Snyder Joel S, Alain Claude
The Rotman Research Institute, Baycrest Centre for Geriatric Care, Toronto, Ontario, Canada.
Cereb Cortex. 2007 Mar;17(3):501-12. doi: 10.1093/cercor/bhj175. Epub 2006 Mar 31.
Normal aging is accompanied by speech perception difficulties, especially in adverse listening situations such as a cocktail party. To assess whether such difficulties might be related to impairments in sequential auditory scene analysis, event-related brain potentials were recorded from normal-hearing young, middle-aged, and older adults during presentation of low (A) tones, high (B) tones, and silences (--) in repeating 3 tone triplets (ABA--). The likelihood of reporting hearing 2 streams increased as a function of the frequency difference between A and B tones (Delta f) to the same extent for all 3 age groups and was paralleled by enhanced sensory-evoked responses over the frontocentral scalp regions. In all 3 age groups, there was also a progressive buildup in brain activity from the beginning to the end of the sequence of triplets, which was characterized by an enhanced positivity that peaked at about 200 ms after the onset of each ABA--triplet. Similar Delta f- and buildup-related activity also occurred over the right temporal cortex, but only for young adults. We conclude that age-related difficulties in separating competing speakers are unlikely to arise from deficits in streaming and might instead reflect less efficient concurrent sound segregation.
正常衰老伴随着言语感知困难，尤其是在诸如鸡尾酒会等不利的听觉环境中。为了评估这些困难是否可能与序列听觉场景分析受损有关，在向听力正常的年轻人、中年人和老年人呈现重复的3个音调三元组（ABA--）中的低音调（A）、高音调（B）和静音（--）时，记录了事件相关脑电位。对于所有3个年龄组，报告听到2个声流的可能性随着A音和B音之间的频率差（Δf）而增加，并且在额中央头皮区域的感觉诱发反应增强与之平行。在所有3个年龄组中，从三元组序列开始到结束，大脑活动也有逐渐增强，其特征是在每个ABA--三元组开始后约200毫秒达到峰值的增强正电位。类似的与Δf和增强相关的活动也出现在右侧颞叶皮层，但仅见于年轻人。我们得出结论，与年龄相关的区分竞争说话者的困难不太可能源于声流分离缺陷，而可能反映了同时进行的声音分离效率较低。
