Temporal loudness integration at threshold in cochlear implant users: A study on the critical duration and the effects of a very high stimulation rate

zaud000048 10.3205/zaud000048 urn:nbn:de:0183-zaud0000481 Short Report Temporal loudness integration at threshold in cochlear implant users: A study on the critical duration and the effects of a very high stimulation rate Lautheitsintegration an der Hörschwelle bei Cochlea-Implantat-Nutzern: Eine Studie zur kritischen Dauer und den Auswirkungen einer sehr hohen effektiven Stimulationsrate Castañeda González Castañeda González Carmen Marie CM

Technical University of Munich, Munich Institute of Biomedical Engineering, Bio-Inspired Information Processing, Boltzmannstraße 11, 85748 Garching, GermanyTechnical University of Munich, Munich Institute of Biomedical Engineering, Bio-Inspired Information Processing, Garching near Munich, Germany

author Schwanda Schwanda Daniela D

Technical University of Munich, Munich Institute of Biomedical Engineering, Bio-Inspired Information Processing, Garching near Munich, Germany Munich University of Applied Sciences, Department of Applied Sciences and Mechatronics, Munich, Germany

author Obando Leitón Obando Leitón Miguel M

Technical University of Munich, Munich Institute of Biomedical Engineering, Bio-Inspired Information Processing, Garching near Munich, Germany

author Karg Karg Sonja S

Technical University Ingolstadt, Biomedical Engineering and Biosignal Processing, Ingolstadt, Germany

author Hemmert Hemmert Werner W

Technical University of Munich, Munich Institute of Biomedical Engineering, Bio-Inspired Information Processing, Garching near Munich, Germany

author German Medical Science GMS Publishing House

Düsseldorf

610 loudness integration cochlear implants psychoacoustics critical duration high stimulation rate Lautheitsintegration Cochlea-Implantate Psychoakustik kritische Dauer hohe Stimulationsrate 20240910 engl This is an Open Access article distributed under the terms of the Creative Commons Attribution 4.0 License. Dieser Artikel ist ein Open-Access-Artikel und steht unter den Lizenzbedingungen der Creative Commons Attribution 4.0 License (Namensnennung). 2628-9083 6 GMS Zeitschrift für Audiologie - Audiological Acoustics GMS Z Audiol (Audiol Acoust) 13 MED-EL (Innsbruck) Deutsche Forschungsgemeinschaft Die sogenannte Lautheitsintegration (LI) benennt den Effekt, dass mit zunehmender Dauer eines Reizes die entsprechende Hörschwelle sinkt. Bei Normalhörenden (NH) verbessert sich hierbei die Hörschwelle um 6,7 dB/Dekade bis zu einer kritischen Dauer (tkrit) von 200 ms (Heil et al. 2017, Zwislocki 1969). In dieser Studie wurde die LI von sieben Cochlea-Implantat(CI)-Nutzern (MED-EL) an zwei Elektrodenpositionen (apikal, basal) über Direktstimulation bestimmt, jeweils bei einer klini</PlainText></TextGroup>schen und einer höheren Stimulationsrate (1,2 und 25 kpps). Hörschwellen bei Stimulusdauern zwischen einem einzelnen Puls (15 µs Phasendauer) und bis zu 1,5 s langen Pulsfolgen wurden gemessen, um die kritische Dauer t<Subscript>krit</Subscript> zu bestimmen, ab der die Hörschwelle unabhängig von der Stimulationsdauer ist.</Pgraph><Pgraph>Bei konstanter Stimulationsrate nahmen die Hörschwellen mit zunehmender Stimulusdauer ab. Im Mittel wurde kein Einfluss der Elektrodenposition auf die LI-Charakteristik festgestellt. Kritische Dauern von CI-Nutzenden (t<Subscript>krit</Subscript>=244±136 ms) ähnelten kritischen Dauern von NH und waren unabhängig von der Elektrodenposition und der Stimulationsrate. Bei zwei Probanden war es nicht möglich, eine kritische Dauer t<Subscript>krit</Subscript> bei 25 kpps zu bestimmen. Die Steilheit der LI-Kurven war von der Stimulationsrate abhängig: LI-Kurven waren bei 25 kpps steiler (–6,2±0,<TextGroup><PlainText>9 d</PlainText></TextGroup>B/Dekade) als bei 1,2 kpps (–4,1±1,3 dB/Dekade). Es überrascht, dass die LI Steilheit von CI-Nutzenden bei hohen Stimulationsraten vergleichbar mit NH Werten war, obwohl die nichtlineare Kompression im Innenohr bei elektrischer Stimulation fehlt. Daher können die flachen LI-Kurven im elektrischen Hören nicht ausschließlich durch den Verlust der nichtlinearen Kompression erklärt werden. Stattdessen beeinflusste die Stimulationsrate die Steilheit der LI-Kurven, was sich wiederum auf die Wahrnehmung langer und kurzer Töne auswirkt.</Pgraph></Abstract> <Abstract language="en" linked="yes"><Pgraph>Detection thresholds (DTs) decrease with increasing stimulus duration. This phenomenon is known as temporal loudness integration (TLI). In normal hearing (NH), DTs improve by 6.7 dB/decade up to a critical stimulus duration (t<Subscript>crit</Subscript>) of approximately 200 ms (Heil et al. 2017, Zwislocki 1969). In this study, TLI was investigated in seven cochlear implant (CI) users (MED-EL) using direct stimulation at a clinical and at a higher stimulation rate (1.2 and 25 kpps) at two electrode positions (apical, basal). Stimulus durations ranging from a single pulse (15 µs phase duration) to 1.5 s long pulse trains were tested to determine the critical duration t<Subscript>crit</Subscript> above which DTs are independent of stimulus duration.