How do the structures and functions of children’s brains develop? With reference to relevant research evidence, examine the relationship between brain structure and function in the developing brain. This essay will evaluate the relationship of the structure and function of the human brain specifically in the area of language. The structure of the brain relates to how the brain is physically made-up. The different roles which areas of the brain become responsible for relate to the function of the brain. Initially the prenatal and postnatal brain structure will be considered, followed by possible hypotheses as to how the structure relates to the functions in the brain. Language development will then be used to consider these hypotheses.
The prenatal brain development consists of three main sections. Firstly the nerve cells called neurons multiply through cell division. These cells then begin to move to their final resting positions. This occurs in two ways. Active migration, in the cerebral cortex, involves the movement of the new cells past the older cells. In other areas of the brain the migration is passive, with the newer cells pushing the older cells further out. Finally the cells begin to differentiate taking their final form. This involves the growth and branching of dendrites. Dendrites pass on and receive signals to and from other neurons. Synapses (points of communication between neurons) and myelin (a sheath which helps the conduction of the signals) also begin to develop at this time. Myelin is important as if this process is delayed the conductivity of the neurons is affected. An incredibly large number of connections are formed at this time (Mareschal et al. 2004).
After birth the brain continues to increase the number of neurons, dendrites, synapses and the production of myelin. The baby is now interacting with an environment which is richer in stimuli than the mother’s womb had been. The vast number of connections begins to prune itself with the best connections remaining in place and those of least value being discarded. This is one way in which different areas of the brain begin to become specialised for different functions.
As the brain grows so the specialisation of different areas of the brain increases. If an area of the babies brain becomes damaged (e.g. in childbirth) there is the ability for other areas of the brain to take over the specialisation of the damaged part of the brain. This ability within the brain is known as plasticity and is characterised by neurons not yet achieving specialisation Mareschal et al., 2004). As the baby develops the brain areas become more specialised so that if a ‘normal’ development occurs the functions which different areas of their brain are responsible for are approximately the same as other adults who have had a ‘normal’ development.
This selectionism involves the amount of use a neural connection receives. If the connection receives a lot of stimulation then it will remain in place and become increasingly encapsulated (separate and more specialised). Those connections which are not used become redundant and eventually cease to work. This means that the brain becomes separated into different functional units called ‘modules’ (Mareschal et al., 2004).
These structural modules are known as neural modules and are real. There are also hypothetical cognitive modules which attempt to explain how the different neural modules work. Fodor (1983) believed that cognitive modules existed and that these were innately predetermined (nativist viewpoint). He believed that the brain worked like an information processor, it receives inputs and processes them and the environment which an individual child is in does not affect this process. Fodor’s theory believes that the modules are domain specific and encapsulated (each module performs its own task regardless of what may be happening to other modules). He also believed that this process was mandatory (no conscious control) and due to these properties were very efficient.
This theory is disputed by Karmiloff-Smith (1992) who also believed that cognitive modules exist but believed that the modules were more epigenetic and that the environment which a child is in can affect the development of the modules (constructivist viewpoint). She hypothesised that the cognitive modules have a genetic predisposition to perform a certain role which allows for flexibility within the system through interactions with the environment. In other words that modules are created because of the child’s development and interactions with the environment.
Fodor’s hypothesis would infer that if the language area of the brain was damaged that no other part of the brain could take over this function. This is not the case and it has been shown that other areas of the brain can take over this function (Reilly et al. 1998). This would seem to indicate that Karmiloff-Smith’s theory holds more weight as it is the brain’s interaction with the environment through the stimulation of neuron pathways that ensures that another part of the brain takes over the language unit. It seems that perhaps the brain has an innate predisposition to develop functions in a certain area and that if this is not possible it has the plasticity to adapt.