The negative behavioural and emotional symptoms of Post-Traumatic Stress Disorder (PTSD) have been extensively reported in the literature. However, much less is known about the neuropsychological and neurobiological characteristics of the disorder. This thesis consists of two papers, the first being a review which highlights the emerging picture of literature in the field of neuropsychology in PTSD, with particular reference to findings in those cognitive domains of general intellectual functioning, memory, attention and executive function. Given that the findings associated within these domains are mixed, the second paper reports the outcome from a neuropsychological study of cognitive differences that was conducted to contribute to current knowledge in the area of neurocognition and visual memory in PTSD in particular. Trauma exposure, current PTSD, depressive and anxiety symptoms and performance on a range of neuropsychological tests were examined in tertiary care outpatients with PTSD (n=26), individuals who had been exposed to severe trauma but without current PTSD (n=26), and healthy controls (n=26). In addition to previously reported deficits in verbal learning and fluency in PTSD, deficits in visual spatial memory were also found. These observable deficits in visual memory may reflect characteristic features of PTSD, such as reported difficulties in remembering certain aspects of traumatic events and the presence of visual flashbacks. It is uncertain whether these deficits represent a risk factor for PTSD, or a consequence of trauma, as suggested by research in animal models.

The ergochromes possess useful anti-tumour properties whilst chromones are useful drugs for the treatment of allergic asthma. The aim of the project was to synthesise ergoflavin or an analogue for the first time, and to this end novel synthetic methods for a, 6-unsaturated ketones and oxygenated dienes were developed. Two major routes are described: The first uses aliphatic starting materials and allows the construction of highly substituted chromones by an intramolecular Diels-Alder reaction. To achieve this a synthetic method to novel phenylthio substituted 3-unsaturated ketone equivalents ( a'-phenylthio-3-amidoketones) was developed. It consisted of nitrile oxide additions to l-phenylthioprop-2-ene, whilst additions to 1-phenylsulphinyl-l,2-propadiene were also investigated, The second route involved the use of a preformed aromatic ring and; (a) an intramolecular Diels-Alder reaction to form a pyrone ring or - (b) an intermolecular Diels-Alder reaction and subsequent Friedel-Crafts cyclisation to give a pyrone ring. For this, a selenium dlene protection, alkylatlon and deprotection methodology was developed. Depending upon the substrate and oxidative conditions a, 3-unsaturated ketones, allylic alcohols, dienes and lactones were obtained, A second route to 4-oxygenated-l,3-butadienes provided the impetus to develop a titanium reagent for the oleflnation of 4-substltuted-3-buten-2-ones, Finally, an investigation into radical cyclisatlons of allylically substituted phenylseleno substrates was made.

This thesis represents an attempt to further our knowledge of the ophthalmic complications of spina bifida and hydrocephalus by means of literature review and a long term clinical study, and to determine whether regular ophthalmic supervision can assist in the general management of affected children. The ophthalmic complications of spina bifida have often been reported in the literature and thought to merit regular supervision of affected children, yet few centres currently offer this service. In this study 322 children attending one regional centre were examined repeatedly over a six year period by one ophthalmologist. Ophthalmic complications were found to be very common. They frequently provided evidence of raised intracranial pressure due to shunt dysfunction even when other objective evidence was lacking. Every spina bifida and hydrocephalus clinic should have an ophthalmalogist in its medical team. Preservation of visual function and early diagnosis of raised intracranial pressure in these children should result from this arrangement.

