Temporal processing in Drosophila melanogaster

Projektinformationen

TEMPRODROME

ID Finanzhilfevereinbarung: 101116996

DOI

10.3030/101116996

EK-Unterschriftsdatum 18 September 2023

Startdatum 1 Januar 2024

Enddatum 31 Dezember 2028

Finanziert unter

• European Research Council (ERC)

Gesamtkosten

€ 1 294 994,00

EU-Beitrag

€ 1 294 994,00

Koordiniert durch

MEDIZINISCHE UNIVERSITAT GRAZ
Austria

Periodic Reporting for period 1 - TEMPRODROME (Temporal processing in Drosophila melanogaster)

Berichtszeitraum: 2024-01-01 bis 2026-06-30

Zusammenfassung vom Kontext und den Gesamtzielen des Projekts

Any form of neural information processing, including our thoughts, perceptions, and plans for the future, depends on spatiotemporal patterns of electrical activity that propagate through neural circuits. The spatial component is simple to read out by taking a snapshot of neural activity at a given point in time. Temporal patterns, on the other hand, are more challenging to interpret, especially in systems that consist of millions or even billions of nerve cells.

We approach this problem by studying temporal signal processing in the brain of the fruit fly, which contains only approximately 150,000 neurons, whose connectivity and whose genetic identities are well-defined. This makes mechanistic ideas precise and testable. Like our brains, the fly brain processes temporal signals over at least nine orders of magnitude ranging from action potentials that last only milliseconds up to circadian rhythms and beyond. While the biophysical mechanisms that act at both ends of this spectrum are well characterised, little is known about the processes that operate at intermediate time scales from hundreds of milliseconds up to minutes.

Our work is based on the premise that nervous systems across species employ a common repertoire of circuit architectures to delay, accumulate, and store signals over this time range. Bridging biophysics and behaviour, we investigate three related brain functions that unfold over milliseconds up to minutes to uncover principles of how signals are kept in working memory: motion vision, perceptual decision-making, and distance estimation.

Arbeit, die ab Beginn des Projekts bis zum Ende des durch den Bericht erfassten Berichtszeitraums geleistet wurde, und die wichtigsten bis dahin erzielten Ergebnisse

The project has made progress in understanding all three brain functions under investigation.

In both the human retina and the optic lobe of the fly brain, neural circuits that compute the direction of visual motion involve temporal filters that store information for up to several hundred milliseconds. Using in vivo patch-clamp recordings, a virtual reality setup, and genetic techniques to label endogenous proteins, we identified distinct ion channels that define neural filter time constants in this time range. In a series of behavioural experiments, we show that these filters critically influence how animals perceive visual motion.

Postsynaptic to motion-sensitive neurons, we discovered a network that integrates motion information over multiple seconds in the lead-up to a perceptual judgement. Targeted optogenetic control of neural activity enabled us to manipulate the animals’ reaction times in a decision-making task and pinpoint the neural substrate of an integrator of visual evidence.

In the central complex, we delineated a neural circuit that integrates distance over minutes. Informed by connectomic data, we screened populations of neurons putatively involved in computing and storing distance information during navigation. Our screening assay identified two distinct types of neuron with strong reciprocal connections whose activity is required for the formation of a distance memory.

Fortschritte, die über den aktuellen Stand der Technik hinausgehen und voraussichtliche potenzielle Auswirkungen (einschließlich der bis dato erzielten sozioökonomischen Auswirkungen und weiter gefassten gesellschaftlichen Auswirkungen des Projekts)

Mechanisms of working memory are diverse, but likely conserved throughout evolution. Up until now, this project has discovered cellular and molecular components that allow neural circuits to manipulate signals in time by delaying, accelerating, and storing them for milliseconds up to minutes. Further research will investigate the precise mechanisms underlying these computations and make them amenable to treatment.