scholarly journals Modulation depth discrimination by cochlear implant users

2021 ◽  
Author(s):  
Jessica Monaghan ◽  
Robert P. Carlyon ◽  
John M. Deeks
Keyword(s):  
Speech Processing ◽  
Dynamic Range ◽  
Modulation Depth ◽  
High Rate ◽  
Backward Masking ◽  
Pulse Trains ◽  
Processing Strategies ◽  
Depth Discrimination ◽  
Variable Point ◽  
Forced Choice Task

Cochlear implants (CIs) convey the amplitude envelope of speech by modulating high-rate pulse-trains. However, not all of the envelope may be necessary to perceive amplitude modulations (AM); the effective envelope depth may be limited by forward and backward masking from the envelope peaks. Three experiments used modulated pulse-trains to measure which portions of the envelope can be effectively processed by CI users as a function of AM frequency. Experiment 1 used a three-interval forced-choice task to test the ability of CI users to discriminate less-modulated pulse trains from a fully-modulated standard, without controlling for loudness. The stimuli in Experiment 2 were identical, but a two-interval task was used in which participants were required to choose the less-modulated interval, ignoring loudness. Catch trials, in which judgements based on level or modulation depth would give opposing answers were included. Experiment 3 employed novel stimuli whose modulation envelope could be modified below a variable point in the dynamic range, without changing the loudness of the stimulus. Overall, results showed that substantial portions of the envelope are not accurately encoded by CI users. Experiment 1, where loudness cues were available, participants on average were insensitive to changes in the bottom 30% of their dynamic range. In Experiment 2, where loudness was controlled, participants appeared insensitive to changes in the bottom 50% of the dynamic range. In Experiment 3, participants were insensitive to changes in the bottom 80% of the dynamic range. We discuss potential reasons for this insensitivity and implications for CI speech-processing strategies.

Signal Coding in Cochlear Implants: Exploiting Stochastic Effects of Electrical Stimulation

2003 ◽  
Vol 112 (9_suppl) ◽  
pp. 14-19 ◽  
Author(s):  
Jay T. Rubinstein ◽  
Robert Hong
Keyword(s):  
Electrical Stimulation ◽  
Speech Perception ◽  
Cochlear Implants ◽  
Speech Processing ◽  
Music Perception ◽  
Dynamic Range ◽  
High Rate ◽  
Monosyllabic Word ◽  
Stochastic Effects ◽  
Processing Strategies

Speech perception in quiet with cochlear implants has increased substantially over the past 17 years. If current trends continue, average monosyllabic word scores will be nearly 80% by 2010. These improvements are due to enhancements in speech processing strategies, to the implantation of patients with more residual hearing and shorter durations of deafness, and to unknown causes. Despite these improvements, speech perception in noise and music perception are still poor in most implant patients. These deficits may be partly due to poor representation of temporal fine structure by current speech processing strategies. It may be possible to improve both this representation and the dynamic range of electrical stimulation through the exploitation of stochastic effects produced by high-rate (eg, 5-kilopulse-per-second) pulse trains. Both the loudness growth and the dynamic range of low-frequency sinusoids have been enhanced via this technique. A laboratory speech processor using this strategy is under development. Although the clinical programming for such an algorithm is likely to be complex, some guidelines for the psychophysical and electrophysiological techniques necessary can be described now.

scholarly journals Neural Rate and Timing Cues for Detection and Discrimination of Amplitude-Modulated Tones in the Awake Rabbit Inferior Colliculus

2007 ◽  
Vol 97 (1) ◽  
pp. 522-539 ◽  
Author(s):  
Paul C. Nelson ◽  
Laurel H. Carney
Keyword(s):  
Inferior Colliculus ◽  
Dynamic Range ◽  
Modulation Depth ◽  
Average Rate ◽  
Modulation Frequency ◽  
Detection Threshold ◽  
Depth Functions ◽  
Depth Discrimination ◽  
High Modulation ◽  
Envelope Processing

Neural responses to amplitude-modulated (AM) tones in the unanesthetized rabbit inferior colliculus (IC) were studied in an effort to establish explicit relationships between physiological and psychophysical measures of temporal envelope processing. Specifically, responses to variations in modulation depth ( m) at the cell’s best modulation frequency, with and without modulation maskers, were quantified in terms of average rate and synchronization to the envelope over the entire perceptual dynamic range of depths. Statistically significant variations in the metrics were used to define neural AM detection and discrimination thresholds. Synchrony emerged at modulation depths comparable with psychophysical AM detection sensitivities in some neurons, whereas the lowest rate-based neural thresholds could not account for psychoacoustical thresholds. The majority of rate thresholds (85%) were −10 dB or higher (in 20 log m), and 16% of the population exhibited no systematic dependence of average rate on m. Neural thresholds for AM detection did not decrease systematically at higher SPLs (as observed psychophysically): thresholds remained constant or increased with level for most cells tested at multiple sound-pressure levels (SPLs). At depths higher than the rate-based detection threshold, some rate modulation-depth functions were sufficiently steep with respect to the across-trial variability of the rate to predict depth discrimination thresholds as low as 1 dB (comparable with the psychophysics). Synchrony, on the other hand, did not vary systematically with m in many cells at high modulation depths. A simple computational model was extended to reproduce several features of the modulation frequency and depth dependence of both transient and sustained pure-tone responders.

