Selective Wireless Stimulation of Rat Sciatic Nerve

Abstract

Chronic stability of functional performance is a significant challenge to the success of implantable devices for neural stimulation and recording. Integrating wireless technology with typical microelectrode array designs is one approach that may reduce instances of mechanical failure and improve the long-term performance of neural devices. We have investigated the long-term stability of Wireless Floating Microelectrode Arrays (WMFAs) implanted in rat sciatic nerve, and their ability to selectively recruit muscles in the hind limb via neural stimulation. Thresholds as low as 4.1 µA were able to generate visible motion of the rear paw. Each implanted device (n=6) was able to selectively recruit plantar flexion and dorsiflexion of the rear paw, and selective stimulation of both movements was achieved throughout the study period. The evoked limb motion was electrode specific and was dependent on location within the fascicular structure of the nerve. Motor thresholds and movement patterns remained stable for more than 8 weeks after device implantation. No major changes in limb function were observed between the implanted and contralateral limb, or between implanted animals and control group animals. The results of this study show that WFMAs with intrafascicular electrodes implanted in a healthy peripheral nerve can provide stable and selective motor recruitment, without altering overall limb function. Clinical Relevance-This work establishes a compact wireless stimulation device as a versatile platform that can provide selective motor recruitment via peripheral nerve stimulation.

Wireless microelectrode arrays for selective and chronically stable peripheral nerve stimulation for hindlimb movement

“…The remaining 10 electrodes in the group of 21 electrodes evoked a motor response sporadically over the 38 week study and at current thresholds typically above 40 µA. We observed consistent motor recruitment patterns over a 38 week study period at thresholds ranging from 4.1 µA (0.8 nC ph −1 , 41 µC cm −2 ) to 2,3,4,5,6,7,8,10,12,14,16,18,20,22,24,26,28,30,32,34,36,38). For animal A01, no data was recorded during week 7, and no data was recorded for electrode 10 at any time point as the electrode was determined to be non-functional at the time of device fabrication.…”

“…Partial data from weeks 1 through 8 of this study were also reported in [24]. Of the 96 electrodes implanted in total (16 electrodes per device in n = 6 animals), 21 appeared to be either within the epineurium or outside the nerve upon visual inspection at the time of implantation (A01, A03, and A05-E14, E15, and E16; A02, A04, and A06-E01, E02, E03, and E04).…”

“…(b) Color maps of the current threshold values required to generate visible movement in the implanted limb (Implanted Group-left hindlimb). Rows represent each of the 16 electrodes in the implanted array and columns represent each time point of recorded data (week 1, 2, 3,4,5,6,7,8,10,12,14,16,18,20,22,24,26,28,30,32,34,36,38). For animal A01, no data was recorded during week 7, and no data was recorded for electrode 10 at any time point as the electrode was determined to be non-functional at the time of device fabrication.…”

Materials and Devices for Stretchable Electronic Nerve Interfaces

“…2 Video tracking of limb motion can be used to distinguish between plantarflexion and dorsiflexion as well as individual toe movements. 134,135 The most quantifiable test method however is electrical measurement of the evoked muscle response, called electromyography (EMG). 136 EMG measures the action potentials of muscle fibers during muscle contractions.…”

“…For this, the back-end connection would need to be replaced with a non-contact method for transmission of power and information. Some non-stretchable PNIs 93,134,137 , see Chapter 3.3, as well as other stretchable electronic implants not intended for the PNS 138 , already employ such an approach, and one could build on their acquired knowledge. The most promising power transfer methods are radiofrequency (RF) and light.…”