Cortical - Basal Ganglia Circuits: Control of Behaviour and Alcohol Misuse

Highly organised and differentiated neural circuits form and unite to link the cortex with the basal ganglia and thalamus to mediate movement, cognition and behaviour. Previous assertions that the basal ganglia primarily acted to filter cortical information to facilitate motor outputs only have since given way to an understanding of the basal ganglia as a relay and gating structure with functionally and structurally segregated inputs, functions and outputs. Thus, cortical – basal ganglia circuits can be segregated into three broadly separable functional domains mediating motor (primary and supplementary motor cortex (SMA) and putamen), cognitive (dorsolateral prefrontal cortex (dlPFC) and caudate), and limbic (ventromedial prefrontal cortex and ventral striatum (VS)) processes. In addition, cognitive and behavioural programs that pass through the cortical – basal ganglia circuitry can be subject to filtering by the subthalamic nucleus (STN), which receives direct projections from the cortex. This work first demonstrated the functional organisation of segregated intrinsic cortical – basal ganglia circuits in humans, alongside a detailed map of functional subzones within STN, a small and technically inaccessible midbrain structure. The behavioural relevance of the defined cortical – basal ganglia circuits was investigated by examining the cognitive constructs of impulsivity and compulsivity. Waiting impulsivity, a tendency towards rapid premature responses that has been associated with compulsive drug use, was associated with connectivity between limbic regions including subgenual anterior cingulate cortex, VS and STN. However, motor impulsivity, in the form of stopping ability, was associated with motoric regions including pre-SMA and STN. Compulsivity was captured as deficits in: reversal learning, implicating lateral orbitofrontal cortex; attentional shifting, implicating dlPFC; and habit learning, implicating SMA. Neural circuit changes were also examined in individuals with alcohol dependence and binge drinkers. Waiting impulsivity was elevated in both groups and the functional connectivity, microstructural integrity and anatomical connectivity of the neural circuit underlying waiting impulsivity were associated with problematic drinking behaviours in both groups. Together, this work establishes that discrete functional subzones of small subcortical regions can be differentiated in humans and that their behavioural correlates can be similarly mapped. The definition of intrinsic network architecture underlying a particular behaviour and the demonstration its disturbance in psychiatric groups will crucially inform the development of future diagnostic and therapeutic models

Training endogenous task shifting using neurologic music therapy

2013 Summer.Includes bibliographical references.People with acquired brain injury (ABI) are highly susceptible to disturbances in executive functioning (EF) and these effects are pervasive. Research studies using music therapy for cognitive improvement in this population are limited. Scientific research regarding the proposed neural correlates of executive functions abound. Additionally, scientific music research is gaining momentum. The presence of shared neural correlates and extended pathways between certain kinds of music and executive functions is clear. Further, the capacity of music training to induce neural plasticity has significant support, but interventions on a clinical level are sparse. The current randomized control trial (n=14) sought to uncover whether using a specific neurologic music therapy approach to train endogenous task shifting would create positive results in standard measures of executive functioning (the Trail Making Test and the PASAT). In this pilot study, participants were randomly assigned to one of three groups: a neurologic music therapy group (NMT), a placebo, singing group and a control group. Both music groups met for one hour a day for five days. One-way ANOVA of the pre- and posttest group differences revealed a statistically significant difference between the NMT group and the placebo group (p= .3189; LSM p= .0315; F=4.44; ƞ2= .446; ɷ2= .329; d= 1.79; MSE=.3189; C.I. -1.6661, -0939). However, a statistically significant difference was not found between the NMT group and the control group. Further, a statistically significant effect was also found between the control group and the placebo group, leading to inconclusive results (p= .3189; LSM p =.0230, C.I. -1.8343, -0.1667; F=4.44; ƞ2= .446; ɷ2= .329; d= 1.79; MSE=.3189). The novelty of meeting in a group to sing songs did not show a difference, providing preliminary support for the importance of therapeutically applied music. Treatment feasibility and future considerations are discussed

Mechanisms of behavioral change targeting automatic processes

In order to eliminate unhealthy behaviors, one must find ways to make better choices. Changing preferences is an important strategy in addressing public health concerns such as the obesity epidemic. In this dissertation, I present several lines of research, which all aim to influence choice behavior. First, we developed a novel extensive training paradigm that uses monetary reinforcement to influence choices for less desired palatable foods over initially more preferred foods. We found that, as reinforced training progressed, there was decreased recruitment of a frontoparietal network of brain regions that have been previously associated with cognitive control. We also found neural evidence that suggests formation of a stronger stimulus-response association as reinforced training progressed. These findings demonstrate that it is possible to influence food choices through reinforcement and that training is associated with a decreasing need for top-down frontoparietal control. However, the long term durability of this change in choice behavior is in question. Learning theory predicts a return to choosing the initially more preferred item simply with the passage of time, despite overtraining the new behavior. Thus, we turned our efforts toward targeting automatic processes to achieve a lasting shift in choice behavior. We found that our attempts to interfere with memory traces for an established choice or to train bottom-up inhibition to avoid particular food items were unsuccessful. However, we found that driving sustained attention toward particular food items at behaviorally relevant points in time during cue-approach training robustly influences choice preferences in favor of those items. Imaging results show that value representation for those items in the ventromedial prefrontal cortex is amplified. Finally, we found that spacing cue-approach training trials over multiple days benefits the long-term maintenance of the cue-approach choice effect. Results presented in this dissertation lay the groundwork for new insights into mechanisms of behavioral change and value-based decision making more broadly as well as suggest some strategies for developing real-world intervention paradigms to help those seeking to adopt and maintain healthier habits.Neuroscienc

