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Neuroconstructivism is a theory that states that gene–gene interaction, gene–environment interaction and, crucially, ontogeny are all considered to play a vital role in how the brain progressively sculpts itself and how it gradually becomes specialized over developmental time.
Supporters of neuroconstructivism, such as Annette Karmiloff-Smith, argue against innate modularity of mind, the notion that a brain is composed of innate neural structures or modules which have distinct established evolutionarily developed functions. Instead, emphasis is put on innate domain relevant biases. These biases are understood as aiding learning and directing attention. Module-like structures are therefore the product of both experience and these innate biases. Neuroconstructivism can therefore be seen as a bridge between Jerry Fodor's psychological nativism and Jean Piaget's theory of cognitive development.
Development vs. innate modularity
Neuroconstructivism has arisen as a direct rebuttal against psychologists who argue for an innate modularity of the brain. Modularity of the brain would require a pre-specified pattern of synaptic connectivity within the cortical microcircuitry of a specific neural system. Instead, Annette Karmiloff-Smith has suggested that the microconnectivity of the brain emerges from the gradual process of ontogenetic development. Proponents of the modular theory might have been misled by the seemingly normal performances of individuals who exhibit a learning disability on tests. While it may appear that cognitive functioning may be impaired in only specified areas, this may be a functional flaw in the test. Many standardized tasks used to assess the extent of damage within the brain do not measure underlying causes, instead only showing the static end-state of complex processes. An alternative explanation to account for these normal test scores would be the ability of the individual to compensate using other brain regions that are not normally used for such a task. Such compensation could only have resulted from developmental neuroplasticity and the interaction between environment and brain functioning.
Different functions within the brain arise through development. Instead of having pre-specified patterns of connectivity, neuroconstructivism suggests that there are "tiny regional differences in type, density, and orientation of neurons, in neurotransmitters, in firing thresholds, in rate of myelination, lamination, ratio of gray matter to white matter," etc. that lead to differing capabilities of neurons or brain regions to handle specific functions. For example, the ventral and dorsal streams only arise because of innate differences in processing speed of neurons, not an innate selection to be either ventral or dorsal by the respective neurons. Such a differentiation has been entitled a domain-relevant approach to development.
This contrasts the previous domain-general and domain-specific approaches. In the domain-general framework, differences in cognitive functioning are attributed to overarching differences in the neurons across the entire brain. The domain-specific approach contrasts this framework by arguing for inherent, specific differences within the genes which directly control a person's development. However, domain-specificity cannot be ruled out by neuroconstructivism. Instead, it offers a developmental approach that focuses on change and emergent outcomes. Such change leads to domain-specificity in adult brains, but neuroconstructivism argues that the key component of the specificity occurred from the domain-general start state.
Every aspect of development is dynamic and interactive. Human intelligence may be more accurately defined by focusing on the plasticity of the brain and its interactions with the environment rather than inherent differences within the DNA structure. Dissociations seen in Williams syndrome or autism provide neuroscientists with a means of exploring different developmental trajectories.
Neuroconstructivism uses context to demonstrate the possible changes to the brain's neural connections. Starting with genes and incorporating progressively more context indicates some of the constraints involved in development. Instead of viewing the brain as independent of its current or previous environment, neuroconstructivism shows how context interacts with the brain to gradually form the specialized adult brain. In fact, by building on preexisting representations, representations become increasingly context bound (rather than context free). This leads to "restrictions of fate" in which later learning is more restricted than earlier learning.
Previous theories have supposed that genes are static unchanging code for specific developmental outcomes. However, new research suggests that genes may be triggered by both environmental and behavioral influences. This probabilistic epigenesis view of development, suggests that instead of following a predetermined path to expression, genes are modified by the behavior and environment of an organism. Furthermore, these modifications can then act on the environment, creating a causal circle in which genes influencing the environment are re-influenced by these changes in the environment.
Cells do not develop in isolation. Even from a young age, neurons are influenced by the surrounding environment (e.g., other neurons). Over time, neurons interact either spontaneously or in response to some sensory stimulation to form neural networks. Competition between neurons plays a key role in establishing the exact pattern of connections. As a result, specific neural activation patterns may arise due to the underlying morphology and connection patterns within the specified neural structures. These may subsequently be modified by morphological change imposed by the current representations. Progressively more complex patterns may arise through manipulation of current neuronal structures by an organism's experience.
While neurons are embedded within networks, these networks are further embedded within the brain as a whole. Neural networks do not work in isolation, such as in the modularity of mind perspective. Instead, different regions interact through feedback processes and top-down interactions, constraining and specifying the development of each region. For example, the primary visual cortex in blind individuals has been shown to process tactile information. The function of cortical areas emerges as a result of this sensory input and competition for cortical space. "This interactive specialization view implies that cortical regions might initially be non-specific in their responses but gradually narrow their responses as their functional specialization restricts them to a narrower set of circumstances."
The brain is further limited by its constraint within the body. The brain receives input from receptors on the body (e.g., somatosensory system, visual system, auditory system, etc.). These receptors provide the brain with a source of information. As a result, they manipulate the brain's neural activation patterns, and thus its structure, leading to constraining effects on the construction of representations in the mind. The sensory systems limit the possible information the brain can receive and therefore act as a filter. However, the brain may also interact with the environment through manipulation of the body (e.g., movement, changes in attention, etc.), thus manipulating the environment and the subsequent information received. Pro-activity while exploring the environment leads to altered experiences and consequently altered cognitive development.
While a person may manipulate the environment, the specific environment in which the person develops has highly constraining effects on the possible neural representations exhibited through a restriction of the possible physical and social experiences. For example, if a child is raised without a mother, the child cannot change his/her responses or actions to generate a mother. S/he may only work within the specified constraints of the environment in which s/he is born.
The nature of representations
All of the above constraints interact to form cognitive representations in the brain. The main principle is context dependence, as shaping occurs through competition and cooperation. Competition leads to the specialization of developing components which then forms new representations. Cooperation, on the other hand, leads to combinations of existing mental representations that allow existing knowledge to be reused. Construction of representations also depends on the exploration of the environment performed by the individual. However, the experiences derived from this pro-activity constrain the range of possible adaptations within the mental representations. Such progressive specialization arises from the constraints of the past and current learning environment. To alter representations, the environment demands improvements through small additions to the current mental state. This leads to partial representations instead of the fixed, static representations that are assumed to occur in adults. Neuroconstructivism argues such end products do not exist. The brain's plasticity leads to ever-changing mental representations through individual pro-activity and environmental interactions. Such a viewpoint would then imply that any current mental representations are the optimal outcome for a specified environment. For example, in developmental disorders like autism, atypical development arises because of adaptations to multiple interacting constraints, the same as normal development. However, the constraints differ and thus result in a different end-product. This view directly contrasts previous theories which assumed that disorders arise from isolated failures of particular functional modules.
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