Low-cost, open-source device for applying controlled olfactory stimuli during functional magnetic resonance imaging (fMRI) of the brain.

Using functional magnetic resonance imaging (fMRI) to assess brain activity in response to olfactory stimuli is of great biomedical and clinical interest. However, application of controlled sequences of olfactory stimuli within the setting of fMRI equipment is challenging since the associated limitations for non-magnetic and non-conducive materials. Here, we have developed and tested a simple, low-cost, open-source, stand-alone device to apply selectable controlled sequences of olfactory stimuli in subjects undergoing fMRI. The device consists of an Arduino-controlled unit containing a blower-based airflow generator and a multichannel air valves system, a set of long air conducting tubing, and bubbler-based odor sources. The device was first validated on the bench to characterize the range of achievable flows, ensuring that the device can be adapted to a variety of applications and fMRI settings. The effectiveness of device performance was subsequently assessed in female patients with sexual dysfunction using a fMRI protocol based on subjecting them to controlled sequences of olfactive stimuli with pheromone, phenethyl alcohol (a rose fragrance) or neutral clean air. Therefore, the device facilitates biomedical research and clinical assessment of the neural pathways modulated by the olfactory system.