SK channels are small conductance Ca2+-activated K+ channels expressed throughout the CNS. SK channels modulate the excitability of hippocampal CA1 neurons by affecting afterhyperpolarization and shaping excitatory postsynaptic responses. Such SK-mediated effects on activity-dependent neuronal excitability and synaptic strength are thought to underlie the modulatory influence of SK channels on memory encoding. Here,the effect of a new SK1 selective activator, GW542573X, on hippocampal-dependent object memory, contextual and cued conditioning, and trace fear conditioning was examined. The results demonstrated that pre- but not post-training systemic administration of GW542573X impaired object memory and trace fear memory in mice 24 h after training. Contextual and cued fear memory were not disrupted. These current data suggest that activation of SK1 subtype-containing SK channels impairs long-term memory. These results are consistent with converging evidence that SK channel activation suppressed behaviorally triggered synaptic plasticity necessary for encoding hippocampal-dependent memory. / Includes bibliography. / Thesis (M.S.)--Florida Atlantic University, 2015. / FAU Electronic Theses and Dissertations Collection

We sought to better understand human motor control by investigating functional interactions between the Supplementary Motor Area (SMA), dorsal Anterior Cingulate Cortex (dACC), and primary motor cortex (M1) in healthy adolescent participants performing visually coordinated unimanual finger-movement and n-back working memory tasks. We discovered modulation of the SMA by the dACC by analysis of fMRI BOLD time series recorded from the three ROIs (SMA, dACC, and M1) in each participant. Two measures of functional interaction were used: undirected functional connectivity was measured using the Pearson product-moment correlation coefficient (PMCC), and directed functional connectivity was measured from linear autoregressive (AR) models. In the first project, task-specific modulation of the SMA by the dACC was discovered while subjects performed a coordinated unimanual finger-movement task, in which the finger movement was synchronized with an exogenous visual stimulus. In the second project, modulation of the SMA by the dACC was found to be significantly greater in the finger coordination task than in an n-back working memory, in which the same finger movement signified a motor response indicating a 0-back or 2-back working memory match. We thus demonstrated in the first study that the dACC sends task-specific directed signals to the supplementary motor area, suggesting a role for the dACC in top-down motor control. Finally, the second study revealed that these signals were significantly greater in the coordinated motor task than in the n-back working memory task, suggesting that the modulation of the SMA by the dACC was associated with sustained, continuous motor production and/or motor expectation, rather than with the motor movement itself. / Includes bibliography. / Dissertation (Ph.D.)--Florida Atlantic University, 2015. / FAU Electronic Theses and Dissertations Collection

