|By Tré LaRosa
Pretty much anybody you might ask would likely agree that the brain is a complicated organ. It’s the organ where our “I-ness” resides. Our brain is how we experience the world and our lives as thinking, conscious, sentient multi-cellular organisms. Our brain is what allows “us,” whatever “we” are, to sense and perceive the world our bodies occupy. We might all agree that the brain is complex, but this fleshy organ in our skulls is not just complex. Michio Kaku, a world-renowned theoretical physicist, expressed the complexity of the brain in much more stark terms, going as far as to say the brain is “the most complicated object in the known universe.” Not black holes, not dark matter, not octopuses, not the Higgs boson, nope; the brain.
At first glance, this expression sounds hyperbolic. We know our brains; we are our brains. The only world we know of is the world we experience in our minds. In science, we like to group like things; we group animals by their lineages, we group elements by similar properties, and we group parts of our bodies. All of us have cells that make up our tissues and tissues come together to make organs and then many organs work together as organ systems. Tissues are comprised of many different cells with different functions but together they come together to form a tissue which has multiple purposes. Organs, then, have multiple different types of tissues that function together so the organ can serve its broader purposes. Those organs then work in concert with other organs as part of organ systems. All of this results in a human! In this way, then, the brain is an organ like all others. It is composed of fat, water, protein, carbohydrates, and salts and contains blood vessels and nerves. These nerves include neurons and glial cells. But unlike other organs, each complex in their own right, the research community doesn’t actually know how the brain actually works.
It should be noted that Kaku’s quote contains a bit more than just the comment about how the brain is the most complex organ in the known universe. The full quote concisely conveys the magnitude of connections contained in the human brain: “The human brain has 100 billion neurons, each neuron connected to 10,000 other neurons. Sitting on your shoulders is the most complicated object in the known universe.” First, Kaku’s figure of 100 billion neurons is one that is commonly quoted but never cited, and it’s actually incorrect. The best estimate as of now is closer to (a still very large) 86 billion neurons plus or minus about 10%. (Perhaps Kaku did not intend to be exact when he said that quote. The real estimate being closer to 86 billion does not detract from his point: the brain is nevertheless incredibly complex and comprises an incomprehensible amount of neurons.) Additionally, the brain has about the same or more glial cells. Both neurons and glial cells are critical for the function of the brain but they have very different roles. Neurons carry information and are what allow our brains to control the rest of our bodies while glial cells operate are the support cells. As the National Cancer Institute puts it, glial cells “support, nourish, and protect the neurons.” The other portion of Kaku’s quote captures the dizzying interconnectivity of neurons in our brains, as depicted in the MRI image below. The second image shows this interconnectivity in much finer detail, showing how each neuron forms webs of interconnectivity with several others.
Xavier Gigandet et. al. – Gigandet X, Hagmann P, Kurant M, Cammoun L, Meuli R, et al. (2008) Estimating the Confidence Level of White Matter Connections Obtained with MRI Tractography. PLoS ONE 3(12): e4006. doi:10.1371/journal.pone.0004006
Image by Callista Harper (Queensland Brain Institute)
In a review article about the relationship between brain structure and function published in the journal Behavioral Sciences, the authors state: “The main hypothesis is that the anatomic architecture conditions, but does not determine, the neural network dynamic. The functional connectivity cannot be explained only considering the anatomical substrate.” In other words, when researchers study the brain’s physical structure, they cannot completely explain the mechanisms that give rise to the brain’s functions, such as sensory perception, processing, or memory formation and storage. What researchers do understand, at least to a better degree, is which parts of the brain are involved in certain processes.
The function of the brain that is maybe the most mysterious is consciousness, which lies on the precipice of science and philosophy. I think, therefore I am, pondered René Descartes several hundred years ago about this very question. This idea, that the world we’re consciously perceiving in this very moment must be real since we believe we are experiencing it, is a question that is inextricably linked to the function of the brain but is one that is uniquely challenging because we are quite literally consciousness embodied investigating itself. Other research inquiries, such as into cures for neurocognitive conditions, are inquiries into brain dysfunction; research into consciousness is into one of the most fundamental, puzzling questions of human existence. To explain consciousness would be the brain explaining its own existence. The question of consciousness has earned the title of the “mind-body problem” with a history that goes back thousands of years. The crux of this question is whether the mental phenomena we experience are directly and only due to the physical anatomy of our brains or not.
Many questions remain about the most complicated object in the universe, but these questions are questions of fundamental importance to humanity for many reasons. First, there is something intrinsically important about understanding the three pound organ in our skulls that we use not only to perceive the world around us but to actually investigate the way it gives rise to our own ability to investigate these research questions. Our ability and desire to understand the world and continue trying to figure out our place in the universe and history is one of the most special parts of humanity. We seek the answers to these questions and I suspect that within every person, there is a desire to understand why we exist at all.
Aside from the philosophical rationale for these inquiries, they do have critical importance in the context of neurological conditions. As the research world seeks to understand how the anatomy of the brain causes the many complexities of functions its responsible for including consciousness, progress in understanding allows for a deeper understanding of the mechanism underlying dysfunction and abnormalities. Since many neurological conditions affect movement, sensory perception, memory, and cognition, a stronger understanding of how the brain’s anatomy contributes to its function will give researchers a much better position to understand the mechanisms of neurological conditions. Inevitably, a much better understanding of the mechanisms of the brain empowers researchers and clinicians to better prevent, diagnose, treat, and cure conditions.
As researchers, we seek to explain the world for many reasons, such as to reduce human suffering. In a universe where we have no idea if consciousness exists elsewhere, we are committed to understanding why our brains give rise to consciousness for many reasons, one of which is to illuminate the conditions that harm the organ that gives us that ability.
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