Andreas Bahmer - Profile on Academia.edu (original) (raw)
Papers by Andreas Bahmer
Effects of electrical pulse polarity shape on intra cochlear neural responses in humans: Triphasic pulses with cathodic second phase
Hearing Research, Dec 1, 2013
Charge balanced pulses are used in modern cochlear implants to avoid direct current (DC) stimulat... more Charge balanced pulses are used in modern cochlear implants to avoid direct current (DC) stimulation that may damage neural tissues. In this context the effect of electrical pulse shape and polarity is still a matter of debate and the most effective pulse shape needs to be determined (Bahmer et al., 2010a; Undurraga et al., 2010; Wieringen et al., 2008; Macherey et al., 2008). Therefore, we conducted electrophysiological measurements, namely electrical compound action potentials (ECAPs) to assess response strength elicited by various pulse shapes and polarities in five cochlear implant recipients (SonataTI100/PulsarCI100 devices, MED-EL Innsbruck). ECAP response strength depending on pulse shape was compared with individual psychophysical thresholds. Results indicated the weakest response amplitude and highest thresholds for symmetric triphasic pulse shapes (with cathodic second phase), and the strongest response amplitude and lowest thresholds for biphasic pulses with anodic first phase. Biphasic pulses with cathodic first phase generated intermediate response amplitude and thresholds.
Triphasic Pulses Reduce Facial Nerve Stimulation in CI Users: Intra- and Postoperative Electromyographic Data
Forschung heute – Zukunft morgen, 2018
Using the Floating Mass Transducer (FMT) as a microphone – a possibility to develop a fully implantable CI?
Laryngo-rhino-otologie, Apr 1, 2018
The aim of this work was to test a new model for oscillating neurons (chopper neurons) in the coc... more The aim of this work was to test a new model for oscillating neurons (chopper neurons) in the cochlear nucleus of the auditory system. In the beginning, it is shown that multiples of 0.4 ms are apparent in intrinsic oscillations in the auditory system and in pitch shift experiments. The existence of a time constant of 0.4 ms is explained by the assumption of a minimum chemical synaptic delay of this size between chopper neurons. The large dynamic range of periodicity coding, the small dynamic range of pure tone response, and the sharp frequency tuning of chopper neurons can be explained as a functional result of simultaneous projections from both the auditory nerve fibers and onset neurons to chopper neurons. As a consequence, the topology of the simulation of chopper neurons is as follows: To ensure the preference for multiples of 0.4 ms as observed in physiological and psychophysical experiments, chopper neurons are arranged in a circular network. The minimum number of two chopper...
IFMBE Proceedings, 2009
Cochlear implants are the first and until now the only existing prosthesis that can substitute an... more Cochlear implants are the first and until now the only existing prosthesis that can substitute an entire sensory system-the hearing system-nearly completely. After implantation and a period of rehabilitation, most deaf patients are able to use the telephone or listen to the radio with their cochlear implant system. Although top performing cochlear implant subjects understand speech nearly perfectly in quiet, large difficulties remain in acoustically complex environments. As well, music appraisal remains poor. It can be assumed that most of these problems arise due to the entrainment of fibers of the auditory nerve to the electrical pulse pattern applied in current stimulation strategies. Several methods were proposed to circumvent this rather artifical stimulation mode. We present methods which account for neurophysiological and neuroanatomical properties of the auditory nerve and cochlear nucleus. To quantify the outcome of these methods we developed several experimental tests.
