Zhang Min, Alamatsaz Nima, Ihlefeld Antje
Department of Biomedical Engineering, New Jersey Institute of Technology, Newark, NJ, United States.
Rutgers Biomedical and Health Sciences, Rutgers University, Newark, NJ, United States.
Front Neurosci. 2021 Jul 22;15:675326. doi: 10.3389/fnins.2021.675326. eCollection 2021.
Suppressing unwanted background sound is crucial for aural communication. A particularly disruptive type of background sound, informational masking (IM), often interferes in social settings. However, IM mechanisms are incompletely understood. At present, IM is identified operationally: when a target should be audible, based on suprathreshold target/masker energy ratios, yet cannot be heard because target-like background sound interferes. We here confirm that speech identification thresholds differ dramatically between low- vs. high-IM background sound. However, speech detection thresholds are comparable across the two conditions. Moreover, functional near infrared spectroscopy recordings show that task-evoked blood oxygenation changes near the superior temporal gyrus (STG) covary with behavioral speech detection performance for high-IM but not low-IM background sound, suggesting that the STG is part of an IM-dependent network. Moreover, listeners who are more vulnerable to IM show increased hemodynamic recruitment near STG, an effect that cannot be explained based on differences in task difficulty across low- vs. high-IM. In contrast, task-evoked responses near another auditory region of cortex, the caudal inferior frontal sulcus (cIFS), do not predict behavioral sensitivity, suggesting that the cIFS belongs to an IM-independent network. Results are consistent with the idea that cortical gating shapes individual vulnerability to IM.
抑制不需要的背景声音对于听觉交流至关重要。一种特别具有干扰性的背景声音类型，即信息掩蔽（IM），常常在社交场合中产生干扰。然而，IM机制尚未被完全理解。目前，IM是通过操作来识别的：当根据阈上目标/掩蔽能量比目标应该是可听的，但却因为类似目标的背景声音干扰而无法被听到时。我们在此证实，在低IM背景声音与高IM背景声音之间，语音识别阈值存在显著差异。然而，在这两种情况下语音检测阈值是可比的。此外，功能近红外光谱记录显示，对于高IM背景声音而非低IM背景声音，颞上回（STG）附近任务诱发的血氧变化与行为语音检测性能共变，这表明STG是IM依赖网络的一部分。此外，更容易受到IM影响的听众在STG附近显示出血流动力学募集增加，这种效应无法基于低IM与高IM之间任务难度的差异来解释。相比之下，在另一个听觉皮层区域，即尾侧额下回沟（cIFS）附近的任务诱发反应并不能预测行为敏感性，这表明cIFS属于IM独立网络。结果与皮质门控塑造个体对IM易感性的观点一致。