The neurocognitive process of preference-based decisions

This thesis focused on three aspects of human preference-based decisions. First, integrating multiple sources of value information had an impact on behavioural performance and the underlying cognitive process. During preference-based judgments, humans combine multiple information sources into a single source of evidence, and behavioural changes are related to the quality of evidence. Second, to investigate psychophysical performance (sensitivity and bias) based on internal value and external perception information, a categorization task was conducted with value information embedded into geometric shapes. As measured by Weber ratio, attaching internal values to geometric shapes resulted in less discriminating sensitivity than perceptual judgements, and there was no difference in the response bias between the two types of decisions. Hence, these findings showed that a single computational process may underlie both value-based and perceptual decisions, and that transferring internal preference onto external perceptual input generates additional noise to the decision-making process. Third, this thesis investigated the MEG signatures of internal value-based decisions as well as their differences from perceptual decisions. Instead of geometrical shapes, internal value information embedded into spatial locations and binary choice task was conducted using the identical visual stimuli in both the internal preference and external perception context. Multivariate patten analysis on source space MEG data showed that more extended visual and frontoparietal activations are sensitive to value differences in value-based decisions. These results provide a foundation for further integrating perceptual and preference-based decisionmaking into a single framework. Overall, findings presented in this thesis contributes to the study of value-based decision-making by integrating novel experimental approaches, cognitive modelling, and electrophysiological investigations of the human brain

Occipitotemporal Representations Reflect Individual Differences in Conceptual Knowledge

Through selective attention, decision-makers can learn to ignore behaviorally irrelevant stimulus dimensions. This can improve learning and increase the perceptual discriminability of relevant stimulus information. Across cognitive models of categorization, this is typically accomplished through the inclusion of attentional parameters, which provide information about the importance assigned to each stimulus dimension by each participant. The effect of these parameters on psychological representation is often described geometrically, such that perceptual differences over relevant psychological dimensions are accentuated (or stretched), and differences over irrelevant dimensions are down-weighted (or compressed). In sensory and association cortex, representations of stimulus features are known to covary with their behavioral relevance. Although this implies that neural representational space might closely resemble that hypothesized by formal categorization theory, to date, attentional effects in the brain have been demonstrated through powerful experimental manipulations (e.g., contrasts between relevant and irrelevant features). This approach sidesteps the role of idiosyncratic conceptual knowledge in guiding attention to useful information sources. To bridge this divide, we used formal categorization models, which were fit to behavioral data, to make inferences about the concepts and strategies used by individual participants during decision-making. We found that when greater attentional weight was devoted to a particular visual feature (e.g., “color”), its value (e.g., “red”) was more accurately decoded from occipitotemporal cortex. We also found that this effect was sufficiently sensitive to reflect individual differences in conceptual knowledge, indicating that occipitotemporal stimulus representations are embedded within a space closely resembling that formalized by classic categorization theory

Predicting Forex Currency Fluctuations Using a Novel Bio-inspired Modular Neural Network

This thesis explores the intricate interplay of rational choice theory (RCT), brain modularity, and artificial neural networks (ANNs) for modelling and forecasting hourly rate fluctuations in the foreign exchange (Forex) market. While RCT traditionally models human decision-making by emphasising self-interest and rational choices, this study extends its scope to encompass emotions, recognising their significant impact on investor decisions. Recent advances in neuro- science, particularly in understanding the cognitive and emotional processes associated with decision-making, have inspired computational methods to emulate these processes. ANNs, in particular, have shown promise in simulating neuroscience findings and translating them into effective models for financial market dynamics. However, their monolithic architectures of ANNs, characterised by fixed struc- tures, pose challenges in adaptability and flexibility when faced with data perturbations, limiting overall performance. To address these limitations, this thesis proposes a Modular Convolutional orthogonal Recurrent Neural Net- work with Monte Carlo dropout-ANN (MCoRNNMCD-ANN) inspired by recent neuroscience findings. A comprehensive literature review contextualises the challenges associated with monolithic architectures, leading to the identification of neural network structures that could enhance predictions of Forex price fluctuations, such as in the most prominently traded currencies, the EUR/GBP pairing. The proposed MCoRNNMCD-ANN is thoroughly evaluated through a detailed comparative analysis against state-of-the-art techniques, such as BiCuDNNL- STM, CNN–LSTM, LSTM–GRU, CLSTM, and ensemble modelling and single- monolithic CNN and RNN models. Results indicate that the MCoRNNMCD- ANN outperforms competitors. For instance, reducing prediction errors in test sets from 19.70% to an impressive 195.51%, measured by objective evaluation metrics like a mean square error. This innovative neurobiologically-inspired model not only capitalises on modularity but also integrates partial transfer learning to improve forecasting ac- curacy in anticipating Forex price fluctuations when less data occurs in the EUR/USD currency pair. The proposed bio-inspired modular approach, incorporating transfer learning in a similar task, brings advantages such as robust forecasts and enhanced generalisation performance, especially valuable in domains where prior knowledge guides modular learning processes. The proposed model presents a promising avenue for advancing predictive modelling in Forex predictions by incorporating transfer learning principles

