Role of Gene-Environment Interplay in Individual Differences in Brain and Behavior

Emerging evidence suggests that, in contrast to traditional notions of nature vs. nurture dichotomies, there is a dynamic interplay between genes and the environment during the process of development that can lead to individual differences in brain and behavior.  At a molecular level of analysis, this interplay is achieved through epigenetic mechanisms which regulate gene expression and are responsive to changing environmental conditions.  Studies in rodents have illustrated the impact of variations in the early social environment on stress responsivity, response to reward, and adult reproductive/social behavior mediated through the epigenetic regulation of gene expression.  Though these mechanisms are capable of maintaining stable individual differences in behavior, it is increasingly apparent that plasticity exists whereby experiences occurring during later time-points can shift the developmental trajectory.  These environmental influences also have implications for the transmission of traits across multiple generations and there in increasing evidence for these transgenerational effects in the study of experience-dependent epigenetic change.  In translating these findings to humans, it is critical to consider site-specificity and gene-specificity of epigenetic effects as well as the potential “match” or “mismatch” between environmental conditions experienced during early vs. later periods of development.  Overall, these studies suggest that epigenetic mechanisms may provide a “memory” of early experiences leading to stable individual differences in adult behavior that may serve as a phenotypic adaptation to the environment.