以功能性磁振造影初探聽覺語言歷程: 中日語言比較及老化影響

Abstract

人與人溝通的過程中，語言是最為常用的一種傳遞工具，透過'聽'而獲得成功的理解，此歷程包含了對語音的接收辨認及對語意的理解判斷，本研究旨在探討聽覺理解歷程於大腦皮質活化的情形，本研究又分為兩部份，第一部分是透過中文和日文之比較初探語音和語意歷程的相同與相異之處，建基於對語言系統的了解，進一步探究在時間脈絡下，老化可能帶來的影響，過去行為研究指出正常老化所導致的詞彙知識缺損並不明顯，但於功能性磁振造影研究中普遍發現，老化可能帶來腦區活化的程度下降，同時藉由額葉或其他較高階處理的區域之活化上升來補償以維持功能，然而老化於聽覺語意歷程之影響的實證研究仍相當缺乏，此為第二部分之研究動機。本研究使用功能性磁振造影及聽覺語意判斷作業，以感興趣區域(Regions of interest)的方式分析，並於研究二中同時控制大腦皮質萎縮的影響。本研究之研究一發現，在左側顳頂葉(temporoparietal regions)，包括緣上回(supramarginal gyrus)以及背側的額葉額下回(dorsal portion of inferior frontal gyrus)所形成的語音迴路在中日文語言系統中有差異，也證實語意處理在跨語言特性時活化情形較為接近。研究二結果顯示，在表現維持相同水準的情況下，老年組在負責語言知覺處理的左側上顳葉回(superior temporal gyrus)呈現顯著的功能下降，但在額葉或負責語音及語意歷程的區域並無明顯補償效應；同時，老年組於語意作業的行為表現在反應速度上有明顯下降，且與多處大腦皮質的萎縮呈負相關。本研究結果顯示，支持過去行為研究的結果，正常老化對語音處理或語意知識的功能影響不大，但語意判斷之反應慢化，且上顳葉回在行為表現未受影響之前即出現功能的降低，可能代表語音知覺的改變。

The aim of this study was to investigate the patterns of cortical activation during auditory semantic processing using fMRI and the effects of aging on this network. We reviewed current research for cortical activation patterns of auditory semantic processing and summarized relevant neuroimaging models of aging that showed consistent compensatory pattern of age-related changes in brain activity. We first examined similarities and differences in auditory phonological and semantic processing between Chinese and Japanese language. Based on language networks from younger population, we then examined compensatory pattern for auditory semantic processing in healthy elderly participants. We applied functional MRI and ROI analysis to investigate the activation patterns of language-related regions in healthy young and old participants. Young Japanese participants showed greater activation in temporoparietal regions including left supramarginal gyrus and left dorsal portion of inferior gyrus compared to young Taiwanese participants during speech perception processing of their respective languages. Japanese and Chinese language elicited similar activity in the semantic network, especially in the angular gyrus, middle temporal gyrus and the ventral portion of inferior frontal gyrus. In terms of aging effects, elderly Japanese adults had decreased left superior temporal gyrus activation compared to the younger Japanese, suggesting an initial change in the semantic language network. In addition, a general slowing during semantic judgment associated with the volumetric decline was observed.