Stress is a part of daily life, however it seems some people are better able to deal with pressures while others fall into despair.  A new animal study suggests differences in brain activity account for why some are resilient and others may succumb to stress-induced depression.

For the study, scientists mapped the brain activity of mice who were put under stress and identified several brain regions that show different activity in mice that expressed helpless behavior compared to those who showed resilience.  This researchers identified regions of the brain that play an important role in stress-induced depression, and could be targets for future treatments.

“Our findings reveal distinct brain activity markings that correlate with adaptive and maladaptive behavioral responses to stress, and provide a framework for further studies investigating the contribution of specific brain regions to maladaptive stress responses,” the researchers wrote.

For the study, mice were subjected to bouts of inescapable and unpredictable foot shocks. They were separated into resilient and helpless groups depending on escape latency and number of failures in a testing session.  A failure was recorded if the mouse did not shuttle to avoid the 10 second shock. According to the researchers, the helpless mice had significantly more failures and longer escape latencies than the resilient ones.

[pullquote]Researchers identified regions of the brain that play an important role in stress-induced depression, and could be targets for future treatments.[/pullquote]

Overall, the animals that showed helpless behavior had a significantly lower amount of neural activity happening in the brain compared to the resilient mice, including in the prefrontal cortex, which is associated with planning, decision making and social behavior and has been implicated in anxiety disorders. The helpless mice also showed less activity in areas involved in reward processing, emotion, and behavioral motivation.  The hypothalamic area, which is important for defensive behavior, also had lower activation, as did areas related to stress coping, learning and memory, and cognitive function.  The only area of the brain that was more active in helpless mice was the locus coeruleus, suggesting that region may play a key part in stress-induced depression and should be studied further.

Additionally, the scientists saw a higher level of similarity in brain activity of the helpless mice. The researchers wrote that they, “uncovered abnormally stereotypic brain activity in helpless mice.”

More studies are needed to determine if these changes in brain activity are causally related to the expression of helplessness or resilience.

 Source: Frontiers in Neural Circuits.