Social influences on neuroplasticity: stress and interventions to promote well-being

Abstract

Experiential factors shape the neural circuits underlying social and emotional behavior from the prenatal period to the end of life. These factors include both incidental influences, such as early adversity, and intentional influences that can be produced in humans through specific interventions designed to promote prosocial behavior and well-being. Here we review important extant evidence in animal models and humans. Although the precise mechanisms of plasticity are still not fully understood, moderate to severe stress appears to increase the growth of several sectors of the amygdala, whereas the effects in the hippocampus and prefrontal cortex tend to be opposite. Structural and functional changes in the brain have been observed with cognitive therapy and certain forms of meditation and lead to the suggestion that well-being and other prosocial characteristics might be enhanced through training.

Figure 1

Chronic stress causes neurons to shrink or grow but not necessarily to die. Representation of the chronic stress effects detected in animal models on growth or retraction of dendrites in the basolateral amygdala and orbitofrontal cortex (growth) and in the CA3 hippocampus, dentate gyrus and medial prefrontal cortex (shrinkage), as described in the text. These effects are largely reversible in young adult animals, although aging appears to compromise resilience and therefore at least in medial prefrontal cortex recovery.

Figure 2

Physically abused children show alterations in orbitofrontal volume compared with typically developing children and volume shrinkage in this region is related to measures of family stress. Top: Physically abused children show reductions in orbitofrontal cortex compared with typically developing controls; Bottom: Among physically abused children, those showing poorer academic function and poorer family functioning (greater family stress) exhibit less volume in orbitofrontal cortex. Note that because the voxel-wise analysis was a between groups comparison and the correlational analysis was conducted with the abused children only, this does not suffer from the “double-dipping” problem.

Figure 3

Anatomically segmented amygdala volumes are larger in later-adopted post-institutionalized children. a. Anatomical segmentation of the amygdala; b. later-adopted post-institutionalized children show larger amygdala volume compared with both early adopted children and with typically developing controls. No differences among groups were found in hippocampus or caudate. Asterisk indicates that the later adopted group exhibits significantly larger amygdala volume compared with each of the comparison groups.

Figure 4

Change in gray matter volume in the right basolateral amygdala from pre to post eight weeks of mindfulness-based stress reduction (MBSR) was associated with decreases in perceived stress over this same time period. Individuals undergoing MBSR who showed the largest decreases in perceived stress also showed the largest decreases in basolateral amygdala gray matter volume.