Effects of Signal-to-Noise Ratio on Auditory Cortical Frequency Processing
Effects of Signal-to-Noise Ratio on Auditory Cortical Frequency Processing
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DOI：
10.1523/jneurosci.2079-15.2016
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发表时间：
2016-03
期刊：
影响因子：
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通讯作者：
Magnus J Teschner;B. Seybold;B. Malone;Jana Hüning;C. Schreiner
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文献类型：
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作者：
Magnus J Teschner;B. Seybold;B. Malone;Jana Hüning;C. Schreiner
在听觉系统中存在背景噪声的情况下，支持声信号鲁棒处理的神经机制在很大程度上仍然没有得到解决。心理物理学实验表明，信号检测受到信噪比（SNR）和整体刺激水平的影响，但这种关系尚未得到充分表征。我们通过构建不同信噪比、音调水平和噪声水平下大鼠初级听觉皮层的音调频率反应区（FRA）来评价大鼠初级听觉皮层频率的神经表征。我们发现，响应强度和选择性的频率和声音水平取决于信噪比和音调水平之间的相互作用。在低SNR时，联合增加音调和噪声水平降低了发射率并缩小了FRA带宽;然而，在较高SNR时，增加音调和噪声水平增加了发射率并扩大了带宽，如通常在没有背景噪声的情况下获得的FRA所见。这些频率和强度调谐的变化降低了在低SNR时的音调水平和音调频率辨别力。相比之下，无论是响应起始延迟还是噪声驱动的稳态放电率都与SNR或整体声级没有意义的相互作用。人类的语音检测性能也被证明取决于整体声级和SNR之间的相互作用。总之，这些结果表明，由高噪声水平造成的信号处理困难是相当普遍的，并表明我们在简单声音中看到的神经生理学变化可以推广到更复杂的刺激。在背景噪声中有效地处理声音是哺乳动物听觉系统的一个重要特征，也是在许多听力条件下成功听力的必要特征。即使是轻微的听力损失也会严重影响人类的这种能力，严重降低沟通能力。在背景噪声中实现高性能所涉及的机制还没有得到很好的理解。研究了信噪比和总刺激水平对大鼠初级听皮层神经元频率调谐的影响。我们发现，噪声对频率选择性的影响不仅取决于信噪比，而且还取决于前景音调和背景噪声的水平。这些观察结果可以改善听力受损患者的治疗方法。
The neural mechanisms that support the robust processing of acoustic signals in the presence of background noise in the auditory system remain largely unresolved. Psychophysical experiments have shown that signal detection is influenced by the signal-to-noise ratio (SNR) and the overall stimulus level, but this relationship has not been fully characterized. We evaluated the neural representation of frequency in rat primary auditory cortex by constructing tonal frequency response areas (FRAs) in primary auditory cortex for different SNRs, tone levels, and noise levels. We show that response strength and selectivity for frequency and sound level depend on interactions between SNRs and tone levels. At low SNRs, jointly increasing the tone and noise levels reduced firing rates and narrowed FRA bandwidths; at higher SNRs, however, increasing the tone and noise levels increased firing rates and expanded bandwidths, as is usually seen for FRAs obtained without background noise. These changes in frequency and intensity tuning decreased tone level and tone frequency discriminability at low SNRs. By contrast, neither response onset latencies nor noise-driven steady-state firing rates meaningfully interacted with SNRs or overall sound levels. Speech detection performance in humans was also shown to depend on the interaction between overall sound level and SNR. Together, these results indicate that signal processing difficulties imposed by high noise levels are quite general and suggest that the neurophysiological changes we see for simple sounds generalize to more complex stimuli. SIGNIFICANCE STATEMENT Effective processing of sounds in background noise is an important feature of the mammalian auditory system and a necessary feature for successful hearing in many listening conditions. Even mild hearing loss strongly affects this ability in humans, seriously degrading the ability to communicate. The mechanisms involved in achieving high performance in background noise are not well understood. We investigated the effects of SNR and overall stimulus level on the frequency tuning of neurons in rat primary auditory cortex. We found that the effects of noise on frequency selectivity are not determined solely by the SNR but depend also on the levels of the foreground tones and background noise. These observations can lead to improvement in therapeutic approaches for hearing-impaired patients.