Dissociation in Age-Related Developmental Trajectories Between Phonetic Fluency and Semantic Fluency Tests: Analysis of Longitudinal Data From the Yakumo Study

Possible age-related differences in Phonemic Fluency Test (PFT) and Semantic Fluency Test (SFT) performance were examined by using longitudinal data of healthy older adults. The performance trajectories of 81 older adults in the 2 tests were analyzed for 11 years, from 65 to 75 years of age, via individually calculated linear regression coefficients. The results indicated that the PFT and SFT performance showed an age-related decline. However, the declining slope of the SFT was steeper than that of the PFT performance. These findings correspond with those of previous cross-sectional studies and suggest a future need to examine neurobiological substrates underlying the two domains of verbal fluency abilities.

Relation between cognitive and cerebello-thalamo-cortical functions in healthy elderly people: Evidence from the Yakumo Study

Relations between cognitive and cerebello-thalamo-cortical functions in healthy elderly people (65-75 years old) were examined by longitudinal behavioral data. Based on the individually calculated cognitive decline ratio in D-CAT (digit cancelation test) and in LMT (Logical Memory Test) during the period of 11 years, participants were classified into the Decline and the Maintain groups and group differences in the postural tremor measures (Quotient of Romberg) were compared. Significant group differences were shown in the postural tremor measure in D-CAT that reflects prefrontal function, but it was not the case in LMT. These results strengthened our previous findings that suggest a strong relation between the cerebello-thalamo-cortical function and the prefrontal cortex function using behavioral measures. Findings provide evidence that to strengthen postural function such as physical exercise is effective for slowing cognitive decline with age.