Otology & Neurotology, 2016
Hypothesis: Triphasic pulse stimulation prevents from facial nerve stimulation (FNS) because of a... more Hypothesis: Triphasic pulse stimulation prevents from facial nerve stimulation (FNS) because of a different electromyographic input-output function compared with biphasic pulse stimulation. Background: FNS is sometimes observed in cochlear implant users as an unwanted side effect of electrical stimulation of the auditory nerve. The common stimulation applied in current cochlear implant consists of biphasic pulse patterns. Two common clinical remedies to prevent unpleasant FNS caused by activation of certain electrodes are to expand their pulse phase duration or simply deactivate them. Unfortunately, in some patients these methods do not provide sufficient FNS prevention. In these patients triphasic pulse can prevent from FNS. The underlying mechanism is yet unclear. Methods: Electromyographic (EMG) recordings of muscles innervated by the facial nerve (musculi orbicularis ori and oculi) were applied to quantitatively assess the effects on FNS. Triphasic and biphasic fitting maps were compared in four subjects with severe FNS. Based on the recordings, a model is presented which intends to explain the beneficial effects of triphasic pulse application. Results: Triphasic stimulation provided by fitting of an OPUS 2 speech processor device. For three patients, EMG was successfully recorded depending on stimulation level up to uncomfortable and intolerable FNS stimulation as upper boarder. The obtained EMG recordings demonstrated high individual variability. However, a difference between the input-output function for biphasic and triphasic pulse stimulation was visually observable. Compared with standard biphasic stimulation, triphasic pulses require higher stimulation levels to elicit an equal amount of FNS, as reflected by EMG amplitudes. In addition, we assume a steeper slope of the input-output function for biphasic pulse stimulation compared with triphasic pulse stimulation. Conclusion: Triphasic pulse stimulation prevents from FNS because of a smaller gradient of EMG input-output function compared with biphasic pulse stimulation. The underlying mechanism can be modeled by differences in spatiotemporal spread of the electrical field.
Journal of Neuroscience Methods, 2012
Triphasic electrical stimulation pulses with an adjustable phase amplitude ratio (PAR) can reduce... more Triphasic electrical stimulation pulses with an adjustable phase amplitude ratio (PAR) can reduce stimulus artifacts in electrically evoked compound actions potentials (ECAPs) recording in the cochlea (see companion paper Bahmer and Baumann, submitted for publication). The present study describes the application of triphasic pulses in forward masking paradigms for recording recovery functions. Masking was found to be most effective using equal masker-probe PAR settings. Results were compared with data applying artifact cancellation strategy for biphasic pulses according to Miller et al. (2000). Measurements were accomplished in five subjects (S1-S5) with an equal masker-probe PAR setting, whereby more detailed test series were carried out in one subject (S1). All subjects were users of MED-EL SONATAti100 or PULSARci100 cochlear implants (Innsbruck, Austria). Parameters like asymptote level, absolute refractory period and time constant were determined by fitting exponential functions to the recovery functions. Detailed measurements collected on 11 electrode locations in subject S1 showed similar parameter profiles on basal electrode contacts for both triphasic and Miller artifact cancellation methods, whereas apical/middle electrode contacts differed in part largely. Compared to Miller's artifact cancellation method estimated asymptote levels were lower with triphasic stimulation; the estimated absolute refractory period and time constants were estimated higher on apical electrodes. Results obtained in subjects S2-S5 showed considerable variances and a proper parametrization of the recovery function was possible only very selectively for triphasic pulse stimulation. In these cases, congruencies in estimated asymptote levels and time constants were found when triphasic stimulation and biphasic stimulation according to Miller were compared.
