Speech perception, acoustic variability and time: normal and impaired listeners

描述（由申请人提供）：言语感知给听者带来了两个难题。首先，声音信号是可变的和上下文相关的，使得音素识别困难。其次，它随着时间的推移而展开，在一个单词的早期，可能没有足够的信息来识别它。本研究旨在了解听众如何解决这两个问题，这些问题如何相互关联，并以此来了解两组受损听众：语言障碍听众（LI）和使用人工耳蜗（CIs）的听众。项目1询问听者如何补偿由于说话者和语音上下文造成的变化，以及补偿如何与听者在单词识别过程中暂时考虑的候选单词之间展开的竞争相互作用。它采用事件相关电位来评估补偿是否发生在听觉编码水平或在以后的分类过程中。它还使用眼动追踪来检查词汇竞争对手每时每刻的激活（听众同时考虑多个单词的强烈程度），询问声音提示和补偿过程何时影响词汇处理。最后，它考察了难以识别说话者的CI用户可能会抑制他们的补偿能力。这可能会导致更好的处理策略，设备配置和治疗。项目2检查听者如何表示单词中信息的顺序（例如，他们如何区分像cat和tack这样的合成词）。大多数型号使用音素的序列顺序来排除畸形竞争者。然而，最近的数据表明，听众并没有完全排除anadrome，这表明顺序没有明确表示。项目2使用眼动追踪和视觉世界范式，使用已知单词和小型人工语言来确定听者是否使用细粒度的声学细节（音素在音节开头和结尾位置的发音差异）作为顺序的代理。它还检查了患有LI的听众，他们可能在细粒度的听觉细节和序列顺序方面都有缺陷；以及无法获得细粒度光谱细节的CI用户。这将评估强调听觉或顺序缺陷是LI来源的语言障碍理论。它还将帮助我们了解CI用户之间结果的可变性，并进一步完善我们对CI必须传输哪些声学信息的理解。项目3询问词汇竞争对手在单词识别过程中保持活跃的时间。先前的研究发现，具有LI的听者在单词识别过程中不能完全抑制词汇竞争对手。项目3开发了一种眼球追踪范式来评估竞争对手活跃的时间，并通过检查单词、回声记忆和语音短期记忆之间的抑制来询问维持这种活跃的机制。它将听者与LI和CI使用者一起进行研究，以确定这种激烈竞争的后果，它与其他语言过程的关系以及损害的位置。在这三个项目中，本提案旨在更好地表征正常听者言语感知的潜在机制，目的是利用这种表征来更好地理解受损听者面临的独特问题。

DESCRIPTION (provided by applicant): Speech perception poses two difficult problems for listeners. First, the acoustic signal is variable and context dependent, making phoneme identification difficult. Second, it unfolds over time and at early points in a word there may not e sufficient information to identify it. This research aims to understand how listeners solve both problems, how these problems relate to each other, and to use this to understand two groups of impaired listeners: listeners with Language Impairment (LI) and listeners who use Cochlear Implants (CIs). Project 1 asks how listeners compensate for variation due to talker and phonetic context, and how compensation interacts with unfolding competition between candidate words that listeners momentarily consider during word recognition. It employs event related potentials to assess whether compensation occurs at the level of auditory encoding or during later categorical processes. It also uses eye-tracking to examine moment-by-moment activation of lexical competitors (how strongly listeners consider multiple words in parallel), asking when acoustic cues and compensation processes impact lexical processing. Finally, it examines CI users whose difficulty identifying talkers may inhibit their compensation abilities. This may lead to better processing strategies, device configurations and therapies. Project 2 examines how listeners represent the order of information in a word (e.g., how they distinguish anadromes like cat and tack). Most models use the serial order of the phonemes to exclude anadrome competitors. However, recent data indicate that listeners do not completely rule out anadromes, suggesting that order is not explicitly represented. Project 2 uses eye-tracking and visual world paradigm with known words and small artificial languages to determine whether listeners use fine-grained acoustic detail (differences in how a phoneme is pronounced in syllable-initial and final positions) as a proxy for order. It also examines listeners with LI, who may have deficits with both fine-grained auditory detail and serial order; and CI users who lack access to fine-grained spectral detail. This will assess theories of language impairment that emphasis auditory or sequencing deficits as the source of LI. It will also help us understand the variability in outcomes among CI users and further refine our understanding of what acoustic information must be transmitted by the CI. Project 3 asks how long lexical competitors remain active during word recognition. The prior grant discovered that listeners with LI do not fully suppress lexical competitors during word recognition. Project 3 develops an eye-tracking paradigm to assess how long competitors are active, and to ask what mechanisms maintain it, examining inhibition between words, echoic memory and phonological short-term memory. It ex- amines listeners with LI and CI users to determine the consequences of this heightened competition, how it relates to other language processes, and the locus of the impairment. Across all three projects, this proposal aims to better characterize the underlying mechanisms of speech perception in normal listeners with the goal of using this characterization to better understand the unique problems faced by impaired listeners.