Background: Osteoarthritis (OA) is the most common musculoskeletal disease worldwide and a major cause of chronic pain. Treatment of OA pain is still suboptimal due to limited efficacy and considerable side effects of available analgesics. Pain in OA has a significant central component. Cyclooxygenases (COXs) and glial cells in the spinal cord and the periaqueductal gray (PAG) play a significant role in central sensitisation and pain modulation. Vascular endothelial growth factor-A (VEGF-A) is a key molecule in normal and pathological angiogenesis. Serine arginine protein kinase 1 (SRPK1), which phosphorylates serine arginine splice factor 1 (SRSP1), controls VEGF gene alternative splicing. This results in two splice variants; VEGF-A165a, which is pro-angiogenic and pro-nociceptive, and anti-angiogenic VEGF-A165b, which showed anti-nociceptive effects in models of neuropathic and inflammatory pain. Objective: This thesis investigated changes in COX expression and glial activation in the spinal cord and the PAG in the monosodium iodoacetate (MIA) model of OA. It also addressed the effects of VEGF-A165b and SRPK1 inhibitor SPHINX-31 on pain behaviour and joint pathology, as well as COX expression and glial activation in the spinal cord and the PAG in the same model. Hypothesis: VEGF-A165b and SPHINX-31 can prevent and/or reverse enhanced pain behaviour in the MIA model of OA, through involvement of spinal glial cells and COXs in the PAG and spinal cord. Vascular-astrocyte association in the PAG is enhanced in the MIA model of OA, and this effect is reversed by administration of SPHINX-31. Methods: Rats received an intra-articular injection of MIA (1 mg) in the knee. In one study, animals were treated with VEGF-A165b (i.p. 20 ng/g body weight twice weekly) on days 0-13 (VEGF(d0-13) group) or days 14-28 (VEGF(d14-28) group) after MIA injection; in another study, rats received SPHINX-31 (i.p. 0.8 µg/g body weight twice weekly; (MIA/SPHINX group)) for 19 days after induction of the model. Pain behaviour was monitored throughout the studies, at the end of which (day 28) tissues were collected for the assessment of joint histopathology and the evaluation of spinal COX-2 mRNA expression by PCR. In addition, immunofluorescence (IF) was used to assess COX-2 expression and glial activation in the spinal cord, as well as astrocyte activation and vascular-astrocyte association in the PAG. Results: VEGF-A165b significantly attenuated weight bearing asymmetry (%) in MIA rats on day 28 (29.58 ± 1.803 in MIA/VEGF(d0-13) group vs. 22.95 ± 2.088 in MIA/PBS group, p < 0.01; 29.23 ± 1.49 in VEGF(d14-28) vs. 22.95 ± 2.088 in MIA/PBS, p < 0.05). VEGF-A165b reversed mechanical withdrawal thresholds to the naïve level, but without reaching statistical significance. No significant changes in knee joint pathology were observed in VEGF-A165b treated MIA rats compared to the MIA/PBS counterparts. In the MIA/VEGF(d0-13) group, contralateral deep laminae of the dorsal horn had a higher percentage (%) of non-neuronal cells expressing COX-2 than the corresponding superficial laminae (3.26 ±1.16 vs 1.12 ± 0.43, p < 0.05), while no difference was observed in the MIA/PBS group. Administration of VEGF-A165b did not significantly affect spinal microglia and astrocyte activation, nor COX-2 expression in the PAG. SPHINX-31 had no significant effects on pain behaviour, joint pathology or spinal COX-2 expression in the MIA model of OA. On the other hand, MIA/SPHINX group exhibited a higher activation of spinal microglia than MIA controls (% of CD11b +ve cells in MIA/SPHINX-31 vs MIA/vehicle groups: 6.36 ± 0.89 vs 1.72 ± 0.38, p < 0.01). In addition, SPHINX-31 significantly increased astrocyte activation in the ipsilateral dorsolateral (DL) PAG relative to corresponding ventrolateral (VL) PAG (GFAP IF intensity: 12.89 ± 1.52 vs 8.46 ± 0.84, p < 0.05), and it increased vascular-astrocyte association (%) in the contralateral DL PAG relative to corresponding VL PAG (70.35 ± 7.68 vs 38.92 ± 8.19, p < 0.05). Interestingly, naïve rats had a significantly higher astrocyte activation and vascular-astrocyte association in the VL PAG than in DL PAG. Conclusions: VEGF-A165b exerted a significant antinociceptive effect in the MIA model of OA without affecting joint pathology, spinal glial cell activation or COX-2 expression in the PAG. SPHINX-31 did not reverse pain behaviour, but showed a potential effect on astrocyte activation and vascular-astrocyte association in the DL PAG relative VL PAG in the MIA model of OA.