Pitch Matching Psychometrics in Electric Acoustic Stimulation
Ear & Hearing, 2011
Combined electric-acoustic stimulation (EAS) is a therapeutic option for patients with severe to ... more Combined electric-acoustic stimulation (EAS) is a therapeutic option for patients with severe to profound mid- and high-frequency hearing loss while low-frequency hearing is mostly unaffected. The present study investigates bimodal pitch matching in EAS users as a function of the angular placement of electrodes. Results are compared with data obtained from previous pitch matching studies. Knowledge of electric and acoustic pitch mapping may be important for effective fitting to control the frequency range of acoustic and electric processing. Pitch adjustment experiments were conducted in eight subjects with residual hearing in the opposite ear as well as in the implanted ear. Four subjects received a standard 31.5-mm electrode array and four subjects received the shorter, more flexible 24-mm FLEX electrode array (PULSARCI100 or SONATATI100 stimulator, MED-EL, Innsbruck, Austria). The subjects' task was to listen to single-electrode stimuli presented at a fixed rate (800 pulses per second) via the cochlear implant and to adjust the frequency of the acoustic stimulus until the perceived pitch matched the perception of the electrically conveyed stimulus. Two to four of the most apical electrodes were tested depending on the range of the individual's residual hearing. Postoperative x rays (modified Stenver's view) were analyzed to compare individual pitch matching data in terms of the electrode arrays' insertion angle. The average mean frequency match for the most apical electrode 1 in EAS subjects implanted with the FLEX array was 583 Hz, while for the two subjects with a deep insertion of the 31.5-mm standard electrode array, the matches were 128 and 223 Hz. Because the residual hearing in the EAS subgroup was rather limited in the high-frequency range, a limited number of basal electrodes were assessed to determine the slope of the electric place/pitch function. A considerable variation in terms of the individual pitch function was observed. The slope of the pitch function varied to a large extent among subjects. The differences between contra- and ipsilateral adjustments were very small (mean average 14 Hz) and within the range of the variance (average SD 124 Hz). The application of a pitch matching procedure to assess the electric/acoustic crossover frequency is feasible. In the present study, ipsi- and contralateral pitch matches made by EAS patients were nearly equal; therefore, a severe alteration in the excitation pattern of the basilar membrane in the implanted ear can be ruled out.
Triphasische Pulse reduzieren Fazialisnervstimulation in CI-Nutzern: Intra- und postoperative elektromyographische Daten
Forschung heute – Zukunft morgen, 2018
Cochlear Implants International, 2013
Objectives: Most cochlear implants implement stimulation strategies which apply sequential electr... more Objectives: Most cochlear implants implement stimulation strategies which apply sequential electrical pulses to encode acoustic signals such as speech, noise, and sounds via electrical stimulation of the auditory nerve. Parallel stimulation of adjacent electrodes has been employed in recent cochlear implant (CI) systems in an endeavor to improve coding of pitch information (e.g. FS4-p fine structure with parallel signal processing MED-EL, Innsbruck, Austria; VCIS, AB Corp., Sylmar, CA, USA). We investigated whether parallel stimulation of three adjacent electrodes enhances rate pitch perception compared with single electrode stimulation. Methods: Most comfortable loudness (MCLs) levels were assessed in single and multi electrode condition in 12 subjects (15 ears, PULSARci100/SONATAti100 implant, MED-EL). Rate pitch discrimination was determined by means of an adaptive procedure (two-interval two-alternative forced choice, 2I2AFC) at individual MCL in the single-and multi-electrode condition at base frequencies of 100, 200, 283, 400, and 566 pulses per second (pps) (single electrode condition: electrode 5, multi electrode condition: electrode 4, 5, 6; PULSARci100/SONATAti100 implant: 12 electrode contacts; 1, most apical; 12, most basal). Results: To achieve MCL in the multi-electrode condition significantly higher stimulation current compared with single stimulation was required. No significant difference between single-and multi-electrode condition just noticeable differences in rate discrimination (JNDR) group was found. In contrast, a pairwise comparison of individual results in a subgroup recruited out of successfully completed runs at high base rates showed statistically an improved rate discrimination in 17 of 24 runs in the multi-electrode condition. Therefore, a potential effect of parallel stimulation on rate discrimination is conceivable. Discussion: The results in a subgroup of this study indicate that, compared with single-electrode stimulation, synchronous multi-electrode stimulation of three adjacent electrodes shows improvement rate discrimination in 17 of 24 test runs (binomial and χ 2 test, P = 0.05) but did not result in statistically better JNDRs (best averaged improvement 19.8% at base rate 400 pps).
Ecological psychology pioneered by J.J. Gibson has a powerful influence on the research of percep... more Ecological psychology pioneered by J.J. Gibson has a powerful influence on the research of perception. Ecological psychology is a non-representationalist approach that attempts to overcome dichotomy between agent and environment, action and perception [1]. Overcoming these dichotomies is the key concept of affordance [1]. Affordances are environmental properties, such as height, shape, weight, etc. that can allow opportunities for various actions in relation to the mobility of the perceiver [1]. Moreover, the affordance is processed by the sensory system leading to perception, which may or may not be followed by an action.
