Specific Aim 1: Establish Psychiatric sensitivity of explore/exploit decision making in TBI patients. It is hypothesized that TBI patients with impulsivity will demonstrate overly-exploratory responses, and patients with compulsivity will demonstrate overly-exploratory responses, relative to the Markov Decision Process (MDP) models.
Specific Aim 2: Elucidate neuropathologies underlying maladaptive explore/exploit decision making in TBI. It is hypothesized that s and FMRI data will converge to suggest that AMY-VS-PFC neuropathologies underlie maladaptive decision making associated neuropsychiatric symptoms in TBI
Specific Aim 3: Generate models to support rational brain stimulation protocol design. Data from Aim 2 will be used to constrain computational models to develop high –definition transcranial direct current stimulation (HD-tDCS) protocols to maximize current flow to anatomical targets. The optimized protocol will then be evaluated as a method for modulating explore/exploit decision making in healthy controls and TBI patients in the future CBRR-affiliated project.
Specific Aim 1: Is the occurrence of cortical spreading depolarization (CSD) or specific types of CSD associated with worsening neurologic or radiographic outcomes after acute brain injury?
Specific Aim 2: Can CSD be detected using non-invasive or minimally invasive techniques?
Specific Aim 3: What is the effect of other systemic and local variables on the occurrence and type of CSD?
Specific Aim 4: What is the most accurate method to define and score CSD?
Hypothesis: Spreading depolarizations (SD)s are a key underlying mechanism of the acute behavior and period of vulnerability that follow a concussion.
Specific Aim 1: Testing the hypothesis that spreading depolarization (SD) contributes to acute post-hit behavior. Adolescent concussions are of serious concern and are confounded by the developing brain. Concussions (or mild traumatic brain injuries) are often described by the acute symptoms of neurological dysfunction that include headaches, vertigo, nausea, disorientation and/or cognitive deficits but does not require the loss of consciousness. Current guidelines for the diagnosis and recovery of a concussion are based on these transient symptoms. Typically the symptoms resolve within a few hours or days, but ~20-30% of individuals have symptoms that can persist for weeks or months. Adolescents typically take longer to recover. However, the underlying mechanisms of the acute symptoms and vulnerability of a second hit are poorly understood. This is a critical gap to fill because there is a clear lack of effective treatments for concussions during the acute phase to promote brain recovery and repair.
Specific Aim 2: Testing the hypothesis that the acute injury phase is associated with a period of vulnerability to a second hit. Repeated concussions have been associated with persistent behavioral alterations, severe cognitive deficits, and have been linked to brain pathology that is associated with chronic traumatic encephalopathy (CTE). Post-injury symptoms are often worse and persist longer in individuals with a history of a prior concussion. Alterations in cerebral blood flow (CBF) and metabolic dysfunction have long been associated with concussions. It is clinically assumed that this period of disrupted CBF and metabolic dysfunction is associated with a heightened vulnerability to a second hit.
Long-term goal: Helping develop strategies and treatments to improve brain recovery following mild brain injuries. The objective is to identify the underlying mechanism(s) of the neurological dysfunction and the period of vulnerability that follow an injury in adolescent mice. We and others have recently provided exciting initial evidence that large slowly propagating waves of cortical depolarizations are initiated by a closed skull injury and are responsible for a prolonged reduction in CBF (~90 min). The role of SDs in concussion-like symptoms and vulnerability to a second hit are currently unknown. The rationale for the proposed studies is that knowledge gained here will provide a basis for new approaches to target the known consequences of SDs to promote brain recovery and limit long-term sequelae of concussions which are very common and an often severely debilitating type of brain injury.
A Rat Model of Responsive Neural Stimulation for Epilepsy
Specific Aim 1: I will determine whether stimulating REM-promoting brain regions is effective in reducing seizure severity in an evoked model of epilepsy. Recent studies have identified a network of brain regions wherein experimental stimulation causes rapid transition into REM sleep, if the subject is in slow-wave sleep16,17. I will target one of these brain regions, the cholinergic neurons of the pedunculopontine nucleus (PPT) in the rat kindling model, to test my working hypothesis that seizure thresholds are higher when cholinergic signaling from the PPT to the thalamus induces cortical asynchrony.
Specific Aim 2: I will determine whether pre-seizure stimulation of the PPT can reduce seizure severity in an epilepsy
model associated with spontaneous seizures. Real-world seizures are often difficult to predict and, therefore, a chronic model is needed to motivate the translatability of this seizure target. The seizure forecasting community has made great strides in the last five years in predicting seizures and seizure prone states18,19. I will apply the state-of-the art in seizure forecasting to the kainic model of chronic focal epilepsy to test my hypothesis that PPT stimulation can prevent predicted seizures.
