Wiring the Brain

The prevailing model for how the network of the brain is organized is the “small-world” network.   In such a network, most units, or nodes, are very sparsely and only locally connected.   However, a very small proportion of nodes, called hubs, are very highly connected, and over longer distances.   These hubs thus provide an indirect but short pathway of connectivity between any two nodes in the network (like people with thousands of “friends” on Facebook).   This overall architecture is highly efficient and robust and can be observed not just at the level of networks of neurons but also at   a higher level of brain organization, in the pattern of connectivity of cortical areas.   Indeed, it is also typical of genetic, social and many other networks, including the internet.   In the brain, the existence of hub neurons had thus been hypothesised, but these beasts had not actually been observed until a recent study by Rosa Cossart and colleagues.   They were analysing the activity patter...