</Pgraph><Pgraph>At a constant stimulation rate, DTs decreased with increasing stimulus duration. On average, no systematic effect of the electrode position was observed. Critical durations in CI users (t<Subscript>crit</Subscript>=244±136 ms) were similar to critical durations in NH, and were independent of the electrode pos<TextGroup><PlainText>i</PlainText></TextGroup>tion and the stimulation rate. For two subjects, it was not possible to determine a critical duration t<Subscript>crit</Subscript> at 25 kpps. The stimulation rate influenced the slope of the TLI. TLI curves were steeper at 25 kpps (–6.2±0.<TextGroup><PlainText>9 dB</PlainText></TextGroup>/dec<TextGroup><PlainText>a</PlainText></TextGroup>de) than at 1.2 kpps (4.1±1.3 dB/decade). Surprisingly, the TLI slope of CI users at high stimulation rates was comparable to NH values, although the nonlinear compression in the inner ear is missing in electrical stimulation. Therefore, our data shows that, at high stimulation rates, TLI curves in electric hearing are similar to acoustic ones, despite the missing non-linear compression in the intact ear. The stimulation rate influenced the steepness of the TLI curves, which in turn affects the CI user’s perception of long and short sounds. </Pgraph></Abstract> <TextBlock linked="yes" name="1 Introduction"> <MainHeadline>1 Introduction</MainHeadline><Pgraph>Listeners perceive short stimuli quieter than long stimuli at the same stimulus intensity. This effect is called temporal loudness integration (TLI). Conversely, at the hearing threshold, short stimuli require higher amplitudes than long stimuli to be perceived. In normal hearing (NH), the detection threshold (DT) drops by 6.7 dB upon a tenfold increase in stimulus duration (decade) <TextLink reference="1"></TextLink>. This improvement in DT holds up to a critical duration t<Subscript>crit</Subscript> of 200 ms <TextLink reference="2"></TextLink>; for longer stimuli, the DT becomes independent of stimulus duration.</Pgraph><Pgraph>The effect of TLI has also been observed in cochlear implant (CI) users <TextLink reference="3"></TextLink>, <TextLink reference="4"></TextLink>. At a fixed stimulation rate, DTs decrease with increasing stimulus duration, i.e., as the number of pulses in a pulse train increases. However, the improvement in DTs is significantly lower than in NH (–1.4 dB/decade <TextLink reference="3"></TextLink>). TLI has mainly been investigated for single-channel stimulation rates between 300 and 3,000 pps (pulses per second) and stimulus durations up to 300 ms <TextLink reference="4"></TextLink>, <TextLink reference="5"></TextLink>, <TextLink reference="6"></TextLink>. Literature on TLI at long<TextGroup><PlainText>er d</PlainText></TextGroup>urations reported inconsistent results on a possible critical duration in electric hearing. While in <TextLink reference="3"></TextLink>, critical durations of around 100 ms were found only in some subjects, <TextLink reference="7"></TextLink> reported critical durations comparable to NH between 5<TextGroup><PlainText>0 a</PlainText></TextGroup>nd 200 ms, and <TextLink reference="8"></TextLink> reported critical durations around 100 ms. Our study set out to find the slope and critical durations for a clinically used single-channel stimulation rate (1.2 kpps) and for a high stimulation rate (25 kpps). Characterizing TLI curves at high stimulation rates is relevant since the coding strategies activate multiple contacts in quick succession. Systematically reviewing the effects of an overall increased stimulation rate may lead to improved coding strategies that provide normal-hearing TLI characteristics and reduce the unpleasant loud distortions known to be a common problem for CI users.</Pgraph><Pgraph>Due to the wide current spread in the cochlea when stimulated with a CI <TextLink reference="9"></TextLink>, <TextLink reference="10"></TextLink>, <TextLink reference="11"></TextLink>, the effective stimulation rate to which a nerve fiber is exposed can correspond to the summed rate of several active electrodes. Therefore, two stimulation rates were selected for this study: (1) a single-channel HDCIS (High-Definition Continuous Interleaved Sampling) stimulation rate of 1.2 kpps and (2) a stimulation rate of 25 kpps. TLI was measured at threshold in seven CI users at two stimulation rates (1.<TextGroup><PlainText>2 k</PlainText></TextGroup>pps and 25 kpps) and two electrode positions (apic<TextGroup><PlainText>a</PlainText></TextGroup>l and basal) using the adjustment method. Stimulus durations from a single pulse (15 µs phase duration) to 1.5 s long pulse trains were tested to determine the crit<TextGroup><PlainText>ic</PlainText></TextGroup>al duration (t<Subscript>crit</Subscript>) from which on DTs are independent of stimulus duration.