Long Term Goal- is to improve the clinical outcome for epilepsy patients receiving neural stimulation by elucidating a mechanistic understanding of why such treatments work. Inspired by the observation that generalized seizures are nearly absent during rapid-eye movement (REM) sleep13,14, my objective here is to further our understanding of how REMpromoting brain regions affect seizure propagation. In my prior work, I found that cortical neurons are less responsive to hippocampal output when inputs arrive upon a background of cortical asynchrony15. During REM, much of the brain operates in this asynchronous regime which potentially fosters the anti-convulsant state. My central hypothesis is that seizures can be prevented by experimentally modulating REM-promoting brain regions. By developing a circuit-level understanding for why neural stimulation prevents seizure spread, this work will pave the way for the development of
novel treatments for refractory epilepsy wherein generation of cortical asynchrony can be tested as a biomarker for anticonvulsant stimulation protocols.
Specific Aims: Aim 1: Characterize the neuronal dendrite morphology and spine density in naïve rats within the prefrontal cortex. The overarching goal is to assess the changes that occur within the prefrontal cortex following PAE+PI. Therefore, the characterization of normal development must occur. At postnatal day 28 (P28) and P100, naïve prefrontal cortex will be dissected, stained with FD Rapid Golgi Stain Kit, and utilizing a Leica microscope, high magnification and z-stack images will be obtained, followed by analysis with IMARIS software. Three-dimensional reconstructions will be performed with IMARIS Filament Tracer, and total process length, number of terminal points and number of branch points will be calculated. Additionally, an automated Sholl analysis will be performed on each digitized cell with the IMARIS software. We hypothesize that the developing prefrontal cortex at P28 will have a dense and complex structure, due to the period of dendritic arborization, glial proliferation and synapse formation that occurs during maturation. At P100, we hypothesize that naïve rats will have decreased spine density following pruning and maturation.
Aim 2: Test that neuronal dendrite morphology and spine density will be altered in the prefrontal cortex following PAE+PI compared to either PAE or PI alone. The prefrontal cortex is extremely plastic, and exposure to various drugs can result in synaptic changes. The impact on dendritic length and complexity as well as spine density following PAE+PI is not known. While previous studies have shown less mature cortical tissue in preterm infant compared to term infants, we hypothesize that at P100, PAE and PI will individually result in decreased dendritic length and complexity as well as decreased spine density. When PAE+PI are combined, we expect a unique signature to emerge in which the prefrontal cortex has significantly delayed maturation. The parameters that will be collected include total process length, number of terminal points, and number of branch points. An automated Sholl analysis will be performed with utilization of IMARIS software.
Together, these studies will examine the structural, diffusion and functional brain abnormalities through a critical period of neurodevelopment and will provide vital translational clues to the injury specific to PAE+PI and will facilitate diagnostic clinical biomarkers to aid in the development of therapies and treatments within this vulnerable patient population.
Specific Aim 1: Measure treatment-induced improvements in language abilities.
We postulate that participants will demonstrate improved naming and language use (i.e., narrative abilities, confidence), with greater and longer lasting gains following adjuvant brain stimulation.
Specific Aim 2: Measure connectivity and balance pre- and post- aphasia treatment.
Our working hypothesis is that increased intra- and inter-hemispheric connectivity (measured with resting-state fMRI) and more normalized interhemispheric balance (measured with quantitative EEG) will be observed following aphasia treatment, with greater and longer-lasting changes following adjuvant brain stimulation.
Specific Aim 3: Examine relationship between language outcomes and changes in brain dynamics (e.g., connectivity and balance).
We hypothesize that greater gains in language abilities will be related to greater adaptive changes in brain dynamics.
Specific Aim 1: What is the time course and magnitude of functional recovery following intracortical transplantation of hPSNs in a mouse model of focal cerebral ischemia? We will establish the rate and time course of behavioral recovery following hPSNS transplantations in a focal photothrombotic model of ischemic injury. hPSNs will be transplanted one week after ischemic injury and behavioral and anatomic recovery will be assessed using multiple motor, sensory, and immunochemical tests.
Specific Aim 2: Is behavioral recovery enhanced by increased activation of transplanted hPSNs? Ontogenetic stimulation of hPSNs via hannelrhodopsin-2 will be used to test whether the rate or magnitu njury. hPSNs will be transplanted one week after ischemic injury and behavioral and anatomic recovery will be assessed using multiple motor, sensory, and immunochemical tests.
Specific Aim 2: Is behavioral recovery enhanced by increased activation of transplanted hPSNs? Ontogenetic stimulation of hPSNs via hannelrhodopsin-2 will be used to test whether the rate or magnitude of behavioral recovery is enhanced by chronic intermittent depolarization of transplanted cells.
