title: Influence of uncertainty and surprise on human corticospinal excitability during preparation for action.
abstract: Actions are guided by prior sensory information [1-10], which is inherently uncertain. However, how the motor system is sculpted by trial-by-trial content of current sensory information remains largely unexplored. Previous work suggests that conditional probabilities, learned under a particular context, can be used preemptively to influence the output of the motor system [11-14]. To test this we used transcranial magnetic stimulation (TMS) to read out corticospinal excitability (CSE) during preparation for action in an instructed delay task [15, 16]. We systematically varied the uncertainty about an impending action by changing the validity of the instructive visual cue. We used two information-theoretic quantities to predict changes in CSE, prior to action, on a trial-by-trial basis: entropy (average uncertainty) and surprise (the stimulus-bound information conveyed by a visual cue) [17-19]. Our data show that during preparation for action, human CSE varies according to the entropy and surprise conveyed by visual events guiding action. CSE increases on trials with low entropy about the impending action and low surprise conveyed by an event. Commensurate effects were observed in reaction times. We suggest that motor output is biased according to contextual probabilities that are represented dynamically in the brain.
authors.affiliation: Sobell Department of Motor Neuroscience and Movement Disorders, Institute of Neurology, University College London, London WC1N3BG, United Kingdom; Wellcome Trust Centre for Neuroimaging, Institute of Neurology, University College London, London WC1N3BG, United Kingdom; Institute of Cognitive Neuroscience, University College London, London WC1N3BG, United Kingdom. Electronic address: s.bestmann@fil.ion.ucl.ac.uk.
authors.forename: Sven
authors.initials: S
authors.lastname: Bestmann
authors.affiliation: Wellcome Trust Centre for Neuroimaging, Institute of Neurology, University College London, London WC1N3BG, United Kingdom.
authors.forename: Lee M
authors.initials: LM
authors.lastname: Harrison
authors.affiliation: Wellcome Trust Centre for Neuroimaging, Institute of Neurology, University College London, London WC1N3BG, United Kingdom; Institute of Cognitive Neuroscience, University College London, London WC1N3BG, United Kingdom.
authors.forename: Felix
authors.initials: F
authors.lastname: Blankenburg
authors.affiliation: Sobell Department of Motor Neuroscience and Movement Disorders, Institute of Neurology, University College London, London WC1N3BG, United Kingdom; Institute of Cognitive Neuroscience, University College London, London WC1N3BG, United Kingdom.
authors.forename: Rogier B
authors.initials: RB
authors.lastname: Mars
authors.affiliation: Institute of Cognitive Neuroscience, University College London, London WC1N3BG, United Kingdom.
authors.forename: Patrick
authors.initials: P
authors.lastname: Haggard
authors.affiliation: Wellcome Trust Centre for Neuroimaging, Institute of Neurology, University College London, London WC1N3BG, United Kingdom.
authors.forename: Karl J
authors.initials: KJ
authors.lastname: Friston
authors.affiliation: Sobell Department of Motor Neuroscience and Movement Disorders, Institute of Neurology, University College London, London WC1N3BG, United Kingdom.
authors.forename: John C
authors.initials: JC
authors.lastname: Rothwell
mesh_terms: D000328:Adult; D002540:Cerebral Cortex / Q000502:physiology*; D003463:Cues; D005260:Female; D006801:Humans; D008297:Male; D009043:Motor Activity / Q000502:physiology*; D013116:Spinal Cord / Q000502:physiology*; D035501:Uncertainty