BETWEEN SELF AND OTHER: AN INVESTIGATION INTO THE BEHAVIOURAL AND NEURAL CORRELATES OF AMBIGUITY IN AGENCY

Background: In most circumstances we easily distinguish changes to the external world brought about by our own actions from those with external origins. However, there are contexts where the sense of agency is put into question. Little is known about ambiguity characterised by a lack of information for self-other differentiation, despite its relevance to symptoms and levels of consciousness associated with certain mental health conditions. In this PhD thesis by publication, behavioural and neuroimaging methods are used to explore self-other processing capacities in ambiguous conditions. Individual differences are examined in relation to brain response with the aim of shedding light and generating further testable hypotheses on mechanisms of agency in both health and psychosis. Chapter 2: Building on ideas from developmental and perceptual psychology, Chapter 2 lays out the theoretical framework and rationale behind the experimental work. The paper defines the concept of ambiguity in relation to self-other processing. With caregiver-infant interactions and social interactions more generally described as inherently ambiguous, a key proposal is that experience in ambiguity-promoting settings provide conditions necessary for developing reality-testing abilities and a flexible sense of self-other associated with mental heath. Such abilities may be malleable, however, continuing to develop through experience in activities involving intricate joint action such as social dialogue. It is argued that activities such as music-making which require self-other distinctions, yet make differentiation challenging may particularly hone these skills. Implications for phenomena such as hallucinations associated with reduced attributional abilities are discussed. Chapter 3: In the first experimental study, a task was developed that manipulates ambiguity by controlling the probability that a participant’s finger taps results in auditory tones as opposed to tones generated by ‘another’s finger taps’. The ability to accurately attribute actions to self and to other was negatively related to hallucination proneness (HP) and positively related to musical experience (ME). This pattern of results was accentuated by ambiguous conditions where the probability of self- and other-generated tones was equal. This not only associates HP with specific difficulties in dealing with ambiguity, but also supports the notion that attribution abilities are malleable and can improve through experience in ambiguous settings such as those involving intricate joint action. Chapter 4: Chapter 4 investigated neural responses to modulating the degree of control belonging to self and other using the probability method tested in Chapter 3 in a parametric fMRI block design. Linear and non-linear stimulus-response functions highlighted a network of brain regions previously associated with motor control and self-other processing to be particularly sensitive to control belonging to self. All regions also displayed significant non-linearity with decreased response in ambiguous conditions. This study provides initial insight into attributional ambiguity-processing in the brain. Chapter 5: In Chapter 5, neural responses to the task were examined in relation to individual differences. Combining whole-brain univariate and a task-based ICA approach, results showed increased ambiguity-related response in sensory and DMN regions to be related to positive schizotypy and difficulties in processing ambiguity, in contrast to task performance and musical experience which correlated with reduced response. Chapter 6: The final study examined the effects of attribution performance, including performance specifically related to ambiguity, on resting-state functional connectivity using ICA, dual regression and a network analysis. Findings showed connectivity between frontal networks and other brain regions increased with reduced task performance. Conclusions: The thesis concludes with a discussion of these collective findings and implications for future research. Together the behavioural and imaging findings point towards the importance of ambiguity in self-other processing. Increased insight into the topic may enhance our understanding of agency mechanisms underlying ‘self-disorders’ such as schizophrenia and eventually contribute to extending the range of therapeutic possibilities.