Prosocial Behavior and Neurodegenerative Disease

Behavioral variant frontotemporal dementia (bvFTD) is a neurodegenerative disease characterized by progressive and dramatic changes in behavior and emotional responses. In particular, patients with bvFTD have deficits in empathy, including the ability to relate and respond to the emotions of others. These deficits are important precursors for prosocial behaviors – actions intended to benefit people other than oneself – and were thus hypothesized to be impaired in patients with bvFTD. Thus far, no known studies have utilized objective laboratory tests to examine patients’ prosocial behaviors. The present study addressed these gaps by using objective laboratory measures (i.e., a donation paradigm) and a multi-method approach by studying the neural and emotional responses (i.e., autonomic and somatic peripheral physiology, facial expressions) associated with prosocial behavior across a sample of patients with neurodegenerative diseases and non-symptomatic aging caregivers. In the present study, 88 participants (17 with bvFTD, 12 with Alzheimer’s disease, and 59 non-symptomatic caregivers) viewed a film of others in distress. Participants were then given the option to donate their own money as a measure of prosocial behavior. Results revealed that patients with bvFTD donated significantly less money than non-symptomatic caregivers, while patients with Alzheimer’s disease and non-symptomatic caregivers donated comparable amounts. When examining emotional responses and regions of neural degeneration as potential mediators of the relationship between diagnosis and prosocial behavior, neither emotional responses nor neural regions were found to mediate the findings with one exception: lower ventral striatum volume was significantly associated with lower levels of prosocial behavior. This finding aligns with research that suggests that the ventral striatum plays a central role in the reward network of the brain, and how evolutionarily, feeling reward when engaging in prosocial behaviors likely conferred benefits in the context of interpersonal relationships. The study extends our understanding of a neurodegenerative disease that profoundly impacts the lives of patients and their families and contributes important new information to the literature on prosocial behavior