Olfactory fMRI Activation Pattern Across Different Concentrations Changes in Alzheimer's Disease.

Area of Science:

• Neuroimaging
• Olfactory Neuroscience
• Neurology

Background:

• Olfactory dysfunction is an early indicator of Alzheimer's disease (AD).
• Olfactory functional MRI (fMRI) offers an objective measure of olfactory function.
• Variations in individual responses and magnetic artifacts can affect olfactory fMRI reliability.

Purpose of the Study:

• To enhance the reliability of olfactory fMRI by examining primary olfactory cortex (POC) responses.
• To investigate olfactory fMRI patterns across three odor concentrations in controls, mild cognitive impairment (MCI), and AD patients.
• To assess the utility of POC activation patterns in detecting early AD.

Main Methods:

• Olfactory fMRI was performed on 44 controls, 46 MCI subjects, and 44 AD patients using lavender stimuli at 0.10%, 0.33%, and 1.00% concentrations.
• Analysis focused on activated voxels in the POC and changes in activation across different concentrations.
• Five distinct POC activation patterns were identified and correlated with olfactory function.

Main Results:

• Normal controls exhibited olfactory adaptation to higher odor concentrations.
• AD patients demonstrated an increased olfactory threshold and a lack of olfactory habituation.
• The POC activation pattern successfully identified 90.9% of AD patients with impaired habituation and 63.0% of MCI subjects with impaired habituation.

Conclusions:

• POC activation patterns in olfactory fMRI across varying concentrations are effective for evaluating olfactory function.
• This method shows promise for the early detection of Alzheimer's disease, particularly in individuals with mild cognitive impairment.