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Temporal hyper-precision of brainstem neurons alters spatial sensitivity of binaural auditory processing with
Michaela Müller1, Hongmei Hu2,3, Mathias Dietz2,3
1Graduate School of Systemic Neurosciences, Ludwig-Maximilians-Universität, Munich, Germany.
Frontiers in Neuroscience
|January 23, 2023
Summary
Cochlear implants (CIs) improve hearing but impair sound localization. Electrical stimulation causes hyper-precise neural inputs, altering spatial hearing. Reducing this precision may restore sound localization for CI users.
Area of Science:
- Neuroscience
- Auditory system research
- Biomedical engineering
Background:
- Spatial hearing, crucial for communication and navigation, relies on interaural time differences (ITDs).
- Cochlear implants (CIs) restore hearing but often fail to restore accurate sound localization via ITD detection.
- The neural basis for poor ITD sensitivity in CI users is unclear, with deficits potentially arising at the input or processing stages.
Purpose of the Study:
- To investigate the impact of electrical stimulation on brainstem auditory inputs in a cochlear implant model.
- To compare neural response characteristics between electrical and acoustic stimulation.
- To model the consequences of altered neural inputs on interaural time difference sensitivity and spatial hearing.
Main Methods:
- Extracellular single neuron recordings in gerbils to compare brainstem responses to electrical and acoustic stimulation.
- Utilized a computational model of the auditory brainstem, tuned to physiological data, to predict ITD sensitivity.
- Simulated effects of altered input precision on spatial sensitivity in the computational model.
Main Results:
- Electrical stimulation induced severe hyper-precision and moderate hyper-entrainment in brainstem inputs to binaural comparator neurons.
- Computational modeling predicted maintained ITD sensitivity but severely altered spatial sensitivity with electrical stimulation.
- Reduced input precision in the model recovered a wider range of separable ITDs, mimicking findings in CI users.
Conclusions:
- The binaural processing stage in CI users must contend with significantly altered input statistics due to electrical stimulation.
- Temporal hyper-precision of inputs, induced by electrical stimulation, is a likely central cause of diminished ITD sensitivity in CI users.
- Strategies to mitigate neural hyper-precision may improve sound localization capabilities for individuals with cochlear implants.
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