Abstract
Objective. One approach to conveying sensory feedback in neuroprostheses is to electrically stimulate sensory neurons in the cortex. For this approach to be viable, it is critical that intracortical microstimulation (ICMS) causes minimal damage to the brain. Here, we investigate the effects of chronic ICMS on the neuronal tissue across a variety of stimulation regimes in non-human primates. We also examine each animal’s ability to use their hand—the cortical representation of which is targeted by the ICMS—as a further assay of possible neuronal damage. Approach. We implanted electrode arrays in the primary somatosensory cortex of three Rhesus macaques and delivered ICMS four hours per day, five days per week, for six months. Multiple regimes of ICMS were delivered to investigate the effects of stimulation parameters on the tissue and behavior. Parameters included current amplitude (10–100 μA), pulse train duration (1, 5 s), and duty cycle (1/1, 1/3). We then performed a range of histopathological assays on tissue near the tips of both stimulated and unstimulated electrodes to assess the effects of chronic ICMS on the tissue and their dependence on stimulation parameters. Main results. While the implantation and residence of the arrays in the cortical tissue did cause significant damage, chronic ICMS had no detectable additional effect; furthermore, the animals exhibited no impairments in fine motor control. Significance. Chronic ICMS may be a viable means to convey sensory feedback in neuroprostheses as it does not cause significant damage to the stimulated tissue.
Highlights
IntroductionIn an attempt to restore motor function, anthropomorphic robotic arms are being developed, as are algorithms to control these arms using signals from the
While the implantation and residence of the arrays caused significant tissue damage, chronic Intracortical microstimulation (ICMS) delivered over the span of months caused minimal additional tissue damage and no detectable behavioral deficits over the range of parameters tested
After six months of chronic ICMS, the non-human primates (NHPs) were perfused, and their brains were removed with the arrays and dura mater intact
Summary
In an attempt to restore motor function, anthropomorphic robotic arms are being developed, as are algorithms to control these arms using signals from the. Signals from the motor cortex of tetraplegic patients have been used to control a robotic limb to perform motor tasks [2, 3]. While this is a remarkable accomplishment, upper-limb neuroprostheses may not be clinically viable until they include somatosensory feedback [1, 4]. To be clinically relevant, ICMS must be demonstrated to be safe and robust over years or decades
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