Multiple sclerosis (MS) is a prevalent and progressive autoimmune inflammatory disease affecting both white and gray matter and resulting in lesions and atrophy within the central nervous system (CNS) (Bermel & Bakshi, 2006; Confavreux & Vukusic, 2006; Cree, 2012; Friese, Schattling, & Fugger, 2014). Fine motor impairment, including manual motor speed and fine motor dexterity deficits, is common in MS patients (e.g., Benedict et al., 2011; Chipchase, Lincoln, & Radford, 2003). However, impairment does not progress uniformly across patients (Confavreux, Vukusic, Moreau, & Adeleine, 2000; Filippi & Rocca, 2011; Scalfari, Neuhaus, Daumer, DeLuca, & Muraro, 2013) and the association between disease burden and physical disability is moderate at best (Bermel & Bakshi, 2006; Filippi et al., 2013). Though the brain reserve hypothesis has helped to explain the clinico-pathologic dissociation between cognitive functioning and disease burden in MS patients (Sumowski et al., 2013; Sumowski et al., 2014a), there is no published literature on brain reserve and motor functioning in MS. Instead, only preliminary data have been presented on brain reserve and general physical disability (Sumowski et al., 2014b). As such, the purpose of this dissertation was to examine the protective effect of brain reserve, estimated via intracranial volume (ICV), on fine motor functioning in relapse-onset MS patients. A sample of 178 relapse-onset, right-handed MS patients underwent neuropsychological testing along with neurological examination, including magnetic resonance imaging (MRI). As part of the evaluation, patients were administered the Nine Hole Peg Test (NHPT; a measure of fine motor speed and dexterity) and the Finger Tapping Test (FTT; a measure of manual motor speed), which served as this study’s outcomes (i.e., dependent variables). Predictors (i.e., independent variables) included demographic variables (age, sex), disease variables (disease duration and disease phenotype, including relapsing-remitting MS (RRMS) or secondary-progressive MS (SPMS)), MRI estimates of disease burden (T2 lesion volume [T2LV], normalized brain volumes as measures of cerebral atrophy), and MRI-derived measures of ICV as an estimate of brain reserve. Results revealed that phenotype (r = .56, p < .001) significantly predicted performance on the NHPT, such that patients with SPMS did worse than patients with RRMS. Regarding disease burden, T2LV (r = .24, p = .001) and normalized gray matter volume (r = -.18, p = .019) predicted NHPT, with less disease burden associated with better performance. Greater ICV (r = -.21, p =.006) was also significantly associated with better performance on the NHPT. Next, phenotype (r = -.45, p < .001) predicted FTT with SPMS patients again performing worse than RRMS patients. Sex (r = .40, p < .001) was a significant predictor of FTT with men outperforming women, on average. For FTT, normalized gray matter volume (r = .36, p < .001) was the only measure of disease burden that predicted performance, with greater volume (i.e., less atrophy) associated with better performance. Similarly, greater ICV (r = .31, p < .001) significantly predicted better performance on the FTT. For both NHPT and FTT, interactions between measures of disease burden and ICV were not significant. As such, some evidence from this study was not consistent with the reserve hypothesis; however, this finding may be due to differences in the way brain reserve impacts motor outcomes (relative to cognitive outcomes). Nonetheless, as ICV was associated with better performance for both outcome measures, these findings provide partial support for the brain reserve hypothesis in fine motor functioning in MS. Therefore, findings from this study have real-life applications with regard to improved understanding of fine motor disability in MS and identification of patients at risk for upper extremity dysfunction, leading to the possibility of early intervention. Findings also have implications for informing clinical research in MS. Future research should examine the protective effect of brain reserve on fine motor functioning within larger cross-sectional samples (i.e., RRMS vs. SPMS), within primary-progressive MS (PPMS) patients, and when using additional measures of upper extremity disability (e.g., Grip Strength Test). Longitudinal research would also help to determine whether there is a moderating effect of brain reserve on fine motor disability progression as well as allow patients to serve as their own baseline, which would control for individual differences in motor functioning. Next, examining reserve in patients experiencing lesions and atrophy in specific brain regions underlying motor function (e.g., cerebellum and precentral gyrus) may help explain why interactions between disease burden and ICV were not significant within the present study. Finally, by testing the brain reserve hypothesis as it relates to fine motor functioning in non-clinical, healthy controls, it would be possible to determine whether the protective effect of reserve is present premorbidly.

The central nervous system controls many physiological processes including energy metabolism, immune response, reproduction, and development. In turn, hormones synthesized in and secreted by peripheral organs can be transported across the blood-brain barrier to modulate the development of the brain, the formation of new neurons, neural activity, behavior, and the secretion of brain-derived hormones. The central control of bone mass, mediated by the adipocyte-derived hormone leptin, has raised questions of whether the skeleton may signal back to the brain. In recent years, the Karsenty laboratory has uncovered the endocrine role of the bone-derived hormone osteocalcin. Through the use of a vast array of genetic tools, the Karsenty lab has discovered that osteocalcin is a potent regulator of glucose homeostasis, adaptation to exercise, energy metabolism, and male fertility. The multifunctional role of osteocalcin led us to hypothesize that it may act as a molecular means of communication between the skeleton and the brain. We asked whether osteocalcin could regulate brain development during embryogenesis and behavioral functions in adulthood. In addressing these questions, we observed that bone-derived osteocalcin crosses the blood-brain barrier, accumulates in discrete parts of the brain including the hippocampus, and binds to several neuronal populations to favor the synthesis of monoamine neurotransmitters (serotonin, dopamine, and norepinephrine), and to impede the synthesis of the inhibitory neurotransmitter, GABA. Osteocalcin-/- mice have increased anxiety and depression and impaired learning and memory when compared to WT littermates. We also uncovered that the absence of maternal osteocalcin during embryogenesis hinders brain development and causes defects in spatial learning and memory in the adult offspring. Upon characterizing the necessity of osteocalcin for brain development and cognitive function, we investigated whether bone health is a determinant of cognition, and whether osteocalcin may be sufficient to reverse age-related cognitive decline. In addressing the first question, we found that impairment in either bone formation or bone resorption negatively impacts both anxiety and memory. In addressing the second question, we found that osteocalcin is also necessary for the beneficial effect of young blood on cognitive functions. Finally, we observed reduced anxiety and improved memory in aged mice receiving osteocalcin peripherally. This action appears to require an increase in brain-derived neurotrophic factor levels in the hippocampus. Against the backdrop of our progressively aging population, it is important for future studies to determine whether osteocalcin may act therapeutically in humans to treat age-related cognitive decline. Additionally, to identify potential drug targets, it is important to fully characterize the molecular mechanism by which osteocalcin acts on neurons.

