scholarly journals Microsecond Interaural Time Difference Discrimination Restored by Cochlear Implants After Neonatal Deafness

2018 ◽  
Author(s):  
Nicole Rosskothen-Kuhl ◽  
Alexa N Buck ◽  
Kongyan Li ◽  
Jan W H Schnupp
Keyword(s):  
Cochlear Implants ◽  
Critical Period ◽  
Interaural Time Difference ◽  
Spatial Hearing ◽  
Time Difference ◽  
Interaural Time Differences ◽  
Behavioral Thresholds ◽  
Essentially Normal ◽  
High Degree ◽  
Prelingually Deaf

AbstractCochlear implants (CIs) can restore a high degree of functional hearing in deaf patients however spatial hearing remains poor, with many early deaf CI users reported to have no measurable sensitivity to interaural time differences (ITDs) at all. Deprivation of binaural experience during an early critical period is often blamed for this shortcoming. However, we show that neonatally deafened rats provided with precisely synchronized CI stimulation in adulthood can be trained to localize ITDs with essentially normal behavioral thresholds near 50 μs. Furthermore, neonatally deaf rats show high physiological sensitivity to ITDs immediately after binaural implantation in adulthood. The fact that our neonatally deaf CI rats achieved very good behavioral ITD thresholds while prelingually deaf human CI patients usually fail to develop a useful sensitivity to ITD raises urgent questions about whether shortcomings in technology or treatment may be behind the usually poor binaural outcomes for current binaural CI patients.

scholarly journals Microsecond interaural time difference discrimination restored by cochlear implants after neonatal deafness

eLife ◽  
2021 ◽  
Vol 10 ◽  
Author(s):  
Nicole Rosskothen-Kuhl ◽  
Alexa N Buck ◽  
Kongyan Li ◽  
Jan W H Schnupp
Keyword(s):  
Cochlear Implant ◽  
Cochlear Implants ◽  
Early Development ◽  
Critical Period ◽  
Interaural Time Difference ◽  
Spatial Hearing ◽  
Time Difference ◽  
Interaural Time Differences ◽  
Behavioral Thresholds ◽  
Essentially Normal

Spatial hearing in cochlear implant (CI) patients remains a major challenge with many early deaf users reported to have no measurable sensitivity to interaural time differences (ITDs). Deprivation of binaural experience during an early critical period is often hypothesized to be the cause of this shortcoming. However, we show that neonatally deafened (ND) rats provided with precisely synchronized CI stimulation in adulthood can be trained to lateralize ITDs with essentially normal behavioral thresholds near 50 μs. Furthermore, comparable ND rats show high physiological sensitivity to ITDs immediately after binaural implantation in adulthood. Our result that ND CI rats achieved very good behavioral ITD thresholds while prelingually deaf human CI patients often fail to develop a useful sensitivity to ITD raises urgent questions concerning the possibility that shortcomings in technology or treatment, rather than missing input during early development, may be behind the usually poor binaural outcomes for current CI patients.

scholarly journals Linear summation in the barn owl's brainstem underlies responses to interaural time differences

2013 ◽  
Vol 110 (1) ◽  
pp. 117-130 ◽  
Author(s):  
Paula T. Kuokkanen ◽  
Go Ashida ◽  
Catherine E. Carr ◽  
Hermann Wagner ◽  
Richard Kempter
Keyword(s):  
Interaural Time Difference ◽  
Field Potential ◽  
Time Difference ◽  
Linear Summation ◽  
Interaural Time Differences ◽  
Synaptic Potentials ◽  
Binaural Stimulation ◽  
Nonlinear Responses ◽  
Model Predictions ◽  
Primary Origin

The neurophonic potential is a synchronized frequency-following extracellular field potential that can be recorded in the nucleus laminaris (NL) in the brainstem of the barn owl. Putative generators of the neurophonic are the afferent axons from the nucleus magnocellularis, synapses onto NL neurons, and spikes of NL neurons. The outputs of NL, i.e., action potentials of NL neurons, are only weakly represented in the neurophonic. Instead, the inputs to NL, i.e., afferent axons and their synaptic potentials, are the predominant origin of the neurophonic (Kuokkanen PT, Wagner H, Ashida G, Carr CE, Kempter R. J Neurophysiol 104: 2274–2290, 2010). Thus in NL the monaural inputs from the two brain sides converge and create a binaural neurophonic. If these monaural inputs contribute independently to the extracellular field, the response to binaural stimulation can be predicted from the sum of the responses to ipsi- and contralateral stimulation. We found that a linear summation model explains the dependence of the responses on interaural time difference as measured experimentally with binaural stimulation. The fit between model predictions and data was excellent, even without taking into account the nonlinear responses of NL coincidence detector neurons, although their firing rate and synchrony strongly depend on the interaural time difference. These results are consistent with the view that the afferent axons and their synaptic potentials in NL are the primary origin of the neurophonic.

