Repercussions of the first complete map of the insect brain

Recently, the academic journal Science published the first comprehensive map of all the circuits and connections between neurons (“connectome”) in an insect brain. But not of any insect, but of the larva of the fruit fly (Drosophila melanogaster), one of the most used animal models in laboratories around the world to carry out studies of genetics, embryonic development and neuroscience that allow us to know more. about how the human brain works.

To understand the scope of this scientific milestone that determined, among other things, that at this stage the Drosophila brain contains 3,016 neurons and 548,000 synaptic connections, the CyTA-Leloir Agency consulted José Manuel Duhart, a researcher at the National Research Council, on various questions. Scientific and Technical (CONICET) in the Behavioral Genetics Laboratory of the Leloir Institute Foundation (FIL), in Argentina all these entities.

The biotechnologist with a PhD in Science and Technology, who on his social networks graphs his status as “sucking Drosophilas”, has been working with this insect since 2015 to try to understand the neural mechanisms that set the rhythm of the biological clock, in charge of synchronizing the passage of the day. and night, and how various motivational factors impact sleep regulation.

“The results of this study allow us to have a first hyper-detailed map of how all the neurons in a brain are connected. This information will make it possible to generate hypotheses about how a neural circuit (a group of neurons connected in a specific way) is capable of generating or sustaining complex functions such as learning and forming memories”, summarized Duhart. And he added: “Although the complexity of our brain is extremely greater, both in number of neurons and in the repertoire of functions that it is capable of performing, it is hoped that the general rules that we learn from these less complex organisms serve as a framework to accelerate understanding of our biology.

The study carried out by scientists from the universities of Cambridge (United Kingdom) and Johns Hopkins (United States) was based on images obtained by electron microscopy with a very high level of resolution. This made it possible to identify characteristic structures of the connections between neurons and to reconstruct which neuron communicates with which other and, furthermore, in what “direction” this communication occurs.

José Manuel Duhart holding tubes that house Drosophila larvae. (Photo: CyTA-Leloir Agency)

For Duhart, beyond the technical challenge and the usefulness of the new data for future research, “there are findings that are really surprising.” And he explained: “It was observed that neurons can receive information in structures that are not generally associated with that purpose, such as axons, and that they can send it from structures that were not associated with that role either, such as dendrites.” Although he acknowledged that this had already been described in some particular regions of the brain, “now it seems to be a phenomenon extended to the whole organ,” he said.

Another interesting point, he mentioned, is that there is a high level of recurrence in brain connectivity: around 40% of neurons are capable of “replying” to others that send them information. “The neurons that are part of the learning center of the brain are among those with the highest degree of recurrence. This network architecture resembles models used in artificial intelligence,” said the expert. And he continued: “Perhaps our greater understanding of the functioning of simple organisms can help to optimize and generate new computational models.”

From this very detailed map, scientists will be able to extract general models about how a network of neurons is organized to manage to enter information or inputs and generate actions or memories from them. “In addition, knowing how the circuits work to perform these tasks lays the foundation for understanding what is going wrong in pathological situations, and eventually devising better research strategies to find treatments,” Duhart explained.

more than a fly

Because it shares many biological processes with humans, Drosophila melanogaster is an excellent model for research on general principles of cell biology, genetics, embryonic development, and brain function in general. This is added to the fact that it is a small animal, easy to raise and maintain and with a short life cycle. In any case, great caution must be taken when extrapolating the results found in the fly to humans, as Duhart warns.

Lastly, the scientist highlighted another important aspect behind the use of this animal model: “Drosophila may also be useful to accelerate our understanding of the biology of other invertebrates, something that has an impact on the well-being of the planet. For example, most pollinating species are insects and various factors –such as the intensive use of pesticides and climate change– have led to a decline in their numbers. Now we will be able to accelerate knowledge about how these factors impact the physiology of insects in order to design palliative strategies, or help diagnose the causes of their decline.” (Source: CyTA-Leloir Agency)