Spectral maxima sound coding algorithms, for example n-ofm strategies, used in commercial cochlear implant devices rely on selecting channels with the highest energy in each frequency band. This technique works well i...
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ISBN:
(纸本)9781479928934
Spectral maxima sound coding algorithms, for example n-ofm strategies, used in commercial cochlear implant devices rely on selecting channels with the highest energy in each frequency band. This technique works well in quiet, but is inherently problematic in noisy conditions when noise dominates the target, and noise-dominant channels are mistakenly selected for stimulation. A new channel selection criterion is proposed to addresses this shortcoming which adaptively assigns weights to each time-frequency unit based on the formant location of speech and instantaneous signal to noise ratio. The performance of the proposed technique is evaluated acutely with three cochlear implant users in different noise scenarios. Results indicate that the proposed technique improves speech intelligibility and perception quality, particularly at low signal-to-noise ratio. Significance of the proposed technique lies in its ability to be integrated with the existing sound coding framework employed within commercial cochlear implant processors, making it easier to adapt for resource-limited and time critical devices.
Neuronal diversity in the cochlea is largely determined by ion channels. Among voltage-gated channels, hyperpolarization-activated cyclic nucleotide-gated (HCN) channels open with hyperpolarization and depolarize the ...
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Neuronal diversity in the cochlea is largely determined by ion channels. Among voltage-gated channels, hyperpolarization-activated cyclic nucleotide-gated (HCN) channels open with hyperpolarization and depolarize the cell until the resting membrane potential. The functions for hearing are not well elucidated and knowledge about localization is controversial. We created a detailed map of subcellular location and co-expression of all four HCN subunits across different mammalian species including CBA/J, C57Bl/6N, Ly5.1 mice, guinea pigs, cats, and human subjects. We correlated age-related hearing deterioration in CBA/J and C57Bl/6N with expression levels of HCN1, -2, and -4 in individual auditory neurons from the same cohort. Spatiotemporal expression during murine postnatal development exposed HCN2 and HCN4 involvement in a critical phase of hair cell innervation. The huge diversity of subunit composition, but lack of relevant heteromeric pairing along the perisomatic membrane and axon initial segments, highlighted an active role for auditory neurons. Neuron clusters were found to be the hot spots of HCN1, -2, and -4 immunostaining. HCN channels were also located in afferent and efferent fibers of the sensory epithelium. Age-related changes on HCN subtype expression were not uniform among mice and could not be directly correlated with audiometric data. The oldest mice groups revealed HCN channel up- or downregulation, depending on the mouse strain. The unexpected involvement of HCN channels in outer hair cell function where HCN3 overlaps prestin location emphasized the importance for auditory function. A better understanding may open up new possibilities to tune neuronal responses evoked through electrical stimulation by cochlear implants.
Frontal areas of the mammalian cortex are thought to be important for cognitive control and complex behaviour. These areas have been studied mostly in humans, non-human primates and rodents. In this article, we presen...
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Frontal areas of the mammalian cortex are thought to be important for cognitive control and complex behaviour. These areas have been studied mostly in humans, non-human primates and rodents. In this article, we present a quantitative characterization of response properties of a frontal auditory area responsive to sound in the brain of Carollia perspicillata, the frontal auditory field (FAF). Bats are highly vocal animals, and they constitute an important experimental model for studying the auditory system. We combined electrophysiology experiments and computational simulations to compare the response properties of auditory neurons found in the bat FAF and auditory cortex (AC) to simple sounds (pure tones). Anatomical studies have shown that the latter provides feedforward inputs to the former. Our results show that bat FAF neurons are responsive to sounds, and however, when compared to AC neurons, they presented sparser, less precise spiking and longer-lasting responses. Based on the results of an integrate-and-fire neuronal model, we suggest that slow, subthreshold, synaptic dynamics can account for the activity pattern of neurons in the FAF. These properties reflect the general function of the frontal cortex and likely result from its connections with multiple brain regions, including cortico-cortical projections from the AC to the FAF.
Binaural hearing benefits with bilateral cochlear implants (CI) are usually smaller than with normal hearing (NH) in the same tasks. This gap in performance has typically been attributed to a lack of coordinated stimu...
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It has been suggested that the most important factor for obtaining high speech intelligibility in noise with cochlear implant (CI) recipients is to preserve the low-frequency amplitude modulations of speech across tim...
