The Incredible Shrinking Hippocampus
It didn’t feel good. Worry was a feeling in my chest and it woke me up at night. Fear made my heart pound, my ears ring and my voice go funny. Depression pulled my energy plug and made it hard to imagine being in any other state.
Jolts of fear are fine. The rush before heading downhill on skis is fun. Sustained anxiety is not.
When I was feeling bad – emotionally and physically – I took it as a sign of my own weakness. Surely, if I was stronger or smarter in some way, I wouldn’t be feeling this.
It has been a relief to discover that forces are at work that are bigger than my wishes or will, and that I can respond in more helpful ways than I previously recognized.
It is bigger than I can control
Our bodies are remarkable creations. They are programmed to help us cope with danger by opening chemical valves long before our thought processes can respond. In the face of immediate alarm this serves us well. We respond appropriately and deal with the perceived threat. When the moment of alarm has passed, our bodies then return to normal programming, trying to digest that lunch or repair that bruise.
There are times, however, when life makes it difficult to return to normal. At home, there may be economic struggles or prolonged worry about a loved one. When working abroad new food, new language and work environments, scary traffic or security worries may keep us on edge for long periods of time. When that happens, the chemistry that helped us in the short term can work against us. The good news is that we can act to help bring the chemistry back into line.
A wee bit of anatomy
Our brain’s “shock absorber” is called the hippocampus. It does a number of things, including create new memories and manage emotions. When subjected to prolonged stress, depression or disorders like Alzheimer’s, the hippocampus actually shrinks in size and its ability to function diminishes. Close by the hippocampus are structures called the amygdala, sometimes called the brain’s “alarm bell”.
Imagine a stimulus – someone suddenly yelling or jumping in front of us. That stimulus signal is routed through a clearing house called the thalamus and then directed to parts of the brain responsible for creating meaning and conscious thought. Part of it is also routed to the amygdala.
Our immediate response to danger or trauma:
If the amygdala determines a fight or flight kind of reaction is needed, it hits the chemical pumps.
An estimated 1500 biochemical reactions are triggered and our bodies' hormones rush into our bloodstream, resulting in:
a boost in cortisol, which helps give quick energy, lower pain and increase immunity
increased blood sugar to feed our brain and muscles
increased heart rate
blood being diverted to the brain and major muscles, feeding our ability to think and react
platelet production increasing in anticipation of the need to help blood clot in wounds
endorphin levels rising, helping to dull and ignore pain long enough to respond actively to the threat
What a fantastic design! But what happens if we stay at a high level of alert?
The effects of sustained and elevated stress response are:
The hippocampus (the “shock absorber”) shrinks, making it more difficult to manage what we are experiencing, messing with our short term memory and perhaps leaving us stuck playing the memory of bad events repeatedly.
The amygdala, in constrast, begins to trigger alarm bells and chemical flows more quickly and frequently, leaving us feeling chronically alert and jumpy.
Frequent adrenaline spikes increase cholesterol levels and plaque deposits in arteries, creating higher risks of strokes or heart problems.
Changes in blood circulation patterns may create high blood pressure problems or migraine headaches.
Higher levels of cortisol over time damage white blood cells and impair our bodies’ immune systems, leaving us more vulnerable to infections, colds, flu and other illnesses or diseases.
Sustained higher levels of stomach acid may lead to ulcers and other digestive problems.
Chronic flows of endorphins lead to less effective pain relief and the potential for chronic pain or headaches.
Muted endorphin response may increase the temptation to consume more alcohol, caffeine or other substances that will temporarily mimic the sensations of normality or well-being.
Not so pleasant. I now understand that my dramatic illness didn’t arise from my being intrinsically deficient in some way – but from my not knowing how to bring my body’s reaction to stress back to a normal and sustainable state. In the next series of notes we will look at strategies for handling stress in a range of international environments.
An advance peek: It seems that exercise can help the hippocampus to grow again, and the amygdala’s responses to be brought back towards normal.
In a journal or on a pad, create a picture of yourself and stress. Ask how you know you are feeling stressed – what are your physical reactions, your emotional reactions, your cognitive reactions (things like putting socks in the fridge and forgetting why you went upstairs). On the same list ask how others know you are stressed. Do you behave or interact differently? My daughter notes that sometimes I am grumpy with her because I am stressed, not really because of what she is doing.
Then consider the ways that you manage stress when it comes into your life. This list of strategies which work at home will also be important when away. This is a good exercise to do with a partner or friend – someone close enough to help us recognize and manage our peaks in stress.