Howard Hughes Medical Institute-led research has uncovered three neural circuit mechanisms that enable female fruit flies to modify their visual processing during aggressive interactions.
Neuronal circuits responsible for detecting and relaying visual features are well-studied. Previous studies in primates, rodents, and invertebrates have demonstrated the importance of neurons tuned to specific visual features, such as size, speed, and color. Extracting the neural mechanisms underlying state-dependent visual attention based on changing goals or environmental conditions has remained elusive.
With its genetic accessibility, detailed neural connections, and observed complex behaviors, the fruit fly provides a powerful system for investigating state-dependent visual processing.
In a study, "Social state alters vision using three circuit mechanisms in Drosophila," published in Nature, researchers analyzed the fruit fly Drosophila melanogaster to map its neural connections to identify circuit motifs that alter visual processing in aggressive females.
They employed cell-type-specific genetic tools, behavioral assays, and neurophysiological analyses to demonstrate the role of these circuits in modulating visual attention during aggression.
Three distinct circuit mechanisms identified
First, the convergence of excitatory inputs from neurons conveying select visual features and internal states allows for enhanced visual and state information integration. This mechanism involves neurons known as lobula columnar (LC) neurons, which project visual information from the optic lobe to the central brain.
Second, dendritic disinhibition of select visual feature detectors increases the responsiveness of specific visual neurons during aggression. This involves relieving inhibition on the dendrites of LC10-group neurons in the lobula, enhancing their ability to detect fly-sized moving objects.
Third, a toggle switch mechanism shifts visual processing between two types of visual feature detectors, LC10a and LC10c neurons. Depending on the social context, this switching enables the fly to prioritize relevant visual cues, such as aggression or courtship.
Researchers also discovered that elements of this toggle switch operate in male fruit flies during courtship pursuit, suggesting that different social behaviors may share common circuit mechanisms. The findings imply that a single neural node differing across sexes can regulate multiple shared sensorimotor circuits.
The study reveals circuit mechanisms involved in dynamic sensory processing, advancing our understanding of how internal states utilize context to influence perception.