Greater hippocampal gray matter volume in subjective hyperosmia: a voxel-based morphometry study

Area of Science:

• Neuroscience
• Olfactory Research
• Neuroimaging

Background:

• Subjective hyperosmia (SH) is a self-reported heightened sense of smell, often linked to emotional olfactory experiences.
• Understanding the neural underpinnings of SH can provide insights into olfactory perception and its cognitive associations.

Purpose of the Study:

• To investigate differences in gray matter volume (GMV) between individuals with subjective hyperosmia (SH) and subjective normosmia (SN).
• To explore correlations between GMV and olfactory function within these groups.

Main Methods:

• Voxel-based morphometry (VBM) was employed to compare GMV between SH (N=18) and SN (N=14) participants.
• Olfactory function was assessed using the "Sniffin' Sticks" test battery.
• Region-of-interest (ROI) and whole-brain analyses were conducted.

Main Results:

• SH participants showed significantly larger GMV in the left hippocampus compared to SN participants (FWE corrected p < 0.05).
• Whole-brain analysis revealed greater GMV in SH participants in the bilateral hippocampus, right hypothalamus, left precuneus, and left superior frontal gyrus.
• Positive correlations were observed between left hippocampal GMV and odor threshold/discrimination scores across all participants.
• Among SH participants, self-rated olfactory ability correlated positively with GMV in the cerebellum, superior frontal gyrus, and precentral gyrus.

Conclusions:

• Subjective hyperosmia is associated with increased gray matter volume in key brain regions involved in olfactory processing and cognitive functions.
• These findings suggest a neuroanatomical basis for enhanced olfactory perception in individuals reporting hyperosmia.