Alexithymia correlates with the size of the right anterior cingulate

The authors investigated a possible relationship between interindividual variability in anterior cingulate gyrus (ACG) morphology and alexithymia.

Magnetic resonance images were obtained in 100 healthy university graduates (51 female, 49 male; mean age 25.6 y). Surface area measurements of the ACG were performed on reformatted sagittal views in both hemispheres. The Toronto Alexithymia Scale (TAS-20) and the Temperament and Character Inventory (TCI) were administered.

Right ACG surface area significantly correlated with TAS-20 total score in men (r = 0.37; p = 0.009) and in women (r = 0.30; p = 0.034). After controlling for three TCI subscales (harm avoidance, self-directedness, and self-transcendency), the correlation between TAS-20 total and right ACG became nonsignificant in women, but was only slightly reduced (r = 0.32; p = 0.032) in men. A linear regression model with right ACG as a dependent variable revealed brain volume, TCI-harm avoidance and TAS 20 total score as significant predictors in the total sample (explained proportion of total variation (EPTV) 37%). In men, beside brain volume, only TAS-20 total score showed a highly significant contribution (EPTV 41%), whereas in women only TCI-harm avoidance was a significant predictor (EPTV 36%).

The authors' findings indicate that there is a significant positive relation between the size of the right ACG and alexithymia as measured with the TAS in healthy subjects. This applies especially for men whereas in women ACG size is more associated with the subscale harm avoidance of the TCI. Our findings also suggest a partial lateralization of human emotion processing, especially negative emotion.