Music often evokes strong emotions, such as excitement, joy, and nostalgia. These emotions can be highly pleasurable and accompanied by increased physiological arousal. Pleasure-inducing music activates a network of brain regions including the medial prefrontal cortex (mPFC), striatum, and amygdala. In Experiment 1, I explore the neural structures critical for music-evoked pleasure. I hypothesize that individuals with damage to brain regions involved in emotional responses to music (e.g., mPFC, striatum, amygdala) will show a decrease in their pleasurable responses to music after brain injury. Patients from the Iowa Neurological Patient Registry completed questionnaires that assessed current emotional responses to music and changes in emotional responses to music after brain injury. The results provided partial support for the hypothesis, and the most striking loss of musical pleasure (referred to as "music anhedonia") occurred in a patient with damage to the striatum. However, musical pleasure appears to be relatively resistant to brain damage, as music anhedonia was only observed in a few individuals with varying regions of brain damage. Along with strong emotions, music often triggers distant memories. However, the mechanism underlying music-evoked autobiographical memories (MEAMs) has not yet been investigated. Here, I predict that emotion is a central aspect underlying MEAMs. In Experiment 2a, I tested the hypothesis that MEAMs are more emotional and vivid than autobiographical memories evoked by pictures of famous faces. Neurologically normal, healthy adults viewed pictures of famous faces and listened to music while electrodermal activity was recorded. After each stimulus, participants described any memories that were evoked. Supporting my prediction, I found that MEAMs were significantly more vivid than face-evoked memories. In addition, music that evoked memories was accompanied by increased skin conductance responses compared to music that did not evoke memories. In Experiment 2b, I used a neuropsychological approach to test the prediction that neural regions underlying music-evoked emotions are also critical for MEAMs. I tested the hypothesis that individuals with damage to brain regions important for music-evoked emotions (mPFC, amygdala, and striatum) would have impaired MEAMs. Individuals with damage to these regions, brain-damaged comparison subjects (with damage to other regions) and neurologically normal comparison subjects completed the same task as in Experiment 2a. The results indicated partial support for the hypothesis, showing that individuals with mPFC, but not striatal, damage had slightly decreased MEAM vividness. Additionally, individuals with damage to the striatum and mPFC showed a disconnect between emotional ratings and physiological responsiveness. These findings provide important implications for the use of music in therapeutic settings. Since musical reward is predominantly preserved in individuals with brain damage, music can be used to improve mood and affect in clinical populations. In addition, these findings support the use of music as a memory aid in patients with dementia, since music-evoked memories are shown to be more vivid than memories evoked by other cues. Together, these experiments provide partial support for the hypothesis that neural regions important for emotion are also critical for MEAMs, indicating that emotion may be an important aspect underlying music-evoked autobiographical memories.

Huntington disease (HD) is a neurodegenerative disorder caused by expansion of a polyglutamine tract within the huntingtin (HTT) protein, forming mutant HTT (mtHTT). HD patients suffer from psychiatric, behavioral, cognitive, and motor abnormalities, with death typically occurring 15-20 years after symptom onset. Currently, there are no treatments able to slow disease progression or delay onset. HD is a disease of aging. Despite the mtHTT protein being produced throughout life, symptoms do not typically appear until adulthood. Furthermore, many cellular effects of normal aging are also seen in HD, including altered intercellular communication and loss of proteostasis. Recently, our lab found evidence that inducing age-like changes uncovers HD phenotypes, which contribute to pathogenesis in neurons. This suggests that reversing the aging process could counteract phenotypic development of HD. Thus, anti-aging could be effective for treatment of HD. Our lab conducted an anti-aging preclinical trial in which aged HD mice were systematically treated with plasma from young mice, known as young blood treatment. The goal of this trial was to investigate if treatment could successfully delay disease onset or progression. The aim of my project is to determine if treatment affected biological age and HD by analyzing the levels of protein markers in these brains. Preliminary data validates that aging markers decrease with age and shows that young blood treatment has varying success at rejuvenating protein levels. This work contributes to a better understanding of the relationship between biological age and HD pathogenesis.

