A longitudinal study of cortical EEG to olfactory stimulation : involving inter- and intra- subjective responses

This thesis forms the largest and most systematic study of the topographical EEG response to odour. The evolutionary history of the olfactory sense is briefly presented and its relevance to humans in the present day is considered. This thesis examines the information processing that occurs in this sensory system. The type of processing that the olfactory system utilises at each anatomical stage is discussed. The character of olfactory information that may reach neocortical levels in humans is considered in the light of the technology available to detect such information. The neurogenesis of the EEG is considered, together with questions concerning its postulated functional significance. The empirical work carried out uses the most advanced methodology for this type of study. The large number of odourants and subjects, combined with the longitudinal element, make this the most ambitious study of this nature undertaken. The issues surrounding the analysis and interpretation of EEG data arc fully discussed and the impact of Chaos theory is considered. Five major analysis techniques were used on the data collected, but largely negative findings arc reported. The reasons for the failure of this experimental paradigm are discussed and improvements arc suggested for future work. The major contribution of this thesis lies in its exploration of the assumptions of the EEG response to odour. The thesis notes the lack of a conceptual framework that has hindered progress in the area of the "odour" EEG. Recent developments in neural network theory and Chaos theory are highlighted as possible alternative approaches to the modelling and understanding of the olfactory system

Neural processes underpinning episodic memory

Episodic memory is the memory for our personal past experiences. Although numerous functional magnetic resonance imaging (fMRI) studies investigating its neural basis have revealed a consistent and distributed network of associated brain regions, surprisingly little is known about the contributions individual brain areas make to the recollective experience. In this thesis I address this fundamental issue by employing a range of different experimental techniques including neuropsychological testing, virtual reality environments, whole brain and high spatial resolution fMRI, and multivariate pattern analysis. Episodic memory recall is widely agreed to be a reconstructive process, one that is known to be critically reliant on the hippocampus. I therefore hypothesised that the same neural machinery responsible for reconstruction might also support ‘constructive’ cognitive functions such as imagination. To test this proposal, patients with focal damage to the hippocampus bilaterally were asked to imagine new experiences and were found to be impaired relative to matched control participants. Moreover, driving this deficit was a lack of spatial coherence in their imagined experiences, pointing to a role for the hippocampus in binding together the disparate elements of a scene. A subsequent fMRI study involving healthy participants compared the recall of real memories with the construction of imaginary memories. This revealed a fronto-temporo-parietal network in common to both tasks that included the hippocampus, ventromedial prefrontal, retrosplenial and parietal cortices. Based on these results I advanced the notion that this network might support the process of ‘scene construction’, defined as the generation and maintenance of a complex and coherent spatial context. Furthermore, I argued that this scene construction network might underpin other important cognitive functions besides episodic memory and imagination, such as navigation and thinking about the future. It is has been proposed that spatial context may act as the scaffold around which episodic memories are built. Given the hippocampus appears to play a critical role in imagination by supporting the creation of a rich coherent spatial scene, I sought to explore the nature of this hippocampal spatial code in a novel way. By combining high spatial resolution fMRI with multivariate pattern analysis techniques it proved possible to accurately determine where a subject was located in a virtual reality environment based solely on the pattern of activity across hippocampal voxels. For this to have been possible, the hippocampal population code must be large and non-uniform. I then extended these techniques to the domain of episodic memory by showing that individual memories could be accurately decoded from the pattern of activity across hippocampal voxels, thus identifying individual memory traces. I consider these findings together with other recent advances in the episodic memory field, and present a new perspective on the role of the hippocampus in episodic recollection. I discuss how this new (and preliminary) framework compares with current prevailing theories of hippocampal function, and suggest how it might account for some previously contradictory data

