SignificanceStroke is the leading cause of chronic disability in the United States. How stroke size affects post-stroke repair and recovery is poorly understood.AimWe aim to investigate the effects of stroke size on early repair patterns and determine how early changes in neuronal circuits and networks predict functional outcomes after stroke.ApproachWe used wide-field optical imaging, photothrombosis, and the cylinder-rearing assay to examine changes in neuronal circuit and network activity in the context of functional recovery after stroke.ResultsLarger strokes ablating S1FP caused diffuse and widespread forepaw stimulus-evoked cortical activation, including contralesional regions evolving within 4 weeks post-stroke; smaller strokes resulted in more focused ipsilesional activation. Larger strokes decreased neuronal fidelity and bilateral coherence during stimulation of either the affected or unaffected forepaw within this 4-week period. Mice in the larger lesion group demonstrated hyperconnectivity within the contralesional hemisphere at the resting state. Greater degrees of remapping diffusivity, neuronal fidelity degradation, and hyperconnectivity predicted worse 8-week recovery after statistically controlling for the effect of infarct size.ConclusionsThese results suggest that diffuse patterns of remapping, and desynchronization and hyperconnectivity of cortical networks, evolving early after stroke may reflect maladaptive plasticity, predicting poor long-term functional recovery.
Recent developments in optogenetics allow for quick and minimally invasive methods of mapping functional brain circuits in animal models. DeepLabCut (DLC), a toolbox for markerless pose estimation, offers the ability to track features in three-dimensions. We demonstrate a hybrid method utilizing DLC and light-based, optogenetic motor mapping to concurrently localize motor representations of multiple limbs in mice. Our results suggest that behaviorally-relevant, motor movements involving multiple limbs reside in overlapping cortical representations of each limb. Applications of this technique include characterizing recovery of finer, articulated movements of affected limbs after stroke, or mapping brain network activity during naturalistic behavior.
Psychedelics, which effects appear to be mediated via seratonin-2A receptors(5-HT2AR), are a promising therapeutic. Recent human studies have shown drastic changes in functional network organization but may be confounded due to Serotonin’s vasoconstriction effects. We aimed to determine if 5-HT2AR agonism (via Lisuride), alone, differentially affect cortical neuronal and hemodynamic activity, functional connectivity (FC), and neurovascular coupling (NVC). Eight Thy1-jRGECO1a mice were imaged for 60-minutes under awake, resting-state conditions using wide-field optical imaging. Lisuride significantly reduced neuronal and hemodynamic bilateral FC and activity in a region- and frequency-band-specific manner. Furthermore, delayed NVC was observed. Results suggest 5-HT2AR agonism alters hemodynamic activity, FC and NVC. Future work will evaluate acute effects of commonly used psychedelics on brain function and differentiate hallucinatory vs non-hallucinatory 5-HT2A receptor activation.
Understanding how different central nervous system diseases affect different components of neurovascular coupling will allow for linking changes in neural or metabolic dysfunction to changes in hemodynamic signaling upon which blood-based imaging methods rely. We developed a dual fluorophore imaging system for simultaneous, high-speed mapping of neural, metabolic, and hemodynamic activity. Proof-of-concept measurements of spontaneous and stimulus-evoked dynamics are presented in awake and anesthetized mice. This flexible hardware platform allows for integrating optogenetic stimulation for all optical neural circuit interrogation and readout, and for examining the interaction between multiple cell populations.
Recent developments in optogenetics allow for quick and minimally invasive methods of mapping functional brain circuits in animal models. DeepLabCut (DLC), a toolbox for markerless pose estimation, offers the ability to track features in 3-dimensions. We demonstrate a hybrid method utilizing DLC and light-based, optogenetic motor mapping to concurrently localize motor representations of multiple limbs in mice. Our results suggest that behaviorally-relevant, motor movements involving multiple limbs reside in overlapping cortical representations of each limb. Applications of this technique include characterizing recovery of finer, articulated movements of affected limbs after stroke, or mapping brain network activity during naturalistic behavior.
We examine the correlation of non-invasive, frequency-domain diffuse optical spectroscopy (FD-DOS) and diffuse correlation spectroscopy (DCS) measurements of cerebral tissue oxygen extraction fraction (OEF) and relative cerebral blood flow (rCBF) with invasive cerebral microdialysis measurement of the cerebral lactate-pyruvate ratio (LPR), a biomarker of metabolic stress, during extracorporeal membrane oxygenation (ECMO) in a pediatric swine model of ECMO assisted cardiopulmonary resuscitation (n=15). During 22-24 hours of ECMO, non-invasive FD-DOS/DCS neuromonitoring of OEF and rCBF demonstrated significant correlations with cerebral LPR. Non-invasive detection of critical neurometabolic stress at the bedside may facilitate brain-targeted ECMO management after cardiac arrest.