Huntington Disease (HD) is an autosomal dominant neurodegenerative disease caused by an expansion of a CAG trinucleotide repeat tract in the huntingtin (HTT) gene. This CAG tract expansion causes production of mutant HTT (mtHTT) protein, which misfolds and forms inclusions in the brain that accumulate with age. Misfolded mtHTT aggregates have been linked with increased cell death in neuron cell culture, leading to speculation that mtHTT aggregates cause cell death. However, there are mouse lines that have robust mtHTT inclusion deposition, but no HD-like signs or neurodegeneration. Furthermore, neuronal HD cultured cells with inclusions were found to be less likely to die compared to those with no inclusions. These findings indicate that mtHTT inclusions may play a neuroprotective role in HD by sequestering a toxic soluble form. Cell cultures show increased levels of stress response proteins when oligomeric mtHTT levels are elevated, indicating that oligomers may be the toxic species driving disease pathogenesis. Our lab has recently shown that inducing age-related changes in HD neurons induces oligomer formation. This finding suggests that there is a potential link between biological age and mtHTT misfolding. I am investigating this relationship by assessing mtHTT aggregation in the brains of HD model mice that have undergone anti-aging therapy using EM48, an antibody that recognizes misfolded mtHTT. The results of this study may provide further insight into the relationship between biological age and accumulation of misfolded mtHTT protein. If we find a relationship between biological age and mtHTT misfolding that can be therapeutically modulated, this may provide new insight into the ‘toxic species’ of mtHTT and would have implications for strategies aimed at reducing its levels. No effects of ‘young blood’ (YB) therapy were observed in this study. But due to limitations in the study, a conclusion on the effect of YB treatment will require further work, including optimization of image processing and processing of a greater number of animals.

<p>The striatum is part of a neural feedback network that modifies the functioning of the cerebral cortex. The importance of the striatum is underlined by the clinical consequences of striatal dysfunction: disordered signaling in the striatum gives rise to the clinical syndrome of Parkinson's disease, while degeneration of striatal output neurons produces the clinical manifestations of Huntington's disease. The striatum is a complex structure comprised of two major populations of neurons: the spiny projection neurons that carry the striatal output to other nuclei in the basal ganglia; and several subtypes of aspiny cells that project locally within the striatum to modify striatal output. The two major inputs to the striatum are the glutamatergic pathway from the cerebral cortex and the dopaminergic pathway from the substantia nigra. The goal of my research is to explore the nature and functional significance of dopamine-glutamate signaling and its role in the striatum and basal ganglia. My first series of studies in vivo demonstrated that altering dopaminergic tone in the striatum by D2-dopamine receptor blockade or by 6-hydroxy-dopamine lesion of the nigrostriatal dopamine projection in the rat could modify the pathological, neurochemical and behavioural consequences of glutamate-receptor-mediated-stimulation. In order to investigate the details of this interaction, I developed an in vitro tissue culture system. I showed initially that the growth of striatal neurons in serum free culture parallels their in vivo development. I then went on to use this in vitro system to demonstrate the differential effects of selective glutamate receptor agonists on transmitter release from subpopulations of the two major classes of striatal neurons: (i) those in which somatostatin and neuropeptide Y are colocalised with nitric oxide and (ii) the substance P-containing spiny projection neurons. This series of studies demonstrated that substance P release was selectively stimulated through the N-methyl-D-aspartate (NMDA) subtype of glutamate receptor while somatostatin and neuropeptide Y release were selectively provoked by stimulation of the kainate receptor. Stimulation of the metabotropic glutamate receptor had little effect on the release of any of the three peptides. My final series of experiments examined the differential effects of selective dopamine receptor stimulation on glutamate-receptor-induced release of substance P, somatostatin and neuropeptide Y. The D1 agonist SKF 38393, and to a significantly lesser extent the D2 agonist quinpirole, attenuated glutamatergic release of substance P from the spiny neurons. In contrast, the D2 agonist quinpirole potentiated the release of neuropeptide Y and somatostatin from aspiny neurons. The D1 agonist SKF 38393 attenuated glutamate receptor stimulated release of neuropeptide Y, without significantly affecting the release of somatostatin from the same cultures. This latter result indicates that dopamine can differentially regulate transmitter release not only from separate populations of striatal neurons but also differentially control release of transmitter that are colocalised within a single population of neurons. To my knowledge these studies are the first to demonstrate this differential regulation in the striatum, and implies that the delicate balance required for both normal cognition and movement may be intimately related to the balance of signaling between the intrinsic (somatostatin-neuropeptide Y-containing) and extrinsic (substance P-containing) neuronal populations in the striatum.</p> / Doctor of Philosophy (PhD)

