The Topology of Networks and Cortical Synchrony

5 In cortex, there are several electrically coupled inhibitory interneuronal 6 networks which are thought to be critical to temporal coordination of 7 cortical and hippocampal oscillations seen in EEG. This is because gap8 junction mediated networks have many properties, such as speed and 9 bidirectionality, desirable for neural synchronization. Gap junctions 10 exclusively connect GABAergic neurons of the same type, implying distinct 11 functional roles for each type of inhibitory network. Using BRIAN, we built 12 a model simulating Layer IV excitatory neurons, which receive thalamic 13 input and synapse onto gap-junction coupled interlaminar inhibitory 14 neurons, which in turn inhibit Layer VI excitatory neurons. The electrical 15 coupling of the inhibitory layer drives synchronization of neuronal firing in 16 Layer VI which is dependent on the topology the electrically connected 17 inhibitory network. We investigated how lattice (nearest neighbor), random, 18 and small world topologies effect synchronization. Small world networks 19 occur when a percent of connections in a lattice network are rewired 20 randomly, resulting in the path length L between any two neurons scaling 21 with the logarithm of N. Small world networks are less likely to exist in 22 systems where links arise mainly from spatial or temporal proximity. We 23 found that small-world network topology for the gap-junction connected 24 inhibitory network results in the highest correlation between spiking of 25 neurons in the inhibited layer. 26 27