Amygdala, cortex, heart: are we still evolving?

As I mentioned in Our third brain: the heart, I find the research neuroscience has been doing in recent years on the heart as a cognitive and emotional centre fascinating. This time I want to talk to you about how human beings have gradually developed different parts of their central nervous system, and how the idea of the heart as our third brain could be seen as a continuation of the evolution of our mind.

Let’s get to it…

The limbic system

Since the dawn of time we have used the limbic brain, the most primitive part of our brain, which is basically in charge of our survival and our emotions. The amygdala is the most important element of the limbic system, and its job is to warn us when something threatens our survival. Over time and through evolution, our limbic system has taken on new functions, so that nowadays it also warns us of psychological threats, that is, anything that threatens our mental stability or causes us psychological stress. To put it simply, nobody needs to threaten you with a knife, and you don’t need a lion a metre away, for your amygdala to fire. It has now also learnt to fire when you sit an exam and your mind goes blank, to give one example. One threatens your life and the other threatens to ruin your summer; there’s no comparison, but your amygdala doesn’t care: it will react in exactly the same way. Another interesting fact is that the information processed by our limbic system travels much, much faster than the information processed by the cerebral cortex. This makes a lot of sense: if the amygdala is in charge of our survival, it needs to work extremely fast to send signals to the rest of the body and activate the three famous survival responses: flight, fight or freeze. Depending on various factors, one of the three will be chosen.

What’s more, our limbic system records anything that was a threat to each of us in the past (physical or psychological). So when it perceives a situation that is the same as, or similar to, that past one, it fires to protect us. If we’re functioning well and the threat is real, we’ll act accordingly and save our lives. If we’re functioning well and the threat wasn’t real, we’ll regulate the signs of that activation in the moment and calm down. If we’re not functioning well because we have some kind of disorder related to limbic system dysfunction, we won’t respond adaptively. Post-traumatic stress disorder (PTSD) would be a very good example of a dysfunctional limbic system, as the amygdala is overactive and fires far more often than it should. This happens because the person overestimates danger (perceives as a threat something that isn’t really one) and is in a constant state of hypervigilance to “protect” their physical and psychological integrity.

The cerebral cortex

Over time, human beings evolved into the “mental era” and began to use (and therefore develop) the cortex, or cerebral cortex. In principle, this is the most evolved part of the brain. The cortex processes the information coming from our environment, filters it, rationalises it… helping us act accordingly. To put it simply, it’s what helps you hold a meaningful conversation, study, read this article and take in the information it contains… to name a few examples. The cerebral cortex represents our mental side, our cognition. It’s the main reason we have all the technology we have today. Why? Because it’s the part of our brain responsible for our imagination and creativity. Without it there would be no progress, because human beings wouldn’t be able to imagine, and therefore couldn’t think of something that doesn’t exist in order to then create it in the world of the senses, our world. The cortex is what runs our everyday life, the ordinary moments, when emotions are present at a low level or simply not present at all.

The cortex will take the lead as long as emotions aren’t running very high. If, for example, you’re working calmly at your computer, your cortex will be the one at work. But if you suddenly overhear something about redundancies while your boss is looking at you from across the room, unless you don’t care about your job, your amygdala will fire and your cortex will take a back seat. And what does that mean? That you’ll try to carry on writing your report, but you won’t get a single thing right, because your emotions are at their peak and all you can think about is your (supposedly) imminent dismissal, how you won’t be able to pay the mortgage, and a whole cascade of catastrophic scenarios that will have played out in your head in a split second. Palpitations, sweating, dizziness, a dry throat and a long list of other possibilities will be your body’s way of reacting to what your amygdala has decided is a threat.

To put it simply, when intense emotions are involved, the amygdala holds all the cards. Hence the familiar “I’ve frozen, I can’t think”. Fortunately, under normal circumstances, the amygdala wins battles but not the war.

And the heart?

Nowadays, some professionals are considering the latest findings on the functions of the heart as part of this evolutionary process, which began with the limbic system and continued with the cerebral cortex. Does the heart represent a more evolved form of our cognitive and emotional world? Could it give rise to higher levels of consciousness? In the previous article I mentioned the hypothesis, still unproven, that the heart might process emotions free of memories. Could this represent emotional processing at a higher level, leading to better management of our emotions? Is there really a link between intuition and information processing through this organ? What would the implications be if so? If we were to reach the so-called heart-brain coherence I mentioned in that article (a concept that is still being researched)… would that mean making maximum use of our cognitive abilities? And if so, would it mean developing abilities we can’t even imagine right now? For now these are open, and largely speculative, questions. We know that some people stand out in certain mental abilities far above most others; it would be interesting to study certain variables related to this in that group of people so that we can keep making progress in this field.

These are just a few of the interesting questions that, hopefully, neuroscience will answer in time. There’s a lot to say on the subject, and we’ll come back to it another time.