In nonlinear systems, the inclusion of low-level noise can paradoxically improve signal detection, a phenomenon known as stochastic resonance (SR). SR has been observed in human hearing whereby sensory thresholds (e.g., signal detection and discrimination) are enhanced in the presence of noise. Here, we asked whether subcortical auditory processing (neural phase locking) shows evidence of SR. We recorded brainstem frequency-following-responses (FFRs) in young, normal-hearing listeners to near-electrophysiological-threshold (40 dB SPL) complex tones composed of 10 iso-amplitude harmonics of 150 Hz fundamental frequency (F0) presented concurrent with low-level noise (+20 to −20 dB SNRs). Though variable and weak across ears, some listeners showed improvement in auditory detection thresholds with subthreshold noise confirming SR psychophysically. At the neural level, low-level FFRs were initially eradicated by noise (expected masking effect) but were surprisingly reinvigorated at select masker levels (local maximum near ∼ 35 dB SPL). These data suggest brainstem phase-locking to near threshold periodic stimuli is enhanced in optimal levels of noise, the hallmark of SR. Our findings provide novel evidence for stochastic resonance in the human auditory brainstem and suggest that under some circumstances, noise can actually benefit both the behavioral and neural encoding of complex sounds.

在非线性系统中，包含低电平噪声反而会改善信号检测，这种现象称为随机共振 (SR)。已经在人类听力中观察到 SR，从而在存在噪声的情况下增强感觉阈值（例如，信号检测和辨别）。在这里，我们询问皮层下听觉处理（神经相位锁定）是否显示 SR 的证据。我们记录了年轻、听力正常的听众对由 10 iso组成的近电生理阈值 (40 dB SPL) 复杂音调的脑干频率跟随反应 (FFR)- 150 Hz 基频 (F0) 的振幅谐波与低电平噪声（+20 至 −20 dB SNR）同时出现。尽管耳朵之间存在差异且较弱，但一些听众表现出听觉检测阈值的改善，亚阈值噪声从心理物理学上证实了 SR。在神经层面，低水平 FFR 最初被噪声消除（预期的掩蔽效应），但在选择掩蔽水平（局部最大值接近 ~ 35 dB SPL）时出人意料地重新焕发活力。这些数据表明，在最佳噪声水平下，脑干对接近阈值周期性刺激的锁相得到增强，这是 SR 的标志。我们的研究结果为人类听觉脑干中的随机共振提供了新的证据，并表明在某些情况下，噪音实际上可以有益于复杂声音的行为和神经编码。