The rate pitch discrimination ability of cochlear implant (CI) users is poor compared to normal-h... more The rate pitch discrimination ability of cochlear implant (CI) users is poor compared to normal-hearing (NH) listeners. Already at low pulse rates, the just noticeable difference (JND) is on average about 20% of the base rate, while NH listeners can still discriminate small frequency differences of about 0.2% at 1 kHz. A recent study investigated the application of double pulses with short interpulse intervals (IPIs) to improve temporal coding and therefore improve rate pitch discrimination. It was shown that double pulses with equal amplitudes have no significant effect on rate pitch discrimination. Short IPIs, smaller than the absolute refractory period, result in a facilitation effect (first pulse reduces threshold for second pulse). The effect has its maximum if the amplitude of the first pulse is at or slightly below the ECAP threshold. The hypothesis is that double pulses with maximum facilitation improve temporal processing and therefore influences rate pitch discrimination. Consequently, in our study, the amplitude of the first pulse was set at ECAP threshold, which was determined for each subject individually at one single apical electrode. The amplitude of the second pulse was increased until the pulse train was at most comfortable level. The rate pitch JND of this pulse train was determined for loudness balanced single and double pulses with 15 µs IPI. We will present first results but data collection is still ongoing.
Elektrisch-akustischer Tonhöhenvergleich
Effects of Electrical Pulse Polarity Shape on Intra Cochlear Neural Responses in Humans: Triphasic Pulses with Anodic and Cathodic Second Phase
Hearing Research
Charge balanced pulses are used in modern cochlear implants to avoid direct current (DC) stimulat... more Charge balanced pulses are used in modern cochlear implants to avoid direct current (DC) stimulation that may damage neural tissues. In this context the effect of electrical pulse shape and polarity is still a matter of debate and the most effective pulse shape needs to be determined (Bahmer et al., 2010a; Undurraga et al., 2010; Wieringen et al., 2008; Macherey et al., 2008). Therefore, we conducted electrophysiological measurements, namely electrical compound action potentials (ECAPs) to assess response strength elicited by various pulse shapes and polarities in five cochlear implant recipients (SonataTI100/PulsarCI100 devices, MED-EL Innsbruck). ECAP response strength depending on pulse shape was compared with individual psychophysical thresholds. Results indicated the weakest response amplitude and highest thresholds for symmetric triphasic pulse shapes (with cathodic second phase), and the strongest response amplitude and lowest thresholds for biphasic pulses with anodic first phase. Biphasic pulses with cathodic first phase generated intermediate response amplitude and thresholds.
Evaluation of an artifact reduction strategy for electrically evoked auditory steady-state responses: Simulations and measurements
Journal of Neuroscience Methods
Editorial: Understanding the Importance of Temporal Coupling of Neural Activities in Information Processing Underlying Action and Perception
Frontiers in Computational Neuroscience
Auditory brainstem structures: brain canonical microcircuits for temporal processing?
Loudness Perception and Dynamic Range Depending on Interphase Gaps of Biphasic Pulses in Cochlear Implants
Ear and Hearing
Rate pitch discrimination in cochlear implant users with the use of double pulses and different interpulse intervals
Cochlear Implants International
Perception and motor interaction with physical surroundings can be analyzed by the changes in pro... more Perception and motor interaction with physical surroundings can be analyzed by the changes in probability laws governing two possible outcomes of neuronal activity, namely the presence or absence of spikes (binary states). Perception and motor interaction with physical environment are accounted partly by the reduction in entropy within the probability distributions of binary states of neurons in distributed neural circuits, given the knowledge about the characteristics of stimuli in physical surroundings. This reduction in the total entropy of multiple pairs of circuits in networks, by an amount equal to the increase of mutual information among them, occurs as sensory information is processed successively from lower to higher cortical areas or between different areas at the same hierarchical level but belonging to different networks. The increase in mutual information is partly accounted by temporal coupling as well as synaptic connections as proposed by Bahmer and Gupta [1]. We pro...
