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

Joshi, Shalmali D and Braithwaite, Jason J and Nuttall, Helen (2022) New Insights into the Role of Cortical Hyperexcitability in the Neurotypical Population predisposed to Aberrant Experiences. PhD thesis, Lancaster University.

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Abstract

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.