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