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J Neurophysiol. 2015 Aug;114(2):781-92. doi: 10.1152/jn.00260.2015. Epub 2015 May 27.

No unified reward prediction error in local field potentials from the human nucleus accumbens: evidence from epilepsy patients.

Author information

1
Wellcome Trust Centre for Neuroimaging, University College London, London, United Kingdom; Department of Neurology, Otto-von-Guericke University, Magdeburg, Germany; max-philipp.stenner@med.ovgu.de.
2
Wellcome Trust Centre for Neuroimaging, University College London, London, United Kingdom; Max Planck University College London Centre for Computational Psychiatry and Ageing Research, London, United Kingdom;
3
Department of Neurology, Otto-von-Guericke University, Magdeburg, Germany; Department of Behavioral Neurology, Leibniz Institute for Neurobiology, Magdeburg, Germany;
4
Department of Neurology, Otto-von-Guericke University, Magdeburg, Germany;
5
Epilepsy-Center Berlin-Brandenburg, Department of Neurology, Charité Universitätsmedizin, Berlin, Germany; and.
6
Department of Behavioral Neurology, Leibniz Institute for Neurobiology, Magdeburg, Germany; Department of Stereotactic Neurosurgery, Otto-von-Guericke University, Magdeburg, Germany.

Abstract

Functional magnetic resonance imaging (fMRI), cyclic voltammetry, and single-unit electrophysiology studies suggest that signals measured in the nucleus accumbens (Nacc) during value-based decision making represent reward prediction errors (RPEs), the difference between actual and predicted rewards. Here, we studied the precise temporal and spectral pattern of reward-related signals in the human Nacc. We recorded local field potentials (LFPs) from the Nacc of six epilepsy patients during an economic decision-making task. On each trial, patients decided whether to accept or reject a gamble with equal probabilities of a monetary gain or loss. The behavior of four patients was consistent with choices being guided by value expectations. Expected value signals before outcome onset were observed in three of those patients, at varying latencies and with nonoverlapping spectral patterns. Signals after outcome onset were correlated with RPE regressors in all subjects. However, further analysis revealed that these signals were better explained as outcome valence rather than RPE signals, with gamble gains and losses differing in the power of beta oscillations and in evoked response amplitudes. Taken together, our results do not support the idea that postsynaptic potentials in the Nacc represent a RPE that unifies outcome magnitude and prior value expectation. We discuss the generalizability of our findings to healthy individuals and the relation of our results to measurements of RPE signals obtained from the Nacc with other methods.

KEYWORDS:

deep brain stimulation; local field potentials; nucleus accumbens; reward prediction error

PMID:
26019312
PMCID:
PMC4533060
DOI:
10.1152/jn.00260.2015
[Indexed for MEDLINE]
Free PMC Article

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