Effects of electrical pulse polarity shape on intra cochlear neural responses in humans: Triphasic pulses with cathodic second phase
Hearing Research, Dec 1, 2013
Charge balanced pulses are used in modern cochlear implants to avoid direct current (DC) stimulat... more Charge balanced pulses are used in modern cochlear implants to avoid direct current (DC) stimulation that may damage neural tissues. In this context the effect of electrical pulse shape and polarity is still a matter of debate and the most effective pulse shape needs to be determined (Bahmer et al., 2010a; Undurraga et al., 2010; Wieringen et al., 2008; Macherey et al., 2008). Therefore, we conducted electrophysiological measurements, namely electrical compound action potentials (ECAPs) to assess response strength elicited by various pulse shapes and polarities in five cochlear implant recipients (SonataTI100/PulsarCI100 devices, MED-EL Innsbruck). ECAP response strength depending on pulse shape was compared with individual psychophysical thresholds. Results indicated the weakest response amplitude and highest thresholds for symmetric triphasic pulse shapes (with cathodic second phase), and the strongest response amplitude and lowest thresholds for biphasic pulses with anodic first phase. Biphasic pulses with cathodic first phase generated intermediate response amplitude and thresholds.
Triphasic Pulses Reduce Facial Nerve Stimulation in CI Users: Intra- and Postoperative Electromyographic Data
Forschung heute – Zukunft morgen, 2018
Using the Floating Mass Transducer (FMT) as a microphone – a possibility to develop a fully implantable CI?
Laryngo-rhino-otologie, Apr 1, 2018
The aim of this work was to test a new model for oscillating neurons (chopper neurons) in the coc... more The aim of this work was to test a new model for oscillating neurons (chopper neurons) in the cochlear nucleus of the auditory system. In the beginning, it is shown that multiples of 0.4 ms are apparent in intrinsic oscillations in the auditory system and in pitch shift experiments. The existence of a time constant of 0.4 ms is explained by the assumption of a minimum chemical synaptic delay of this size between chopper neurons. The large dynamic range of periodicity coding, the small dynamic range of pure tone response, and the sharp frequency tuning of chopper neurons can be explained as a functional result of simultaneous projections from both the auditory nerve fibers and onset neurons to chopper neurons. As a consequence, the topology of the simulation of chopper neurons is as follows: To ensure the preference for multiples of 0.4 ms as observed in physiological and psychophysical experiments, chopper neurons are arranged in a circular network. The minimum number of two chopper...
IFMBE Proceedings, 2009
Cochlear implants are the first and until now the only existing prosthesis that can substitute an... more Cochlear implants are the first and until now the only existing prosthesis that can substitute an entire sensory system-the hearing system-nearly completely. After implantation and a period of rehabilitation, most deaf patients are able to use the telephone or listen to the radio with their cochlear implant system. Although top performing cochlear implant subjects understand speech nearly perfectly in quiet, large difficulties remain in acoustically complex environments. As well, music appraisal remains poor. It can be assumed that most of these problems arise due to the entrainment of fibers of the auditory nerve to the electrical pulse pattern applied in current stimulation strategies. Several methods were proposed to circumvent this rather artifical stimulation mode. We present methods which account for neurophysiological and neuroanatomical properties of the auditory nerve and cochlear nucleus. To quantify the outcome of these methods we developed several experimental tests.
