Fig. 1. Neuronal structure and two types of neural networks. (  A ) Cortical pyramidal cell architecture with multiple dendrites branching from a pyramid-shaped cell body (soma) from which descends a single, outgoing axon. Pyramidal cell dendrite (  upper left ) receives incoming axon signal at a chemical/neurotransmitter synapse. Another dendrite (  upper right ) links to another neuron’s dendrite by a window-like (dendritic–dendritic) gap junction electrotonic synapse. (  B ) Schematic version of the same type of neuron with three dendrites and single axon, and connections as used in  A . (  C ) Network of neurons connected serially by axonal–dendritic chemical/neurotransmitter synapses. Information/excitation flows unidirectionally (counterclockwise) from axon to dendrite through the network. Electrical recordings at various points in the network’s spatial distribution show single voltage spike potentials propagating spatially through the network. (  D ) Network of neurons (and glia) linked by gap junctions, mostly dendritic–dendritic but also by glial cell gap junctions. Inputs to the network are from axonal–dendritic chemical synapses; outputs from the network are from axons of neuron components. Because gap junction–connected neuronal dendrites depolarize synchronously, electrical recordings at various points in the network’s spatial distribution show synchronous voltage depolarizations , e.g. , at γ synchrony (coherent 40 Hz). Both membranes and cytoplasmic interiors are continuous throughout the network.