Subjective cognitive decline, a perceived worsening of cognitive functioning without objective deficit onassessment, could indicate incipient dementia. However, the neural correlates of subjective... Show moreSubjective cognitive decline, a perceived worsening of cognitive functioning without objective deficit onassessment, could indicate incipient dementia. However, the neural correlates of subjective cognitive decline asassessed by magnetic resonance imaging remain somewhat unclear. Here, we evaluated differences in functionalconnectivity across memory regions, and cognitive performance, between healthy older adults aged 50 to 85 with(n¼35,Age¼68.57.7, 22 female), and without (n¼48,Age¼67.08.8, 29 female) subjective cognitivedecline. We also evaluated neurite density, fractional anisotropy, and mean diffusivity of the parahippocampalcingulum, cingulate gyrus cingulum, and uncinatefiber bundles in a subsample of participants (n¼37). Partic-ipants with subjective cognitive decline displayed lower average functional connectivity across regions of a pu-tative posterior memory system, and lower retrosplenial-precuneus functional connectivity specifically, than thosewithout memory complaints. Furthermore, participants with subjective cognitive decline performed poorer thancontrols on visual working memory. However, groups did not differ in cingulum or uncinate diffusion measures.Our results show differences in functional connectivity and visual working memory in participants with subjectivecognitive decline that could indicate potential incipient dementia. Show less
This thesis investigates the mechanisms of stimulus-driven visual attention (global saliency), the mechanisms of top-down visual attention, and the interaction between these mechanisms, in visual... Show moreThis thesis investigates the mechanisms of stimulus-driven visual attention (global saliency), the mechanisms of top-down visual attention, and the interaction between these mechanisms, in visual search. Following the outline of an existing model of top-down visual attention, namely the Closed-Loop Attention Model (CLAM), simulations in this thesis explore mechanisms of visual working memory in the prefrontal cortex and of object recognition in the ventral pathway, and specify mechanisms of spatial selection in the dorsal pathway. Behavioral experiments additionally address several questions regarding stimulus-driven and top-down visual attention in visual search, and their interaction. The findings of the simulations and behavioral experiments have implications for CLAM in particular, and for the mechanisms of global saliency and top-down visual attention in general. Show less
