Sleep Circadian Rhythms
My research addresses questions related to sleep and circadian rhythms. The research ranges from molecular and genetic approaches to behavioral studies in mice and humans. Great progress has been made recently in understanding fundamental aspects of circadian rhythms, but many aspects of sleep are poorly understood. Although sleep occupies approximately one third of our lives, we still cannot answer the basic question of why we sleep. It now appears that most animals have some form of sleep, and birds and mammals generally have two very different kinds of sleep – Rapid-Eye-Movement (REM) sleep and non-REM sleep that may serve different or complementary functions. In addition to fundamental questions about sleep function and sleep regulation, sleep is also of great medical and societal importance. Sleep disturbances afflict approximately 75 million people in the United States alone, and even normal sleepers often get insufficient sleep due to lifestyle factors that can result in serious accidents, poor performance, lowered quality of life, and even grouchiness. Clearly, something about the brain requires sleep and, in our view, genetic approaches in mice provide one of the best opportunities for a better understanding of sleep.
Mice are an excellent model organism for genetic studies because there is a wide diversity of inbred strains. Members of each individual inbred strain are genetically identical, like identical twins in humans, but among different strains there are many different alleles of each gene that contribute to physiological and behavioral differences. We are currently investigating differences in gene expression among these strains for genes that we believe are critical for sleep regulation or sleep function. We also monitor different strains for behavioral differences ranging from total sleep time, to their daily activity patterns. For example, we have one mouse strain called CAST/EiJ that is similar to humans with the clinical condition called Advanced Sleep Phase Syndrome, and wake up much earlier than normal. We have recently identified at least one chromosomal region (or Quantitative Trait Locus) that contributes to this trait, and are now trying to find which of the approximately one hundred genes in this region is the critical one.
A major limitation in all studies of sleep in mice, or any mammal, is the difficulty of performing EEG/EMG analyses. In mice, this requires extensive surgery, recovery, cabling of animals, and considerable time for signal analyses. Therefore, we developed a non-invasive, high-throughput alternative using a piezoelectric film attached to the floor of a mouse cage, and then developed signal processing algorithms to score sleep and wake in real time. This work is being done in collaboration with Prof. Kevin Donohue in Engineering. We currently have our system screening mice at Oak Ridge National Laboratory and other locations to take advantage of the extensive diversity of mice available at these locations, including a large cross that may revolutionize complex genetic studies, called the Collaborative Cross.
In addition to our studies in mice, we are also studying various aspects of sleep, meditation and performance in people, such as whether meditation might provide some of the restoration we normally associate with sleep. We are using a well-validated psychomotor vigilance test that accurately reflects underlying sleepiness. Our data thus far suggest meditation can indeed boost performance, and in a way that appears to compensate or pay-off sleep debt.
Kaul P, J Passafiume, RC Sargent, BF O’Hara. Meditation acutely improves psychomotor vigilance and may decrease sleep need. Behav Brain Functions. 6:47 (pp. 1-9) (2010).
- "Clock genes and sleep homeostasis: a fundamental link within the two-process model?" Sleep 36, 3 (2013): 301-2. Details.
- "Distinct phase relationships between suprachiasmatic molecular rhythms, cerebral cortex molecular rhythms, and behavioral rhythms in early runner (CAST/EiJ) and nocturnal (C57BL/6J) mice." Sleep 35, 10 (2012): 1385-94. Details.
- "Effects of aging and genotype on circadian rhythms, sleep, and clock gene expression in APPxPS1 knock-in mice, a model for Alzheimer's disease." Experimental neurology 236, 2 (2012): 249-58. Details. Full text
- "Behavioral and genetic dissection of a mouse model for advanced sleep phase syndrome." Sleep 34, 1 (2011): 39-48. Details.
- "Genetic analysis in the Collaborative Cross breeding population." Genome research 21, 8 (2011): 1223-38. Details. Full text
- "Effects of ramelteon and triazolam in a mouse genetic model of early morning awakenings." Brain research 1296, (2009): 46-55. Details. Full text
- "Assessment of a non-invasive high-throughput classifier for behaviours associated with sleep and wake in mice." Biomedical engineering online 7, (2008): 14. Details. Full text
- "Genomic and proteomic approaches towards an understanding of sleep." CNS & neurological disorders drug targets 6, 1 (2007): 71-81. Details. Full text
- "Sleepy genes." Frontiers in neuroscience 4, (0): 183. Details. Full text
- "Diffuse brain injury induces acute post-traumatic sleep." PloS one 9, 1 (0): e82507. Details. Full text