</Pgraph></TextBlock> <TextBlock linked="yes" name="2 Methods"> <MainHeadline>2 Methods</MainHeadline><SubHeadline>2.1 Subjects and stimuli</SubHeadline><Pgraph>Seven CI users (4 female, 3 male, 8 ears) between 1<TextGroup><PlainText>7 a</PlainText></TextGroup>nd 82 years (mean age: 59±21 years) participated in this study. All subjects had MED-EL implants (products: Sonata, Synchrony, Pulsar, Concerto) and at least one year of CI experience. Subjects gave their informed written consent and received monetary compensation. This study was conducted in accordance with the Declaration of Helsinki and approved by the medical ethics committee of the Klinikum Rechts der Isar (Munich, 2126/08).</Pgraph><Pgraph>Stimuli programmed with MATLAB were sent directly to the electrode array using MED-EL’s MAXBOX, bypassing the speech processor. TLI was examined at two stimulation rates (1.2 and 25 kpps) on an apical (E3) and a basal electrode (E10 out of 12 electrodes in MED-EL CIs). Stimuli were pulse trains of biphasic cathodic-leading pulses with 15 µs phase duration and 2.1 µs interph<TextGroup><PlainText>ase g</PlainText></TextGroup>ap. The duration of the pulse trains ranged from a single pulse to 1.5 s (1,800 pulses at 1.2 kpps and 37,500 pulses at 25 kpps). There were 11 durations measured at 1.2 kpps and 15 durations at 25 kpps, including the single pulse condition. The pulse train containing a single pulse was measured once and assigned to both stimulation rates. During the experiment, the stimulus repeated after a 500 ms pause.</Pgraph><SubHeadline>2.2 Procedure</SubHeadline><Pgraph>Subjects adjusted the stimulation amplitude to their DT using a keyboard (adjustment method); stimulus amplitudes could be changed in fine and coarse steps. Subjects familiarized themselves with the task during a single training round. Four well-separated DTs (single pulse, 1<TextGroup><PlainText>0 ms</PlainText></TextGroup>, 100 ms, and 1.5 ms), five at the higher rate ((single pulse), 1 ms, 10 ms, 100 ms, and 1.5 s), were measured during training at both electrode positions. DT estimates for the remaining durations were linearly interpolated in the log-log domain to speed up the measurement time during the main experiment. Training trials were not randomized; DTs were measured from the longest to the shortest duration, one rate and one electrode at a time.</Pgraph><Pgraph>The main experiment consisted of four repetitions of all possible combinations: electrode x stimulation rate <TextGroup><PlainText>x d</PlainText></TextGroup>uration (50 conditions). Each round contained all 5<TextGroup><PlainText>0 co</PlainText></TextGroup>nditions in randomized order. To minimize biases, DTs were adjusted starting twice from below and twice from above the DT amplitude <TextLink reference="12"></TextLink>. If subjects did not request a break before, breaks were programmed every 2<TextGroup><PlainText>5 m</PlainText></TextGroup>in.</Pgraph><Pgraph>Slopes and critical durations were estimated by fitting the data to a broken stick curve of the form: </Pgraph><Pgraph><ImgLink imgNo="1" imgType="inlineFigure"/></Pgraph><Pgraph>With I being the DT amplitude in CU (current unit, 1 CU corresponds to approximately 1 µA), I<Subscript>1</Subscript> the stimulus amplitude for the single-pulse condition, N the number of pulses, m the slope, N<Subscript>crit</Subscript> the critical duration in number of pulses, and I<Subscript>∞</Subscript> the asymptote value after the critical duration has been exceeded. An exemplary fit for subject S3 (25,000 pps, apical electrode) is shown in Figure 1 <ImgLink imgNo="1" imgType="figure"/>. On a double-logarithmic axis, power functions appear as a linear dependency (see Figure 2 <ImgLink imgNo="2" imgType="figure"/>). Power law fits have already been used to describe NH <TextLink reference="13"></TextLink> and CI data <TextLink reference="5"></TextLink>. Fits worked well with R<Superscript>2</Superscript>=0.97±0.02 and R<Superscript>2</Superscript>=0.98±0.01 at 1.2 kpps for the apical and basal electrode, respect<TextGroup><PlainText>i</PlainText></TextGroup>vely, and R<Superscript>2</Superscript>= 0.99±0.01 and R<Superscript>2</Superscript>=0.99±0.01 at 25 kpps.