Cultural variation in the gray matter volume of the prefrontal cortex is moderated by the dopamine D4 receptor gene (DRD4)

Abstract

Recent evidence suggests a systematic cultural difference in the volume/thickness of prefrontal regions of the brain. However, origins of this difference remain unclear. Here, we addressed this gap by adopting a unique genetic approach. People who carry the 7- or 2-repeat (7/2-R) allele of the dopamine D4 receptor gene (DRD4) are more sensitive to environmental influences, including cultural influences. Therefore, if the difference in brain structure is due to cultural influences, it should be moderated by DRD4. We recruited 132 young adults (both European Americans and Asian-born East Asians). Voxel-based morphometry showed that gray matter (GM) volume of the medial prefrontal cortex and the orbitofrontal cortex was significantly greater among European Americans than among East Asians. Moreover, the difference in GM volume was significantly more pronounced among carriers of the 7/2-R allele of DRD4 than among non-carriers. This pattern was robust in an alternative measure assessing cortical thickness. A further exploratory analysis showed that among East Asian carriers, the number of years spent in the U.S. predicted increased GM volume in the orbitofrontal cortex. The present evidence is consistent with a view that culture shapes the brain by mobilizing epigenetic pathways that are gradually established through socialization and enculturation.

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