Aging causes visible changes in our body. Our hair turns gray, our skin wrinkles and loses its elasticity. With aging, more subtle changes occur in our brains. Just like our muscles and joints, our brains can become stiff. There may be a decline in memory and mental skills. There are many changes at the microscopic level, apart from those that are reflected in behavior.
The normal aging process causes slight changes in mental abilities. Memorizing new information and remembering names and numbers can be difficult. Memories of one’s own life and information about general facts constitute declarative memory ; This type of memory regresses with aging. How things are done, such as cycling and tying shoes, concern procedural memory, which is not affected by aging.
Working memory also declines with age. Working memory is briefly activated while memorizing the phone number, license plate or parking lot. Some studies show that working memory begins to weaken as early as the age of 30. Working memory relies on the rapid processing of new information rather than stored information. The ability to predict the speed of objects and problem-solving is also associated with this type of memory and is affected by old age.
As you get older, it can become harder to concentrate and focus. For example, it becomes difficult to understand speech in a noisy environment. Focusing on a particular stimulus by eliminating distracting stimuli is called selective attention. Paying attention to two different tasks, such as talking while driving, is also affected by aging. This is called divided attention.
Not all mental abilities regress after age 30. Some functions may be performed better in middle age. Verbal skills, spatial reasoning, math, and abstract reasoning may be better in middle age than in youth.
We have the chance to learn new things throughout life. Despite the negative effects of aging, our brain remains relatively plastic. In other words, new neural connections can be established in the face of different difficulties and tasks.
Changes in cognitive skills reflect changes in brain structure and chemistry. By middle age, slight but measurable changes occur in the brain. In the 30s and 40s, the total volume of the brain begins to shrink. In the old age, especially around the age of 60, the rate of shrinkage increases.
Volume loss does not occur at the same rate throughout the brain. Some areas shrink faster and more than others. The prefrontal cortex, cerebellum, and hippocampus lose the most volume with aging.
The folded shell (cortex) part of the outer part of the brain gets thinner with age. Cortical thinning is more pronounced in the frontal and temporal lobes.
The areas of the brain that undergo the most significant changes due to aging are the areas that mature late in youth. For this reason, a theory has been put forward that the last maturing is lost first. Studies examining changes in white matter with age support this hypothesis. The first nerve connections to develop in the brain are those that connect the cortex to the lower levels of the brain and the spinal cord. The association fibers connecting the areas in the same hemisphere mature the latest and show the fastest regression with age.
Changes at the neuron level contribute to shrinkage and cortical thinning in the aging brain. Neurons shrink, their dendrites shorten and shrink, the myelin layer surrounding axons deteriorates. The number of synapses between brain cells is reduced, which affects learning and memory.
In old age, although synaptic changes are selective and mild, their effects on cognitive decline may be greater than structural and chemical changes. In the prefrontal cortex and hippocampus, it was observed that the dendrites decreased, their branching and synapse nodes decreased. Studies in monkeys have shown that aging affects fine synaptic nodes more. Thin synaptic nodes form and disappear faster than larger mushroom-like types. Therefore, they may have roles in working memory.
With age, less dopamine is produced in the brain and dopamine receptors decrease. It has been determined that serotonin decreases in individuals aged 60-70 years with mild cognitive impairment.
Finally, new neuron formation, namely neurogenesis, also decreases with age. The olfactory bulb and dentate gyrus are where new neurons are formed throughout adult life. How new neurons integrate into existing neural circuits in the brain is still not fully understood.