'Social Defeat' Stressors & Behavioral Plasticity

An emerging field of social neuroscience explores the correlation between neural and behavioral plasticity. One might say that there is a particular 'zone' associated with this correlation: the mesolimbic dopamine pathway. This pathway, along with its projections into the nucleus accumbens, allows an organism to create automatic associations between emotionally salient stimuli in the environment and their outcomes, so that the organism can approach or avoid the stimuli accordingly--almost like a computer program that returns a particular output for a given input. A study by research team Berton et al. observes the effects of repetitive 'social defeat stress' in order to examine which exact neural correlate mediates long-term neural and behavioral plasticity in response to aversive social experiences. First, the team had to characterize the molecular mechanism responsible for altering activity in the mesolimbic dopamine pathway in response to a particular psychosocial experience. In order to do this, they adopted an experimental paradigm that models 'social defeat,' in which various mice were exposed to a different aggressor mouse each day for 10 days, and the social approach toward an unfamiliar mouse was recorded in a wire mesh cage that utilized a video-track system to track the 'socially defeated' mice's movement.

As you can see in the image on the left, the mice subjected to 'social defeat' generally avoided the interaction zone, where it would interact with each new aggressor mouse. These mice therefore developed an aversion to social interaction, signaling unified neural and behavioral  plasticity in response to a negative social experience. Further gene profiling/mainuplation of the subjects' NAc (nucleus accumbens) yielded the finding that brain-derived neurotrophic factor (BDNF) is responsible for both the development of experience-developed social aversion and the obliteration of this aversion, thus indicating the integral role of BDNF in modulating neural and behavioral plasticity in response to negative social experiences.







To view the full Berton et al. study, follow this link.