Mapping the Microstructure and Striae of the Human Olfactory Tract with Diffusion MRI

Area of Science:

• Neuroscience
• Neuroimaging
• Sensory Systems

Background:

• The human sense of smell is crucial for various functions, including appetite, threat detection, and memory.
• Neural circuitry of the olfactory system, particularly the olfactory tracts, remains incompletely understood.
• Previous diffusion magnetic resonance imaging (dMRI) studies faced challenges in reconstructing olfactory tracts due to artifacts.

Purpose of the Study:

• To characterize the in vivo cortical connectivity of human olfactory tracts using advanced dMRI.
• To investigate the relationship between olfactory tract structural integrity and olfactory perception.
• To create a normalized probabilistic atlas of the olfactory tracts for future research.

Main Methods:

• Utilized dMRI with readout segmentation of long variable echo-trains (RESOLVE) to minimize image distortions.
• Collected high-resolution dMRI data from 25 healthy human participants.
• Applied probabilistic tractography with constrained spherical deconvolution (CSD) to identify olfactory tract striae and their connections.

Main Results:

• Successfully identified lateral, medial, and intermediate olfactory striae and their cortical targets (piriform cortex, amygdala, olfactory tubercle, anterior olfactory nucleus).
• Generated a normalized, probabilistic atlas of the human olfactory tracts.
• Found a negative correlation between olfactory tract mean diffusivity (MD) and odor discrimination performance.

Conclusions:

• Provides the first detailed in vivo description of human olfactory tract connectivity.
• Demonstrates a link between the structural integrity of olfactory tracts and olfactory perceptual function.
• The developed atlas can aid future research on olfactory tract integrity in health and disease.