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The settler colonial family as a site of trauma for women in selected novels by New Zealand women writers
No full textThis thesis examines the depiction of the settler colonial family as a site of trauma from a female-gendered perspective in selected novels by New Zealand women writers. I argue that women are vulnerable to psychic trauma through their subordinate and marginalized positions in the heteropatriarchal formulation of the settler colonial family and the sociocultural, economic and political structures and norms of settler colonialism. I use the relationships and affective dimensions of family as the lens to examine the ideological and material manifestations of settler colonialism in New Zealand society and culture, focusing on their impact on women.
The temporal timespan of the selected novels – The Story of a New Zealand River (1920) by Jane Mander, The Butcher Shop (1926) by Jean Devanny, Wednesday’s Children (1937) by Robin Hyde, The Book of Secrets (1987) by Fiona Kidman, Enemy Territory (1997) by Elspeth Sandys, and Rain (1994) by Kirsty Gunn – demonstrates that settler colonialism is a persistent structure that continues to exert a pervasive influence on the family in the postcolonial period. Each of the novels depicts not only how trauma impacts on an individual woman, but also what it reveals about the interrelationships between trauma experienced in the interpersonal affective intimacies of the family and the broader sociocultural and historical context.
I draw on trauma theory to examine the manifestation of traumatic symptomology and sequelae, and to situate the interpersonal locus of individual trauma in its sociocultural and historical context. Structural, non-event-based trauma theories which encompass relational, inter-generational, cumulative and insidious trauma open up ways of exploring the selected novels as trauma narratives. Feminist trauma theorists expand contemporary understandings of trauma through their foregrounding of female experiences of trauma in the interpersonal realm. Their contributions are important for the theoretical frame of my argument that the trauma women experience in the familial locus needs to be understood within its wider context. The novels call attention to the importance of examining how the power relations of the settler colonial family continue to render women vulnerable to psychic trauma
Managing the Impacts of Airbnb: A Case Study of Queenstown, New Zealand
No full textAirbnb is a new phenomenon that has transformed accommodation in the tourism industry and expanded across the globe. The operation of Airbnb involves individuals renting out rooms in their homes or renting entire homes on an online marketplace, as a means of short-term accommodation. Media attention has focused on the negative implications of Airbnb, such as a reduction in housing supply and neighbourhood nuisance. Yet if well managed, the platform has the potential to contribute positively to economies and societies. Airbnb is autonomous in nature, as transactions take place between the ‘host' and consumer. Therefore, regulation and enforcement are difficult to implement.
This research sought to investigate the positive and negative impacts of Airbnb in the context of Queenstown. The location was chosen as the case study for the research as it is a prominent tourist hub in New Zealand that is already struggling to provide sufficient infrastructure to facilitate growth in visitor numbers. Using qualitative methods, the research also sought to investigate current and future regulatory and non-regulatory approaches to manage the effect of Airbnb.
The research finds that Airbnb exacerbates issues in the District such as housing affordability and availability, staff retention issues and neighbourhood nuisance. Conversely, it was also found that Airbnb generates beneficial impacts for the community such as a profitable opportunity for local residents, contributions to the tourism industry and diversifying the accommodation market. The study also found that while some adverse impacts are directly addressed through QDLC’s current regulation, other impacts are forfeited.
