Altered emotional morality in frontotemporal dementia.

INTRODUCTION: Frontotemporal dementia (FTD), a disorder characterised by abnormal social behaviour and potential sociopathy, provides a window to the neurobiology of moral behaviour. This study investigated the basis of altered moral judgements in patients with FTD.

METHODS: We administered an inventory of moral knowledge, five "reasoned" moral dilemmas, and five "emotional" moral dilemmas where subjects may cause direct harm to another through their own actions, to 21 patients with FTD compared to 21 comparably mildly impaired patients with Alzheimer's disease (AD) and 21 normal controls. Among the FTD patients, the results were compared to findings on functional neuroimaging.

RESULTS: All groups showed retention of knowledge for moral behaviour and the ability to make reasoned moral judgements. In contrast to the other groups, the FTD patients were altered in their ability to make emotional moral judgements. Among the FTD patients, the altered moral judgements corresponded to right hemisphere frontotemporal involvement.

CONCLUSIONS: In FTD patients, these findings suggest a decreased emotional responsiveness to others and a tendency to respond to moral dilemmas in a calculated fashion. Such a disturbance may result from ventromedial frontal dysfunction in FTD and supports the presence of a "morality" network in the brain, predominantly in the right hemisphere.