Biomarker for Major Depressive Disorder Discovered
The abnormal gyrification, or the development of gyri, can manifest as serious neurological disorders, including the highly disabling and widespread mental illness — major depressive disorder (MDD). Although the link between abnormal gyrification and MDD is well established, a reliable indicator or biomarker has so far remained out of reach.
Researchers led by Professor Byung-Joo Ham and Associate Professor Kyu-Man Han from Korea University Medicine have successfully identified a neuroimaging-based biomarker for MDD in a recent study published in Psychological Medicine. They found that the local gyrification index (LGI), a measurement of cortical folding that is derived from brain scans, is markedly different in patients with MDD when compared with healthy individuals.
From detailed brain MRI scans, the researchers found significantly lower LGI values, which is indicative of hypogyrification or decreased cortical folding, in 7 of the 66 cortical regions assessed on both hemispheres of the brain of patients with MDD. These regions included the prefrontal cortex, anterior cingulate cortex, insula, and several temporal and parietal regions. They also observed the highest amount of hypogyrification in the left pars triangularis of these individuals. Their findings attest to the suitability of using LGI as a biomarker of MDD. Because LGI values reflect the long-drawn developmental process of gyrification that is not spontaneously affected by an individuals' state during the measurement process, it could be a relatively stable neuroimaging biomarker for assessing MDD risk.
This study is reportedly a first-of-its-kind in investigating the association between the clinical characteristics of MDD and LGI, while involving a relatively larger number of participants. As part of their study, the researchers noted an association between the recurrence and duration of illness and increased gyrification in several occipital and temporal cortical regions, although they found no significant difference in the LGI values for these regions between the patients and healthy individuals.
Dr Han believes that their findings may have deeper implications, "The regions with hypogyrification that we've identified have been widely explored in MDD research and they've been shown to play a pivotal role in neural circuits involved in emotional regulation. Our findings could be evidence for the pathophysiology of MDD." Prof Ham concludes, "Our findings can provide a basis for the selection of targets for future neuromodulation treatments including non-invasive brain stimulation with electricity, especially in the prefrontal cortex, to improve the symptoms of MDD."