scholarly journals Late maturation of backward masking in auditory cortex

2018 ◽  
Vol 120 (4) ◽  
pp. 1558-1571
Author(s):  
Michelle M. Mattingly ◽  
Brittany M. Donell ◽  
Merri J. Rosen
Keyword(s):  
Language Processing ◽  
Speech Processing ◽  
Dynamic Range ◽  
Developmental Time ◽  
Mongolian Gerbils ◽  
Backward Masking ◽  
Selective Listening ◽  
Age Related ◽  
Time Courses ◽  
Short Signal

Speech perception relies on the accurate resolution of brief, successive sounds that change rapidly over time. Deficits in the perception of such sounds, indicated by a reduced ability to detect signals during auditory backward masking, strongly relate to language processing difficulties in children. Backward masking during normal development has a longer maturational trajectory than many other auditory percepts, implicating the involvement of central auditory neural mechanisms with protracted developmental time courses. Despite the importance of this percept, its neural correlates are not well described at any developmental stage. We therefore measured auditory cortical responses to masked signals in juvenile and adult Mongolian gerbils and quantified the detection ability of individual neurons and neural populations in a manner comparable with psychoacoustic measurements. Perceptually, auditory backward masking manifests as higher thresholds for detection of a short signal followed by a masker than for the same signal in silence. Cortical masking was driven by a combination of suppressed responses to the signal and a reduced dynamic range available for signal detection in the presence of the masker. Both coding elements contributed to greater masked threshold shifts in juveniles compared with adults, but signal-evoked firing suppression was more pronounced in juveniles. Neural threshold shifts were a better match to human psychophysical threshold shifts when quantified with a longer temporal window that included the response to the delayed masker, suggesting that temporally selective listening may contribute to age-related differences in backward masking. NEW & NOTEWORTHY In children, auditory detection of backward masked signals is immature well into adolescence, and detection deficits correlate with problems in speech processing. Our auditory cortical recordings reveal immature backward masking in adolescent animals that mirrors the prolonged development seen in children. This is driven by both signal-evoked suppression and dynamic range reduction. An extended window of analysis suggests that differences in temporally focused listening may contribute to late maturing thresholds for backward masked signals.

scholarly journals SOI-Based Multi-Channel AWG with Fiber Bragg Grating Sensing Interrogation System

Photonics ◽  
2021 ◽  
Vol 8 (6) ◽  
pp. 214
Author(s):  
Siming Weng ◽  
Pei Yuan ◽  
Wei Zhuang ◽  
Dongliang Zhang ◽  
Fei Luo ◽  
...  
Keyword(s):  
Fiber Bragg Grating ◽  
Dynamic Range ◽  
High Dynamic Range ◽  
High Rate ◽  
Bragg Grating ◽  
Arrayed Waveguide Grating ◽  
High Agreement ◽  
High Dynamic ◽  
Critical Components ◽  
Arrayed Waveguide

For the development of minimized and high-rate photonic-integrated fiber Bragg grating interrogation (FBGI) systems, arrayed waveguide grating (AWG) has been widely used as one of the critical components. In this paper, we present an 8-channel SOI-based AWG for a photonic integrated FBG interrogation microsystem. The channel spacing of the AWG is designed to be 3 nm to meet a high-dynamic-range demodulation requirement. The core size of the fabricated AWG is about 335 × 335 μm2. The simulation results and experimental results are in high agreement, showing that AWG has a fine transmission spectrum with crosstalk below −16 dB, nonuniformity below 0.4 dB, insertion loss below −6.35 dB, 3 dB bandwidth about 1.3 nm and 10 dB bandwidth of 2.3 nm. The proposed AWG can be applied perfectly to the SOI-based AWG demodulation microsystem, exhibiting a large dynamic range of 1.2 nm, the resolution for measurements is 1.27 pm and a high accuracy of 20.6 pm.

scholarly journals Contribution of onset/offset information of modulation to amplitude modulation depth discrimination

2008 ◽  
Vol 123 (5) ◽  
pp. EL111-EL115 ◽  
Author(s):  
Derek R. Edwards ◽  
Jungmee Lee ◽  
Jennifer Andrews ◽  
Aileen Wong
Keyword(s):  
Amplitude Modulation ◽  
Modulation Depth ◽  
Depth Discrimination

Responses of primate T1-T5 spinothalamic neurons to gallbladder distension

1984 ◽  
Vol 247 (6) ◽  
pp. R995-R1002 ◽  
Author(s):  
W. S. Ammons ◽  
R. W. Blair ◽  
R. D. Foreman
Keyword(s):  
Chest Pain ◽  
Dynamic Range ◽  
Discharge Rate ◽  
Gallbladder Disease ◽  
High Rate ◽  
High Threshold ◽  
Spinothalamic Tract ◽  
Left Chest ◽  
Afferent Fibers ◽  
Upper Thoracic

