The circuits of olfactory signaling are reminiscent of complex computational devices. The olfactory receptor code, which represents the responses of receptors elicited by olfactory stimuli, is effectively an input code for the neural computation of odor sensing. Here, analyzing a recent dataset of the odorant-dependent responses of human olfactory receptors (ORs), we show that the space of human olfactory receptor codes is partitioned into a modular structure where groups of receptors are

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... ed" for key olfactory features. Our analysis reveals a low-dimensional structure in the space of human odor perception, with the receptor groups as the bases to represent major features in the perceptual odor space. These findings provide a novel evidence that some fundamental olfactory features are already hard-coded at the level of ORs, separately from the higher-level neural circuits.