Motivational incentives enhance top-down modulation of visual spatial attention in healthy aging and mild cognitive impairment but not probable Alzheimer's disease

The goal of this dissertation was to examine the influence of motivational incentives on visual spatial attention in patients with probable Alzheimer's Disease (PRAD), patients with mild cognitive impairment (MCI) and healthy age-matched control subjects (EC). Specifically, I compared the ability of monetary incentives to influence behavioral and neural performance on a covert visual spatial attention task while participants were scanned using functional magnetic resonance imaging (fMRI). A volumetric MRI study was also conducted to test for potential group differences in brain atrophy. The results from the experiments presented in this dissertation reveal that: (1) motivational incentives can influence top-down modulation of visual spatial expectancy in EC and MCI, but not PRAD; (2) the enhancement of spatial expectancy by incentives is regulated by the PCC in the EC and MCI subject groups; (3) disengaging attention is specifically impaired in the PRAD population; (4) EC, but not MCI or PRAD subjects can disengage and reorient attention quicker when incentives are present; (5) the OFC controls the influence of motivation on disengagement; and (6) hippocampal atrophy and the associated memory impairments in the PRAD group may account for the inability of monetary incentives to enhance spatial attention in this population. I conclude that monetary incentives are effective in motivating elder controls and MCI subjects to enhance visual spatial attention processes and that the PCC and OFC areas responsible for this enhancement are the same as those in young adults.