Constant alterations of the olfactory system as a result of interaction with the chemosensory environment are a matter of interdisciplinary interest. Studies have shown that exposure to odors leads to changes at both peripheral and central levels of the olfactory system, and this may result from both bottom-up and top-down processes. It seems reasonable to expect that the olfactory system would adapt to sensory loss and compensate for the lack of visual or auditory input. Yet, results in this regard are contradictory, reporting either enhanced olfactory performance in blindness or no significant difference between people with blindness and their respective control groups. Inspired by this discrepancy, we have conducted a series of studies comparing people with blindness and people with deafness, with their respective control groups (sighted or blind, respectively). This work led us to the general conclusion of no major advantage of people with blindness over sighted people in the behavioural response to odours, but we did observe decreased chemosensory performance in people with deafness.
Plasticity of the olfactory system has also been used in the rehabilitation of people with olfactory loss (anosmia). Olfactory training (OT) is a systematic exposure to a defined set of odorants – e.g., lemon, rose, cloves, and eucalyptus, twice a day over the period of at least 12 weeks. OT has been found to effectively rehabilitate the sense of smell, particularly in patients who lost their sense of smell due to a viral infection. Given the proximity of the brain structures responsible for olfactory processing and the limbic system, we hypothesized that OT may be beneficial for cognitive and emotional processing. Presented evidence suggests that the effects of OT may extend beyond olfactory performance and provide support in cognitive aging and emotional development.