Granger causality analysis of state dependent functional connectivity of neurons in orofacial motor cortex during chewing and swallowing

Primate feeding behavior is characterized by a series of jaw movement cycles of different types making it ideal for investigating the role of motor cortex in controlling transitions between different kinematic states. We recorded spiking activity in populations of neurons in the orofacial portion of primary motor cortex (MIo) of a macaque monkey and, using a Granger causality model, estimated their functional connectivity during transitions between chewing cycles and from chewing to swallowing cycles. We found that during rhythmic chewing, the network was dominated by excitatory connections and exhibited a few “out degree” hub neurons, while during transitions from rhythmic chews to swallows, the numbers of excitatory and inhibitory connections became comparable, and more temporarily varying “in degree” hub neurons emerged. Furthermore, based on shared connections between neurons between different networks, networks from same state transitions were quantitatively shown to be more similar. These results suggest that networks of functionally connected neurons in MIo change their operative states with changes in kinematically defined behavioral states.