Otology & Neurotology, 2016
Hypothesis: Triphasic pulse stimulation prevents from facial nerve stimulation (FNS) because of a... more Hypothesis: Triphasic pulse stimulation prevents from facial nerve stimulation (FNS) because of a different electromyographic input-output function compared with biphasic pulse stimulation. Background: FNS is sometimes observed in cochlear implant users as an unwanted side effect of electrical stimulation of the auditory nerve. The common stimulation applied in current cochlear implant consists of biphasic pulse patterns. Two common clinical remedies to prevent unpleasant FNS caused by activation of certain electrodes are to expand their pulse phase duration or simply deactivate them. Unfortunately, in some patients these methods do not provide sufficient FNS prevention. In these patients triphasic pulse can prevent from FNS. The underlying mechanism is yet unclear. Methods: Electromyographic (EMG) recordings of muscles innervated by the facial nerve (musculi orbicularis ori and oculi) were applied to quantitatively assess the effects on FNS. Triphasic and biphasic fitting maps were compared in four subjects with severe FNS. Based on the recordings, a model is presented which intends to explain the beneficial effects of triphasic pulse application. Results: Triphasic stimulation provided by fitting of an OPUS 2 speech processor device. For three patients, EMG was successfully recorded depending on stimulation level up to uncomfortable and intolerable FNS stimulation as upper boarder. The obtained EMG recordings demonstrated high individual variability. However, a difference between the input-output function for biphasic and triphasic pulse stimulation was visually observable. Compared with standard biphasic stimulation, triphasic pulses require higher stimulation levels to elicit an equal amount of FNS, as reflected by EMG amplitudes. In addition, we assume a steeper slope of the input-output function for biphasic pulse stimulation compared with triphasic pulse stimulation. Conclusion: Triphasic pulse stimulation prevents from FNS because of a smaller gradient of EMG input-output function compared with biphasic pulse stimulation. The underlying mechanism can be modeled by differences in spatiotemporal spread of the electrical field.
Journal of Neuroscience Methods, 2012
Triphasic electrical stimulation pulses with an adjustable phase amplitude ratio (PAR) can reduce... more Triphasic electrical stimulation pulses with an adjustable phase amplitude ratio (PAR) can reduce stimulus artifacts in electrically evoked compound actions potentials (ECAPs) recording in the cochlea (see companion paper Bahmer and Baumann, submitted for publication). The present study describes the application of triphasic pulses in forward masking paradigms for recording recovery functions. Masking was found to be most effective using equal masker-probe PAR settings. Results were compared with data applying artifact cancellation strategy for biphasic pulses according to Miller et al. (2000). Measurements were accomplished in five subjects (S1-S5) with an equal masker-probe PAR setting, whereby more detailed test series were carried out in one subject (S1). All subjects were users of MED-EL SONATAti100 or PULSARci100 cochlear implants (Innsbruck, Austria). Parameters like asymptote level, absolute refractory period and time constant were determined by fitting exponential functions to the recovery functions. Detailed measurements collected on 11 electrode locations in subject S1 showed similar parameter profiles on basal electrode contacts for both triphasic and Miller artifact cancellation methods, whereas apical/middle electrode contacts differed in part largely. Compared to Miller's artifact cancellation method estimated asymptote levels were lower with triphasic stimulation; the estimated absolute refractory period and time constants were estimated higher on apical electrodes. Results obtained in subjects S2-S5 showed considerable variances and a proper parametrization of the recovery function was possible only very selectively for triphasic pulse stimulation. In these cases, congruencies in estimated asymptote levels and time constants were found when triphasic stimulation and biphasic stimulation according to Miller were compared.