Insect neuroethology of reinforcement learning

Historically, reinforcement learning is a branch of machine learning founded on observations of how animals learn. This involved collaboration between the fields of biology and artificial intelligence that was beneficial to both fields, creating smarter artificial agents and improving the understanding of how biological systems function. The evolution of reinforcement learning during the past few years was rapid but substantially diverged from providing insights into how biological systems work, opening a gap between reinforcement learning and biology. In an attempt to close this gap, this thesis studied the insect neuroethology of reinforcement learning, that is, the neural circuits that underlie reinforcement-learning-related behaviours in insects. The goal was to extract a biologically plausible plasticity function from insect-neuronal data, use this to explain biological findings and compare it to more standard reinforcement learning models. Consequently, a novel dopaminergic plasticity rule was developed to approximate the function of dopamine as the plasticity mechanism between neurons in the insect brain. This allowed a range of observed learning phenomena to happen in parallel, like memory depression, potentiation, recovery, and saturation. In addition, by using anatomical data of connections between neurons in the mushroom body neuropils of the insect brain, the neural incentive circuit of dopaminergic and output neurons was also explored. This, together with the dopaminergic plasticity rule, allowed for dynamic collaboration amongst parallel memory functions, such as acquisition, transfer, and forgetting. When tested on olfactory conditioning paradigms, the model reproduced the observed changes in the activity of the identified neurons in fruit flies. It also replicated the observed behaviour of the animals and it allowed for flexible behavioural control. Inspired by the visual navigation system of desert ants, the model was further challenged in the visual place recognition task. Although a relatively simple encoding of the olfactory information was sufficient to explain odour learning, a more sophisticated encoding of the visual input was required to increase the separability among the visual inputs and enable visual place recognition. Signal whitening and sparse combinatorial encoding were sufficient to boost the performance of the system in this task. The incentive circuit enabled the encoding of increasing familiarity along a known route, which dropped proportionally to the distance of the animal from that route. Finally, the proposed model was challenged in delayed reinforcement tasks, suggesting that it might take the role of an adaptive critic in the context of reinforcement learning

O efeito do dimorfismo sexual e da confiabilidade percebida nas preferências de atratividade: uma perspetiva evolutiva