Intrinsic protein folding pathways are modulated by molecular chaperones, such as the diverse group of heat shock proteins (Hsps). Among these is the small heat shock protein (sHsp) family which in the mammalian genome consists of 10 low molecular weight (15-30kDa) members. The sHsps have classical chaperone functions but additionally contribute to pathways that protect against cellular stresses, maintain the cytoskeleton, prevent protein aggregation and regulate apoptosis. They contain a characteristic C-terminal α-crystallin domain, which is exclusive to the sHsp family. In addition to their constitutive expression under physiological (non-disease) conditions, they are also induced under conditions of stress/heat shock which is thought to play a role in response to protein misfolding that underpins disease. There are a wide range of diseases in which the sHsps function or are dysfunctional by mutations, such as neurodegenerative disorders, cataract, and desmin related myopathy. Each of the 10 sHsps is believed to have a unique expression profile. Seven of the sHsps are expressed in heart and muscle, but little is known about their precise expression and/or physiological role in the CNS. In the present study the expression of the mammalian sHsps in various mouse tissues including the brain was investigated. This provided evidence for the constitutive expression of 4 sHsps in the brain. In situ hybridization using naïve adult mice revealed a distinct white matter (oligodendrocyte) specific expression pattern for HspB5 (αBcrystallin). HspB1 (Hsp25) and HspB8 (Hsp22) demonstrated overlapping expression in the lateral and dorsal ventricles of the brain, as well as expression in a distinct set of motor neurons in the ventral horn of the spinal cord. Further, cellular immunostaining and subfractionation of brain tissue supports a distinct cellular and subcellular protein expression of HspB1, HspB5, HspB6 (Hsp20) and HspB8 in the brain. Both HspB5 and HspB6 were enriched in the myelin fraction. In view of the potential for induction of these sHsps by stress and modulation in chronic brain diseases we systematically investigated the sHsp signature in two distinct models of intracellular (R6/2) and extracellular (ME7) proteinopathies. These models recapitulate key features of Huntington’s and prion disease, respectively. Analysis of the sHsps in the R6/2 Huntington’s disease (HD) mouse model showed a specific down-regulation of HspB5 in the white matter at all time points analyzed. All other sHsps investigated did not change in this model of HD. Analysis of the sHsps in ME7 prion disease showed up-regulation of HspB1, HspB5 and HspB8 in the hippocampus. For HspB1, this was selective to an anatomically defined sub-population of astrocytes distributed in the stratum radiatum. In contrast, all GFAP positive astrocytes throughout the hippocampus exhibited induced expression of HspB5 and HspB8. Based on QT-PCR data, the changes in expression of the sHsps in either model was not under transcriptional control, suggesting translation/posttranslational regulation. The differing results in the two models suggest that the presence of intracellular (R6/2) or extracellular (ME7) aggregates may dictate the sHsp response associated with non-neuronal cells. In view of the emerging significance of non-neuronal cells in chronic diseases the data supports adaptive and differential responses that might contribute to and/or provide a route to therapy of distinct aspects of neurodegeneration.

Huntington's Disease (HD) is one of many neurodegenerative diseases that are associated with protein misfolding, aggregation and oxidative stress. While several changes in the redox homeostasis have been shown to occur in HD animal models and HD brains, the formal relationships between intracellular protein misfolding that occurs in HD, redox dysregulation and cellular toxicity are unknown. Therefore, several cellular models of intracellular polyglutamine (polyQ) protein misfolding were established for mechanistic studies. Various in vitro transient and stable cell expression systems expressing an N-terminal fragment of huntingtin (htt) (httExon 1, httEx1) with/or without a polyQ expansion and fused to fluorescent proteins were characterized. Mutant httEx1 (mhttEx1) constructs expressed in both neuronal and non-neuronal cell lines produced early polyQ aggregates and intracellular inclusion bodies (IBs) followed by cell toxicity that increased over time in time-course experiments. Using oxidation-sensitive probes, reactive oxygen species (ROS) were measured in polyQ-expressing cells using single, live-cell imaging analysis by confocal microscopy or population assays in order to explore the relationship between polyQ aggregation, ROS production and cellular toxicity. This study highlighted an early increase in ROS due to the expression of aggregation-prone mhttEx1 in both transient and stable cellular systems that coincided with polyQ aggregation, but preceded cell death. Suppression of ROS and toxicity was achieved by two antioxidant compounds (L-NAC and Trolox). Moreover, the use of MitoQ (Coenzyme Q10 covalently attached to triphenylphosphonium cation (TPP+)) at nanomolar concentrations abrogated the increased ROS due to mhttEx1 suggesting a mitochondrial origin of ROS. Given that molecular chaperones regulate the folding/misfolding of proteins and are involved in the regulation of the cellular redox homeostasis, the role of the redoxactivatable chaperone DJ-1 in HD was investigated. Protein expression analysis in HD cell models, a rodent model of HD and human HD brain samples showed an up-regulation of DJ-1 protein expression compared to control samples. Oxidation of DJ-1 was also elevated in the human HD cortex. To test for a functional role of DJ-1 elevation and oxidation in HD, DJ-1 was overexpressed with wild-type or mhttEx1 in cell lines and mouse primary astrocytes. Overexpression of DJ-1 accelerated mhttEx1 aggregation and toxicity both of which could be suppressed by exposure of cells to mild oxidants suggesting that DJ-1, when redox-activated to a chaperone, modulates polyQ aggregation and toxicity. This hypothesis was tested by overexpression of mhttEx1 with a DJ-1 mutant lacking a critical redox activatable cysteine (Cys106). The C106S-DJ-1 mutant lost its ability to reduce polyQ aggregation and toxicity under oxidising conditions upon co-expression with mhttEx1 suggesting that DJ-1 indeed functions as a modulator of polyQ misfolding and toxicity. Together this work suggests that ROS may be produced during polyQ aggregation and is involved in cellular toxicity. This study also shows that DJ-1 regulates both, polyQ aggregation and toxicity in cell models and given the increased DJ-1 expression in vitro and in vivo (human HD), this protein could be a potential target for HD therapy.

