语音回路和视空间模板对音位流畅性和语义流畅性的影响

采用双任务范式,通过四种次任务考察了工作记忆两个子系统－语音回路和视空间模板对音位流畅性和语义流畅性的影响。实验1表明,主动产生系列发音和被动聆听声音判断对音位流畅性影响更大,表明音位流畅性更依赖于语音回路。实验2表明,字形匹配和字形旋转判断对语义流畅性影响更大,表明语义流畅性更依赖于视空间模板。研究还表明,被试完成音位流畅性任务的策略更易受语言的特点影响,完成语义流畅性任务的策略更易受概念系统的特性影响     

Category size effects in semantic and letter fluency in Alzheimer's patients

Many studies have found that patients with Alzheimer's disease (AD) perform significantly worse than normal controls on verbal fluency tasks. Moreover, some studies have found that AD patients' deficits compared to controls are more severe for semantic fluency (e.g., vegetables) than for letter fluency (e.g. words that begin with F). These studies, however, have not taken category size into account. A comparison of AD patients and age-matched controls on three semantic and three letter categories revealed that both the size and type of a category significantly predicted AD patients' deficits on verbal fluency tasks. These results suggest that the verbal fluency of AD patients will be most attenuated on large semantic categories.     

Differential impacts of age of acquisition on letter and semantic fluency in Alzheimer's disease patients and healthy older adults

The degree to which the typical age of acquisition (AoA) of words and word frequency have separable influences on verbal production tasks has been strongly debated. To examine the overlap between these factors in verbal fluency tasks, the performance of Alzheimer's disease (AD) patients (N?=?34) and normal elderly controls (N?=?36) was compared on semantic (e.g., vegetables) and letter (e.g., words that begin with F) fluency tasks. These comparisons revealed that words generated for the semantic fluency task had an earlier AoA while words generated for the letter fluency task had a higher word frequency. Differences in AoA between AD patients and controls were larger for semantic than letter fluency. These results suggest that AoA has an effect on verbal production that is independent of word frequency and that AoA has a semantic locus.     

Verbal fluency over time as a measure of automatic and controlled processing in children with ADHD

The performance of ADHD children on semantic category fluency (SCF) versus initial letter fluency (ILF) tasks was examined. For each participant, word production was recorded for each 15-s time slice on each task. Performance on both fluency tasks was compared to test the hypothesis that children with ADHD are characterized by a performance deficit on the ILF task because performance on this task is less automated than performance on the SCF. Children classified with ADHD (N = 20) were compared to children with other psychopathology (N = 118) and healthy controls (N = 130). Results indicated that the groups could not be differentiated by the total number of words produced in 60 s in either fluency task. As hypothesized, a significant interaction of group by productivity over time by type of fluency task was found: ADHD children had more problems finding words in the first 15 s of the IFL than did children in the other two groups, and as compared with their performance on the SCF. Results were taken to indicate that children with ADHD symptoms show a delay in the development of automating skills for processing abstract verbal information.     

Children's word fluency strategies

Two word fluency tasks, the FAS letter fluency task and the "animal" semantic fluency task, were administered to 130 healthy Swedish-speaking children between 6 and 15 years of age. The main aim was to gather normative data on these word fluency tasks for Swedish-speaking children. Another purpose was to examine the switching and clustering strategies used, along with the occurrence of erroneous responses, in relation to demographic data and number of words retrieved. Both phonological and semantic analyses of switching and clustering were conducted. Higher age was found to be related to a more effective use of phonological and semantic switching and clustering strategies. The reference data resulting from this study may be of clinical value in examinations of children with various diagnoses, including language impairment.     

