The Brain and Mind Institute, The University of Western Ontario, London, Ontario N6A 3K7, Canada and
The Brain and Mind Institute, The University of Western Ontario, London, Ontario N6A 3K7, Canada and.
J Neurosci. 2018 Jun 13;38(24):5466-5477. doi: 10.1523/JNEUROSCI.0346-18.2018. Epub 2018 May 17.
The ability to detect regularities in sound (i.e., recurring structure) is critical for effective perception, enabling, for example, change detection and prediction. Two seemingly unconnected lines of research concern the neural operations involved in processing regularities: one investigates how neural activity synchronizes with temporal regularities (e.g., frequency modulation; FM) in sounds, whereas the other focuses on increases in sustained activity during stimulation with repeating tone-frequency patterns. In three electroencephalography studies with male and female human participants, we investigated whether neural synchronization and sustained neural activity are dissociable, or whether they are functionally interdependent. Experiment I demonstrated that neural activity synchronizes with temporal regularity (FM) in sounds, and that sustained activity increases concomitantly. In Experiment II, phase coherence of FM in sounds was parametrically varied. Although neural synchronization was more sensitive to changes in FM coherence, such changes led to a systematic modulation of both neural synchronization and sustained activity, with magnitude increasing as coherence increased. In Experiment III, participants either performed a duration categorization task on the sounds, or a visual object tracking task to distract attention. Neural synchronization was observed regardless of task, whereas the sustained response was observed only when attention was on the auditory task, not under (visual) distraction. The results suggest that neural synchronization and sustained activity levels are functionally linked: both are sensitive to regularities in sounds. However, neural synchronization might reflect a more sensory-driven response to regularity, compared with sustained activity which may be influenced by attentional, contextual, or other experiential factors. Optimal perception requires that the auditory system detects regularities in sounds. Synchronized neural activity and increases in sustained neural activity both appear to index the detection of a regularity, but the functional interrelation of these two neural signatures is unknown. In three electroencephalography experiments, we measured both signatures concomitantly while listeners were presented with sounds containing frequency modulations that differed in their regularity. We observed that both neural signatures are sensitive to temporal regularity in sounds, although they functionally decouple when a listener is distracted by a demanding visual task. Our data suggest that neural synchronization reflects a more automatic response to regularity compared with sustained activity, which may be influenced by attentional, contextual, or other experiential factors.
检测声音中规律（即重复结构）的能力对于有效的感知至关重要，例如能够实现变化检测和预测。有两条看似不相关的研究线索涉及到处理规律的神经运作：一条研究了神经活动如何与声音中的时间规律（例如频率调制；FM）同步，而另一条则专注于在重复音调模式刺激下持续活动的增加。在三项针对男性和女性人类参与者的脑电图研究中，我们研究了神经同步和持续神经活动是否可分离，或者它们是否在功能上相互依赖。实验一表明，神经活动与声音中的时间规律（FM）同步，并且持续活动同时增加。在实验二中，声音中 FM 的相位相干性被参数化地改变。尽管神经同步对 FM 相干性的变化更敏感，但这些变化会导致神经同步和持续活动的系统调制，随着相干性的增加，幅度增加。在实验三中，参与者要么对声音进行持续时间分类任务，要么执行视觉物体跟踪任务以分散注意力。无论任务如何，都观察到神经同步，而只有当注意力集中在听觉任务上时才观察到持续反应，而在（视觉）分心时则不会。结果表明，神经同步和持续活动水平在功能上是相关的：两者都对声音中的规律敏感。然而，与可能受到注意力、上下文或其他经验因素影响的持续活动相比，神经同步可能反映了对规律的更具感官驱动的反应。最佳感知要求听觉系统检测声音中的规律。同步的神经活动和持续神经活动的增加似乎都可以指示规律的检测，但这两种神经特征的功能关系尚不清楚。在三项脑电图实验中，当听众听到包含调制频率不同的规则的声音时，我们同时测量了这两种特征。我们观察到，这两种神经特征都对声音中的时间规律敏感，尽管当听众被要求进行视觉任务时，它们在功能上分离。我们的数据表明，与可能受到注意力、上下文或其他经验因素影响的持续活动相比，神经同步反映了对规律的更自动反应。
