Relationship between regional cerebral blood flow and verbal fluency in Alzheimer's disease

Abstract

Category and letter verbal fluency tests are widely used for dementia detection and severity measure. Performances of these tasks have been regarded to be mainly associated with the left frontal lobe function. However, some recent studies suggest that there are different neuropsychological bases between these two tasks, and the brain region which contributes to these performances still remains unclear in Alzheimer's disease (AD). To clarify the neural basis of verbal fluency in AD, we examined the relationship between performances of these tasks and regional cerebral blood flow (rCBF). Twenty-five AD patients were administered verbal fluency tasks and single photon emission computed tomography (SPECT) scans. Thirteen cortical regions of interest were symmetrically defined in each hemisphere. Letter fluency scores were correlated significantly only with the left prefrontal (Brodmann's area (BA) 10-46) regional cerebral blood flow (rCBF). In contrast, category fluency scores were correlated most strongly with the left temporal rCBF and also with the left prefrontal (BA 10-46) rCBF. In conclusion, the present study suggests that left prefrontal (BA 10-46) dysfunction contributes to decline in both letter and category fluency scores in AD, while typical posterior dysfunction of AD has a closer relationship with decline in category fluency scores.

Neuropsychological Predictors of Incident Dementia in Patients With Vascular Cognitive Impairment, Without Dementia

“…6,29 Perhaps these results are not surprising, given that almost half of the surviving cases who progressed to dementia were diagnosed with AD or mixed AD at follow-up. It should be noted, however, that in the neuroimaging literature, both letter and category fluency tasks have been found to activate left prefrontal areas, 30,31 although category fluency also activates left temporal structures, 31,32 in general accordance with our results.…”

“…6,29 Perhaps these results are not surprising, given that almost half of the surviving cases who progressed to dementia were diagnosed with AD or mixed AD at follow-up. It should be noted, however, that in the neuroimaging literature, both letter and category fluency tasks have been found to activate left prefrontal areas, 30,31 although category fluency also activates left temporal structures, 31,32 in general accordance with our results.The relative severity of memory deficits predicted progression to dementia even among those patients who had overt memory impairments at baseline but were excluded from a diagnosis of dementia either because they lacked functional impairment or other cognitive impairment. This suggests that our findings do not simply reflect the progression of preclinical memory deficits at baseline to overt memory deficits at follow-up that are required by definition for a diagnosis of dementia.…”

Domain-Specific Improvement of Cognition on Memantine in Patients with Alzheimer’s Disease Treated with Rivastigmine

“…Verbal fluency tests are regarded as tests to assess frontal lobe function. Left prefrontal dysfunction contributes to decline in both letter and category fluency scores in AD, while typical posterior dysfunction of AD has a closer relationship with decline in category fluency scores [46] . However, medial temporal lobe structures are also involved.…”

Association between Cognitive Impairment and Gait Disturbance in Patients with Idiopathic Normal Pressure Hydrocephalus

“…The scores of serial 7 subtest of the MMSE and category fl uency subtest of the verbal fl uency test of patients with iNPH were lower than those of patients with AD, although the differences were not signifi cant. The category fl uency subtest is not considered a pure frontal lobe test because it requires posterior lobe function [20] or temporal lobe function [21,22] as well as frontal lobe function. The absence of a signifi cant difference between the two groups on the serial 7 subtest appeared to be due to the fact that AD patients were matched to the patients with iNPH on the basis of the MMSE score.…”