Mind Blender

Slicing and dicing across neuroscience, tech, and medicine

The Backward Brain

How the brain keeps us who we are and how experience changes it

The brain is a funny juxtaposition of conundrums. In part it seems to undergird the immutable me—that every morning that I wake up I am still Eric Leuthardt. Maybe a little older, but same personality, same habits, likes, fears (spiders), what have you. Even if you put me under the deepest anesthesia and then you wake me up—still me. 

Strangely, this solidity of person is built on a churning ever-changing engine of neurons. The synapses, or connections, between our neurons are mediated by various protein receptors that are turning over every several minutes. So the very complex architecture of our brain’s wiring is literally altered on a moment-by-moment basis. Yet I am still me. The very notion seems akin to building a house on top of a tornado.

So how does the brain do it—make for a constant person, yet constantly change at the same time?

A common analogy that is used for the brain is to compare it to the computer. It’s the information processing core that takes input in through our senses, processes the information (our conscious and unconscious thinking, reflexes, etc.), and kicks out an output in the form of muscle movements and hormones. Going along with this analogy, people often consider the physical stuff like the cortex, the nerve tracts, and nuclei as representing the “hardware;” the relatively permanent structures like the hard drive and chips that allow the signals to transit. The complex patterns of electrical and chemical impulses between neurons are the ephemeral data that we could call the “software.”

The truth actually is backward—the physical stuff is changing and the electric patterns are constantly maintaining the structure. For the brain, the software supports the hardware. This is in part why an organ that is five percent of our body weight consumes about 20% of the heart’s output. Only a small part of this energy is for “evoked” activity—the brain activations associated with a cognitive task such as sensing the outside world, moving our limbs, and talking. The vast majority of energy utilization is associated with fluctuating activity that binds different regions of the brain. 

Funny enough, these are called “resting” state networks. They are called that because they are present regardless of whether the brain is performing a task or not. They are actually present regardless of whether we are awake, asleep, or even deeply sedated. They are anything but at rest, these are the ongoing fluctuations of brain activity that maintain the synaptic connections between different regions of brain. Thus, despite the receptors being constantly turned over at the synapse, these oscillating networks are constantly guiding how the synapses are being rebuilt.

Why do it this way? Seems somewhat inefficient to constantly be rebuilding these connections on an ongoing basis. The reason is to maintain permanence with a flexibility to change. There have been several key studies that have shown with recovery from injury that these networks can indeed change with time. With ongoing input, the networks can shift and alter themselves for a new permanent self. Think of this when you get a corrupted hard drive—the system is forever broken. With an injury to the brain, however, it can rewire itself to return to the best function possible.

In the context of learning, as experience comes in over time they have an effect on these networks as well. So when we try to master a new language, play a musical instrument, or when we take on a new job, the totally novel input can shape the dynamic patterns of our brain. Today, people are frequently talking about controlling one’s diet to optimize health and fitness. Putting things into our body is something we have control over. If one considers ongoing experiences as a form of “food” that shapes our brains networks, just as vegetables keep us slim and junk food makes us fat, we should be choosy about the experience we expose our brain to. Perhaps reality TV should come with a warning label as “junk experience” with low nutritional content.

 

Teaser Image: iStock

Eric Leuthardt, M.D., is the director of the Center of Innovation in Neuroscience and Technology at Washington University School of Medicine, where he researches brain-computer interfaces.

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