Physiological and Computational-Modeling Studies of Timbre Encoding in the Inferior Colliculus

下丘音色编码的生理学和计算模型研究

• 批准号: 10604855
• 负责人: Johanna Fritzinger
• 金额: $ 4.68万
• 依托单位: UNIVERSITY OF ROCHESTER
• 依托单位国家: 美国
• 财政年份: 2022
• 资助国家: 美国
• 起止时间: 2022-09-01 至 2025-08-31
• 项目状态: 未结题
• 来源: https://reporter.nih.gov/project-details/10604855
• 关键词: Acoustic Nerve; Area; Auditory; Auditory system; Brain Stem; Cells; Characteristics; Cochlear Implants; Code; Communication; Complex; Comprehension; Computer Models; Contralateral; Data; Fiber; Frequencies; Hearing Aids; Inferior Colliculus; Inner Hair Cells; Lead; Masks; Midbrain structure; Modeling; Music; Nerve Fibers; Neuraxis; Neurons; Noise; Oryctolagus cuniculus; Perception; Peripheral; Phase; Physiological; Play; Population; Psychophysics; Public Health; Research; Research Project Grants; Signal Transduction; Source; Speech; Stimulus; Study models; Testing; Thalamic structure; Update; Variant; Work; awake; base; design; experimental study; extracellular; improved; insight; instrument; neural model; novel; novel strategies; physiologic model; relating to nervous system; response; sound; training opportunity

Timbre, the quality that allows sounds to be distinguished when they are identical in pitch, level, and duration, is a critical aspect of speech comprehension and music enjoyment. My proposal will fill a gap in neural studies of timbre by testing the hypothesis that capture and off-CF inhibitory mechanisms lead to robust representations of suprathreshold synthetic and natural-instrument timbre in the midbrain. To test my hypothesis, I will record single-unit inferior colliculus (IC) responses from awake Dutch-belted rabbits. I will also develop a new computational IC model based on these physiological responses. Spectral envelopes of harmonic sounds are correlated with the timbral perception of “brightness”. I propose two mechanisms that contribute to spectral-envelope encoding: capture and off-characteristic frequency (CF) inhibition. The first mechanism, capture, refers to the dominance of harmonics near spectral peaks over auditory-nerve fibers tuned near the peaks. Capture is due to saturation of inner hair cells. Capture by a single harmonic reduces the amplitude of low-frequency neural fluctuations in auditory-nerve fibers. Rates of IC neurons are sensitive to low-frequency neural fluctuations as characterized by modulation transfer functions. Ultimately, capture of auditory-nerve responses for fibers tuned near spectral peaks results in IC rate profiles that encode spectral peaks. Preliminary results are partially consistent with spectral peaks of synthetic timbre stimuli capturing peripheral responses, leading to a rate representation of salient spectral features in the midbrain. However, another mechanism that could explain IC representations of timbre is off-CF inhibition, which has been proposed to explain frequency-sweep sensitivity and psychophysical forward masking. A subcortical computational model that features capture, but not off-CF inhibition, was able to predict preliminary responses to synthetic timbre and narrowband tone-in-noise, but could not predict responses to wideband tone-in-noise or natural timbre, indicating the need to update the model. I have developed experiments to test the hypothesis that timbre is robustly encoded in the midbrain via capture and off-CF inhibition. Aim 1.1 will test the hypothesis that responses to wideband tone-in-noise are strongly influenced by off-CF inhibition, and reducing the noise bandwidth increases the influence of capture. In Aim 1.2 I will update a computational IC model by adding off-CF inhibition to test the hypothesis that capture and off-CF inhibition are necessary to explain tone-in-noise stimuli. Aim 2.1 will test the hypothesis that the spectral peak of a shaped harmonic complex, synthetic timbre, is robustly encoded in the IC over a range of suprathreshold sound levels. Aim 2.2 bridges the gap between synthetic and natural timbre by recording responses to real instrument sounds. Responses from Aim 2 will further test the new IC model. This project will provide insight on the IC representation of suprathreshold timbre. This research will lead to novel strategies to restore timbre perception in hearing aids and cochlear implants, which are not designed for timbre perception.

音色，当声音在音高、水平和音质上相同时， 持续时间是言语理解和音乐欣赏的关键方面。我的提议将填补神经科学的空白 音色的研究，通过测试的假设，捕获和关闭CF抑制机制导致强大的 阈上合成和自然乐器音色在中脑的表现。为了验证我的假设， 我将记录清醒荷兰带兔的单个单位下丘（IC）反应。我还将开发一个 新的计算IC模型基于这些生理反应。 谐波声音的频谱包络与“亮度”的音色感知相关。我 提出了两种有助于频谱包络编码的机制：捕获和非特征频率 (CF)抑制作用第一种机制，捕获，指的是频谱峰值附近的谐波占主导地位， 神经纤维在峰值附近调谐。捕获是由于内毛细胞的饱和。由一个单一的捕获 谐波降低了神经纤维中低频神经波动的幅度。IC费率 神经元对由调制传递函数表征的低频神经波动敏感。 最后，捕获调谐在光谱峰值附近的纤维的神经反应，导致IC速率曲线 编码频谱峰值的初步结果与合成音色的谱峰部分一致 刺激捕捉周边反应，导致率代表显着的频谱特征，在 中脑然而，另一种可以解释音色的IC表征的机制是关闭CF抑制， 已经提出来解释频率扫描灵敏度和心理物理前向掩蔽。皮层下 一个以捕获为特征的计算模型，而不是非CF抑制，能够预测初步的反应 合成音色和窄带音噪声，但不能预测响应宽带音噪声或 音色自然，表示需要更新模型。 我已经开发了实验来测试这一假设，即音色是在中脑中通过 捕获和关闭CF抑制。目标1.1将检验对宽带噪声中的音调的响应是 受关闭CF抑制的强烈影响，并且降低噪声带宽增加了捕获的影响。在 目的1.2我将通过添加关闭CF抑制来更新计算IC模型，以检验捕获和 关闭CF抑制对于解释噪音中的音调刺激是必要的。目标2.1将检验光谱 成形的谐波复合物的峰值，合成音色，在IC中在一个范围内被鲁棒地编码， 阈上声级Aim 2.2通过录音弥合了合成音色和自然音色之间的差距 对真实的乐器声音的反应。目标2的回应将进一步测试新的IC模型。该项目将 提供有关阈上音色的IC表现的见解。这项研究将导致新的战略， 在助听器和人工耳蜗中恢复音色感知，这不是为音色感知而设计的。