Abstract
A cochlear implant (CI) is an auditory prosthesis that enables hearing by providing electrical stimuli through an electrode array. It has been previously established that the electrode position can influence CI performance. Thus, electrode position should be considered in order to achieve better CI results. This paper describes how the electrode position influences the auditory nerve fiber (ANF) response to either a single pulse or low- (250 pulses/s) and high-rate (5,000 pulses/s) pulse-trains using a computational model. The field potential in the cochlea was calculated using a three-dimensional finite-element model, and the ANF response was simulated using a biophysical ANF model. The effects were evaluated in terms of the dynamic range, stochasticity, and spike excitation pattern. The relative spread, threshold, jitter, and initiated node were analyzed for single-pulse response; and the dynamic range, threshold, initiated node, and interspike interval were analyzed for pulse-train stimuli responses. Electrode position was found to significantly affect the spatiotemporal pattern of the ANF response, and this effect was significantly dependent on the stimulus rate. We believe that these modeling results can provide guidance regarding perimodiolar and lateral insertion of CIs in clinical settings and help understand CI performance.
Highlights
A cochlear implant (CI) is a medical prosthesis used to restore human auditory function
As the electrode-to-fiber distance increases, spike jitter, which is defined as the standard deviation of the spike latencies, is increased; and great spike jitter could characterize the ensemble response of auditory nerve fiber (ANF) fibers [10]
For electrode C, the spikes were initiated between P2 and C3; as the stimulus level increased, the spike was initiated at the more central node, C3. These results indicate that the electrode positions, as well as the stimulus rate, clearly influenced the spatio-ANF responses
Summary
A cochlear implant (CI) is a medical prosthesis used to restore human auditory function. Many research groups have studied the signal processing [1, 2], surgical approach [3], and electrode design [4, 5] of CIs in order to improve CI performance Another such effort is the ongoing research on the effects of electrode position. When an electrode is located closer to the modiolus, less current is required to excite the ANFs. Mino et al (2004) reported on the effects of electrode-to-fiber distance on spatiotemporal patterns of spike initiation using an ANF multicompartment model, and the results of this computer model may support and aid in the understanding of the physiological studies that have examined the effects of electrode position [9]. Despite the modeling results of the variation of electrode-to-fiber distance, the previously reported models have a drawback due to nonrealistic conditions being used
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