Brain mass: While brain volume decreases overall with age, the frontal lobe and hippocampus - specific areas of the brain responsible for cognitive functions - shrink more than other areas. The frontal lobes are located directly behind the forehead. They are the largest lobes in the human brain and are considered to be the human behavior and emotional control centers for our personalities.The hippocampus is a complex brain structure embedded deep into the temporal lobe. It plays a major role in learning and memory. Studies have shown that the hippocampus is susceptible to a variety of neurological and psychiatric disorders.
Cortical density: This refers to the thinning of the outer corrugated surface of the brain due to decreasing synaptic connections. Our cerebral cortex, the wrinkled outer layer of the brain that contains neuronal cell bodies, also thins with age. Cortical thinning follows a pattern similar to volume loss and is particularly pronounced in the frontal lobes and parts of the temporal lobe. Lower density leads to fewer connections, which could contribute to slower cognitive processing.
the ageing brain ||
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Neurotransmitter systems: The brain begins to produce different levels of chemicals that affect neurotransmitters and protein production, ultimately leading to a decline in cognitive function.
As the brain ages, neurons also begin to die, and the cells also produce a compound called amyloid-beta. Amyloid beta is what is typically associated with Alzheimer's. It can also be found in the brain of an individual who is aging. If there are amyloid-beta plaques (prions) in the brain, it can be a sign of Alzheimer's disease. And when there are signs of plaque, but no prions, it may be a sign of normal aging.
Researchers are working to understand normal brain aging, why some people stay cognitively healthy longer than others, and what might protect your brain as you age. Visit the Alzheimers.gov Clinical Trials Finder to learn about clinical trials and studies near you and consider joining a study to be a partner in discovery.
Aging may also bring positive cognitive changes. For example, many studies have shown that older adults have more extensive vocabularies and greater knowledge of the depth of meaning of words than younger adults. Older adults may also have learned from a lifetime of accumulated knowledge and experiences. Whether and how older adults apply this accumulated knowledge, and how the brain changes as a result, is an area of active exploration by researchers.
There have been studies investigating different types of memory in ageing using neuropsychological testing and neuroimaging. However, it must be pointed out that it is sometimes methodologically difficult to separate some of these functions, for example episodic memory encoding and semantic memory retrieval.24 Despite this studies are beginning to examine performance on memory tasks with ageing and by neuroimaging. A review article focusing in this area highlighted the changes in regional brain activation.24 Older brains tend to show more symmetrical activation, either because they have increased activation in a hemisphere that is less activated than in younger adults or because they show reduced activation in the areas most activated in younger adults. This has been shown for visual perception and in memory tasks.24 The observed changes in activation in the left and right prefrontal cortex are in keeping with changes in memory performance, particularly episodic memory, as this is thought to be based in this area.24 It has also been suggested that the actual level of brain activation, as shown in neuroimaging, may be related more directly to the levels of memory performance.25 A review of studies using electroencephalograms to examine event related potentials in response to stimuli also contribute some support for increased symmetry in brain activation with age.26
Another factor to consider with regard to the ageing brain and its cognitive performance is hormonal influence. It is known that sex hormones can affect cognitive processes in adulthood and that changes in sex hormones occur in ageing particularly in women at menopause. Women also have a higher incidence of AD even when longer life expectancy is taken into account.14 AD is characterised by failing memory and there has been a suggestion that oestrogen therapy may increase dopaminergic responsivity32 and play a protective part in AD.33,34 It must be remembered though that the use of HRT has recently been shown to have cancer risks.35 Growth hormone levels also decline with age and may be associated with cognitive performance although the evidence is far from clear.36
Increasing evidence points to vascular factors not only contributing to cognitive problems in ageing but also to the two most common dementias seen in this population. The prevalence of dementia increases almost exponentially with increasing age with around 20% of those aged 80 affected rising to 40% of those aged 90.39
The issue of normal ageing is a difficult one because there are studies that show cognitively intact adults aged 100,72,73 and yet a high percentage suffer from dementia and the line between mild cognitive impairment and normal memory changes74 is still a little blurred.75,76 What is in no doubt is that changes in brain vasculature, WML and intra/extra cellular changes are likely to begin in midlife.71 There are many influences on the ageing brain, genetics, biological, and environmental influences all of which contribute to the physiological and cognitive changes77,78; Mattson79 provided a review.