Abstract Background: Cusk-eels from the subfamily Neobythiitinae are one of the major groups of sound-producing fishes on the continental slope. Sounds have never been recorded from a member of this subfamily, and sonic anatomy is considered a proxy for sound production. As the first part of a study on the effects of depth on sonic anatomy, we examined three relatively shallow species from the upper continental slope. Methods: Three species (Hoplobrotula armata, Neobythites longipes and Neobythites unimaculatus) were examined for sonic anatomy (skeleton, swimbladder and sonic muscles), and sonic and epaxial muscle fibers were measured for diameter. Regressions of dimensions and weights of sonic muscles and swimbladders against fish total length and weight were compared to determine sexual dimorphism and relative development between species. Results: Four pairs of sonic muscles (two medial and two lateral) originate on the skull and insert on the medial swimbladder or on modified epineural ribs that attach to the lateral swimbladder. The medial and medial intermediate muscles are generally larger in males than females and are made of relatively small fibers (ca 10 um in diameter), and lateral muscles are generally larger in females and consist of larger fibers as in epaxial muscles. Medial muscles are considerably larger in Hoplobrotula armata than in the Neobythites species. Conclusion: Neobythitines from the upper slope have relatively well-developed sexually-dimorphic sonic systems, suggesting that males produce advertisement calls for courtship. There are major quantitative differences between species. We suggest that sound production involves tonic contraction of the large-fibered lateral muscle pair and oscillatory contractions of the smaller medial fibers setting the swimbladder into vibration. Hoplobrotula armata is probably capable of making more intense sounds than the Neobythies spp.

Dystroglycanopathies are muscular dystrophies caused by mutations in genes involved the in O-linked glycosylation of alpha-dystroglycan. Severe forms exhibit brain and ocular developmental abnormalities in addition to muscular dystrophy. While cerebellar dysplasia is a common feature of dystroglycanopathy, its pathogenesis has not been thoroughly investigated. Here we evaluate the role of dystroglycan during cerebellar development. Brain-selective deletion of dystroglycan does not affect overall cerebellar growth, but causes malformations associated with glia limitans disruptions and granule cell heterotopia that recapitulate phenotypes found in dystroglycanopathy patients. Cerebellar pathology in these mice is not evident until birth even though dystroglycan is lost during the second week of embryogenesis. The severity and spatial distribution of glia limitans disruption, Bergmann glia disorganization, and granule cell heterotopia rapidly increase during postnatal development. Astrogliosis becomes prominent at these same sites by the time cerebellar development is complete. Interestingly, there is spatial heterogeneity in the glia limitans and granule neuron migration defects that spares the tips of lobules IV-V and VI. The full spectrum of developmental pathology is caused by loss of dystroglycan from Bergmann glia, as neither granule cell- nor Purkinje cell-specific deletion of dystroglycan results in similar pathology. These data illustrate the importance of dystroglycan function in radial/Bergmann glia, but not neurons, during cerebellar histogenesis. The spatial heterogeneity of pathology shows that the dependence on dystroglycan is not uniform. Cognitive deficits are constant features of severe dystroglycanopathies, yet the precise molecular mechanism leading to neuronal dysfunction in these diseases is not known. Here, we show that dystroglycan interaction with dystrophin is required for the normal clustering of a subset of inhibitory synapses in Purkinje neurons. Using mouse models of dystroglycan mutants, we demonstrate that the number of gamma-aminobutyric acid receptor-containing synapses is significantly reduced in the absence of dystroglycan or portions of dystroglycan; a similar result is attained in dystrophin-deficient mice. Finally, we verify that the number of these receptors is retained when dystroglycan and dystrophin are preserved exclusively in Purkinje neurons. Our findings substantiate the notion that brain dystroglycan is important for neuronal function and suggest a molecular mechanism that may underline cognitive impairments in dystroglycanopathies.

