Dual-process model of white-matter development

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This reference is used to support claims made by Dr Piotr Wozniak as part of an article series on memory, learning, creativity, and problem solving.

Measurements of the developmental trajectory of gray and white matter in the brain are helpful in understanding the conceptualization process that determines the brain architecture as well as phenomena such as critical periods, precocity paradox, creativity, intelligence, harms of coercion in learning, harms of early instruction, importance of the Fundamental Law of Learning, etc.

The dual-process model of white matter development explains the dynamics of changes in properties of white matter in the brain. It juxtaposes two related phenomena that determine the ultimate density and topology of white matter: (1) axonal pruning and (2) axonal myelination.

In the conceptualization process, disparate areas of the brain are connected by long-distance pathways populated with long axonal connections. Those connections are rich at birth and facilitate further growth and sprouting along well-established white matter tracts.

In childhood, fast thinking is slow to develop and is determined by pruning of the unused and interfering axons. It is also facilitated by axonal myelination that stabilizes the most efficient pathways. The coordination and synchrony of individual sub-processes in this dynamic architectural process will determine the ultimate outcome: an intelligent brain. In subsequent research Yeatman et al. noticed that "some anatomical [white matter] properties stably predict the ease with which a child learns to read, while others dynamically reflect the effects of experience". Widespread changes can be observed in white matter substrate as fast as in two months of intense practice.

The importance of the pleasure of learning is to let the entire process be controlled by the learn drive to maximize the efficient use of neural resources to optimize the large scale connectivity. Instead, in the process of schooling, and primarily, early instruction, we do the opposite of what is needed. We coerce children into learning artificial behaviors that may have long-term negative consequences in development. By looking for early acceleration, and by using wrong developmental yardsticks, we risk affecting the architecture of young brains, and undermine future prospects for maximizing intelligence.

Yeatman, Dougherty, Wandell, and Ben-Shachar developed a model of dual-process model of white matter development using differentiation of developmental trajectories in reading proficiency in children, which they correlated with fractional anisotropy (FA) of a selected subset of tracts involved in reading.

Using computer simulations, the team presented a set of fiber density development curves based on their model. The model involves a dual-process system with one process (myelination) that increases the density, and a second process (pruning) that decreases the density. The resultant of the two can produce the variation in developmental trajectories as observed in data.

The balance between the two processes can be modeled by simple homeostatic equations that govern development over time; the parameters of the developmental processes were chosen to model the characteristics of the above-average readers (black curve) and below-average readers (gray curve). The model for the above-average group has synchronous development of the processes, whereas the below-average group is modeled with slightly asynchronous development. For both groups the FA developmental rate is approximately linear during the age range of 7–15 y (shaded region), but the specific rate of development differs (colored lines) […] The slope is negative when myelination and pruning are asynchronous, with myelination dominating during early development and pruning dominating during later development

Quoted excerpts come from the following reference:

Title: Development of white matter and reading skills

Authors: Jason D. Yeatman, Robert F. Dougherty, Michal Ben-Shachar, and Brian A. Wandell

Date: 2012

Backlink: Precocity paradox

Link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3497768/