Perceptual and neural plasticity of odor quality coding in the human brain

Current neurobiological models of odor perception tend to emphasize the “bottom-up” contributions of odorant chemistry in determining the perceptual features of an odor. However, increasing research suggests that “topdown” effects related to learning and experience play equally important roles in human olfactory perception, implying that a given set of olfactory receptors activated by an odorant does not neatly map onto a given odor percept. Rather, odor perception may rely on more synthetic mechanisms subserved by higher order brain regions. This review article focuses on the modulatory effects of learning, context, and experience on human odor perception. Recent psychophysical and neuroimaging work from our laboratory indicates that sensory-specific information about odor quality is not static within human piriform and orbitofrontal cortices but can be rapidly updated by mere sensory exposure. This experience-dependent neural plasticity parallels behavioral improvements in odor perception, providing direct evidence for the role of learning in shaping neural representations of odor quality in the human brain.