To what extent can cognitive development be understood in terms of the specialization of function in specific structures of the brain?
Developmental cognitive neuropsychology seeks to understand and explain the relationship between the human brain and its function. One might consider the extent to which cognitive development can be understood in terms of the specialisation of function in specific structures of the brain. Two contrasting theories of functional specialisation will be presented, debating the means by which brain functions develop and contesting the influence environment bears upon the maturing brain. To enable exploration of this topic, an account of key concepts of brain development will be offered throughout. The essay will then turn to the function of language. The extent to which language is reliant upon specific cortical structures has been the subject of keen contention, and affords rich research from which to discuss whether particular regions of the brain have an innately pre-specified role to support particular cognitive functions. Research related to the prefrontal cortex will also be considered, drawing the essay to its conclusion.
To explore cognitive development in terms of the specialisation of function in specific cortical structures, one must outline association between structural differentiation and functional specialisation. The typically developed adult brain shows predictable associations between specific cortical areas with particular cognitive functions. Prior to maturation, the developing brain demonstrates increasing differentiation in both structure and function of cells, with structural changes directly affecting functional capacity. The structural differentiation of neural pathways through the processes of dendritic growth, myelination and encapsulation result in cortical areas highly efficient in supporting particular types of information, or specialised functions. The underlying reasons for the organisation of the brain in this manner are unclear. One theory seeking to explain the relationship between cortical areas and corresponding functions suggests the brain is organised into functional units, or ‘cognitive modules’. These hypothetical modules support particular functions, such as language, and are highly specialised to process particular information.
There is significant dissent regarding the means by which development of the brain domain-specific modules occurs, centring largely on the extent to which cognitive development is genetically determined or epigenetic. The theories of two main protagonists are briefly discussed here. Fodor (1983) presents a domain-specific hypothesis of cognitive development, offering a phylogenetic viewpoint from which functional specialisation is supported by genetically determined cognitive modules – this development of the brain Fodor terms modularity. Fodor’s theory centres on the perceptual input systems, which he proposes, process stimulus information taken from transducers, which sense stimuli, and deliver a representation of this to the central processor for higher-cognitive functions. Fodor refers to these input systems as modules, stating that the act of cognition begins at the point at which this specialised processing takes place. Fodor states that input systems have four fundamental rudiments: they are domain-specific, each module only processing one type of information; the modules work independently of one another (encapsulation); the processing is mandatory and lastly, that input systems are rapid. Development, for Fodor, is a result of maturation, not interaction with the environment, with predetermined links between the development of specific regions of the brain with the acquisition of cognitive and motor abilities.
In contrast to Fodor, Karmiloff-Smith (1992) proposes an epigenetic theory of modularisation, in which cognitive modules develop to support specific types of information-processing as a product...