The research is significant as it may help to inform local authorities on future management strategies to maximize the potential benefit, and diminish adverse impacts, that Airbnb could have in tourism destinations. As a result, the study concludes by suggesting possible management strategies which seek to reduce and address adverse impacts associated with the platform. Recommendations include the implementation of a Visitor Levy, the development of a Workers Village and/or the incorporation of housing affordability and availability considerations into current Residential Visitor Accommodation regulation
Impacts of an eye invading parasite on the behaviour and ecology of its freshwater fish host
No full textParasites are increasingly shown to impact ecosystem processes such as population dynamics and food web interactions. This can be accomplished by altering the host’s behaviour as a side-effect of infection, a response of the host to being infected, or through direct manipulation by the parasite. Some parasites, such as those that infect the sensory organs, are more likely to impact the behaviour of their host than others. Diplostomid trematodes often infect the eyes (e.g. lens, humours, or retina) of fish as larvae where they can impact various behaviours such as escaping predators and finding food. Tylodelphys darbyi is the only identified diplostomid in New Zealand. In its juvenile stage, this parasite resides in the humours of common bully, or toitoi, Gobiomorphus cotidianus, and is particularly abundant in the fish population of Lake Hayes. In this thesis, using a series of laboratory experiments, I address the impact T. darbyi has on its host’s 1) ability to react to predators, 2) choice of microhabitat, 3) ability to compete with conspecifics, 4) personality traits, as well as 5) determine the parasite’s distribution among South Island lakes. I demonstrate that there appears to be no impact of the parasite on the host’s ability to avoid predation, however as infection increases fish spend more time actively moving about away from shelter. The more T. darbyi are present in the eyes of fish, the more likely fish are to stay closer to a food source, share a shelter, and for males to be darker in colour. Further, infection with T. darbyi appears to impact personality traits (boldness, activity, exploration, and aggression) in fish, and based on a comparison with fish from another lake where T. darbyi is absent, the parasite might also drive population-level differences in behaviour. Overall, the influence of T. darbyi on fish behaviour is subtle rather than pronounced, but detectable across multiple behaviours. Finally, I demonstrated that T. darbyi has a broader distribution on the South Island than previously recorded, and I also used molecular markers to uncover 2-3 more species of diplostomids in New Zealand, all also found in G. cotidianus. These findings indicate that the parasite impacts the behaviour of bullies in the study population, i.e. Lake Hayes, that it has the potential to drive population-level differences in its host, and that it is only one of several species of diplostomid trematode parasites in the South Island, each of which may exert its own impacts on fish behaviour. Gobiomorphus cotidianus is a ubiquitous presence in New Zealand freshwaters and as such any factor that impacts their behaviour and ecology can have wide ranging implications. Finally, this thesis further brings to light the underappreciated role of parasites in generating inter-population and inter-individual differences in host behaviour
The early LARC catches the sperm: a qualitative and normative exploration of proactive provision of contraception in Aotearoa
No full textNew Zealand adolescents are at risk of unintended pregnancy; by not routinely using contraceptives, or using methods with higher failure rates. Adolescents face barriers accessing most forms of contraception, including long-acting reversible contraceptive methods. Addressing the barriers could improve uptake of effective methods of contraception, reducing the risk of unintended adolescent pregnancy. On these grounds, I investigated the concept of proactive long-acting reversible contraception provision, with tiered contraceptive counselling. Before assessing costs and feasibility of a proactive programme, the acceptability of such a programme should be determined. To gauge acceptability, I consulted with New Zealand adolescents (recipients), and New Zealand general practitioners (providers) using a qualitative research methodology. I then conducted a normative ethical inquiry of the ethical issues surrounding proactive contraception provision.
I consulted with female adolescents in four focus groups. We discussed topics of sexual health, contraception, and specifically discussed proactive long-acting reversible contraception provision. I performed nine general practitioner semi-structured interviews – these began with discussion of adolescent sexual health, contraception, and then discussed proactive long-acting reversible contraception provision. I used a general inductive thematic analysis approach to analyse transcripts.
The focus group and interview participants were generally positive about the concept, emergent focus group themes were reproductive health fear, sex and body shame, adolescents’ requirements for sexual health provision, barriers to contraception, and sexual health knowledge, Emergent interview themes were contraceptive decision making, the general practitioner role, sexual activity, social context, gauging adolescent understanding, and youth.
These focus groups and interviews indicated that the concept of proactive long-acting reversible contraception provision is acceptable to both adolescents and to general practitioners. The focus groups and interviews prompted me to shift my position from a proactive long-acting reversible contraception provision model to a proactive contraception provision model which did not focus on long-acting reversible contraceptives alone. This shift was a response to what the findings of the empirical work suggested, as proactive contraception provision should allow for the needs of a wider range of adolescents to be met.
