Disentangling the component processes in complex planning impairments following ventromedial prefrontal lesions

Damage to ventromedial prefrontal cortex (vmPFC) in humans disrupts planning abilities in naturalistic settings. However, it is unknown which components of planning are affected in these patients, including selecting the relevant information, simulating future states, or evaluating between these states. To address this question, patients with damage to vmPFC, control lesion patients, and healthy age-matched controls played Four-in-a-Row, a board game of medium planning complexity. Damage to vmPFC disrupted performance in this task compared to both control groups. We then leveraged a computational framework to assess different component processes of planning. Impairments following vmPFC damage included shallower planning depth, and a tendency to overlook game-relevant features. In a simpler planning setting involving binary choices across a short future horizon (‘Two-Step Task’), we found little evidence of planning in all groups, and no behavioural differences between groups. Taken together, these results suggest that planning impairments following vmPFC lesions are apparent in more complex state spaces, and associated with a tendency to overlook relevant information and plan less deeply into the future.