No description available.

No description available.

A remarkable feature of the human visual system is that it is possible to extrapolate a large amount of information about the three-dimensional structure of the environment simply from the pattern of light that falls on the retinae. This information is derived from a number of different cues to depth. The mechanisms by which these are encoded in the brain, combined into an overall percept, and subsequently interpreted are reasonably well understood. However, individuals who participate in studies of depth perception tend to have acute sensitivity to certain depth cues, meaning that the consequences of individual differences in depth perception have been largely ignored. In this thesis I investigate how individual differences in the ability to utilise a single cue, binocular disparity, affects overall perception of depth and then go on to explore the wider function significance of such a deficit. I also examine whether an underlying deficit in stereopsis may account for some of the perceptual differences observed in autism spectrum disorder (ASD). The first set of experiments explored the consequences of individual differences in stereopsis upon perception. The initial study of this thesis used a shape constancy paradigm to identify how individual cues to depth are utilised and combined in typical children and adults. I report that while children are more sensitive to certain depth cues compared to adults, they still show some degree of cue combination (though only for higher- level information). In addition, I observed that an inability to use binocular information appears to cause re-weighting to occur in favour of monocular cues, regardless of age. In the second study, I used the same paradigm to explore depth cue sensitivity and combination in typically-developing (TD) and ASD teenagers. The results from this experiment indicated that contextual and binocular information interact when creating an overall percept of depth. A main effect of ASD diagnosis was found, with this group reporting perception that was less biased and closer to the raw sensory input. Although participants with ASD exhibited poorer stereoacuity than their TD counterparts, this did not explain the differences between the groups. I propose this indicates that perceptual differences in autism likely stem from underlying neurological differences specific to the disorder as opposed to a more general stereopsis deficit. The third study assessed the combination of ordinal and metric depth cues in TD and ASD adults. Cue integration did not depend on sensitivity to disparity or autism diagnosis. Unlike previous research, and inconsistent with perceptual theories of autism, I found that individuals with ASD automatically integrated depth cues, even when it was not advantageous to do so. Additionally, I found that the processing of uncrossed disparities was particularly difficult for those with an ASD. The second part of the thesis aimed to characterise the functional significance of impaired stereopsis. For the fourth study, I wanted to establish whether the functional significance of stereopsis followed a developmental trajectory. I was also interested if the motor deficits observed in those with poor stereopsis were limited to hand-eye coordination tasks. Using three tasks derived from a standardised test of motor proficiency – catching a ball, balancing on one leg, and bead-threading – I measured the effect of binocular vision and stereoacuity on motor ability. Stereoacuity affected performance across a range of tasks involving the use of fine and gross motor skill, and – importantly – the effect of stereopsis did not change with age. In the final study, I enquired as to the further-reaching consequences of poor stereopsis. Using a quantitative survey I aimed to establish how stereopsis, motor skills, and social skills related to one another. While motor ability mediated the relationship between stereopsis and social skill, stereopsis also directly contributed to social skill, causing me to suggest that the functional significance of stereopsis is not limited to motor ability. It is concluded that while individual differences in stereoacuity may affect the amount of depth experienced, they do not affect the ability to combine different cues to depth. While those with ASD experience differences in perception, these cannot be attributed to the increased prevalence of stereopsis impairment. It does, however, seem that individual differences in stereoacuity impact upon the development of motor proficiency and social skill, which are typically compromised in those with ASD.

