How many neurons does a fruit fly brain have?
About 140,000. In 2024 scientists finished mapping every one of them in one adult fruit fly’s brain, with more than 50 million synapses between them.
A fruit fly’s brain is smaller than a poppy seed and holds about 140,000 neurons. A human brain has hundreds of thousands of times more. Even so, the fly’s brain lets it fly, find food, learn smells, and escape a swatter.
A complete map of a nervous system, with every neuron and every synapse, is called a connectome. The fruit fly is one of very few animals whose whole brain has been mapped this way. The WiredMind lessons run on a different, later map: the connectome of one male fly’s brain and nerve cord, and each lesson uses a circuit of 3,000 to 4,500 of its neurons.
See it in a lesson
Key terms
- Neuron
- A nerve cell. It receives signals from other cells and, when enough of them add up, sends a signal of its own.
- Synapse
- The junction where one neuron passes its signal to the next. The more synapses two cells share, the stronger the link between them.
- Connectome
- A complete wiring diagram of a nervous system: every neuron and every synapse between them. The lessons run on the connectome of one real fruit fly.
- Neural circuit
- A group of neurons wired together to do one job, such as recognizing a smell or setting off a jump.