The human brain goes through several large-scale changes as the individual progresses from embryo through to old age.

Contents 1 Pre-natal development 2 Adolescence 3 Aging 4 See also 5 External links

[edit] Pre-natal development

Developmental neurobiology concerns itself with the development of the brain. The process of neurogenesis populates the brain, then programmed cell death cuts the growing brain down to size.

[edit] Adolescence

During adolescence the brain goes through a process of synaptic pruning.

[edit] Aging

Brain aging (American English) is the major risk factor for most common neurodegenerative diseases, including Alzheimer's Disease, Cerebrovascular Disease, Parkinson's Disease and Amyotrophic Lateralising Sclerosis. Other risk factors, including genetic mutations, low educational attainments and head injury contribute much less to the risk of these disorders. The molecular biology of brain aging is poorly understood and this is of importance when seeking to understand the pathogenesis of Alzheimer's Disease (Yankner, Lu & Loerch, 2008).

There are few informative studies on the molecular biology of brain aging in the absence of neurodegenerative disease. In large part this deficit is attributable to the paradox that many individuals without clinical disease before death are found at autopsy to have extensive evidence of brain neurodegeneration and, conversely, some die with clinical features of disease but show few signs at autopsy of degeneration. The hypothetical concept of cognitive or brain reserve was devised to explain these types of discrepancy between clinical features and brain pathology (Stern, 2002).

The human brain shows a decline in function and a change in gene expression. This modulation in gene expression may be due to oxidative DNA damage at promoter regions in the genome. Genes that are down-regulated over the age of 40 include:

• GluR1 AMPA receptor subunit
• NMDA R2A receptor subunit (involved in learning)
• Subunits of the GABA-A receptor
• Genes involved in long-term potentiation e.g. calmodulin 1 and CAM kinase II alpha.
• Calcium signalling genes
• Synaptic plasticity genes
• Synaptic vesicle release & recycling genes

Genes that are upregulated include:

• Genes associated with stress response and DNA repair
• Antioxidant defence

Normal aging is distinct from Neurodegenerative disease. DNA damage due to oxidation increase as the brain ages, possibly due to impaired mitochondrial function.

Neuroinflamation is a common feature of aging in the mammalian brain. Astrogliosis (measured by immunohistochemistry of GFAP) increases with age in mouse, rat as well as human brain.

[edit] See also

• Aging
• DNA damage theory of aging
• Life extension
• List of life extension related topics
• Memory and aging
• Senescence
• Reliability theory of aging and longevity

[edit] External links

• Brain puzzles from Infoaging.org
• Researchers Gain New Insights into the Aging Brain
• Study suggests aging brain shifts gears to emotional advantage
• Brain exercise software(commercial)

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