Beautiful Science: The Modular Brain

So much of our lives take place in our heads – in memory or imagination, deep thought or speculations. Yet, we seldom spare a thought for the very organ that makes this happen: the brain. In this post, I will share what science has revealed about the remarkable architecture of our brains and how this architecture accomplishes so much despite the fact that our brain represents just 2 percent of our entire body.

That our brain consumes 20 percent our energy despite being only 2 percent of our body weight gives an idea of how hard working the brain is. The reason why the brain uses so much energy because it is a powerful electrical system that is constantly active. This electrical system is made up of nearly 100 billion nerve cells or neurons connected to each other in a labyrinthine neural network that enables us to think, perceive, remember, make judgements and plan. The big question is: how does our brain manage such complexity? As alluded a while ago, the answer lies in the brain’s “architecture”. In essence, our brains are built according to very efficient, very economical, space-saving rules, rules that ensure that it can carry out a huge variety of complex tasks every second without it being fried. Modular architecture is the name for this hype-efficient design.

In a modular architecture, clusters of localized neurons called “modules” are specialized to do their thing and at the same, they are connected to other modules to enrich the brain’s capabilities. There are many reasons why a modular design is superior to globally functioning brain like the central command of a communist state). First of all, a modular brain cuts down on energy costs. Since it is divided into units, only regions within a given module need to be active to complete specific assignments. Think of the alternative. If you used your entire brain for every action, your brain’s electricity bill would go through the roof (or cranium)!. Here’s a simple analogy: if you want cool the bedroom at night, you simply switch on the bedroom’s aircon, not all the aircon units of the entire house. Same with the brain.

There are 80 to 100 billion neurons in a human brain, and every single one of them form thousands of connections with other neurons, form local clusters called modules, which in turn are connected with other modules, leading to a complex network of hundreds of trillions of synapses working together to enable brain cells to communicate with each other.

Modular brains are also functionally efficient. This is because multiple modules can process specialized information at the same time. It is much easier to walk, talk, and chew gum at the same time if many modular units are working independently, rather than a single system attempting to coordinate all the actions. Moreover, if the brain behaved as a single unit, then it would need to be a “jack-of-all-trades” to adequately perform all of our daily duties. We know from daily life that this is inefficient.

Economics for example thrive on specialization: farmers farm, doctors treat, bakers bake, garbage men take care of garbage disposal and so on. When people apply themselves and focus on specific tasks, they become good at doing those tasks, leaving other tasks to other “specialists”. Experts are all efficient producers. And when experts work simultaneously, there is greater economic output than if everyone attempted to do a bit of everything. As with economics, so it is with the brain.

Then, there is consciousness, that mysterious ability to feel that one is alive. Although we have yet to have a complete understanding of how consciousness arises from the brain, one thing is certain: dozens of studies have shown that consciousness is resilient. Damage of dysfunction in brain region X may cause a change in behavior Y but consciousness almost always remains intact. Grandpa may have Alzheimzer’s disease, but as long as his heart continues to bear, consciousness, albeit with a checkboard of altered contents, will survive the carnage of his degenerating disease. Only a brain organized by modules, none of which monopolizes consciousness can explain these facts.

Thirdly, and perhaps most importantly, a modular brain is an adaptive brain. Living things live in an ever-changing environment that requires adaptation and learning. Indeed, we evolve that way. A module allows faster adaptation or evolution of a system to a changing environment because one module can be changed independently without changing or losing other already well-adapted modules. This way, the brain can evolve part-by-part without threatening well-functioning aspects of the system.

Even if you take evolution out of the equation, brain modularity is helpful for learning. Scientists studying the brain’s architecture have found that the pattern of particular neural networks changes over the course of learning a new skill. Although many skills take considerable time to perfect, we are able to learn new skills through experience. Imagine if the entire brain has to change the way it functions whenever we acquired a new skill. This would not only be inefficient (why reinvent the wheel?) but positively, maladaptive because we would lose our expertise in old skills.

In summary, the perks of a modular brain are that it saves energy when resources are scarce, allows for specialization yet parallel processing when time is limited, makes it easier to alter functionality when new survival pressures arise, and allows us to add new skills to the inventory of old ones. A modular brain is indeed a Godsend. When one stops to think about it, how could the brain possibly be organized any other way?

Further Reading

Michael S. Gazzaniga, The Consciousness Instinct: Unraveling the Mystery of How the Brain Makes the Mind, Farrar, Strauss and Giroux, New York, 2018.

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