Design and Testing of an Olfactory Stimulus Presentation Device for use in Functional Magnetic Resonance Imaging (fMRI)

Abstract

<p>Olfaction is an ancient and complex chemosensory process that for many animals serves as their main sensory link with the surrounding environment. In the field of functional brain imaging, it is a process that has been largely unstudied due to many complicating factors such as the qualitative nature of olfaction, the difficulty of providing stimuli in a controlled manner, and the non-superficial location of the main olfactory centers of the brain. The goal of this project was to develop an MRI compatible device for generation and presentation of olfactory stimulus for use in functional imaging of the olfactory response. After taking into consideration various constraints in the design process, the final device design consists of a scented liquid that is nebulised in an Erlenmeyer flask by pressurized medical air and subsequently transported through chemically inert tubing to a modified ventilator mask secured to the subject. To test the device, functional magnetic resonance imaging (fMRI) analysis was performed with an experimental protocol that provided stimulus for a period of 30 seconds and allowed it to clear for 90 seconds. This procedure was repeated over 5 cycles starting with 90 seconds of no stimulus resulting in a total time of 10 minutes. Statistical analysis was performed on the resulting images from two of the three fMRI experiments undertaken and the results of the last trial show activation of deep areas of the brain commonly associated with olfaction and described in existing publications on the topic. This is a promising result given the number of trials undertaken and the simplistic nature of the overall experimental protocol. Therefore, the conclusion is that with increased time and funding the basic device and experimental protocols presented in this project could easily be expanded to assist in a functional characterization of the olfactory response.</p>