Microstimulation of the lumbar DRG recruits primary afferent neurons in localized regions of lower limb

Abstract

Ayers CA, Fisher LE, Gaunt RA, Weber DJ. Microstimulation of the lumbar DRG recruits primary afferent neurons in localized regions of lower limb. J Neurophysiol 116: 51-60, 2016. First published April 6, 2016 doi:10.1152/jn.00961.2015.-Patterned microstimulation of the dorsal root ganglion (DRG) has been proposed as a method for delivering tactile and proprioceptive feedback to amputees. Previous studies demonstrated that large-and mediumdiameter afferent neurons could be recruited separately, even several months after implantation. However, those studies did not examine the anatomical localization of sensory fibers recruited by microstimulation in the DRG. Achieving precise recruitment with respect to both modality and receptive field locations will likely be crucial to create a viable sensory neuroprosthesis. In this study, penetrating microelectrode arrays were implanted in the L5, L6, and L7 DRG of four isoflurane-anesthetized cats instrumented with nerve cuff electrodes around the proximal and distal branches of the sciatic and femoral nerves. A binary search was used to find the recruitment threshold for evoking a response in each nerve cuff. The selectivity of DRG stimulation was characterized by the ability to recruit individual distal branches to the exclusion of all others at threshold; 84.7% (n ϭ 201) of the stimulation electrodes recruited a single nerve branch, with 9 of the 15 instrumented nerves recruited selectively. The median stimulation threshold was 0.68 nC/phase, and the median dynamic range (increase in charge while stimulation remained selective) was 0.36 nC/phase. These results demonstrate the ability of DRG microstimulation to achieve selective recruitment of the major nerve branches of the hindlimb, suggesting that this approach could be used to drive sensory input from localized regions of the limb. This sensory input might be useful for restoring tactile and proprioceptive feedback to a lowerlimb amputee.

High-density spinal cord stimulation selectively activates lower urinary tract afferents

“…Therefore, we used stimulus-triggered averaging to detect responses evoked by stimulation. The presence of a compound action potential on each nerve was determined by comparing responses following stimulation to baseline recordings in which no stimulation occurred, using a previously-published method 67,68 . To determine the response detection threshold, we calculated the 99% confidence interval on the root mean squared baseline amplitude.…”

Spatial models of cell distribution in human lumbar dorsal root ganglia

“…While most studies have used penetrating electrode arrays to record from neurons in the interior of the DRG, recent work has demonstrated that afferent signals can be recorded from neurons near the exterior of DRG using surface recording arrays (Kashkoush, Gaunt, Fisher, Bruns, & Weber, 2019;Sperry et al, 2018) and that microelectrodes can be used for low-current microstimulation of DRG neurons (Ayers, Fisher, Gaunt, & Weber, 2016;Bruns, Weber, & Gaunt, 2015;Fisher et al, 2014). Additionally, dorsal root ganglion stimulation (DRGS) is an emerging therapy for chronic neuropathic pain (Deer et al, 2017), providing a non-addictive alternative to opioids for pain management.…”

The benefits of sensation on the experience of a hand: A qualitative case series

“…Multiple research groups are working to augment prosthetic hands with naturalistic sensation, delivered via electrical stimulation applied directly to the peripheral nerves [13–18], spinal cord [19], or cortex [20]. Electrical stimulation can produce tactile and proprioceptive sensations referred to the phantom hand and limb.…”