Gunnar – stress biology

The research I do is research studying the effects of the biology of stress on human brain and behavioural development. Stress is a, the biology, the physiology of stress, is a really important mediator of the experiences we have and the impacts that that has on our brain development and our physical and health development as well. So, I’m very interested in that biology and we study that to try to understand how experience, some experience, especially adverse experiences, get under the skin and shape the way that we develop and our health.  

So there are two arms of the mammalian –we’re mammals—of the mammalian stress system. One of which people are very familiar with because we get really direct feedback from it. And that’s the sympathetic adrenal medullary system. That’s the adrenaline surge system. The one that you have a fright experience, you feel your heart suddenly racing, you get a lot of energy and you can run like heck for a very long period of time. The fight-flight system. 

And we get measures of that by measuring heart rate. We can look at the two sides of the nervous system: the parasympathetic calm down side, we measure something called vagal tone. It’s the extent to which you have variations in heart, in beats, timing between beats, that’s related to respiration. And that’s what the vagal system does. And the sympathetic arm of that system which we look at as something called pre-ejection period: the time between when your sinoatrial node says “beat”, and your heart beats.        

And so when you have more adrenaline flowing, that’s shorter. So, the heart says, “beat” and it goes. Okay, so we can measure autonomic activity to get an idea of the fight-flight side. Also supporting, and extremely critical, is the hypothalamic pituitary adrenal cortical system. Notice that the adrenals are involved here in both sides. This is the outside part of your two adrenal glands. It produces something called cortisol in humans. It’s a steroid hormone and it organizes long-term responses to stress. 

So it helps you to sort of go from running immediately to being able to sustain that for a longer period of time. It also shapes the way the brain will respond to the next adverse experience. So we’re very interested. My lab is particularly interested in that side of the stress system because, in terms of that question, how does it get under the skin and shape the way we develop, I’m interested in the regulation of that hormone which will shape longer term responses to stressors and life’s challenges. 

And we measure that in saliva. Because you produce this hormone, this steroid hormone, it goes into your blood stream, and some of it just seeps into your spit. So I can collect saliva and get a sense of how much of this has been produced in the child’s body.