</Pgraph></TextBlock> <TextBlock linked="yes" name="3 Results"> <MainHeadline>3 Results</MainHeadline><Pgraph>Figure 2 <ImgLink imgNo="2" imgType="figure"/> shows the DTs with regard to the DT amplitude of a single pulse (SP DT) as a function of stimulus dur<TextGroup><PlainText>a</PlainText></TextGroup>tion. The black dotted line denotes NH TLI charact<TextGroup><PlainText>eri</PlainText></TextGroup>stics <TextLink reference="1"></TextLink>, <TextLink reference="2"></TextLink>. TLI was observed at both stimulation rates and electrodes; DTs decreased with increasing stimulus duration up to 244±136 ms and remained unchanged at longer stimulus durations. On average, no systematic effect of the electrode (apical, basal) was observed. In contrast, TLI was affected by the stimulation rate; TLI curves were steeper at the higher stimulation rate. At 1<TextGroup><PlainText>.2 kp</PlainText></TextGroup>ps, DTs decreased with increasing stimulus du<TextGroup><PlainText>rati</PlainText></TextGroup>on by 4.1±1.3 dB/decade up to t<Subscript>crit</Subscript>=206±103 ms (Figure 2 <ImgLink imgNo="2" imgType="figure"/>, left panel). At 25 kpps, DTs improved by 6.2±0.<TextGroup><PlainText>9 dB</PlainText></TextGroup>/decade (t<Subscript>crit</Subscript>=291±182) (Figure 2 <ImgLink imgNo="2" imgType="figure"/>, right panel) and resembled NH TLI (black dotted line). Neither the electrode nor the stimulation rate affected the critical duration. Increasing the stimulation rate from 1.2 kpps to 2<TextGroup><PlainText>5 k</PlainText></TextGroup>pps, which corresponds to increasing the number of pulses within a fixed period of time, also decreased DTs. Although related to TLI, this is a different effect known as multi-pulse integration <TextLink reference="4"></TextLink>, <TextLink reference="14"></TextLink>.</Pgraph><Pgraph>TLI showed high intersubjective variability. TLI slopes <TextGroup><PlainText>at 1.2 k</PlainText></TextGroup>pps ranged from –2.2 dB/decade (S1) to –7.<TextGroup><PlainText>8 dB</PlainText></TextGroup>/decade (S8), the latter even exceeding slopes reported in NH. Interestingly, S8’s slope did not increase further at 25 kpps (–7.2 dB/decade). Slopes at 25 kpps ranged between –4.6 dB/decade (S4) and –7.<TextGroup><PlainText>5 dB</PlainText></TextGroup>/dec<TextGroup><PlainText>a</PlainText></TextGroup>de (S1). Except for S8, all subjects exhibited steeper slopes at the higher stimulation rate, and five out of eight subjects had slopes comparable to, or larger than, NH values (><TextGroup><PlainText>6 dB</PlainText></TextGroup>/decade). Critical durations were between 33 ms (S4) and 751 ms (S2). For two subjects (S5 and S7), no critical duration t<Subscript>crit</Subscript><1.5 s could be determined at the higher rate. Although, on average, the electrode had no systematic effect on the TLI curves, S4 exhibited shorter critical durations at the basal electrode position, e.g., 352 ms (apical, 1.2 kpps) compared to 3<TextGroup><PlainText>3 m</PlainText></TextGroup>s (basal, 1.2 kpps).</Pgraph></TextBlock> <TextBlock linked="yes" name="4 Discussion"> <MainHeadline>4 Discussion</MainHeadline><Pgraph>The slope at which DTs improved with increasing stimulus durations was –4.1±1.3 dB/decade at 1.2 kpps and –6.2±0.9 dB/decade at 25 kpps. These slopes are larger than the –0.42 dB per doubling of duration, equivalent to –1.4 dB/decade, reported for a 100 pps stimulation rate <TextLink reference="3"></TextLink>. The slope for 1.2 kpps is similar, if not somewhat higher, than the –3.5 dB/decade slope for 1.5 kpps stimuli in <TextLink reference="5"></TextLink>. The mean slope of –6.2 dB/decade at 2<TextGroup><PlainText>5 k</PlainText></TextGroup>pps is fittingly higher than slopes found for 1<TextGroup><PlainText>0 k</PlainText></TextGroup>pps (–4.3 dB/decade <TextLink reference="15"></TextLink>) and 18 kpps (–5.5 dB/decade <TextLink reference="5"></TextLink>). As reported by other studies <TextLink reference="4"></TextLink>, <TextLink reference="5"></TextLink>, <TextLink reference="16"></TextLink>, we also observed highly intersubjective variable TLI slopes. Our critical durations (1.2 kpps: 247±123 ms; 25 kpps: 292±182 ms) were comparable to, and higher than, values cited in the literature for electric hearing (100 ms <TextLink reference="3"></TextLink>, <TextLink reference="8"></TextLink>; 50–200 ms <TextLink reference="7"></TextLink>) and NH (200 ms <TextLink reference="2"></TextLink>). In agreement with <TextLink reference="5"></TextLink>, <TextLink reference="16"></TextLink>, no systematic effect of the electrode was observed on average. However, two subjects exhibited noticeable differences between electrodes in accord<TextGroup><PlainText>a</PlainText></TextGroup>nce with <TextLink reference="3"></TextLink>, <TextLink reference="5"></TextLink>, <TextLink reference="14"></TextLink>. These differences within a single subject might be explained by neuronal health at that specific location, proximal to the stimulation site <TextLink reference="4"></TextLink>, <TextLink reference="14"></TextLink>.