Overview
This lecture explores how the human brain develops from conception through infancy, highlighting the roles of genetics, environment, and early experiences in shaping brain structure and function.
The Complexity of the Brain
- The human brain is the most complex organ, even a baby's brain contains billions of neurons and trillions of connections.
- Each neuron can form thousands of connections, creating an intricate neural network.
- Most brain cells (neurons) are formed before birth and rarely replaced, unlike other body cells.
Brain Development Before Birth
- Brain development starts with the formation of the neural tube, which will become the brain and spinal cord.
- By four weeks gestation, neurons are forming rapidly—about 500,000 per minute.
- Neurons migrate to specific brain regions, guided by genetic cues and interactions with neighboring cells.
- Neuronal migration is a precise and vulnerable process essential for brain organization.
Wiring the Brain
- Brain wiring follows a genetic blueprint, initially forming broad connections.
- Proper connections are strengthened through use, while unused connections are pruned—summed up as "use it or lose it."
- This wiring process continues after birth, especially in premature babies.
Premature Birth and Brain Vulnerability
- Babies born prematurely miss crucial weeks of brain development in the womb.
- Exposure to sensory overload in intensive care units can negatively affect later cognitive and emotional functioning.
- Carefully controlled environments and parental contact can improve outcomes for premature babies.
Nature vs. Nurture in Brain Development
- Genetics determine initial brain structure, but environment and sensory experiences modify brain function (plasticity).
- Experiments show that brain areas can adapt to new inputs, but genetic constraints remain.
Sensory Experience and Brain Plasticity
- Newborns are highly sensitive to sensory input; stimulation is essential for proper brain development.
- Visual development depends on timely visual experience; early deprivation (e.g., cataracts) can cause permanent deficits.
- Early intervention can help restore function, but critical periods exist for optimal recovery.
Ongoing Brain Development and Plasticity
- Brain circuits are refined by experience throughout life, not just in infancy.
- Childhood is a period of high brain plasticity and learning.
- Brain development continues into adolescence and adulthood, adapting to new experiences.
Key Terms & Definitions
- Neuron — a nerve cell that transmits electrical and chemical signals in the brain.
- Neural Tube — the embryonic structure that forms the brain and spinal cord.
- Migration — movement of neurons to their destined locations in the brain during development.
- Plasticity — the brain's ability to change and adapt in response to experience.
- Pruning — elimination of unused neural connections to strengthen important ones.
- Critical Period — a developmental window when the brain is especially sensitive to certain experiences.
Action Items / Next Steps
- Review assigned readings on brain development and plasticity.
- Prepare questions for next class on childhood brain changes and language learning.
- If applicable, watch the next episode in the series on child brain development.