Sleep deprivation (SD) results in a decline in cognitive performance. Our research uses functional imaging to study the neural correlates of this decline. We wish to understand why and how sleep deprivation affects behavior. We are also interested in why some individuals are better able to maintain cognitive performance when sleep deprived better than others.
The first experiments we performed tested verbal working memory. We were initially interested in how performing a more complex task might result in better maintenance of performance than engaging in a simpler task (Chee and Choo, 2004).
We found that this is the consequence of greater task related frontal lobe activation. The frontal lobe figures prominently in theoretical accounts of why behavior changes after sleep deprivation. We found how sleep deprivation modulates activation in frontal lobe activation to be strongly task and individual dependent.
Later experiments with short-term memory showed that the extent to which parietal lobe activation declines following sleep deprivation corresponds to increased performance variability. Changes in parietal lobe activation appear to be a promising marker of vulnerability to memory decline.
We have found that it may not be memory storage failure per se but decline in attention and visual processing that may underlie performance drops in short term memory after sleep deprivation (Chee and Chuah, 2007). Following up on this work we examined how brain activation is altered when persons make slower responses when sleep deprived (Chee et al., 2008) (Chee et al., 2010). Recently we have extended our work to examine how visual processing capacity is compromised. We found that in accordance with Lavie’s perceptual load model of attention, sleep deprived persons have reduced capacity to process task irrelevant peripheral information (Kong et al., 2010).
Regarding risky decision-making, we found that the nucleus accumbens, an area in the brain that is involved with the anticipation of reward was selectively more active when risky decisions were made under conditions of sleep deprivation. Our findings show how sleep deprivation could pose a double threat to advantageous decision making (Venkatraman et al., 2007). We backed this study up with a newer, sophisticated multiple outcome gamble design and found that in decision and outcome receipt phases, there is altered response to potential rewards, realized rewards and losses (Venkatraman et al., 2011).
By discovering functional imaging markers of SD tolerance, we hope to be able to evaluate interventions designed for individuals who are vulnerable to SD. The first example of this line of research concerns the use of the cholinesterase inhibitor donepezil in ameliorating visual attention deficits in the setting of SD (Chuah and Chee, 2008).
We found fMRI task-related signal change to parallel behavioral changes causing us to be excited about the prospect of using fMRI as a supplementary marker for the evaluation of SD countermeasures.
We hope that our imaging markers may help inform individuals of their suitability for occupations where repeated and prolonged sleep deprivation come with the job.
We are working on some really cool stuff related to multi-voxel pattern analysis of visual attention data (Soon et al., in prep.).
How much sleep do we really need? The BIG question and one we hope to attack together with others when we examine short sleepers…
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For research participants:
If you are healthy, have generally good sleep habits, and are interested to be a participant in one of our sleep studies, please fill in the questionnaire on this page, and we will be in touch with you if you meet our volunteer requirements.