The electrical synapses of our neurons are the dark matter of the brain

The universe has its dark matter, the 23% of matter we know is there but we can’t see it because it doesn’t emit any light. The brain also has its own “dark matter”, in the form of electrical synapses.

They are not the chemical synapses through which neurons transmit a stimulus from one cell to another. They constitute a second layer of synapse that allows currents carrying messages to flow passively from one neuron to another through the pores of the cell walls of the neurons.

They’re probably important because just about every type of animal except echinoderms (starfish and sand dollars, for example) have them – and yet we don’t know much about them:

“Electrical synapses are much rarer and harder to detect with current methods. This is why they have hardly been studied so far,” explains Georg Ammer, who has long been fascinated by these hidden cellular connections. “In most animal brains, therefore, we don’t even know the basic things, such as exactly where electrical synapses occur or how they influence brain activity.”

News“The dark matter of the brain” at Max Planck Gesellschaft (April 5, 2022)

Ammer’s team’s recent study of fruit fly brains, however, revealed something interesting:

To track these functions, Ammer and her two colleagues, Renée Vieira and Sandra Fendl, tagged an important protein component of electrical synapses. In the brain of Drosophila, they were able to show that electrical synapses do not occur in all nerve cells, but in almost all areas of the brain. By selectively turning off electrical synapses in the visual processing area, researchers could show that the reaction of affected neurons to certain stimuli is much weaker. Additionally, without electrical synapses, certain types of nerve cells became unstable and began to oscillate spontaneously.

“The results suggest that electrical synapses are important for various brain functions and can play very different functional roles, depending on the type of neuron,” summarizes Ammer. “These synapses should therefore also be incorporated into connectome studies.” The connectome is a map of all neurons and their connections in a brain or brain area.

News“The dark matter of the brain” at Max Planck Gesellschaft (April 5, 2022)

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Fruit flies are a popular study subject in brain research because they only have about 200,000 neurons. A rodent, on the other hand, has 12 billion neurons, which makes scientific hypotheses much harder to test. And, when it comes to the human brian, well, human neurons, in addition to being 86 billion in number, are different and much more efficient than those of rodents. So to test the basic ideas, it is better to stick to fruit flies.

One of the results of a scientific focus on fruit cup pests has been some interesting discoveries even about their simple brains. For example, a single fly neuron can do complex calculations. Flies use complex strategies to make the most of very small brains. In fact, in some types of tasks, such as smell detection, flies outperform computers. Of course, that might not be so surprising; smells matter a lot more to the fruit fly than to a computer…

And our journey into the brain has only just begun.

*To note: Curiously, the human brain and the universe are remarkably similar in many ways. It seems the universe is not random but rather patterned in the way it unfolds. When an astrophysicist and a neurosurgeon compared notes, they were surprised at how the brain follows the same pattern as the universe.

You can also read: Memory relies more on the electrical field of the brain than on neurons. MIT researchers liken the electric field to an orchestra driving neurons as players. The neurons associated with our memories can change; it’s the electric field that holds memories together, say neuroscientists.


The brain unfolds like a drama, with neurons in different roles. Researchers studying fruit flies hope that pinpointing the stages at which human neurons disappear or become deregulated can help develop treatments to insert or replace them. The brains of humans and fruit flies are strikingly similar, but with very different results. Obviously, the brain is not all we need to know about a life form.