title: Reward Pays the Cost of Noise Reduction in Motor and Cognitive Control.
abstract: Speed-accuracy trade-off is an intensively studied law governing almost all behavioral tasks across species. Here we show that motivation by reward breaks this law, by simultaneously invigorating movement and improving response precision. We devised a model to explain this paradoxical effect of reward by considering a new factor: the cost of control. Exerting control to improve response precision might itself come at a cost--a cost to attenuate a proportion of intrinsic neural noise. Applying a noise-reduction cost to optimal motor control predicted that reward can increase both velocity and accuracy. Similarly, application to decision-making predicted that reward reduces reaction times and errors in cognitive control. We used a novel saccadic distraction task to quantify the speed and accuracy of both movements and decisions under varying reward. Both faster speeds and smaller errors were observed with higher incentives, with the results best fitted by a model including a precision cost. Recent theories consider dopamine to be a key neuromodulator in mediating motivational effects of reward. We therefore examined how Parkinson's disease (PD), a condition associated with dopamine depletion, alters the effects of reward. Individuals with PD showed reduced reward sensitivity in their speed and accuracy, consistent in our model with higher noise-control costs. Including a cost of control over noise explains how reward may allow apparent performance limits to be surpassed. On this view, the pattern of reduced reward sensitivity in PD patients can specifically be accounted for by a higher cost for controlling noise.
authors.affiliation: Nuffield Department of Clinical Neurosciences, John Radcliffe Hospital, Oxford OX3 9DU, UK; Department of Experimental Psychology, University of Oxford, Oxford OX1 3UD, UK; Institute of Neurology, University College London, London WC1N 3BG, UK; Institute of Cognitive Neuroscience, University College London, London WC1N 3AR, UK; National Hospital for Neurology and Neurosurgery, Queen Square, London WC1N 3BG, UK. Electronic address: sanjay.manohar@ndcn.ox.ac.uk.
authors.forename: Sanjay G
authors.initials: SG
authors.lastname: Manohar
authors.affiliation: Nuffield Department of Clinical Neurosciences, John Radcliffe Hospital, Oxford OX3 9DU, UK; Department of Experimental Psychology, University of Oxford, Oxford OX1 3UD, UK.
authors.forename: Trevor T-J
authors.initials: TT
authors.lastname: Chong
authors.affiliation: Nuffield Department of Clinical Neurosciences, John Radcliffe Hospital, Oxford OX3 9DU, UK; Department of Experimental Psychology, University of Oxford, Oxford OX1 3UD, UK.
authors.forename: Matthew A J
authors.initials: MA
authors.lastname: Apps
authors.affiliation: Institute of Neurology, University College London, London WC1N 3BG, UK; National Hospital for Neurology and Neurosurgery, Queen Square, London WC1N 3BG, UK.
authors.forename: Amit
authors.initials: A
authors.lastname: Batla
authors.affiliation: Institute of Neurology, University College London, London WC1N 3BG, UK; National Hospital for Neurology and Neurosurgery, Queen Square, London WC1N 3BG, UK.
authors.forename: Maria
authors.initials: M
authors.lastname: Stamelou
authors.affiliation: National Hospital for Neurology and Neurosurgery, Queen Square, London WC1N 3BG, UK.
authors.forename: Paul R
authors.initials: PR
authors.lastname: Jarman
authors.affiliation: Institute of Neurology, University College London, London WC1N 3BG, UK; National Hospital for Neurology and Neurosurgery, Queen Square, London WC1N 3BG, UK.
authors.forename: Kailash P
authors.initials: KP
authors.lastname: Bhatia
authors.affiliation: Nuffield Department of Clinical Neurosciences, John Radcliffe Hospital, Oxford OX3 9DU, UK; Department of Experimental Psychology, University of Oxford, Oxford OX1 3UD, UK; Institute of Neurology, University College London, London WC1N 3BG, UK; Institute of Cognitive Neuroscience, University College London, London WC1N 3AR, UK; National Hospital for Neurology and Neurosurgery, Queen Square, London WC1N 3BG, UK.
authors.forename: Masud
authors.initials: M
authors.lastname: Husain
mesh_terms: D003071:Cognition / Q000502:physiology*; D003657:Decision Making / Q000502:physiology*; D004298:Dopamine / Q000378:metabolism; D006801:Humans; D008959:Models, Neurological; D009043:Motor Activity / Q000502:physiology*; D010300:Parkinson Disease / Q000503:physiopathology*; D011597:Psychomotor Performance / Q000502:physiology*; D012201:Reward; D012438:Saccades / Q000502:physiology
chemical_list: D004298:Dopamine
keywords: decision-making; dopamine; drift-diffusion model; motivation; speed-accuracy trade-off