age-related cognitive decline

Cognitive decline in normal aging

How cognitive function declines with age

Older adults commonly need to practice more than younger adults to achieve the same level of performance. Such age deficits are at least partly due to poorer monitoring of their learning.

Failing to immediately retrieve well-known information does become more common with age, with an increase in "tips of the tongue" evident as early as the mid-thirties. Older people tend to be less likely than younger people to actively pursue a missing word.

Older adults are less likely than younger ones to use the appropriate brain regions when performing a memory task, and more likely to use cortical regions that are not as useful. But this can be at least partly overcome if the seniors are given specific strategy instructions.

Older adults appear to be particularly impaired in context processing — particularly seen in an inability to remember where they heard (or read, or saw) something. Because context is involved in many memory processes, this may have far-reaching implications. An impaired ability to remember context may reflect frontal-lobe inefficiency rather than aging per se.

Decreased ability to remember past events is linked to an impaired ability to imagine future events.

Older adults may compensate for cognitive decline by using additional brain regions. However, the downside is that these brain regions are then not available when a task requires them specifically. This may explain older adults' poorer performance on complex short-term memory tasks.

An important (perhaps even the most important) reason for cognitive decline in older adults is now seen to be a growing inability to filter out irrelevant/distracting information and inhibit processing. There can, however, be a decision-making/problem-solving advantage to this inclusion of apparently irrelevant information.

Older adults’ greater problems with multitasking stem from their impaired ability to disengage from an interrupting task and restore the original task.

There is growing evidence that memory problems (even amnesia) reflect confusion between memories more than loss of memory, and age-related difficulties reflect increasing difficulties in replacing out-of-date information with new, or distinguishing between them.

There do seem to be some gender differences in how brains change with age, which is consistent with the evidence that general intelligence is reflected in different brain attributes for men and women.

While IQ tends to drop with age, this may simply reflect perception deficits, not cognitive ones.

Brain regions that are especially affected by age include shrinking of the frontal lobe, especially the prefrontal cortex, of the medial temporal lobe, especially the hippocampus, and (for men only) the cerebellum. Aging also tends to degrade white matter, leading to brain networks growing less coordinated. The default network is most severely disrupted. Levels of the inhibitory neurotransmitter GABA also tend to decline with age, as does the levels of dopamine. Both are important for learning and memory.

See news reports

Rate of cognitive decline

White matter appears to decrease faster than grey matter, but doesn't begin to decline until the forties. Presumably this relates to the decline in processing speed that is the most evident characteristic of age-related decline.

Grey matter, on the other hand, declines at a fairly constant rate from adolescence, mirroring a decline in processing ability that seems to start as early as the twenties.

Cognitive decline seems to be faster in women than men. This presumably reflects apparent gender differences in brain activity. For example, while women seem to have a greater density of brain cells in the prefrontal cortex, they also show a steeper rate of decline so that, in old age, the density is similar between the genders.

There is some evidence that individual differences in processing speed and memory are more important than age, and that personality attributes affect the rate of cognitive decline and brain atrophy.

Some gene variants, including the so-called Alzheimer’s gene, are associated with a faster rate of decline, or an earlier start. These may be triggered by activity in early adulthood. Head size in adulthood also seems to affect rate of decline. Head size in adulthood reflects not only head size at birth, but growth in the early years — pointing to the importance of providing both proper nourishment and intellectual stimulation in these early years.

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Extent of cognitive decline in the population

Most older adults do not suffer cognitive impairment. Around 30-40% of adults over 65 have the type of cognitive loss we regard as a normal consequence of age — a measurable (but slight) decline on memory tests; a feeling that you're not quite as sharp or as good at remembering, as you used to be (age-related cognitive impairment). Around 10% of adults over 65 develop mild cognitive impairment (MCI), which does impact everyday living, and is a precursor of Alzheimer's.

There are significant differences in prevalence as a function of age. For example, in the U.S., a large sample found MCI in 9% of those aged 70 to 79 and nearly 18% of those 80 to 89. Prevalence decreased with years of education: 25% in those with up to eight years of education, 14% in those with nine to 12 years, 9% in those with 13 to 16 years, and 8.5% in those with greater than 16 years.

Large-scale population surveys of mild cognitive impairment in the elderly have produced large differences in national levels, ranging from 10% to 26%.

Although women may decline at a faster rate than men, prevalence of decline may be greater among men. For example, a large Dutch survey of those aged 85 and older found more women than men had good memory (41% vs 29%) and mental speed (33% vs 28%), despite the fact that more women than men had a limited education.

However, severe memory problems in the elderly have become more rare. The main reasons seem to be better physical fitness (partly due to better healthcare), higher levels of education, and greater personal wealth.

See news reports

 

Meditation's cognitive benefits

A critical part of attention (and working memory capacity) is being able to ignore distraction. There has been growing evidence that meditation training (in particular mindfulness meditation) helps develop attentional control, and that this can start to happen very quickly.