To further explore the topic, I undertook a normative ethical inquiry, exploring the benefits and harms of a proactive contraception provision model. From this, I determined that proactive contraception provision could enhance reproductive autonomy, while providing benefits that would outweigh any potential harms.
Proactive contraception provision to increase adolescent uptake of effective contraceptive methods is therefore a concept worth pursuing. Such an initiative would improve adolescents’ contraceptive knowledge, and could decrease unintended teenage pregnancy by empowering adolescents to control their fertility in a way that suits them
Social problem solving and language skills in children with and without attention deficit hyperactivity disorder (ADHD)
No full textChildren with Attention Deficit Hyperactivity Disorder (ADHD) often have difficulties interacting socially with peers and adults. The research in this thesis explored the social problem solving skills and social functioning of children with and without a diagnosis of ADHD, as well as the underlying mechanisms that may be contributing to children’s social problem solving abilities and social functioning. The potential mechanisms considered in the thesis included structural and pragmatic language abilities, executive functioning, theory of mind skills, and symptoms of inattention and hyperactivity/impulsivity. The impact of age, gender, and estimated IQ were also considered in analyses.
The research used a combination of parent questionnaires and children’s own performance, when assessing children’s social functioning, social problem solving, and language skills. Children’s social problem solving abilities were assessed using three separate social information processing tasks. One of the tasks presented social dilemmas to the children verbally, while the other two tasks were presented through audio-visual video clips; the different demands of these mediums allowed a comparison of the multiple components involved in real-world social interactions. Group comparisons indicated that children with ADHD performed more poorly than typically developing children on all three social problem solving tasks. In particular, children with ADHD had impaired understanding of characters’ emotions in the social dilemmas. Furthermore, parents rated children with ADHD as having more social problems and fewer social skills compared to the control group. Children with ADHD were also impaired in their pragmatic language abilities, theory of mind skills, and working memory abilities compared to their typically developing peers.
Given the significant differences between groups in their social problem solving abilities, we investigated potential mechanisms that may contribute to children’s social problem solving performance. Regression analyses indicated that pragmatic language skills predicted children’s social problem solving abilities beyond symptoms of ADHD. Additional mechanisms, such as working memory skills and theory of mind, appeared to be contributing to children’s social problem solving through their language abilities.
Exploratory regression analyses were also conducted to investigate potential mechanisms underlying parent ratings of children’s social functioning. Surprisingly, children’ social problem solving abilities were not strongly associated with parent ratings of children’s social functioning. Children’s symptoms of ADHD, their working memory skills, and language abilities all contributed to parent ratings of children’s social functioning. The results of the research suggested that there is a difference in the variables contributing to children’s cognitive social problem solving abilities compared to parent ratings of children’s social functioning. Children’s symptoms of ADHD, particularly severity of hyperactivity/impulsivity, and executive functioning skills played an important role in explaining variance in parent ratings of children’s social functioning, but were less important in explaining children’s cognitive social problem solving abilities. The language skills of children with ADHD appear to be an important contributor to both their cognitive understanding of social problems and their social functioning
Seabed pockmarks and subsurface fluid migration at multiple scales: Investigations using hydroacoustic and seismic data
No full textFluid migration from deep sedimentary basins towards Earth’s surface has various implications for hydrocarbon accumulations and influences slope stability, climate and ecological systems. Fluids seeping from the seafloor can give insight into deep crustal and tectonic processes and can significantly change the seafloor morphology as well as the chemical composition of the overlying ocean.
The timing of fluid migration in many sedimentary basins is often poorly constrained and the composition of fluids involved in the formation of migration pathways and seafloor venting structures is difficult to determine. Likewise, the effect of upward migrating fluids on the surrounding host sediments and their diagenetic processes is an under-investigated field. Although gas bubbles venting from the seafloor are well constrained and easily identified in hydroacoustic data, the detection of submarine groundwater discharge sites often relies on oral traditions and visual reports from fishermen who recognize anomalies (schlieren/streaks) on the sea-surface. In many regions (e.g. organic muds, hydrothermal fields), submarine groundwater discharge is accompanied by gas venting. However, the processes involved in simultaneous gas and water discharge, as well as their relative contributions to geomorphological structures, are generally not well understood.
