Moral decision-making and theory of mind in patients with idiopathic Parkinson's disease.

OBJECTIVE

Cognitive impairments in theory of mind (ToM), executive processing, and decision-making are frequent and highly relevant symptoms in patients with Parkinson's disease (PD). These functions have been related to moral decision-making. Their association to moral decision-making in PD, however, has not been studied yet. It was hypothesized that moral decisions in patients with PD differ from those in healthy control participants, and that more egoistic decisions are related to ToM as well as executive dysfunctions in patients with PD.

METHOD

Nineteen patients with PD and 20 healthy control participants were examined with an everyday moral decision-making task, comprised of 10 low and 10 high emotional forced-choice moral dilemma short stories with egoistic and altruistic options. All participants received an elaborate neuropsychological test battery. Electrodermal skin conductance responses were recorded to examine possible unconscious emotional reactions during moral decision-making.

RESULTS

The groups performed comparably in total scores of moral decision-making. Although ToM did not differ between groups, it was inversely related to altruistic moral decisions in the healthy control group, but not in patients with PD. Executive functions were not related to moral decision-making. No differences were found for skin conductance responses, yet they differed from zero in both groups.

CONCLUSION

Our findings indicate that moral decisions do not differ between patients with PD and healthy control participants. However, different underlying processes in both groups can be presumed. While healthy control participants seem to apply ToM to permit egoistic moral decisions in low emotional dilemmas, patients with PD seem to decide independently from ToM. These mechanisms as well as neuropsychological and neurophysiological correlates are discussed.