A temporally restricted function of the dopamine receptor Dop1R2 during memory formation

The dopamine receptor Dop1R2 plays a crucial role in the formation of longer-lasting memories, while it is dispensable for short-term memories.

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Individual dopaminergic neurons induce unique, yet overlapping combinations of behavioural modulations including safety learning, memory retrieval and acute locomotion

Two evolutionary highly conserved functions of dopamine are to carry "teaching" signals during associative learning and to control movement. In mammals and humans these functions are generally thought to be produced by different populations of neurons. Here, we investigated in the larva of Drosophila melanogaster whether both these functions can be induced by the same individual dopaminergic neurons in the central brain. Focusing on the dopaminergic neurons of the DL1-cluster, we asked whether the optogenetic activation of individual neurons established associative punishment and/or safety memories, controlled the retrieval of the established memories, and acutely modulated locomotion. We found that each neuron had a unique, yet overlapping set of behavioural effects. Several individual neurons both established a memory and modulated acute locomotion by increasing the animals' bending and decreasing its velocity. Our results demonstrate that individual dopaminergic neurons can fulfil a surprisingly broad range of functions in different behavioural contexts. Given the highly conserved roles of the dopaminergic system across the animal kingdom, this study raises the question whether a similarly diverse functionality can be found also in other animals, including humans. ### Competing Interest Statement The authors have declared no competing interest.

Odour representations supporting ethology-relevant categorisation and discrimination in the Drosophila mushroom body

Neural representations of sensory stimuli serve multiple distinct purposes, from the rapid recognition of familiar environments, to the precise identification of individual salient cues. In the insect mushroom body (MB), odours are encoded by the activity of Kenyon cells (KCs). The random wiring of olfactory projection neurons (PNs) and KCs in the MB calyx is thought to enhance odour discrimination. Here, we examined the impact of deviations from random wiring and demonstrated their significant roles in shaping odour representations. We confirm that different KC types have distinct PN input biases correlated with the contextual relevance of the odour information delivered by the PNs. By recording the functional responses of different KC types to ethologically defined odour categories, we found that the αβ and α'β' KCs produce segregated representations of relevant odour groups, potentially enhancing the categorisation of odours based on ethological relevance. Simultaneously, these same KC types displayed distinct representations for food-related odours, supporting precise discrimination. In contrast, γ KCs lacked significant segregation of odour representations by ethological category. Computational simulations refined with our functional data indicated that the specific PN input connection pattern of individual KC types largely accounts for the observed representations. Taken together, we propose that individual KC types process odour information with distinct objectives, supporting both ethological categorisation and discrimination. ### Competing Interest Statement The authors have declared no competing interest.