Pervasive influence of semantics in letter and category fluency: a multidimensional approach

We used multidimensional statistical procedures to study semantic and lexical processes underlying word retrieval in verbal-fluency performance. Forty healthy participants were given a two-choice letter task (i.e., generate items beginning with the letter 'A' or 'F', in any order) and a two-choice category task (i.e., generate animal or fruit names, in any order). Using correspondence analysis (CoA) and hierarchical clustering (HC), we found evidence of prominent semantic organization in both letter and category fluency. For example, a striking categorical segregation between animate and inanimate entities emerged during the letter task. Analysis of inter-item times revealed strong sequential priming effects in both tasks. Taken together, these results indicate that semantic facilitation is pervasive in word retrieval processes, even in the letter-fluency task, and therefore suggest that the traditional view of letter fluency as a purely phonemically based task should be revised. Finally, our findings may help explain patterns of verbal-fluency measures obtained in focal brain lesion patients.     

Shared lesion correlates of semantic and letter fluency in post-stroke aphasia

Lesion–symptom mapping studies have reported a temporal versus frontal dissociation between semantic and letter fluency, and mixed evidence regarding the role of white matter. Mass-univariate and multivariate lesion–symptom mapping was used to identify regions associated with semantic and letter fluency deficits in post-stroke aphasia. Multivariate LSM revealed broad networks including underlying white matter, and substantial overlap between both types of fluency, suggesting that semantic fluency and letter fluency largely rely on the same neural system. All data are available on OSF.     

Verbal fluency output in children aged 7-16 as a function of the production criterion: qualitative analysis of clustering, switching processes, and semantic network exploitation

Developmental changes in children's verbal fluency were explored in this study. One hundred and forty children aged from 7 to 16 completed four verbal fluency tasks, each with a different the production criterion (letter, sound, semantic, and free). The age differences were analyzed both in terms of number of words produced, and clustering, switching, and semantic network exploration. Analysis of the number of words produced showed a larger difference between the 7-8- and the 9-10-year-olds in semantic than in letter fluency, but this difference gradually disappeared with increasing age for semantic fluency while remaining constant for letter fluency. In letter fluency production, age modified both the number of switches and clusters formed whereas in semantic fluency tasks, only cluster size changed with age. Concerning the semantic network exploration indicators derived from the supermarket fluency task, the number of categories sampled increased from 11 to 12 years, but efficient semantic exploitation occurred only after the age of 13-14 years. These results are discussed in terms of the development of strategic retrieval components and categorical knowledge.     

注意控制和短时存储对音位流畅性和语义流畅性的影响

工作记忆的中央执行系统具有注意控制和短时存储的功能。采用双任务范式,探讨了中央执行系统的注意控制和短时存储对言语流畅性的影响。实验1考察了中央执行系统的转换和抑制功能对音位流畅性和语义言语流畅性的影响。结果表明,中央执行系统的转换和抑制功能对两种言语流畅性的影响相当。实验2考察了中央执行系统的注意控制资源和短时存储资源对两种言语流畅性的影响。结果表明,语义流畅性更依赖于短时存储资源,音位流畅性更依赖于注意控制资源。研究还发现,被试完成语义流畅性任务的策略更易受概念系统的特性影响,完成音位流畅性任务的策略更易受语言的特点影响。在实验研究的基础上,作者提出了工作记忆影响言语流畅性的理论模型     

Monitoring the Changing Status of Semantic Memory in Alzheimer's Disease: An Evaluation of Several Process Measures

The deficits in generating correct words on verbal fluency tasks exhibited by patients with Alzheimer's disease (AD) are accompanied by fewer switching responses, smaller phonemic and semantic cluster sizes, and greater than normal percentages of errors and category labels. On category fluency tasks, patients generate a greater proportion of words that are prototypical of their semantic class. To determine whether any of these supplementary measures of verbal fluency performance might be useful in revealing processes involved in the decline of semantic memory in AD, we studied 219 patients with AD and 115 elderly control participants longitudinally. Previously reported group differences between patients and controls were replicated, but changes in average cluster size, error rates, and prototypicality were not related to changes in overall severity of dementia and test-retest stability was only modest. The change in the percentage of labels generated on the Supermarket task was related to changes in dementia severity, but test-retest stability on this measure was quite low. All of these process measures appear to reflect only the current status of the patient's attention to the task and access to semantic knowledge, but they do not forecast future performance. The numbers of switching responses on the fluency tasks were sensitive to differences between clinically deteriorated and clinically stable patients and showed fairly high test-retest stability. However, the number of switching responses is so highly correlated with the number of correct words that it contributes little to the understanding of the processes involved in the progressive decline in performance on fluency tasks by patients with AD.     