Mild hypothermic cardiopulmonary bypass (CPB) is used during neonatal cardiac surgery. To elucidate potential risk factors for brain injury, diffuse optical spectroscopy, diffuse correlation spectroscopy, and cerebral microdialysis techniques were employed to monitor cerebral hemodynamics during mild hypothermic CPB in a swine model. Optical metrics were further compared with microdialysis metrics. Stable microdialysis metabolite levels, a significant decrease in CMRO2, and trending (but not significant) decreases in CBF and increases in OEF were observed. This suggests that the optical metrics may be more sensitive to neurologic injury during CPB than microdialysis.
Extracorporeal membrane oxygenation (ECMO) is an important therapy for critically ill children but survivors have neurodevelopmental impairments. Cerebral inflammatory response resulting in brain edema is observed on ECMO. This pathologic response may adversely impact the quantitative accuracy of diffuse optical spectroscopy (DOS) neuromonitoring (including commercial NIRS) which commonly assumes a 75% water fraction. Using fresh brain tissue desiccation, we directly quantified the severity of cerebral edema in pediatric swine following cardiac arrest, CPR and 22-24 hours of ECMO therapy. The fractional error in DOS quantification of cerebral hemodynamics from assuming 75% water fraction was determined to be <5%.
Recent developments in optogenetics allow for quick and minimally-invasive methods of studying functional brain organization in animal models. DeepLabCut (DLC), a toolbox for markerless pose estimation, offers the ability to track user-defined features in 3-dimensions with human level accuracy. We demonstrate a hybrid method utilizing DLC and optogenetic motor mapping to localize the movements of multiple modalities to the mouse cortex. We outline a pipeline to map and characterize multiple motor representations in anesthetized and awake mice. Furthermore, we identify behaviorally-relevant motor movements of multiple limbs reside in overlapping cortical representations of the respective limbs.
Evaluation of the brain’s resting-state is an important window into neuronal function, connectivity, and health. Resting-state brain activity is reflected via neurovascular coupling in low frequency (0.01-0.1 Hz) hemodynamics, and low frequency power (LFP) can be a proxy for regional neuronal activity. In this exploratory study, we measured LFP in cerebral blood flow using diffuse correlation spectroscopy (LFP-DCS) during the course of an asphyxial cardiac arrest model in pediatric swine. The data demonstrate that LFP-DCS has distinct temporal information to blood flow index and may provide an additional biomarker to predict successful recovery after neurologic insults.
Accurate light dosimery is critical to ensure consistent outcome for pleural photodynamic therapy (pPDT). Ellipsoid shaped cavities with different sizes surrounded by turbid medium are used to simulate the intracavity lung geometry. An isotropic light source is introduced and surrounded by turbid media. Direct measurements of light fluence rate were compared to Monte Carlo simulated values on the surface of the cavities for various optical properties. The primary component of the light was determined by measurements performed in air in the same geometry. The scattered component was found by submerging the air-filled cavity in scattering media (Intralipid) and absorbent media (ink). The light source was located centrally with the azimuthal angle, but placed in two locations (vertically centered and 2 cm below the center) for measurements. Light fluence rate was measured using isotropic detectors placed at various angles on the ellipsoid surface. The measurements and simulations show that the scattered dose is uniform along the surface of the intracavity ellipsoid geometries in turbid media. One can express the light fluence rate empirically as φ =4S/As*Rd/(1- Rd), where Rd is the diffuse reflectance, As is the surface area, and S is the source power. The measurements agree with this empirical formula to within an uncertainty of 10% for the range of optical properties studied. GPU voxel-based Monte-Carlo simulation is performed to compare with measured results. This empirical formula can be applied to arbitrary geometries, such as the pleural or intraperitoneal cavity.
PDT efficacy depends on the concentration of photosensitizer, oxygen, and light delivery in patient tissues. In this study, we measure the in-vivo distribution of important dosimetric parameters, namely the tissue optical properties (absorption μa (λ) and scattering μs ’ (λ) coefficients), photofrin concentration (cphotofrin), blood oxygen saturation (%StO2), and total hemoglobin concentration (THC), before and after PDT. We characterize the inter- and intra-patient heterogeneity of these quantities and explore how these properties change as a result of PDT treatment. The result suggests the need for real-time dosimetry during PDT to optimize the treatment condition depending on the optical and physiological properties.
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