PSYCH201: Wed 05/03 W2;L5

Introduction to Brain Development and Plasticity

  • Topic covered: Development and Plasticity of the Brain
  • References: Kallat's book modules 4.2 and 4.3
  • Editions: Both 13th and 14th editions are acceptable for reference

Overview of Brain Development

  • Objective: Describe early brain development in broad strokes.
  • Neurons: Unique characteristic - can be very long (e.g., axon from toe to spinal cord).

Neuron Mechanics

  • Neurons are post-mitotic (cannot multiply after formed), necessitating repair mechanisms.
  • Neuronal death is irreversible; needs alternative strategies for recovery post-injury (e.g., stroke).

Historical Insights in Neuroscience

  • Roger Sperry:
    • Studied differences between left and right brain functions.
    • Nobel Prize for his work with severed corpus callosum in epilepsy patients, leading to insights on brain lateralization.
  • Rita Livo Montalcini:
    • Discovered nerve growth factor (NGF) critical for synaptic connections.
    • Overcame significant barriers to her research during WWII.

Embryonic Development of the Brain

  • Brain development starts shortly after conception (about 2 weeks).
  • Formation of Neural Tube:
    • Edges of embryo fold to create a tube that later becomes the central nervous system.
  • Homeobox Genes:
    • Determine the body structure's spatial organization across species.

Stages of Brain Differentiation

  • 3 Main Regions:
    • Hindbrain
    • Midbrain
    • Forebrain
  • At birth, the brain weighs ~300 grams; growth reaches ~1200-1400 grams in adulthood.

Key Developmental Processes

  1. Neurogenesis: Formation of new neurons, completed by birth.
  2. Glial Cell Development: Supporting cells that aid neuron function, develop post-birth.
  3. Synaptogenesis: Formation of synapses occurs predominantly after birth.
  4. Myelination: Formation of myelin sheaths around axons; completes around 25 years of age.
  5. Synaptic Pruning: Unused synapses removed to optimize brain efficiency.

Impact of Environmental Factors

  • Prenatal stressors can affect brain development, influencing behavior and psychological outcomes (e.g., maternal infections linked to higher rates of depression and Autism Spectrum Disorder).

Mechanisms for Neuronal Targeting

  • Neurons determine their pathways guided by chemical signals and trails during early development.
  • Roger Sperry's research showed that the origin of the cell (in the eye) determines axon destinations, further explored in salamander experiments.

Brain Adaptations Post-Injury

  • Responses include increased activity in surrounding areas of the brain, collateral sprouting, and increased receptor sensitivity in remaining neurons to compensate for lost function.

Case Studies and Findings

  • Studies on blind individuals demonstrated occipital cortex activation during tactile tasks, showing functional plasticity in brain regions originally dedicated to vision.
  • Research on phantom limbs revealed that adjacent brain areas can take over the function of lost limbs, leading to sensory misperceptions.

Neuroplasticity in Adulthood

  • Neurons are mostly fixed; adaptations arise via modifications in existing synapses rather than through the creation of new neurons.
  • Neuroplastic changes occur due to learning, memory formation, and environmental influences.

Conclusion

  • Brain development is a complex interplay between genetic instructions and environmental interactions, with profound implications for understanding behavior and neurological health.