The neural correlates of reaching focal points.

In pure-coordination games where there are multiple Nash equilibria, the selection of coordinated responses is inexplicable by rational-choice theory - yet coordination is ubiquitous in daily interactions. The psychological game theory therefore evokes the idea of focal-points: some equilibria being chosen due to its salience, as well as through predicting (i.e., mentalizing) other's response. Previous work has been limited to investigating how structural atrophy relates to deficits in coordination, or how brain activations differ between intuitive and deliberated coordination. In this study, we investigated how the strategy of coordination is reflected in the brain, compared to when no coordination is required. Using functional near-infrared spectroscopy (fNIRS), we examined the neural correlates of deriving a response to a category where participants had to either answer freely (i.e., a survey) or try to match their response with another participant (i.e., coordinate). We found that the coordination trials elicited significantly larger changes in oxyhemoglobin [HbO] concentration than survey trials in frontopolar and lateral prefrontal cortex (PFC). Individual differences in behavioral focal index was significantly correlated with [HbO] concentration in lateral PFC. Granger Causality (GC) analysis revealed greater effective connectivity from frontopolar to lateral PFC, and less GC from lateral PFC to frontopolar in the coordination condition. Our findings highlight the crucial role of frontopolar and lateral PFC in human coordination.