Traumatic brain injury (TBI) causes life-debilitating conditions. While patient survival after a TBI has improved, the outlook for quality of life after TBI currently remains poor. In order to address this problem, there is a significant unmet need for new therapeutic options to prevent progression of deficits associated with TBI. To this end, we investigated two strategies to combat the deleterious affect of TBI. First, we targeted cerebral acidosis associated with TBI by testing whether disruption of acid sensing ion channel 1a (ASIC1a) in CNS, or buffering acidosis with sodium bicarbonate, could prevent neurological deficits after TBI. We next tested whether treatment with the neovel class of aminopropyl carbozoles, known as the P7C3 series, could also prevent TBI-associated neurological decline. Using the mouse fluid percussion injury model of TBI, we observed post-injury acidosis in the cortex, consistent with what has been shown in humans following brain injury. Administering HCO3- after fluid percussion injury prevented acidosis and reduced neurodegeneration. Because acidosis activates acid sensing ion channels (ASICs), we also studied AIC1a-/- mice and found reduced neurodegeneration after injury. Both HCO3-3 administration and loss of ASIC1a reduced functional deficits caused by fluid percussion injury. These results suggest that fluid percussion injury induces cerebral acidosis, which activates ASIC channels in the brain and contributes to neurodegeneration. Blocking ASIC1aactivity may thus offer a new therapeutic strategy to attenuate the adverse consequences of TBI. We next applied the blast injury model of TBI to test whether the P7C3 class of neuroprotective aminopropyl carbazoles would be of therapeutic benefit. In addition to preventing neuronal cell death, P7C3 molecules also preserved axonal integrity before neuronal cell loss in this model. The mechanism of P7C3 neuroprotection may be linked to its ability to activate the enzyme, nicotinamide phosphoribosyltransferase, which catalyzed the rate limiting step of nicotinamide adenine dinucleotide salvage pathway. Administration of the lead compound in the series, P7C3-S243, 1 day after blast-mediated TBI blocked axonal degeneration and preserved normal synaptic activity. P7C3-S243 administration also reduced neuronal functional deficits, including impaired learning, memory, and motor coordination in mice. We additionally reported persistent neurologic deficits and acquisition of anxiety-like phenotype in untreated animals 8-months after blast-mediated TBI. Optimized variants of P7C3 thus offer hope for identifying neuroprotective agents for conditions involving axonal damage, neuronal cell death, or both. Together, the results of this body of work identify novel therapeutic interventions that may attenuate deficits associated with TBI, and thus improve the quality of life in people after TBI.

