Table of Contents
Researchers have gained new understanding of how the brain of the fruit fly creates spatial representations that support navigation.
By Alice Roberts | WASHINGTON – 2025/08/26 10:56:19
a, HD cells (EPG neurons) form a ring attractor network in the EB. Their axons project to the PB, where they form two linearized topographic maps of HD. b, The position of the EPG activity bump is influenced by ER neurons that encode the positions of visual HD cues or the direction of the wind. ER neurons are inhibitory and the most active ER neurons push the bump to the location where their inhibitory output is minimal. ER → EPG connections are anatomically all-to-all but their weights are shaped by hebbian plasticity at ER → EPG synapses, such that each ER neuron generally makes functional synapses onto only a subset of EPG neurons. c,Schematic ER → EPG weights.Given a single visual cue and a steady wind direction, associative LTD is predicted to produce a diagonal notch of weak connections in each weight matrix. EPG neurons are sorted by their preferred HD. ER neurons are sorted by their preferred cue position. If the two cues are aligned in the simulated habitat, Hebbian plasticity should align the notches. d, We hypothesize that cue salience and stability affect bump attractor dynamics and learning. e, We image EPG neurons in head-fixed flies walking on a spherical treadmill. as the fly turns on the spherical treadmill, the virtual environment rotates around the fly in the expected direction. Here,the environment contains a shining vertical stripe that serves as an HD cue. f, The bump of EPG activity tracks the fly’s fictive HD in a virtual reality environment, with a relatively constant angular offset. Bump position rotates clockwise in the EB (imaged from the posterior side of the head) as HD rotates counterclockwise; therefore, to account for this directionality, we always plot (−HD) to make it easier to visualize the correspondence between bump position and HD. Credit: Basnak et al. (Nature human Behavior, 2025).
A recent study published in Nature Neuroscience (2025) sheds light on how the brains of fruit flies generate spatial representations that facilitate navigation. The research, led by Melanie A. Basnak and colleagues, delves into the neural mechanisms that allow these insects to orient themselves in their environment.
The study focuses on the role of head direction (HD) cells, specifically EPG neurons, which form a ring attractor network in the ellipsoid body (EB) of the fruit fly brain. These neurons project to the protocerebral bridge (PB), creating two linearized topographic maps of HD. The position of the EPG activity bump, which represents the fly’s current HD, is influenced by ER neurons. These ER neurons encode the positions of visual HD cues or the direction of the wind.
Neural Connections and Environmental Cues
“The bump of EPG activity tracks the fly’s fictive HD in a virtual reality environment,with a relatively constant angular offset.”
ER neurons are inhibitory,and their activity affects the position of the EPG activity bump. The most active ER neurons push the bump to the location where their inhibitory output is minimal. The connections between ER and EPG neurons are anatomically all-to-all, but their weights are shaped by Hebbian plasticity at ER → EPG synapses. This means that each ER neuron typically forms functional synapses onto only a subset of EPG neurons.
The researchers hypothesize that cue salience and stability affect bump attractor dynamics and learning. They used head-fixed flies walking on a spherical treadmill to image EPG neurons. As the fly turns on the treadmill, the virtual environment rotates around the fly in the expected direction. The virtual environment includes a bright vertical stripe that serves as an HD cue.
virtual Reality Experiments
The experiments revealed that the bump of EPG activity tracks the fly’s fictive HD in the virtual reality environment, with a relatively constant angular offset. The bump position rotates clockwise in the EB (imaged from the posterior side of the head) as HD rotates counterclockwise.
Frequently Asked Questions
- What are head direction cells?
- Head direction cells are neurons that fire when an animal’s head is facing a particular direction. They play a crucial role in spatial orientation and navigation.
- What is a ring attractor network?
- A ring attractor network is a neural circuit that maintains a stable representation of a continuous variable, such as head direction. It allows the brain to keep track of the animal’s current heading even in the absence of external cues.
- how do fruit flies use visual cues for navigation?
- Fruit flies use visual landmarks and other cues to orient themselves in their environment. These cues are processed by ER neurons, which then influence the activity of head direction cells to update the fly’s internal representation of its heading.
