Dmitry Gerashchenko - US grants

DESCRIPTION (provided by applicant): Synchronization of neuronal activity within and across brain regions is a fundamental property of cortical and subcortical networks needed for normal brain functions. Synchronization of electroencephalogram (EEG) in the frequency range of 1-4 Hz, referred to as slow wave activity (SWA), is observed during slow wave sleep and is thought to be essential for the recuperative function of sleep. Recent work in our laboratory found that changes in SWA parallel the changes in the activity of neuronal nitric oxide synthase (nNOS)-immunoreactive cells in the cortex in three mammalian species. These results suggest that nNOS neurons in the cortex are part of the brain circuit that is involved in the generation of SWA. Since SWA is an established marker of the homeostatic sleep drive, the nNOS neuronal circuit is expected to be activated by homeostatic mechanisms. The proposed studies will test the following hypotheses: (1) changes in the activity of nNOS cells in the cortex correlate with SWA, (2) changes in the activity of nNOS cells in the cortex are independent of circadian input from the suprachiasmatic nucleus, (3) anatomical properties of nNOS cells are consistent with the role of these neurons in EEG synchronization, (4) nitric oxide production by nNOS is involved in SWA generation, and (5) selective ablation of nNOS cells leads to disturbances in SWA production and sleep homeostasis. This research will be a first step in characterizing newly discovered sleep-active neurons in the cortex. It will provide important information about regulation of brain activity by nNOS neurons and may advance our understanding not only of the pathophysiology of sleep disorders, but also of neurological and psychiatric diseases that involve the cerebral cortex. PUBLIC HEALTH RELEVANCE: Research on the role of sleep-active neurons recently discovered in the cerebral cortex will provide new information about regulation of brain activity. An understanding of the functions and mechanisms of these neurons may lead to new approaches for treating a variety of neurological and psychiatric diseases involving the cerebral cortex, as well as for ameliorating common sleep disorders.

? DESCRIPTION (provided by applicant): Electroencephalographic slow-wave activity (SWA) is an electrophysiological signature of slow (0.5 to 4.0 Hz), synchronized, oscillatory neocortical activity. Changes in SWA have been reported in a wide range of neurodevelopmental disorders, such as Angelman syndrome, Down syndrome, fragile-X syndrome, and schizophrenia. These disorders are believed to be caused by developmental defects in brain connectivity. The causal link between cognitive impairments and SWA has not been established yet, but it is likely to be related to anatomical and functional abnormalities at the synapse level. Performance of learning tasks involving the cortical regions produces a local increase in SWA and is associated with branch-specific formation of dendritic spines after learning. Therefore, defects in the neuronal ensemble dynamics that underlie SWA could result in learning dysfunctions. Activity of neuronal nitric oxide synthase (nNOS) cells in the cerebral cortex correlates with SWA, and SWA production is disturbed in nNOS knockout mice. Based on these results, we hypothesize that nNOS neuronal circuits in the cortex are required for both normal cognitive functions and SWA production. According to our hypothesis, nNOS cells become activated during sleep in the cortical regions that have been involved in active processing of information during wakefulness. The activation of these nNOS cells leads to local nitric oxide (NO) production, which affects the pattern of neuronal activity, resulting in enhanced SWA and memory consolidation. We will test this hypothesis by measuring SWA and memory in the novel object recognition task following 1) the activation of nNOS-expressing cells in the vmPFC and 2) rescuing the nitric oxide production by nNOS-expressing cells in the ventromedial prefrontal cortex (vmPFC) in nNOS knockout mice. These studies will contribute to better understanding of the mechanisms of SWA production and memory consolidation and help to develop new treatments in a wide range of cognitive disorders.

The broader impact/commercial potential of this Small Business Technology Transfer (STTR) Phase I project is to improve people's lives by creating the first wrist-based device that can reliably assess sleep quality. A large pool of undiagnosed patients and the growing population of the elderly point to a massive end-user market for sleep disorder diagnostics devices. The market is steadily increasing due to the visible tilt in preference from drugs to home care sleep tests that are more convenient and lack side effects. This trend is also due to improvements in consumer based sensor technology, limited number of technicians or specialized physicians, and long wait times. In accordance with these market needs, this project is designed to develop a system for assessing sleep at home in a patient friendly and easy to environment. This technology is expected to be especially attractive to elderly patients looking for alternatives to medications and traditional sleep disorder tests. Because the algorithm developed in this project will be tested and validated in a sleep laboratory, it will be accepted in both clinical and non-clinical setting.

