Counting connections in a tiny brain

This exercise is a part of Educator Guide: The Fruit Fly Brain in Exquisite Detail / View Guide

Directions for teachers: Ask students to read the online Science News article “Scientists have mapped an insect brain in greater detail than ever before” and have them answer the following questions. A version of the article, “The fruit fly brain in exquisite detail,” appears in the April 22, 2023 issue of Science News.

1. What is a neuron, and what is a synapse?

Neurons are nerve cells, and synapses are the connections between neurons.

2. In your own words, explain what neuroscientist Marta Zlatic and her colleagues accomplished.

Neuroscientist Marta Zlatic and her colleagues mapped the location of every neuron and its connections in the larval fruit fly brain.

3. What methods did the researchers use to conduct their research? How long did the research project take?

The scientists used images taken by an electron microscope to find the neurons, and then they put the images together to follow the neurons. Using the information they gathered from the images, the scientists were able to create a 3-D version of the neurons. The work took 12 years.

4. How many neurons and synapses did the researchers map in the larval fruit fly? What do you think it means that there are more synapses than neurons?

The researchers mapped 3,000 neurons and approximately 550,000 synapses.  I think having more synapses than neurons shows that an individual neuron can connect to many nerve cells instead of just being able to connect to one other neuron.

5. Visualizing a living system is difficult. How did the scientists present their findings to make their findings easier to understand?

The scientists used brightly colored spheres to depict the nerve cells and bright, stringy tails to show the branches off the nerve cells that send and receive signals.

6. Why did the scientists use larval fruit flies instead of adult fruit flies in their neuron study?

Larval fruit flies were used because their brains are smaller than adult fruit flies, which sped data gathering.

7. Many scientists use fruit flies in their research. Why do you think scientists consider fruit flies a good model organism to study? How was the fruit fly useful in Zlatic’s study?

Scientists use fruit flies as a model organism because the flies do some of the same things we do, like sensing and learning. In Zlatic’s research, it was advantageous to study the fruit fly because its brain is small. Doing this study on a larger animal’s brain would have taken much longer.