Decreasing acoustic resolution with depth requires a multi-scale approach to gain a better understanding of the various fluids and migration processes involved at different depths. Using different hydroacoustic systems and frequencies, I examine fluid migration pathways in the subsurface and various morphological expressions that seeping fluids create on the surface during discharge. I integrate well logs, surface sediment grab samples, as well as sediment cores and geochemical porewater analysis to validate and ground truth the hydroacoustic and seismic observations. I apply these methods to datasets from two study areas: the Canterbury Basin, east of New Zealand’s South Island, and Eckernförde Bay in the Baltic Sea of Northern Germany.
In the Canterbury Basin, my analyses reveal a wide variety of subsurface migration pathways as well as surface structures related to fluid migration. I show how diagenetic processes of fine-grained sediments are dramatically changed in a 2 km radial distance around a conduit feeding a sediment volcano. This change manifests itself in the suppression of polygonal faulting, and is a result of either 1) a significant change in differential stress induced by buoyant upward migrating fluids that accumulate at depth, or 2) permeable stringers intruding into the surroundings of the feeding pipe and therefore facilitating the dewatering of the enclosing sediments. On the surface of the Oligocene Marshall Paraconformity, I find pockmarks as well as discharged sediments emplaced by sediment volcanism. While the pockmarks appear to be related to dewatering mechanisms of the underlying strata, the sediments emplaced on the same surface seem to be sourced from Cretaceous strata. Several sediment intrusions into Paleocene sediments are similarly sourced from Cretaceous lithologies and affect the overlying fault orientation.
Also, I find that recent fluid migration pathways are likely to be responsible for shallow gas accumulations on the continental slope of the Canterbury Basin. On the present-day seafloor, there are numerous pockmarks on the shelf and slope that have been modified by currents. The pockmarks form as a result of gas and/or groundwater seepage, but the contribution of gas versus offshore groundwater could not be unequivocally determined for the Canterbury Basin.
In Eckernförde Bay, in contrast to the Canterbury Basin, I was able to hydroacoustically distinguish areas of submarine groundwater discharge and areas additionally affected by gas seepage. Using very high-resolution multibeam data and sub-bottom profiling, I observed and characterised a new type of pockmark that is associated with submarine groundwater and gas discharge. I determined that, in gaseous muddy sediments, submarine groundwater discharge results in unusually consistent and exceptionally shallow free gas that can even be detected with high-frequency 400 kHz multibeam systems
DNA methylation in pre-eclampsia: methodologies and analytics
No full textThe placenta is a heterogeneous and multifunctional organ that grows and adapts according to increasing and fluctuating fetal demands in the intrauterine environment. As expected, the placenta plays a major role in pregnancy outcomes. Pre-eclampsia (PET) is one of the most common adverse pregnancy complications, that occurs in approximately 10% of pregnancies worldwide, yet the underlying cause is unknown. Unfortunately, the only known cure is delivery of the fetus and placenta. Little progress has been made on treatment and management of pre-eclampsia because the condition usually remains undiagnosed until after the 24th week of gestation, by which time the condition is well established. The use of biomarkers to accurately identify women with an increased risk of developing pre-eclampsia would be a major step forward in antenatal care.
Over the last decade, a growing number of studies have sought to define a correlation between epigenetic modifications and the development of pre-eclampsia. However, reported results have been inconsistent. This may reflect small sample numbers and a lack of standardisation of analytical methods. The lack of independent replication of key findings constrains our understanding of the biological role of DNA methylation in pre-eclampsia. Over the past few years, the field has become focused on using the epigenetic features of cell-free fetal DNA (cff-DNA) to create a universal ‘fetal’ marker in maternal plasma. The molecular analysis of cff-DNA may therefore lead to new non-invasive approaches for assessing placental (fetal) health and detecting pregnancy complications.
