Max Planck Research Group "Auditory Cognition," Max Planck Institute for Human Cognitive and Brain Sciences Leipzig, Germany.
Department of Neurology, Max Planck Institute for Human Cognitive and Brain Sciences Leipzig, Germany.
Front Neurosci. 2014 Jun 4;8:137. doi: 10.3389/fnins.2014.00137. eCollection 2014.
Optimal utilization of acoustic cues during auditory categorization is a vital skill, particularly when informative cues become occluded or degraded. Consequently, the acoustic environment requires flexible choosing and switching amongst available cues. The present study targets the brain functions underlying such changes in cue utilization. Participants performed a categorization task with immediate feedback on acoustic stimuli from two categories that varied in duration and spectral properties, while we simultaneously recorded Blood Oxygenation Level Dependent (BOLD) responses in fMRI and electroencephalograms (EEGs). In the first half of the experiment, categories could be best discriminated by spectral properties. Halfway through the experiment, spectral degradation rendered the stimulus duration the more informative cue. Behaviorally, degradation decreased the likelihood of utilizing spectral cues. Spectrally degrading the acoustic signal led to increased alpha power compared to nondegraded stimuli. The EEG-informed fMRI analyses revealed that alpha power correlated with BOLD changes in inferior parietal cortex and right posterior superior temporal gyrus (including planum temporale). In both areas, spectral degradation led to a weaker coupling of BOLD response to behavioral utilization of the spectral cue. These data provide converging evidence from behavioral modeling, electrophysiology, and hemodynamics that (a) increased alpha power mediates the inhibition of uninformative (here spectral) stimulus features, and that (b) the parietal attention network supports optimal cue utilization in auditory categorization. The results highlight the complex cortical processing of auditory categorization under realistic listening challenges.
在听觉分类中最佳利用声学线索是一项至关重要的技能，特别是在信息性线索被遮挡或降级时。因此，声学环境需要灵活地选择和切换可用线索。本研究旨在探讨大脑在这种线索利用变化背后的功能。参与者在一项分类任务中，对来自两个类别的声学刺激进行即时反馈，这些刺激在持续时间和频谱特性上有所不同，同时我们在 fMRI 和脑电图（EEG）中同时记录血氧水平依赖（BOLD）反应。在实验的前半部分，类别可以通过频谱特性最佳区分。实验进行到一半时，频谱降级使刺激持续时间成为更具信息量的线索。行为上，降级降低了利用频谱线索的可能性。与非降级刺激相比，频谱降级会导致 alpha 功率增加。基于 EEG 的 fMRI 分析显示，alpha 功率与下顶叶皮层和右侧后颞上回（包括颞平面）的 BOLD 变化相关。在这两个区域，频谱降级导致 BOLD 反应与行为上利用频谱线索的耦合减弱。这些数据从行为建模、电生理学和血液动力学提供了一致的证据，表明 (a) 增加的 alpha 功率介导了对无信息（这里是频谱）刺激特征的抑制，以及 (b) 顶叶注意网络支持听觉分类中的最佳线索利用。结果突出了在现实听力挑战下听觉分类的复杂皮质处理。
