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The brain of brains - The Pre-frontal cortex


We've all heard of these phrases - "think with your mind and not your heart", "let's put our brains together", "let's think deeply about this". 

Well, we now know that the brain has many different parts that perform many different functions. But one part, in particular, fits the stereotypical description of "brain" - the Pre-Frontal Cortex (PFC).

Let's first start with some unique features of the PFC. We'll then move on to the different functions which the PFC performs.

  • The PFC is the most recently evolved part of our brains. Reptiles, for example, have no PFC. All mammals have at least a little bit, while more advanced mammals like primates, dolphins, elephants, whales spot bigger and more developed PFCs. The human PFC is the most complexly wired of all.

  • Interestingly, the PFC is the part of your brain that is the latest to mature. Our PFC doesn't fully come online until we are 25. By definition, this also means that the PFC is the least shaped by genes and the most influenced by experience. There is a very good reason for this: your brain needs a longer runway to learn about social context - what is appropriate in different situations? Why is it ok to pay a stranger to cook you a meal, but not ok to pay your mother-in-law to cook the same meal? This is difficult and requires us to experience ourselves before we learn. This also strong hints at why teenage behaviour tends to be very different. More on this later.

  • Finally, the PFC carries a very special type of neuron. Neurons are the basic unit in your brain through which every thought, sensation, feeling, action happens. Amazingly, most neurons in our brains are very similar to the neurons in a fly's brain. Bar one exception - there is a rare and distinctive version of neuron in your frontal cortex called the Von Economo neuron - found only in a small handful of animals. The Von Economo neuron occurs only in 2 parts of our frontal cortex  - the insular cortex (which regulates gustatory and moral disgust - which is why you feel like vomiting whether you eat something disgusting or watch a moral disgusting scene) and the anterior cingulate cortex (this relates to empathy).

  • This entire paragraph sounds like a turn-off with all the scientific jargon - but it was a pretty big deal for us to find out about the Von Economo neuron. Besides all the new terms, the main thing to note is that the Von Economo neuron is rare in the entire natural world. The Von Economo is involved in very complex social decisions, and only a small handful of very socially complex animals have it.

Functions of the PFC


Before we get to the first function, this popular comic is completely inaccurate. Can you name why? You should be able to. 


Ok back to the functions:

1) It helps us make decisions

Should you eat chicken or fish? Watch Movie A or Movie B? Do you say something or not say something? Your PFC decides all of this. It acts as the final decider between emotions and cognition - I feel this way, but I think that way, what should I do? You turn to the PFC as the final decision-maker. 

2) It considers relevant information 

Say you are travelling to a country. Your frontal cortex starts to consider all the different things you might need and draws these out from previously stored memories. For example, it might consider that the electrical plug might be different; that you need to change currency; that the weather might be the opposite of where you are now, and you need to pack appropriately. Of course, the more experience you have garnered in an area, the wider the range of relevant information your PFC can draw up.

3) It helps us to focus on a task
Say you are on the pavement looking to cross the road. Your PFC focuses on traffic in front of you - is it safe for you to get across, and what is the optimal path to take (is it worth walking to the traffic light 50m down the road?) 

Now say you are on the pavement waiting for the bus. Your PFC focuses on identifying buses - a completely different shape and size from most other vehicles. Not only that, your eyes automatically look out for the bus number (whereas you might have simply not bothered if you were just crossing the road).

Being able to focus has obvious benefits, but also drawbacks in specific scenarios. You might be interested in these chapters:
- Heuristics: how and why we filter out information

- Creativity: how can we be more creative? 

4) Categorisation

What would you like to eat  Chances are that in your head you categorised your food: "I had th

But your brain is even more spectacular than that. Researchers from MIT trained a group of monkeys to differentiate between pictures of dogs and cats. Brain scans show that with learning, individual PFC neurons developed where some responded to dogs, while others responded to cats. Even though there are many types of dogs and cats, the monkeys were able to differentiate between the 2.


Now, try something warped. Combine pictures of dogs and cats to create a hybrid - say of 80% dog and 20% cat or 60% dog and 40% cat. The neurons in the PFC that recognise "dogs" respond to this hybrid. But what if the ratio was the other way around - 40% dog and 60% cat? Then the neurons in the PFC that recognise "cats" kick in. Our brains are really good at recognising patterns and categorising information.


There is however a cost to this. We become so attuned that The PFC groups apples and peaches as closer to each other in a conceptual map than are apples and toilet plungers. In a relevant study, monkeys were trained to differentiate between pictures of a dog and of a cat. The PFC contained individual neurons that responded to “dog” and others that responded to “cat.” Now the scientists morphed the pictures together, creating hybrids with varying percentages of dog and cat. “Dog” PFC neurons responded about as much to hybrids that were 80 percent dog and 20 percent cat, or 60:40, as to 100 percent dog. But not to 40:60—“cat” neurons would kick in there.

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