Optimization and Evaluation of an Olfactory Stimulator for fMRI Studies

Abstract

An automatically-controlled olfactometer that can be used in the magnetic resonance imaging environment was designed and built in this study. The overall system design was in accordance with the general requirements of stimulator and aimed to show improvement over an existing olfactometer in the laboratory. The device included two parts:the control system and the gas transportation system. The control system used LabVIEW platform-based software and adopted a virtual apparatus scheme. It was capable of providing man-machine interaction controlling stimulus sequence and gas paths according to the applications. The gas delivery system consisted of 4 variable gas paths and 1 constant gas path, through which clean air was transmitted to three gas-washing bottles filled with liquids having different odors. The fluctuation of gas flow measured by a Honeywell AWM43600 airflow sensor was within 0.3%, and the switching response time between different branches was about 1.07 s. Founctional magnetic resonance imaging (fMRI) experiments on olfaction were performed on 8 subjects with the stimulation device, providing odors of ethanol, pyridine and isoamyl acetate. The fMRI results demonstrated thalamus, amygdala, piriform cortex, orbital frontal cortex activations upon olfactory stimulation. It was concluded that the olfactometer built can deliver quantitative olfactory stimulus and meet the requirements for olfactory fMRI experiments.

Keywords

• fMRI
• olfactory stimulator