Modern methods of neuroimaging are opening new windows to brain functions, among which the generation of mental images. Mental imagery consists of the reactivation of percept-like memory representations. This approach is unusual in human olfaction since the ability to create olfactory mental images is rare. Perfumers are a small population who have learned to form olfactory sensory representations through daily practice and extensive training.
To identify the neural correlates of odor representations and to evaluate the impact of long-term odor training on the brain regions involved in odor processing, we measured brain activity in perfumers while they smelled or imagined odors, using functional magnetic resonance imaging. Additionally, we used voxel-based morphometry to compare the gray-matter volume in perfumers as well as in untrained control subjects to investigate expertise-related structural reorganization.
The functional data confirmed that similar neural substrates were activated in odor perception and imagination. More importantly the level of activity of specific olfactory and memory brain regions in perfumers was negatively correlated with experience during the creation of mental images of odors. In addition, the structural data showed that the gray-matter volume in several olfactory brain regions was positively correlated with experience in perfumers.
Thus, extensive olfactory training leads to the acquisition of acute olfactory knowledge, which is paralleled by both a functional and a structural reorganizations of olfactory brain areas.

Jane PLAILLY, CRNL/Cmo