SLP528 Neurology
Guide to neurology for clinicians and students in speech-language pathology
Neural Development
Neural development is a time period when the nervous system begins to develop.
There are three main layers of cells that form cell division.
Ectoderm: The outermost layer that forms the skin, brain, nervous system, and external tissues.
Mesoderm: The middle layer that forms the muscle, the skeletal system, and the circulatory system.
Endoderm: The innermost layer that forms internal organs.
When all the layers are formed it’s called a gastrula
During embryonic development, the ectoderm starts to form the neural plate. During this period the groove deepens and begins to form the neural crest. It is around 24 days when the neural crest comes up and fuses and the neural tube is formed creating a little hole in the center. The tube like structure in the center is now the central canal, which begins to form to become the spinal cord. At about one month of age the embryo has started forming the spinal canal.
Stages of neural development
The brain starts to develop around the fourth week and becomes noticeable at the sixth week.
These are the eight fundamental processes of neurodevelopment:
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Neurogenesis: Birth of new neurons
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Cell Migration: Neuron moves to its last location
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Cell Differentiation: Generic embryonic cells become specialized cells
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Apoptosis: Redundant, inactivated neurons die
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Arborization: The increase of dendrites
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Synaptogenesis: Formation of synapses
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Synaptic Sculpting: Survival of activated and used synapses
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Myelination: The remaining functional axons are now covered with myelin so they can function better
*An example of cell migration and cell differentiation would be cells traveling to the occipital lobe. This is where the visual cortices are so these cells would specialize in helping us see.
*Synaptic sculpting and apoptosis create space in the brain and make the brain more efficient! For example, an English speaker doesn’t need the Spanish trill, so cells and synapses that may have worked to learn that skill “die.”
*Myelination is a very important milestone in child development. At around 18 months a child experiences an increase of myelination which is consistent with their vocabulary spurt. This makes sense because myelin not only protects the axon, but it makes information spread faster (Pujol et al., 2006).
Watch this very helpful video that summarizes neural development!