The proposed project is a research and development effort to create and test a new system for detecting sleep stages. Because poor sleep is common in modern society and has considerable consequences, including decreased work productivity/abilities, increased rate of accidents and traffic fatalities, and increased health care costs, there is a great need for a new system that can provide an ambulatory assessment of sleep quality under real-world conditions. Although there are many wrist-based devices on the market that are well-suited for measuring sleep in both home and clinical settings, none of these devices can currently allow reliable assessment of sleep quality. This project will develop a new algorithm for a wrist-based device that will detect sleep quality based on actigraphy, photoplethysomnography, and physiological responses to sensory stimulation. This research will apply a multi-modal approach to assess quality of sleep and advance the science of diagnosis and treatment of sleep disorders.

ABSTRACT Poor sleep and memory problems are common in older adults and have considerable consequences including decreased productivity, declines in cognitive abilities, increased rate of accidents and traffic fatalities, and increased health care costs. These sleep and memory problems often occur in midlife and in older adults, when aging is associated with insomnia, fragmentation of sleep, and impairment of attention. Aging also impacts sleep stages and sleep depth, with marked changes in non-rapid eye movement (NREM) sleep, an increase in lighter NREM sleep stages (N1 or N2 stage of sleep) and a decrease in deep or ?slow wave? sleep (N3 stage of sleep). Because deep sleep has been associated with the recuperative function of sleep, memory consolidation, and growth hormone release, age-related reduction in deep sleep has a negative impact on physiologic restoration, memory, and overall health. The overall objective of this proposed research is to develop a non-pharmacological means to address sleep deficiencies and well- being in older midlife adults. Several laboratory studies recently demonstrated that precisely-delivered, specific auditory stimulation in adults results in an enhancement of slow waves on the electroencephalogram (EEG) and improvement in memory. Since older adults have a significant reduction in deep sleep, increasing slow wave production by precisely-delivered auditory stimulation could be particularly useful for this population. To date, the use of auditory stimulation to improve sleep has been limited to adult volunteers in laboratory settings. Our objective is to validate, modify, and improve the application of specific auditory stimulation to increase deep sleep in older individuals, and to develop a system that can deliver slow wave sleep enhancement in the home. Both healthy people and patients with disturbances of sleep and memory could benefit from using this system. It will be especially useful in older people. Our new system will be inexpensive, simple and easy to use.

We propose to develop a novel technology for large-scale labeling and modulating activity of neurons associated with particular physiological processes and behaviors. This technology will be different from all other technologies that are currently used in biological research because it is based on the novel idea that particular neuronal assembles can be targeted by driving the expression of a reporter protein specifically in the neurons that are both active and exposed to the near-infrared light. We will produce vectors in which expression of a reporter protein (such as fluorescent protein mCherry) is controlled by both an activity-sensitive promoter and bacterial phytochrome-1 (BphP1) photoreceptor. Therefore, this protein will not be expressed in neurons that are either active but not exposed to the near-infrared light or exposed to the near-infrared light but not active. Expression of the protein will occur only if the neuron is both active and exposed to the near- infrared light. Because the light can be turned on and off, our proposed tool will allow precise temporal correspondence between the light exposure and the behavior. Such correspondence is critical for labeling neurons during the behaviors that are not sustained in time. By visualizing the pattern of the mCherry expression, we will be able to identify the neurons that are active during specific behaviors (e.g., exploring new object, grooming) or physiological states (e.g., rapid eye movement sleep). We plan to apply this technology in sleep research studies, but it can be also applied in a wide range of neurobiology studies.

Sleep-wake disruptions and cognitive impairments are prevalent and disabling features of Alzheimer's disease (AD). AD patients exhibit profound sleep disturbances including disruption of non-rapid eye movement (NREM) sleep. A major restorative feature of NREM sleep, which is also associated with proper cognitive functioning, is slow-wave activity (SWA). Recent findings suggest a causal relationship between impaired generation of SWA during sleep and AD pathogenesis including extracellular accumulation of the amyloid-? (A?) peptide and neuronal dysfunction. While evidence indicates that cortical-thalamic loops regulate SWA, the exact cellular and molecular mechanisms for impaired SWA in AD are unknown. Thus, a need exists to characterize the cells and molecular mechanisms responsible for SWA generation to reduce the impairments in SWA and pathogenesis of AD. We propose studies that will elucidate the sleep state related mechanisms by which SWA protects against AD. Studies using AD animal models suggest that inhibitory neurotransmission is impaired during periods of SWA. The overall objective of this proposal is to identify and stimulate specific SWA modulating interneuronals to determine which cells restore SWA and mitigate AD-related pathology using an established AD mouse model. Herein, we propose to employ optogenetics and chemogenetics to control neuronal circuits aimed to restore SWA and slow AD progression. Thus, our findings will determine the cellular and molecular relationships between sleep and AD, with the targeting of interneurons during specific periods of sleep as a novel therapeutic approach.