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Neuroimaging

is an umbrella term that refers to a variety of methods and technologies for investigating the brain in both humans and animals.

Two neuroimaging techniques

structural and functional

Structural neuroimaging

This method provides detailed images of the brain’s anatomical structure at a certain point in time. These images look like photographs. This type of imaging helps to identify changes to the structure of the brain that occur after stroke or if, for example, a tumour is present. The most common of thes techniques are X-rays, computerized tomography (CT scans), and magnetic resonance imaging (MRI). T

Functional neuroimaging

provides information about brain activity rather than brain structure. In this method, researchers monitor brain activity as individuals engage in a variety of tasks such as reading or responding to stimuli such as auditory sounds. The areas of the brain that are involved in doing the tasks are illuminated, giving researchers a great view of the parts of the brain involved with each type of task.

functional magnetic resonance imaging (fMRI)

is used most widely to understand the function of the brain during particular tasks.

Neuroimaging techniques have become key to our understanding of

normal age-related changes to the brain, as well as disease processes that can occur with age such as Parkinson’s disease and Alzheimer’s disease.

older adults show activation in both the left and right prefrontal areas when engaged in

a cognitive task

These findings challenge the prevailing idea that

specific brain regions control specific brain functions.

This led to the development of a theory known as HAROLD, which stands for

Hemispheric Asymmetry Reduction in Older Adults (Cabeza et al., 2002; Cabeza et al., 2004). According to this theory, the higher level of bilateral activations in the prefrontal cortex of aging brains demonstrates a compensatory strategy for numerous cognitive tasks.

Bilateralization

in this case, refers to evidence that, in older brains, activations for cognitive tasks spread out to both hemispheres of the prefrontal cortex, whereas in the young, they are typically confined to a single hemisphere.

This is known as compensation

When older adults perform the same task as younger adults, they use different neural circuitry, which, in turn, enhances their performance on these tasks

CRUNCH model

Compensation-Related Utilization of Neural Circuit Hypothesis, also attempts to explain compensatory activity in older adults (Reuter-Lorenz & Cappell, 2008). In this model, the older brain will work harder and broaden its search for available resources to use in a particular cognitive task.

According to the CRUNCH theory

more brain activation occurs in older adults as compared to younger adults on only those tasks that are easier to do. On those tasks that are harder for older adults to do, this compensatory mechanism no longer is effective, which leads to equal or less activation in older adults relative to young adults.

The STAC model

Scaffolding Theory of Aging and Cognition (Park & Reuter-Lorenz, 2009; Reuter-Lorenz & Park, 2014) provides an integrative account of the different theories mentioned so far. These researchers point out that the aging brain is subject to a range of neural challenges to which it must adapt (i.e., atrophy, amyloid deposition, white matter deterioration, etc.), leading to continuous functional reorganization. the model states that both lifespan (aging) and life experience variables affect the development of compensatory scaffolding.

Although there is support for all of these models, none are very good at explaining when or why

compensation breaks down. While there is a growing consensus that the aging brain retains considerable plasticity of function, it is less clear how age differences in brain activity relate to cognitive performance.

Most studies are cross-sectional in nature and longitudinal studies are what is needed to

fully understand the complexities of cognitive aging

Normal aging is associated with

loss of brain volume (shrinkage) and weight,

The frontal cortex (especially the prefrontal cortex), hippocampus, and parietal lobes experience

considerable shrinkage with age

These areas are important to learning, memory, planning, and other complex mental activities. In fact, poor performance on tasks measuring executive functions has been associated with decreased volume in

the prefrontal cortex

Decreases in the hippocampus have been associated with

deficits in episodic memory

the occipital lobe shows very little

age-related changes

Neuronal shrinkage, loss of glial cells, and reduction in myelination may be contributing to

the reduction in brain volume

Widening of the grooves (sulci) in the brain and shrinking of the convolutions of the brain (gyri) also occur with age, secondary to

loss of volume.

The white matter of the brain consists of

bundles of axons that connect areas of grey matter (the neuronal cell bodies) in the brain to each other and carry nerve impulses between neurons. A thin layer of fat, known as myelin, surrounds the axons providing electrical insulation, which is white in colour, giving rise to the name “white matter.”

The loss of grey-matter volume begins in early adulthood and continues throughout adulthood; the death of neurons has been identified as a possible cause of

grey-matter volume loss, this loss in volume may better be explained by a decrease in the size and number of connections between the neurons

The health of white matter also declines with age. Diffusion tensor imaging, which diffuses water through the white matter, is used to determine

the health of this part of the brain. These changes to the white matter are seen as abnormal areas of signal intensity on MRIs and are clinical markers of increased risk of depression, impaired gait and mobility, stroke, and dementia in both cross-sectional and longitudinal studies

Changes in neurotransmitters, most notably

dopamine, serotonin, and acetylcholine, also occur with age

Declines in dopamine have been associated with

declines in short-term memory, working memory, attention, learning, and mental flexibility

Changes in the way the brain processes serotonin have been associated with

cognitive decline in normal aging and dementia such as Alzheimer’s disease.

