Differences in olfactory functional connectivity in early-onset depression and late-onset depression

Area of Science:

• Neuroscience
• Psychiatry
• Medical Imaging

Background:

• Late-onset depression (LOD) and early-onset depression (EOD) have distinct pathological mechanisms and clinical features, including varying degrees of olfactory dysfunction.
• The specific brain abnormalities contributing to olfactory dysfunction differences between EOD and LOD are not well understood.

Purpose of the Study:

• To compare functional connectivity (FC) patterns in olfactory regions between EOD and LOD patients.
• To investigate the relationship between olfactory FC and cognitive function in these patient groups.

Main Methods:

• Recruited 105 EOD patients, 101 LOD patients, and 160 normal controls (NCs).
• Conducted clinical assessments, olfactory testing, cognitive evaluations, and magnetic resonance imaging (MRI).
• Analyzed FC within eight primary and secondary olfactory regions.

Main Results:

• LOD patients demonstrated significantly decreased odor identification (OI) compared to EOD patients and NCs.
• The LOD group exhibited reduced FC in olfactory regions (piriform cortex, lateral entorhinal cortex, orbital-frontal cortex) compared to EOD and NC groups.
• Abnormal olfactory FC correlated with impaired cognitive function and OI, with left orbital-frontal cortex-amygdala FC partially mediating the link between global cognition and OI.

Conclusions:

• LOD patients display reduced FC in primary and secondary olfactory cortices compared to EOD patients.
• Altered olfactory FC is associated with olfactory dysfunction and cognitive deficits in LOD.
• Orbital-frontal cortex-amygdala FC plays a mediating role in the relationship between cognitive function and olfactory identification.