Michael W. L. Chee

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Brain activations associated with semantic processing of visual and auditory words were investigated using functional magnetic resonance imaging (fMRI). For each form of word presentation, subjects performed two tasks: one semantic, and one nonsemantic. The semantic task was identical for both auditory and visual presentation: single words were presented(More)
Using fMR adaptation, we studied the effects of aging on the neural processing of passively viewed naturalistic pictures composed of a prominent object against a background scene. Spatially distinct neural regions showing specific patterns of adaptation to objects, background scenes, and contextual integration (binding) were identified in young adults.(More)
The neurobehavioral effects of 24 hr of total sleep deprivation (SD) on working memory in young healthy adults was studied using functional magnetic resonance imaging. Two tasks, one testing maintenance and the other manipulation and maintenance, were used. After SD, response times for both tasks were significantly slower. Performance was better preserved(More)
Removal of non-brain tissues, particularly dura, is an important step in enabling accurate measurement of brain structures. Many popular methods rely on iterative surface deformation to fit the brain boundary and tend to leave residual dura. Similar to other approaches, the method proposed here uses intensity thresholding followed by removal of narrow(More)
Lapses of attention manifest as delayed behavioral responses to salient stimuli. Although they can occur even after a normal night's sleep, they are longer in duration and more frequent after sleep deprivation (SD). To identify changes in task-associated brain activation associated with lapses during SD, we performed functional magnetic resonance imaging(More)
STUDY OBJECTIVES Using a gambling task, we investigated how 24 hours of sleep deprivation modulates the neural response to the making of risky decisions with potentially loss-bearing outcomes. DESIGN Two experiments involving sleep-deprived subjects were performed. In the first, neural responses to decision making and reward outcome were evaluated. A(More)
Behavioral differences in the visual processing of objects and backgrounds as a function of cultural group are well documented. Recent neuroimaging evidence also points to cultural differences in neural activation patterns. Compared with East Asians, Westerners' visual processing is more object focused, and they activate neural structures that reflect this(More)
PURPOSE OF REVIEW The review summarizes current knowledge about what fMRI has revealed regarding the neurobehavioral correlates of sleep deprivation and sleep-dependent memory consolidation. RECENT FINDINGS Functional imaging studies of sleep deprivation have characterized its effects on a number of cognitive domains, the best studied of these being(More)
Sleep deprivation (SD) impairs short-term memory, but it is unclear whether this is because of reduced storage capacity or processes contributing to appropriate information encoding. We evaluated 30 individuals twice, once after a night of normal sleep and again after 24 h of SD. In each session, we evaluated visual memory capacity by presenting arrays of(More)
Sleep deprivation results in the loss of our ability to suppress a prepotent response. The extent of decline in this executive function varies across individuals. Here, we used functional magnetic resonance imaging to study the neural correlates of sleep deprivation-induced differences in inhibitory efficiency. Participants performed a go/no-go task after(More)