PFN neurons
systemNavigationspeciesD. melanogaster3D view3 of 626 cellssources4
PFN neurons are columnar neurons of the fruit fly’s central complex that connect the protocerebral bridge, the fan-shaped body and the noduli. They combine the fly’s heading with self-motion signals, a step in computing the direction in which it is travelling.
| Also known as | P-FN neurons · Protocerebral bridge–fan-shaped body–noduli neurons · PFNa · PFNd · PFNm · PFNp · PFNv |
|---|---|
| Region | Central complex: protocerebral bridge, fan-shaped body and noduli |
| System | Navigation |
| In the display bundle | 3 of the 626 reconstructed neurons in the site’s MaleCNS display bundle, which shows 626 of the model’s 166,700 neurons: PFNa 1, PFNp 2 |
What they are
The complete connectome of the central complex describes several PFN types, including PFNa, PFNd, PFNm, PFNp and PFNv, which differ in the fan-shaped body layers they innervate and in the noduli inputs they receive (Hulse et al., 2021).
What they do
As a fly walks, PFNd and PFNv neurons conjunctively encode its translational velocity and its heading: velocity signals from locomotor brain regions are multiplied with heading signals from the compass system. Downstream hΔB neurons pool their output into a world-centred representation of translational velocity (Lu et al., 2022).
A related study found a signal in the fan-shaped body that tracks the fly’s travelling direction relative to external cues, and described a circuit that computes it by adding vectors represented as sinusoidal patterns of activity across neuronal populations (Lyu et al., 2022).
Ventral PFN types, which include PFNa, PFNm and PFNp, are tuned to the direction of airflow, with cells in each hemisphere tuned to 45° on their own side (Currier et al., 2020). Imaging experiments suggest that ventral PFNs inherit this tuning from neurons that bring input from the lateral accessory lobe to the noduli (Currier et al., 2020).
Behavior
Perturbing PFNd neurons disrupts path integration based on self-motion in walking flies (Lu et al., 2022), and silencing ventral PFNs prevented flies from making appropriate corrective turns after the airflow direction changed (Currier et al., 2020).