Summary: The researchers found a biomarker for major depressive disorder (MDD) in the folds of the brain’s outer covering, or gyri. The investigation, the first of its kind, linked MDD to the local gyrification index (LGI), a measure of cortical folding derived from brain scans.
The study revealed that patients with MDD showed decreased cortical folds, especially in the left pars triangularis. This breakthrough lays the foundation for a better understanding of MDD and potential treatment targets.
Key facts:
- This study is the first to examine the relationship between major depressive disorder (MDD) and the local gyrification index (LGI) of several cortical regions.
- The investigators found that patients with MDD showed lower LGI scores, indicating reduced cortical folds, especially in the left pars triangularis.
- The clinical characteristics of MDD, such as recurrence and disease duration, are associated with increased gyrification in several occipital and temporal cortical areas.
Source: Korea University School of Medicine
In appearance, the outermost layer of the human brain, called the cortex, is a maze of tissue folds. The raised crests or surfaces of these folds, called the gyri, play an important role in the proper functioning of the brain.
Improper gyrification — or development of gyri — has been implicated in a variety of neurological disorders, one of which is the debilitating and widespread mental illness, major depressive disorder (MDD).
Although previous studies have shown that abnormal cortical folding patterns are associated with MDD, reliable indicators so far remain out of reach.
Now, in a positive turn of events, researchers led by Professor Byung-Joo Ham and Associate Professor Kyu-Man Han of Korea University Medicine have reported the successful identification of a neuroimaging-based biomarker for MDD in a recent study published on May 8, 2023 in Psychological Medicine.
Talking about the unique findings that set their study apart from previous ones, Prof. Ham explains, “Our first study investigated the association of MDD with the local gyrification index or LGI of several cortical regions at the whole-brain level and the association of LGI with the clinical characteristics of MDD.”
But what exactly is the local gyrification index (LGI)?
LGI is a measurement of cortical folds derived from brain scans as the ratio of curved and smooth cortical surfaces in the region of interest.
In this study, the researchers compared the LGI values of various cortical regions in the brains of MDD patients with those of healthy people. The neuroimaging data used to compare and analyze the two groups was obtained from magnetic resonance imaging scans.
Prof. Ham and his team showed that LGI values of various cortical regions in the brains of MDD patients showed hypogyrification—a condition characterized by decreased cortical folding—when compared to healthy individuals.
They found that patients with MDD showed significantly lower LGI values in 7 of 66 cortical areas assessed (in both hemispheres), which included the prefrontal cortex, anterior cingulate cortex, insula, and several temporal and parietal areas.
Notably, the most significant hypogyrification was observed in the left pars triangularis of a patient with MDD. This finding is a breakthrough in MDD research!
When asked to share his thoughts on the results of the study, Dr. Han insists that there is more to their findings than meets the eye.
“The cortical regions that we assessed in our previous studies have been shown to influence emotion regulation. This means that the abnormal cortical folding pattern could be associated with dysfunction of neural circuits involved in emotion regulation, thereby contributing to the pathophysiology of MDD, he adds reflectively.
The study findings unequivocally establish LGI as a relatively stable neuroimaging marker for MDD, when compared to previously identified biomarkers. This is because LGI values reflect a long-standing developmental process of gyrification that is not spontaneously affected by individual circumstances during the measurement process.
It is also important to highlight the robustness of this study, given that it involved a larger sample size of participants, which gives it an advantage over previously conducted similar studies.
Interestingly, the investigators noted that the clinical characteristics of MDD, including recurrence and disease duration in patients, were associated with increased gyrification in several occipital and temporal cortical areas.
However, they did not observe any significant difference in LGI values in this region between the patients and the control group.
With the head-start provided by this study, future research may explore genetic factors that predispose individuals to abnormal cortical folding patterns, and, in turn, MDD. This study may also serve as a roadmap for the selection of cortical regions as targets for medical treatment aimed at reducing the symptoms of this condition.
Overall, by identifying a new biomarker for MDD, this research has paved the way for a deeper understanding of this serious and widespread mental health problem, which we hope will bring the medical community one step closer to finding effective solutions in the future.
About this major depressive disorder research news
Author: Gihyun Park
Source: Korea University School of Medicine
Contact: Gihyun Park – Korea University School of Medicine
Picture: The image is credited to Neuroscience News
Original Research: Open access.
“Reduced Cortical Girification in Major Depressive Disorder” by Byung-Joo Ham et al. Psychological Medicine
Abstract
Cortical Gyrification is Reduced in Major Depressive Disorder
Background
Early neurodevelopmental aberrations, such as abnormal cortical folding patterns, are candidate biomarkers of major depressive disorder (MDD). We aimed to investigate the relationship of MDD to the local gyrification index (LGI) in each cortical region at the whole brain level, and the relationship of LGI to the clinical characteristics of MDD.
Method
We obtained T1-weighted images from 234 patients with MDD and 215 healthy controls (HCs). LGI values of 66 cortical regions in the bilateral hemispheres were automatically calculated according to the Desikan-Killiany atlas. We compared LGI scores between the MDD and HC groups using analysis of covariance, including age, sex, and years of education as covariates. The relationship between clinical characteristics and LGI scores was investigated in the MDD group.
Results
Compared with HCs, patients with MDD showed significantly reduced LGI values in cortical areas, including bilateral ventrolateral and dorsolateral prefrontal cortex, medial and lateral orbitofrontal cortex, insula, right rostral anterior cingulate cortex, and several temporal and parietal areas, with the largest size effect in the left pars triangularis (Cohen’s F2 = 0.361; P = 1.78 × 10−13). Regarding the association of clinical characteristics with LGI in the MDD group, recurrence and longer disease duration were associated with increased gyrification in several occipital and temporal regions, which did not show a significant difference in LGI between the MDD and HC groups.
Conclusion
These findings suggest that LGI may be a relatively stable neuroimaging marker associated with MDD predisposition.
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