eprintid: 1467263 rev_number: 50 eprint_status: archive userid: 608 dir: disk0/01/46/72/63 datestamp: 2015-06-12 11:23:49 lastmod: 2020-02-12 23:53:00 status_changed: 2015-06-12 11:23:49 type: thesis metadata_visibility: show item_issues_count: 0 creators_name: Smittenaar, P title: Action control in uncertain environments ispublished: unpub divisions: UCL divisions: A01 divisions: B02 divisions: C07 divisions: D07 divisions: F83 abstract: A long-standing dichotomy in neuroscience pits automatic or reflexive drivers of behaviour against deliberate or reflective processes. In this thesis I explore how this concept applies to two stages of action control: decision-making and response inhibition. The first part of this thesis examines the decision-making process itself during which actions need to be selected that maximise rewards. Decisions arise through influences from model-free stimulus-response associations as well as model-based, goal-directed thought. Using a task that quantifies their respective contributions, I describe three studies that manipulate the balance of control between these two systems. I find that a pharmacological manipulation with levodopa increases model-based control without affecting model-free function; disruption of dorsolateral prefrontal cortex via magnetic stimulation disrupts model-based control; and direct current stimulation to the same prefrontal region has no effect on decision-making. I then examine how the intricate anatomy of frontostriatal circuits subserves reinforcement learning using functional, structural and diffusion magnetic resonance imaging (MRI). A second stage of action control discussed in this thesis is post-decision monitoring and adjustment of action. Specifically, I develop a response inhibition task that dissociates reactive, bottom-up inhibitory control from proactive, top-down forms of inhibition. Using functional MRI I show that, unlike the strong neural segregation in decision-making systems, neural mechanisms of reactive and proactive response inhibition overlap to a great extent in their frontostriatal circuitry. This leads to the hypothesis that neural decline, for 4 example in the context of ageing, might affect reactive and proactive control similarly. I test this in a large population study administered through a smartphone app. This shows that, against my prediction, reactive control reliably declines with age but proactive control shows no such decline. Furthermore, in line with data on gender differences in age-related neural degradation, reactive control in men declines faster with age than that of women. date: 2015-04-28 vfaculties: VFBRS oa_status: green full_text_type: other thesis_class: doctoral_open language: eng thesis_view: UCL_Thesis primo: open primo_central: open_green verified: verified_manual elements_source: Manually entered elements_id: 1028322 lyricists_name: Dolan, Raymond lyricists_name: Smittenaar, Peter lyricists_id: RJDOL46 lyricists_id: PBSMI27 full_text_status: public pagerange: 1 - 272 pages: 272 institution: UCL (University College London) department: Institute of Neurology thesis_type: Doctoral editors_name: Dolan, RJ citation: Smittenaar, P; (2015) Action control in uncertain environments. Doctoral thesis , UCL (University College London). Green open access document_url: https://discovery.ucl.ac.uk/id/eprint/1467263/2/Smittenaar%20thesis%202015.pdf