Monkeys moved thought-controlled computer cursors more quickly and accurately when provided with additional sensory feedback, according to a new study in the Dec. 15 issue of The Journal of Neuroscience. While most brain-machine technologies rely only on visual feedback, this study demonstrated that these systems can be improved when users have additional input, such as a sense of the arm’s position and motion, a sensation known as proprioception.
With the aid of brain-controlled devices, paralyzed people have been able to send e-mail, play video games, and operate robotic arms. In this study, researchers led by Nicholas Hatsopoulos, PhD, of the University of Chicago, aimed to help further develop such machines for people who may still experience feeling in paralyzed limbs, including many patients with spinal cord injury and amyotrophic lateral sclerosis (ALS).
“Organisms use multiple senses, including sight and touch, as feedback to adjust motor behavior,” Hatsopoulos said. “The ability to feel movements of the limbs and body is critical for normal motor control. Loss of this sense results in movements that are slow, poorly coordinated, and require great concentration.”
The authors worked with two adult rhesus macaques to assess a system that incorporates a sense of movement. Each monkey was first trained to control a cursor using brain signals only; electrodes collected and processed data from the monkeys’ motor cortex cells and transmitted those commands to the computer. Basic science research has shown that simply thinking about a motion activates brain cells in the same way that making the movement does, so each monkey needed to only think about moving a cursor to do it.
The researchers equipped each animal with a robotic “sleeve” that fit over an arm. In the first part of the experiment, the monkeys controlled the cursor by simply looking at the computer screen. In the second part, the robotic device moved the monkey’s relaxed arm in tandem with the cursor movement, so the monkey could sense the cursor’s motion in time and space. The authors found when the monkeys had the extra sensation, the cursor hit the target faster and more directly. The results also showed increased movement-related information in the activity of motor cortex cells, compared with visual-only feedback.
Hatsopoulos said his group’s findings may pave the way for enhanced brain-controlled devices that include multiple forms of natural or even artificially produced sensory feedback. “Wearable exoskeletal robots could provide sensory information to patients with full or partial feeling,” he said. “Alternatively, direct stimulation of the relevant area of the cortex could be used to replicate sensory feedback in patients who have lost both motor and sensory function.”
The research was supported by the National Institute of Neurological Disorders and Stroke and the Paralyzed Veterans of America Research Foundation.
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