Historical views of the brain reflect the biases of the time.

The industrial age spawned mechanical explanations for the brain.

Today, a new concept of the brain is well adapted to explaining and responding to 21st-century challenges.

Displayed on a wall in my study is a diagram taken from a children’s encyclopedia dating from the 1930s. It’s labeled “The Central Control Station of Your Body,” and consists of a cutaway view of the skull, which houses a series of rooms occupied by one or more well-dressed men in the business suits popular at the time.

In the different rooms, the workings of the brain are illustrated by drawings of the men carrying out various tasks. The caption reads, “Imagine your brain as the executive branch of a big business. It is divided into many departments. Seated at the big desk in the headquarters office is the General Manager—Your Conscious Self—with telephone lines running to all departments.”

Today, it’s easy to ridicule such a simplistic, sexist view of how the brain works. Why are only men depicted? Nor do most of us experience ourselves as a general manager issuing orders to compliant underlings. In addition, our “conscious self” is not always in control, delegating orders to other areas of the brain. For instance, just a moment ago, I walked across the room to pour myself an iced tea. I was conscious of wanting the cooling beverage, but can’t provide anything but the most elementary description of how my nerves and muscles enabled me to walk to the pitcher.

Despite the amusement kindled by the children’s diagrams depicting the brain as a corporate organization, it nonetheless illustrates an accepted principle of brain operation: localization (specific brain areas dedicated to designed tasks).

Severe damage to the occipital lobes, for instance, results in a form of blindness secondary to obliteration of the visual areas, which correspond to what the localizationists refer to as the “visual center” for the brain. Dysfunction anywhere in the long circuitous pathway uniting the eye, brain, brainstem, and cerebral cortex also produces various forms of visual deficit, but not usually permanent blindness.

As a rule, the more a brain function is distinguishable from an elemental form of sensation (seeing, hearing, etc.), the less localizable and more distributed its function within the brain. Emotions, for instance, largely emanate from the so-called limbic system, but that structure occupies a vast amount of real estate. As a result, specific emotional states of mind, such as elation or despair, do not emanate from centers and therefore cannot be pinpointed or localized.

Overall, the brain’s functions are related to the number of neurons and their interconnections, with behavior resulting from a culmination of activity from many, many nerve cells linked together. Here are the key concepts: 1) each nerve cell is unique, and 2) function is dependent on transmission across the synapse (the tiny gap between nerve cells) of many different messenger chemicals (neurotransmitters).

But the brain is never conclusively explained; an air of mystery always remains. For instance, at any given moment, one cannot be certain which neuron may be influencing another, and even more important, no one can know how many connections a particular neuron may make. So how might we go about modeling something like that, you may ask.

I think a good place to learn about the brain is in the kitchen. Why the kitchen? It offers a deeply metaphorical comparison with the brain. Select a high-quality pasta designated for spaghetti. Put half of the pieces aside. Cut the contents of the other half of the box, approximately equally, into split pieces and pieces broken into three parts.

Now cook the spaghetti al dente (firm) and pour it into a colander. After it’s cooled for a minute, thoroughly mix the strands.

Now insert a cooking tong deep down into the mix, select a single strand (spaghetto) and begin to remove it, but very slowly. At first, you’ll have no idea of the length of the selected strand, nor any idea of how many of the other strands it may have previously been in contact with. Some of the longer strands have made connections with far distant strands. The longer the strand, the greater the possibility of potential contacts. The word for our spaghetti concoction is connectome. Every strand is at least potentially in contact with many others, either directly or via intermediary strands, for a total of many, many connections, the majority of them unknown. How many connections might that be? There is literally no way of telling.

Starting in the 2000s, neuroscientists suggested that the human brain, like our spaghetti metaphor, is best described as a connectome.

In 2005, Olaf Sporns and Patric Hagmann independently applied the word connectome to the brain. “One could consider the brain connectome, set of all neural connections, as one single entity, thus emphasizing that the huge brain neural communication capacity and computational power critically relies on this subtle and incredibly complex connectivity architecture.”

Thanks to the findings of the Human Connectome Project, launched in 2009 at NIH, neuroscientists have become increasingly confident that, as Sporns and Hagmann put it, “High connectivity alone appears to form an essential part of the structural backbone of the brain.”

How many connections might be involved? To put that question into perspective, consider the 1 mm-long roundworm, which contains only 302 neurons but forms about 7,000 connections. Compare that to our brain of 86 billion neurons organized into a network of circuits that are interconnected by short and long-range pathways.

To further appreciate the complexity involved in all of this, bear in mind that not all neurons operate identically: Some facilitate transmission while others inhibit it; a given neuron may use any one or more of an estimated 100 neurotransmitters, along with small molecular messengers which also facilitate nerve impulses.

At this point, just past the first quarter of the 21st century, connectomics as a structural-functional model of the brain promises to lead to a new and more encompassing understanding of the organ.

In addition, the connectomic brain model may provide potential solutions for some of the unique problems that we are now encountering in the world.

Damoiseaux JS, Greicius MD (October 2009). "Greater than the sum of its parts: a review of studies combining structural connectivity and resting-state functional connectivity." Brain Structure & Function. 213 (6): 525–533. https://pubmed.ncbi.nlm.nih.gov/19565262/

Dorkenwald S, Matsliah A, Sterling AR, Schlegel P, Yu SC, McKellar CE, et al. "Neuronal wiring diagram of an adult brain." Nature. 634 (8032): 124–138 October 2, 2024. https://doi.org/10.1038/s41586-024-07558-y

Sadaghiani S, Brookes MJ, Baillet S. "Connectomics of human electrophysiology." NeuroImage. 247 118788. February 15, 2022. https://www.sciencedirect.com/science/article/pii/S1053811921010600?via%3Dihub

Sporns O, Tononi G, Kötter R. "The Human Connectome: A Structural Description of the Human Brain.” PLOS Computational Biology 1(4): e42, 2005. https://doi.org/10.1371/journal.pcbi.0010042

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