Centre for Cognitive Ageing and Cognitive Epidemiology (CCACE), Department of Psychology, University of Edinburgh, UK.
J Neuropsychol. 2019 Sep;13(3):462-484. doi: 10.1111/jnp.12159. Epub 2018 Apr 17.
Effective use of semantic knowledge requires a set of conceptual representations and control processes which ensure that currently relevant aspects of this knowledge are retrieved and selected. It is well-established that levels of semantic knowledge increase across the lifespan. However, the effects of ageing on semantic control processes have not been assessed. I addressed this issue by comparing the performance profiles of young and older people on a verbal comprehension test. Two sets of variables were used to predict accuracy and RT in each group: (1) the psycholinguistic properties of words probed in each trial and (2) the performance on each trial by two groups of semantically impaired neuropsychological patients. Young people demonstrated poor performance for low-frequency and abstract words, suggesting that they had difficulty processing words with intrinsically weak semantic representations. Indeed, performance in this group was strongly predicted by the performance of patients with semantic dementia, who suffer from degradation of semantic knowledge. In contrast, older adults performed poorly on trials where the target semantic relationship was weak and distractor relationships strong - conditions which require high levels of controlled processing. Their performance was not predicted by the performance of semantic dementia patients, but was predicted by the performance of patients with semantic control deficits. These findings indicate that the effects of ageing on semantic cognition are more complex than has previously been assumed. While older people have larger stores of knowledge than young people, they appear to be less skilled at exercising control over the activation of this knowledge.
有效利用语义知识需要一套概念表示和控制过程，以确保当前相关的知识得到检索和选择。已经确立的是，语义知识水平在整个生命周期中都会增加。然而，衰老对语义控制过程的影响尚未得到评估。我通过比较年轻人和老年人在口头理解测试中的表现来解决这个问题。两组变量用于预测每组的准确性和 RT：（1）在每个试验中探测的单词的心理语言学属性，（2）两组语义受损神经心理患者在每个试验中的表现。年轻人在低频和抽象词上表现不佳，这表明他们处理具有内在弱语义表示的单词有困难。事实上，该组的表现与语义痴呆患者的表现密切相关，后者患有语义知识退化。相比之下，老年人在目标语义关系较弱而干扰关系较强的试验中表现不佳——这些条件需要高水平的控制处理。他们的表现不能由语义痴呆患者的表现来预测，而是可以由语义控制缺陷患者的表现来预测。这些发现表明，衰老对语义认知的影响比之前假设的更为复杂。虽然老年人比年轻人拥有更多的知识储备，但他们似乎在控制知识的激活方面不太熟练。
