Abstract
BackgroundThe loss of motor functions resulting from spinal cord injury can have devastating implications on the quality of one’s life. Functional electrical stimulation has been used to help restore mobility, however, current functional electrical stimulation (FES) systems require residual movements to control stimulation patterns, which may be unintuitive and not useful for individuals with higher level cervical injuries. Brain machine interfaces (BMI) offer a promising approach for controlling such systems; however, they currently still require transcutaneous leads connecting indwelling electrodes to external recording devices. While several wireless BMI systems have been designed, high signal bandwidth requirements limit clinical translation. Case Western Reserve University has developed an implantable, modular FES system, the Networked Neuroprosthesis (NNP), to perform combinations of myoelectric recording and neural stimulation for controlling motor functions. However, currently the existing module capabilities are not sufficient for intracortical recordings.MethodsHere we designed and tested a 1 × 4 cm, 96-channel neural recording module prototype to fit within the specifications to mate with the NNP. The neural recording module extracts power between 0.3–1 kHz, instead of transmitting the raw, high bandwidth neural data to decrease power requirements.ResultsThe module consumed 33.6 mW while sampling 96 channels at approximately 2 kSps. We also investigated the relationship between average spiking band power and neural spike rate, which produced a maximum correlation of R = 0.8656 (Monkey N) and R = 0.8023 (Monkey W).ConclusionOur experimental results show that we can record and transmit 96 channels at 2ksps within the power restrictions of the NNP system and successfully communicate over the NNP network. We believe this device can be used as an extension to the NNP to produce a clinically viable, fully implantable, intracortically-controlled FES system and advance the field of bioelectronic medicine.
Highlights
The loss of motor functions resulting from spinal cord injury can have devastating implications on the quality of one’s life
In investigation of spike sorted data in comparison to thresholded data for the use in Brain machine interfaces (BMI) we have previously shown that spike sorting does not substantially improve decoding performance
Using similar signal processing techniques from our previous wireless device (Irwin et al 2016), we developed a novel 96-channel intracortical recording device to be used as an extension to the modular, fully implantable functional electrical stimulation (FES) system developed at Case Western Reserve University
Summary
The loss of motor functions resulting from spinal cord injury can have devastating implications on the quality of one’s life. FES systems have been controlled by the user via physical switches, shoulder motion, and wrist position, which allows patients to cycle through pre-programmed stimulation patterns (Prochazka et al 1997; Snoek et al 2000; Handa et al 1992; Johnson et al 1999; Smith et al 1987). Current FES systems use residual myoelectric activity or joint angles as a method of control to achieve more finely tuned movements (Memberg et al 2014; Smith et al 1987) These current methods may work for individuals with partial paralysis, they can be unintuitive for patients and only provide a few degrees of freedom. A control solution which can provide more function to patients with all levels of injury is needed
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