Building Brains

For generations parents have watched children grab, chew and explore interesting objects in the world around them.  Whilst these sorts of behaviours have long been encouraged it is only recently that we have begun to understand their critical importance in healthy brain development.

Until the mid-90’s our knowledge of brain development remained limited however with the widespread introduction of the PET-CT scanner our understanding has vastly increased, with more than 80% of our knowledge developed since their arrival.

Like most aspects of development, our brain’s is dependent on both hereditary and environmental factors. Genetics certainly play an important role in our intelligence, however rather than setting the absolute level, hereditary factors seem to set an intelligence range, which is currently believed to be around 40 IQ points.  We now know that our environment in the first 3 years determines where in this range our intelligence will eventually fall.

The cerebellum is the part of the brain associated with higher order thinking processes and is responsible for abstract thought. Although it doesn’t fully develop until we are 8 years old the parts that are connected to sensory input start to develop earlier.  This explains why we are able to deal with objects we can see or feel before we can think about ideas with no sensory connection. New research indicates that our ability to solve problems and learn new tasks (or intelligence) is actually related to the thickness of the cortex which covers the cerebellum and not the overall size of the brain.

When we are born we have 100 billion brain cells called neurons, to begin with these cells are isolated from one another and have not yet formed the vast network which is necessary for us to think and to learn. As the we begin to receive stimulation which is sensory, novel and challenging these neurons begin to form connections with one another, with each one able to connect to 15,000 others.

For the first 3 years the brain is incredibly sensitive, forming connections at an astonishing rate and much more rapidly than at any other period. By our 3rd birthday they will have formed approximately 1000 trillion connections, twice as many as an adult has!  The more communication that occurs the more connections that are created, and although no more neurons are created, the proliferation of this expansive network causes the cortex to thicken.

During this period of intense proliferation each new stimulus leads to new growth of neural connections and the more connections that are made, the more possibilities that will exist.

There is no other period in life in which we come close to matching the rate of these accomplishments, which is hardly surprising when we consider the external changes that occur from birth to 3.  It’s during this first 3 years that we learn to speak, think and perform sophisticated tasks and lay down the neural foundations on which the rest of our development depends upon.

Between ages 3 and 9 the our brain enters a phase of consolidation in which the connections are pruned and refined with only those that prove to be meaningful and well used are kept.  To use language as an example, during our first year we make all sounds of all languages, and thus the neural connections required to make these sounds. However, unless these are regularly reinforced, then we lose these connections which is is why someone who learns a language after the age of 10 will never be able to completely get rid of their native accent.

After 3 it becomes more difficult for neural connections to be made, but until the hormones of puberty start to kick in the brain still has good potential to grow and change.  Interestingly during this period the child’s brain uses relatively more energy than at any other time in their life, with around 50% of the calories consumed by a child.

This is pointedly illustrated in cases where a child is born with healthy visual anatomy but with cataracts.  These are a clouding of the eyes lens that prevent light from entering the eyes, but can be removed with a simple surgery.  However the child will only recover the ability to see if the cataracts are removed before they are 2 years old. If they are removed after this the brain is unable to create the neural connection needed for vision and the child will remain blind. The first few year are a critical periods in the development of our brains which need to be correctly nurtured, and the opportunities to establish connections must not be missed.

1. Lessen-Firestone J. 1999. Building Brains. Ready to Learn Forums, Michigan