Dynamic emergence of relational structure network in human brains.

Reasoning the hidden relational structure from sequences of events is a crucial ability humans possess, which helps them to predict the future and make inferences. Besides simple statistical properties, humans also excel in learning more complex relational networks. Several brain regions are engaged in the process, yet the time-resolved neural implementation of relational structure learning and its contribution to behavior remains unknown. Here human subjects performed a probabilistic sequential prediction task on image sequences generated from a transition graph-like network, with their brain activities recorded using electroencephalography (EEG). We demonstrate the emergence of two key aspects of relational knowledge - lower-order transition probability and higher-order community structure, which arise around 540-930 ms after image onset and well predict behavioral performance. Furthermore, computational modeling suggests that the formed higher-order community structure, i.e., compressed clusters in the network, could be well characterized by a successor representation operation. Overall, human brains are computing the temporal statistical relationship among discrete inputs, based on which new abstract graph-like knowledge could be constructed.