تأثیرات اجتماعی بر بیولوژی اعصاب و رفتار: اثرات اپی ژنتیک در طول توسعه

The quality of the social environment can have profound influences on the development and activity of neural systems with implications for numerous behavioral and physiological responses, including the expression of emotionality. Though social experiences occurring early in development may be particularly influential on the developing brain, there is continued plasticity within these neural circuits amongst juveniles and into early adulthood. In this review, we explore the evidence derived from studies in rodents which illustrates the social modulation during development of neural systems, with a particular emphasis on those systems in which a long-term effect is observed. One possible explanation for the persistence of dynamic changes in these systems in response to the environment is the involvement of epigenetic mechanisms, and here we discuss recent studies which support the role of these mechanisms in mediating the link between social experiences, gene expression, neurobiological changes, and behavioral variation. This literature raises critical questions about the interaction between neural systems, the concordance between neural and behavioral changes, sexual dimorphism in effects, the importance of considering individual differences in response to the social environment, and the potential of an epigenetic perspective in advancing our understanding of the pathways leading to variations in mental health.

Though our understanding of the neurobiology of mood disorders has advanced through the use of modern imaging and pharmacological techniques, there are still significant gaps in our knowledge regarding the origins of increased susceptibility to psychopathology. Epidemiological studies of the impact of early-life abuse and neglect suggest that the quality of early social experiences is associated with an altered risk of depression and anxiety in adulthood (Batten et al., 2004, Bradley et al., 2008, Neigh et al., 2009 and Stirling and Amaya-Jackson, 2008). These studies suggest that the quality of the early-life social environment may lead to a cascade of neurobiological changes with implications for numerous behavioral outcomes, including enhanced emotionality. Further support for the role of the social environment in shaping the brain comes from experimental studies in rodents, where targeted manipulation of postnatal mother–infant interactions has been demonstrated to induce long-term changes in behavior associated with effects on a wide range of neural systems. These results suggest that plasticity in brain development in response to the early social environment may account for the vulnerability that exists in individuals when they are exposed to disruptions in the quality of that environment. Interestingly, the social influence on risk and resilience may not be limited to these early developmental time-points. Here we will highlight literature from recent experimental studies in rodents illustrating how social experiences occurring during postnatal and juvenile periods, and in early adulthood, can shape neural systems that in some cases may lead to altered emotionality (i.e. behavioral and physiological responses to stress, novelty, etc.). Though questions still remain regarding the time-course, specificity, and behavioral consequences of these changes, there is emerging evidence that epigenetic regulation of gene expression may be a critical feature of this neural plasticity. We will explore the recent evidence supporting an epigenetic perspective on the origins of individual differences in behavior and identify critical issues raised by these studies that can guide future studies on the role of the social environment in shaping brain development.