Developmental Brain Ontogeny

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Developmental Brain Ontogeny

• Developmental Neuropsychology

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Gyri Formation

• Originally thought to reflect a passive process
• Mechanical folding
• Early brain is smooth or lessencephalic
• Neurons migrate from the germinal matrix
• Dorsolateral side of lateral ventrilces

3
Gyri Formation

• Gyral patterns can be modified experimentally
• Lesions yield abnormal patterns
• Microgyria and cytoarchitectonic abnormalities
  results from brain injury

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Fetal Brain Development

• Neural tube first recognizable structure
• Occurs about 6-8 weeks gestation
• Begins to differentiate
• Bulb at anterior end

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Fetal Brain Development

• Neural tube is the first recognizable structure
• Bulb develops lateral fissure
• Sylvian fissure develops - downward ascending

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Fetal Brain Development

• Approximately recognizable brain at 3-4 months
  gestation
• No cortical processes at this point
• At 7-8 months gestation 6 layers of the cortex
  appear

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Brain Development

• Head size increases
• Density of cells decreases, size increases
• Myelination occurs for life
• Cortex develops from the bottom up

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Brain Development

• Fissures
• Parietal, occipital, temporal in the first two
  years
• Frontal spurt ages 2 to 6

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Brain Development

• Electrophysiology
• 1st year delta predominates
• (1.5 to 3.5 HZ)
• 6 alpha increases
• (7.5 to 12.5 HZ)

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Fetal Brain Development

• Neurons seem to know their final location and
  migrate
• Myelination development of white fatty sheath,
  covers most neurons continues well into life

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Developmental Brain Development
Newborn 6 months 2 years Adult
Density (x103/mm3) 99 30.5 20.1 12.5
Cell Volume (um3) 240 610 990 1040
Dendritic branches 3.1 15.6 16.7 40.8
Dendritic length (um) 203 2367 3259 6836