As we age, our brain undergoes a number of changes. One of the most notable changes is a decline in overall brain volume and a decrease in the number of neurons. Additionally, there may be a decline in the ability of the brain to repair itself, leading to an increased risk of damage and disease. There may also be a decline in cognitive function, such as memory, attention, and processing speed.
Putting this in a list, it would be listed as follows (NOTE : this is the list consolidated from many different sources and you may see some of the items are almost same but just a little bit different of wording. I didn't try to consolidate the list further to make it short because I think some repetition would not do any harm. On the contrary, a certain degree of repepition would help us to get familiar).
There would be many additional examples of changes with age. I will talk about each of these items in more detail in this note.
NOTE : In the following details, there are description indicating the rate of changes in specific number. But those specific number would come from a limited amount of research result and may not be generalized or the number would show variations among different persons, sex and other factors. So just take it just as a ballpark figures (approximate number).
Changes in Overall Brain Volume
The volume of the brain and/or its weight declines with age at a rate of around 5% per decade after age 401 with the actual rate of decline possibly increasing with age particularly over age 70.
The exaxt mechanism behind this volume reduction is not clearly known. Some of hypothesis are as follows :
NOTE : It is unlikely to have a single reason for the volume reduction. It is more likely that multiple factors works simulteneously or those factors may varies with person and sex.
As we age, there are changes in the density of the brain's cortex, which is the outer layer of the brain that is responsible for many of our cognitive functions such as perception, attention, and memory.
One of the most well-known changes in cortical density with aging is a decrease in gray matter volume. Gray matter is composed mainly of nerve cells and their connections, and its volume decreases with age in many brain regions, particularly in the prefrontal cortex, temporal lobes, and parietal lobes. This decrease in gray matter volume is thought to be due to a loss of nerve cells and synapses (connections between nerve cells) as well as changes in the support cells called glia.
A study that used magnetic resonance imaging (MRI) found that the cortical thickness of the brain decreases by about 0.5% to 1% per year after the age of 40. Another study using MRI found that the cortical thickness decreases by about 0.02 mm per year between the ages of 20 to 80.
White matter typically deteriorates with age. This can lead to a decline in cognitive function, including problems with memory, attention, and decision making. The most common age-related changes in white matter include the loss of myelin.
White matter is composed mainly of the long fibers (myelinated nerve fibers) that connect different brain regions, and its volume increases with age. The increase in white matter volume is thought to be due to the accumulation of myelin, a fatty substance that surrounds the fibers and helps to speed up the transmission of signals. It is believed that slowing down processing and reducing cognitive function is related to the myelin shrinks.
It is believed that the myelin sheath start deteriorating after around the age of 40 even in normal ageing and deteriorate more significantly in the 60s and beyond.
Some study using MRI scans, found that the white matter volume in the brain decreases by about 0.2% per year for adults between the ages of 30 to 90. Another study, using Diffusion Tensor Imaging (DTI) found that the fractional anisotropy (FA) of white matter decreases by about 0.1% per year for adults between the ages of 20 to 80.
With ageing, the brain begins to produce different levels of chemicals that affect neurotransmitters and protein production, ultimately leading to a decline in cognitive function.
One of the most well-known changes in neurotransmitters with aging is a decline in the level of acetylcholine. Acetylcholine is a neurotransmitter that is involved in memory, attention, and learning. A decline in acetylcholine levels is thought to contribute to age-related memory decline and the development of Alzheimer's disease.
Another change in neurotransmitters with aging is a decline in the level of dopamine. Dopamine is a neurotransmitter that is involved in motivation, reward, and movement control. A decline in dopamine levels is thought to contribute to age-related changes in motor function, such as Parkinson's disease, and mood disorders, such as depression.
There are also changes in the balance of other neurotransmitters such as norepinephrine, serotonin and GABA, which can also have impact on cognitive function and mood regulation.
Which part of the brain shrinks the most ?
Brain changes do not occur to the same extent in all brain regions.
The frontal lobe and hippocampus shrink more than other areas while brain volume decreases overall with age and we would see some degree of shrink in temporal lobes.
The area of major brain changes seems to vary in men and women. frontal and temporal lobes most affected in men compared with the hippocampus and parietal lobes in women
The rate of reduction in brain volume may increase with age particularly over 70
You may correlate these shrink of the parts of the brain with common behavioral changes that are commonly observed among elderly persons.
Behavioral changes associated with the shrinkgage in Hippocampus
Behavioral changes associated with the shrinkgage in Prefrontal Cortex
Behavioral changes associated with the shrinkgage in Temporal Lobe
NOTE : you may notice that the some of the difficulties listed here are similar (or same) as the one listed as in the case of hippocampus shrinkage. It is because Hippocampus itself is embedded deep inside of temporal lobe. That is, temporal lobe shrinkage may lead to Hippocampus functionality changes as well.
Here I want to list some of the personal experiences about myself which seems to be related to againg brain.