Drosophila, larva, mushroom bodies, calyx, olfaction, circuitry, calcium imaging
Organisms with brains can discriminate with high specificity among an enormous range of sensory stimuli – humans even have neurons that respond to individual celebrities! The initial representation of sensory stimuli is broad and distributed across many channels but transformed into highly specific and sparse representations in the higher brain. To study this process in a simple system with powerful genetic tools, I am interested in the circuitry of odour discrimination and olfactory memory formation in Drosophila.
We have therefore generated a sensory map of odor specificities for the antennal lobe (the first olfactory centre) and the mushroom body calyx (a secondary olfactory center essential for memory), using the simple larval olfactory system as a model. Imaging of larval brains using genetically encoded calcium indicators reveals the maps of olfactory information in both olfactory centres, with only a limited spread of activity as information passes through the circuitry. This movie shows a single glomerulus active in both bilateral calyces of the mushroom bodies, upon odor stimulation of larvae that have only a single functional olfactory receptor.
We are now interested in the following questions:
- What is the circuitry that generates sparse representations of odours in the mushroom bodies?
- How do sparse odor representations associate with other sensory stimuli?
We combine targeted gene expression to identify and manipulate the neuronal circuitry, calcium imaging to monitor the function of identified neurons, and larval olfactory learning assays to understand the role of identified neurons in learning behaviour.
Click on the thumbnails below to view movies [also linked in-text]:
4 key publications
- Masuda-Nakagawa, L.M., Ito, K., Awasaki, T. and O’Kane, C.J. (2014) A single GABAergic neuron mediates feedback of odor-evoked signals in the mushroom body of larval Drosophila. Frontiers in Neural Circuits 8: 35. PMCID: PMC3988396 A summary of this paper is available
- Masuda-Nakagawa, L.M., Awasaki, T., Ito, K., and O’Kane, C.J. (2010) Targeting expression to projection neurons that innervated specific mushroom body calyx and antennal lobe glomeruli in larval Drosophila. Gene Expr Patts 10: 328. PMID: 20659588
- Masuda-Nakagawa, L.M., Gendre, N., O’Kane, C.J., and Stocker, R.F. (2009) Localized olfactory representation in mushroom bodies of Drosophila larvae. Proc. Natl. Acad. Sci. USA 106: 10314-10319. PMID: 19502424
- Masuda-Nakagawa, L.M., Tanaka, N.K., and O’Kane, C.J. (2005) Stereotypic and random patterns of connectivity in the larval mushroom body calyx of Drosophila. Proc. Natl. Acad. Sci. USA 102: 19027-19032. PMID: 163957192
Page amended 6 June 2014