Quantitative and Qualitative Analysis of Verb Fluency Performance in Individuals With Probable Alzheimer's Disease and Healthy Older Adults.

Purpose To date, verb fluency tasks have been mainly analyzed quantitatively for individuals with dementia. Qualitative analysis, however, such as examining the semantic and psycholinguistic content of the responses might further inform researchers and clinicians about patients' cognitive and linguistic status. Therefore, the current study examined psycholinguistic and lexical characteristics of verb fluency responses in individuals with probable Alzheimer's disease (pAD) and healthy older adults to delineate qualitative and quantitative differences between the two groups. Method The verb fluency responses from participants with pAD (amnestic type) were compared to those from age- and education-matched healthy older adults. The responses were analyzed with respect to the number and proportion of correct responses, word frequency, age of acquisition, phoneme and syllable length, and neighborhood density. The verb responses were also categorized into mental state verbs and action verbs. Additionally, a battery of cognitive-linguistic tests was administered, and for each group, relationships between correct verb fluency responses and other cognitive-linguistic skills were investigated using correlation and regression analyses. Results Similar to previous findings regarding noun retrieval in dementia, the results revealed that individuals with pAD not only produced fewer correct verb fluency responses but also generated little to no mental state verbs compared to the control group. The group with pAD also produced verbs with shorter phoneme and syllable lengths, higher word frequency, and earlier age of acquisition ratings relative to the healthy older adults. The number of correct verb fluency responses was mainly predicted by a reading comprehension score in the pAD group and a nonverbal fluency test score in the healthy group. Conclusion The current quantitative and qualitative findings add support to the contention that lexical-semantic impairments underlie word retrieval problems in pAD and such difficulties present in generative naming paradigms and also across grammatical categories.