Impaired cooperation and prosocial learning during trust game in behavioral variant frontotemporal dementia

Background Interpersonal trust and cooperation are important aspects of prosocial behavior. Dementia can alter social cognition, but it remains unclear how these changes alter propensity to trust and willingness to cooperate with others, and whether there are differences between types of dementia. Objective To determine if patients with behavioral variant frontotemporal dementia (bvFTD) differ from patients with Alzheimer's disease (AD) and cognitively normal controls in trusting behaviors and learning to cooperate. Methods 38 bvFTD patients, 20 AD patients and 26 cognitively normal participants invested money in two separate partners to receive a proportion of the profit in return. One partner returned a fair proportion of the investment ( cooperative partner) while the other partner did not ( selfish partner). We also measured perspective-taking capability for patients by administering the Interpersonal Reactivity Index to their study informants. Results bvFTD patients invested less money on average with the cooperative partner than the AD and control groups and did not learn to cooperate. bvFTD patients also rated the cooperative partner as less trustworthy than AD and controls. Additionally, last investment for the cooperative partner was correlated with perspective-taking skills, as was mean investment for both cooperative and selfish partners, in dementia patients. Conclusions Our results suggest that bvFTD patients are less receptive to reciprocity. Patients with bvFTD do not learn to cooperate with a trustworthy partner even with repeated interactions receiving positive feedback, which was related to impaired perspective-taking abilities. Our findings may shed light on disrupted reinforcement learning as a pathway to impaired prosocial behavior in bvFTD.