The role of emotions and physiological arousal in modulating impulsive behaviour

Impulsivity refers to both a stable personality trait and a set of behaviours which undergo momentary changes depending on the current circumstances. Impulsivity plays a vital role in daily life as well as clinical practice as it is associated with drug misuse and certain neuropsychiatric conditions. Because of its great health and well-being importance, it is crucial to understand factors which modulate impulsive behaviours. The current studies investigated the role of emotions and physiological arousal as modulators of impulsive actions and decisions in healthy individuals. A set of experiments was conducted using a variety of methods including behavioural testing, physiological recordings, psychopharmacology and neuroimaging. Studies 1 and 2 clarified the influence of emotional states on distinct dimensions of impulsive behaviours. Study 3 investigated the neural correlates behind the impact of emotions on impulsive actions. Finally, studies 4 and 5 focused on the relationship between physiological arousal and behavioural and trait impulsivity. Our findings demonstrate that a degree to which one’s internal (emotional or physiological) state changes, is associated with behavioural impulsivity level. Importantly, distinct dimensions of impulsivity are differentially sensitive to those changes. Namely, increased state level of physiological arousal is associated with decreased motor ‘stopping’ impulsivity, enhanced subjective ratings and objective measurements of arousal are also related to decreased temporal impulsivity. Increased ratings of stress and increased physiological arousal, however, are associated with higher reflection impulsivity. At the neural level, successful response inhibition requires enhanced activation of prefrontal and parietal areas in impulsive individuals, particularly in negative emotional context, suggesting that behavioural control might be more effortful for highly impulsive individuals. In conclusion, changes in internal bodily state are related to behavioural impulsivity level. Staying more attuned to those changes and finding adaptive ways to adjust behaviour according to bodily needs might be vital to reducing impulsivity levels

Contributions of Human Prefrontal Cortex to the Recogitation of Thought

Human beings have a unique ability to not only verbally articulate past and present experiences, as well as potential future ones, but also evaluate the mental representations of such things. Some evaluations do little good, in that they poorly reflect facts, create needless emotional distress, and contribute to the obstruction of personal goals, whereas some evaluations are the converse: They are grounded in logic, empiricism, and pragmatism and, therefore, are functional rather than dysfunctional. The aim of non-pharmacological mental health interventions is to revise dysfunctional thoughts into more adaptive, healthier ones; however, the neurocognitive mechanisms driving cognitive change have hitherto remained unclear. Therefore, this thesis examines the role of the prefrontal cortex (PFC) in this aspect of human higher cognition using the relatively new method of functional near-infrared spectroscopy (fNIRS). Chapter 1 advances recogitation as the mental ability on which cognitive restructuring largely depends, concluding that, as a cognitive task, it is a form of open-ended human problem-solving that uses metacognitive and reasoning faculties. Because these faculties share similar executive resources, Chapter 2 discusses the systems in the brain involved in controlled information processing, specifically the nature of executive functions and their neural bases. Chapter 3 builds on these ideas to propose an information-processing model of recogitation, which predicts the roles of different subsystems localized within the PFC and elsewhere in the context of emotion regulation. This chapter also highlights several theoretical and empirical challenges to investigating this neurocognitive theory and proposes some solutions, such as to use experimental designs that are more ecologically valid. Chapter 4 focuses on a neuroimaging method that is best suited to investigating questions of spatial localization in ecological experiments, namely functional near-infrared spectroscopy (fNIRS). Chapter 5 then demonstrates a novel approach to investigating the neural bases of interpersonal interactions in clinical settings using fNIRS. Chapter 6 explores physical activity as a ‘bottom-up’ approach to upregulating the PFC, in that it might help clinical populations with executive deficits to regulate their mental health from the ‘top-down’. Chapter 7 addresses some of the methodological issues of investigating clinical interactions and physical activity in more naturalistic settings by assessing an approach to recovering functional events from observed brain data. Chapter 8 draws several conclusions about the role of the PFC in improving psychological as well as physiological well-being, particularly that rostral PFC is inextricably involved in the cognitive effort to modulate dysfunctional thoughts, and proposes some important future directions for ecological research in cognitive neuroscience; for example, psychotherapy is perhaps too physically stagnant, so integrating exercise into treatment environments might boost the effectiveness of intervention strategies