Component processes, top-down modulation, and interactions between perceptual and reflective processing

Internal thought, or reflection, is the way that human beings process information that they have received via sensory perception or retrieved from memory, potentially distill it into new forms, and eventually transform it into plans for appropriate actions. It is clear that perceptual and reflective processes overlap and interact with one another to some degree, but many of the details of their reciprocal relationship remain to be explored. In this dissertation, we examine questions of how reflective processes may impact subsequent perception of stimuli and/or modulate activity in high-level visual areas of cortex, and to what extent attention processes operate similarly or differently in the perceptual versus reflective domains.;Of course, in its natural setting, human thought is complex, fleeting, and unpredictable, so in many of the experiments contained herein, we use a component-process approach to try to study reflection in a simpler and more controlled setting than is possible when using more complex cognitive tasks. In particular, we examine the effects of refreshing representations that are currently active in working memory by cuing participants to briefly think of, or visualize, items that they were shown just a moment ago. We believe refreshing to be an important component process of many more complex cognitive operations, and to be the reflective equivalent of a shift in perceptual attention.;In Chapter 2, we demonstrate that this simple act of reflective attention can modulate activity in category-selective visual areas. In Chapter 3 we extend this finding to show that when one item is refreshed, reflective attention can actually suppress activity in areas selective for another item that is not refreshed in addition to enhancing activity in areas selective for the refreshed item. In Chapter 3 we also examine areas that are activated in common between perceptual and reflective attention processes or selectively for one type of attention or the other; in addition, we demonstrate a selective impairment in older adults for reflective suppression, but not for reflective enhancement or any form of modulation by perceptual attention.;While Chapters 2 and 3 employed functional magnetic resonance imaging (fMRI), Chapter 4 uses electroencephalography (EEG) to demonstrate that refreshing has a distinct electrophysiological signature and appears to comprise two distinct temporal sub-components. In addition, we examine refreshing across different categories of items and demonstrate that at least a modest amount of category information is contained in the refresh EEG response.;In Chapter 5, we address the question of whether reflectively induced activity in high-level visual areas contains information about the particular exemplar held in mind. Using a mental imagery task and multivariate pattern analysis (MVPA), we demonstrate that exemplar-level information is contained in several scene-selective areas during mental imagery, and furthermore that this information partially re-instantiates patterns of activity that are present during the perception of those exemplars.;Chapter 6 addresses the question of whether reflective enhancement and suppression are truly separable processes (or simply different manifestations of a single process) by examining whether reflective suppression of category-selective cortex can carry over and produce behavioral / neural impairments in perceiving new items from the suppressed category. Chapter 7 takes a different approach to studying the behavioral impact of reflective attention on later perception and demonstrates that in some circumstances, subsequent perception of a refreshed item can actually be impaired, an effect that mirrors the perceptual attention effect known as inhibition of return (IOR).;Finally, Chapter 8 summarizes the results of the studies contained in the preceding chapters, and describes preliminary data from a follow-up experiment based on those findings.