Pitch Matching Psychometrics in Electric Acoustic Stimulation
Ear & Hearing, 2011
Combined electric-acoustic stimulation (EAS) is a therapeutic option for patients with severe to ... more Combined electric-acoustic stimulation (EAS) is a therapeutic option for patients with severe to profound mid- and high-frequency hearing loss while low-frequency hearing is mostly unaffected. The present study investigates bimodal pitch matching in EAS users as a function of the angular placement of electrodes. Results are compared with data obtained from previous pitch matching studies. Knowledge of electric and acoustic pitch mapping may be important for effective fitting to control the frequency range of acoustic and electric processing. Pitch adjustment experiments were conducted in eight subjects with residual hearing in the opposite ear as well as in the implanted ear. Four subjects received a standard 31.5-mm electrode array and four subjects received the shorter, more flexible 24-mm FLEX electrode array (PULSARCI100 or SONATATI100 stimulator, MED-EL, Innsbruck, Austria). The subjects' task was to listen to single-electrode stimuli presented at a fixed rate (800 pulses per second) via the cochlear implant and to adjust the frequency of the acoustic stimulus until the perceived pitch matched the perception of the electrically conveyed stimulus. Two to four of the most apical electrodes were tested depending on the range of the individual's residual hearing. Postoperative x rays (modified Stenver's view) were analyzed to compare individual pitch matching data in terms of the electrode arrays' insertion angle. The average mean frequency match for the most apical electrode 1 in EAS subjects implanted with the FLEX array was 583 Hz, while for the two subjects with a deep insertion of the 31.5-mm standard electrode array, the matches were 128 and 223 Hz. Because the residual hearing in the EAS subgroup was rather limited in the high-frequency range, a limited number of basal electrodes were assessed to determine the slope of the electric place/pitch function. A considerable variation in terms of the individual pitch function was observed. The slope of the pitch function varied to a large extent among subjects. The differences between contra- and ipsilateral adjustments were very small (mean average 14 Hz) and within the range of the variance (average SD 124 Hz). The application of a pitch matching procedure to assess the electric/acoustic crossover frequency is feasible. In the present study, ipsi- and contralateral pitch matches made by EAS patients were nearly equal; therefore, a severe alteration in the excitation pattern of the basilar membrane in the implanted ear can be ruled out.
Triphasische Pulse reduzieren Fazialisnervstimulation in CI-Nutzern: Intra- und postoperative elektromyographische Daten
Forschung heute – Zukunft morgen, 2018
Cochlear Implants International, 2013
Objectives: Most cochlear implants implement stimulation strategies which apply sequential electr... more Objectives: Most cochlear implants implement stimulation strategies which apply sequential electrical pulses to encode acoustic signals such as speech, noise, and sounds via electrical stimulation of the auditory nerve. Parallel stimulation of adjacent electrodes has been employed in recent cochlear implant (CI) systems in an endeavor to improve coding of pitch information (e.g. FS4-p fine structure with parallel signal processing MED-EL, Innsbruck, Austria; VCIS, AB Corp., Sylmar, CA, USA). We investigated whether parallel stimulation of three adjacent electrodes enhances rate pitch perception compared with single electrode stimulation. Methods: Most comfortable loudness (MCLs) levels were assessed in single and multi electrode condition in 12 subjects (15 ears, PULSARci100/SONATAti100 implant, MED-EL). Rate pitch discrimination was determined by means of an adaptive procedure (two-interval two-alternative forced choice, 2I2AFC) at individual MCL in the single-and multi-electrode condition at base frequencies of 100, 200, 283, 400, and 566 pulses per second (pps) (single electrode condition: electrode 5, multi electrode condition: electrode 4, 5, 6; PULSARci100/SONATAti100 implant: 12 electrode contacts; 1, most apical; 12, most basal). Results: To achieve MCL in the multi-electrode condition significantly higher stimulation current compared with single stimulation was required. No significant difference between single-and multi-electrode condition just noticeable differences in rate discrimination (JNDR) group was found. In contrast, a pairwise comparison of individual results in a subgroup recruited out of successfully completed runs at high base rates showed statistically an improved rate discrimination in 17 of 24 runs in the multi-electrode condition. Therefore, a potential effect of parallel stimulation on rate discrimination is conceivable. Discussion: The results in a subgroup of this study indicate that, compared with single-electrode stimulation, synchronous multi-electrode stimulation of three adjacent electrodes shows improvement rate discrimination in 17 of 24 test runs (binomial and χ 2 test, P = 0.05) but did not result in statistically better JNDRs (best averaged improvement 19.8% at base rate 400 pps).
Ecological psychology pioneered by J.J. Gibson has a powerful influence on the research of percep... more Ecological psychology pioneered by J.J. Gibson has a powerful influence on the research of perception. Ecological psychology is a non-representationalist approach that attempts to overcome dichotomy between agent and environment, action and perception [1]. Overcoming these dichotomies is the key concept of affordance [1]. Affordances are environmental properties, such as height, shape, weight, etc. that can allow opportunities for various actions in relation to the mobility of the perceiver [1]. Moreover, the affordance is processed by the sensory system leading to perception, which may or may not be followed by an action.
