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bioRxiv · 10.1101/2025.03.07.642101

Mechanisms of Tone-in-Noise Encoding in the Inferior Colliculus

Fritzinger, J. B.·Carney, L. H.
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Abstract

Extracellular single-unit responses to tone-in-noise (TIN) stimuli were recorded in the inferior colliculus (IC) of awake female Dutch-belted rabbits. Stimuli consisted of wideband and narrowband tone-in-noise (TIN) with on-and off-characteristic frequency tones. Neural responses to wideband TIN showed a pattern of rates that increased when the tone matched CF and decreased (with respect to noise-alone responses) when the tone was above or below CF. This result differed from narrowband TIN IC responses that depended on envelope fluctuations in the stimulus, consistent with neural-fluctuation sensitivity. The WB-TIN responses could be fit with a difference-of-gaussians model that had narrow excitation and broad inhibition; responses to TIN could not be predicted by response-maps or spectrotemporal receptive fields. Responses to diotic and contralateral presentations of WB-TIN did not differ due to presentation ear. A single-CF computational model of the IC could not predict responses to wideband TIN. However, adding local off-CF inhibitory inputs to an on-CF IC model improved accuracy. These results suggest that broad inhibition could explain encoding of wideband TIN at suprathreshold signal-to-noise ratios, whereas neural fluctuation sensitivity is more important for narrowband sounds.

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Fritzinger, J. B., Carney, L. H.. 2025-03-10. Mechanisms of Tone-in-Noise Encoding in the Inferior Colliculus. https://doi.org/10.1101/2025.03.07.642101

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