, Rizzuto and his advisor, Richard Andersen, a Caltech neuroscience professor, piggybacked on clinical work done by Adam Mamelak, a neurosurgeon at Huntington Memorial Hospital in Pasadena.
Mamelak was treating three patients with severe epilepsy. Trying to identify the brain areas where the seizures occurred, the neurosurgeon implanted electrodes into the patients' ventrolateral prefrontal cortex.
"So for a couple of weeks these patients are lying there, bored, waiting for a seizure," Rizzuto said. "I was able to get their permission to do my study, taking advantage of the electrodes that were already [surgically implanted] there."
The patients had to watch a computer screen for a flashing target, then remember the target location for a short time, then reach to that location on a touch screen.
Monitoring their brain activity, Rizzuto was able to show conclusively that the ventrolateral prefrontal cortex is involved in how we process spatial information.
"These findings were not surprising to our group, because we understand that object and spatial processing do not necessarily require different processing domains in the brain," Rizzuto said.
"There is more research showing that the brain areas dedicated to object and spatial processing actually have a lot of interconnections with each other," he added. "However, some scientists still hold these traditional ideas of separate object and spatial processing domains, and they may be surprised at our results."
Recent studies of monkeys have shown that neurons in the monkeys' ventrolateral prefrontal cortex also carry spatial signals when monkeys are planning movements.
"The monkey brain is a model for the human brain, and studies like these provide critical evidence that there are indeed [structural likenesses] between them, even at the highest levels of brain processing," said Earl Miller, a neuroscience professor at the Massachusetts Institute of Technology in Cambridge.
The Caltech research is important, Miller said, because it identifies the ventral prefrontal cortex as a site where motor, or body movement, planning takes place, meaning it could be used to drive neural prosthetic devices.
"There may be big advantages to using the prefrontal cortex [for neural prostheses] rather than [the] lower-level motor cortex, because the prefrontal cortex seems less hardwired and specific to the details of the movements than [the] primary motor cortex," Miller said. (The motor cortex is a brain region that controls voluntary muscle movement.)
Movement-planning areas are also less susceptible to damage than areas of the brain directly responsible for movement. In the case of a spinal cord injury, for example, communication to and from the primary motor cortex is cut off: For example, severed nerves might prevent a person's brain from sending signals telling their legs to step forward.
However, the brain still performs the computations associated with planning to move. Scientists could, in theory, tap into these planning calculations and decode where a person is thinking of moving.
"We believe that motor-planning areas will be more resistant to pathological reorganization after spinal injury, as it is already known that neurons in primary motor cortex die after such injuries," Rizzuto said. In other words, neurons in motor-planning parts of the brain are probably less likely to be "scrambled" after an injury than they are in areas that are directly involved in carrying out movement.
As the control center of the brain, the prefrontal cortex could possibly be used to control multiple prosthetic devices simultaneously.
"For instance, a patient could navigate his wheelchair and use an LCD interface to type a letter at the same time," Rizzuto said. "This could be accomplished by having the patient learn different neural codes, or contexts, for different devices."
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