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It has been suggested that the most important factor for obtaining high speech intelligibility in noise with cochlear implant (CI) recipients is to preserve the low-frequency amplitude modulations of speech across time and frequency by, for example, minimizing the amount of noise in the gaps between speech segments. In contrast, it has also been argued that the transient parts of the speech signal, such as speech onsets, provide the most important information for speech intelligibility. The present study investigated the relative impact of these two factors on the potential benefit of noise reduction for CI recipients by systematically introducing noise estimation errors within speech segments, speech gaps, and the transitions between them. The introduction of these noise estimation errors directly induces errors in the noise reduction gains within each of these regions. Speech intelligibility in both stationary and modulated noise was then measured using a CI simulation tested on normal-hearing listeners. The results suggest that minimizing noise in the speech gaps can improve intelligibility, at least in modulated noise. However, significantly larger improvements were obtained when both the noise in the gaps was minimized and the speech transients were preserved. These results imply that the ability to identify the boundaries between speech segments and speech gaps may be one of the most important factors for a noise reduction algorithm because knowing the boundaries makes it possible to minimize the noise in the gaps as well as enhance the low-frequency amplitude modulations of the speech.
Multi-channel cochlear implants (CI) leverage frequency based cochlear tonotopic mapping to map acoustic information to the cochlear place of stimulation which is primarily determined by electrode locations. Despite t...
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Objective:The fundamental frequency modulation (F0mod) sound processing strategy was developed to improve pitch perception with cochlear implants. In previous work it has been shown to improve performance in a number ...
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Objective:The fundamental frequency modulation (F0mod) sound processing strategy was developed to improve pitch perception with cochlear implants. In previous work it has been shown to improve performance in a number of pitch-related tasks such as pitch ranking, familiar melody identification, and Mandarin Chinese tone identification. The objective of the current study was to compare speech perception with F0mod and the standard clinical advanced combination encoder (ACE) *** sample:Seven cochlear-implant listeners were recruited from the clinical population of the University Hospital ***:F0mod was implemented on a real-time system. Speech recognition in quiet and noise was measured for seven cochlear-implant listeners, comparing F0mod with ACE, using three different Dutch-language speech materials. Additionally the F0 estimator used was evaluated physically, and pitch ranking performance was compared between F0mod and ***:Immediately after switch-on of the F0mod strategy, speech recognition in quiet and noise were similar for ACE and F0mod, for four out of seven listeners. The remaining three listeners were subjected to a short training protocol with F0mod, after which their performance was reassessed, and a significant improvement was ***:As F0mod improves pitch perception, for the seven subjects tested it did not interfere with speech recognition in quiet and noise, and has a low computational complexity, it seems promising for implementation in a clinical sound processor.
Multi-channel cochlear implants (CI) leverage frequency based cochlear tonotopic mapping to map acoustic information to the cochlear place of stimulation which is primarily determined by electrode locations. Despite t...
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ISBN:
(纸本)9781467369985
Multi-channel cochlear implants (CI) leverage frequency based cochlear tonotopic mapping to map acoustic information to the cochlear place of stimulation which is primarily determined by electrode locations. Despite the fact that electrode locations within the cochlea are unique to each patient, the acoustic frequencies assigned to the electrodes by the CI processor are determined generically, resulting in a mismatch between intended and actual pitch perception. This is known to be a limiting factor for hearing outcomes with CIs. In this study, we propose a novel, image-guided CI processor programming strategy to select more optimal, patient-customized frequency assignments. The performance of the proposed strategy was evaluated using vocoder-based simulations with ten normal hearing listeners. In our simulations, our strategy results in significantly better speech recognition scores than the standard clinical strategy.
Objectives: To document musical listening and enjoyment in recipients of Advanced Bionics cochlear implants (CIs) and to compare musical perception in those using early coding strategies with subjects using the newer ...
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Three sound signal compression methods are being offered allowing (depending on the application aim) finding the best trade-off between the compression efficiency and the realization complexity. The testing of the met...
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ISBN:
(纸本)9531840547
Three sound signal compression methods are being offered allowing (depending on the application aim) finding the best trade-off between the compression efficiency and the realization complexity. The testing of the methods proposed was done on a half-nature simulation system including personal computers 10 Mbit/sec Ethernet LAN and the sound signal input/output means.
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