Task Progress:
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APPROACH My project leveraged a novel translational analog in the wild red squirrel: it is a freely behaving, abundant, tractable rodent model. We recently characterized sleep-like patterns in red squirrels using accelerometry suggesting that high behavioral demands lead to more efficient sleep (unpublished). If this particular behavioral regime was better understood, it may offer a broader perspective of how sleep interplays with demanding environments and high-performing individuals.
RESULTS
My project aimed to characterize red squirrel sleep patterns in the wild; however, it was significantly impacted by border shutdowns at our primary field site in Canada due to COVID-19. I overcame those challenges by creating a local field site near the University of Michigan at Saginaw Forest, where I tagged, tracked, and trapped a local population of red squirrels. Although I did not collect a significant amount of field data, I was successful in a limited number of wild and lab-based neural recordings. The toolset I developed measured neural, cardiac, and accelerometry data. I demonstrated how such a device can be deployed in free-living conditions or used in a closed-loop paradigm to enhance SWS (see Gaidica & Dantzer, 2022). I also presented first-of-its-kind data that characterized red squirrel SWS periodicity, suggesting robust ~20-minute cycles. The significance of such work is threefold: (1) I refined a translational field model including new surgical methods for future use, (2) I developed a novel implantable with embedded technology that can apply to human conditions, and (3) I published convincing pilot data suggesting red squirrels are an ethologically relevant animal model who exhibits robust SWS cycles with behavioral patterns (e.g., sleep-wake) more like humans than rats or mice.
YEARS 1-2 IMPACT
In sum, my research worked toward a new approach and methods to reveal the foundations of performance and resilience.
YEAR 3 RESEARCH PLAN
The hindlimb unloading (HU) model has been used to simulate microgravity—and more broadly, disuse—for over 40 years. Since the National Aeronautics and Space Administration (NASA) confirmed similar tissue fluid shifts and musculoskeletal responses in rodents compared to subjects in the weightlessness of space, HU has become an important model to study other physiologic factors relating to metabolic, endocrine, and adrenal function. However, the current (and common) HU apparatus is statically calibrated, such that the hindlimbs are unloaded through tail suspension using a constant force. This weight is typically equal to a 30° incline (i.e., head-tilt down) which matches the cephalic fluid shift and pressures experienced in zero-G while providing normal weight-bearing on the forelimbs and unloading the lumbar vertebrae but not the cervical vertebrae. Since tilt-angle and weight-unloaded are co-linear, the notion that a standard unloading protocol could be implemented dynamically is possible if the unloaded weight could be monitored.
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