A Computational Model of a Single Auditory Nerve Fiber for Electric-Acoustic Stimulation

Abstract

Cochlear implant (CI) recipients with preserved acoustic low-frequency hearing in the implanted ear are a growing group among traditional CI users who benefit from hybrid electric-acoustic stimulation (EAS). However, combined ipsilateral electric and acoustic stimulation also introduces interactions between the two modalities that can affect the performance of EAS users. A computational model of a single auditory nerve fiber that is excited by EAS was developed to study the interaction between electric and acoustic stimulation. Two existing models of sole electric or acoustic stimulation were coupled to simulate responses to combined EAS. Different methods of combining both models were implemented. In the coupled model variant, the refractoriness of the simulated fiber leads to suppressive interaction between electrically evoked and acoustically evoked spikes as well as spontaneous activity. The second model variant is an uncoupled EAS model without electric-acoustic interaction. By comparing predictions between the coupled and the noninteracting EAS model, it was possible to infer electric-acoustic interaction at the level of the auditory nerve. The EAS model was used to simulate fiber populations with realistic inter-unit variability, where each unit was represented by the single-fiber model. Predicted thresholds and dynamic ranges, spike rates, latencies, jitter, and vector strengths were compared to empirical data. The presented EAS model provides a framework for future studies of peripheral electric-acoustic interaction.

Pulsatile electrical stimulation creates predictable, correctable disruptions in neural firing

“…These terms can also be re-arranged to estimate the contribution of spontaneous APs and pulse-induced APs to F separately (See Methods). Prior work by our group and others has attempted to capture these interactions using simplifying equations 26,28 , but those attempts do not provide a complete description of the effects observed in our simulation described below.…”

“…Our simulations show a number of effects of pulsatile stimulation on axon channel dynamics that can prevent other pulses from producing APs and override spontaneous activity. The resulting PFRs resemble pulse effects demonstrated across neural systems: high-frequency facilitation (row 1) has been observed in auditory nerve fibers 27,30 ; the PPB effect that leads to a bend in PFR (row 2) has been observed auditory nerve fibers 25 and dorsal column axons 22,27,30 ; high amplitude block is observed in the sciatic nerve (row 3) 31 ; amplitude-dependent growth of firing rates has been observed in the auditory nerve 32 ; experiments on hippocampal neurons 33 , auditory fibers 28 and spinal cord proprioceptive fibers 21 demonstrate pulse-spontaneous additive and blocking effects (Fig. 4a).…”

A dynamical computational model of theta generation in hippocampal circuits to study theta-gamma oscillations during neurostimulation

“…In terms of neurostimulation, most computational work has focused on the mechanisms underlying DBS of the basal ganglia for motor disorders such as Parkinson's disease (Rubin and Terman, 2004;Pirini et al, 2009;Mina et al, 2013;Ebert et al, 2014), peripheral nerve stimulation (Rattay et al, 2003;Kipping and Nogueira, 2022), spinal cord stimulation (Rattay et al, 2000;Capogrosso et al, 2013), or has remained generic (Basu et al, 2018). However, models investigating neurostimulation of hippocampal circuits are scarce (Hendrickson et al, 2016;Bingham et al, 2018), and do not take into account the effects on theta-gamma oscillations.…”

A dynamical computational model of theta generation in hippocampal circuits to study theta-gamma oscillations during neurostimulation

“…In terms of neurostimulation, most computational work has focused on the mechanisms under-lying DBS of the basal ganglia for motor disorders such as Parkinson’s disease ( Rubin and Terman, 2004 ; Pirini et al, 2009 ; Mina et al, 2013 ; Ebert et al, 2014 ), peripheral nerve stimulation ( Rattay et al, 2003 ; Kipping and Nogueira, 2022 ), spinal cord stimulation ( Rattay et al, 2000 ; Capogrosso et al, 2013 ), or has remained generic ( Basu et al, 2018 ). However, models investigating neurostimulation of hippocampal circuits are scarce ( Hendrickson et al, 2016 ; Bingham et al, 2018 ), and do not take into account the effects on theta-gamma oscillations.…”