Influence of uncertainty and surprise on human corticospinal excitability during preparation for action.
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.
Bestmann
Sven
S
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.
Harrison
Lee M
LM
Wellcome Trust Centre for Neuroimaging, Institute of Neurology, University College London, London WC1N3BG, United Kingdom.
Blankenburg
Felix
F
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.
Mars
Rogier B
RB
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.
Haggard
Patrick
P
Institute of Cognitive Neuroscience, University College London, London WC1N3BG, United Kingdom.
Friston
Karl J
KJ
Wellcome Trust Centre for Neuroimaging, Institute of Neurology, University College London, London WC1N3BG, United Kingdom.
Rothwell
John C
JC
Sobell Department of Motor Neuroscience and Movement Disorders, Institute of Neurology, University College London, London WC1N3BG, United Kingdom.
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