</Pgraph><Pgraph>Despite several studies suggesting that a central process mediates TLI <TextLink reference="8"></TextLink>, <TextLink reference="15"></TextLink>, <TextLink reference="17"></TextLink>, <TextLink reference="18"></TextLink>, the integration of audit<TextGroup><PlainText>o</PlainText></TextGroup>ry information seems to have important peripheral processing components. It has been hypothesized that TLI slopes are influenced by the nonlinear compression in the inner ear and, therefore, shallow slopes in hearing-impaired listeners (2–3 dB/decade <TextLink reference="19"></TextLink>) are due to the loss of compression in the hearing-impaired ear <TextLink reference="20"></TextLink>. It is thus surprising that the TLI slopes at 25 kpps (–6.<TextGroup><PlainText>2 dB</PlainText></TextGroup>/decade) are comparable to NH values (–6<TextGroup><PlainText>.7 dB</PlainText></TextGroup>/dec<TextGroup><PlainText>a</PlainText></TextGroup>de), even though the nonlinear compression in the inner ear is missing in electric hearing. Even more so, S8 had a slope of –7.8 dB/decade already at 1.2 kpps. Other factors affecting the steepness of TLI slopes include the abnormally rapid increase in neural firing rate with stimulus level <TextLink reference="3"></TextLink>, <TextLink reference="17"></TextLink>, <TextLink reference="19"></TextLink>, <TextLink reference="21"></TextLink>, rapid and high adaptation to electrical stimulation <TextLink reference="4"></TextLink>, <TextLink reference="21"></TextLink>, and neural health <TextLink reference="4"></TextLink>, <TextLink reference="22"></TextLink>.</Pgraph><Pgraph>Our measurements provide new insights into how auditory information is integrated in the auditory system, especially for electrical hearing with a CI. Our data shows that, at high stimulation rates, TLI curves in electric hearing are similar to acoustic ones, despite the missing non-linear compression in the intact ear. The stimulation rate influenced the steepness of the TLI curves, which in turn will affect the CI user’s perception of long and short sounds. As the speech processor and its coding strategy also influence the TLI in CI users, it remains to be investigated how the coding strategy affects TLI and whether steeper TLI curves are beneficial for speech understanding, e.g., for detecting weak consonants of short duration (p, t, k). Restoring natural TLI in CIs is essential for an accurate loudness representation, particularly for the perception of short, impulsive sounds, to avoid unpleasantly loud stimuli. </Pgraph></TextBlock> <TextBlock linked="yes" name="Notes"> <MainHeadline>Notes</MainHeadline><SubHeadline>Conference presentation</SubHeadline><Pgraph>This contribution was presented at the 26<Superscript>th</Superscript> Annual Conference of the German Society of Audiology and published as an abstract <TextLink reference="23"></TextLink>.</Pgraph><SubHeadline>Acknowledgments </SubHeadline><Pgraph>We are particularly grateful to the seven study participants.</Pgraph><Pgraph>MED-EL (Innsbruck) and the German Research Foundation (DFG, Deutsche Forschungsgemeinschaft) [project number 415658392] funded this project.</Pgraph><SubHeadline>Competing interests</SubHeadline><Pgraph>The authors declare that they have no competing interests.</Pgraph></TextBlock> <References linked="yes"> <Reference refNo="1"> <RefAuthor>Heil P</RefAuthor> <RefAuthor>Matysiak A</RefAuthor> <RefAuthor>Neubauer H</RefAuthor> <RefTitle>A probabilistic Poisson-based model accounts for an extensive set of absolute auditory threshold measurements</RefTitle> <RefYear>2017</RefYear> <RefJournal>Hear Res</RefJournal> <RefPage>135-61</RefPage> <RefTotal>Heil P, Matysiak A, Neubauer H. A probabilistic Poisson-based model accounts for an extensive set of absolute auditory threshold measurements. Hear Res. 2017 Sep;353:135-61. DOI: 10.1016/j.heares.2017.06.011</RefTotal> <RefLink>https://doi.org/10.1016/j.heares.2017.06.011</RefLink> </Reference> <Reference refNo="2"> <RefAuthor>Zwislocki JJ</RefAuthor> <RefTitle>Temporal summation of loudness: an analysis</RefTitle> <RefYear>1969</RefYear> <RefJournal>J Acoust Soc Am</RefJournal> <RefPage>431-41</RefPage> <RefTotal>Zwislocki JJ. Temporal summation of loudness: an analysis. J Acoust Soc Am. 1969 Aug;46(2):431-41. DOI: 10.1121/1.1911708</RefTotal> <RefLink>https://doi.org/10.1121/1.1911708</RefLink> </Reference> <Reference refNo="3"> <RefAuthor>Donaldson GS</RefAuthor> <RefAuthor>Viemeister NF</RefAuthor> <RefAuthor>Nelson DA</RefAuthor> <RefTitle>Psychometric functions and temporal integration in electric hearing</RefTitle> <RefYear>1997</RefYear> <RefJournal>J Acoust Soc Am</RefJournal> <RefPage>3706-21</RefPage> <RefTotal>Donaldson GS, Viemeister NF, Nelson DA. Psychometric functions and temporal integration in electric hearing. J Acoust Soc Am. 1997 Jun;101(6):3706-21. DOI: 10.1121/1.418330</RefTotal> <RefLink>https://doi.org/10.1121/1.418330</RefLink> </Reference> <Reference refNo="4"> <RefAuthor>Zhou N</RefAuthor> <RefAuthor>Kraft CT</RefAuthor> <RefAuthor>Colesa DJ</RefAuthor> <RefAuthor>Pfingst BE</RefAuthor> <RefTitle>Integration of Pulse Trains in Humans and Guinea Pigs with Cochlear Implants</RefTitle> <RefYear>2015</RefYear> <RefJournal>J Assoc Res Otolaryngol</RefJournal> <RefPage>523-34</RefPage> <RefTotal>Zhou N, Kraft CT, Colesa DJ, Pfingst BE. Integration of Pulse Trains in Humans and Guinea Pigs with Cochlear Implants. J Assoc Res Otolaryngol. 