My research interests broadly entail the processes during sleep that are important for health and cognitive functions. Additionally, my work investigates how autonomic and central nervous system factors interact to produce regulatory effects on sleep-dependent health and cognitive enhancement. Further, by harnessing physiological biomarkers during sleep, my work aims to develop interventional tools that target at sleep and counteract age-related cognitive/ physiological declines.
The impact of sex hormones on neural correlates of sleep-dependent working memory and long-term memory changes.
Sex hormones strongly modulate sleep spindles and vagal autonomic activity. During the mid-luteal phase, women show greater amplitudes of spindles and lower vagal activity. During the early follicular phase, women show lower amplitudes of spindles and higher vagal activity. The fluctuations of central and autonomic signals parallel with our recent findings, implicating a trade-off between sleep-dependent long-term and working memory processes (Chen et al., 2021). In this project, we test women participants’ overnight sleep and sleep-dependent cognitive changes during their mid-luteal phase (high sex hormone) and their early follicular phase (low sex hormone). We utilize functional brain imaging techniques to investigate the neural trade-offs supporting sleep-dependent long-term and working memory plasticity.
Heart-Brain Interaction Modulated by Sleep and Aging
Both autonomic and sleep dysregulation have been separately implicated in age-related and pathological cognitive decline. My research focuses on examining brain-body communication, and how this interaction can be a distinct predictor or biomarker of plasticity, cognitive ability and enhancement.
Trade-off between Frontal-Subcortical Working Memory and Hippocampal Episodic Memory Processing during Sleep
Recent discoveries suggest the intriguing possibility that LTM consolidation relies on central sigma activity, whereas WM improvement relies on autonomic vagal processes. However, it remains unclear whether these two mechanisms are independent or counteracting. Here, we exploited zolpidem to boost sigma activity and observed a decrease in vagal activity. Using effective connectivity, we found that central sigma activity exerted greater causal influence on autonomic tone, and such influence can be enhanced by zolpidem. Our findings indicate that Non-rapid-eye-movement (NREM) sleep toggles between spindle-dependent and vagal-dependent processes, supporting time for the enhancement of both LTM and WM during sleep via separate mechanisms.
Hacking Sleep for Better Memory Using Brain Stimulation
A great body of research shows that aging is characterized by a decline in executive functions, long-term memory, brain atrophy, impaired sleep, as well as decreased vagal tone. Both autonomic and sleep dysregulation have been separately implicated in age-related and pathological cognitive decline. Yet, few practical treatment options have emerged from either area alone. My research aims to develop unique non-invasive, sleep-focused interventions to counteract cognitive decline.
REM Sleep and Memory Consolidation
Studies on memory consolidation has focused on NREM sleep. My research explores the roles of Rapid-eye-movement (REM) sleep on sleep dependent memory changes. We found bursts activity of Alpha, Beta, and Theta during REM, which may play a key role in procedural learning.