Decreases in acetylcholine in the hippocampus also have been commonly associated with

Alzheimer’s disease, but decreases in acetylcholine have not been consistently found during normal aging.

In addition, there is evidence of alterations in

the size, number, and density of blood vessels in the brain with age

Limitations of cognitive functioning include

small sample sizes, narrow age ranges (i.e., young and older adults but no middle-aged adults), and in many prior studies, separate consideration of different types of structural variables when there is evidence that they are not independent of each other.

cognitive reserve (CR)

arose after numerous research findings showed that the degree of damage to the brain does not always correlate with cognitive and functional abilities. In other words, two people with similar levels of brain damage or pathology do not necessarily function at the same level

A high CR

is assumed to decrease the susceptibility to clinical manifestations of structural brain changes and is influenced by lifetime experiences including factors such as higher educational attainment, complex work experiences, bilingualism, social engagement, and an active lifestyle. It is related to less severe or delayed clinical manifestations in diseases such as Alzheimer’s disease, Parkinson’s disease, traumatic brain injuries, and multiple sclerosis.

Common ways to measure cognitive reserve are by

measuring occupation, number of years of education, and the amount of leisure activities an individual engages in, usually within the last year

There is evidence that CR is modifiable and that people could change their risk of cognitive decline through

performance of mentally and physically stimulating activities. It should be noted that research on the protective factors of CR for cognitive decline is somewhat conflicting but this is likely due to the multitude of measures that can be used to determine CR.

Grotz and colleagues (2017) and Kartschmit and colleagues (2019) found that, in general, there is a lack of reliable information about the measurement properties of questionnaires measuring CR which is important area of research because

if individuals with low CR, who potentially are at greater risk of developing brain diseases can be identified, strategies can be implemented in an effort to increase CR in these individuals.

Two of the most basic cognitive functions affected by age are

memory and attention

Sensory memory is divided into five memory types (one for each of the senses) The three most-studied forms of sensory memory are

iconic memory (visual), echoic memory (sound), and tactile memory (touch).

Information is passed from our sensory memory to our short-term memory through the process of

attention.

He found that memory loss is greater in the first few days after learning new information, with the rate of forgetting much slower as the days progress. This has come to be known as

the forgetting curve

Changes in central executive function with age have been identified as a key contributor to

age-related declines across a range of cognitive tasks

Due to the changes in working memory with age, it’s not unusual for older adults to experience

simple forgetfulness during everyday abilities and activities (e.g. missing keys, being slower in recalling names and dates),

Tasks that have been developed to assess working-memory include

reading-span tasks, the Trail-Making tasks, and digit-span tasks

The most prominent theories about aging memory are

a reduction in processing resources, a general slowing in the speed of processing information, and difficulties in inhibiting irrelevant information.

The reduction of processing resources theory hypothesizes that

older adults do not have as many processing resources available as younger adults, and this leads to less efficient encoding and retrieval of information. Older adults show impairments on tasks with high attentional demands, with relatively no signs of impairment on tasks that are less demanding.

The speed of processing theory hypothesizes that

increased age is associated with a decrease in the speed with which many processing operations can be executed and that this reduction in speed leads to impairments in cognitive functioning

The inhibition theory proposed by Hasher and Zacks (1988) theorizes that

inhibitory processes, which are responsible for regulating the information that enters and leaves working memory, weakens with age.

HM story

after suffering from severe seizures due to a bicycle accident in childhood, HM underwent an experimental surgery at age 27, where parts of his hippocampus and amygdala were removed to alleviate his seizures. While the surgery was successful in reducing seizures, it resulted in profound memory loss. HM was unable to form new memories (anterograde amnesia) and had difficulty recalling past events (retrograde amnesia). His case provided critical insights into the role of the hippocampus in memory formation and significantly advanced the understanding of memory research. Dr. Brenda Milner's work with HM established her as a leading neuroscientist and highlighted the importance of studying memory disorders.

Research shows that older individuals have more difficulty with

consolidating and retrieving information. Specifically, older individuals tend to show more deficits on tests of free recall as compared to deficits on recognition memory (Morcom & Friston, 2012). However, how the information is presented to older adults affects episodic memory recall.

Older adults often report difficulties in recalling the names of common objects or other well-learned information, The one change in semantic memory as part of normal aging is an increased difficulty in retrieving information that is otherwise accessible this is called

tip-of-the-tongue (TOT) phenomena.