Specific Aim 3: Do transplanted hPSNs receive physiologically relevant afferent innervation from host? Using in-vivo multi-electrode recording of transplanted neurons during peripheral sensory stimulation we will determine whether hPSNs display altered spiking behavior during simulation that would normally activate endogenous cortical circuits.
Specific Aim 1: To evaluate the time and polarity-dependent effectiveness of tDCS in improving neurologic recovery after traumatic brain injury. These experiments will test the hypothesis that stimulation beginning at one and three weeks following TBI improves motor and cognitive function. Using an established mouse TBI model (controlled cortical impact), we will assess effects of repetitive tDCS stimulation of different polarity, applied beginning at either one week or three weeks after TBI on behavioral outcomes at two and three months post-injury.
Specific Aim 2: To determine whether tDCS enhances migration and differentiation of endogenous neural stem cells after traumatic brain injury. These experiments will test the hypothesis that repetitive tDCS modulates recruitment of endogenous NSC to areas of focal injury. Mice will be sacrificed at multiple time points post stimulation, and numbers and phenotypes of neural stem-derived cells will be identified by stereological analysis in brain sections.
Specific Aim 3: To determine whether tDCS induces long-lasting modulation of regional and microvascular flow during recovery from traumatic brain injury. These experiments will test the hypothesis that repetitive tDCS can modulate neurovascular coupling in peri-infarct area. Laser speckle contrast imaging and two-photon imaging will be used to identify regional and microvascular flow changes, respectively, to assess the effect of stimulation during the recovery period.
Specific Aim 1: To investigate whether functional EEG abnormalities (theta band phase synchrony) underlie common disturbances of cognitive control during the semi-acute injury stage.
Hypothesis 1: Theta band phase synchrony during cognitive control will be diminished during the semi-acute stage of mmTBI, and will be correlated with dysfunctional performance across multiple measures of cognitive control (e.g. accuracy and response times)
Hypothesis 2: Functional EEG Abnormalities will be related to the degree of white matter lesions as assessed by DTI, linking white matter abnormalities with functional consequences.
Specific Aim 2: To investigate whether functional EEG activities predict recovery post-injury.
Hypothesis 1: A restoration in theta band phase synchrony during cognitive control will be predictive of better cognitive control recovery at 4 months post-injury, providing a biomarker of recovery.
Hypothesis 2: The functional measure of theta band phase synchrony will predict the extent of recovery in cognitive control over and above the predictive power of more traditional measures of structural pathology.
Hypothesis 3: Novel pattern classification techniques bases on these predictive measures will exhibit high sensitivity for classifying patients relative to controls and for defining the independent contribution of separate prognostic measures (structural, functional, behavioral) for predicting recovery.
Specific Aim 1: tDCS for executive dysfunction in mmTBI. Experiments in this aim will test the hypothesis that in patients with mmTBI, left prefrontal anodal tDCS concurrent with cognitive training for ten consecutive weekdays will result in significantly more improvement in executive function compared to sham stimulation. Patients with cognitive complaints 3 months to 2 years after mmTBI will be recruited from local emergency departments and brain injury clinics.
Aim 1.1: tDCS will be paired with computer-based cognitive training tasks of response inhibition, set shifting and working memory. Executive function will be measured with the NIH Examiner batter before, immediately after, and one month after stimulations.
Aim 1.2: Persistence of post-traumatic symptom reduction and quality of life improvement will be assessed with Common Data Elements instruments via telephone interview at six months and one year.
Aim 1.3: Clinical predictor of tDCS response including injury severity, premorbid intelligence and post-traumatic symptom burden will be determined with linear mixed-models analysis.
Specific Aim 2: tDCS for depressive symptoms in mmTBI. Experiments in this aim will test hypothesis that left prefrontal anodal tDCS in patients with mmTBI will significantly reduce depressive symptoms compared to sham stimulation.
Aim 2.1: Patients will be assessed for symptoms of depression via self-report instruments and clinician-administered scales from NIH common Data Elements before, immediately after, and one month after the stimulation protocol.
Aim 2.2: Persistence of antidepressant benefit will be assessed via telephone interview at 6 months and one year.
Aim 2.3: Clinical predictor of tDCS response such as injury severity, premorbid intelligence, and symptom burden will be determined. Accomplishment of these Aims will have a tremendous clinical impact on the treatment of chronic and debilitating TBI-related symptoms, and will establish tDCS as an effective and safe tool to be used for the important clinical problem. Future studies would be able to refine and expand this technique to different TBI populations, as well as other similar neuropsychiatric disorders.
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