Microglia play a central role in immune surveillance and modulation of neuroinflammation as well as playing a role in neurodevelopment. Microglia involve in the development of pathological pain in adults but not early in life. However little detail is known about the changing phenotype of microglia during development. We examined age-related changes in microglia following activation with pathogen- and damage- associated molecular patterns (PAMPs/DAMPs). Microglial cultures were prepared from neonatal postnatal day (P1) and adult (P40) rat brains and spinal cords. Immunocytochemistry, qRT-PCR and functional assays were used to identify age-related differences. Adult microglia display a pro-inflammatory immune profile characterized by significantly increased IL-1β mRNA levels in response to PAMPs and DAMPs. In contrast, IL-1β mRNA in neonatal microglia showed a slight increase after stimulation with DAMPs. Anti-inflammatory gene expression was significantly increased in neonatal microglia relative to adult microglia. Compared to adult microglia, neonatal cells had increased phagocytic activity when unstimulated and following activation with LPS and ATP. Moreover, the nuclear receptor Nurr1 may play a major role in reducing pro-inflammatory signalling and promoting the anti-inflammatory phenotype in neonatal microglia. Nurr1 isoforms are differentially expressed in neonatal and adult microglia, with the Nurr1a isoform being significantly elevated in neonatal cells. Using lentiviral vector-mediated expression of Nurr1 isoforms, we also show that over-expression of TINUR, a splice variant of Nurr1, in neonatal and adult microglia attenuates inflammation by trans-repression the IL-1β expression and trans-activation the IL-10 gene expression following ATP exposure. Together, these data provide evidence for age-related difference in microglial function during postnatal development. In addition, these findings demonstrate insight into the mechanisms by which Nurr1 might act, and suggest potential therapeutic targets for the treatment of neuro-inflammatory diseases.

Amyloid β(Aβ)-induced synaptic and neuronal degeneration has been linked to the memory loss observed in Alzheimer's disease (AD). Although Aβ-induced impairment of synaptic and nonsynaptic plasticity is known to occur before any cell death, the links between these neurophysiological changes and the loss of specific types of behavioural memory are not fully understood. This thesis introduces a behaviourally and physiologically tractable animal model to the Aβ field for the first time, allowing for an in-depth approach to investigating Aβ-induced memory loss to be explored. In Aβ 1-42- and Aβ 25-35-treated Lymnaea stagnalis, retrieval of consolidated memory is disrupted after single-trial conditioning and single-injection of synthetic peptide. All succeeding work builds upon these findings using a top-down approach to investigate how Aβ disrupts retrieval of consolidated memory. Neuronal and synaptic health were monitored over a 24 hour in vivo incubation period and other memory stages were considered to determine time points of memory vulnerability. In brains that displayed healthy neurons and degenerating synapses, only animals that were exposed to Aβ during the 24-48 hour post-training time points exhibited any behavioural deficits. All other behavioural responses remained normal. Focus then shifted to investigate the peptide, as opposed to behaviour, involved in the above mentioned experiments. After systemic injection, Aβ was found to penetrate the ganglia, enter cells, and localise to specific organelles by 24 hours exposure. Aβ morphology and structure were also monitored over the 24 hour incubation period, using transmission electron microscopy (TEM), formic acid extraction, silver stain, and western blot. A large distinction between the two peptides, Aβ 1-42 and Aβ 25-35, became apparent at this point and even when peptides were prepared using the same procedure, their effects on behaviour became drastically different. However, it is interesting to note that although the two peptides used are very different, under different preparation procedures they will both produce predominantly tetramer species after 24 hour in vivo incubation. Finally, investigations into disruptions of molecular signalling cascades were considered in order to correlate these disruptions to the observed Aβ-induced behavioural deficits. Specifically, molecular, pharmacological, and biochemical techniques were used to measure protein alterations and post-translational modifications, and to inhibit key protein components, involved in cAMP response element binding protein (CREB)-signalling pathways in Lymnaea brain after 24 hour in vivo incubation of Aβ. Phosphorylated CREB was found to be decreased in both Aβ-treated groups; this decrease pattern was also found in active protein kinase A (PKA) experiments. These experiments correlate memory deficits to Aβ-induced disruptions in PKA and CREB activity; however, PKA inhibition experiments indicate that this molecular cascade disruption is not sufficient to cause the observed behavioural deficits. Taken together, this work correlates Aβ-induced changes from a wide range of components involved in learning and memory, with Aβ-disrupted memory recall. Importantly as well, this work develops Lymnaea stagnalis as a novel model for Aβ research and continues to distinguish the two commonly used peptides, Aβ 1-42 and Aβ 25-35. By linking the effects of Aβ on defined neuronal circuits to behavioural deficits in a novel model, the Aβ field has been further developed in an important and unique way.