Doutoramento em PsicologiaO trabalho apresentado nesta tese teve como principal objetivo investigar o impacto do dimorfismo sexual e da confiabilidade percebida na atratividade humana, considerando os pressupostos da Psicologia Evolutiva. O Capitulo 1 apresenta uma revisão da literatura relevante na área, apresentando as principais teorias relativas ao que determina a atração humana, os fatores que contribuem para uma aparência atraente e os aspetos subjacentes às diferenças individuais na escolha de parceiro. O Capítulo 2 descreve um estudo de potenciais evocados, que pretendeu investigar os correlatos neurofisiológicos da perceção da forma sexualmente dimorfa das faces. Faces que variaram nas características de masculinidade / feminilidade induziram respostas diferenciadas nos componentes P2, EPN e LPP. Modulações específicas aquando da apresentação de faces do sexo oposto foram visíveis em P2 e EPN. Além disso, diferenças entre sexos, tanto nos componentes precoces como nos tardios, revelaram diferenças no processamento visual que não foram evidentes nos resultados comportamentais. O Capítulo 3 apresenta três experiências, nas quais investigamos a influência da cor da pele sexualmente dimorfa, para além da forma, na atratividade facial. Quando lhes foi permitido que manipulassem faces de homens com o objetivo de as tornar o mais atraentes possível, as participantes do sexo feminino aumentaram a masculinidade da cor da pele e diminuíram a masculinidade da forma. A cor da pele é, assim, proposta como uma característica sexualmente dimorfa que desempenha um papel importante nas perceções de atratividade ao comunicar o valor como parceiro. O Capítulo 4 investiga a possibilidade das mulheres preferirem odores de homens com uma cor de pele mais masculina. Participantes do sexo feminino cheiram e avaliaram os odores de vários dadores do sexo masculino, e os resultados mostraram que os odores dos dadores com uma cor de pele mais masculina foram considerados mais apelativos (“likeable”) e saudáveis, mas menos viris (“maleness”). Os resultados foram discutidos considerando o efeito das estratégias reprodutivas com a influência simultânea de estereótipos cognitivos. No Capitulo 5, explorou-se o papel da confiabilidade percebida na atratividade, simultaneamente com possíveis diferenças individuais com base nos níveis de ansiedade de interação social. Ao permitir que participantes de ambos os sexos manipulassem faces, tal como no Capitulo 3, tanto os participantes do sexo masculino como as participantes do sexo feminino escolheram aumentar a confiabilidade percebida para aumentar a atratividade, especialmente quando consideraram relações a longo-prazo. Além disso, a ansiedade de interação social correlacionou-se positivamente com a preferência por confiabilidade em faces, possivelmente indicando uma atração aumentada por parceiros seguros e confiáveis em indivíduos ansiosos. Finalmente, o Capitulo 6 sumariza os principais resultados, discute as suas possíveis implicações teóricas e apresenta várias propostas de estudos futuros.The work presented in this thesis aimed to investigate the impact of both sexual dimorphism and perceived trustworthiness on human attractiveness, considering the perspective of Evolutionary Psychology. Chapter 1 reviews the relevant literature in the field, acknowledging the main theories about what determines human attraction, the factors that contribute to an attractive appearance and the sources of individual differences in mate choice. Chapter 2 describes an ERP study that aimed to investigate the neurophysiological correlates of the perception of sexually dimorphic shape in faces. Faces that varied in masculinity/ femininity features elicited differentiated responses in P2, EPN, and LPP components. Faces of the opposite sex of participants elicited specific modulations on the P2 and EPN. Also, sex differences in both early, and later components revealed differences in visual processing that were not evident in behavioural results. Chapter 3 presents three experiments, in which we investigated the influence of sexually dimorphic skin colour, in addition to shape, on the perception of facial attractiveness. When allowed to manipulate male faces to make them as attractive as possible, female participants increased skin colour masculinity and decreased shape masculinity. Skin colour is proposed as a sexually dimorphic feature that plays a role in attractiveness perception by advertising mate value. Chapter 4 investigates the possibility of women preferring the odours of men with a more masculine skin colour. Female participants were asked to smell and rate the odours of several male donors, and results showed that the odours of donors with a more masculine skin colour were considered as more likeable and healthy, but scored lower in maleness. The results were discussed taking into account the effect of reproductive strategies with the simultaneous influence of cognitive stereotypes. In Chapter 5, the role of facial features of perceived trustworthiness on attractiveness was explored, along with the effect of individual differences in social interaction anxiety levels. By allowing participants of both sexes to manipulate faces as in Chapter 3, both males and females chose to increase perceived trustworthiness to rise facial attractiveness, especially when considering long-term relationships. Moreover, social interaction anxiety correlated positively with the preference for facial trustworthiness, possibly indicating an increased attraction for trustworthy secure mates in anxious individuals. Finally, Chapter 6 summarises the main findings, discusses their possible theoretical implications and presents some proposals for future studies

Host plant finding by Acraea acerata Hew. (Lepidoptera: Nymphalidae), the sweet potato butterfly: implications for pest management

Phytophagous insects such as Lepidopteran species utilise both olfactory and visual cues to locate their host-plants used as mating or oviposition sites, shelter or food. Larvae of Acraea aceratafeed on sweet potato plant leaves causing more that 50 % loss of sweet potato tuber yield in some East African countries. Attempting to elaborate a management strategy to control A. aceratasuitable to a tropical resource- poor farming system, it was essential to investigate how the butterfly finds its host- plants. The results of a wind tunnel bioassay using glass-screened, muslin-screened and non-screened sweet potato plants suggested that sweet potato plant volatiles play an important role in attracting A. aceratato its host-plant. This was supported by both the distance moved by female A. aceratatowards muslin-screened plants (olfactory cues) and the percentage of butterflies which landed on the screen. Visual stimuli seemed to have a negative effect. The attractiveness of sweet potato plant volatiles to A. aceratawas later confirmed by the use of volatiles collected by headspace entrainment from sweet potato plantsThe main components of sweet potato plant volatiles were tentatively identified by GC-MS (Gas Chromatography coupled with Mass Spectrometry) analysis and electrophysiological responses were recorded for some of them. Compared to ethylbenzene, 3-carene and (-) trans-caryophyllene, 3-hexen-l-ol,(Z), a general green leaf alcohol, elicited far more substantial EAG (electroantennogram) responses in A.acerata.This result suggested that A. aceratamight well respond to a specific blend of volatiles made up of the different chemical components of sweet potato plant volatiles instead of one or two specific chemical components.Considering the important role of sweet potato plant volatiles in attracting A. acerata,a number of plants reported to be repellent to herbivorous insects were mixed with sweet potato plants and screened for repelling/disorienting of female A. aceratain olfactometer and wind tunnel bioassays. Two plant mixtures with opposite effects on the response of A. aceratato their volatiles were identified: sweet potato + Desmodiumplant volatiles were found to be more attractive to the butterfly than sweet potato plant volatiles alone, and sweet potato + onion plant volatiles which reduced considerably the attractiveness of sweet potato plant volatiles to A. acerata.As the trichomes of Desmodiumplants were reported to trap insects, a ‘push-pull’ management strategy for A. aceratainvolving the two intercrops was suggested: the intercrop sweet potato + onion plants would ‘push’ away ovipositing A. aceratawhereas the intercrop sweet potato + Desmodiumplants would attract the butterflies which would be trapped by Desmodiumtrichomes. The results of a preliminary field experiment carried out in Uganda suggested that the intercrop sweet potato + onion plants had a negative effect on the number of egg batches laid by A. acerataon sweet potato plants. There is, therefore, a need for comprehensive field experimentation of the whole strategy to validate these laboratory and field experimental findings