Tuning to Interaural Time Difference and Frequency Differs Between the Auditory Arcopallium and the External Nucleus of the Inferior Colliculus

2009 ◽  
Vol 101 (5) ◽  
pp. 2348-2361 ◽  
Author(s):  
Katrin Vonderschen ◽  
Hermann Wagner
Keyword(s):  
Inferior Colliculus ◽  
Tuning Curve ◽  
Interaural Time Difference ◽  
Low Frequency ◽  
Steep Slope ◽  
Time Difference ◽  
Interaural Time Differences ◽  
Tuning Curves ◽  
Barn Owls ◽  
Zero Time

Barn owls process sound-localization information in two parallel pathways, the midbrain and the forebrain pathway. Exctracellular recordings of neural responses to auditory stimuli from far advanced stations of these pathways, the auditory arcopallium in the forebrain and the external nucleus of the inferior colliculus in the midbrain, demonstrated that the representations of interaural time difference and frequency in the forebrain pathway differ from those in the midbrain pathway. Specifically, low-frequency representation was conserved in the forebrain pathway, while it was lost in the midbrain pathway. Variation of interaural time difference yielded symmetrical tuning curves in the midbrain pathway. By contrast, the typical forebrain-tuning curve was asymmetric with a steep slope crossing zero time difference and a less-steep slope toward larger contralateral time disparities. Low sound frequencies contributed sensitivity to contralateral leading sounds underlying these asymmetries, whereas high frequencies enhanced the steepness of slopes at small interaural time differences. Furthermore, the peaks of time-disparity tuning curves were wider in the forebrain than in the midbrain. The distribution of the steepest slopes of best interaural time differences in the auditory arcopallium, but not in the external nucleus of the inferior colliculus, was centered at zero time difference. The distribution observed in the auditory arocpallium is reminiscent of the situation observed in small mammals. We speculate that the forebrain representation may serve as a population code supporting fine discrimination of central interaural time differences and coarse indication of laterality of a stimulus for large interaural time differences.

The Effect of Spatially Separated Sound Sources on Speech Intelligibility

1969 ◽  
Vol 12 (1) ◽  
pp. 5-38 ◽  
Author(s):  
Donald D. Dirks ◽  
Richard H. Wilson
Keyword(s):  
Speech Intelligibility ◽  
Rank Order ◽  
Interaural Time Difference ◽  
Sound Field ◽  
Spatial Separation ◽  
Spatial Location ◽  
Time Difference ◽  
Noise Sources ◽  
Sound Sources ◽  
Interaural Time Differences

A series of five experiments was conducted to investigate the effects of spatial separation of speakers on the intelligibility of spondaic and PB words in noise and the identification of synthetic sentences in noise and competing message. Conditions in which the spatial location of the speakers produced interaural time differences ranked highest in intelligibility. The rank order of other conditions was dependent on the S/N ratio at the monaural near ear. Separations of only 10° between the speech and noise sources resulted in measurable changes in intelligibility. The binaural intelligibility scores were enhanced substantially over the monaural near ear results during conditions where an interaural time difference was present. This result was observed more effectively when spondaic words or sentences were used rather than PB words. The implications of this result were related to the interaural time difference and the frequency range of the critical information in the primary message. Although the initial experiments were facilitated by recording through an artificial head, almost identical results were obtained in the final experiment when subjects were tested in the sound field.

scholarly journals Interaural place-of-stimulation mismatch estimates using CT scans and binaural perception, but not pitch, are consistent in cochlear-implant users

2021 ◽  
Author(s):  
Joshua G. W. Bernstein ◽  
Kenneth K. Jensen ◽  
Olga A. Stakhovskaya ◽  
Jack H. Noble ◽  
Michael Hoa ◽  
...  
Keyword(s):  
Cochlear Implants ◽  
Interaural Time Difference ◽  
Spatial Hearing ◽  
Ct Scans ◽  
Bilateral Stimulation ◽  
Electrode Arrays ◽  
Frequency Information ◽  
Binaural Processing ◽  
Ct Measurements ◽  
Hearing Abilities

ABSTRACTBilateral cochlear implants (BI-CIs) or a CI for single-sided deafness (SSD; one normally functioning acoustic ear) can partially restore spatial-hearing abilities including sound localization and speech understanding when there are competing sounds. However for these populations, frequency information is not explicitly aligned across the ears, resulting in interaural place-of-stimulation mismatch. This diminishes spatial-hearing abilities because binaural encoding occurs in interaurally frequency-matched neurons. This study examined whether plasticity – the reorganization of central neural pathways over time – can compensate for peripheral interaural place mismatch. We hypothesized differential plasticity across two systems: none for binaural processing but adaptation toward the frequencies delivered by the specific electrodes for sequential pitch perception. Interaural place mismatch was evaluated in 43 human subjects (20 BI-CI and 23 SSD-CI, both sexes) using interaural-time-difference (ITD) discrimination (simultaneous bilateral stimulation), place-pitch ranking (sequential bilateral stimulation), and physical electrode- location estimates from computed-tomography (CT) scans. On average, CT scans revealed relatively little BI-CI interaural place mismatch (26° insertion-angle mismatch), but relatively large SSD-CI mismatch, particularly at the apical end of the array (166° for an electrode tuned to 300 Hz, decreasing to 14° at 7000 Hz). ITD and CT measurements were in agreement, suggesting little binaural-system plasticity to mismatch. The pitch measurements did not agree with the binaural and CT measurements, suggesting plasticity for pitch encoding or procedural biases. The combined results show that binaural processing may be optimized by using CT-scan information, but not pitch measurements, to program the CI frequency allocation to reduce interaural place mismatch.SIGNIFICANCE STATEMENTPlacement of electrode arrays in users of cochlear implants (CIs; bionic auditory prostheses that partially restore hearing) does not align the frequency information to acoustic neural encoding across the ears. This interaural place-of-stimulation mismatch diminishes spatial hearing abilities. This study shows that for experienced adult CI users with two CIs or with one CI and one normal-hearing ear, the best possible binaural sensitivity occurs when the same cochlear location is stimulated in both ears. This means that binaural brainstem pathways do not experience “plasticity” to compensate for interaural place mismatch – i.e., they do not reorganize to respond to input from different cochlear places. Therefore, explicit correction of interaural place mismatch by a clinician is necessary to derive maximum spatial-hearing benefits.

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