title: Hierarchical prediction errors in midbrain and basal forebrain during sensory learning.
abstract: In Bayesian brain theories, hierarchically related prediction errors (PEs) play a central role for predicting sensory inputs and inferring their underlying causes, e.g., the probabilistic structure of the environment and its volatility. Notably, PEs at different hierarchical levels may be encoded by different neuromodulatory transmitters. Here, we tested this possibility in computational fMRI studies of audio-visual learning. Using a hierarchical Bayesian model, we found that low-level PEs about visual stimulus outcome were reflected by widespread activity in visual and supramodal areas but also in the midbrain. In contrast, high-level PEs about stimulus probabilities were encoded by the basal forebrain. These findings were replicated in two groups of healthy volunteers. While our fMRI measures do not reveal the exact neuron types activated in midbrain and basal forebrain, they suggest a dichotomy between neuromodulatory systems, linking dopamine to low-level PEs about stimulus outcome and acetylcholine to more abstract PEs about stimulus probabilities.
authors.affiliation: Translational Neuromodeling Unit (TNU), Institute for Biomedical Engineering, University of Zurich and Swiss Federal Institute of Technology (ETH), 8032 Zurich, Switzerland; Laboratory for Social and Neural Systems Research (SNS), University of Zurich, 8091 Zurich, Switzerland. Electronic address: iglesias@biomed.ee.ethz.ch.
authors.forename: Sandra
authors.initials: S
authors.lastname: Iglesias
authors.forename: Christoph
authors.initials: C
authors.lastname: Mathys
authors.forename: Kay H
authors.initials: KH
authors.lastname: Brodersen
authors.forename: Lars
authors.initials: L
authors.lastname: Kasper
authors.forename: Marco
authors.initials: M
authors.lastname: Piccirelli
authors.forename: Hanneke E M
authors.initials: HE
authors.lastname: den Ouden
authors.forename: Klaas E
authors.initials: KE
authors.lastname: Stephan
mesh_terms: D000161:Acoustic Stimulation; D000328:Adult; D001499:Bayes Theorem; D059907:Functional Neuroimaging; D006801:Humans; D007858:Learning / Q000502:physiology*; D008297:Male; D008636:Mesencephalon / Q000502:physiology*; D010775:Photic Stimulation; D016548:Prosencephalon / Q000502:physiology*