Although recent evidence suggests that reward- and attention-based guidance recruit overlapping cortical regions and have similar effects on sensory responses, the exact nature of the relationship between the two remains elusive. Three series of behavioral and fMRI experiments were designed to investigate the precise nature of effects of reward on attentional selection, and to examine flexibility of the reward influences. In the first experimental series, effects of reward on space- and object-based selection were compared. Behavioral and neuroimaging results showed that space-based attentional allocation occurred mandatorily, integrating reward information over time, while object-based attentional allocation was completely replaced by the reward signal. The second experimental series investigated whether reward-based contingency learned in a bottom-up search task is transferred to a subsequent top-down search task. Results demonstrated that reward modulation effect established in a pop-out search task was transferred to a conjunction search task, increasing search efficiency for targets previously associated with higher reward. In the third experimental series, the precise nature of reward-based modulation on neuronal tuning function was investigated. It was found that reward optimizes orientation tuning adaptively to stimulus contexts. These results suggest that reward serves to constrain attentional selection by robustly representing valuable stimuli, and that an integrated priority map, based on reward information, guides both top-down and bottom-up attention.
|Commitee:||Philbeck, John, Rothblat, Lawrence, Sohn, Myeong-Ho, Thothathiri, Malathi|
|School:||The George Washington University|
|School Location:||United States -- District of Columbia|
|Source:||DAI-B 74/10(E), Dissertation Abstracts International|
|Subjects:||Neurosciences, Psychology, Cognitive psychology|
|Keywords:||Attention, Fmri, Neuronal tuning, Reward, Space- and object-based attention, Visual search|
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