Department of Psychology and Center for Mind and Brain, University of California, Davis, USA; Department of Medical Social Sciences, Feinberg School of Medicine, Northwestern University, USA.
Department of Psychology and Center for Mind and Brain, University of California, Davis, USA; Departments of Psychology and Psychiatry, Tufts University and Massachusetts General Hospital, USA.
Neuropsychologia. 2018 Aug;117:135-147. doi: 10.1016/j.neuropsychologia.2018.05.023. Epub 2018 May 28.
Young adults show consistent neural benefits of predictable contexts when processing upcoming words, but these benefits are less clear-cut in older adults. Here we disentangle the neural correlates of prediction accuracy and contextual support during word processing, in order to test current theories that suggest that neural mechanisms underlying predictive processing are specifically impaired in older adults. During a sentence comprehension task, older and younger readers were asked to predict passage-final words and report the accuracy of these predictions. Age-related reductions were observed for N250 and N400 effects of prediction accuracy, as well as for N400 effects of contextual support independent of prediction accuracy. Furthermore, temporal primacy of predictive processing (i.e., earlier facilitation for successful predictions) was preserved across the lifespan, suggesting that predictive mechanisms are unlikely to be uniquely impaired in older adults. In addition, older adults showed prediction effects on frontal post-N400 positivities (PNPs) that were similar in amplitude to PNPs in young adults. Previous research has shown correlations between verbal fluency and lexical prediction in older adult readers, suggesting that the production system may be linked to capacity for lexical prediction, especially in aging. The current study suggests that verbal fluency modulates PNP effects of contextual support, but not prediction accuracy. Taken together, our findings suggest that aging does not result in specific declines in lexical prediction.
年轻人在处理即将到来的单词时，表现出一致的、可预测的上下文带来的神经优势，但老年人的这种优势并不明显。在这里，我们将在单词处理过程中分离预测准确性和上下文支持的神经相关性，以检验当前的理论，即预测加工背后的神经机制在老年人中受到了特定的损害。在句子理解任务中，要求老年和年轻读者预测文章结尾的单词，并报告这些预测的准确性。与年龄相关的 N250 和 N400 预测准确性效应以及独立于预测准确性的 N400 上下文支持效应都有所减少。此外，预测加工的时间优先性（即成功预测的早期促进）在整个生命周期中都得到了保留，这表明预测机制不太可能在老年人中受到独特的损害。此外，老年人在前 N400 正波（PNP）上表现出与年轻成年人相似幅度的预测效应。先前的研究表明，老年人的词汇预测与言语流畅性之间存在相关性，这表明产生系统可能与词汇预测能力相关，尤其是在衰老过程中。本研究表明，言语流畅性调节了 PNP 对上下文支持的影响，但不调节预测准确性。总的来说，我们的发现表明，衰老不会导致词汇预测能力的特定下降。
