AG Neuroakustik, Carl von Ossietzky Universität, Oldenburg, Germany.
Neuroimage. 2010 Jan 1;49(1):835-42. doi: 10.1016/j.neuroimage.2009.07.014. Epub 2009 Jul 17.
The aim of the present study was to find a functional MRI correlate in human auditory cortex of the psychoacoustical effect of release from masking, using amplitude-modulated noise stimuli. A sinusoidal target signal was embedded in a band-limited white noise, which was either unmodulated or (co)modulated. Psychoacoustical thresholds were measured for the target signals in both types of masking noise, using an adaptive procedure. The mean threshold difference between the unmodulated and the comodulated condition, i.e., the release from masking, was 15 dB. The same listeners then participated in an fMRI experiment, recording activation of auditory cortex in response to tones in the presence of modulated and unmodulated noise maskers at five different signal-to-noise ratios. In general, a spatial dissociation of changes of overall level and signal-to-noise ratio in auditory cortex was found, replicating a previous fMRI study on pure-tone masking. The comparison of the fMRI activation maps for a signal presented in modulated and in unmodulated noise reveals that those regions in the antero-lateral part of Heschl's gyrus previously shown to represent the audibility of a tonal target (rather than overall level) exhibit a stronger activation for the modulated than for the unmodulated conditions. This result is interpreted as a physiological correlate of the psychoacoustical effect of comodulation masking release at the level of the auditory cortex.
本研究旨在通过使用调制噪声刺激，在人类听觉皮层中找到释放掩蔽的心理声学效应的功能磁共振成像（fMRI）相关物。正弦目标信号嵌入在带限白噪声中，该噪声要么未调制，要么（共）调制。使用自适应程序测量了两种掩蔽噪声中目标信号的心理声学阈值。即，未调制与共调制条件之间的平均阈值差，也就是掩蔽释放，为 15dB。然后，相同的听众参与了 fMRI 实验，在调制和未调制噪声掩蔽器存在的情况下，记录了听觉皮层对音调的激活情况，在五个不同的信噪比下。总的来说，在听觉皮层中发现了整体水平和信噪比变化的空间分离，这与以前关于纯音掩蔽的 fMRI 研究相吻合。对调制噪声和未调制噪声中呈现的信号的 fMRI 激活图进行比较，表明先前显示出代表音调目标可听性（而不是整体水平）的赫希氏回前外侧区域的那些区域对于调制条件的激活比未调制条件更强。该结果被解释为听觉皮层水平上共调制掩蔽释放的心理声学效应的生理相关物。
