Andreas Bahmer - Academia.edu (original) (raw)
Papers by Andreas Bahmer
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.
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Forschung heute – Zukunft morgen, 2018
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Laryngo-rhino-otologie, Apr 1, 2018
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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...
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IFMBE Proceedings, 2009
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Otology & Neurotology, 2016
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Journal of Neuroscience Methods, 2012
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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.
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Forschung heute – Zukunft morgen, 2018
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Cochlear Implants International, 2013
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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.
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Journal of Neuroscience Methods
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Frontiers in Computational Neuroscience
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Ear and Hearing
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Cochlear Implants International
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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...
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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.
Bookmarks Related papers MentionsView impact
Forschung heute – Zukunft morgen, 2018
Bookmarks Related papers MentionsView impact
Laryngo-rhino-otologie, Apr 1, 2018
Bookmarks Related papers MentionsView impact
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...
Bookmarks Related papers MentionsView impact
IFMBE Proceedings, 2009
Bookmarks Related papers MentionsView impact
Otology & Neurotology, 2016
Bookmarks Related papers MentionsView impact
Journal of Neuroscience Methods, 2012
Bookmarks Related papers MentionsView impact
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.
Bookmarks Related papers MentionsView impact
Forschung heute – Zukunft morgen, 2018
Bookmarks Related papers MentionsView impact
Cochlear Implants International, 2013
Bookmarks Related papers MentionsView impact
Bookmarks Related papers MentionsView impact
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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.
Bookmarks Related papers MentionsView impact
Journal of Neuroscience Methods
Bookmarks Related papers MentionsView impact
Frontiers in Computational Neuroscience
Bookmarks Related papers MentionsView impact
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Ear and Hearing
Bookmarks Related papers MentionsView impact
Cochlear Implants International
Bookmarks Related papers MentionsView impact
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...
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