For example:

  • after an eight-week course that included up to 30 minutes of daily meditation, novices improved their ability to quickly and accurately move and focus attention.
  • three months of rigorous training in Vipassana meditation improved attentional control.
  • after eight weeks of Mindfulness Training, Marine reservists during pre-deployment showed increased working memory capacity and decreased negative mood (this training also included concrete applications for the operational environment and information and skills about stress, trauma and resilience in the body).
  • after a mere four sessions of 20 minutes, students produced a significant improvement in critical cognitive skills — and a dramatic improvement when conditions became more stressful (provided by increasingly challenging time-constraints).

There seem to be several factors involved in these improvements: better control of brainwaves; increased gray matter density in some brain regions; improved white-matter connectivity.

Thus, after ten weeks of Transcendental Meditation (TM) practice, students showed significant changes in brainwave patterns during meditation compared to eyes-closed rest for the controls. These changes reflected greater coherence and power in brainwave activity in areas that overlap with the default mode network (the brain’s ‘resting state’). Similarly, after an eight-week mindfulness meditation program, participants had better control of alpha brainwaves. Relatedly, perhaps, experienced Zen meditators have shown that, after interruptions designed to mimic spontaneous thoughts, they could bring activity in most regions of the default mode network back to baseline faster than non-meditators.

Thus, after an 8-week mindfulness meditation program, participants showed increased grey-matter density in the left hippocampus , posterior cingulate cortex, temporo-parietal junction , and cerebellum , as well as decreased grey-matter density in the amygdala . Similarly, another study found experienced meditators showed significantly larger volumes of the right hippocampus and the right orbitofrontal cortex, and to a lesser extent the right thalamus and the left inferior temporal gyrus.

These areas of the brain are all closely linked to emotion, and may explain meditators' improved ability in regulating their emotions.

Thus, long-term meditators showed pronounced differences in white-matter connectivity between their brains and those of age-matched controls, meaning that meditators’ brains were better able to quickly relay electrical signals. The brain regions linked by these white-matter tracts include many of those mentioned as showing increased gray matter density. Another study found that a mere 11 hours of meditation training (IBMT) produced measurable changes in the integrity and efficiency of white matter in the corona radiata (which links to the anterior cingulate cortex, an area where attention and emotion are thought to be integrated).

It’s an interesting question, the extent to which poor attentional control is a reflection of poor emotional regulation. Obviously there is more to distractability than that, but emotion and attention are clearly inextricably entwined. So, for example, a pilot study involving 10 middle school students with ADHD found that those who participated in twice-daily 10 minute sessions of Transcendental Meditation for three months showed a dramatic reduction in stress and anxiety and improvements in ADHD symptoms and executive function.

The effects of emotion regulation are of course wider than the effects on attention. Another domain they impact is that of decision-making. A study involving experienced Buddhist meditators found that they used different brain regions than controls when making decisions in a ‘fairness’ game. The differences reflected less input from emotional reactions and more emphasis on the actual benefits.

Similarly, brain scans taken while experienced and novice meditators meditated found that periodic bursts of disturbing noise had less effect on brain areas involved in emotion and decision-making for experienced meditators compared to novices — and very experienced meditators (at least 40,000 hours of experience) showed hardly any activity in these areas at all.

Attention is also entwined with perception, so it’s also interesting to observe that several studies have found improved visual perception attendant on meditation training and/or experience. Thus, participants attending a three-month meditation retreat, showed significant improvements in making fine visual distinctions, and ability to sustain attention.

But such benefits may depend on the style of meditation. A study involving experienced practitioners of two styles of meditation (Deity Yoga (DY) and Open Presence (OP)) found that DY meditators were dramatically better at mental rotation and visual memory tasks compared to OP practitioners and controls (and only if they were given the tasks immediately after meditating). Similarly, a study involving Tibetan Buddhist monks found that, during "one-point" meditation, monks were significantly better at maintaining their focus on one image, when two different images were presented to each eye. This superior attentional control was not found during compassion-oriented meditation. However, even under normal conditions the monks showed longer stable perception compared to meditation-naïve control subjects. And three months of intense training in Vipassana meditation produced an improvement in the ability of participants to detect the second of two visual signals half a second apart (the size of the improvement was linked to reduced brain activity to the first target — which was still detected with the same level of accuracy). Similarly, three months of intensive meditation training reduced variability in attentional processing of target tones.

