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Effects of electrode position on spatiotemporal auditory nerve fiber responses: a 3D computational model study.

Kang S, Chwodhury T, Moon IJ, Hong SH, Yang H, Won JH, Woo J - Comput Math Methods Med (2015)

Bottom Line: Thus, electrode position should be considered in order to achieve better CI results.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.

View Article: PubMed Central - PubMed

Affiliation: School of Electrical Engineering, Biomedical Engineering, University of Ulsan, Ulsan 680-749, Republic of Korea.

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.

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Comparison of responses to a single biphasic pulse for electrodes A (circle), B (rectangle), C (diamond), and D (triangle). The firing efficiency, mean latency, and jitter in response to 100 identical single pulses at each current level are plotted as functions of the stimulus level. The threshold (θ) is defined as the level evoking a firing efficiency of 0.5. OC: organ of Corti, SM: scala media, ST: scala tympani, and SV: scala vestibuli.
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fig3: Comparison of responses to a single biphasic pulse for electrodes A (circle), B (rectangle), C (diamond), and D (triangle). The firing efficiency, mean latency, and jitter in response to 100 identical single pulses at each current level are plotted as functions of the stimulus level. The threshold (θ) is defined as the level evoking a firing efficiency of 0.5. OC: organ of Corti, SM: scala media, ST: scala tympani, and SV: scala vestibuli.

Mentions: The electrode positions were found to have a significant effect on the site of excitation and influence the spike latency. Figure 3 shows model responses to 100 repeated presentations. The FE (second row), mean latency (third row), and jitter (fourth row) were plotted as functions of the stimulus level. The mean latency and jitter were defined as the mean value and standard deviation of the spike latencies, respectively. The first row of each column shows the position of stimulus electrodes A–D. The FE was fitted to the sigmoid function to estimate the threshold (0.5 FE). The threshold for the electrode position close to the modiolus (C) was lower than those for the electrode positions near the peripheral node (A, B, and D). The threshold for the electrode A was relatively high. The mean latency and jitter decreased along with an increasing stimulus level, and these results are consistent with previous animal ANF data [23]. Moreover, the mean latency for electrode C was found to be shorter, owing to the fact that the spikes were centrally initiated.


Effects of electrode position on spatiotemporal auditory nerve fiber responses: a 3D computational model study.

Kang S, Chwodhury T, Moon IJ, Hong SH, Yang H, Won JH, Woo J - Comput Math Methods Med (2015)

Comparison of responses to a single biphasic pulse for electrodes A (circle), B (rectangle), C (diamond), and D (triangle). The firing efficiency, mean latency, and jitter in response to 100 identical single pulses at each current level are plotted as functions of the stimulus level. The threshold (θ) is defined as the level evoking a firing efficiency of 0.5. OC: organ of Corti, SM: scala media, ST: scala tympani, and SV: scala vestibuli.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4338381&req=5

fig3: Comparison of responses to a single biphasic pulse for electrodes A (circle), B (rectangle), C (diamond), and D (triangle). The firing efficiency, mean latency, and jitter in response to 100 identical single pulses at each current level are plotted as functions of the stimulus level. The threshold (θ) is defined as the level evoking a firing efficiency of 0.5. OC: organ of Corti, SM: scala media, ST: scala tympani, and SV: scala vestibuli.
Mentions: The electrode positions were found to have a significant effect on the site of excitation and influence the spike latency. Figure 3 shows model responses to 100 repeated presentations. The FE (second row), mean latency (third row), and jitter (fourth row) were plotted as functions of the stimulus level. The mean latency and jitter were defined as the mean value and standard deviation of the spike latencies, respectively. The first row of each column shows the position of stimulus electrodes A–D. The FE was fitted to the sigmoid function to estimate the threshold (0.5 FE). The threshold for the electrode position close to the modiolus (C) was lower than those for the electrode positions near the peripheral node (A, B, and D). The threshold for the electrode A was relatively high. The mean latency and jitter decreased along with an increasing stimulus level, and these results are consistent with previous animal ANF data [23]. Moreover, the mean latency for electrode C was found to be shorter, owing to the fact that the spikes were centrally initiated.

Bottom Line: Thus, electrode position should be considered in order to achieve better CI results.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.

View Article: PubMed Central - PubMed

Affiliation: School of Electrical Engineering, Biomedical Engineering, University of Ulsan, Ulsan 680-749, Republic of Korea.

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.

Show MeSH