Morfologisen perheen vaikutus sanan tunnistamiseen normaalissa ikääntymisessä, lievässä kognitiivisessa häiriössä, sekä Alzheimerin taudissa

Reading a word activates morphologically related words in the mental lexicon. People with Alzheimer's disease (AD) or Mild Cognitive Impairment (MCI) often have difficulty retrieving words, though the source of this problem is not well understood. To better understand the word recognition process in aging and in neurodegenerative disorders such as MCI and AD, we investigated the nature of the activation of morphologically related family members in 22 Finnish speakers with AD, 24 with MCI, and 17 cognitively healthy elderly. We presented Finnish monomorphemic (base form) nouns in a single-word lexical decision experiment to measure the speed of word recognition and its relation to morphological and lexical variables. Morphological variables included morphological family size (separate for compounds and derived words) and pseudo-morphological family size (including the set of words that have a partially overlapping form but that do not share an actual morpheme, e.g., pet and carpet, or corn and corner). Pseudo-morphological family size was included to examine the influence of words with orthographic (or phonological) overlap that are not semantically related to the target words. Our analyses revealed that younger and elderly controls and individuals with MCI or AD were influenced by true morphological overlap (overlapping forms that also share meaning), as well as by the word's pseudo morphological family. However, elderly controls and individuals with MCI or AD seemed to rely more on form overlap than young adults. This demonstrates that an increased reliance on form-based aspects of language processing in Alzheimer's disease is not necessarily due to a partial loss of access to semantics, but might be explained in part by a common age-related change of processes in written word recognition. (C) 2018 The Author(s). Published by Elsevier Ltd.Peer reviewe

Vartaloallomorfien myönteinen vaikutus sanojen tunnistamiseen

The aim of the present study was to investigate whether the recognition speed of Finnish nominal base forms varies as a function of their paradigmatic complexity (stem allomorphy) or productivity status. Nikolaev et al. (2014) showed that words with greater stem allomorphy from an unproductive inflectional class arc recognized faster than words with lower stein allomorphy from a productive inflectional class. Productivity of an inflectional paradigm correlates with the number of stem allomorphs in languages like Finnish in that unproductive inflectional classes tend to have higher stem allomorphy. We wanted to distinguish which of these two characteristics provides the benefit to speed of recognition found by Nikolaev et al. (2014). The current study involved a lexical decision task comparing three categories of words: unproductive with three or more stem allomorphs, unproductive with two stem allomorphs, and productive with two stein allomorphs. We observed a facilitation effect for word recognition only for unproductive words with three or more stem allomorphs, but not for unproductive words with two allomorphs. This effect was observed particularly in words of low to moderate familiarity. The findings suggest that high stem allomorphy, rather than productivity of the inflectional class, is driving the facilitation effect in word recognition.Peer reviewe

Age-related Differences in Idiom Production in Adulthood

To investigate whether idiom production was vulnerable to age-related difficulties, we asked 40 younger (ages 18–30) and 40 older healthy adults (ages 60–85) to produce idiomatic expressions in a story-completion task. Younger adults produced significantly more correct idiom responses (73%) than did older adults (60%). When older adults generated partially correct responses, they were less likely than younger participants to eventually produce the complete target idiom (old: 32%; young: 70%); first-word cues after initial failure to retrieve an idiom resulted in more correct idioms for older (24%) than younger (15%) participants. Correlations between age and idiom correctness were positive for the young group and negative for the older group, suggesting mastery of familiar idioms continues into adulthood. Within each group, scores on the Boston Naming Test correlated with performance on the idiom task. Findings for retrieving idiomatic expressions are thus similar to those for retrieving lexical items

The Relationship Between Lexical Performance and Regional Gray Matter Volumes: A Longitudinal Study of Cognitively Healthy Elderly

This study investigated the longitudinal relationship among aging, performance on lexical tasks, and regional gray matter volumes over 2-7 years. A total of 137 older participants who remained cognitively normal were administered four lexical tasks at each time point: the Boston Naming Test (BNT), Vocabulary Test, Semantic- and Phonemic-Fluency task. In addition, they underwent repeated magnetic resonance imaging (MRI) scanning acquired within two months of the lexical tasks. The average interval between time points was 2.36 years (range 1.50-7.64) and the average number of time points was 2.65 times (range 2-5). Results indicated that age differentially affects lexical task performance in two ways. First, baseline age was significantly negatively related to the scores on the BNT and Semantic Fluency task but not related to the Vocabulary test and Phonemic Fluency task. Second, the interval between the baseline and follow-ups was significantly related to the performance on the BNT, Vocabulary test and Semantic Fluency task. The longer the interval between the observations, the lower the scores on these tasks. This shows that as people get older, general lexical production ability within participants declines. Moreover, the rate of change in performance over time varies across tasks. Older participants tended to score lower at each successive time point and the rate of decline was greater on the tasks that impose more constraints on semantic and phonemic specificity than the tasks that demand less specificity in lexical selection. Thus, the BNT and Semantic Fluency tasks are more sensitive to age-related lexical performance changes in cognitively normal older adults than are Phonemic Fluency tasks or Vocabulary Test. Further, the interval effect clearly shows that as time progresses older adults’ lexical production abilities decline on all tasks except in the Phonemic Fluency. Regarding the relationship between regional brain volumes and lexical performance over time, common and specific association patterns were found. Individual brain regions whose volume reduction predicted lexical performance decline were found in the bilateral temporal, parietal and frontal cortices. More specifically, the volumes of the medial temporal lobes (MTL) were significantly related to performance on all four lexical task, while other brain regions showed distinctive association patterns with individual tasks; the frontal pole was related to accuracy on the BNT; the temporal pole, supramarginal gyrus, superior frontal and superior parietal cortices to the scores on the Vocabulary Test; the dorsolateral prefrontal and precuneus to the scores on the Semantic Fluency task; the fusiform gyrus, inferior frontal, superior parietal, superior and inferior temporal cortices to the scores on the Phonemic Fluency task. When these significant regions were jointly analyzed, significant task-related clusters emerged for the BNT and Vocabulary test. For the BNT performance, the bilateral MTL and left frontal pole were crucial; for the Vocabulary test, while the left superior temporal cortex and bilateral MTL were important. These results provide evidence that both common (shared across lexical tasks) and distinct regional volume reduction in the left and right hemispheres are associated with performance changes over time on different lexical tasks in cognitively healthy elderly individuals. Beyond the classic language areas determined from aphasiology, far more distributed regions, such as MTL, should be included as part of the lexical network for people experiencing a gradual aging process without prominent brain damage. A combination of common and specific brain regions contribute to maintenance and decline of lexical retrieval and semantic/phonemic processing