The nature and assessment of executive function are areas of active research. Many current assessments of executive function are complex, have limited reliability and validity, and suffer from task impurity, meaning other cognitive processes may indirectly influence task performance. Additionally, measures may be culture, language, or education bound limiting their use in certain populations (Miyake, Emerson, & Friedman, 2000; Miyake, Friedman, et al., 2000; Strauss, Sherman, & Spreen, 2006; Stuss, 2007). The purpose of this project was to develop a novel set of executive function measures to address issues with current clinical measures. The new measures 1) can be used in an ERP environment, 2) use the same stimulus set to address task impurity and 3) use simpler cognitive operations of inhibition, set-shifting, and updating, identified in previous research by Miyake et al., (2000). Twenty-nine undergraduate participants at the University of South Florida were administered currently used clinical measures of executive function theorized to engage in inhibition, set-shifting, and updating and the set of the novel tasks. ERP data was collected during the administration of the novel tasks. Behaviorally, conditions theorized to engage executive function resulted in slower response reaction time than control conditions. Additionally, behavioral results indicated that performance on novel tasks were differentially related to different clinical EF tasks. ERP differences were observed between both Go/No-Go conditions (inhibition) and among N-back conditions (updating). Results suggest the novel executive function tasks are tapping into different cognitive processes and may be a viable tool for studying executive function in the future.

Abstract not available

Examination of how the brain mediates emotional experience is now an area of significant and intense research interest. This is an important endeavour considering that emotion is a key component in vulnerability factors governing risk for mood and anxiety disorders. Recent neuropsychological and neuroimaging studies are also beginning to explore the effects of antidepressants on the processing of emotional stimuli in healthy participants to help understand the role of neurochemicals in affective behaviour more broadly. Unfortunately the literature is fraught with contradictions and complications resulting from the technique used, task instructions, selection of stimuli and gender differences. The aim of the current thesis therefore, was to investigate emotional processing in healthy participants and to examine the impact of serotonergic augmentation on this processing through the presentation of visual emotional stimuli and examination of self report, peripheral- and neurophysiological measures of emotional responsiveness. Seventy five images low in arousal content, selected from the International Affective Picture System (IAPS) and categorised as pleasant, neutral and unpleasant, were presented to participants in four experimental studies. Findings support previous literature suggesting that there is substantial overlap in frontal neural circuitry when the brain processes emotional images of different valence. Gender differences in the processing of visual emotional stimuli were also observed however suggesting the need for future studies to take such factors into account. In particular, females unlike males displayed right-sided, frontal, neurophysiological activations in response to unpleasant relative to neutral images. Emotional valence was also found to modulate heart rate (HR) thereby confirming the reliability and validity of the task-viewing paradigm. Augmentation of serotonin was found to suppress any differences in HR across the three differently valenced categories of images, while neurophysiological responses were potentiated during pleasant valence but suppressed during unpleasant valence. In summary, the studies included in this thesis provide evidence for neurophysiological modulation by emotional content and gender. In addition, the studies employ a more systems-based approach to the study of antidepressant action, through examination of the neurophysiological responses to visual emotional stimuli. This approach may lead to greater understanding of the functional consequences of neurochemical modulation on cortical networks involved in emotional processing.

