| Summary: | <p>Brain Machine Interfaces (BMI) strive to restore motor and sensory functions lost due to paralysis, amputation, and neurological diseases by interfacing brain circuitry to external actuators in form of a cursor on a computer screen or a robotic limb. There is a strong clinical need for sensory restoration as lack of somatosensory feedback leads to loss of fine motor control and one of the most common preferences for improvements according to individuals with upper-limb loss is the ability to require less visual attention to perform certain functions and to have a better control of wrist movement. One way to restore sensory functions is using electrical microstimulation of brain sensory areas as an artificial sensory channel; however, the ways of creating such artificial sensory inputs are poorly understood. </p><p>This dissertation presents the use of intracortical microstimulation (ICMS) to the primary somatosensory cortex (S1) to guide exploratory arm movements without visual feedback. Two rhesus monkeys were chronically implanted with multielectrode arrays in S1 and primary motor cortex (M1). The monkeys used a hand-held joystick to reach targets with a cursor on a computer screen. ICMS patterns were delivered to S1 when the cursor was placed over the target, mimicking the sense of touch. After the target or the cursor was made invisible, monkeys relied on ICMS feedback instead of vision to perform the task. For an invisible cursor, a random offset was added to the position of the invisible cursor to rule out the possibility that monkeys relied on joystick position felt through proprioception. Learning to perform these tasks was accompanied by changes in both the parameters of arm movements and representation of those parameters by M1 and S1 neurons at a population and individual neuronal levels. </p><p>Offline decoding of single neurons and population of neurons showed that overlapping, but not identical subpopulations of neurons represented movements when ICMS provided feedback instead of vision.</p><p>These results suggest that ICMS could be used as an essential source of sensation from prosthetic limbs.</p> === Dissertation
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