Cognitive processing of food rewards

AbstractCues associated with tasty foods, such as their smell or taste, are strong motivators of eating, but the power of food cues on behaviour varies from moment to moment and from person to person. Variation in the rewarding value of a food with metabolic state explains why food cues are more attractive when hungry. However, cognitive processes are also important determinants of our responses to food cues. An urge to consume a tempting food may be resisted if, for example, a person has a longer term goal of weight loss. There is also evidence that responses to food cues can be facilitated or inhibited by memory processes. The aim of this review is to add to the literature on cognitive control of eating by reviewing recent evidence on the influence of working memory and episodic memory processes on responses to food cues. It is argued that processing of food information in working memory affects how much attention is paid to food cues in the environment and promotes the motivation to seek out food in the absence of direct contact with food cues. It is further argued that memories of specific recent eating episodes play an important role in directing food choices and influencing when and how much we eat. However, these memory processes are prone to disruption. When this happens, eating behaviour may become more cue-driven and less flexible. In the modern food environment, disruption of cognitive processing of food reward cues may lead to overconsumption and obesity

Development of medical point-of-care applications for renal medicine and tuberculosis based on electronic nose technology

Introduction: Current clinical diagnostics are based on biochemical, immunological or microbiological methods. However, these methods are operator dependent, time consuming, expensive and require special skills, and are therefore not suitable for point-of-care testing. Recent developments in gas-sensing technology and pattern recognition methods make electronic nose technology an interesting alternative for medical point-of-care devices. Methods: We applied a gas sensor array based on 14 conducting polymers to monitor haemodialysis in vitro and to detect pulmonary tuberculosis in both culture and sputum. Results and discussion: The electronic nose is able to distinguish between control blood and “uraemic” blood. Furthermore, the gas sensor array is not only capable of discriminating pre- from post-dialysis blood (97% accuracy) but also can follow the volatile shift occurring during a single haemodialysis session. The electronic nose can be used for both dialysate side and blood-side monitoring of haemodialysis. The pattern observed for post- and pre-dialysis blood might reflect the health status of the patients and can therefore be related to the long-term outcome. Furthermore, the gas sensor array was also able to discriminate between Mycobacterium spp. and other lung pathogens such as Pseudomonas aeruginosa. More importantly the gas sensor array was capable of resolving different Mycobacterium spp. such as Mycobacterium tuberculosis, M. scrofulaceum, and M. avium in both liquid culture and spiked sputum samples. The detection limit for M. tuberculosis in both sputum and liquid culture is 1 x 104 mycobacteria ml-1 and therefore partially fulfils the requirement set by the WHO. The gas sensor array was able to detect culture proven TB with a sensitivity of 89% and a specificity of 91%. Conclusions: In conclusion, this study has shown the ability of an electronic nose as a point-of-care device in these areas.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Assessing the effect of people's behaviour on energy consumption in buildings