Effect of Manipulation of Notch Signaling Pathway on Neural Stem Cell Proliferation in the Hippocampus Following Traumatic Brain Injury By Seung L. Kim A thesis statement submitted for degree requirement in Mater of Science Virginia Commonwealth University, 2019 Advisor: Dong Sun, MD. PhD. Department of Anatomy & Neurobiology The Notch signaling pathway is known as a core signaling system in maintaining neural stem cells (NSCs) in embryonic development and adulthood including cell proliferation, maturation, and cell fate decision. Proliferation of NSCs persists throughout lifespan in neurogenic niches and is often upregulated following neurological insults including traumatic brain injury (TBI). Therefore, NSCs are viewed as the brain’s endogenous source for repair and regeneration. We speculate Notch signaling pathway is also involved in injury-induced cell proliferation in the neurogenic niche following TBI. TBI, which is a leading cause of death and disability, has been a huge burden to our society. Many efforts have been made in attempt to treat and manage TBI. In this study, we examined the involvement of Notch signaling pathway in injury induced NSC proliferation in the neurogenic niche, by administering exogenous Notch ligands including, Notch agonist or antagonist. Adult rats were intraventricularly infused with Notch1 receptor agonists (anti-Notch1 antibody at the dose of 0.5, 2 or 4μg/ml), Notch1 receptor antagonist (recombinant Jagged1 fusion protein at the dose of 25, 50 or 100μg/ml) or vehicle for 7 days following TBI. 5-bromo-2-deoxyuridine (BrdU) was administered single daily via intraperitoneal injection to label proliferating cells for 7 days post injury. The animals were sacrificed on the 7th day at 2 hours after the last BrdU injection. Sequential vibratome sliced coronal brain sections were processed for proliferation marker BrdU, Ki67 or immature neuronal marker DCX staining. BrdU, Ki67 or DCX-labeled cells in the dentate gyrus of the hippocampus were quantified using unbiased stereological method. We found TBI in the form of moderate lateral fluid percussion injury (LFPI) induced cell proliferation was further augmented by 7-day infusion of Notch agonist (Notch1-2μg/ml) as shown by BrdU and Ki67 labeling. Further, 7-day infusion of Notch antagonist (Jagged1-50μg/ml) post-injury greatly reduced the number of BrdU+ cells. However, ambiguous dose related responses were also observed where 7-day infusion of higher dose of Notch agonist (Notch1-4μg/ml) resulted in reduced cell proliferation. No major changes in the numbers of newly generated neurons were observed across the animals, except a slight reduction in Notch agonist (Notch1-2μg/ml) and Notch antagonist (Jagged1-50μg/ml) infused animals as shown by DCX labeling. Infusion of Notch agonist or antagonist affects NSC proliferation following TBI suggesting the involvement of Notch signaling pathway in regulating post-TBI NSC proliferation in the neurogenic niche. For the unexpected opposite results of higher dosing of Notch 1 agonist, the presence of other Notch receptors regulating NSC in the neurogenic niche should be considered. Future studies involving selective manipulation of these Notch receptors and their downstream effectors would clear some results.

Synapses must continuously maintain stable function in order for neuronal circuits and higher-order systems to properly function. By necessity, tight regulation of molecules necessary for appropriate neurotransmission coupled with homeostatic forms of plasticity function to stabilize synaptic output. The Drosophila melanogaster larval neuromuscular junction (NMJ) is an excellent model synapse for investigating both homeostatic synaptic plasticity (HSP) and neurotransmission machinery. At the NMJ, post-synaptic impairments to neurotransmitter sensitivity (decreased quantal size) initiate HSP. A retrograde, muscle-to-nerve signal instructs the presynaptic neuron to increase neurotransmitter release (quantal content) to compensate for the post-synaptic impairment and maintain synaptic output. HSP can be separated into temporally distinct induction and maintenance phases, depending on the nature of the impairment. Acute blockade of glutamate receptors initiates rapid forms of HSP that restore synaptic output within minutes. Loss-of-function mutations in a gene encoding a glutamate receptor result in reduced quantal size, and as a result, expression of HSP over the lifespan of that animal. However, it is unclear whether these temporal phases are distinct processes with overlapping machinery, or whether both phases are part of a common process with temporal distinct signaling requirements. Here we show that, in addition to being molecularly distinct, the temporal phases are functionally distinct. We provide evidence that the long-term maintenance of HSP requires continuous inositol trisphosphate receptor (IP3R) and Ryanodine receptor (RyR) activities, but neither are necessary for the rapid induction phase of HSP. In addition, we investigated how mutations associated with Familial Hemiplegic Migraine Type 1 (FHM1) impact synapse function and seizure behavior. We show that flies expressing this mutant channel are susceptible to seizures. Further, neurons expressing a transgene for cacophony containing the FHM1 mutations R192Q and S218L in the analogous locations showed significant hyper-excitability. Concurrent knockdown of the gene Multiple inositol polyphosphate phosphatase 2 (Mipp2) attenuated hyper-excitable phenotypes. Additionally, Mipp2 knockdown or LiCl treatment, both of which should attenuate downstream IP3R signaling, mitigated susceptibility to seizures in adults. Together these results contribute to our understanding both of both the pathophysiology of migraine and seizures.