The rate pitch discrimination ability of cochlear implant (CI) users is poor compared to normal-h... more The rate pitch discrimination ability of cochlear implant (CI) users is poor compared to normal-hearing (NH) listeners. Already at low pulse rates, the just noticeable difference (JND) is on average about 20% of the base rate, while NH listeners can still discriminate small frequency differences of about 0.2% at 1 kHz. A recent study investigated the application of double pulses with short interpulse intervals (IPIs) to improve temporal coding and therefore improve rate pitch discrimination. It was shown that double pulses with equal amplitudes have no significant effect on rate pitch discrimination. Short IPIs, smaller than the absolute refractory period, result in a facilitation effect (first pulse reduces threshold for second pulse). The effect has its maximum if the amplitude of the first pulse is at or slightly below the ECAP threshold. The hypothesis is that double pulses with maximum facilitation improve temporal processing and therefore influences rate pitch discrimination. Consequently, in our study, the amplitude of the first pulse was set at ECAP threshold, which was determined for each subject individually at one single apical electrode. The amplitude of the second pulse was increased until the pulse train was at most comfortable level. The rate pitch JND of this pulse train was determined for loudness balanced single and double pulses with 15 µs IPI. We will present first results but data collection is still ongoing.
Elektrisch-akustischer Tonhöhenvergleich
Effects of Electrical Pulse Polarity Shape on Intra Cochlear Neural Responses in Humans: Triphasic Pulses with Anodic and Cathodic Second Phase
Hearing Research
Charge balanced pulses are used in modern cochlear implants to avoid direct current (DC) stimulat... more Charge balanced pulses are used in modern cochlear implants to avoid direct current (DC) stimulation that may damage neural tissues. In this context the effect of electrical pulse shape and polarity is still a matter of debate and the most effective pulse shape needs to be determined (Bahmer et al., 2010a; Undurraga et al., 2010; Wieringen et al., 2008; Macherey et al., 2008). Therefore, we conducted electrophysiological measurements, namely electrical compound action potentials (ECAPs) to assess response strength elicited by various pulse shapes and polarities in five cochlear implant recipients (SonataTI100/PulsarCI100 devices, MED-EL Innsbruck). ECAP response strength depending on pulse shape was compared with individual psychophysical thresholds. Results indicated the weakest response amplitude and highest thresholds for symmetric triphasic pulse shapes (with cathodic second phase), and the strongest response amplitude and lowest thresholds for biphasic pulses with anodic first phase. Biphasic pulses with cathodic first phase generated intermediate response amplitude and thresholds.
Evaluation of an artifact reduction strategy for electrically evoked auditory steady-state responses: Simulations and measurements
Journal of Neuroscience Methods
Editorial: Understanding the Importance of Temporal Coupling of Neural Activities in Information Processing Underlying Action and Perception
Frontiers in Computational Neuroscience
Auditory brainstem structures: brain canonical microcircuits for temporal processing?
Loudness Perception and Dynamic Range Depending on Interphase Gaps of Biphasic Pulses in Cochlear Implants
Ear and Hearing
Rate pitch discrimination in cochlear implant users with the use of double pulses and different interpulse intervals
Cochlear Implants International
Perception and motor interaction with physical surroundings can be analyzed by the changes in pro... more Perception and motor interaction with physical surroundings can be analyzed by the changes in probability laws governing two possible outcomes of neuronal activity, namely the presence or absence of spikes (binary states). Perception and motor interaction with physical environment are accounted partly by the reduction in entropy within the probability distributions of binary states of neurons in distributed neural circuits, given the knowledge about the characteristics of stimuli in physical surroundings. This reduction in the total entropy of multiple pairs of circuits in networks, by an amount equal to the increase of mutual information among them, occurs as sensory information is processed successively from lower to higher cortical areas or between different areas at the same hierarchical level but belonging to different networks. The increase in mutual information is partly accounted by temporal coupling as well as synaptic connections as proposed by Bahmer and Gupta [1]. We pro...