Extracellular unit recordings were obtained from 44 spinothalamic tract (STT) neurons in the T1-T5 segments of 15 alpha-chloralose anesthesized monkeys (Macaca fascicularis). Each cell had a somatic receptive field in the left chest region and was excited by electrical stimulation of cardiopulmonary sympathetic afferent fibers. Gallbladder distension to pressures between 20 and 100 mmHg increased activity in 16 of 44 neurons. Responses usually consisted of bursts of activity associated with increased gallbladder pressure (phasic responses) followed by maintained activity during the distension (tonic responses). Magnitude of phasic responses was linearly related to the distending pressure and was consistently greater than magnitude of tonic responses. The gallbladder-responsive and nonresponsive groups included similar proportions of wide dynamic range, high threshold, and high-threshold inhibitory cells. Nine of 10 gallbladder-responsive cells and 11 of 21 gallbladder-nonresponsive cells increased their discharge rate after injection of 2 micrograms/kg bradykinin into left atrium. Activity of cells with gallbladder input increased from 14 +/- 4 to 33 +/- 4 spikes/s. Cells without gallbladder input increased their discharge rate to a significantly less degree (10 +/- 3-23 +/- 4 spikes/s). These results indicate that upper thoracic STT neurons may increase their activity during gallbladder distension. Convergence of afferent information from the chest and gallbladder may explain chest pain occurring during gallbladder disease. Furthermore the tendency of gallbladder-responsive cells to respond to bradykinin injections with a high rate of discharge could explain how this chest pain of gallbladder origin may closely mimic pain of angina pectoris.

scholarly journals Effect of current focusing on the sensitivity of inferior colliculus neurons to amplitude-modulated stimulation

2016 ◽  
Vol 116 (3) ◽  
pp. 1104-1116 ◽  
Author(s):  
Shefin S. George ◽  
Mohit N. Shivdasani ◽  
James B. Fallon
Keyword(s):  
Inferior Colliculus ◽  
Cochlear Implants ◽  
Modulation Depth ◽  
Neural Activation ◽  
Detection Thresholds ◽  
P Values ◽  
Pulse Trains ◽  
Spectral Cues ◽  
Current Focusing ◽  
Channel Interactions

In multichannel cochlear implants (CIs), current is delivered to specific electrodes along the cochlea in the form of amplitude-modulated pulse trains, to convey temporal and spectral cues. Our previous studies have shown that focused multipolar (FMP) and tripolar (TP) stimulation produce more restricted neural activation and reduced channel interactions in the inferior colliculus (IC) compared with traditional monopolar (MP) stimulation, suggesting that focusing of stimulation could produce better transmission of spectral information. The present study explored the capability of IC neurons to detect modulated CI stimulation with FMP and TP stimulation compared with MP stimulation. The study examined multiunit responses of IC neurons in acutely deafened guinea pigs by systematically varying the stimulation configuration, modulation depth, and stimulation level. Stimuli were sinusoidal amplitude-modulated pulse trains (carrier rate of 120 pulses/s). Modulation sensitivity was quantified by measuring modulation detection thresholds (MDTs), defined as the lowest modulation depth required to differentiate the response of a modulated stimulus from an unmodulated one. Whereas MP stimulation showed significantly lower MDTs than FMP and TP stimulation ( P values <0.05) at stimulation ≤2 dB above threshold, all stimulation configurations were found to have similar modulation sensitivities at 4 dB above threshold. There was no difference found in modulation sensitivity between FMP and TP stimulation. The present study demonstrates that current focusing techniques such as FMP and TP can adequately convey amplitude modulation and are comparable to MP stimulation, especially at higher stimulation levels, although there may be some trade-off between spectral and temporal fidelity with current focusing stimulation.

An Introduction to Cochlear Implant Technology, Activation, and Programming

2002 ◽  
Vol 33 (3) ◽  
pp. 153-161 ◽  
Author(s):  
Jan A. Moore ◽  
Holly F. B. Teagle
Keyword(s):  
Hearing Loss ◽  
Cochlear Implant ◽  
Cochlear Implants ◽  
Speech Processing ◽  
Academic Development ◽  
School Age Children ◽  
School Age ◽  
Technology In The Classroom ◽  
Processing Strategies ◽  
Cochlear Implant Surgery

Over the last decade, cochlear implantation has become an increasingly viable alternative for the treatment of profound sensorineural hearing loss in children. Although speech and hearing professionals play an important role in the communicative, social, and academic development of children with cochlear implants, many may be unfamiliar with recent advances in implant technology. This article provides an overview of the components of cochlear implant systems and the speech processing strategies that are currently being used by toddlers, preschoolers, and school-age children. A brief description of cochlear implant surgery and the procedures for programming these devices are also included. Finally, information regarding the use of assistive listening technology in the classroom is presented.

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