2015 Aug;16(4):523-34. DOI: 10.1007/s10162-015-0521-0</RefTotal> <RefLink>https://doi.org/10.1007/s10162-015-0521-0</RefLink> </Reference> <Reference refNo="5"> <RefAuthor>Obando-Leitón M</RefAuthor> <RefAuthor>Dietze A</RefAuthor> <RefAuthor>Castañeda González CM</RefAuthor> <RefAuthor>Saeedi A</RefAuthor> <RefAuthor>Karg S</RefAuthor> <RefAuthor>Hemmert W</RefAuthor> <RefTitle>On the Effect of High Stimulation Rates on Temporal Loudness Integration in Cochlear Implant Users</RefTitle> <RefYear>2023</RefYear> <RefJournal>Trends Hear</RefJournal> <RefPage>23312165231207229</RefPage> <RefTotal>Obando-Leitón M, Dietze A, Castañeda González CM, Saeedi A, Karg S, Hemmert W. On the Effect of High Stimulation Rates on Temporal Loudness Integration in Cochlear Implant Users. Trends Hear. 2023;27:23312165231207229. DOI: 10.1177/23312165231207229</RefTotal> <RefLink>https://doi.org/10.1177/23312165231207229</RefLink> </Reference> <Reference refNo="6"> <RefAuthor>Hughes ML</RefAuthor> <RefAuthor>Goehring JL</RefAuthor> <RefAuthor>Baudhuin JL</RefAuthor> <RefAuthor>Schmid KK</RefAuthor> <RefTitle>Effects of stimulus level and rate on psychophysical thresholds for interleaved pulse trains in cochlear implants</RefTitle> <RefYear>2016</RefYear> <RefJournal>J Acoust Soc Am</RefJournal> <RefPage>2297</RefPage> <RefTotal>Hughes ML, Goehring JL, Baudhuin JL, Schmid KK. Effects of stimulus level and rate on psychophysical thresholds for interleaved pulse trains in cochlear implants. J Acoust Soc Am. 2016 Oct;140(4):2297. DOI: 10.1121/1.4963903</RefTotal> <RefLink>https://doi.org/10.1121/1.4963903</RefLink> </Reference> <Reference refNo="7"> <RefAuthor>Shannon RV</RefAuthor> <RefTitle>Temporal processing in cochlear implants</RefTitle> <RefYear>1983</RefYear> <RefJournal>J Acoust Soc Am</RefJournal> <RefPage>110</RefPage> <RefTotal>Shannon RV. Temporal processing in cochlear implants. J Acoust Soc Am. 1983 Nov 1;74(S1):110. DOI: 10.1121/1.2020739</RefTotal> <RefLink>https://doi.org/10.1121/1.2020739</RefLink> </Reference> <Reference refNo="8"> <RefAuthor>McKay CM</RefAuthor> <RefAuthor>Lim HH</RefAuthor> <RefAuthor>Lenarz T</RefAuthor> <RefTitle>Temporal processing in the auditory system: insights from cochlear and auditory midbrain implantees</RefTitle> <RefYear>2013</RefYear> <RefJournal>J Assoc Res Otolaryngol</RefJournal> <RefPage>103-24</RefPage> <RefTotal>McKay CM, Lim HH, Lenarz T. Temporal processing in the auditory system: insights from cochlear and auditory midbrain implantees. J Assoc Res Otolaryngol. 2013 Feb;14(1):103-24. DOI: 10.1007/s10162-012-0354-z</RefTotal> <RefLink>https://doi.org/10.1007/s10162-012-0354-z</RefLink> </Reference> <Reference refNo="9"> <RefAuthor>Ifukube T</RefAuthor> <RefAuthor>White RL</RefAuthor> <RefTitle>Current distributions produced inside and outside the cochlea from a scala tympani electrode array</RefTitle> <RefYear>1987</RefYear> <RefJournal>IEEE Trans Biomed Eng</RefJournal> <RefPage>883-90</RefPage> <RefTotal>Ifukube T, White RL. Current distributions produced inside and outside the cochlea from a scala tympani electrode array. IEEE Trans Biomed Eng. 1987 Nov;34(11):883-90. DOI: 10.1109/tbme.1987.326009</RefTotal> <RefLink>https://doi.org/10.1109/tbme.1987.326009</RefLink> </Reference> <Reference refNo="10"> <RefAuthor>Bai S</RefAuthor> <RefAuthor>Encke J</RefAuthor> <RefAuthor>Obando-Leitón M</RefAuthor> <RefAuthor>Weiß R</RefAuthor> <RefAuthor>Schäfer F</RefAuthor> <RefAuthor>Eberharter J</RefAuthor> <RefAuthor>Böhnke F</RefAuthor> <RefAuthor>Hemmert W</RefAuthor> <RefTitle>Electrical Stimulation in the Human Cochlea: A Computational Study Based on High-Resolution Micro-CT Scans</RefTitle> <RefYear>2019</RefYear> <RefJournal>Front Neurosci</RefJournal> <RefPage>1312</RefPage> <RefTotal>Bai S, Encke J, Obando-Leitón M, Weiß R, Schäfer F, Eberharter J, Böhnke F, Hemmert W. Electrical Stimulation in the Human Cochlea: A Computational Study Based on High-Resolution Micro-CT Scans. Front Neurosci. 2019;13:1312. DOI: 10.3389/fnins.2019.01312</RefTotal> <RefLink>https://doi.org/10.3389/fnins.2019.01312</RefLink> </Reference> <Reference refNo="11"> <RefAuthor>Nelson DA</RefAuthor> <RefAuthor>Kreft HA</RefAuthor> <RefAuthor>Anderson ES</RefAuthor> <RefAuthor>Donaldson GS</RefAuthor> <RefTitle>Spatial tuning curves from apical, middle, and basal electrodes in cochlear implant users</RefTitle> <RefYear>2011</RefYear> <RefJournal>J Acoust Soc Am</RefJournal> <RefPage>3916-33</RefPage> <RefTotal>Nelson DA, Kreft HA, Anderson ES, Donaldson GS. Spatial tuning curves from apical, middle, and basal electrodes in cochlear implant users. J Acoust Soc Am. 2011 Jun;129(6):3916-33. DOI: 10.1121/1.3583503</RefTotal> <RefLink>https://doi.org/10.1121/1.3583503</RefLink> </Reference> <Reference refNo="12"> <RefAuthor>Gelfand SA</RefAuthor> <RefTitle></RefTitle> <RefYear>2017</RefYear> <RefBookTitle>Hearing: An introduction to psychological and physiological acoustics</RefBookTitle> <RefPage></RefPage> <RefTotal>Gelfand SA. Hearing: An introduction to psychological and physiological acoustics. 