The mechanisms involved in plasticity in the nervous system are thought to support cognition, and some of these processes are affected during normal ageing. Notably, cognitive functions that rely on the medial temporal lobe and prefrontal cortex, such as learning, memory and executive function, show considerable age-related decline. It is therefore not surprising that several neural mechanisms in these brain areas also seem to be particularly vulnerable during the ageing process. In this review, we discuss major advances in our understanding of age-related changes in the medial temporal lobe and prefrontal cortex and how these changes in functional plasticity contribute to behavioural impairments in the absence of significant pathology.
Background: Anaesthetic drugs act at sites within the brain that undergo profound changes during typical ageing. We postulated that anaesthesia-induced brain dynamics observed in the EEG change with age.
Conclusions: These profound age-related changes in the EEG are consistent with known neurobiological and neuroanatomical changes that occur during typical ageing. Commercial EEG-based depth-of-anaesthesia indices do not account for age and are therefore likely to be inaccurate in elderly patients. In contrast, monitoring the unprocessed EEG and its spectrogram can account for age and individual patient characteristics.
If you forget a name or two, take longer to finish the crossword, or find it hard to manage two tasks at once, you're not on the road to dementia. What you're experiencing is your brain changing the way it works as you get older. And in many ways it's actually working better. Studies have shown that older people have better judgment, are better at making rational decisions, and are better able to screen out negativity than their juniors are.
How is it possible for older people to function better even as their brains slow? "The brain begins to compensate by using more of itself," explains Dr. Bruce Yankner, professor of genetics and co-director of the Paul F. Glenn Laboratories for the Biological Mechanisms of Aging at Harvard Medical School. He notes that MRIs taken of a teenager working through a problem show a lot of activity on one side of the prefrontal cortex, the region we use for conscious reasoning. In middle age, the other side of the brain begins to pitch in a little. In seniors, both sides of the brain share the task equally.
If you've found that it's a little harder to carry on a conversation while searching your bag for your keys, MRI studies offer some clues. They show that in younger people, the area of the brain used to do a task goes dark immediately once the task is completed, while in older people it takes longer to shut down. As a result, it's harder for the older brain to take on several tasks, because not only do you need to use more of the brain for any single task, but the brain also has a harder time letting go of a task. So even after you fish out your keys, you may have trouble getting back into the conversation.
What about the moments when you find yourself driving down the street without any recollection of having passed the last few blocks? Or the times you've locked the car door with your keys in the ignition? On those occasions your brain may have slipped into the default mode, which controls processes like remembering and daydreaming that are not required for a directed task. Imaging studies show that interconnected regions of the brain dubbed the "default network" grow more active with age, indicating that as we age we spend more time daydreaming.
Getting regular exercise is also important. Physical exercise is the best-documented way to preserve brain function. It helps you to lay down new memories and better focus on the tasks ahead of you. Thirty minutes of moderate exercise on most days is all you need.
Accentuating the positive. The amygdala, the area of the brain that consolidates emotion and memory, is less responsive to negatively charged situations in older people than in younger ones, which may explain why studies have shown that people over 60 tend to brood less.
Dr. Yankner and his research team have discovered that a gene that is switched on during fetal development is reactivated in the brains of healthy older people to repair the effects of stress. The gene, called REST, turns off genes that are responsible for Alzheimer's disease. Autopsies of people who died from Alzheimer's have very little of the REST protein, while people the same age who die of other causes have high levels. 2ff7e9595c
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