Origin of the Human Brain / by Chris Baldwin

By Justin

Week 2

So last week I mentioned the three layers, they are Reptile, Limbic and Neocortex. Last week I mentioned the building the house analogy, you build the foundation first, then walls and ceilings. The human brain was “constructed” much in the same way, the reptilian brain being the oldest foundation of brain which we inherited from prehistoric reptiles.

 

Sooooooo this week...

The first thing I’d like to focus on this week is the human brain and its origins, last week I touched briefly on the reptile brain and its basic innate functions, this week I’d like to expand on the three sections of the brain and what they are responsible for.

Viewing it in three distinct groups is referred to as the The Triune Brain, First proposed by Neuroscientist Paul D. MacLean in the 1960s. The human brain is much more complex and is comprised of many more “sections” but in terms of evolution it actually splits up quite nicely into these three bits. A nice example of this is that pretty much all reptiles alive today have a version of the reptilian brain that we have, just without the other two sections.

 

Reptile Brain

The text book name for this is the brain stem.  It comprises a central nervous system (nerves and muscles n stuff that makes you move and not die), and a “computer” to control things like breathing, body temperature regulation and heart rate. Imagine if you had to manually make sure you took regular breaths and that your heart actually pumped blood... you’d go mad, well you wouldn’t you’d probably die!

The reptile brain also takes control of spacial awareness, which boils down to, “That tree is over there and im over here. There’s some space between us I can move around in before I hit that tree!” This obviously helps with perception and judging how far away something is, but also helps with knowing what’s yours in terms of territory. So we can “mark off” an area which is classed as “safe” or “mine”. This means we can set up “mental barriers” in our heads relating to the space around us. If something crosses the line into what is ours, it is automatically a threat and will probably get eaten... maybe. Either way having “territory” and being specially aware of it helps to identify possible threats.

It is also handy when knowing the difference between something being small or far away. This is a massive thing in terms of perception which I'm going to touch on later in another essay. But, for now, it’s basically, “This cow is small, and that ones far away, yeah?”

 

Limbic System

The limbic system is the 2nd layer of the brain. This is comprised of a number of other smaller parts, all of which control emotional responses and behaviour; especially behaviour associated with survival. This will play a key role later in these blogs.

There are several parts of the brain that make up the limbic system but to keep things short I’m going to focus on the Hippocampus and Amygdala.

Hippocampus

The Hippocampus’ primary function is that of memory. It sort of stores events, short-term, before passing them other parts of the brain for more permanent storage. An example of this would be learning a new task; your hippocampus would catalog the learning so the information is passed onto your cerebral cortex for long term storage, and your motor centres to store how to move when performing said task.

Connections made by the hippocampus also link into other parts and help with memory association with things like scents etc. This is a vital function for survival! The smell of a predator would be associated with danger and allow you to run away, or prepare to fight before you have seen it; or more importantly before it has seen you! Another service provided by the hippocampus in terms of memory/emotion is to ensure empathetic reactions. For example, if you see somebody crying you feel the need to hug them.

 

Amygdala

The amygdala plays a key role on your emotional responses, including pleasure, fear, panic etc. Another part of the Limbic system is the Basal Ganglia, this works with the amygdala and regulates “reward” emotions. It also regulates habit-formation based on repetition. This can be good when learning a new task and feeling proud that you have progressed; but conversely bad when forming an addiction to drugs.

The Amygdala talks to the hippocampus when attaching emotions to memories; especially “negative ones”. This may sound like bad idea, but if you’re hunting one day and you see a predator, the following day (if you go back to the same area), you will remember the predator and also the feeling of fear you felt previously - so you’re more likely to not go back.

 

Neocortex

This is the top and final layer of the mammal brain. I’m now specifying mammal as this is where we split away from others species in terms of brain structure. Humans have the largest Necortex of all mammals. The Neocortex is split into 4 parts; the frontal, temporal, parietal and occipital lobes. The main function of the Neocortex  is essentially information processing. From visual information, to touch, to sound. Current theories also suggest that human consciousness also originates in the Neocortex. It’s important to note here that although all “higher” brain function takes place in the Neocortex, the driving forces and emotions attached to these functions still originate from the reptile brain and limbic system. This is, effectively, like having a modern super computer that is powered, regulated, and uses hazard protection systems from the days of steam...

This point is VERY important later on.

 

NEXT WEEK

Next week we take a look at the birth and cementing of consumerism and the origins and evolution of advertising.