An Intro To The World of Connectomics

6 min readFeb 3, 2021

The brain is a miraculous organ, and that's not a secret to anyone. Our brains may only be 3 pounds, however, it's the powerhouse of intelligence, interpretation, initiating body movement, and is the steering wheel that controls all of our behaviours.

Although the brain is one of the most important organs within all living organisms, neuroscientists still don’t understand nor can comprehend how some components within the brain work. If neuroscientists don’t even fully comprehend how information is processed within the brain of a tiny worm with a few hundred neurons, we shouldn’t be surprised that the human brain with 80–100 billion neurons, is still a mystery to us.

What if we want to ask more questions about brain activity? Like how neurological disorders, such as Alzheimer’s and ADHD develop?

Through the study of connectomics, we can ask better questions about specifics within the brain.

Put simply, connectomics is the study of the brain’s structural and functional connections between different cells. This correlation is visualized as a connectome, referring to a set of connections within the brain.

In this article, I’ll be giving you an overview of the world of connectomics.

Brain Communication

In order to understand connectomics, we need to have a basic understanding of communication within the brain.

I don’t know about you, but when I hear really good music, I automatically start dancing. I don’t care where I am, good music calls for a dance party at any moment.

When someone throws a ball at me, my first instinct is not to dodge it, but rather run towards the ball and catch it.

Occasionally, when my mother asks me to put away my dishes, I run downstairs to put them away before my mother gets annoyed at me.

How do we instinctively know how to do these tasks?

The brain is made up of billions of cells referred to as neurons.

These neurons carry information that consists of electrical pulses, and whenever you perform any action, neurons in your brain fire off.

A neuron has branches that look like a tree, and they are called dendrites. The dendrites receive signals, and a longer projection that looks like a tree trunk, called the axon, sends signals.

These electrical pulses can jump from neurons to neurons through the use of the nerve releasing chemical signals called neurotransmitters.

At the end of the axons, we can find synapses that act as a channel for neurons to communicate. The neuron transmitters will then use the synapses as a tunnel to travel from different neurons, creating new electrical waves where it travels.

The Connectome

The connectome is a comprehensive map of the neural connections within the brain of an organism. It’s often thought of as a wiring diagram that maps all the neural connections within the nervous system of an organism. A connectome can refer to the mapping of a brain of an entire organism, or the mapping of brain subsystems, such as hippocampal connectomes, thalamic connectomes, or cortical connectomes.

Currently, the only organism that we have a complete connectome for is C. elegans , which is a one and a half millimetre organism. This organism has a very small neural network, consisting of around 300 neurons and around 7,000 synaptic connections.

Construction of the C. elegans connectome took a very long time and involved very tedious scientific manpower. Every individual neuron was identified, located, and traced, just through manual visual recognition. This means that individual scientists had to follow the organism’s neuronal pathways with their own vision, and the convoluted paths were tracked through many microscopic images.

Unsurprisingly, the human brain is far more complicated in comparison to the brain of C. elegans. In fact, our brains have 80–100 billion neurons and an estimated amount of 700 trillion synaptic connections. Today, completing the human connectome is out of our reach due to the existing technology we have. The first reason is that there aren’t enough electron microscopes in existence to make imaging of the large amounts of tissue in our brains feasible. Second, interpreting these images and tracing projections from each neuron is still carried out through humans clicking through images, which is not efficient what so ever.

If we want to accomplish building a single human connectome, we will need many electron microscopes and artificial intelligence that can accomplish the task of visually tracing neuronal projections and recognizing and recording synaptic connections.

Although there are possible challenges related to mapping the human connectome, there are many opportunities that create optimism for this possibility.

Electron microscopy is rapidly improving and decreasing in cost, and there is a promising future of faster and stronger prototypes of these microscopes. Additionally, artificial intelligence is being pursued in many labs to accomplish the tedious task of visualization that comes with mapping a connectome.

The Importance of Constructing a Human Connectome

Human mental behaviour, such as intelligence (general abilities), depression, ADHD, and schizophrenia are hypothesized to be related to different parts and features of the human brain. Currently, we lack the tools necessary to investigate such theories. However, once we can fully construct human connectomes, scientists and doctors will solve many mysteries related to the correlation between our brain structure and abilities and behaviours. By comparing wiring diagrams of different human brains, it is likely that with this information, we will be able to develop target treatments such as better drugs, neural prostheses, and different surgical practices.

Key Takeaways 🔑

connectomics is the study of the brain’s structural and functional connections between different cells
This correlation is visualized as a connectome, referring to a set of connections within the brain
Neurons communicate with each other through neurotransmitters, and synapses allow signals to pass from one neuron to another
The connectome is a comprehensive map of the neural connections within the brain of an organism
Currently, the only organism that we have a complete connectome for is C. elegans
scientists followed C. elegans neuronal pathways with their own vision, and the convoluted paths were tracked through many microscopic images
our brains have 80–100 billion neurons and an estimated amount of 700 trillion synaptic connections
completing the human connectome is out of our reach due to the existing technology we have
to construct a single human connectome, we will need many electron microscopes and artificial intelligence
there is optimism in terms of developing a human connectome because microscopes are improving and becoming cheaper, and A.I. is being used in connectomics
once we can fully construct human connectomes, scientists and doctors will solve many mysteries related to the correlation between our brain structure and abilities and behaviours