Abstract
The use of contextual information is an important capability to facilitate language comprehension. This can be shown by studying behavioral and neurophysiological measures of accelerated word recognition when semantically or phonemically related information is provided in advance, resulting in accompanying attenuation of the respective event-related potential, i.e. the N400 effect. Against the background of age-dependent changes in a broad variety of lexical capacities, we aimed to study whether word priming is accomplished differently in elderly compared to young persons. 19 young (29.9 ± 5.6 years) and 15 older (69.0 ± 7.2 years) healthy adults participated in a primed lexical decision task that required the classification of target stimuli (words or pseudo-words) following related or unrelated prime words. We assessed reaction time, task accuracy and N400 responses. Acceleration of word recognition by semantic and phonemic priming was significant in both groups, but resulted in overall larger priming effects in the older participants. Compared with young adults, the older participants were slower and less accurate in responding to unrelated word-pairs. The expected N400 effect was smaller in older than young adults, particularly during phonemic word and pseudo-word priming, with a rather similar N400 amplitude reduction by semantic relatedness. The observed pattern of results is consistent with preserved or even enhanced lexical context sensitivity in older compared to young adults. This, however, appears to involve compensatory cognitive strategies with higher lexical processing costs during phonological processing in particular, suggested by a reduced N400 effect in the elderly.
Highlights
To conclude, we found an age-dependent N400 modulation by lexical context at word level in semantic and phonemic priming of words and pseudo-words which resembled the pattern obtained at sentence level in previous studies
With respect to the N400 effect, younger participants showed decreased responses elicited by related items across all task subcategories, whereas this effect was considerably smaller in older adults
The N400 effect elicited by phonemic priming at electrode Cz was virtually absent for pseudo-words and words alike
Summary
We found an age-dependent N400 modulation by lexical context at word level in semantic and phonemic priming of words and pseudo-words which resembled the pattern obtained at sentence level in previous studies. Whereas the behavioral results pointed to even greater sensitivity to (or need for) context in older adults, the latter expressed markedly smaller N400 amplitude reductions accompanying phonemic and semantic priming than younger adults. This dissociation of behavioral and ERP results in older adults seems most reasonably to reflect age-related changes of resource allocation implying higher cognitive effort during lexical decisions, but it does not support a link between absent N400 effects and impaired use of lexical context. As dedifferentiation of cognitive abilities with age has been associated with changing patterns of intra- and interhemispheric brain activations in functional imaging studies, a correlation with altered N400 processing is a possible interpretation of the results that requires further investigatio
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