6th ed. Boca Raton: CRC Press; 2017 Nov 22. DOI: 10.1201/9781315154718</RefTotal> <RefLink>https://doi.org/10.1201/9781315154718</RefLink> </Reference> <Reference refNo="13"> <RefAuthor>Gerken GM</RefAuthor> <RefAuthor>Bhat VK</RefAuthor> <RefAuthor>Hutchison-Clutter M</RefAuthor> <RefTitle>Auditory temporal integration and the power function model</RefTitle> <RefYear>1990</RefYear> <RefJournal>J Acoust Soc Am</RefJournal> <RefPage>767-78</RefPage> <RefTotal>Gerken GM, Bhat VK, Hutchison-Clutter M. Auditory temporal integration and the power function model. J Acoust Soc Am. 1990 Aug;88(2):767-78. DOI: 10.1121/1.399726</RefTotal> <RefLink>https://doi.org/10.1121/1.399726</RefLink> </Reference> <Reference refNo="15"> <RefAuthor>Saeedi A</RefAuthor> <RefAuthor>Hemmert W</RefAuthor> <RefTitle>Investigation of Electrically Evoked Auditory Brainstem Responses to Multi-Pulse Stimulation of High Frequency in Cochlear Implant Users</RefTitle> <RefYear>2020</RefYear> <RefJournal>Front Neurosci</RefJournal> <RefPage>615</RefPage> <RefTotal>Saeedi A, Hemmert W. Investigation of Electrically Evoked Auditory Brainstem Responses to Multi-Pulse Stimulation of High Frequency in Cochlear Implant Users. Front Neurosci. 2020;14:615. DOI: 10.3389/fnins.2020.00615</RefTotal> <RefLink>https://doi.org/10.3389/fnins.2020.00615</RefLink> </Reference> <Reference refNo="16"> <RefAuthor>Zhou N</RefAuthor> <RefAuthor>Xu L</RefAuthor> <RefAuthor>Pfingst BE</RefAuthor> <RefTitle>Characteristics of detection thresholds and maximum comfortable loudness levels as a function of pulse rate in human cochlear implant users</RefTitle> <RefYear>2012</RefYear> <RefJournal>Hear Res</RefJournal> <RefPage>25-32</RefPage> <RefTotal>Zhou N, Xu L, Pfingst BE. Characteristics of detection thresholds and maximum comfortable loudness levels as a function of pulse rate in human cochlear implant users. Hear Res. 2012 Feb;284(1-2):25-32. DOI: 10.1016/j.heares.2011.12.008</RefTotal> <RefLink>https://doi.org/10.1016/j.heares.2011.12.008</RefLink> </Reference> <Reference refNo="14"> <RefAuthor>Pfingst BE</RefAuthor> <RefAuthor>Colesa DJ</RefAuthor> <RefAuthor>Hembrador S</RefAuthor> <RefAuthor>Kang SY</RefAuthor> <RefAuthor>Middlebrooks JC</RefAuthor> <RefAuthor>Raphael Y</RefAuthor> <RefAuthor>Su GL</RefAuthor> <RefTitle>Detection of pulse trains in the electrically stimulated cochlea: effects of cochlear health</RefTitle> <RefYear>2011</RefYear> <RefJournal>J Acoust Soc Am</RefJournal> <RefPage>3954-68</RefPage> <RefTotal>Pfingst BE, Colesa DJ, Hembrador S, Kang SY, Middlebrooks JC, Raphael Y, Su GL. Detection of pulse trains in the electrically stimulated cochlea: effects of cochlear health. J Acoust Soc Am. 2011 Dec;130(6):3954-68. DOI: 10.1121/1.3651820</RefTotal> <RefLink>https://doi.org/10.1121/1.3651820</RefLink> </Reference> <Reference refNo="17"> <RefAuthor>Zwislocki J</RefAuthor> <RefTitle>Theory of temporal auditory summation</RefTitle> <RefYear>1960</RefYear> <RefJournal>J Acoust Soc Am</RefJournal> <RefPage>1046-60</RefPage> <RefTotal>Zwislocki J. Theory of temporal auditory summation. J Acoust Soc Am. 1960 Aug 1;32(8):1046-60. DOI: 10.1121/1.1908276.</RefTotal> <RefLink>https://doi.org/10.1121/1.1908276.</RefLink> </Reference> <Reference refNo="18"> <RefAuthor>Gerken GM</RefAuthor> <RefAuthor>Solecki JM</RefAuthor> <RefAuthor>Boettcher FA</RefAuthor> <RefTitle>Temporal integration of electrical stimulation of auditory nuclei in normal-hearing and hearing-impaired cat</RefTitle> <RefYear>1991</RefYear> <RefJournal>Hear Res</RefJournal> <RefPage>101-12</RefPage> <RefTotal>Gerken GM, Solecki JM, Boettcher FA. Temporal integration of electrical stimulation of auditory nuclei in normal-hearing and hearing-impaired cat. Hear Res. 1991 May;53(1):101-12. DOI: 10.1016/0378-5955(91)90217-w</RefTotal> <RefLink>https://doi.org/10.1016/0378-5955(91)90217-w</RefLink> </Reference> <Reference refNo="19"> <RefAuthor>Carlyon RP</RefAuthor> <RefAuthor>Buus S</RefAuthor> <RefAuthor>Florentine M</RefAuthor> <RefTitle>Temporal integration of trains of tone pulses by normal and by cochlearly impaired listeners</RefTitle> <RefYear>1990</RefYear> <RefJournal>J Acoust Soc Am</RefJournal> <RefPage>260-8</RefPage> <RefTotal>Carlyon RP, Buus S, Florentine M. Temporal integration of trains of tone pulses by normal and by cochlearly impaired listeners. J Acoust Soc Am. 1990 Jan;87(1):260-8. DOI: 10.1121/1.399293</RefTotal> <RefLink>https://doi.org/10.1121/1.399293</RefLink> </Reference> <Reference