Differential impacts of age of acquisition on letter and semantic fluency in Alzheimer's disease patients and healthy older adults

The degree to which the typical age of acquisition (AoA) of words and word frequency have separable influences on verbal production tasks has been strongly debated. To examine the overlap between these factors in verbal fluency tasks, the performance of Alzheimer's disease (AD) patients (N = 34) and normal elderly controls (N = 36) was compared on semantic (e.g., vegetables) and letter (e.g., words that begin with F) fluency tasks. These comparisons revealed that words generated for the semantic fluency task had an earlier AoA while words generated for the letter fluency task had a higher word frequency. Differences in AoA between AD patients and controls were larger for semantic than letter fluency. These results suggest that AoA has an effect on verbal production that is independent of word frequency and that AoA has a semantic locus.     

Bilingualism and reading difficulties: an exploration in episodic and semantic memory

This study was designed to investigate the effect of bilingualism and reading difficulties (RD) on episodic and semantic memory. The subjects included 190 children (aged 9–12 years): 45 Iranian-Swedish bilinguals and 59 Swedish monolinguals with typically developed reading, along with 41 bilinguals and 45 monolinguals with RD. To measure episodic memory, subject-performed and verbal tasks were used for encoding, and both free and cued recall were used for retrieval. Letter and category fluency tasks were used to test semantic memory. In action memory, bilingual children with RD benefited less from enactment encoding form compared to children with typically developed reading. Additionally, bilingual with RD had lower rates of recollection in category fluency compared to their monolingual counterparts. However, in letter fluency, there was not found a difference between performances of bilinguals and monolinguals with RD. We discuss the involvement of long-term memory in both bilingualism and reading.     

Performance on a measure of category fluency in cognitively impaired elderly

ABSTRACT

Measures of verbal fluency are widely used in the assessment of cognitive functioning of the elderly. However, limited research has evaluated patterns (across specific timed intervals) of performance on tasks of language fluency in different forms of dementia. The current study investigated semantic fluency in 488 elderly individuals (249 with Alzheimer's dementia, 97 Vascular dementia, 97 Mild Cognitive Impairment and 45 cognitively intact) across 15-second intervals in an animal naming task using retrospective chart review. Normal controls produced significantly more exemplars and AD patients produced fewer animal names than the other groups. After the first 15- second time interval, the demented groups produced significantly fewer exemplars than the non-demented. At the end of 30 seconds it was possible to differentiate normal aging from MCI who no longer differed from the VaD group. Overall, it appears that the greatest and most clinically meaningful differences between the diagnostic groups were detected in the first three 15-second intervals. The present findings support the use of time intervals and total scores on tasks of verbal fluency in clinical settings and for research purposes.     

Divergent thinking in Alzheimer's and frontotemporal dementia

Twenty-three patients with mild dementia of the Alzheimer's type (DAT) or frontotemporal type (DFT) and age- and education-matched control subjects were administered tests of complex fluency involving divergent thinking and tests of letter, category, and figural fluency. The tests of complex fluency discriminated the dementia patients from control subjects more strongly than did the other fluency tests. The results suggest that divergent thinking as assessed by complex fluency tests is a cognitive domain that is impaired early in the course of dementia. The sensitivity of complex fluency tests compared to that of letter, category, and figural fluency tests may be related to greater demands for conceptualization in relating stimulus attributes to function and greater demands for flexible thinking during self-directed search processes.     

Divergent Thinking in Alzheimer's and Frontotemporal Dementia

Twenty-three patients with mild dementia of the Alzheimer's type (DAT) or frontotemporal type (DFT) and age- and education-matched control subjects were administered tests of complex fluency involving divergent thinking and tests of letter, category, and figural fluency. The tests of complex fluency discriminated the dementia patients from control subjects more strongly than did the other fluency tests. The results suggest that divergent thinking as assessed by complex fluency tests is a cognitive domain that is impaired early in the course of dementia. The sensitivity of complex fluency tests compared to that of letter, category, and figural fluency tests may be related to greater demands for conceptualization in relating stimulus attributes to function and greater demands for flexible thinking during self-directed search processes.     

