Neural representation of cognitive changes within the visual system in the AD brain

Normal cognitive function requires a high level of interaction among regions of a neural network. The presence of disease pathology will alter the functional network. The visual system is divided into 2 main pathways: (a) a ventral pathway that includes the occipital, temporal and frontal lobes which mediates object processing, (b) a dorsal pathway that includes occipital, parietal and frontal lobes which mediates spatial processing. We used functional magnetic resonance imaging to identify the neural substrates in mild AD patients and age-matched healthy controls. We show activation along the expected neural pathways for the object and location matching tasks in the healthy controls. Alzheimer’s patients recruit more neural areas in both tasks compared to the healthy controls. The differences in patterns of activation between both groups show a cortical reorganization in the AD patients that may be due to presence of the disease.