Olfactometry in fMRI studies: odor presentation using nasal continuous positive airway pressure

Area of Science:

• Neuroscience
• Sensory Science
• Medical Imaging

Background:

• Functional magnetic resonance imaging (fMRI) is crucial for studying brain activity.
• Accurate and controlled delivery of olfactory stimuli is challenging in fMRI environments.
• Existing methods may lack precision, introduce confounding sensory cues, or be prohibitively expensive.

Purpose of the Study:

• To present a novel, cost-effective olfactometer for generating and presenting olfactory stimuli during human fMRI.
• To enable precise synchronization of odor delivery with the respiratory cycle.
• To facilitate fMRI studies investigating olfactory perception and its neural correlates.

Main Methods:

• The olfactometer utilizes air dilution principles, integrating a nasal mask and a nasal Continuous Positive Airway Pressure (CPAP) device.
• It allows for computer-controlled, rapid switching between olfactory conditions, synchronized with the inhalation phase.
• The system records the subject's breathing pattern, ensuring stimulus delivery accuracy without sensory artifacts.

Main Results:

• The method successfully generated and presented distinct olfactory stimuli (pleasant and unpleasant odors) during fMRI.
• The system demonstrated reliability, maintaining constant odor concentrations throughout prolonged imaging sessions.
• The olfactory stimuli effectively induced different affective states in healthy subjects, as evidenced by fMRI data.

Conclusions:

• The developed olfactometer offers a reliable, affordable, and precise tool for olfactory fMRI research.
• It overcomes limitations of previous methods by minimizing sensory confounds and enabling respiratory-gated stimulus presentation.
• This technology supports advanced investigations into the neural basis of olfaction and emotion.