This PhD project seeks to identify a panel of candidate epigenetic biomarkers for pre-eclampsia that can ultimately be detected in cff-DNA in maternal plasma. The work presented in this thesis has three main objectives. The first objective is to discover and validate epigenetic (DNA methylation) differences in pre-eclamptic placentas by performing and analysing reduced representation bisulfite sequencing (RRBS) data and publicly available 450K data. The second objective was to establish a targeted bisulfite sequencing protocol for genomic DNA and cf-DNA. To do this, I used the Illumina MiSeq platform to validate differentially methylated candidates that were generated from the discovery phase (objective 1). I also used MiSeq sequencing to quantify placental methylation of cf-DNA in pregnant maternal plasma. Targeted bisulfite sequencing generates a large amount of high quality and high coverage sequence data. Thus, the third objective of this PhD project was to develop a bioinformatic pipeline for the analysis of high-throughput targeted bisulfite sequencing (MiSeq) data.
In the discovery phase of this project, methylation on a genome-wide scale at single-nucleotide resolution was conducted to screen for methylation biomarkers, with 15 selected placental samples(9 PET and 6 CTL). We identified several genomic locations where variation in methylation between pre-eclamptic tissues and unaffected controls could be associated with pre-eclampsia. Interestingly, among the differentially methylated genes, there was enrichment for a set of genes that have been found in cancer studies to function as tumour suppressor genes. We propose that these loci are epigenetically regulated and may be functionally relevant in the pathophysiology of pre-eclampsia. Complementary to the RRBS analysis, in-silico analysis of published 450K DNA methylation data identified several differentially methylated positions (DMPs). Among those loci identified by discovery analysis, 28 were selected for independent validation. Targeted high-throughput bisulfite sequencing was chosen as it provides a more focused analysis of the selected regions. Our data demonstrated correlation between the discovery tools (RRBS and 450K) and the validation technology (targeted bisulfite sequencing). Our validation analysis confirmed three differentially methylated fragments from RRBS analysis (PCDHB17, GPR123, XRN2), two differentially methylated cytosines (AL353597.1, TBX15), and four differentially methylated positions, identified by in-silico analysis, in an independent cohort. We demonstrated the targeted bisulfite sequencing approach to be a powerful validation method on predefined regions and surrounding CpG sites to confirm aberrant methylation in the pre-eclamptic methylome. Since all targets were amplified and sequences as a multiplexed pool, this method proved efficient in reducing the cost and time while enhancing the coverage. Our results also demonstrate the powerful of bioinformatics pipeline developed for downstream analysis.
In the cff-DNA part of this study, I selected five epigenetic marker genes from the literature that displayed opposite and extreme methylation differences between the placenta and somatic tissues. I then established a targeted bisulfite sequencing (Illumina MiSeq) protocol to quantify the methylation of the epigenetic marker genes (RASSF1A, SERPINB5, AIRE58, AIREA1 and PSMB5) in plasma samples taken from healthy pregnant and non-pregnant individuals. By quantifying the methylation of these marker genes, I was able to determine the proportion of placental DNA in maternal blood. Isolation and quantification of cff-DNA is a critical step in developing non-invasive screening strategies for the identification of epigenetic biomarkers in maternal plasma. By knowing the exact contribution of placental DNA in maternal plasma, a future project will be able to continue the second phase and ultimate aim of this project which is the quantification of methylation biomarkers in maternal plasma as a predictor for pregnancy complications, particularly, pre-eclampsia. The study also demonstrated a clear correlation between increasing cff-DNA and increasing gestational age.
To the best of this author’s knowledge, this study is the first to report the validation of RRBS and 450K-derived candidate biomarkers using Illumina MiSeq. Moreover, I believe it is the first to establish cff-DNA quantification by targeted bisulfite sequencing. Further optimisation is warranted before confirming the utility as a clinical biomarker. Genomic data sets and the rapidly expanding bioinformatic tools to analyse them provide a unique opportunity to quickly evaluate biomarker concepts with minimal cost and identify promising markers for prospective validation on precious clinical specimens
Estimating population density and habitat selection of rats (Rattus spp.) and abundance of birds on the Otago Peninsula
No full textThe introduction of rats (Rattus spp.) and conversion of native forest and scrub have had a devastating effect on the biodiversity of New Zealand’s fauna and flora, threatening many native bird species with extinction. The Otago Peninsula is an area of land characterised by its fragmented landscape and presence of introduced mammalian predators, including rats.
