Brain Plascity Part 1 Video 1

Brain Plasticity and Neurodevelopment

Introduction to Section Two

  • Focus areas:
    • Brain plasticity
    • Sensation and perception
  • Structure of lectures:
    • Two lectures dedicated to brain plasticity

Understanding Neurodevelopment

  • Overview of neurodevelopment and brain changes
  • Key questions regarding brain assembly:
    • How to assemble a brain with neurons?
    • Critical information needed for correct assembly.

Analogy: Assembling a Brain

  • Lego Car Assembly:
    • Collecting all pieces and organizing them
    • Referring to an instruction manual for guidance
  • Comparison with Brain Assembly:
    • Requires exact pieces (neurons) and capabilities for connections
    • No explicit instruction book is provided for assembly

Development of the Human Central Nervous System

  • Timeline of development:
    • Begins at approximately two weeks gestational age
    • Formation: folding lips surrounding a fluid-filled cavity
    • Central Canal of spinal cord and four ventricles of brain development
  • Visual representation:
    • Three weeks: Early brain structure development
    • Seven and a half weeks:
    • Brainstem formation
    • Simple muscle movements start due to spontaneous spinal cord activity

Growth and Weight Changes

  • Average human brain weight:
    • At birth: 350 grams
    • By end of first year: 1,000 grams
    • Typical adult brain: 1,200-1,400 grams
  • Comparison with assembly approach:
    • The nervous system doesn't follow a precise assembly manual

Key Questions in Neurodevelopment

  1. How many neurons are needed?
  2. How do neurons establish connections with each other?

Mechanisms for Neuron Counting and Survival

  • Data visualization: Number of motor neurons in human fetus across developmental stages (10, 20, and 30 weeks gestation):
    • Initial growth phase with neuron production followed by a decrease over time
  • Counterintuitive observation:
    • Decrease in motor neurons as development progresses
Apoptosis Mechanism
  • Definition: Apoptosis refers to the programmed cell death in neurons
    • Each neuron has a built-in suicide program unless it connects with other neurons
  • Example: Motor neurons receive Nerve Growth Factor (NGF)
    • NGF promotes survival and growth of axons in motor neurons
  • Without sufficient connections:
    • Neurons do not receive enough NGF
    • Neurons undergo apoptosis (die)

Competition for Nerve Growth Factor

  • Video explanation:
    • Three neurons compete for NGF
    • Successful neurons connect and survive, while unsuccessful neuron dies

Implications of Neurodevelopment

Fetal Alcohol Syndrome (FAS)
  • Definition: A condition in children due to heavy alcohol consumption during pregnancy
  • Observed characteristics:
    • Facial abnormalities
    • Hyperactivity
    • Impulsiveness
    • Difficulty in maintaining attention
    • Varying degrees of mental retardation
    • Motor problems and heart defects
  • Effects of alcohol on the developing brain:
    1. Interferes with new neuron production
    2. Affects neuron migration and differentiation
    3. Impairs synaptic transmission
    • Inhibits glutamate (excitatory neurotransmitter) receptors
    • Enhances GABA (inhibitory neurotransmitter) receptor activity

Mechanisms of Alcohol Impact

  • Changes in neuronal activity:
    • Results in decreased epsp (excitatory postsynaptic potential) and increased ipsp (inhibitory postsynaptic potential)
    • Neurons are less likely to fire and communicate effectively
  • Adaptation Mechanism:
    • Neurons build additional glutamate receptors to compensate
  • Consequences:
    • Overstimulation upon return of normal neurotransmitter function
    • Excess influx of sodium and calcium leads to potential neuron death
Conclusion on Neuronal Production
  • Observations of decreasing motor neurons suggest
    • The brain overproduces neurons early in development
    • Neurons establish connections to become functional parts of the neural network while unnecessary neurons undergo apoptosis