Despite extensive evidence documenting abnormal hypothalamic-pituitary-adrenal (HPA) axis functioning as a risk factor for the development of depression and other psychiatric disorders, and experimental evidence from acute stress manipulations, the effects of sustained cortisol alterations on clinically relevant cognitive-behavioural and neural processing remain poorly understood. The aim of this thesis was to characterise how non-acute changes in cortisol levels modify behavioural and neural biases implicated in stress-related disorders by following two complementary lines of evidence: firstly, by increasing cortisol via a direct pharmacological intervention; and secondly, by testing the ability of gut microbiota manipulations to alter cortisol reactivity. The first study found that sustained increases in cortisol following 10-day administration of hydrocortisone were associated with altered memory and emotional processing in healthy volunteers. Specifically, participants receiving hydrocortisone showed enhanced recognition of emotional words, while their neutral memory performance was unaffected despite lower parahippocampal and occipital activation during viewing and encoding of neutral pictures. Furthermore, we found that resting-state functional connectivity between limbic-temporal regions of interest (amygdala and hippocampus) and the striatum (head of the caudate), as well as frontal and prelimbic cortices was decreased. In contrast, hippocampal and visual processing during negative facial expressions, and functional connectivity between the amygdala and the brainstem at rest, were increased in the hydrocortisone versus placebo groups. Overall, these findings suggest that non-acute increases in glucocorticoids enhance processing of emotionally salient information in limbic-temporal regions, which may modulate further neural mechanisms of sensory and homeostatic relevance. Enhancements in declarative emotional memory following hydrocortisone also implicate the modulation of amygdalar-hippocampal interactions by cortisol. Conversely, neutral stimulus processing was found to be either reduced or unaffected across a number of cognitive and memory domains. A specific increase for negative processing was further supported by poorer self-reported well-being at the mid-point of the study in participants receiving hydrocortisone. In a separate study exploring the ability of prebiotic supplements to affect cortisol reactivity and emotional processing, a Bimuno-galactooligosaccharide prebiotic was found to reduce the waking cortisol response and increase positive versus negative attentional processing in healthy volunteers. While these effects were not found to be associated, they provide initial promising evidence of the ability to target the HPA axis and emotional processing via the gut microbiota in humans. Overall, this thesis supports the idea that stress-induced physiological changes after prolonged or repeated cortisol exposure are associated with neural and behavioural alterations, which in turn have been crucial in understanding neuropsychological mechanisms underlying psychiatric disease. A better stratification of the effects of sustained HPA axis alterations on psychiatrically relevant cognitive-emotional domains and neural mechanisms thus remains of high priority.

No description available.

