The differentiation of the cerebral cortex into different structural areas results in a brain that may have different ‘functional units’. These units, or modules, specialise in processing information in different ways. It is important to highlight the distinction between brain structure and brain function. Brain structure is the physical make-up of the brain and is made up of structured units called neural modules. The existence of these modules is proven with evidence. The brain structure relates to how the brain operates with cognitive modules providing a way of thinking how different functions are performed; these cognitive modules are hypothetical constructs and there is no real evidence of their existence. It is these hypothetical cognitive modules which will be discussed further in this paper.
The developmental process raises the debate as to whether the brain structure and functions are innately predetermined or whether development is influenced by other external factors. There are two main arguments of cognitive development in regard to specialist brain structure and functions. The nativist approach proposes that children are born with an innate or genetically pre-specified aptitude for development. Fodor (1983) is hugely influential among cognitive development theorists. His nativist viewpoint believes that humans are born with an innate capacity to develop information processing systems which allow children to make sense of the world. His theory ‘modularity of mind’ suggests that modules are rapid processing systems which are domain specific, encapsulated, extremely efficient and happen independently of conscious control. In contrast, the constructivist perspective as advocated by Karmiloff-Smith (1992) puts forward that children develop as a result of interacting with a complex environment. Although it is recognised by psychologists that genes inevitably react to the environment so could never be an exclusive factor; the nativist view is that as aspects of development apply to all children regardless of their environment arguing it is due to their genetic make up rather than external factors.
This can be shown in the writings of Mehler & Duprox (1994) who documented the case of a well-known composer who suffered a stroke which left a cerebral legion of the left hemisphere of the brain resulting in loss of speech. His musical abilities were unaffected; he could still decipher scores by ear and read music by brail. Interestingly, it left him unable to decipher texts where letters are identical symbols in brail to musical notes. This according to the nativist perspective suggests an innate function that musical ability would be a function of the right hemisphere and linguistic competence the left hemisphere. This illustrates a disassociation between language and other cognitive functions.
Fodor (1983) recognised the environment had an impact over the course of evolution of the human brain structure but did not believe it played a significant role in an individual’s development. Although Karmiloff-Smith (1992) agrees with basic notion of encapsulated cognitive modules she contests that these are genetically pre-defined structures of modularity. The constructivist framework suggests that the mind becomes modularised as a result of development, strengthened pathways influenced by the environment. It recognises there may be a number of innately pre-specified controls but this is limited. The mind becomes more modularised as development precedes taking into account the plasticity of early brain development. The constructivist view of modularisation is more epigenetic than a nativist perspective. Epigenesis acknowledges that development occurs as a result of interaction between genes and their environment.
Chomsky (1965) argued that children have an innate aptitude to learn complex grammatical systems and have an inherent language acquisition device (LAD). Pinker (1994) recognised that language alone cannot substantiate nativist theory. However, the fact that highly structured complex language appears in all human groups suggests an innate characteristic in human species. He put forward four basic arguments to substantiate his theory. The first involves the development of pidgins into creoles. He elicited work from linguist Derek Bickerton who studied migrant workers to the USA. The workers developed a pidgin. This is a non-grammatical form of communication between non-native speakers to converse with each other. The interesting aspect of the study is that the children of the migrant workers then developed a fully-fledged Creole, a grammatical language with structures and constructs similar to those of conventional languages. Pinker argues the children were responding to an innate characteristic of development in that every child reinvents language anew as they use it throughout development. Pinker’s second point relates to the poverty of input and he draws upon work from Chompsky to illustrate the argument. Chomsky (1965) posits that children are able to produce language they have never heard before such as grammatically correct questions which are comparably complex. This implies children are able to generate language anew as they have an innate grasp of grammatical structure. His third basis is connected to the universality of potentially arbitrary grammatical rules; proposing that as auxiliary words move to the beginning of the sentence to form a question in languages this reflects a commonality in structure of the human brain. His last point correlates with neuropsychology; arguing that there is an identifiable region in the brain for language and this would suggest a set of genes were genetically predetermined.
To support the argument that regions of the brain are innately specified, areas of the cortex would need to be identified as crucial to language development. However, there is evidence to suggest that a variety of regions can support language acquisition. The term ‘equipotentiallity’ undermines nativism theory suggesting that at birth left and right hemispheres of brain both have ‘equal potential’ for developing language.
Reilly et al (1998) examined the effects of focal legions which happened before six months of age into infancy and their subsequent narrative skills. The study found that brain injury group showed some delay in grammatical and narrative skills when compared with the control group. Initially there was a large gap in performance between the brain injury and control group; over time this gap between the groups performance reduced significantly. It clearly showed cognitive development in both groups and highlighted the adaptable functions of the brain arguable due to the influence of the environment. Stiles and Thal (1993) also studied children who possessed focal legions in a longitudinal study. The study showed language delays irrespective of which side the hemisphere was damaged. Interestingly, the most significant delays in word comprehension were among the right hemisphere legion group. This suggests regions responsible for language acquisition are not those necessarily those used for language processing in the adult. The evidence from the previous studies show that the left temporal lobe is clearly related to language processing in adults; and shows a bias toward the processing system in building neural modules that specialise in language. Johnson (1997) notes that although regions left temporal lobe are best suited to process language it is not critical as there is sufficient plasticity in the developing cortex to take on these functions.
