Now diving into the processing and transformation of raw olfactory stimulation of sensory neurons to the output of the olfactory neuropils via projection neurons, see these two papers, one in fly and one in zebrafish. The former shows how PNs respond to the derivative of the input, which is essential for tracking stimuli up a gradient, and the latter shows how the LNs perform a whitening of the olfactory input (to decorrelate the inputs into the otherwise multiply stimulated olfactory receptors and their corresponding sensory neurons) which optimally prepares similar stimuli for separation:
Kim AJ, Lazar AA, Slutskiy YB. Projection neurons in Drosophila antennal lobes signal the acceleration of odor concentrations. Elife. 2015 May 14;4:e06651.
https://elifesciences.org/articles/6651
Wanner AA, Friedrich RW. Whitening of odor representations by the wiring diagram of the olfactory bulb. Nature neuroscience. 2020 Mar;23(3):433-42.
https://www.nature.com/articles/s41593-019-0576-z
4/4
Neurons in the fruit fly olfactory system respond most strongly to the sudden appearance of an odor, and to odors that are changing rapidly in strength, but are relatively insensitive to the absolute levels of an odor.
And in flies in particular, all papers signed by Rachel Wilson as the senior author (now a professor at Harvard Medical School) in the early 2000s are absolutely outstanding, on probing with electrophysiology and genetics the various synapses in the fruit fly olfactory system, e.g., the sensory neuron (ORN or OSN, synonyms) to the projection neurons (PNs), or the local neurons (LNs), or the LNs to each other or to the PNs, and the PNs back to the LNs. She's written a couple of reviews on the subject that are very accessible for the curious student.
Click on "Publications" and expand them, to find the ones published in Current Opinion in Neurobiology or in the Annual Review Neuroscience:
https://neuro.hms.harvard.edu/faculty-staff/rachel-wilson
... like e.g., this one:
Wilson RI. Early olfactory processing in Drosophila: mechanisms and principles. Annual review of neuroscience. 2013 Jul 8;36(1):217-41.
https://www.annualreviews.org/content/journals/10.1146/annurev-neuro-062111-150533
Rachel's more recent work is on neural networks in the fly for spatial navigation.
3/4
On that, the work from Lucia Prieto-Godino in (then) Richard Benton's lab on "undead" neurons is critical, demonstrating that, beyond the genes encoding olfactory receptors, there is a much larger pool of pseudogenes (genes that aren't normally expressed) that, when rescued, result in additional, distinct yet functional glomeruli in the first-order neuropil for olfaction (the antennal lobe in an insect; the olfactory bulb in a vertebrate).
Prieto-Godino LL, Silbering AF, Khallaf MA, Cruchet S, Bojkowska K, Pradervand S, Hansson BS, Knaden M, Benton R. Functional integration of โundeadโ neurons in the olfactory system. Science advances. 2020 Mar 11;6(11):eaaz7238.
https://www.science.org/doi/abs/10.1126/sciadv.aaz7238
Lucia is now a lab head at The Crick, studying with comparative connectomics the evolution of olfactory circuits and more, in fruit flies.
2/4
An undergraduate student asked me about olfactory sensory processing and this is what I replied. What have I missed of major importance, from the perspective of a senior undergrad?
The olfactory system is indeed fascinating, one that challenged researchers for some time. The first major break through came from Richard Axel's lab by the hand of the then student Leslie Vosshall, now professor at Rockefeller in New York and prominent HHMI Vicepresident and mosquito researcher.
Vosshall LB, Amrein H, Morozov PS, Rzhetsky A, Axel R. A spatial map of olfactory receptor expression in the Drosophila antenna. Cell. 1999 Mar 5;96(5):725-36.
https://www.cell.com/cell/fulltext/S0092-8674(00)80582-6
A search for "Vosshall Axel" in Google Scholar will surface related papers:
https://scholar.google.com/scholar?hl=en&as_sdt=0%2C5&q=vosshall+axel&btnG=
A conceptual breakthrough in olfactory coding came from the study of receptors by several groups, in both flies and mice, and later in zebrafish, but what I find compelling is the development of the primacy hypothesis for olfactory receptors by Rinberg's and Koulakov's labs:
Wilson CD, Serrano GO, Koulakov AA, Rinberg D. A primacy code for odor identity. Nature communications. 2017 Nov 14;8(1):1477.
https://www.nature.com/articles/s41467-017-01432-4
The above relates to the ability of animals to have a small number of olfactory receptors (like a fly larva) or more (an adult fruit fly) or many more (like moths and bees), or even more (like in a dog's nose), and yet the system works. More receptors support a less coarse encoding of odours, and vice versa. But the system for olfactory sensing is flexible and therefore evolvable.
1/4
Very amusing to see how the vertebrate developmental neurobiology field is converging with #Drosophila and insects in general with regard to the mechanisms of brain development:
"Together, these findings suggest a lineage-based mechanism for scalable positional information that complements diffusion-based mechanisms and offers a general framework for tissue patterning."
That sentence has been used for decades to describe fruit fly brain development.
Research Reveals How Zebrafish Larval Behavior Sheds Light on Human Handedness
๐ฐ Original title: I study why zebrafish larva prefer to circle left or right, to understand how and why human brains encode right- and left-handedness
๐ค IA: It's not clickbait โ
๐ฅ Usuarios: It's not clickbait โ
View full AI summary: https://killbait.com/en/research-reveals-how-zebrafish-larval-behavior-sheds-light-on-human-handedness/?redirpost=d0257863-96d7-4a82-bbca-28f1c72a8ce1
BiO is proud to partner with the European Zebrafish Society to offer travel grants for the 13th European Zebrafish Meeting (EZM2026) - 7-11 July 2026 in Vienna, Austria. This travel grant is designed to provide financial support for early-career researchers based in the Global South.
More information and an application form can be found on the EZS website: https://www.ezsociety.org/grants-EZM2026
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