Meet Your Brain: The Hippocampus

The Hippocampus is a part of the emotional processing centre of the brain (the Limbic system). Hippocampus literally means ‘Sea Horse’ in classical Greek and it is so called because it looks quite uncannily like a sea horse. It has widely spread links to lots of other networks which make it a a really important centre for storing and retrieving conscious memories. The Hippocampus allows you to remember all those facts and figures you learnt at school, where you keep the spare batteries, what you ate for dinner, and where you spent your last holiday.

The Hippocampus and the Amygdala are closely connected. Because the Hippocampus acts like a librarian storing and organising information and the Amygdala acts to add emotional ‘tone’ to experiences the two brain centres co-ordinate to allow us to store and retrieve emotionally-based memories.

One of the fascinating studies that really illustrates how amazingly changeable the brain is was done on London taxi drivers who have to memorise an enormous amount of spatial information in order to be able to navigate successfully around such a vast city. Brain scans showed that these taxi drivers have significantly larger Hippocampi than is normal and also that the size of the Hippocampi increased the longer that they had been in the job.

The hippocampus is particularly vulnerable to the effects of stress. Cortisol, one of the bodies main stress hormones has been shown to be very damaging to cells in the Hippocampus leading to them shrinking, forming fewer connections and even killing off some of the neurons. This is why people who are under lots of stress frequently complain of having a “mind like a sieve”.  Such cortisol induced damage to the hippocampus has also been found in patients who develop post-traumatic stress disorder (PTSD).

Neurons in the hippocampus have also been shown to degenerate relatively early in the course of Alzheimers disease which is why one of the first and most profound symptoms of this disease is forgetfulness.

Also the hippocampus matures quite slowly and until it’s fully online we can’t generate conscious memories very well. This is why none of us can recall much that happened in our first few years of life- it wasn’t that we weren’t paying attention but we just didn’t have the hippocampal function to make conscious memories. At the same time of course we constructed millions of unconscious (implicit) memories which allowed us to learn fantastically complex things like talking and walking all without knowing how we did it.

So what can we do to care for this vital part of our brain? Well a lot of it comes down to “use it or lose it”. Learning new things helps us to grow bigger and more connected Hippocampi. Also avoiding or minimising stress can help to prevent cortisol-induced damage to the neurons of the Hippocampus.