Theories of Human Functional Brain Development

Session Objectives

  • By the end of today’s session:

    • Understand the main 3 theories of functional brain development:

    • Maturational

    • Skill learning

    • Interactive specialisation

    • Identify theoretical frameworks guiding research questions and methods in human neurodevelopmental studies.

    • Interpret research findings as consistent or inconsistent with these theoretical frameworks.

Importance of Theories

  • Discusses the foundational role of theories in understanding human brain development.

Overview of Brain Development

  • Knowledge concerning brain development is divided into:

    • Prenatal Development

    • Postnatal Development:

    • Established subcortical structural development.

    • Key processes include:

      • Neurogenesis in the hippocampus.

      • Synaptogenesis. Refers to the rapid formation of synapses between neurons after birth. Occurs at an extremely high rate in infancy and early childhood.

      • Synaptic pruning. The selective elimination of weaker or unused synapses.

      • Ongoing myelination. Myelination involves the formation of a fatty myelin sheath around axons by oligodendrocytes.

    • Notable differences in metabolism and glucose usage. As pruning progresses, metabolic demand becomes more efficient and regionally specialized.

      • The role of “helplessness” in human infant development.

    • Ongoing cortical development. The cerebral cortex matures slowly, continuing into the mid-to-late 20s.

Structural vs. Functional Development

  • Locationist point of view:

    • Asserts that certain structures or areas of the brain are associated with specific functions.

  • Debate on whether functional and structural specialisation present in adulthood is innately determined or shaped by:

    • Environmental engagement.

    • Regular structured interaction leading to brain adaptation in support of skills.

Definition of Theories of Functional Brain Development

  • Represents a framework that captures:

    • The relationship between physical brain development and behavioral/cognitive capabilities' emergence.

  • Main interest:

    • Mechanisms underlying developmental changes.

    • Investigate the developmental trajectory of particular systems and origins of cortical specialisation in specific functions.

  • Focuses primarily on cortical functions but applies to understanding and intervening in atypical development.

Overview of the Three Theories

  1. Maturational Theory

    • Claims the existence of pre-determined structures and areas of the brain tailored for specific functions.

    • Emergence of functions relies on the maturation of these structures.

    • Causality:

      • Unidirectional; functional development is solely attributed to brain maturation.

    • Mapping:

      • Static mapping reflects a ‘mosaic’ where functions are localized in specific areas that develop fully before functionality is observable.

    • Development is characterized as sudden and non-linear.

  2. Skill Learning Theory

    • Associates nervous maturation and task performance.

    • Advocates that to learn specific skills, key brain areas are activated and involved.

    • Causality:

      • Unidirectional, with the environment driving functional development.

    • Mapping:

      • Dynamic mapping where functions are assigned to different brain areas correlating to development and skill proficiency until reaching specialization.

  3. Interactive Specialisation Theory

    • Functional specialization arises from inter-regional interactions.

    • Brain responses are determined by connectivity patterns with other regions.

    • The environment plays a crucial role in determining specialization needs.

    • Causality:

      • Bidirectional, where maturation impacts skill development while the environment shapes functions influencing brain maturation.

    • Mapping:

      • Dynamic mapping reflects a circular interaction where functional mappings shift from widespread to specific, which may differ from adult patterns despite similar behaviors (e.g., vocabulary development).

Limitations of Developmental Theories

  • Limitations of Maturation Theory:

    • Biological Determinism: It often ignores the degree to which the environment can influence or even trigger the maturation of biological structures.

    • Inflexibility: This model does not account for neuroplasticity or the brain's ability to repurpose areas if the primary maturational path is disrupted.

    • Passive Learning: It characterizes the infant as a passive recipient of genetic programming rather than an active explorer.

  • Limitations of Skill Learning Theory:

    • Neglect of Biological Blueprints: It may underestimate the role of innate architectural constraints that make humans predisposed to certain types of learning (e.g., language).

    • Sensitive Periods: It struggles to explain "critical periods" where learning must occur within a specific window (tt) to be fully effective, regardless of environmental richness later in life.

  • Limitations of Interactive Specialization:

    • Empirical Difficulty: Because it involves complex, bidirectional feedback loops (Brain↔EnvironmentBrain↔Environment), it is very difficult to test and isolate variables in a lab setting.

    • Computational/Imaging Requirements: To prove these theories, high-resolution longitudinal neuroimaging is required, which is costly and logistically challenging for large cohorts.

Implicit Theories in Research

  • Examination of implicit theories exemplified through face processing across development, demonstrating support for each foundational theory.

  • Engage in a Mentimeter activity for class participation.

Discussion Questions on Skill Development

  • Investigation into why specific skills may not be observable at early developmental stages:

    1. How does each theory (Maturational, Skill Learning, Interactive Specialisation) address this?

    2. What methodological decisions would be made to measure early brain process development?

    3. How would physical impairments in specific brain areas affect skill development?

    4. Plasticity Definition:

    • What is plasticity in the context of brain development?

Methodological Note in Developmental Neuroscience

  • Reference: Elsevier, Developmental Cognitive Neuroscience 1 (2011) 101-109

  • Key guidelines for neuroimaging research based on developmental theory include:

    1. Age group selection should be theory-driven.

    2. Brain-behaviour correlations must be computed, acknowledging effect size variations.

    3. Longitudinal designs are necessary to examine maturation and change.

    4. Training and intervention studies illustrate cognitive functions' malleability and neural mechanisms.

    5. Interpreting compensatory brain activation should be approached with caution.

    6. Differences in strategy can lead to varied differential brain activation.

Summary and Implications

  • Discussion of the three distinct theories:

    • Variations in definitions, causality, and mapping assumptions.

    • Implicit influences in developmental studies affecting rationale, methodology, and interpretation.

    • Identification of overlaps among theories and significance in atypical development findings.