Brain to Z: A is for amygdala

For the first installment of Brain to Z, we're focusing on the amygdala...

Amygdala is the Greek word for almond. It refers to two correspondingly sized regions of the brain found deep within our temporal lobe. If you can imagine 2 lines, one passing straight through your eye and one through your ear, the amygdalae sit roughly where these two lines would intersect on both sides of your head. They play a large role in our emotional responses.

That’s not to say it’s the only part of the brain that deals with our feelings, of course. I mentioned before how deep within the brain the amygdala sits. As a general rule, the deeper you dive into the anatomy of the brain, the more primitive and universal the propensity for a particular response. For example, the brain stem, the deepest layer and first to form, is most responsible for controlling our non voluntary body functions like our breathing, or our alertness: things like our reflexes, flinches to shocks and so on.

The amygdala is just a few layers up and has a role in more complicated feelings and responses. It acquires information from our various sensory systems - our ability to see, hear and smell - and paints a picture combining all these inputs, which then connects with the parts of the body involved with emotional reactivity. When you encounter sudden danger, stress hormones are released and you may freeze. If you’re listening to music you like, you’ll feel an urge to tap your foot to the beat.

And it's not just using the information from our eyes and ears, it’s also working from signals delivered to it from other parts of the brain, from the stem to the cerebral cortex (the outermost layer) where the most complicated neural processes are occurring. It’s extremely effective at aggregating all this information and informing our response.

To help with efficiency, the amygdala causes us to build relationships between stimuli and responses. This is known as pavlovian association, so named after some of the most famous experiments in psychology.

Ivan Pavlov was a physiologist studying digestion in dogs. While investigating the salivation process, he realised that his test subjects, before the food had even appeared, were beginning to salivate as soon as the person feeding them had entered the room.

To investigate further, he conducted experiments where he rang a bell before his dogs were fed. Once they’d become accustomed to this noise before meal times, ringing the bell caused them to salivate without any food being delivered.

The amygdala plays a vital role in this process, recognising the biologically significant stimulus the dogs were exposed to (in this case the sounds of the bell) and triggering the emotional response (the saliva forming in their mouths). An extremely significant finding, if a little cruel!