Conflict-dependent dynamic of subthalamic nucleus oscillations during moral decisions

Abstract

Although lesional, neuroimaging, and brain stimulation studies have provided an insight into the neural mechanisms of judgement and decision-making, all these works focused on the cerebral cortex, without investigating the role of subcortical structures such as the basal ganglia. Besides being an effective therapeutic tool, deep brain stimulation (DBS) allows local field potential (LFP) recordings through the stimulation electrodes thus providing a physiological “window” on human subcortical structures. In this study we assessed whether subthalamic nucleus LFP oscillations are modulated by processing of moral conflictual, moral nonconflictual, and neutral statements. To do so, in 16 patients with Parkinson's disease (8 men) bilaterally implanted with subthalamic nucleus (STN) electrodes for DBS, we recorded STN LFPs 4 days after surgery during a moral decision task. During the task, recordings from the STN showed changes in LFP oscillations. Whereas the 14–30 Hz band (beta) changed during the movement executed to perform the task, the 5–13 Hz band (low-frequency) changed when subjects evaluated the content of statements. Low-frequency band power increased significantly more during conflictual than during nonconflictual or neutral sentences. We conclude that STN responds specifically to conflictual moral stimuli, and could be involved in conflictual decisions of all kinds, not only those for moral judgment. LFP oscillations provide novel direct evidence that the neural processing of conflictual decision-making spreads beyond the cortex to the basal ganglia and encompasses a specific subcortical conflict-dependent component.

Keywords:

• Moral decisions
• Conflict
• Subthalamic nucleus
• Local field potentials
• Deep brain stimulation

Acknowledgments

This study was supported by the ERANET-Neuron Grant “PhysiolDBS” (Neuron-48-013), by Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico (Milan, Italy), Università degli Studi di Milano (Italy), IRCCS Istituto Neurologico Carlo Besta, IRCCS Istituto Ortopedico Galeazzi (Milan, Italy), Istituto Neurologico Mondino (Pavia, Italy), Ministero della Sanità (Italy), Ministero dell'Università e della Ricerca Scientifica e Tecnologica (Italy). The authors wish to thank Guglielmo Foffani for his helpful advice on data analysis.

Notes

*The first three authors contributed equally to this work.