How do brains meet the challenge of network communication?

"Can't write today" by TonyHall is licensed with CC BY 2.0.

The physical laws of the universe make communication among separated entities unlikely. The central and perhaps most unsettling implication of Einstein’s theory of relativity is that no two locations in space can ever be fully reconciled. They will always be separate, and even light cannot provide instantaneous connection. At galactic scales, light can take thousands of years to travel from star system to star system, ensuring that no reliable connection or exchange of information is possible. At a fundamental level, choosing to interact with someone or something at a distance away from ourselves is problematic in our universe.

Though the brain is much smaller than a galaxy, it still faces the challenge of getting information from one place to another in real time. It must do so in an uncertain environment. Lots of things can go wrong when trying to get a message from here to there, even if the distance traveled is just a few millimeters of brain tissue. Message corruption can come from a host of possible failures in a neuron’s chemical machinery, from spontaneous firing of a nearby neuron, or even from an errant cosmic ray. With the speed of message transmission far slower than that of light, the consequences of message failure could be large, and not easily remedied.

The biggest problem of all is selectivity. How do we let one out of many distant parties know that we would like to communicate with them, and then do so reliably and in real time? A communication system is not worthy of the name if we cannot select at will with whom we will communicate.

It has taken humans thousands of years to solve the challenges of communication. For most of human history, fast, selective, reliable communication has been a distant dream, and a sharp contrast to the clunky, furtive, slow, inflexible and error-prone reality of semaphore, telegraph, post, and other systems.

Yet with today’s internet, we have an extremely efficient and robust solution. The internet is not perfect—and the content of messages we send on it are another matter entirely. But the internet has provided a stupendously efficient solution the problems of fast, selective, and reliable message passing, allowing billions of entities to intercommunicate across every land mass, as well as in the skies and underground. This success comes in the context of components and a global environment that are uncertain even in the best of times. Everything from squirrels to heat waves and solar storms can interrupt signals on the internet. But it succeeds because it was designed to work despite an uncertain environment.

The brain faces the same challenges of massive intercommunication, but this fact has been obscured by thinking of it as a computer. While the internet was engineered to address the challenges of an uncertain world, computers largely don’t need to worry about them. After loading it with algorithms, data, and electrical current, a computer requires no interactions outside its housing. The core of a computer has a small number of strictly regulated streams of information (essentially just external data and memory data), and permits a similarly small number of outputs. There is little selectivity in the process.

How has the brain met the challenges of communicating within itself?

We can rule out the notion that the brain has no overarching communication strategy. The brain has 86 billion neurons to work with—each a tiny bag of highly choreographed chemical interactions, and each just a few hops away from any other.

Together, neurons need to achieve diverse and flexible behavior. To do so, evolution must have shaped the brain’s strategy for intercommunication. The idea of An Internet in Your Head is to examine how has the brain has achieved reliable and selective communication using neurons. Though the brain is not exactly like the internet, I argue that it likely exploits similar communication strategies for similar reasons.

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