Although schizophrenia has been shown to have a substantial component, there is a paucity of known risk alleles. Furthermore, all of the known risk genes are of small effect sizes. Previously it has been shown that a 12 base pair insertional polymorphism in the in the C-terminal, opposite paired (Opa) domain of the MED12 gene known as MED1212bp represents a small but significant risk for a positive syndrome psychosis. In addition, the MED1212bp polymorphism is found in approximately 1.6 percent of X-chromosomes of northern European decent. Studies in zebrafish show that alterations in MED12 reduces staining for monoaminergic neuronal populations, including dopaminergic and serotonergic populations. However, precise mechanisms through which these changes occur are not known. My goal for this study was to use PC6-3 cells as a mammalian cell culture for studying cellular and transcriptional effects of MED12 in a dopaminergic model system. The approach I took was based on studies that have shown that overexpression of C-terminal proline, glutamine and leucine rich (PQL) and Opa domain constructs interact in a dominant negative manner with several transcriptional regulatory proteins that interact with MED12. GFP tagged PQL and Opa domain constructs were placed into a tetracycline inducible T-REx™ regulated expression vector and introduced into a previously generated PC6-3, TR156 cell line that expresses the Tet-Repressor molecule. In this study, I report a selection bias against stably transfected cell lines strongly expressing constructs containing the two C-terminal PQL-Opa protein domains of MED12. I also show that the described low levels of induction of that construct are associated with small, but significant alterations in nuclear morphology, possibly due to nuclear reorganization. Induction of PQL-Opa domains also increases in cell metabolism as measured by a tetrazolium salt assay, typically associated with increases in proliferation compared to the GFP controls or Opa domain alone. Interestingly, the MTS results in the stable cell lines were not reflected changes in cell numbers from direct cell counts performed by light microscopy, or changes in cell cycle distribution as measured by propidium iodide staining and fluorescence activated cell sorting (FACS). In addition I also show microarray gene expression data for both the stable tetracycline inducible lines, as well as transiently electroporated PC6-3 cells. For both the stable and transient expression experiments, the arrays were characterized by small fold changes, which were not validated by RT-PCR. The stable arrays did not produce any robust findings. However, gene ontology (GO) data, as determined by GoMiner analysis, from the transiently electroporated cells shows that 9 of the top 31 GO categories are related to changes in proliferation and cytoskeletal reorganization. However, despite this trend, the data from the GoMiner analysis was above the level of statistical significance (á = 0.05), as is indicated by the false discovery rates (FDR > 0.3). Analysis of the directionality of expression proved intriguing and demonstrated significant evidence of skewing in the pattern of differential expression of annotated genes where there was a significant tendency for the most significantly differentially expressed probes belonging to 13568 annotated genes to be more highly expressed genes in the electroporated GFP control construct cells than those with the PQL/Opa construct. This is also consistent with a broad overlap of the expression data with ChIP-seq data suggesting that the dominant negative effect may be spread over many MED12 regulated genes, in which case the low expression levels are particularly problematic. While the data from these experiments do not present a clear mechanism for MED12 function, they are informative in developing models of MED12 alteration, and potential improvements are discussed.