Investigating the Shared and Distinct Mechanisms Underpinning Perceptual Decision-Making and Metacognition
Year: 2020
Type: dissertation
Abstract: In order to successfully adjust to changes and learn in the sensory environment, humans must be able to detect whether or not decisions are based on reliable sources of information.Because we cannot always depend on the availability of objective feedback regarding the accuracy of our choices, computing a subjective sense of confidence to guide adaptive behavioural strategies is a necessity.Computational neuroscience has made substantial progress in parsing the basis of these metacognitive evaluations, which are reviewed in the introductory chapter of this thesis.Specifically, a set of mathematical models have been devised which hinge on the idea that the same sensory evidence accumulation processes that mediate perceptual decision-making might also govern the emergence of representations of confidence.Support for this prediction comes from invasive recording techniques in both non-human and human animals.However, many questions about exactly how these signals influence metacognitive judgements remain.For instance, it is unclear whether the decision variable is directly read-out to inform confidence, what the precise temporal dynamics of this evidence accumulation process are and what other information sources might influence the emergence of metacognitive representations.By adopting paradigms that allowed for the identification of these distinct neural signatures in non-invasive human brain recordings the current thesis aimed to elucidate the temporal dynamics as well as unique contributions of these different levels of processing along the sensorimotor hierarchy in the construction of confidence.The experiments presented in Chapter 2 aimed to address two gaps in current explorations of this relationship.Firstly, to extend on previous research by establishing that the sensory evidence accumulation process scales with choice confidence.This was confirmed in two experiments, showing that stronger build-up and higher amplitudes in this signal was associated with higher levels of confidence.This chapter further highlighted important methodological considerations for future work, by demonstrating that domain-general evidence accumulation does not simply continue to build until the choice reports and can be strategically terminated.Secondly, this study aimed to elucidate the role of motor level processes in the construction of confidence.Investigation of effector-specific mu/beta signals showed that, while contralateral motor preparation reached a fixed amplitude prior to response execution, higher activation for the unchosen alternative was associated with lower levels of confidence.These findings were complemented by an analysis of response conflict, which indicated theta band activity was similarly elevated on lower confidence trials.Additionally, the effects occur during a similar time window prior to the response, which provides a tentative indication that motor preparatory signals might indirectly influence metacognitive judgements through the expression of response conflict in theta power.As the curtain falls on this four-year long journey, I cannot help to look back with enormous gratitude to the people that have helped me to bring this thesis over the finish line.I want to start with expressing my deepest appreciation to my supervisor, Redmond O'Connell.It has truly been a blessing to have such an enthusiastic and knowledgeable mentor.Your tireless feedback, humour and boundless patience have made the entire process far more enjoyable.Moreover, you have truly enabled me to become a better researcher then I could have ever imagined being.I also want to thank our close collaborator Simon Kelly for his sharp insights and for helping to put my first steps into the complicated world of computational modelling and Claire Gillan for her valuable feedback and help when setting up the Amazon Mechanical Turk experiment in Chapter 4 of this thesis.I want to thank the current members of the O'Connell lab.Jessica Dully, for your amazing sense of humour, your friendship and the incredible feedback you have given me on (oh so) many rough portions of writing.Kevin Walsh, for your warm words of encouragement and making late nights and weekend days in the office enjoyable.Cian Judd, for your cabaret and musical interludes that have brought me many moments of joy.Katerina Kalou, for acting as a voice of reason during the final stages of this PhD.Elaine Corbett, for your invaluable feedback in the modelling section of this thesis.
Author: Wouter Rys
Language: English
Subfield: Cognitive Neuroscience
Field: Neuroscience
Domain: Life Sciences
Open Access status: green
OpenAlex ID: W3044515465