Why Do We Have Brains?
The brain directs and coordinates movements and reflexes, registers sensations and is the supreme nervous organ by which man acquires knowledge and the power to use and adapt it. It shapes our personalities, and without it we would be more helpless than the tiniest human baby.
There are three main parts of the brain: the forebrain (or cerebrum), the midbrain and the hindbrain. They have the consistency of soft jelly and are protected by three membranes (meninges), a tough outer envelope called the dura and a watery fluid (cerebrospinal fluid) which acts as a support and a cushion. The brain is connected to the spinal cord, and its surface is highly convoluted.
The cerebrum which forms nearly nine-tenths of the brain is divided into two halves (hemispheres). Generally the left half of the cerebrum controls the right half of the body, and the right half of the cerebrum controls the left half of the body. Some areas are connected with the special senses of man, but there are so-called “silent areas” which scientists believe are connected with memory and the association of ideas. The thalamus, a mass of gray matter which is buried in the cerebrum, is the source of instinctive feeling and emotion.
The midbrain is concerned with eye-movements, while the hindbrain contains the nerve cells responsible for breathing, heart action, and digestive juices and so on. The cerebellum, a part of the hindbrain, plays an important role in the execution of the more highly skilled movements.
The primary purpose of a brain is to move around our environment in a meaningful way. In fact, one could even argue that most of the brain is dedicated towards actions. If we consider that the basic building block of the brain is the neuron, then it comes as a surprise to most to find out that the majority of neurons are not in the association cortex where “higher” thought processes are generated. Of the estimated 86-100 billion, around 80 percent are to be found in the cerebellum, the bulbous structure at the base of the brain at the back that controls our movements.
People often assume that animals with bigger brains are more intelligent because they have more brain cells. It is true to some extent but it is not the number of neurons that determine intelligence but rather the number of connections between the neurons. So the ‘association cortex’ is just that, the 3mm thick outer layer of the brain that stores information for processing through the vastly interconnected networks of associated activity. And this of course, is the secret to the processing capacity of the brain.
Each neuron has up to 10,000 connections, which means that the number of potential different patterns of neural activity is virtually infinite. With just 500 neurons you have the potential for more different patterns than the estimated number of atoms in the observable universe!
Our big brains are mostly made up of connections between neurons, around 160,000 km—enough in an individual human brain to circumnavigate the equator four times. The purpose of all these connections is to store patterns of neural activity that are the basis for sensations, perceptions, cognitions and other important brain functions we possess.
However, we must remember that these abilities all serve the primary function of action. Without the ability to act, we would be completely at the mercy of the environment, which is why we evolved a brain to act on the world. After all, Mother Nature doesn’t select for a good idea, its action that speaks louder than words.