This study aimed to estimate the abundance of rats at three sites of fragmented vegetation on the Otago Peninsula using spatially explicit capture-recapture (SECR) and noninvasive genetic sampling. Hair-snag tube grids and microsatellite genotyping were used in an attempt to identify individual rats and estimate population density. The results remain inconclusive in terms of estimating rat population density due to the high degree of genotyping error and inability to identify recaptures. As such, a simple estimate of rat population density at each site was obtained through the inclusion of a boundary strip around the hair-snag tube grid and using a minimum number alive of rats at each site. The boundary strip was calculated to establish an effective trap area to reduce the edge effect in the density calculation. The highest density of rats was found to be at Okia, with approximately 0.9 rats/ha. Leith Walk had a density of 0.7 rats ha-1, while Hooper’s Inlet had an estimated density of 0.3 rats ha-1.
In addition to this, a habitat selection analysis was also undertaken. Number of tiers was used as an index of vegetation complexity and was found to be positively associated with probability of rat presence (p=0.020), as was percentage groundcover (p=0.006). While rat species could not be discerned from genotyping, these results suggest the species detected was likely ship rat (Rattus rattus). Distance to coast, presence or absence of fruiting trees, distance to freshwater, maximum canopy height, and site were all found to be nonsignificant variables in predicting rat presence.
A tracking tunnel line at each site also gave a rough index of rat abundance. Very low tracking rates of 10% at Hooper’s Inlet and Okia confirmed rat presence in the area. No rat tracks were recorded at Leith Walk. There was no correlation between rat tracking rates and the number of rats detected from the hair-snag tube grids. Mice (Mus musculus) were frequently detected using both sampling methods, with tracking rates of 100% at all three sites.
Using 5-minute bird counts 24 bird species were counted across the same three sites in which the rat sampling was conducted. The most abundant bird species were bellbird (Anthornis melanura) at Leith Walk, and goldfinch (Carduelis carduelis) at Hooper’s Inlet and Okia. Distance sampling allowed for analysis of ten of the most abundant species in DISTANCE software to estimate population density of these species. Fantails (Rhipidura fuliginosa) had the highest population density among bird species at Leith Walk (1.043 ha-1), whereas silvereyes (Zosterops lateralis lateralis) had the highest estimated densities of species at both Leith Walk (0.175 ha-1) and Okia (0.163 ha-1). These results provide a foundation for further study of rat density estimations and bird abundance on the Otago Peninsula, and can be used as a baseline when evaluating the impact of future rat eradication, which has been proposed to meet the goal of a Predator Free Peninsula by 2050
Medicine amongst the Maoris in ancient and modern times
No full textMy excuse for attempting this thesis is firstly, that I am a graduate in medicine of the University New Zealand and secondly, that my mother was a Maori.
It seems to me that with a young university such as that of New Zealand, without the facilities for research work provided by older and richer homes of learning, the scope for original work, which it is the duty of every University to encourage and foster, is somewhat limited. In the philology, history and ethnology of the Polynesian Race, however, is provided a wide field for research work which it is the bounden duty of this University to explore and lead the way. As an obligation to my 'alma mater' I take up the subject nearest to my family - medicine amongst the Maoris, in ancient and modern times.