Steps that older adults can take to enhance their memory and help to delay or even prevent dementia

Those steps include managing your health (e.g., eating a healthy diet, not smoking, exercising regularly) as well as engaging in activities that both stimulate (e.g., play board games, work on crosswords or other kinds of puzzles) and relax (e.g., reading, meditation, yoga) the brain.

Types of attention

sustained attention, selective attention, divided attention

Older adults are slower than younger adults in their response times to the targets, with these age differences attributed to

general slowing of information processing in older adults rather than due to changes in selective attention with age.

Age-related changes in colour perception can contribute to errors and a slower response time on the

Stroop task. This is an important consideration as this is a measure that is often used diagnostically.

Older adults are more negatively affected by the division of attention than are younger adults, and particularly so when

the demands of the task are high

There are age differences on more complex vigilance tasks

(e.g., detecting a small red square among larger red squares, especially if the stimuli are visually degraded or presented at a rapid rate).

The transmission deficit hypothesis (TDH)

holds that the mental connections linking an idea to its phonology (which is an ordered sequence of consonants and vowels) is very important in the process of linking an idea, such as an evil villain living in another galaxy who represents the dark side of the force, to the words, Darth Vader.

Older adults also are more likely to use

circumlocutions, a roundabout or indirect way of speaking in which the person uses more words than necessary to express an idea

Circumlocutions occurred more often in older adults in a

TOT state than the younger participants. In a recent study, Segaert and her colleagues (2018) found that higher physical fitness levels are associated with less language decline in healthy aging.

Higher aerobic fitness levels were associated with

better word finding abilities in older adults. The higher the older adults’ aerobic fitness level, the lower the probability of experiencing a tip-of-the-tongue state.

Under-accommodation

occurs when a communication partner fails to consider how normal age-related changes affect speaking and listening. This can create social isolation (even in a room full of people) a

Over-accommodation

occurs when the communication partner relies on negative stereotypes of the older adult to guide communication. This is insulting and patronizing and may discourage them from fully participating in a conversation

Both involve speaking to an older adult as though they were

incompetent and helpless. Elderspeak

Elderspeak is used is the Communication Predicament of Aging Model (CPAM), which is based on

the assumption that speakers make accommodations in their communication style based on observations of the listener.

Researchers have found that using elderspeak increased negative

vocalizations in residents (e.g., yelling out, wailing, crying) and resistance to care, particularly with those residents who have a dementia which distresses both residents and staff

Older adults in long-term care often do not speak their minds because

they find that it is more important to “fit in and not cause trouble.”

Psychometric approach to intelligence

This approach has dominated the study of intelligence since the 19th century.

fluid intelligence decreases with age while crystallized intelligence increases with age and only begins to show modest, if any, declines after the age of 70. This is known as

the classic aging pattern.

Salthouse took issue with the idea that

crystallized intelligence declines after the age of 70. He argues that crystallized intelligence may continue to grow into an individual's 80s or 90s but there is not a good way to measure this intellectual growth.

Contrary to earlier beliefs that intelligence declines significantly with age

study results over the years have consistently shown that there is no uniform pattern of age-related decline in intellectual abilities and the Classic Aging Pattern, the rate of decline in fluid intelligence was much slower than originally thought

Those reaching old age in the 1960s and 1970s and those reaching old age in the 1980s and 1990s. As you can see, relative to those born earlier, individuals in the later-born cohort showed, on average,

considerably better cognitive functioning at age 70 as well as lower rates of cognitive decline from ages 50 to 80. The cohort that was born later had higher scores throughout the entire age range on all abilities assessed, with the exception of number ability.

Higher educational attainment, as well as access to a higher quality of education in the later-born cohort, was thought to account for much of the cohort differences. It was not unusual for later-born cohorts of children to leave school as early as Grades 4 or 5, as children were needed to

work on the farm or go to work to help their families make ends meet.

Also included in the explanation of the observed cohort differences in intellectual functioning were advances in, and access to

technology; workplaces requiring individuals to use increasingly complex cognitive skills; and greater participation of women in the labour force.

Predictive validity of IQ scores in determining mortality is hampered by

reverse causality in that diseases such as diabetes or hypertension can cause cognitive decline, especially in older adults. However, studies in which the participants had their IQ assessed in childhood or early adulthood, which represents premorbid functioning, had lower mortality rates at follow-up in the absence of disease, minimizing this concern

In the relationship between childhood intelligence test scores and cause of death they found inverse associations for all major causes of death including

coronary heart disease, stroke, cancer, respiratory disease, digestive disease, external causes of death, and dementia. In general, the effect sizes were similar for women and men.

