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Brain volume peaks at the teenage years, [34] and after the age of 40 it begins declining at 5% per decade, speeding up around 70. [35] Average adult male brain weight is 1,345 grams (47.4 oz), while an adult female has an average brain weight of 1,222 grams (43.1 oz). [36]
The total volume of the hippocampus is also ... to Alzheimer's disease in elderly adults > 80 years of age. [3]: 1503 Hippocampal sclerosis occurs in other ...
Sedentary adults over age 55 show a 1–2% decline in hippocampal volume annually. [37] A neuroimaging study with a sample of 120 adults revealed that participating in regular aerobic exercise increased the volume of the left hippocampus by 2.12% and the right hippocampus by 1.97% over a one-year period. [37]
In a significant proportion of persons with LATE-NC, there is atrophy, cell loss and astrogliosis in the hippocampus, diagnosable at autopsy (and somewhat less specifically via MRI during life) as hippocampal sclerosis. [3] Brains with LATE-NC and hippocampal sclerosis are relatively more affected clinically than those with LATE-NC alone. [4]
In adult humans the volume of the hippocampus on each side of the brain is about 3.0 to 3.5 cm 3 as compared to 320 to 420 cm 3 for the volume of the neocortex. [ 181 ]
Individuals who develop hippocampal lesions often fare poorly on measures of verbal declarative memory. Tests involving the recall of paragraphs or strings of words, as cited by Bremner and colleagues, illustrate a degree of dysfunction among lesion patients proportionate to the percentage of hippocampal volume and the amount of cells lost. [7]
Exercising has frequently increased the reproduction of neuronal precursor cells and helped with age-related declines in neurogenesis. The brain volume decreases roughly 5% per decade after forty. It is currently unclear why brain volume decreases with age.
This results in smaller hippocampal volumes, potentially explaining the association between early life stress and reduced hippocampal volume. [63] This volume reduction may be associated with the emotion regulation deficits seen in those exposed to early life stress. The amygdala is particularly vulnerable to early life stress. [58]