Neville et al (1998) used function magnetic resonance imaging (FMRI) to study activity in the brain responding to language stimuli with both deaf and hearing participants. The investigation showed there was activation in the left hemisphere language areas when processing language stimuli for both sets of participants corresponding with the association of language processing in the left hemisphere irrespective of form of language. Both written and sign language were processed in related areas of the left hemisphere. The right hemisphere also showed increased activity for deaf participants, this could suggest a captured language process related to the visuo-spatial information of sign language. The investigation showed bias in the left hemisphere toward language processing. However, the result should be taken with some caution as a single study limits the validity of an investigation.
In the brain structure the prefrontal cortex consist of one third of the brain surface and is considered to be crucial for higher cognitive abilities. Its main functions include planning and execution of sequences of actions, the maintenance of information over short delays in working memory and the ability to inhibit a set of responses which are appropriate in one context but not another, these processes are known as executive functions. Structural changes in the prefrontal cortex can related to various aspects of the cognitive and behavioral development of children. It is associated with the early stages of development of a new skill with involvement decreasing only when the skill has been developed. Johnson el al (1998) looked into the areas of the brain which were associated of attention shifting. He found in infancy there is greater prefrontal activity for these tasks than in adults and this may be due to early developmental stage in infants. It could be argued that these skills in adulthood have already been learned and relocated to a more specialised area of the cortex.
The extent to which cognitive development can be understood in terms of the specialisation of function in specific structures of the brain remains inconclusive. There is research which supports notions from both sides of the debate. The evidence to support the nativist approach does indicate there is some kind of predisposition in human infants to develop skills and language. This may be true as the brain is known to develop language even if there is some structural damage to the area associated with language processing. However, there is evidence to compromise the genetically pre-determined specific cortical regions such of that of plasticity and equipotentiality. The prefrontal cortex is linked to cognitive development and higher cognitive functions and may be influential in early developmental processes but much work is needed to relate the structure and function of the brain to development. The research is complex but there is a balance of evidence to suggest that most regions of cortex differentiation results in an epigenetic system of interaction between molecular and genetic factors rather than a predefined structure of modularity.
References
Changeux, J.-P. (1985) Neuronal Man: the biology of mind, New York, Pantheon.
Chomsky, N. (1965) Aspects of the Theory of Syntax, Cambridge, MA, MIT Press.
Fodor, J. A. (1983) The Modularity of Mind: an essay on faculty psychology, Cambridge, MA, MIT Press.
Hebb, D. O. (1949) The Organisation of Behaviour: a neuropsychological approach, New York, Wiley.
Huttenlocher, P. R. (1990) ‘Morphometric study of human cerebral cortex development’, Neuropsychologia, vol. 28, pp. 517–27.
Johnson, M. H. (1997) Developmental Cognitive Neuroscience, Oxford, Blackwell.
Johnson, M. H., Tucker, L. A., Stiles, J. and Trauner, D. (1998) ‘Visual attention in infants with perinatal brain damage: evidence of the importance of anterior lesions’, Developmental Science, vol. 1, pp. 53–8.
Karmiloff-Smith, A. (1992) Beyond Modularity: a developmental perspective on cognitive science, Cambridge, MA, MIT Press.
Keslo, S. (1995) Dynamic Pattern: the self-organization of brain and behavior, Cambridge, MA, MIT Press.
Marechal, D., Johnson, M. H. and Grayson, A. (2006) ‘Brain and Cognitive development’ in Oates, J. and Grayson, A. (2006) Cognitive and Language Development, Milton Keynes, The Open University
Mehler, J. and Dupoux, E. (1994) What Infants Know, Oxford, Blackwell.
Neville, H. J., Bavelier, D., Corina, D. et al. (1998) ‘Cerebral organisation for language in deaf and hearing subjects: biological constraints and effects of
experience’, Proceedings of the National Academy of Science, USA, vol. 95, pp. 922–9.
Oates,J. (2006) in The Open University (2006) Media Kit, ED209: Child Development DVD-ROM (Media Kit Part 3, Video Band 6: Finding a Voice: Alex and Leigh), Milton Keynes, The Open University.
Pinker, S. (1994) The Language Instinct: the new science of language and mind, London, Penguin.
Reilly, J. S., Bates, E. A. and Marchman, V. A. (1998) ‘Narrative discourse in children with early focal brain injury’, Brain and Language, vol. 61, pp. 335–75.
Stiles, L. and Thal, D. (1993) ‘Linguistic and spatial cognitive development following early focal brain injury: patterns of deficit and recovery’, in Johnson, M. H. (ed.) Brain Development and Cognition: a reader, pp. 643–64, Oxford, Blackwell.
