Wambacq Ilse J A, Koehnke Janet, Besing Joan, Romei Laurie L, Depierro AnnMarie, Cooper David
Department of Communication Sciences and Disorders, Audiology Program, Montclair State University, NJ 07043, USA.
J Am Acad Audiol. 2009 Jul-Aug;20(7):453-8.
When listening to one speaker while another conversation is occurring simultaneously, we separate the competing sounds by processing physical cues such as common onset time, intensity, frequency harmonicity, and spatial location of the sound sources. Spatial location is determined in large part by differences in arrival of a sound at one ear versus the other ear, otherwise known as interaural time difference (ITD) or interaural phase difference (IPD). There is ample anecdotal evidence that middle-aged adults experience greater difficulty listening to speech in noise, even when their audiological evaluation does not reveal abnormal results. Furthermore, it has been shown that the frequency range for IPD processing is reduced in middle-aged adults compared to young adults, even though morphological changes in the auditory evoked potential (AEP) response were only observed in older adults.
The purpose of the current study was to examine early aging effects (< 60 years) on IPD processing in concurrent sound segregation.
We examined the change AEP evoked by detection of a mistuned and/or phase-shifted second harmonic during the last 1500 msec of a 3000 msec amplitude-modulated harmonic complex. A passive listening paradigm was used.
Ten young (21-35 years) and 11 middle-aged (48-57 years) adults with normal hearing were included in the study.
Scalp electroencephalographic activity was recorded from 63 electrodes. A temporospatial principal component analysis was conducted. Spatial factor scores of individual spatial factors were the dependent variable in separate mixed-design ANOVAs for each temporal factor of interest. Stimulus type was the within-subject independent variable, and age group was the between-subject independent variable.
Results indicated a delay in the upward P2 slope and the P2 peak latency to a sudden phase shift in the second harmonic of a harmonic complex in middle-aged adults compared to young adults. This AEP difference increased as mistuning (as a second grouping cue) decreased and remained evident when the IPD was the only grouping cue.
We conclude that our findings reflect neurophysiologic differences between young and middle-aged adults for IPD processing in concurrent sound segregation.
当在听一个说话者讲话的同时另一段对话也在进行时，我们通过处理诸如声音源的共同起始时间、强度、频率谐波性和空间位置等物理线索来分离相互竞争的声音。空间位置在很大程度上由声音到达一只耳朵与另一只耳朵的时间差异决定，也就是所谓的双耳时间差（ITD）或双耳相位差（IPD）。有大量轶事证据表明，中年成年人在嘈杂环境中听语音时会遇到更大困难，即使他们的听力评估未显示异常结果。此外，研究表明，与年轻人相比，中年成年人处理IPD的频率范围有所缩小，尽管仅在老年人中观察到听觉诱发电位（AEP）反应的形态学变化。
本研究的目的是检查早期衰老效应（<60岁）对同时进行的声音分离中IPD处理的影响。
我们检查了在一个3000毫秒调幅谐波复合体的最后1500毫秒期间，检测到失谐和/或相移的二次谐波时诱发的AEP变化。采用被动聆听范式。
本研究纳入了10名听力正常的年轻人（21 - 35岁）和11名中年成年人（48 - 57岁）。
从63个电极记录头皮脑电图活动。进行了颞空间主成分分析。对于每个感兴趣的时间因素，在单独的混合设计方差分析中，各个空间因素的空间因子得分是因变量。刺激类型是受试者内自变量，年龄组是受试者间自变量。
结果表明，与年轻人相比，中年成年人在谐波复合体二次谐波突然相移时，向上的P2斜率和P2峰潜伏期延迟。随着失谐（作为第二个分组线索）减少，这种AEP差异增大，并且当IPD是唯一的分组线索时仍然明显。
我们得出结论，我们的研究结果反映了年轻人和中年成年人在同时进行的声音分离中处理IPD的神经生理差异。
