Objective: To investigate the heritability of personality traits related to brain regions by recruiting a group of healthy mothers with their daughters.
Methods: Twenty-two right handed mother-daughter pairs who gave their informed consents were included in this study. All of the participants were screened with non-patient Turkish version of Structured Clinical Interview for DSM IV (Diagnostic and Statistical Manual of Mental Disorders) to rule out any current and past psychiatric disorder. The volunteers filled the TCI (Temperament and Character Inventory) and underwent MRI (Magnetic Resonance Imaging) for brain imaging in consecutive days. The MRI scans of the participants were obtained during their follicular phase to control menstrual effect on brain volume. Image analysis was performed using SPM 8 software (Statistical Parametric Mapping) running in MATLAB 7. Image processing was based on the VBM-DARTEL (Voxel Based Morphometry) method. Age and total brain volume were included as confounding factors. To obtain common brain structures correlated with personality traits in both groups, group x personality dimension interaction analyses were performed.
Results: The daughters had higher education years and they scored significantly higher NS (Novelty Seeking) points compared to their mothers. The correlation analyses revealed that HA (Harm Avoidance) in temperamental traits, SD (Self-Directedness) and ST (Self-Transcendence) in character traits were correlated significantly within mother-daughter pairs. The common brain structures which were significantly interacted in different personality traits were: Harm Avoidance: Positively interacted areas were right orbitofrontal cortex (BA 10) and left occipital cortex (BA 19), negatively interacted areas were left inferior frontal lobe (BA 45), left primary sensory cortex (BA 1), right amygdala, hypothalamus and cerebellum. Novelty Seeking: Positively interacted areas were left primary sensory cortex (BA 1) and the pole of left temporal lobe (BA 20). There was no negative interaction. Reward Dependence: There was only positively interacted areas which were left frontal lobe (BA 6, 8), right primary sensory area extended to motor areas (BA 3, 4), the pole of left temporal lobe (BA 20), the left inferior (BA 44) and the right middle frontal gyrus (BA 46). Persistence: There was only positively interacted areas which were bilateral ventral striatum and bilateral superior frontal gyrus at BA 6. Self-Directedness: There were only negative associations at the bilateral middle frontal gyrus (BA 6), right inferior frontal gyrus (BA 44), right precentral gyrus (BA 9) and posterior cingulate cortex. Cooperativeness: There was only one negative correlation at left superior temporal gyrus (BA 21). Self-Transcendence: There were only negative interactions at superior temporal gyrus (BA 22) bilaterally, left orbitofrontal cortex (BA 10) and right fusiform gyrus (BA 37).
Conclusion: Despite of the limitations, the effect of inheritance related with different personality traits was shown on multiple candidate brain regions in this study. The overlapped brain regions with various personality traits suggest the involvement of these regions in different neural networks by multitasking.