Department of Experimental Audiology, Faculty of Medicine, Otto von Guericke University Magdeburg Magdeburg, Germany.
Special Lab Non-invasive Brain Imaging, Leibniz Institute for Neurobiology Magdeburg, Germany.
Front Psychol. 2014 Jul 21;5:775. doi: 10.3389/fpsyg.2014.00775. eCollection 2014.
In a complex acoustical environment, the auditory system decides which stimulus components originate from the same source by forming auditory streams, where temporally non-overlapping stimulus portions are considered to originate from one source if their stimulus characteristics are similar. The mechanisms underlying streaming are commonly studied by alternating sequences of A and B signals which are often tones with different frequencies. For similar frequencies, they are grouped into one stream. Otherwise, they are considered to belong to different streams. The present study investigates streaming in cochlear implant (CI) users, where hearing is restored by electrical stimulation of the auditory nerve. CI users listened to 30-s long sequences of alternating A and B harmonic complexes at four different fundamental frequency separations, ranging from 2 to 14 semitones. They had to indicate as promptly as possible after sequence onset, if they perceived one stream or two streams and, in addition, any changes of the percept throughout the rest of the sequence. The conventional view is that the initial percept is always that of a single stream which may after some time change to a percept of two streams. This general build-up hypothesis has recently been challenged on the basis of a new analysis of data of normal-hearing listeners. Using the same experimental paradigm and analysis, the present study found that the results of CI users agree with those of the normal-hearing listeners: (i) the probability of the first decision to be a one-stream percept decreased and that of a two-stream percept increased as Δf increased, and (ii) a build-up was only found for 6 semitones. Only the time elapsed before the listeners made their first decision of the percept was prolonged as compared to normal-hearing listeners. The similarity in the data of the CI user and the normal-hearing listeners indicates that the quality of stream formation is similar in these groups of listeners.
在复杂的声学环境中，听觉系统通过形成听觉流来决定哪些刺激成分来自同一来源，其中，如果刺激特征相似，则暂时不重叠的刺激部分被认为来自同一来源。流的形成机制通常通过交替的 A 和 B 信号序列来研究，这些信号通常是具有不同频率的音调。对于相似的频率，它们被组合成一个流。否则，它们被认为属于不同的流。本研究调查了人工耳蜗（CI）使用者中的流，他们通过听觉神经的电刺激来恢复听力。CI 用户在四个不同的基频分离（从 2 个半音到 14 个半音）下，听了 30 秒长的交替 A 和 B 谐波复合序列。在序列开始后，他们必须尽快指出他们是否感知到一个流或两个流，以及在序列的其余部分中感知的任何变化。传统观点认为，初始感知始终是单个流的感知，经过一段时间后可能会变为两个流的感知。最近，基于对正常听力听众数据的新分析，这一普遍的构建假设受到了挑战。本研究使用相同的实验范式和分析方法，发现 CI 用户的结果与正常听力听众的结果一致：（i）第一次决定感知为单一流的概率随着 Δf 的增加而降低，而感知为双流的概率增加，（ii）仅在 6 个半音时才发现构建。只有听众做出第一个感知决策之前的时间延长了，而不是正常听力听众。CI 用户和正常听力听众的数据的相似性表明，这些听众群体中流形成的质量是相似的。