Variation in verbal fluency: A latent variable analysis of clustering,switching, and overall performance

Verbal fluency tasks have long been used to assess and estimate group and individual differences in executive functioning in both cognitive and neuropsychological research domains. Despite their ubiquity, however, the specific component processes important for success in these tasks have remained elusive. The current work sought to reveal these various components and their respective roles in determining performance in fluency tasks using latent variable analysis. Two types of verbal fluency (semantic and letter) were compared along with several cognitive constructs of interest (working memory capacity, inhibition, vocabulary size, and processing speed) in order to determine which constructs are necessary for performance in these tasks. The results are discussed within the context of a two-stage cyclical search process in which participants first search for higher order categories and then search for specific items within these categories.     

Semantic and Phonemic Verbal Fluency in Blinds

A person who has suffered the total loss of a sensory system has, indirectly, suffered a brain lesion. Semantic and phonologic verbal fluency are used for evaluation of executive function and language. The aim of this study is evaluation and comparison of phonemic and semantic verbal fluency in acquired blinds. We compare 137 blinds and 124 sighted people in verbal fluency task. The tasks were phonemic and semantic verbal fluency test that subjects should be generate as many word as possible in a limited amount of time for a given letter (Phonemic fluency) or a given category (Semantic fluency). Independent T Test was used to comparing blind with sighted. Findings show significant difference between two groups so that that sighted subjects have higher performance in semantic verbal fluency task (p = 0.000). Comparing sighted and blind subjects in phonemic verbal fluency task shows performance in sighted subjects (p = 0.000). Based on this study blinds have lower performance in semantic and phonemic verbal fluency task as a executive function of frontal lobe.     

Letter and Category Fluency in Normal Elderly Participants: a Population-Based Study

We studied variables influencing category and letter fluency in a large population-based sample of elderly participants. Letter and category fluency tasks were administered to 1133 unselected non-demented elderly participants in the Paquid cohort on normal and pathological aging. Age, education, principal lifetime occupation and depressive symptomatology independently influenced both category and letter fluency, while gender influenced only category fluency. A conceptualization measure (similarities) was found to influence fluency results mostly through education and prior occupation.     

Why do older adults have difficulty with semantic fluency?

Aging involves many cognitive declines, particularly in fluid intelligence, with relative maintenance of crystallized intelligence. This paradox is evident in the language domain: lexical retrieval becomes slower and less accurate, despite well preserved vocabularies. Verbal fluency assesses both crystallized and fluid aspects of language. Semantic fluency hypothetically reflects semantic knowledge, while letter fluency putatively reflects executive functioning, which would predict a greater impact of aging on the latter. However, the opposite is typically observed.

To investigate factors contributing to such asymmetries, we examined verbal fluency in 86 adults (30-89 years). Multiple regression analyses indicated that semantic fluency depends largely on lexical retrieval speed, as well as visualization strategies to support controlled retrieval, skills which may disproportionately decline with age. By contrast, letter fluency relies heavily on vocabulary knowledge, providing some protection against age-related declines. These findings contribute to our understanding of the mechanisms of typical age-related declines in word retrieval.     

The deterioration of semantic memory in Alzheimer's disease.

Semantic memory impairment is a common feature of dementia of the Alzheimer type (DAT). Recent research has shown that patients with DAT are more impaired (relative to non-demented controls) in generating exemplars from a particular semantic category (e.g., animals) than words beginning with a particular letter, exhibit an altered temporal dynamic during the production of category exemplars, are impaired on confrontation naming tasks and make predominantly superordinate or semantically related errors, consistently misidentify the same objects across a variety of semantic tasks, and have alterations in multi-dimensional scaling models of their semantic network that are indicative of a loss of concepts and associations. These results are consistent with the view that Alzheimer's disease results in a breakdown in the organization and structure of semantic knowledge as neurodegeneration spreads to the association cortices that presumably store semantic representations.