Our Neurons’ Electrical Synapses Are the Dark Matter of the BrainThese aren’t the familiar chemical synapses but a second set, the electrical synapses that enable currents to travel directly between neurons from pore to pore.
The universe has its dark matter, the 23% of matter that we know is out there but can’t see because it emits no light. The brain has its own “dark matter” too, in the form of electrical synapses.
These are not the chemical synapses by which neurons transmit a stimulus from one cell to the next. They are a second layer of synapse that allows message-carrying currents to flow passively from one neuron to another through pores in the neurons’ cell walls.
They are likely important because just about every type of animal except echinoderms (starfish and sand dollars, for example) has them — and yet we don’t know much about them:
”Electrical synapses are much rarer and are hard to detect with current methods. That’s why they have hardly been researched so far,” explains Georg Ammer, who has long been fascinated by these hidden cell connections. “In most animal brains, we therefore don’t know even basic things, such as where exactly 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 revealed something interesting though:
To track down these functions, Ammer and his two colleagues, Renée Vieira and Sandra Fendl, labelled an important protein building block of electrical synapses. In the brain of fruit flies, they were thus able to show that electrical synapses do not occur in all nerve cells, but in almost all areas of the brain. By selectively switching off the electrical synapses in the area of visual processing, the researchers could show that the affected neurons’ reaction to certain stimuli is much weaker. Furthermore, without electrical synapses, some nerve cell types became unstable and began to oscillate spontaneously.
“The results suggest that electrical synapses are important for diverse brain functions and can play very different functional roles, depending on the type of neuron,” Ammer summarizes. “These synapses should therefore also be integrated in 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)
The paper is open access.
Fruit flies are a popular study subject in brain research because they have only about 200,000 neurons. A rodent, by contrast, has 12 billion neurons, making science hypotheses much harder to test. And, as for the human brian, well, human neurons, besides numbering in the 86 billion range, are different from and much more efficient than rodent ones. So for testing basic ideas, it is better to stick to fruit flies.
One outcome of a science focus on the fruit bowl pests has been some interesting discoveries about even their simple brains. For example, a single fly neuron can do complex math. The flies use complex strategies for getting the most out of very small brains. In fact, in certain types of tasks, like odor detection, the flies outperform computers. Of course, that might not be so surprising; odors matter a good deal more to fruit fly than to a computer…
And our journey through the brain has hardly begun.
*Note: Oddly enough, the human brain and the universe are remarkably similar in many ways. It looks as though the universe is not random but rather patterned in the way it unfolds. When an astrophysicist and a neurosurgeon compared notes, they were surprised by the way the brain follows the same pattern as the universe.
You may also wish to read: Memory leans more on the brain’s electric field than on neurons. MIT researchers compare the electric field to an orchestra conducting the neurons as players. The neurons associated with our memories may change; it’s the electric field that holds the memories together, the neuroscientists say.
The brain unfolds like a drama, with neurons in different roles. Researchers studying fruit flies hope that spotting the stages at which human neurons go missing or wrong can help develop treatments to insert or replace them. Human and fruit fly brains are strikingly similar but with vastly different results. Clearly, the brain is not all we need to know about a life form.