Oticon A/S, Smørum, Denmark.
Department of Behavioural Sciences and Learning, Linnaeus Centre HEAD, Swedish Institute for Disability Research, Linköping University, Linköping, Sweden.
Ear Hear. 2021;42(6):1668-1679. doi: 10.1097/AUD.0000000000001053.
Communication requires cognitive processes which are not captured by traditional speech understanding tests. Under challenging listening situations, more working memory resources are needed to process speech, leaving fewer resources available for storage. The aim of the current study was to investigate the effect of task difficulty predictability, that is, knowing versus not knowing task difficulty in advance, and the effect of noise reduction on working memory resource allocation to processing and storage of speech heard in background noise. For this purpose, an "offline" behavioral measure, the Sentence-Final Word Identification and Recall (SWIR) test, and an "online" physiological measure, pupillometry, were combined. Moreover, the outcomes of the two measures were compared to investigate whether they reflect the same processes related to resource allocation.
Twenty-four experienced hearing aid users with moderate to moderately severe hearing loss participated in this study. The SWIR test and pupillometry were measured simultaneously with noise reduction in the test hearing aids activated and deactivated in a background noise composed of four-talker babble. The task of the SWIR test is to listen to lists of sentences, repeat the last word immediately after each sentence and recall the repeated words when the list is finished. The sentence baseline dilation, which is defined as the mean pupil dilation before each sentence, and task-evoked peak pupil dilation (PPD) were analyzed over the course of the lists. The task difficulty predictability was manipulated by including lists of three, five, and seven sentences. The test was conducted over two sessions, one during which the participants were informed about list length before each list (predictable task difficulty) and one during which they were not (unpredictable task difficulty).
The sentence baseline dilation was higher when task difficulty was unpredictable compared to predictable, except at the start of the list, where there was no difference. The PPD tended to be higher at the beginning of the list, this pattern being more prominent when task difficulty was unpredictable. Recall performance was better and sentence baseline dilation was higher when noise reduction was on, especially toward the end of longer lists. There was no effect of noise reduction on PPD.
Task difficulty predictability did not have an effect on resource allocation, since recall performance was similar independently of whether task difficulty was predictable or unpredictable. The higher sentence baseline dilation when task difficulty was unpredictable likely reflected a difference in the recall strategy or higher degree of task engagement/alertness or arousal. Hence, pupillometry captured processes which the SWIR test does not capture. Noise reduction frees up resources to be used for storage of speech, which was reflected in the better recall performance and larger sentence baseline dilation toward the end of the list when noise reduction was on. Thus, both measures captured different temporal aspects of the same processes related to resource allocation with noise reduction on and off.
交流需要认知过程，但传统的言语理解测试无法捕捉到这些过程。在具有挑战性的听力环境下，处理言语需要更多的工作记忆资源，从而减少了用于存储的资源。本研究旨在探讨任务难度可预测性（即提前知道或不知道任务难度）以及降噪对在背景噪声中听到的言语处理和存储的工作记忆资源分配的影响。为此，结合了一种“离线”行为测量方法，即句子结尾词识别和回忆测试（SWIR），以及一种“在线”生理测量方法，即瞳孔测量法。此外，还比较了这两种测量方法的结果，以研究它们是否反映了与资源分配相关的相同过程。
24 名有中度至中度重度听力损失的经验丰富的助听器使用者参加了这项研究。在由四人谈话声组成的背景噪声中，同时使用降噪功能激活和停用测试助听器，测量 SWIR 测试和瞳孔测量。SWIR 测试的任务是听句子列表，在听完每个句子后立即重复最后一个单词，并在列表结束后回忆重复的单词。在句子基线扩张期间（即每个句子之前的平均瞳孔扩张）和任务诱发的峰值瞳孔扩张（PPD）期间，分析了句子基线扩张。通过包含三、五和七个句子的列表来操纵任务难度的可预测性。测试分两个阶段进行，其中一个阶段在每个列表之前向参与者提供有关列表长度的信息（可预测的任务难度），另一个阶段不提供（不可预测的任务难度）。
与可预测的任务难度相比，当任务难度不可预测时，句子基线扩张更高，除了列表开头没有差异。在列表开头，PPD 往往更高，当任务难度不可预测时，这种模式更为明显。当降噪开启时，回忆表现更好，句子基线扩张更高，尤其是在较长列表的末尾。降噪对 PPD 没有影响。
任务难度的可预测性并没有对资源分配产生影响，因为无论任务难度是可预测的还是不可预测的，回忆表现都相似。当任务难度不可预测时，句子基线扩张较高，可能反映了回忆策略的差异、更高程度的任务参与/警觉性或唤醒。因此，瞳孔测量法捕捉到了 SWIR 测试无法捕捉到的过程。降噪释放了用于存储言语的资源，这反映在降噪开启时，列表末尾的回忆表现更好，句子基线扩张更大。因此，两种测量方法都捕捉到了与降噪开启和关闭相关的资源分配的不同时间方面的过程。
