Neighborhood matters: divergent patterns of stress-induced plasticity across the brain

Severe stress impairs cognitive function, but enhances emotionality. This Review describes how stress triggers contrasting patterns of plasticity in the hippocampus, prefrontal cortex and amygdala, all brain areas that are involved in learning and memory. These features of stress-induced plasticity can have long-term consequences for the debilitating symptoms of stress-related disorders. The fact that exposure to severe stress leads to the development of psychiatric disorders serves as the basic rationale for animal models of stress disorders. Clinical and neuroimaging studies have shown that three brain areas involved in learning and memory—the hippocampus, amygdala and prefrontal cortex—undergo distinct structural and functional changes in individuals with stress disorders. These findings from patient studies pose several challenges for animal models of stress disorders. For instance, why does stress impair cognitive function, yet enhance fear and anxiety? Can the same stressful experience elicit contrasting patterns of plasticity in the hippocampus, amygdala and prefrontal cortex? How does even a brief exposure to traumatic stress lead to long-lasting behavioral abnormalities? Thus, animal models of stress disorders must not only capture the unique spatio-temporal features of structural and functional alterations in these brain areas, but must also provide insights into the underlying neuronal plasticity mechanisms. This Review will address some of these key questions by describing findings from animal models on how stress-induced plasticity varies across different brain regions and thereby gives rise to the debilitating emotional and cognitive symptoms of stress-related psychiatric disorders.