Tit for Tat: Costly Punishment in Manifest Huntington's Disease

We aimed to investigate costly punishment in patients with Huntington's disease (HD).

HD is an autosomal dominant neurodegenerative disease with motor, cognitive, and psychiatric symptoms. As neuropsychiatric abnormalities often precede motor symptoms, we wanted to assess whether costly punishment is part of the neuropsychological profile of patients with HD.

A total of 40 non-demented subjects were prospectively enrolled in this study with a between-subject design comparing manifest HD patients (n = 18) to healthy controls (HC; n = 22). All participants performed 8 rounds of a costly punishment task, in which money was shared unevenly in 5 rounds or in a fair manner in the remaining 3 rounds. Participants then had to decide whether they wanted to punish the trustee. Furthermore, all participants underwent neuropsychological background tasks.

HD patients performed worse in the neuropsychological background tests compared to HC (all p values <0.05). Moreover, HD patients punished more often in fair (Wald χ2 = 5.03, p = 0.025) but not in unfair rounds (Wald χ2 = 1.63, p = 0.202).

Our results demonstrate increased costly punishment during fair conditions in HD patients. Whether this behaviour is due to a lack of recognition of social norms, an impairment in top-down inhibition, or an effect of antidopaminergic medication remains unclear.