Electrodes implanted in the somatosensory region of the brain of a man with paralysis as the result of a high-level spinal cord injury were able to stimulate neurons that produced physical sensations, like a squeeze or tap, in his arm. (Photo courtesy of the Andersen lab)
Scientists from California Institute of Technology (Caltech) report their ability to induce natural sensations in the arm of a paralyzed man with a high-level spinal cord injury by stimulating a certain region of the brain with a tiny array of electrodes.
The research was performed 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.
The study was published recently in the journal eLife.
The patient had become paralyzed from the shoulders down 3 years ago after a spinal cord injury. First, two arrays of tiny electrodes were surgically inserted into his somatosensory cortex. The somatosensory cortex is an area of the brain that governs bodily sensations, both proprioceptive sensations (sensations of movement or the body’s position in space) and cutaneous sensations (those of pressure, vibration, touch, and the like), explains a media release from Caltech.
Using the arrays, the researchers then stimulated neurons in the region with very small pulses of electricity. The participant reported feeling different natural sensations—such as squeezing, tapping, a sense of upward 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 was quite interesting,” the study participant says of the sensations, the release continues. “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 governing specific physical sensations are still unclear. In future work, the researchers hope to determine the precise ways to place the electrodes and stimulate somatosensory brain areas in order to induce specific feelings and create a kind of dictionary of stimulations and their corresponding sensations.
The next major step, according to Andersen, in the release, is to integrate the technology with existing neural prosthetics.
“Currently, the only feedback that is available for neural prosthetics is visual, meaning that participants can watch the brain-controlled operation of robotic limbs to make corrections,” says Andersen.
“However, once an object is grasped, it is essential to also have somatosensory information to dexterously manipulate the object. Stimulation-induced somatosensory sensations have the potential added advantage of producing a sense of embodiment; for example, a participant may feel over time that the robotic limb is a part of their body.”
[Source(s): California Institute of Technology, Science Daily]
