Imagine trying to make sense of a vast library filled with all sorts of books, but you only have a few shelves to store them. That’s the challenge our brains face when it comes to processing complex odors. Luckily, olfactory circuits have a clever solution. By using disorder, diffuse sensing, and redundancy, they can compress the immense variety of smells into a small space while still preserving their similarities. It’s like having a magical closet that can hold many different items in an organized yet flexible way. This allows us to learn associations between odors and valences, despite the limited sensory receptors we have. The architecture of our olfactory circuits also involves lateral interactions that decrease correlations in the receptor code, further enhancing the precision of odor representation. And when it comes to transmitting this information to the central brain, disordered projections help reconfigure the densely packed data into a high-dimensional representation, providing multiple redundant subsets for downstream neurons to learn from. Interestingly, introducing any order or structure in these projections can interfere with our ability to recall learned associations in noisy environments. This intriguing theory has been tested using data from Drosophila, highlighting the unique role of disorder in processing olfactory information. To dive deeper into the research and understand more about how our brains make sense of smells, check out the full article!

Animals smelling in the real world use a small number of receptors to sense a vast number of natural molecular mixtures, and proceed to learn arbitrary associations between odors and valences. Here, we propose how the architecture of olfactory circuits leverages disorder, diffuse sensing and redundancy in representation to meet these immense complementary challenges. First, the diffuse and disordered binding of receptors to many molecules compresses a vast but sparsely-structured odor space into a small receptor space, yielding an odor code that preserves similarity in a precise sense. Introducing any order/structure in the sensing degrades similarity preservation. Next, lateral interactions further reduce the correlation present in the low-dimensional receptor code. Finally, expansive disordered projections from the periphery to the central brain reconfigure the densely packed information into a high-dimensional representation, which contains multiple redundant subsets from which downstream neurons can learn flexible associations and valences. Moreover, introducing any order in the expansive projections degrades the ability to recall the learned associations in the presence of noise. We test our theory empirically using data from Drosophila. Our theory suggests that the neural processing of sparse but high-dimensional olfactory information differs from the other senses in its fundamental use of disorder.

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