Altered verbal working memory process in patients with Alzheimer's disease: an fMRI investigation.

Impaired working memory processing is one of the broad range of cognitive deficits in patients with Alzheimer's disease (AD). We aimed to elucidate the differences in brain activities involved in the process of working memory between AD patients and healthy comparison subjects. Twelve patients with AD were recruited along with 12 healthy volunteers as a comparison group. Functional magnetic resonance imaging was employed to assess cortical activities during the performance of a 1-back working memory paradigm using the Korean alphabet as mnemonic content. Subsequently, the difference in neural activities between the 2 groups was analyzed. The AD group performed the tasks with reduced accuracy. Group comparison analysis revealed that the AD group showed decreased brain activity in the left frontal pole (Brodmann area, BA, 10), the left ventrolateral prefrontal cortex (BA47), the left insula (BA13) and the right premotor cortex (BA6) compared to the control group. The AD group showed increased activation in the left precuneus (BA7) compared to the control group. A decreased level of activation in the prefrontal cortex and an increased level of activation in the parietal neural networks from the patient group may document an altered verbal working memory process in the patients with AD.