title: Adaptive Prediction Error Coding in the Human Midbrain and Striatum Facilitates Behavioral Adaptation and Learning Efficiency.
abstract: Effective error-driven learning benefits from scaling of prediction errors to reward variability. Such behavioral adaptation may be facilitated by neurons coding prediction errors relative to the standard deviation (SD) of reward distributions. To investigate this hypothesis, we required participants to predict the magnitude of upcoming reward drawn from distributions with different SDs. After each prediction, participants received a reward, yielding trial-by-trial prediction errors. In line with the notion of adaptive coding, BOLD response slopes in the Substantia Nigra/Ventral Tegmental Area (SN/VTA) and ventral striatum were steeper for prediction errors occurring in distributions with smaller SDs. SN/VTA adaptation was not instantaneous but developed across trials. Adaptive prediction error coding was paralleled by behavioral adaptation, as reflected by SD-dependent changes in learning rate. Crucially, increased SN/VTA and ventral striatal adaptation was related to improved task performance. These results suggest that adaptive coding facilitates behavioral adaptation and supports efficient learning.
authors.affiliation: Department of Physiology, Development, and Neuroscience, University of Cambridge, Downing place, Cambridge CB2 3DY, United Kingdom; Department of Psychiatry, University of Cambridge, Robinson Way, Cambridge CB2 0SZ, United Kingdom. Electronic address: k.diederen@gmail.com.
authors.forename: Kelly M J
authors.initials: KM
authors.lastname: Diederen
authors.affiliation: Department of Psychiatry, University of Cambridge, Robinson Way, Cambridge CB2 0SZ, United Kingdom; Cambridgeshire and Peterborough NHS Foundation Trust, Cambridge CB21 5EF, United Kingdom.
authors.forename: Tom
authors.initials: T
authors.lastname: Spencer
authors.affiliation: Department of Physiology, Development, and Neuroscience, University of Cambridge, Downing place, Cambridge CB2 3DY, United Kingdom.
authors.forename: Martin D
authors.initials: MD
authors.lastname: Vestergaard
authors.affiliation: Department of Psychiatry, University of Cambridge, Robinson Way, Cambridge CB2 0SZ, United Kingdom; Cambridgeshire and Peterborough NHS Foundation Trust, Cambridge CB21 5EF, United Kingdom.
authors.forename: Paul C
authors.initials: PC
authors.lastname: Fletcher
authors.affiliation: Department of Physiology, Development, and Neuroscience, University of Cambridge, Downing place, Cambridge CB2 3DY, United Kingdom.
authors.forename: Wolfram
authors.initials: W
authors.lastname: Schultz
mesh_terms: D000223:Adaptation, Psychological / Q000502:physiology*; D003342:Corpus Striatum / Q000502:physiology*; D006801:Humans; D007858:Learning / Q000502:physiology*; D008279:Magnetic Resonance Imaging; D008960:Models, Psychological; D059906:Neuroimaging; D009474:Neurons; D011597:Psychomotor Performance / Q000502:physiology; D012201:Reward; D013378:Substantia Nigra / Q000502:physiology*; D017557:Ventral Tegmental Area / Q000502:physiology*
keywords: fMRI; normalization; performance; reward; standard deviation