Project Summary/Abstract In the United States millions of people sustain a traumatic brain injury (TBI) each year carrying individualhealthcare and societal costs greater than $45 billion annually. Mild TBI (mTBI) accounts for more than 75% ofall TBIs with many individuals sustaining more than one. mTBI patients report post-concussion syndrome (PCS)symptoms that include sleep disorders (insomnia daytime sleepiness) somatic symptoms (dizziness headacheblurred vision) cognitive complaints (memory executive function) and emotional problems (anxiety depressionirritability disinhibition). For many PCS is transient and still 10-25% report persistent PCS symptoms. Theenigmatic PCS symptom presentation and persistence after mTBI urges investigation into dynamic responsesin the brain that tie acute neurophysiology to behavioral function. The investigative team has refined in vivoimaging methods of miniaturized microscopes (miniscopes) to evaluate cerebral blood flow (CBF) and bloodbrain barrier (BBB) permeability in the unrestrained behaving mouse. New preliminary data leverage theminiscope headcap to induce impact acceleration (weight drop) closed head injury. The data driving this proposalshow immediate accumulation of fluorescent dextrans in the parenchyma within the field of view. The strengthof this approach eliminates anesthesia during long-duration imaging permits naturalistic behavior without headrestraint and locks into a baseplate for repeated imaging of single channel wide-field fluorescence. For the firsttime the cumulative effects of TBI on neurophysiology (CBF BBB permeability sleep) can be regressed towardneurobehavioral impairments. The present proposal tests the hypothesis that the cumulative effects ofmTBI on CBF and BBB permeability promote post-traumatic sleep and predict neurological impairments.Male and female mice are prepared for miniscope imaging through a cranial window and attached baseplate.The baseplate headcap substitutes for a helmet in closed-head impact acceleration TBI. With a 15 sec transitionminiscopes visualize CBF and BBB permeability with intraperitoneal dextrans (40-2000 kDa) in vasculature andparenchyma respectively. The cumulative effects of mTBI are assessed with impacts delivered twice daily dailyor every other day for a week. Aim 1 monitors the cumulative effects of mTBI with varying temporal spacing onCBF concurrent with post-traumatic sleep and subacute behavioral performance. Aim 2 quantifies the extent ofdextran extravasation with post-traumatic sleep and subacute neurological performance. Neurological outcomesinclude anxiety (open field) spatial memory (novel object location) and somatosensory pain (mechanicalhyperalgesia). Twice daily injuries likely show temporal summation of CBF BBB permeability and sleep effectswhich are recovered with longer recovery times between injuries. The integration of miniscope imaging andclosed head injury can propel future studies on physiological perturbations and clinical management of TBI.