Alzheimer’s Disease (AD) is the only condition in the top ten leading causes of death for which we do not have an effective treatment that prevents, slows, or stops its progression. Our ability to design useful interventions relies on (a) increasing our understanding of the pathological process of AD and (b) improving our ability for its early detection. These goals are impeded by our current reliance on the clinical symptoms of AD for its diagnosis. This characterizations of AD often falsely assumes a unified, underlying AD-specific pathology for similar presentations of dementia that leads to inconsistent diagnoses. It also hinges on postmortem verification, and so is not a helpful method for identifying patients and research subjects in the beginning phases of the pathophysiological process. Instead, a new biomarker-based approach provides a more biological understanding of the disease and can detect pathological changes up to 20 years before the clinical symptoms emerge. Subjects are assigned a profile according to their biomarker measures of amyloidosis (A), tauopathy (T) and neurodegeneration (N) that reflects their underlying pathology in vivo. AD is confirmed as the underlying pathology when subjects have abnormal values of both amyloid and tauopathy biomarkers, and so have a biomarker profile of A+T+(N)- or A+T+(N)+. This new biomarker based characterization of AD can be combined with machine learning techniques in multimodal classification studies to shed light on the elements of the AD pathological process and develop early detection paradigms. A guiding research framework is proposed for the development of reliable, biologically-valid and interpretable multimodal classification models.

Prenatal alcohol exposure (Fetal Alcohol Syndrome [FAS] and Fetal Alcohol Spectrum Disorders [FASD’s]) represents the leading preventable cause of intellectual disabilities in the western world, with FASDs estimated to affect approximately 2-5% of live births in the United States at an approximate annual cost of $3.6 billion (CDC, 2015; May et al., 2009). Ethanol (ETOH) exposure during development can lead to a variety of long-term behavioral impairments including problems with executive functioning, motor coordination, spatial learning, attention, and hyperactivity (Jones, 2011; Mattson & Riley, 1998). Much research has been conducted to develop pharmacological and/or environmental interventions to reduce these deficits, however, there are currently no clinically approved medications to treat the deficits related to fetal ETOH exposure. The current study used a developmental “3rd trimester” ETOH exposure model in neonatal rats to test the hypothesis that compounds targeting the nicotinic system will reduce deficits associated with ETOH exposure. Both compounds demonstrated promise in reducing some of the effects of developmental ethanol exposure, with DMXB-A treatment after ethanol exposure reducing balance deficits in females and spatial memory deficits in males. Solidago nemoralis treatment after ETOH exposure reduced learning and memory deficits in males and balance and executive functioning deficits in both sexes. With these results and previous work in this lab and others there appears to be ample evidence for their usefulness in reducing various forms of neurotoxicity. The long-term goal of this research is to evaluate the usefulness of both DMXB-A & Solidago nemoralis (SN) in treating deficits related to developmental ETOH exposure in humans and hopefully develop a treatment for these disorders.

Objective: The purpose of this study was to assess the influence of three single nucleotide polymorphisms (SNP) previously associated with Alzheimer's disease on specific domains of cognition, when controlling for Apolipoprotein E gene (APOE), in a sample of individuals with Alzheimer's disease. Methods: The data were drawn from the Alzheimer's Disease Neuroimaging Initiative database, a comprehensive, longitudinal database of controls, persons with mild cognitive impairment, and persons with mild Alzheimer's disease. Each subject has a full neuropsychological assessment, neuroimaging, genetic sequencing, and physical evaluation. For the purposes of this study, individuals were selected based on the presence of the three SNPs of interest: CR1 (rs3818361_T), CLU (rs11136000_T), and PICALM (rs3851179_A). Each SNP was then measured against the available tests of the ADNI neuropsychological battery that measured immediate and long delay memory, semantic fluency, and confrontation naming. Results: Only the CR1 SNP (rs3818361_T) had significant findings. The presence of the CR1 SNP associated with lower performance on logical memory recall total score, AVLT immediate recall trials 2 and 4, AVLT delayed recall, and confrontation naming in the 12-month control group. Logical memory and AVLT delayed recall were also negatively associated with CR1 in the 12-month AD case group. Discussion: These results support previous findings that the CR1 SNP rs3818361_T is a risk factor for cognitive impairment in individuals with and without AD. Such findings can aid in the earlier detection of Alzheimer's disease, risk for domain specific cognitive impairment, and novel targets for personalized pharmacotherapy.

Abstract not available