Neuroimaging attentional control in the Stroop task
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Attention is a cognitive process essential to daily function. As attention encompasses an extremely broad array of cognitive subprocesses, there remains much to be discovered about the brain regions related to attention with neuroimaging. This thesis presents two studies that used functional magnetic resonance imaging to examine neural activity associated with different forms of attentional control. In the first study, we scanned healthy young adults while they performed the Stroop task, which measures selective attention, to investigate neural responses underlying unanticipated conflict detection. We found several regions across the frontal, parietal, and occipital lobes that became more active during states of unanticipated conflicts, relative to states of anticipated conflicts. These regions included the anterior cingulate, dorsolateral prefrontal cortex, angular gyrus, inferior parietal lobule, precuneus, lingual gyrus, and fusiform gyrus. Activity in these regions has previously been associated with attentional processes such as conflict detection, attention, orientation, and oddball detection. Our results therefore suggest that widespread areas of the cortex serve several cognitive processes involved in successfully monitoring and responding to unanticipated conflicts. In the second study, we tested young and cognitively healthy older adults with the Stroop task to determine whether aging affects the neural mechanisms underlying attentional lapses, defined as relatively longer response times. Like previous studies in young adults, we found regions in the default mode network exhibited greater activity as reaction time to stimuli increased. Attentional lapses were also preceded by decreased activity in regions related to attention, including the anterior cingulate and prefrontal cortices. Most importantly, young adults showed greater positive reaction time-modulated activity in default mode areas, while older adults exhibited greater positive reaction time-modulated activity in more prefrontal areas. Our results suggest that the neural correlates of attentional lapses change with healthy aging, reinforcing the idea of functional plasticity to maintain high cognitive function throughout the lifespan.