ABSTRACT
OBJECTIVE: Bilingualism is discussed as one factor contributing to "cognitive reserve" (CR), as it enhances executive control functions. To elucidate the underlying cerebral correlates, regional glucose uptake was compared between bilinguals and monolinguals with mild cognitive impairment (MCI) and beginning-stage Alzheimer's disease (AD) by using [(18)F]fluorodeoxyglucose (FDG) positron emission tomography (PET). METHODS: Thirty patients (73.2 ± 7.4) diagnosed with MCI or probable AD received physical and neuropsychological examinations, blood tests, and FDG-PET scans. Sixteen patients were classified as lifelong bilinguals, following the criterion of Bialystok et al., and groups were matched for age, sex, and mini mental state examination scores. Analyses were conducted using statistical parametric mapping version 8. The whole brain was used as reference region for intensity normalization and years of education were controlled for. RESULTS: Bilingual patient groups showed substantially greater impairment of glucose uptake in frontotemporal and parietal regions [including Brodmann areas (BAs) 9, 47, 40, and 21] and in the left cerebellum relative to monolingual patients. CONCLUSION: Bilingualism is likely to contribute to CR, given that bilingual patients showed more severe brain changes than monolinguals when adjusting for severity of cognitive impairment. The latter did not only comprise BAs relevant to speech and language but also structures typically involved in AD pathology, such as the temporal and the parietal cortices.
ABSTRACT
Using [(18)F] fluorodeoxyglucose (FDG) positron emission tomography (PET) patients with Alzheimer's disease show impairment of cerebral glucose metabolism in bilateral frontotemporoparietal association cortices and posterior cingulate cortex whereas in patients with mild cognitive impairment (MCI) results are heterogeneous. For the first time, the present study examined alterations of the cerebral glucose metabolism in patients with prodromal AD as compared to patients with AD dementia and healthy controls depending on intensity normalization. 15 patients with AD (69.8±8.5 years) and 28 with prodromal AD (67.4±9.1 years) as well as 10 healthy controls (58.8±5.9 years) underwent FDG PET under resting conditions. By statistical parametric mapping 8, analyses were performed using (a) cerebellar cortex or (b) whole brain as reference region for intensity normalization. Patients with AD dementia showed reductions in bilateral temporoparietal regions and posterior cingulate gyrus as compared to controls. By contrast, patients with prodromal AD had only reductions in the left posterior temporal lobe and left angular gyrus as compared with controls. Cerebellar normalization was superior in differentiating patients with prodromal AD or AD dementia from healthy controls, but global normalization provided slightly better contrasts for the differentiation between patients with prodromal AD and AD dementia in AD-typical regions. Unexpected hypermetabolism in patients was only revealed using global normalization and has to be regarded as an artifact of intensity normalization to a reference region affected by the disease.
