Functional brain imaging of olfactory processing in monkeys

Area of Science:

• Neuroscience
• Olfactory System Research
• Comparative Neuroimaging

Background:

• Bridging the gap between human and animal olfactory brain system studies is crucial.
• Functional magnetic resonance imaging (fMRI) is a key tool for studying brain activity.

Purpose of the Study:

• To conduct an fMRI study of olfaction in squirrel monkeys.
• To enable direct comparisons between human and nonhuman primate olfactory processing.

Main Methods:

• High-resolution fMRI at 3 Tesla with specific voxel size (1.25 x 1.25 x 1.2 mm³).
• Whole-brain imaging using a birdcage coil and gradient-echo spiral pulse sequence.
• Standard block design with sedated adult male squirrel monkeys, followed by spatial normalization and statistical analysis.

Main Results:

• Detected robust odorant-induced brain activations in regions like the orbitofrontal cortex, cerebellum, and piriform cortex.
• Observed signal changes exceeding 0.6%, significantly higher than expected based on human studies.
• Found no stimulus intensity effects in the identified regions, consistent with human olfactory data.

Conclusions:

• Demonstrated the feasibility of studying olfaction in sedated monkeys using human-standard fMRI techniques.
• Provided novel support for the cerebellum's role in sensory acquisition.
• Suggested shared neural substrates for olfactory processing between sedated monkeys and humans.