Factors that are thought to be associated with the maintenance of intelligence in older adults are

average to high socio-economic status, engagement in and exposure to stimulating environments, high intellectual status of spouse, strong social connections, as well as the maintenance of high levels of perceptual processing speed

Personality traits have been associated with higher levels of intelligence in later life. For example

positive beliefs, a flexible attitude, and the personality trait of openness to experience all have been associated with higher intelligence in older adults.

Two main types of training programs in the literature

cognitive training programs and cognitive stimulation programs

Cognitive training programs

that consist of directed practice of specific cognitive tasks Cognitive stimulation programs

Are these training programs effective?

Improved performance on trained tasks has much empirical and experimental support—however, far-transfer effects including improvements to general cognitive abilities and daily functioning are comparably lacking

One reason for the inconsistent pattern of results may be that there are

large differences across studies in the duration of the training program as well as the type and intensity of the training program. For example, cognitive training programs have ranged from a few days to months in duration, and trained individuals have been compared with active control groups in some studies and with passive, no-contact groups in others

The Advanced Cognitive Training for Independent and Vital Elderly (ACTIVE) study focused on

improving memory, processing speed, and reasoning in community-dwelling older adults. The findings showed that this training improved cognitive skills in these targeted domains but this training did not transfer to other cognitive domains. Nonetheless, these improvements could still be observed up to five years later in many of the participants

A more recent cognitive training method involves the use of

video games. The efficacy of video game training for enhancing cognitive ability has been the subject of several meta-analytic studies, with the results showing mixed findings. For example, one meta-analytic study observed minor but significant gains in overall cognitive ability including improved attention, speed of processing, and memory

Conversely, two meta-analyses examining the use of video games for cognitive training found

no evidence of improved cognitive ability or far-transfer outcomes in older adult populations

Lumosity brain-training program

agreed to settle the U.S. Federal Trade Commission (FTC) charges alleging that they deceived consumers with unfounded claims that playing Lumosity games could improve cognitive performance and delay cognitive impairment associated with age and serious health conditions. The creators and marketers paid out two million dollars in false advertising claims. Lumosity preyed on consumer’s fears about age-related cognitive decline when the company suggested that their games could prevent memory loss and the development of dementia. She went on further to say that Lumosity simply did not have the science to back up its advertisements.

Older adults who participate in any type of regular physical activity show less decline in

cognitive abilities such as working memory, attention, processing speed, and general mental functioning than those not participating in regular physical activity

Lehert and colleagues (2015) found that engaging in t'ai chi exercise

improved overall cognitive functioning.

Loughrey and colleagues (2017) examined the impact of the Mediterranean diet (MeDi) on the cognitive functioning of healthy older adults

It may also be beneficial for global cognitive functioning in healthy older adults. Results also showed evidence of some benefit of the MeDi in domains of delayed recall, working memory, processing speed, and reasoning ability.

Another health-related factor that can affect cognitive functioning in later life is the

medications that many older adults take.

Confusion is a serious side effect that can occur from

some medications or the interactions of several medications. If an older adult is overmedicated, this also can cause confusion and cognitive decline. The good news is that when medications are properly managed, there is little chance that adverse side effects such as confusion will occur.

Other factors to consider that can affect cognitive functions in older adults are poor nutrition as well as

alcohol abuse. In fact, high-level alcohol consumption (>14 drink units/week) is linked to an increase in dementia risk and significant alcohol abuse can cause dementia

Peak performance during middle adulthood in everyday problem solving may be that middle-aged adults have the

ideal balance of fluid and crystallized resources needed for everyday problem solving.

Memory, reasoning, and processing speed

were all significant predictors for everyday functioning and everyday problem solving, inductive reasoning independently accounted for the most variance in everyday functioning.

Willis and her colleagues (2006) also showed that older adults who underwent reasoning training showed less

functional decline in Instrumental Activities of Daily Living (IADLs) than an untrained control group, indicating the importance of reasoning for everyday problem solving.

Fluid ability was the primary predictor of performance on

everyday problem solving for young adults

But with increasing age, crystallized ability became the

dominant predictor. These findings suggest that crystallized knowledge may help older adults maintain problem-solving ability in the face of declining fluid ability.

Older adults actually showed better problem-solving abilities than young and middle-aged adults when they were presented with problems associated with

social conflict and interpersonal conflict. The solution to these types of problems rely more on wisdom and a broad range of social experiences rather than fluid ability

Possibility of domain-linked variations in performance is heightened by

taking a contextualist perspective on everyday problem solving.

A contextualist perspective highlights

the ways in which an individual’s coping strategies and task appraisals develop within the individual and are inherently linked to distinct domains that comprise the individual’s life. This perspective indicates that different domains may trigger variations in cognitive processing that, in turn, foster within-person and across-context variation in performance.