What Happens To The Brain As We Age?
Brain aging is inevitable to some extent, but not uniform; it affects everyone, or every brain, differently. Slowing down brain aging or stopping it altogether would be the ultimate elixir to achieve eternal youth. Is brain aging a slippery slope that we need to accept? Or are there steps we can take to reduce the rate of decline? At around 3 pounds in weight, the human brain is a staggering feat of engineering with around 100 billion neurons interconnected via trillions of synapses.
Throughout our lifetime our brain changes more than any other part of our body. From the moment the brain begins to develop in the third week of gestation to old age, its complex structures and functions are changing, networks and pathways connecting and severing. During the first few years of life, a child’s brain forms more than one million new neural connections every second. The size of the brain increases fourfold in the preschool period and by age 6 reaches around 90% of adult volume. The frontal lobes – the area of the brain responsible for executive functions, such as planning, working memory, and impulse control – are among the last areas of the brain to mature, and they may not be fully developed until 35 years old.
As we age, all our body systems gradually decline – including the brain. “Slips of the mind” are associated with getting older. People often experienced those same slight memory lapses in their 20s and yet did not give it a second thought. Older individuals often become anxious about memory slips due to the link between impaired memory and Alzheimer’s disease. However, Alzheimer’s and other dementias are not a part of the normal aging process. Common memory changes that are associated with normal aging include:
- Difficulty learning something new: Committing new information to memory can take longer.
- Multitasking: Slowed processing can make processing and planning parallel tasks more difficult.
- Recalling names and numbers: Strategic memory that helps memory of names and numbers begins to decline at age 20.
- Remembering appointments: Without cues to recall the information, appointments can be put safely in storage and then not accessed unless the memory is jogged.
While some studies show that one third of older people struggle with declarative memory (memories of facts or events that have been stored and can be retrieved), other studies indicate that one fifth of 70-year-olds perform cognitive tests just as well as their 20-year-old counterparts. Scientists are currently piecing together sections of the giant puzzle of brain research to determine how the brain subtly alters over time to cause these changes.
General changes that are thought to occur during brain aging include:
- Brain mass: Shrinkage in the frontal lobe and hippocampus – areas involved in higher cognitive function and encoding new memories – starting around the age of 60 or 70 years.
- Cortical density: Thinning of the outer-ridged surface of the brain due to declining synaptic connections. Fewer connections may contribute to slower cognitive processing.
- White matter: White matter consists of myelinated nerve fibres that are bundled into tracts and carry nerve signals between brains cells. Myelin is thought to shrink with age, and as a result, slow processing and reduce cognitive function.
- Neurotransmitter systems: Researchers suggest that the brain generates less chemical messengers with aging, and it is this decrease in dopamine, acetylcholine, serotonin, and norepinephrine activity that may play a role in declining cognition and memory and increased depression.
In understanding the neural basis of cognitive decline, researchers can uncover which therapies or strategies may help slow or prevent brain deterioration.
Credit: Hannah Nichols for Medical News Today 29 August 2017.