Alzheimer’s disease (AD) is a progressive neurodegenerative disease defined by severe memory loss and the accumulation of amyloid plaques and neurofibrillary tangles in the brain. The experiments presented in this thesis examined cognitive performance in a well-­‐characterised mouse model of AD, the APPswe/PS1dE9 (TG) mouse, at 4-­‐5 months old prior to extensive amyloid plaque deposition. The experiments employed were associative learning tasks, which are not often used to measure cognitive performance in classical neuroscience research into neurodegenerative disease. Chapter 1 looked at appetitive Pavlovian cue and context conditioning and extinction, and found some evidence of impaired contextual discrimination during conditioning. Cue conditioning and extinction was found to be intact in the TG mouse model. Chapter 2 looked at appetitive Pavlovian delay and trace conditioning before examining the ability to time the arrival of the unconditioned stimulus (US). No genotype differences were found during delay or trace conditioning; however, TG mice were impaired (lost precision) in their ability to time the arrival of the US during test trials. Chapter 3 examined recognition memory performance, via the spontaneous novel object recognition (sNOR), relative recency (RR) and context priming (CP) tasks, interpreting the results in terms of Wagner’s SOP model of memory. No genotype differences were found in the sNOR or RR tasks, supporting intact stimulus-­‐generated priming; however, evidence from Bonardi et al. (2016) and non-­‐significant trends in the CP task supported impaired retrieval-generated priming. Chapter 4 looked at the levels of neuro-­‐inflammation (microglia) in the cortex, hippocampus and striatum to assess the possible early contribution of inflammation on the development of AD. This chapter reported greater levels of microglia in the hippocampus and striatum of TG mice compared to wild types. Greater microglia clusters were also seen in the cortex and hippocampus of TG mice compared to wild types. The results from this thesis show evidence of impaired cognitive performance, prior to extensive plaque deposition, in associative learning tasks that are not routinely employed in neuroscience research. Further work is required in these learning tasks to establish whether they could be effectively used to diagnose AD at an early stage.

The British population are increasingly using mobile devices (e.g. smartphones, tablets) to gamble. The empirical work in this thesis looks at how the interaction of gambling’s schedule of reinforcement and mobile device behaviours accelerate the acquisition of learned maladaptive behaviours. The first four chapters report psychometric modelling of gambling prevalence data to understand problem gambling further and identify key indicators relevant to associative processes in gambling behaviour. Chapter 2 reports a taxometric analysis of problem gambling assessment data to test whether these screens measure a dimensional or latent class model, finding stronger support for the latter. However, this only identified a small taxon consisting of around 5% of gamblers endorsing more than one problem gambling symptom. Chapter 3 reports the use of latent class analysis to examine distinct subtypes of responding to different screens, findings a common three-class model that showed signs of a mixed latent structure: the same taxon as Chapter 2 was observed, but the three classes showed little overlap in symptom count. Chapter 4 reports further work modelling the sociodemographic characteristics of these different subgroups. Together the data from these chapters were used help to identify indicators of those most likely to a) be most susceptible to gambling harm and b) common to all problem gamblers. In Chapter 5 a Monte Carlo analysis was conducted to understand the efficacy of taxometric procedures on binary variables, before replicating the taxometric analysis reported in Chapter 2 using dichotomous variables and extending the work to the South Oaks Gambling Screen. The indicators derived from these chapters were then used in laboratory and field studies to study mobile gambling behaviour. The laboratory study in Chapter 6 manipulated two behavioural processes, trial spacing and partial reinforcement, that are relevant to mobile gambling behaviour, showing how a mobile-like schedule is related to increased perseverance and loss-chasing. The same paradigm was used to deliver an experiment on participants’ mobile phones in a field environment in Chapter 7. They further demonstrate that a mobile style schedule of reinforcement is associated with considerable persistence in the face of mounting losses, as participants continued to persevere in the face of losses despite a free choice to cease playing. Finally in the discussion I apply the key themes of the thesis to in-play betting, a form of play that has been heavily promoted alongside mobile gambling, and to an understanding of behavioural addictions.