Posted on Apr 18, 2018, 3 p.m.
For the first time use of tiny arrays of electrodes implanted in the somatosensory cortex has induced sensations of movement and touch in the hand and arm of a paralyzed man by researchers at Caltech, as published in the journal eLife.
Stimulation of a certain region in the brain of a patient with high level spinal cord lesion who could not move or feel his limbs, allowed him to feel sensations of touch and movement. This development may give paralyzed individuals using prosthetics limbs the ability to feel physical feedback from sensors placed in the devices.
The part of the brain governing bodily sensations, both proprioceptive sensations such as movement, and cutaneous sensations such as touch is called the somatosensory cortex. Prior to this work neural implants targeting similar brain areas produced sensations such as tingling or buzzing in the hands. This new implant was able to produce more natural sensations via intracortical stimulation akin to sensations that were experienced by the patient before injury.
Researchers observed that different types of stimulation produced varying sensations, neural codes governing specific physical sensations are still unclear. Researchers hope to create a database of stimulations and corresponding sensations by determining the precise manners and locations in which to place the electrodes to stimulate somatosensory brain areas to induce specific feelings.
Next phase of the research is integration of the new technology with existing neural prosthetics. Connection of existing devices with the somatosensory cortex would make a bidirectional BMI which would enable disabled individuals to feel again using prosthetic limbs. The only feedback available currently is visual for neural prosthetics, meaning participants can watch brain controlled operation of robotic limbs to make corrections, once an object is grasped it is important to have sensory information to manipulate objects dexterously. Stimulation induced somatosensory sensations show potential for added value for prosthetics users in the advantage of producing sense of embodiment.
Materials provided by California Institute of Technology.
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Michelle Armenta Salas, Luke Bashford, Spencer Kellis, Matiar Jafari, HyeongChan Jo, Daniel Kramer, Kathleen Shanfield, Kelsie Pejsa, Brian Lee, Charles Y Liu, Richard A Andersen. Proprioceptive and cutaneous sensations in humans elicited by intracortical microstimulation. eLife, 2018; 7 DOI: 10.7554/eLife.32904