妈妈为什么年纪越大越唠叨?她可能只是想听清你在说什么
Nature自然科研 · 2016/08/06
妈妈为什么年级越大越易唠叨?除了爱,或许是因为她们想听清楚外面的声音。近期,中国科学院心理研究所的科学家们发现,老年人听力下降后,大脑的“语言活动区域”会增强,从而弥补听力的损失。


人上了年纪耳朵会由于各种原因不灵。但大脑作为神经中枢,是会尽可能不让重要的听觉孤立无援的。大脑甚至会调用其他区域来辅助年长者听清周围的声音。

先前的研究显示,在嘈杂环境中,年长者能通过激活与一般认知能力相关的脑区来处理语音,他们的这些脑区往往比同一环境中的年轻人更活跃。但语音感知还包括整合其他脑区的信息,尤其是与交谈有关的脑区。直到目前,这种整合是否能帮助年长者理解嘈杂环境中的语音都尚不清楚。

本周发表于《自然-通讯》的研究 Increased activity in frontal motor cortex compensates impaired speech perception in older adults 中,中国科学院心理研究所的杜一及同事使用了功能性磁共振成像扫描(fMRI),比较了在16位21-34岁和16位65-75岁的成年人在音节识别任务中的脑活动模式。他们发现,在年长者中表现出了“语言运动区域”活动增强。这一策略可被用于补偿语音信号清晰性的缺乏。这种增强与他们在嘈杂环境中辨别不同词语语音的能力是相应的。


年轻和年长的人辨别语音时脑部活动对比。图片来源:Du et al.

也就是说,这一研究确认了当听力功能逐渐下降时,年长者的大脑会通过强化关于说话的脑区,来补偿听力的损失,帮助年长者在吵闹的环境中听清别人说话。

面对听力下降的不利状况,年长者的大脑使用了独特的策略,来帮助自己在不利听觉环境中理解语音。对于帮助老人提升沟通能力的疗法,这一策略有着重要的参考价值。

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  • Increased activity in frontal motor cortex compensates impaired speech perception in older adults

    Understanding speech in noisy environments is challenging, especially for seniors. Although evidence suggests that older adults increasingly recruit prefrontal cortices to offset reduced periphery and central auditory processing, the brain mechanisms underlying such compensation remain elusive. Here we show that relative to young adults, older adults show higher activation of frontal speech motor areas as measured by functional MRI during a syllable identification task at varying signal-to-noise ratios. This increased activity correlates with improved speech discrimination performance in older adults. Multivoxel pattern classification reveals that despite an overall phoneme dedifferentiation, older adults show greater specificity of phoneme representations in frontal articulatory regions than auditory regions. Moreover, older adults with stronger frontal activity have higher phoneme specificity in frontal and auditory regions. Thus, preserved phoneme specificity and upregulation of activity in speech motor regions provide a means of compensation in older adults for decoding impoverished speech representations in adverse listening conditions.

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