Microsecond interaural time difference discrimination restored by cochlear implants after neonatal deafness
Abstract
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.
Data availability
All data generated or analysed during this study are included in the manuscript and supporting files. Data have been deposited to Dryad, under the DOI 10.5061/dryad.573n5tb6d.
-
Behavioral and ephys data of research paperDryad Digital Repository, doi:10.5061/dryad.573n5tb6d.
Article and author information
Author details
Funding
Deutscher Akademischer Austauschdienst (P.R.I.M.E. - Postdoctoral Researchers International Mobility Experience,REA grant agreement n 605728)
- Nicole Rosskothen-Kuhl
Hong Kong General Research Fund (Hong Kong General Research Fund (11100219))
- Jan W H Schnupp
Deutsche Forschungsgemeinschaft (Cluster of Excellence BrainLinks-BrainTools,Grant number EXC1086)
- Nicole Rosskothen-Kuhl
Taube Kinder lernen hoeren e.V.
- Nicole Rosskothen-Kuhl
Hong Kong (Medical Research Fund (06172296))
- Jan W H Schnupp
Shenzhen Science and Innovation Fund (Shenzhen Science and Innovation Fund (JCYJ20180307124024360))
- Jan W H Schnupp
The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.
Reviewing Editor
- Lina Reiss, Oregon Health and Science University, United States
Ethics
Animal experimentation: All procedures involving experimental animals reported here were approved by the Department of Health of Hong Kong (#16-52 DH/HA&P/8/2/5) or Regierungspräsidium Freiburg (#35-9185.81/G-17/124), as well as by the appropriate local ethical review committee. All surgery was performed under ketamine and xylazine anesthesia, and every effort was made to minimize suffering.
Version history
- Received: June 16, 2020
- Accepted: January 7, 2021
- Accepted Manuscript published: January 11, 2021 (version 1)
- Version of Record published: January 18, 2021 (version 2)
Copyright
© 2021, Rosskothen-Kuhl et al.
This article is distributed under the terms of the Creative Commons Attribution License permitting unrestricted use and redistribution provided that the original author and source are credited.
Metrics
-
- 1,511
- views
-
- 215
- downloads
-
- 24
- citations
Views, downloads and citations are aggregated across all versions of this paper published by eLife.
Download links
Downloads (link to download the article as PDF)
Open citations (links to open the citations from this article in various online reference manager services)
Cite this article (links to download the citations from this article in formats compatible with various reference manager tools)
Further reading
-
- Neuroscience
Abnormal activity in the cerebellar nuclei can be used to predict motor symptoms and induce them experimentally, pointing to potential therapeutic strategies.
-
- Cell Biology
- Neuroscience
One of the most extensively studied members of the Ras superfamily of small GTPases, Rac1 is an intracellular signal transducer that remodels actin and phosphorylation signaling networks. Previous studies have shown that Rac1-mediated signaling is associated with hippocampal-dependent working memory and longer-term forms of learning and memory and that Rac1 can modulate forms of both pre- and postsynaptic plasticity. How these different cognitive functions and forms of plasticity mediated by Rac1 are linked, however, is unclear. Here, we show that spatial working memory in mice is selectively impaired following the expression of a genetically encoded Rac1 inhibitor at presynaptic terminals, while longer-term cognitive processes are affected by Rac1 inhibition at postsynaptic sites. To investigate the regulatory mechanisms of this presynaptic process, we leveraged new advances in mass spectrometry to identify the proteomic and post-translational landscape of presynaptic Rac1 signaling. We identified serine/threonine kinases and phosphorylated cytoskeletal signaling and synaptic vesicle proteins enriched with active Rac1. The phosphorylated sites in these proteins are at positions likely to have regulatory effects on synaptic vesicles. Consistent with this, we also report changes in the distribution and morphology of synaptic vesicles and in postsynaptic ultrastructure following presynaptic Rac1 inhibition. Overall, this study reveals a previously unrecognized presynaptic role of Rac1 signaling in cognitive processes and provides insights into its potential regulatory mechanisms.