Résumé
Background: Schizophrenia has a core feature of cognitive dysfunctions. Since these deficits are predictive for patients'
functional outcome, understanding their origin is of great importance to improve their daily lives. A specific
component of the deficit involves social decision-making, which can be studied using the Ultimatum Game
(UG). In this task, a “proposer” proposes a share of money to a “responder”, who can either accept or reject this
offer. If the responder accepts the proposal, both win money. If the responder refuses, both players end up with
nothing. Therefore, the UG evaluates decision-making strategies and social interaction.
Methods:Wecompared the neuronal bases of schizophrenic patientswith healthy controls,while performing the
UG. Electroencephalography (EEG) was used to find differences in the event-related potential (ERP) components
typical for the UG, namely the P2 and feedback-related negativity (FRN). Source reconstruction was further used
to define the origin of these differences.
Results: In the proposer condition, no differenceswere found in amplitude of the P2 and FRN components. In contrast,
in the responder condition, significant differences were found for the amplitude of the FRN (p = 0.009).
Using source reconstruction, a different activation in a border zone of the dorsolateral and the medial prefrontal
cortex was revealed in schizophrenic patients to underlie this component.
Conclusions: We suggest that the difference found in the FRN amplitude is associated with difficulties of patients
in interpreting another's behavior. Although schizophrenic patients correctly activate neuronal bases in the proposer
condition, they were not able to activate the same networks in the responder condition, thereby exposing
their difficulties in social interaction.