Energy consumption in the residential sector has become increasingly important. This is all the more significant considering the pandemic, when people spent more time at home. In order to achieve the zero-carbon target of the Paris Agreement of which the UK is a part, there is a drive to insulate buildings, on the assumption that the more insulated a building is, the more efficient it will perform. In this study, the author examines the effect of peoples' behaviour, particularly window opening, as a behavioural pattern of the occupants and examines impact of occupant behaviour on the energy consumption of residential buildings in the UK. To identify the key factors that influence occupant behaviour, thermal imaging of residential buildings across Nottingham was done, followed by survey with questions regarding window opening behaviour of the participants. This was followed by the analysis of energy usage in Social Housing. Temperature data collected for a period of 14 months, from 17 houses, were analysed and the energy demand was calculated. Findings show that energy efficiency of a building holds an explicate relationship with the behaviour of occupants in the buildings, regardless of the building insulation properties. A highly insulated building could consume as much energy as a badly insulated house, due to people's behaviour. There was empirical evidence that for a well-insulated house with window open, the heating time increases by a factor of 1.6 when compared to similar insulated house with window closed. Hence the assumption that the more the insulation, the more the energy efficiency, might not be true. Findings also show that people's behaviour could reduce the effect of insulation. So, what theoretically is a well-insulated building might behave like a badly insulated house in terms of energy efficiency, depending on the behaviour of occupants. Thermal imaging is a helpful tool in visualising the impact of window opening and can be used to make occupants aware of the effect of their behaviour. ANN feed forward neural network model to predict the window opening behaviour based on the room temperature, radiator temperature and outside ambient temperature was developed. Energy costs of highly insulated and window open house defers from that of badly insulated and window open house only by 2%, while there is a difference of 10% between highly insulated and window open house and highly insulated and window closed house, showing that a well insulated house with window open behaves in a similar way to a poorly insulated house. ANN feed forward neural network model to predict the window opening behaviour based on the room temperature, radiator temperature and outside ambient temperature was developed. The model predicted window opening with 98.8% accuracy for well insulated window closed house and 92% accuracy for well insulated window open house. The findings suggest that people's behaviour could reduce the effect of insulation in residential buildings

Afferent connectivity of the Zebrafish Habenulae

The habenular nuclei are bilateral nuclei located in the dorsal diencephalon. The habenulae and their associated circuitry, the dorsal diencephalic conduction system (DDC) are conserved across all vertebrates. As part of the DDC, the habenulae act as a major relay station between forebrain regions and monoaminergic centres in the midbrain. Zebrafish habenulae display prominent neuroanatomical asymmetries and asymmetries in circuit microarchitecture have been described in both afferent and efferent projections. In this study, I characterise two of the main forebrain afferent nuclei of the habenula: the ventral entopeduncular nucleus (vENT) and nucleus rostrolateralis (RL). Through fate mapping, transgenic line analysis and gene expression studies, I show that the vENT is diencephalic in origin and extends into the telencephalon. vENT is the main afferent telencephalic nucleus of the habenula in zebrafish and is homologous to the entopeduncular nucleus in mammals. I show the afferent nucleus conveying visual information to the habenula is RL. RL is prethalamic and retina and tectal recipient. RL and parapineal afferents asymmetrically innervate the left dorsal habenula. Using parapineal ablations and mutants in which habenula asymmetry is disrupted, I show that RL asymmetric innervation is not parapineal dependent. RL afferents arborise close to differentiating “left sided” habenula neuronal sub-types. Previous studies in zebrafish claim the habenula receives pallial innervation. Using a pan-pallial enhancer -trap line, Tg(gata2:EGFP)bi105, I show that this is not the case. I mapped the insertion to egr3, a gene linked to schizophrenia and important for hippocampal learning and memory and characterise the expression pattern of this line at larval stages. To look at the morphologies and projection patterns of individual habenula afferent and pallial neurons I have adapted a method for switching EGFP to Gal4 in transgenic lines using CRISPR/Cas9. The neuroanatomical characterisation of these habenulo-afferent areas lays important groundwork for further functional characterisation of this important circuit