As another reason, I have the honour through my mother of belonging to the Maori race. As a result of four years work amongst them as an officer of Health, I am much struck by the different view point with which the two races, European and Maori, approach the subject of disease. As a member of the Race I am perhaps enabled to understand my mother's people more intimately than the more progressive but some what forgetful Anglo-Saxon. My experience of Maori ideas and customs dates from beyond the time of graduation in medicine. In childhood's days, I experienced the bitter taste of the decoction prepared from phorium tenex and I heard around me the whispered diagnosis of 'makutu' and 'mate Maori'. Constantly throughout youth and early manhood, I have seen the European doctor wax impatient with what he terms prejudices or superstitions which retard or prevent the recovery of Maori patients. I have understood and sympathised with him. At the same time, with the priveledge of the half-breed inheriting the blood and ideas of both races I have been able to detach myself from European thought and look at the question of disease from my Maori countryman's viewpoint. I understood the burden of the neolithic man's fears and I symathise with him more deeply still. There are deep holes in the Urenui river which flows through our tribal territory wherein, so my Maori mother taught me, dwelt 'taniwhas' or 'dragons of slime' who destroyed the transgressor of the multitude of Maori laws and observances. Years of College and University education, combined with the unbelief inherited from a European father, have not been able to suppress the involuntary shudder and contraction of the erector pilae which the suggestion of bathing in those dark holes gives rise to. We inherit our fears in our blood, we imbibe them at our mother's breast. The schools and teaching of a father appeal to us as we grow older. We subject customs and faiths to the light of comparative criticism and we ridicule the ideas of more primitive races as absurd. But in times of stress, despondency and lowered vitality, there is a tendency to revert to the mother's fears which slumber within beneath the veneer of civilisation. How much more so in the case of the full Maori who has not had the advantage of even primary education! Clodd says, "In structure and inherited tendencies each of us is recent". The Maori has not been civilised for a century yet. As a duty to my kin, I have attempted to put on record their view of disease, in the hope that though anthropologist's and others have done so much in collecting the ideas and customs of races on a lower culture stage, this thesis may serve as a small contribution to ethnology. [Extract from Introduction
Modulation of interhemispheric inhibition and its effect on stroke recovery in the rat
No full textRationale: Residual disability following stroke is a significant challenge for patients and the healthcare system, both in New Zealand and worldwide. Poor recovery from motor cortex (M1) stroke has been associated with an increase in interhemispheric inhibition (IHI) initiated by the unlesioned cortex (Murase, Duque, Mazzocchio, & Cohen, 2004). Previously we showed using intracellular recordings from single neurons that intermittent theta-burst stimulation (iTBS; bursts of three pulses at 50 Hz at 5 Hz) delivered to the contralateral M1 acutely reduced IHI in normal rats (Barry, Boddington, Igelström, et al., 2014). Additionally, this stimulation improved motor recovery sub acutely following stroke (Boddington, Gray, Schulz, & Reynolds, 2020). In the present study we aimed to record IHI changes in the freely moving, stroke affected rat and measure any association with behavioural impairment. We also aimed to determine if iTBS could modify IHI and improve behaviour.
Method: A method of measuring IHI in rats using EEG recording techniques was first developed. Second, to study effects of stroke and iTBS, lesions were induced by injecting endothelin-1 into M1 and dorsal sub-cortical regions and electrodes implanted to measure IHI in freely moving animals. Sham stimulation or iTBS was delivered at low intensity to the contralesional cortex for 15 days, followed by three weeks of no stimulation. Behaviour was recorded throughout, using grid walking and pasta handling tasks.
Results: Baseline IHI was 19.1% ± 4.4 and was increased to 34.3% ± 5.5 one week following lesion induction (mean difference: 15.2 ± 6.0, p=0.033). In addition, increased IHI was weakly associated with worsened motor performance (R2: 0.11, p<0.005). Comparing iTBS and sham stimulated animals, in the final week of the study, iTBS animals showed a 54% ± 8.7 functional improvement in foot faults from their post stroke grid walking impairment, compared to only 15% ± 11 in the sham group; mixed effects model: p<0.05. The pasta handling task also revealed significantly greater improvement following iTBS (improvement of 56% ± 17) compared to sham (14% ± 7.4): p<0.05. In addition, delivery of iTBS reduced IHI to a greater degree than the spontaneous reduction observed in the sham group (linear mixed model: p<0.05), both in the weeks during and following stimulation.
Conclusion: Our results show an association between IHI and behavioural recovery in the early stages of stroke recovery. They also show that IHI is reduced, and behavioural recovery improved by low intensity, contralesional iTBS