refNo="20"> <RefAuthor>Penner MJ</RefAuthor> <RefTitle>A power law transformation resulting in a class of short-term integrators that produce time-intensity trades for noise bursts</RefTitle> <RefYear>1978</RefYear> <RefJournal>J Acoust Soc Am</RefJournal> <RefPage>195-201</RefPage> <RefTotal>Penner MJ. A power law transformation resulting in a class of short-term integrators that produce time-intensity trades for noise bursts. J Acoust Soc Am. 1978 Jan;63(1):195-201. DOI: 10.1121/1.381712</RefTotal> <RefLink>https://doi.org/10.1121/1.381712</RefLink> </Reference> <Reference refNo="21"> <RefAuthor>Buus S</RefAuthor> <RefAuthor>Florentine M</RefAuthor> <RefAuthor>Poulsen T</RefAuthor> <RefTitle>Temporal integration of loudness in listeners with hearing losses of primarily cochlear origin</RefTitle> <RefYear>1999</RefYear> <RefJournal>J Acoust Soc Am</RefJournal> <RefPage>3464-80</RefPage> <RefTotal>Buus S, Florentine M, Poulsen T. Temporal integration of loudness in listeners with hearing losses of primarily cochlear origin. J Acoust Soc Am. 1999 Jun;105(6):3464-80. DOI: 10.1121/1.424673</RefTotal> <RefLink>https://doi.org/10.1121/1.424673</RefLink> </Reference> <Reference refNo="22"> <RefAuthor>McKay CM</RefAuthor> <RefTitle>Applications of Phenomenological Loudness Models to Cochlear Implants</RefTitle> <RefYear>2020</RefYear> <RefJournal>Front Psychol</RefJournal> <RefPage>611517</RefPage> <RefTotal>McKay CM. Applications of Phenomenological Loudness Models to Cochlear Implants. Front Psychol. 2020;11:611517. DOI: 10.3389/fpsyg.2020.611517</RefTotal> <RefLink>https://doi.org/10.3389/fpsyg.2020.611517</RefLink> </Reference> <Reference refNo="23"> <RefAuthor>Castañeda González CM</RefAuthor> <RefAuthor>Obando Leitón M</RefAuthor> <RefAuthor>Schwanda D</RefAuthor> <RefAuthor>Karg S</RefAuthor> <RefAuthor>Hemmert W</RefAuthor> <RefTitle>Lautheitsintegration an der Hörschwelle in Cochlea-Implantat-Nutzern: Eine Studie zur kritischen Dauer und den Auswirkungen einer sehr hohen effektiven Stimulationsrate</RefTitle> <RefYear>2024</RefYear> <RefBookTitle>26. Jahrestagung der Deutschen Gesellschaft für Audiologie. Aalen, 06.-08.03.2024</RefBookTitle> <RefPage>Doc187</RefPage> <RefTotal>Castañeda González CM, Obando Leitón M, Schwanda D, Karg S, Hemmert W. Lautheitsintegration an der Hörschwelle in Cochlea-Implantat-Nutzern: Eine Studie zur kritischen Dauer und den Auswirkungen einer sehr hohen effektiven Stimulationsrate. In: Deutsche Gesellschaft für Audiologie e.V., editor. 26 Jahrestagung der Deutschen Gesellschaft für Audiologie. Aalen, 06.-08.03.2024. Düsseldorf: German Medical Science GMS Publishing House; 2024. Doc187. DOI: 10.3205/24dga187</RefTotal> <RefLink>https://doi.org/10.3205/24dga187</RefLink> </Reference> </References> <Media> <Tables> <NoOfTables>0</NoOfTables> </Tables> <Figures> <Figure format="png" height="317" width="378"> <MediaNo>1</MediaNo> <MediaID>1</MediaID> <Caption><Pgraph><Mark1>Figure 1: Fit for the temporal loudness integration (TLI) curve for S3 at threshold (25 kpps, apical electrode; R</Mark1><Mark1><Superscript>2</Superscript></Mark1><Mark1>=0.99). Detection threshold (DT) plotted as amplitudes in CU (current unit, 1 CU is roughly equivalent to 1 µA). Stimulus duration in number of pulses (upper axis) and corresponding duration in milliseconds (lower axis). The lower axis was cut to accommodate the single pulse condition, for which a pulse train duration (in ms) cannot be assigned unambiguously. The vertical dotted line denotes the critical duration N</Mark1><Mark1><Subscript>crit</Subscript></Mark1><Mark1> above which the amplitude remains unchanged (I</Mark1><Subscript>∞</Subscript><Mark1>). </Mark1></Pgraph></Caption> </Figure> <Figure format="png" height="589" width="756"> <MediaNo>2</MediaNo> <MediaID>2</MediaID> <Caption><Pgraph><Mark1>Figure 2: Temporal loudness integration (TLI) at threshold (mean ± standard deviation, n=8). Detection threshold (DT) amplitudes in dB re single-pulse detection threshold (SP DT) of the corresponding electrode. Stimulus duration in number of pulses (upper axis) and corresponding duration in milliseconds (lower axis). The lower axis was cut to accommodate the single pulse condition, for which a pulse train duration (in ms) cannot be assigned unambiguously. The dotted line shows the average TLI in normal hearing with a slope of 6.7 dB/decade and a critical duration of 200 ms. Top: Apical electrode. Bottom: Basal electrode. Left: 1.2 kpps. Right: 25 kpps.</Mark1></Pgraph></Caption> </Figure> <NoOfPictures>2</NoOfPictures> </Figures> <InlineFigures> <Figure format="png" height="36" width="178"> <MediaNo>1</MediaNo> <MediaID>1</MediaID> <AltText>Equation 1</AltText> </Figure> <NoOfPictures>1</NoOfPictures> </InlineFigures> <Attachments> <NoOfAttachments>0</NoOfAttachments> </Attachments> </Media> </OrigData> </GmsArticle>