title: Neural systems for choice and valuation with counterfactual learning signals.
abstract: The purpose of this experiment was to test a computational model of reinforcement learning with and without fictive prediction error (FPE) signals to investigate how counterfactual consequences contribute to acquired representations of action-specific expected value, and to determine the functional neuroanatomy and neuromodulator systems that are involved. 80 male participants underwent dietary depletion of either tryptophan or tyrosine/phenylalanine to manipulate serotonin (5HT) and dopamine (DA), respectively. They completed 80 rounds (240 trials) of a strategic sequential investment task that required accepting interim losses in order to access a lucrative state and maximize long-term gains, while being scanned. We extended the standard Q-learning model by incorporating both counterfactual gains and losses into separate error signals. The FPE model explained the participants' data significantly better than a model that did not include counterfactual learning signals. Expected value from the FPE model was significantly correlated with BOLD signal change in the ventromedial prefrontal cortex (vmPFC) and posterior orbitofrontal cortex (OFC), whereas expected value from the standard model did not predict changes in neural activity. The depletion procedure revealed significantly different neural responses to expected value in the vmPFC, caudate, and dopaminergic midbrain in the vicinity of the substantia nigra (SN). Differences in neural activity were not evident in the standard Q-learning computational model. These findings demonstrate that FPE signals are an important component of valuation for decision making, and that the neural representation of expected value incorporates cortical and subcortical structures via interactions among serotonergic and dopaminergic modulator systems.
authors: Department of Systems Neuroscience, University Medical Center Hamburg-Eppendorf, Germany. Electronic address: mtobia@uke.de.
authors: M J
authors: MJ
authors: Tobia
authors: Department of Software Engineering and Theoretical Computer Science, School IV Electrical Engineering and Computer Science, Technische Universität Berlin, Germany; Bernstein Center for Computational Neuroscience Berlin, Germany.
authors: R
authors: R
authors: Guo
authors: Department of Systems Neuroscience, University Medical Center Hamburg-Eppendorf, Germany.
authors: U
authors: U
authors: Schwarze
authors: Department of Software Engineering and Theoretical Computer Science, School IV Electrical Engineering and Computer Science, Technische Universität Berlin, Germany.
authors: W
authors: W
authors: Boehmer
authors: Department of Systems Neuroscience, University Medical Center Hamburg-Eppendorf, Germany.
authors: J
authors: J
authors: Gläscher
authors: Department of Systems Neuroscience, University Medical Center Hamburg-Eppendorf, Germany.
authors: B
authors: B
authors: Finckh
authors: Department of Systems Neuroscience, University Medical Center Hamburg-Eppendorf, Germany.
authors: A
authors: A
authors: Marschner
authors: Department of Systems Neuroscience, University Medical Center Hamburg-Eppendorf, Germany.
authors: C
authors: C
authors: Büchel
authors: Department of Software Engineering and Theoretical Computer Science, School IV Electrical Engineering and Computer Science, Technische Universität Berlin, Germany; Bernstein Center for Computational Neuroscience Berlin, Germany.
authors: K
authors: K
authors: Obermayer
authors: Department of Systems Neuroscience, University Medical Center Hamburg-Eppendorf, Germany.
authors: T
authors: T
authors: Sommer
mesh_terms: D000293:Adolescent; D000328:Adult; D001921:Brain / Q000502:physiology*; D001931:Brain Mapping; D002755:Choice Behavior / Q000502:physiology*; D004298:Dopamine / Q000502:physiology; D006801:Humans; D007092:Imagination / Q000502:physiology; D008279:Magnetic Resonance Imaging; D008297:Male; D008962:Models, Theoretical; D011678:Punishment; D012201:Reward; D012701:Serotonin / Q000502:physiology; D013850:Thinking / Q000502:physiology; D055815:Young Adult
chemical_list: D012701:Serotonin; D004298:Dopamine