Cognitive impairment affects approximately half of multiple sclerosis (MS) patients. The Multiple Sclerosis Neuropsychological Questionnaire (MSNQ) has previously demonstrated validity for detecting cognitive impairment in MS, and is quick and easy to complete. The objective was to validate an internet version of the MSNQ. The following were completed at home over the internet for 82 MS patients: (a) patient self-report version of the MSNQ (P-MSNQ), (b) informant version of the MSNQ (I-MSNQ), and (c) Centre for Epidemiological Studies Depression Scale (CES-D). Thereafter, patients completed in-office neuropsychological testing using the Brief Repeatable Battery of Neuropsychological Tests (BRB-N). Both the P-MSNQ and I-MSNQ were highly correlated with depression. The best-cut off score on the I-MSNQ was a 26, which gave a sensitivity of 72% and 60% for detecting cognitive impairment on the BRB-N. Given the modest sensitivity and specificity values, the MSNQ is not recommended for neuropsychological screening purposes over the internet.

Cognitive impairment affects approximately half of multiple sclerosis (MS) patients. The Multiple Sclerosis Neuropsychological Questionnaire (MSNQ) has previously demonstrated validity for detecting cognitive impairment in MS, and is quick and easy to complete. The objective was to validate an internet version of the MSNQ. The following were completed at home over the internet for 82 MS patients: (a) patient self-report version of the MSNQ (P-MSNQ), (b) informant version of the MSNQ (I-MSNQ), and (c) Centre for Epidemiological Studies Depression Scale (CES-D). Thereafter, patients completed in-office neuropsychological testing using the Brief Repeatable Battery of Neuropsychological Tests (BRB-N). Both the P-MSNQ and I-MSNQ were highly correlated with depression. The best-cut off score on the I-MSNQ was a 26, which gave a sensitivity of 72% and 60% for detecting cognitive impairment on the BRB-N. Given the modest sensitivity and specificity values, the MSNQ is not recommended for neuropsychological screening purposes over the internet.

Most of the extant humor research has focused on humor comprehension with only a few studies investigating humor appreciation as a separate construct. The purpose of this investigation was to determine the relation between humor and underlying cognitive processes. Literature on brain injured individuals has indicated that working memory, verbal and visual-spatial reasoning, cognitive flexibility, and concept formation are related to performance on comprehension tests of humor. In this study, cognitive processes underlying both verbal and nonverbal humor were investigated in a sample of healthy young adults. There is evidence that semantic and phonological humor are associated with different neural networks; therefore, both semantic and phonological humor were explored. Studies investigating physiological arousal and humor have indicated that arousal is necessary for the experience of humor. This suggests that the appreciation of humor may require the integration of cognitive and affective information, a process mediated by the ventromedial prefrontal cortex (VMPFC). Thus, a second goal of this study was to investigate the relationship between humor comprehension and appreciation and the VMPFC, by including experimental tasks that previously have been linked to VMPFC functioning. Participants included 94 undergraduate psychology students between the ages of 18 and 39 years. Participants watched film clips and listened to jokes. After the presentation of each joke and each film clip, they completed a humor comprehension/appreciation inventory developed for this study. They also completed measures assessing a range of cognitive abilities hypothesized to underlie humor perception. Hierarchical regression analyses revealed that verbal reasoning was predictive of semantic humor comprehension, indicating that verbal reasoning is a core cognitive ability for the comprehension of jokes in which the humor depends on factors other than simple word play. Cognitive measures were not predictive of phonological humor comprehension or nonverbal humor comprehension. Hierarchical regression analyses revealed that the indicators of VMPFC functioning did not correlate with either humor comprehension or humor appreciation and did not moderate the relation between humor comprehension and humor appreciation. Future research is necessary to elucidate the relationships between cognitive abilities and humor perception and to further explore the contribution of the VMPFC to humor appreciation.

Addressing issues with sensitivity and specificity in TBI assessment this study compared the performance on neuropsychological tests and results from qEEG assessment between a heterogeneous TBI (N=20) group and a matched normal control group (N=20). The TBI group was performed worse on all measures. Significant differences in performance were found in the domains of information processing speed and executive function. Effect sizes of these differences were large. This was also true for the amplitude of the qEEG parameter P3NoGo along with P3Go latency and theta power in the temporal and frontal lobes. Binary logistic regression revealed higher sensitivity and specificity when combining neuropsychological tests and qEEG parameters, suggesting qEEG parameters in  combination with neuropsychological tests to be good assets in TBI assessment.