Androulidakis A G, Jones S J
Sobell Department of Motor Neuroscience and Movement Disorders, Institute of Neurology, University College London, 8-11 Queen Square, London WC1N 3BG, UK.
Clin Neurophysiol. 2006 Aug;117(8):1783-93. doi: 10.1016/j.clinph.2006.04.011. Epub 2006 Jun 21.
To investigate a neurophysiological correlate of the perceptual enhancement of noise-masked sounds when the masking frequencies have a wide spectral bandwidth and are coherently amplitude-modulated.
Auditory evoked potentials were recorded to 1 kHz tones (200 ms, 61 dBSPL, SOA 3s) occurring in silence or with 80 dB masking noise, which was either wide-band or narrow-band and either unmodulated or 100% amplitude-modulated by a 17.5 Hz square-wave. In a second study, the tones were timed to coincide alternately with the rise and fall of the masker envelope.
N1 and P2 potentials recorded to the unmasked tones were abolished in the presence of the unmodulated masker, but were elicited again with lower amplitude and longer latency when the masker was modulated. No significant effect of the masker bandwidth was observed. Latencies were strongly determined by whether the tones coincided with the rise or fall of the masker envelope, indicating that the responses were only evoked when the instantaneous noise level was low.
The findings demonstrate partial correspondence to the threshold reduction to similar stimuli seen in comodulation masking release (CMR). The dependence of latencies on the phase of the masker envelope is consistent with the 'dip-listening' model of CMR.
Under these conditions the N1/P2 complex can be viewed as a possible neurophysiological correlate of perceptual CMR.
研究当掩蔽频率具有宽频谱带宽且进行相干幅度调制时，噪声掩蔽声音的感知增强的神经生理学关联。
记录在安静环境中或存在80 dB掩蔽噪声（宽带或窄带，未调制或由17.5 Hz方波进行100%幅度调制）时，对1 kHz纯音（200 ms，61 dBSPL，刺激间隔3 s）的听觉诱发电位。在第二项研究中，使纯音的时间交替与掩蔽器包络的上升和下降同步。
在未调制掩蔽器存在时，记录到的未掩蔽纯音的N1和P2电位消失，但当掩蔽器调制时，以较低幅度和较长潜伏期再次引出。未观察到掩蔽器带宽的显著影响。潜伏期强烈取决于纯音是否与掩蔽器包络的上升或下降同步，表明仅在瞬时噪声水平较低时才诱发反应。
这些发现表明与在共调制掩蔽释放（CMR）中观察到的对类似刺激的阈值降低部分对应。潜伏期对掩蔽器包络相位的依赖性与CMR的“低谷聆听”模型一致。
在这些条件下，N1/P2复合体可被视为感知CMR的一种可能的神经生理学关联。
