| Summary: | Changes of Mind' can provide insights into the dynamic and continuous processes underlying decision making and action selection. Previous studies on Changes of Mind have exclusively focused on either perceptual or value-based choice. This thesis investigates the flexible neurocognitive mechanisms that shape voluntary actions, which require integration of internally-generated (endogenous) intentions and externally-cued (exogenous) sensory or value-based information. When information is noisy or changes dynamically, agents sometimes change their voluntary intentions and/or change the movements that are required to implement intentions into action. Continuous movement trajectories were used to capture both types of Change of Mind during ongoing action execution, revealing that 'Changes of Intention' are more frequent when intentions are weak or when the cost of pursuing an intention is high. These findings could be qualitatively reproduced by an attractor network model that continuously integrates endogenous and exogenous information over time, occasionally switching from one attractor state to a different one later on. In an fMRI study, the neural dynamics of intention reversals were investigated, providing evidence that neural patterns in a fronto-parietal network change dynamically to incorporate new decision- and action-relevant evidence after action onset. Finally, while behavioural flexibility is advantageous in many situations, an important hallmark of voluntary control is intention pursuit despite external changes or challenges. For example, people often need to persevere in the face of effort. Patients with post-stroke fatigue showed reduced perseverance compared to healthy controls when goal pursuit required continuous effort, which may cause adverse health-related outcomes. In conclusion, this thesis provides new insights into the continuous neurocognitive mechanisms that shape voluntary actions as they unfold. Reversibility of intentions allows agents to adjust their own actions to the current context, while stability of intentions is necessary for successful goal pursuit. Hence, volition requires balanced integration of endogenous intentions with dynamically-changing exogenous information.
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