Department of Neurology, University of Pennsylvania, Philadelphia, PA 19104, USA.
Cereb Cortex. 2010 Apr;20(4):773-82. doi: 10.1093/cercor/bhp142. Epub 2009 Aug 7.
Speech comprehension remains largely preserved in older adults despite significant age-related neurophysiological change. However, older adults' performance declines more rapidly than that of young adults when listening conditions are challenging. We investigated the cortical network underlying speech comprehension in healthy aging using short sentences differing in syntactic complexity, with processing demands further manipulated through speech rate. Neural activity was monitored using blood oxygen level-dependent functional magnetic resonance imaging. Comprehension of syntactically complex sentences activated components of a core sentence-processing network in both young and older adults, including the left inferior and middle frontal gyri, left inferior parietal cortex, and left middle temporal gyrus. However, older adults showed reduced recruitment of inferior frontal regions relative to young adults; the individual degree of recruitment predicted accuracy at the more difficult fast speech rate. Older adults also showed increased activity in frontal regions outside the core sentence-processing network, which may have played a compensatory role. Finally, a functional connectivity analysis demonstrated reduced coherence between activated regions in older adults. We conclude that decreased activation of specialized processing regions, and limited ability to coordinate activity between regions, contribute to older adults' difficulty with sentence comprehension under difficult listening conditions.
尽管老年人的神经生理学发生了显著变化，但他们的言语理解能力仍然基本保持。然而，在听力条件具有挑战性时，老年人的表现比年轻人下降得更快。我们使用句法复杂度不同的短句子来研究健康衰老过程中的言语理解的皮质网络，通过语速进一步控制处理需求。使用血氧水平依赖功能磁共振成像来监测神经活动。句法复杂的句子理解在年轻和老年成年人中激活了核心句子处理网络的组成部分，包括左额下回和中回、左顶下小叶和左颞中回。然而，与年轻人相比，老年人的额下回区域的招募减少；在更困难的快速语速下，招募的个体程度预测了准确性。老年人还表现出额前区域的活动增加，这些区域可能发挥了代偿作用。最后，功能连接分析表明，老年人激活区域之间的相干性降低。我们的结论是，专门处理区域的激活减少，以及区域间活动协调的能力有限，导致老年人在困难的听力条件下理解句子的困难。
