Cortical myelin content mediates differences in affective temperaments.

BACKGROUND

Affective temperaments are regarded as subclinical forms and precursors of mental disorders. It may serve as candidates to facilitate the diagnosis and prediction of mental disorders. Cortical myelination likely characterizes the neurodevelopment and the evolution of cognitive functions and reflects brain functional demand. However, little is known about the relationship between affective temperaments and myelin plasticity. This study aims to analyze the association between the affective temperaments and cortical myelin content (CMC) in human brain.

METHODS

We measured affective temperaments using the Temperament Evaluation of Memphis, Pisa, Paris and San Diego Autoquestionnaire (TEMPS-A) on 106 healthy adults and used the ratio of T1- and T2-weighted images as the proxy for CMC. Using the unsupervised k-means clustering algorithm, we classified the cortical gray matter into heavily, intermediately, and lightly myelinated regions. The correlation between affective temperaments and CMC was calculated separately for different myelinated regions.

RESULTS

Hyperthymic temperament correlated negatively with CMC in the heavily myelinated (right postcentral gyrus and bilateral precentral gyrus) and lightly myelinated (bilateral frontal and lateral temporal) regions. Cyclothymic temperament showed a downward parabola-like correlation with CMC across the heavily, intermediately, and lightly myel0inated areas of the bilateral parietal-temporal regions.

LIMITATIONS

The analysis was constrained to cortical regions. The results were obtained from healthy subjects and we did not acquired data from patients of affective disorder, which may compromise the generalizability of the present findings.

CONCLUSION

The findings suggest that hyperthymic and cyclothymic temperaments have a CMC basis in extensive brain regions.