Paralyzed patient feels sensation again

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For the first time, scientists at Caltech have induced natural sensations in the arm of a paralyzed man by stimulating a certain region of the brain with a tiny array of electrodes. The patient has a high-level spinal cord lesion and, besides not being able to move his limbs, also cannot feel them. The work could one day allow paralyzed people using pros-thetic limbs to feel physical feedback from sensors placed on these devices.
The research was done in the laboratory of Richard Andersen, James G. Boswell Professor of Neuroscience, T&C Chen Brain-Machine Interface Center Leadership Chair, and director of the T&C Chen Brain-Machine Interface Center. A paper de-scribing the work appears in the April 10 issue of the journal eLife.
The somatosensory cortex is a strip of brain that governs bodily sensations, both proprioceptive sen-sations (sensations of movement or the body’s posi-tion in space) and cutaneous sensations (those of pressure, vibration, touch, and the like). Previous to the new work, neural implants targeting similar brain areas predominantly produced sensations such as tingling or buzzing in the hand. The Andersen lab’s implant is able to produce much more natural sensation via intracortical stimulation, akin to sensa-tions experienced by the patient prior to his injury.
The patient had become paralyzed from the shoulders down three years ago after a spinal cord injury. Two arrays of tiny electrodes were surgically inserted into his somatosensory cortex. Using the arrays, the researchers stimulated neurons in the region with very small pulses of electricity. The participant reported feeling different natural sensa-tions — such as squeezing, tapping, a sense of up-ward motion, and several others — that would vary in type, intensity, and location depending on the frequency, amplitude, and location of stimulation from the arrays. It is the first time such natural sen-sations have been induced by intracortical neural stimulation.
“It was quite interesting,” the study participant says of the sensations. “It was a lot of pinching, squeezing, movements, things like that. Hopefully it helps somebody in the future.”
Though different types of stimulation did indeed induce varying sensations, the neural codes govern-ing specific physical sensations are still unclear. In future work, the researchers hope to determine the precise ways to place the electrodes and stimulate somatosensory. .

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