Evolution of the Brain
As indicated in the previous Newsletter the ‘learned’ behaviours commence at the time the child is born. During this early stage of development, the volume of synaptic connectivity is at its peak. This is the formation of neural pathways that initiate a behavioural response to a particular set of homeostatic conditions. This ‘construction’ is not instantaneous but, through trial and error the actions that get the best response are repeated and by continual repetition of this association between stimulus, discomfort, action and consequential relief, a circuit is born.
These attempts to adjust their current physiological state continue until there is some success. Then through repetition the strength of these successful connections increases until they become dominant and are myalinated to become fixed in the structure of the brain. This myelination or ‘insulation’ is supported by glial cells; a type of supportive product that does not conduct electric impulses. There is no definitive appreciation for the function of these cells but I suspect they perform some supportive function in the brain. Nature rarely retains useless materials in such abundance.
This crude description of what happens is at its peak in early childhood. 90% of the brain’s development occurs in the first five years. This is a time when there is an oversupply of neurological materials available to support the learning of new actions. Importantly there are crucial periods, windows of opportunity when the presence of the required material to build synaptic connection, and retention is increased providing optimum conditions for the construction of particular networks.
The development of sight provides a great illustration of the need for stimulus at the time the brain is geared for the acquisition of a new skill. If a child is born with cataracts on their eyes and those cataracts are not removed by about ten months that child will be functionally blind. Even if the cataracts are removed after the critical period and the stimulus is available, the rich neural environment that was there has been removed. This is an example of the ‘use it or lose it’ maxim and a further example of the loss of plasticity in the lower levels of the brain over time.
Those neurons that are not used wither through disuse and eventually are discarded, a process called pruning where the unused neuron cells are removed to make the newly formed connection still more efficient. The effect of this pruning is that in the first three years a child has over 1,000 trillion potential neural connections but the time they reach adolescence this is halved to 500 trillion a number that remains fairly stable for the rest of their life.
Early childhood is a time of great plasticity, a time when new circuits are easily formed and retained. However, once these new circuits are formed and myalinated this plasticity decreases, the newly formed neural pathway are ‘’locked in’. The result is that these behaviours are difficult to change in the future, the required cells have been pruned and the existing behaviours are extremely durable.
This lack of future plasticity explains why the learning that takes place in early childhood is difficult to modify. When you consider that they are permanent this is only an advantage if they have been learned in a functioning environment. However, if the behaviours are learned in a dysfunctional environment these will clash in a functional classroom. This is the fundamental reason cognitive interventions to change the disruptive behaviour of children raised in abusive and neglectful environments are ineffective.
Learning continues throughout our lifetime but decreases as we age and our brain development reflects that reduction. The brain develops in two ways, from the bottom up, that is behaviours in the midbrain and limbic system, which are predominantly social skills and from the back to the front! The back to front evolution reflects the emergence of our intellectual brain, that part we want to access in our lessons. The illustration shows this development.
This progression to adulthood is said to be completed around the age of 28 for males and earlier for females, I will leave that inference without comment! This is when the frontal lobes are developed.
This progressive characteristic is important for our expectations of behaviour for children of different ages. It has been described as the first ten years we become people, with the skills of communication, survival and affiliation and the next we become reproductive people where we must learn a new form of intimate attachment. This reflects Dawkin’s hypothesis we are driven to survive and reproduce!
Our focus is on those children whose behaviour clashes with that required in a functioning classroom. It must be remembered that even though all children will be developing behaviours those children who have not learned the previous functioning skill set will require extra support. When the teacher understands this it helps inform their approach to how they teach their academic programs. Students who are having difficulty learning to relate socially, that is those who are highly disruptive are not going to improve their NAPLAN results until they improve their affiliation skills!
The next illustration shows these phases of development.
In summary, as we move towards maturity we develop in a three staged, hierarchical fashion that reflects our triune brain with:
- Development of the physical self, our reflexive responses in the brain stem and midbrain that cater for changes in our physical homeostatic status.
- The emergence of our objective self in our limbic system where we experience the external world as objects and others. We learn to socialise!
- The final development is in our cerebral cortex, our intellectual brain which allows us to ponder situations that are not easily resolved.
It is the last part of the brain we want in the classroom however this will not be available unless the lower functions are in homeostatic equilibrium. This is why the management of disruptive behaviours is the most important skill a teacher should have. A fact that is ignored by academics and bureaucrats!
