Bee Mark A, Buschermöhle Michael, Klump Georg M
Department of Ecology, Evolution, and Behavior, University of Minnesota, St Paul, MN 55108, USA.
Eur J Neurosci. 2007 Oct;26(7):1979-94. doi: 10.1111/j.1460-9568.2007.05805.x.
Sounds in the real world fluctuate in amplitude. The vertebrate auditory system exploits patterns of amplitude fluctuations to improve signal detection in noise. One experimental paradigm demonstrating these general effects has been used in psychophysical studies of 'comodulation detection difference' (CDD). The CDD effect refers to the fact that thresholds for detecting a modulated, narrowband noise signal are lower when the envelopes of flanking bands of modulated noise are comodulated with each other, but fluctuate independently of the signal compared with conditions in which the envelopes of the signal and flanking bands are all comodulated. Here, we report results from a study of the neural correlates of CDD in European starlings (Sturnus vulgaris). We manipulated: (i) the envelope correlations between a narrowband noise signal and a masker comprised of six flanking bands of noise; (ii) the signal onset delay relative to masker onset; (iii) signal duration; and (iv) masker spectrum level. Masked detection thresholds were determined from neural responses using signal detection theory. Across conditions, the magnitude of neural CDD ranged between 2 and 8 dB, which is similar to that reported in a companion psychophysical study of starlings [U. Langemann & G.M. Klump (2007) Eur. J. Neurosci., 26, 1969-1978]. We found little evidence to suggest that neural CDD resulted from the across-channel processing of auditory grouping cues related to common envelope fluctuations and synchronous onsets between the signal and flanking bands. We discuss a within-channel model of peripheral processing that explains many of our results.
现实世界中的声音在幅度上会发生波动。脊椎动物的听觉系统利用幅度波动模式来提高在噪声中检测信号的能力。一种展示这些一般效应的实验范式已被用于“共调制检测差异”（CDD）的心理物理学研究中。CDD效应指的是这样一个事实：当调制噪声的侧翼带的包络相互共调制，但与信号相比独立波动时，检测调制窄带噪声信号的阈值要低于信号和侧翼带的包络都被共调制的情况。在此，我们报告了一项关于欧洲椋鸟（Sturnus vulgaris）中CDD的神经相关性研究的结果。我们操纵了：（i）窄带噪声信号与由六个噪声侧翼带组成的掩蔽声之间的包络相关性；（ii）信号相对于掩蔽声起始的延迟；（iii）信号持续时间；以及（iv）掩蔽声声谱水平。使用信号检测理论根据神经反应确定掩蔽检测阈值。在各种条件下，神经CDD的幅度在2到8分贝之间，这与在一项关于椋鸟的配套心理物理学研究中报告的结果相似[U. 朗格曼 & G.M. 克伦普（2007年）《欧洲神经科学杂志》，26，1969 - 1978]。我们几乎没有发现证据表明神经CDD是由与信号和侧翼带之间的共同包络波动和同步起始相关的听觉分组线索的跨通道处理导致的。我们讨论了一个外周处理的通道内模型，该模型解释了我们的许多结果。
