Evidence for a Large-Scale Brain System Supporting Allostasis and Interoception in Humans

Large-scale intrinsic brain systems have been identified for exteroceptive senses (e.g., sight, hearing, touch). We introduce an analogous system for representing sensations from within the body, called interoception, and demonstrate its relation to regulating peripheral systems in the body, called allostasis. Employing the recently introduced Embodied Predictive Interoception Coding (EPIC) model, we used tract-tracing studies of macaque monkeys, followed by two intrinsic functional magnetic resonance imaging samples (N = 280 and N = 270) to evaluate the existence of an intrinsic allostatic/interoceptive system in the human brain. Another sample (N = 41) allowed us to evaluate the convergent validity of the hypothesized allostatic/interoceptive system by showing that individuals with stronger connectivity between system hubs performed better on an implicit index of interoceptive ability related to autonomic fluctuations. Implications include insights for the brain’s functional architecture, dissolving the artificial boundary between mind and body, and unifying mental and physical illness

New Insights into the Role of Cortical Hyperexcitability in the Neurotypical Population predisposed to Aberrant Experiences.

Broadly, aberrant experiences are categorised as aberrant perceptual experiences, aberrant body / self-experiences and aberrant beliefs. There is growing evidence that cortical hyperexcitability underlies many aberrant perceptual experiences such as hallucinations, illusions, distortions etc. in the visual domain. Predisposition to these experiences has been associated with a hyperexcitable visual cortex but has not been explored with aberrant body experiences. Given that many conditions and disorders contain both aberrant perceptual and aberrant body experiences, predisposition to cortical hyperexcitability may not be limited to the visual and extra striate cortices and may be involved in mediating atypical cognitive affective states underlying aberrant body experiences. This would then provide evidence for a functional overlap between neural networks involved in certain aberrant perceptual and aberrant body experiences. In part, the main concern with researching aberrant experiences has been the lack of standardised diagnostic tools and methodologies. The present work therefore additionally aimed to explore novel methodological approaches in examining cognitive affective biases underpinning aberrant body experiences. This thesis is comprised of three empirical studies. Chapter 2 assessed the reliability and utility of methodological improvements made to the newly devised Body-Threat Assessment Battery (BTAB – Braithwaite et al., 2020) as a salient tool in examining aberrant body experiences and associated increases in autonomic activity (as measured by skin conductance responses (SCRs) in addition to introducing a novel FaceReader method as a second objective psychophysiological measure. Chapter 3 investigated whether predisposition to cortical hyperexcitability mediated efficacy of applied brain stimulation (using Multi-channel Transcranial Direct Current – MtDCS) to the right ventrolateral prefrontal cortex (rVLPFC) which has been identified as an important structure in emotion regulation and cognitive affective states as part of multi-sensory integration and aberrant body experiences. Finally, Chapter 4 explored the role of interoceptive vulnerability in alternative therapeutic strategies (repetitive Transcranial Magnetic Stimulation – rTMS) in maintaining corticomotor efficiency (primary motor cortex – M1) following upper arm immobilisation. Collectively, this thesis extends and provides new insights, methodologically and theoretically, into cognitive affective biases underlying aberrant experiences

FROM INEQUALITY TO INFLAMMATION: EXPLORING INTERNAL AND EXTERNAL CONTRIBUTIONS TO AFFECTIVE PROCESSING

From influencing our social interactions to molding our physical and mental health, how our brain processes affective stimuli plays a crucial role in healthy human functioning. Utilizing results from 3 unique studies, the current dissertation aims to contribute empirical support for newer theoretical assertions that affective processing is significantly influenced by prior as well as internal physiological information to support allostasis. In Chapter 2, I explore how one’s contextual history may differentially shape how the brain processes affective information by examining the link between socioeconomic position and efficiency within the allostatic interoceptive network. In Chapter 3, I explore inflammation as one source of physiological information that can influence affective processing. In Chapter 4, I examine how shifting inflammation may alter affective processing via changes in motivated behavior. This dissertation closes with a synthesis of the studies discussed and a discussion of 3 future studies that aim to respond to the remaining outstanding questions.Doctor of Philosoph