Mental calculation impairment in Alzheimer's disease: a functional magnetic resonance imaging study

This functional MRI study investigates cerebral activations during mental arithmetic performance, in patients diagnosed with probable Alzheimer's disease (with mild to moderate severity) and age-matched healthy controls. The arithmetic task consisted in three-digit addition and subtraction problems. The task elicited bilateral parietal and prefrontal activations in the control group, in agreement with previous imaging studies of mental arithmetic. In the Alzheimer group, inferior parietal and lateral prefrontal activations were significantly reduced when compared to controls (corrected P < 0.05 ). This important reduction of activity was likely responsible for the patients' poor performance in the task. These results confirm the deficit in calculation abilities, which occurs early in Alzheimer's disease, and provide additional knowledge of the neural mechanisms underlying this impairment.