Altered local and matrix functional connectivity in depressed essential tremor patients

Area of Science:

• Neuroscience
• Clinical Neurology
• Psychiatry

Background:

• Depression is a common comorbidity in essential tremor (ET), but its underlying neural mechanisms are not fully understood.
• Regional homogeneity (ReHo) analysis of resting-state functional magnetic resonance imaging (fMRI) offers insights into spontaneous brain activity.

Purpose of the Study:

• To investigate spontaneous neural activity and functional connectivity (FC) differences in depressed ET patients compared to non-depressed ET patients and healthy controls (HCs).
• To explore the relationship between clinical depression severity and brain activity in ET patients.

Main Methods:

• Resting-state fMRI was used to perform local FC analyses, specifically ReHo, on 41 depressed ET patients, 49 non-depressed ET patients, and 43 HCs.
• Matrix FC and correlation analyses were conducted to examine inter-regional connectivity and its association with depression severity.

Main Results:

• Depressed ET patients exhibited decreased ReHo in bilateral cerebellum lobules IX and increased ReHo in bilateral anterior cingulate and middle prefrontal cortices compared to non-depressed ET patients.
• Significant ReHo differences were observed between depressed ET patients and HCs, with matrix FC revealing alterations in the frontal-cerebellar-anterior cingulate cortex pathway.
• Depression severity positively correlated with inter-ROI FC between the anterior cingulate cortex and middle prefrontal cortices, and negatively with FC between the anterior cingulate cortex and cerebellum lobules IX.

Conclusions:

• Altered local and inter-regional FC within frontal-cerebellar-anterior cingulate cortex circuits are characteristic of depression in ET patients.
• Cerebellum lobules IX, middle prefrontal cortices, and anterior cingulate cortices are identified as potential pathogenic structures contributing to depression in ET.