Investigating the Effects of Stress on Brain Circuitry
We are all familiar with the unpleasant physical symptoms of stress – things like headache, irritability, and fatigue – which all stem from activity in our brain. The ability to respond to stress is an essential survival tool. However, when the stress system responds inappropriately, it can lead to mental health conditions such as depression and anxiety disorders.
How the brain reacts to stress, through changes to cells and circuits within the brain, remains, for the most part, a mystery. HBI researcher Dr. Jaideep Bains is working to understand how stressful situations can lead to long-term changes in brain circuitry and the functioning of individual brain cells, or neurons.
Bains focuses on circuits in the hypothalamus, which is the brain’s command-centre for stress responses. He and his team discovered how neurons in that area of the brain control the levels of stress hormones in the body. They also found that the brain’s response to stress depends on how that stress is encountered.
“For example,” explains Bains, “we already know that repeated exposure to the same stressor changes your reaction to it over time. What we’ve discovered for the first time are some of the key cellular mechanisms that may be responsible for these changes.” These adaptations are critical to allowing the brain to filter out stressors that are not threatening.
Most recently, Bains also discovered a means through which the brain can respond rapidly to unique stressors. So, while it may adapt over time to a constant source of stress, the brain continues to remain vigilant for new perceived threats that may appear. Bains has uncovered a mechanism that may explain how a new source of stress can prime the brain to react even more robustly to subsequent stressful events.
“We have discovered that stress signals arriving in the brain leave a molecular imprint on brain cells that lasts for several days,” explains Bains. “We then observed that these imprinted cells reacted more strongly to subsequent stressors.”
By understanding how stress leads to long-term changes in brain circuitry, Bains hopes that we can learn how to “switch off” the brain’s inappropriate responses to unpredictable stress. Understanding how the brain’s stress command centre can discriminate between a repeated stressor that is harmless versus one that requires an immediate response is a vital step towards the development of new ways of treating or preventing the disorders caused by stress.
“At the end of the day what we are striving for is understanding the factors that create the balance between stress resilience and vulnerability. We want to have the ability to experience stress, respond appropriately, and then move on with our lives.”
Posted May 28, 2012