Shared mechanisms of object-based attention and object working memory.

Most theories of visual selective attention assume that attention operates on spatial locations. However it is becoming increasingly clear that visual attention may also operate on perceptual groups that result from a preattentive analysis of the visual scene based on Gestalt grouping operations; a form of selection referred to as object-based attention. The studies in this dissertation were designed to characterize the processing components involved in object-based attention and to determine the extent to which object- and space-based attention are dissociable. These issues were investigated by examining the effects of different working memory tasks on the functioning of object-based attention in neurologically intact observers. Neuroimaging and focal lesion studies suggest that object-based attention and object working memory rely on common brain regions in the left posterior parietal cortex. If the overlap between these systems is functional as well as structural, then object working memory should selectively interfere with object-based attention. In contrast, other working memory systems that rely on different brain regions and/or involve different cognitive processes should not interfere. Subjects performed tasks that typically produce an advantage for responding to attributes from one object rather than from two separate objects. These attention tasks were either performed alone or in a dual-task condition with object, verbal, or spatial working memory load. A series of experiments showed that when subjects remembered objects while performing the attention tasks, the single-object advantage was reliably reduced. In contrast, remembering letter names or spatial locations in memory did not interfere with the single-object advantage. However, memory for locations was reliably decreased by the concurrent attention task. These results suggest that the neuropsychological mechanisms that mediate selective attention to objects are also involved in the short-term storage of object representations in working memory. Also, these results are consistent with the possibility that object-based selection involves an activational component responsible for activating representations of objects and a representational component that may also underlie object encoding. Implications of these results for the separability of object- and space-based selection are discussed.PhDCognitive psychologyPsychobiologyPsychologyUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/129938/2/9711920.pd