Plate Nº 27 · recorded October 7, 2026
Health & Medicine ResearchReported finding
Fruit Fly Brains Reveal How a Neural Gate Switches Memory On
NYU researchers showed how a gated circuit in the fruit fly brain writes and erases short-term memories of a smell's direction — confirming a long-suspected design for working memory.
By Marcus Bennett4 min read707 words
In brief
- The study was published online October 7 in the journal Nature.
- The fruit fly brain has fewer than 200,000 neurons, versus tens of billions in humans.
- Two neuron types, PFG and hΔK, form a 'split attractor network' gated by blocked communication.
- Flies tracked an apple cider vinegar odor for seconds after it disappeared, revealing the memory circuit.
- The paper is Aaron J. Lanz et al., Nature (DOI: 10.1038/s41586-026-11144-9).
A study published October 7 in the journal Nature has confirmed, for the first time in a working brain, a long-suspected circuit design that lets animals switch short-term memory on and off within seconds.
Researchers at NYU Langone Health made the discovery in fruit flies — an animal with fewer than 200,000 neurons, compared with the tens of billions in a human brain. Despite that simplicity, the fly brain's organization and the way its neurons communicate closely resemble our own.
"Our study shows how a neuronal circuit forms a short-term memory in response to a fly sensing an odor, enabling it to remember a direction and travel toward a smell it wants to remember," said study senior investigator Katherine Nagel, Ph.D., an associate professor in the Department of Neuroscience at NYU Grossman School of Medicine. "Scientists have long assumed an arrangement like this powers working memory, but our experiments confirm this arrangement exists and show how it works in a specific context."
Why working memory needs a switch
Working memory — the mental scratchpad that holds information for seconds at a time — faces a built-in design problem. It must be stable enough to hold a signal, yet flexible enough to start and stop quickly.
Think of briefly remembering a few digits of a security code. You need to activate that memory instantly. But holding on to every number you see all day would waste energy. Brains need a gate.
How do you test memory in a fly?
The fruit fly is a favorite tool of neuroscientists because its "connectome" — the complete map of every connection between its neurons — has been fully charted. Researchers can directly watch how specific neuron types interact to produce behavior.
In the new experiments, the team exposed flies to a whiff of apple cider vinegar. The flies walked toward the odor — and kept heading that way for a few seconds even after the smell vanished. While monitoring the flies' brains during this task, the researchers saw two types of neurons, called PFG and hΔK, respond to the smell with similar patterns of electrical activity, suggesting the cells work together to steer the fly.
What is a 'split attractor network'?
The two neuron types form what neuroscientists call an attractor network — a circuit in which a group of neurons effectively "talks" to themselves until a stable, self-sustaining signal emerges. But the fly's version has a twist.
Most of the time, communication between PFG and hΔK is blocked:
- With the block in place, PFG neurons simply track the fly's orientation in space, fed by the fly's internal "compass" system.
- When the block lifts and the two neuron types can exchange signals, the fly locks onto a goal — such as the source of an odor — and moves toward it.
The researchers call this arrangement a "split attractor network."
In this design:
- PFG neurons carry the content of the memory (where the fly is heading);
- hΔK neurons control the timing of memory formation;
- the communication block acts as the gate that opens and closes.
That split, the authors argue, delivers exactly the combination of stability and flexibility that working memory requires: a signal that persists once written, yet can be written and discarded rapidly.
What comes next?
The findings come from one circuit in one insect, so questions remain about how general this design is. "Right now, one of the frontiers in neuroscience is understanding what specific networks are doing, and the fruit fly is one of the best models to study that," Nagel said. "The fly has an amazing track record for revealing how human biology works in a clear and simple way. My hope is that it gives us insight into processes like working memory that we have not yet had the tools to study in depth."
Nagel's laboratory next plans to examine how the circuit is controlled across different time frames, characterize what information other neuron types are tracking, and work out why different brain regions can control similar functions at the same time.
The paper, led by Aaron J. Lanz and colleagues, appears as "A split attractor design for rapidly writing a navigational goal" in Nature (DOI: 10.1038/s41586-026-11144-9).
via Medical Xpress (Source)
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