Parasympathetic systems, risk, and the brain

Professor Bruce McEwen describes how the hippocampus and prefrontal cortex mediate the parasympathetic system, which is associated with risk-taking.

Then you have the hippocampus, which is an area that’s involved in spatial learning and memory, and in what’s called contextual memory, in other words, remembering where you were and what you were doing when something either very good or bad happened. The prefrontal cortex is involved in many different things. It also – and, I should say, the hippocampus helps to turn off the physiologic stress response – so does the prefrontal cortex help to turn off the physiologic stress response. It also helps to balance between the two parts of the autonomic nervous system, the sympathetic and parasympathetic systems, and you have to have these symptoms in balance. If you have too much [para]sympathetic activity, you have a lot of inflammation, a lot of potential damage to your heart, many things. You need parasympathetic, and the prefrontal cortex helps you keep that in tune. It helps to regulate mood, so you don’t ruminate about negative things, it controls impulsive behaviors, so if you don’t have enough prefrontal cortical control, you may drive a car too fast, and that’s why young males have high insurance rates, because their prefrontal cortex hasn’t developed adequately. It’s also why testosterone may promote risk-taking behaviors, both through its ability to stimulate appetitive behaviors, but also through its ability, perhaps, to disinhibit a little bit the prefrontal cortex. The prefrontal cortex is involved in working memory and decision making, so it’s an extraordinary, important part of the brain that keeps everything in balance.