Elliott, Natasha Alicia
(2023)
Investigating the mechanisms of neural-visceral coupling for therapeutic applications.
PhD thesis, University of Nottingham.
Abstract
Anxiety and mood disorders are commonly characterised by emotion regulation difficulties. Research suggests meditation practice improves emotion reactivity and well-being by modifying attention regulation. Most meditation practices involve directing attention towards internal sensations, such as the breath. It is thought that attending to internal signals re-calibrates executive function processes, such as how attention is allocated and the number of cognitive resources required to process such information. Studies have shown meditation modifies neural activity in brain regions associated with executive function and enhances relaxed states, indicated by an increase in autonomic vagal tone. However, despite meditation originating several thousand years ago, the interaction between these neural and physiological mechanisms and how they relate to therapeutic effects is yet to be understood. This thesis examines the mechanisms of neural-visceral integration during breath-focused meditation (Su-soku) to facilitate psychopathological knowledge and the development of future therapeutic interventions.
To investigate the effects of meditation, 80 healthy participants, across two data sets, engaged in either Su-soku meditation or observed a relaxing woodland scene. Based on previous studies, neural and autonomic activity was recorded using electroencephalography (EEG) and electrocardiography (ECG), respectively. Studies in this thesis primarily focus on whether there are significant differences in cerebral and autonomic activity between the Su-soku meditation and woodland scene conditions and the relationship between these measures. A secondary aim was to investigate the therapeutic effects of these interventions. As a result, cognitive function and mood were examined using a cognitive flanker task and mood state questionnaire before and after assigned intervention conditions.
Fronto-midline (FM) oscillatory power in theta, alpha and beta frequencies were significantly modulated from baseline and across Su-soku blocks, which suggests breath-focused meditation induces an altered attentive state. Furthermore, meditation moderately enhanced the vagal tone compared to the relaxing woodland scene. This thesis also demonstrates for the first time that sustained attention towards the breath, via Su-soku meditation, promotes a tendency for FM-oscillatory power to peak during exhalation. According to previous literature, autonomic phases, such as the respiratory and cardiac cycles, have been associated with changes in attention regulation. As a result, finding a relationship between neural oscillations and the respiratory cycle may reflect neural modulation, via cardio-respiratory synchrony mechanisms, to facilitate the processing of internal signals. Exploratory work suggested synchronised cardiac-respiratory signals, referred to as resonance breathing, may enhance the effects of meditation, such as the neural processing of cardiac signals and improving mood.
While further research is warranted, this thesis provides novel insights into the role of neural-visceral interactions during breath-focused meditation and highlights potential future therapeutic applications of such work.
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