大脑如何感知和理解言语是心理学和脑科学研究的重要问题之一。近年来，言语产出相关的皮层言语运动系统（SMS）通常被认为以代偿调节方式参与有噪音干扰和/或信息缺失情况下的言语知觉中。本研究采用功能性核磁共振成像（fMRI）技术考查在噪音干扰下的音节辨识任务中的感觉运动整合机制。研究1发现，SMS的参与程度随语音辨识难度增加而增加、在噪音干扰下比听皮层具有更高的音位特异性编码和表征能力，并且在难度适中时对听皮层编码代偿作用最大。研究2发现，听力正常的老年人在噪音干扰下存在音节辨识困难，且比年轻人更加依赖SMS的活动增加以及较少受到老化和噪音影响的言语运动表征以代偿听觉加工能力的下降。本研究不仅加深了对言语知觉中跨通道感觉运动信息整合机制及其毕生发展机制的认识，还为帮助听力受损或正常的老年人设计和开展言语交流康复训练方案提供了新的视角和启发。
The way our brains perceive and comprehend speech remains an essential issue in psychology and brain science. In recent years, consensus has gradually been made on that the speech motor system (SMS) contributes to speech perception in a modulatory and compensatory manner, especially under noise masking or speech degradation circumstances. Using functional magnetic resonance imaging, the current work investigates neural mechanisms of sensorimotor integration and compensation during syllable identification task in noisy conditions. Study 1 reveals an increment of the SMS involvement as the task difficulty increases. In addition, the SMS shows more robust specificity of phoneme representations than auditory regions in noisy conditions, as such a superiority climaxes at moderate noise levels. Study 2 finds that older adults with normal hearing have difficulty in syllable-in-noise identification. Compared with younger counterparts, the elders rely more on increased recruitment of the SMS and preserved speech motoric representations, which are less affected by noise and aging effects than auditory ones, to compensate for deficient auditory encoding. Our findings deepen the knowledge of neural mechanisms underlying cross-modal sensorimotor integration in speech perception and its life-span developmental changes. Moreover, new insights could be given on designing and implementing rehabilitative and training regimens for speech comprehension (e.g., SMS-targeted brain enhancement) in older adults with or without hearing loss.
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