Inside Reily’s head, the emotions are sleeping in their room when suddenly an alarm bell rings and a demolition ball destroys the windows. Right after some construction workers appear and start destroying the whole place.

 

What’s going on?

 

 

Synaptic pruning

What the creators of the movie are trying to represent in these scenes is the synaptic pruning, a normal process in the brains of teenagers.

 

Neurons are connected through a space called synapses, where they release and receive chemical messengers (neurotransmitters) and electrical signals to communicate with each other.

 

Since we are born, the pace at which neurons create connections with other neurons around is really fast, and that allows our brain to absorb a huge amount of knowledge.

 

But as we grow, especially during adolescence, we need to filter what is important for us and what is not. Therefore, we need to clear synapses that we don’t usually use, that is the synaptic pruning. In other words, our body gets rid of weak connexions between neurons that won’t be relevant for us in the future.

 

In the movie, the construction workers would be immune cells, as the immune system is the one in charge of the synaptic pruning.

 

This process is essential to make important connections stronger and create mature neuronal circuits to develop an adult brain, and it’s controlled by our genes and our experiences.

 

Why do our experiences determine what connections are weak?

When we are babies everything is new for us. What we see, what we feel, what we eat. So neurons are creating synapses all the time. But there are experiences that we do over and over during the following years. For example, walking or using a spoon. 

 

Our brain knows that information is important, is relevant for us. So we can do those actions without even thinking, automatically. Those connections are stronger.

 

But other experiences didn’t prove to be as important. We barely use them, so they get weak. Those are the connections that are erased during the synaptic pruning. 

 

What happens if it goes wrong?

Some research shows that if the synaptic pruning doesn’t take place correctly, the brain would have more connections than it should and it is more likely to develop disorders such as epilepsy or schizophrenia.

 

References:

 

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7368197/ 

https://www.sciencedirect.com/topics/veterinary-science-and-veterinary-medicine/synaptic-pruning