Systems neuroscience is the study of the function of neural circuits in intact organisms.This research area is concerned with how cells behave when connected together to form neural networks, and thus forms the link between perception, action and higher cognitive functions on the one hand and cells and molecules on the other. Nonlinear interactions between voltage and ligand-gated channels, second messenger systems, exocytosis, and other processes dictates that these networks will not just be the sums of their parts, but will produce unexpected and complex patterns of activity.