References

You can read about these studies in more detail in the aggregated news reports on meditation. Three studies were mentioned here without having appeared in the news reports:

Lutz, A., Slagter, H. A., Rawlings, N. B., Francis, A. D., Greischar, L. L., & Davidson, R. J. (2009). Mental Training Enhances Attentional Stability: Neural and Behavioral Evidence. J. Neurosci., 29(42), 13418-13427. doi:10.1523/JNEUROSCI.1614-09.2009

Tang, Y.-Y., Lu, Q., Geng, X., Stein, E. A., Yang, Y., & Posner, M. I. (2010). Short-term meditation induces white matter changes in the anterior cingulate. Proceedings of the National Academy of Sciences, 107(35), 15649 -15652. doi:10.1073/pnas.1011043107

Travis, F., Haaga, D., Hagelin, J., Tanner, M., Arenander, A., Nidich, S., Gaylord-King, C., et al. (2010). A self-referential default brain state: patterns of coherence, power, and eLORETA sources during eyes-closed rest and Transcendental Meditation practice. Cognitive Processing, 11(1), 21-30. doi:10.1007/s10339-009-0343-2
 

 

 

Estrogen's effect on memory & learning

Estrogen's effect on the brain is a complex story, one which we are only beginning to understand. We know it's important for women, but we're not sure about the details. One of the problems is that it appears to interact with stress. There are two aspects to estrogen's effects on women: normal monthly fluctuations in estrogen levels, and menopause.

It's also important to distinguish post-menopause (once you have completely stopped menstruating) from perimenopause (the years of menstrual irregularity leading up to this).

In general, the last few years of research seem to be coming to the conclusion that any cognitive problems women experience as they approach menopause is limited, both in time and in task, and depends in part on other factors. For example, those who experience many hot flashes may have poorer verbal memory, but the main cause for this may be the poorer sleep quality; those who are distressed or experience mood changes may find their memory and concentration affected for that reason.  These findings suggest the best approach to dealing with cognitive problems in perimenopause is to tackle the physical and/or emotional causes.

Post-menopause is different. Post-menopause is all about low estrogen levels, and the importance of estrogen for brain function. Nevertheless, estrogen therapy for postmenopausal women has had inconsistent results; there has even been some research suggesting it may increase the risk of later dementia. There is also some suggestion that it may not help those women who have cognitively stimulating environments, or are highly educated. And other indications that timing might be critical -- the age at which you begin hormone therapy. At the moment, we simply have too little clear evidence to warrant recommending hormone therapy for cognitive reasons (particularly in light of the possible cancer risk), or to know when it might be effective.

Excitingly, however (because there is no downside!), there is some evidence that physical exercise can counter the cognitive decline postmenopausal women may experience. There's also a study suggesting that the effect of low estrogen after menopause is not to impair cognition but simply to change it -- however, because women aren't prepared for, or understand, these changes, they perceive it as impairment. That would suggest that what is needed is an education program in how the brain changes (but first we have to understand exactly how it does change!).

See news reports

Memory FAQs

Is there such a thing as a photographic memory?

While one cannot completely discount the possibility of a photographic memory, since there have been some very rare individuals with truly extraordinary powers of memory, those examples of outstanding memory that have been studied have all turned out to be due to the use of powerful memory strategies.

The lesson we can draw from most examples of "photographic memory" is that there are truly effective memory strategies, and anyone who wants to put in the requisite time and energy can achieve such a powerful memory. However, the point that most so-called "memory trainers" don't make, is that to achieve such levels of mastery requires a great deal of practice. Moreover, their accomplishments are specific to the memory task they have practiced. That is, achieving a high level of skill at remembering names doesn't mean you'll be any better at remembering things you've read, or things you have to do.

Practicing a particular strategy leads to skill at that strategy, it doesn't lead to a "good memory". There is no such thing as a good memory, and no such thing as a bad one. You may be good at remembering some things, and poor at remembering others.

It should be noted I am only talking here of people with no brain abnormalities. It does seem that particular brain abnormalities can lead to ways of processing information that are dramatically different from the normal (see the case of Kim Peek). However, it may well be that such a memory limits understanding.

References

Ericsson, K.A. (1985). Memory skill. Canadian Journal of Psychology, 39, 188-231.

Higbee, Kenneth L. Your memory. How it works and how to improve it. NY: Simon & Schuster, Inc., 1988.

Thompson, C. P., Cowan, T.M. & Frieman, J. Memory search by a memorist. Hillsdale, NJ: Lawrence Erlbaum Ass., 1993.

Will memorizing lists and speeches improve my memory?

No. Many "memory trainers" tell you memory is like a muscle, and if you exercise it it will become stronger. They tell you that memorizing things will make your memory better. However, you can memorize until you're blue in the face, and this won't give you a better memory. Indeed, if you set aside time each day for memorizing, you will usually find that eventually it takes you longer to memorize information (boredom probably!)1.

The value of memory "exercise" lies in what you're doing. If you're simply learning by rote repetition, this does nothing, because memory is not a muscle. If you're using a memory strategy of some kind, then of course practice will improve your skill at that strategy. Hence, if you spend an hour every day on memorizing using a mnemonic strategy (say the method of loci, or the pegword strategy), you will indeed become better at using that strategy. In fact, it takes a great deal of practice before you can effectively use most of these strategies.

However, this will not "improve your memory", because memory is not a thing. What it does, is make you better at that particular strategy, and only that strategy.

References

Herrmann, D.J. & Searleman, A. 1990. The new multimodal approach to memory improvement. In G. Bower (ed.) Advances in Learning and Motivation, New York: Academic Press.

1. Higbee, Kenneth L. Your memory. How it works and how to improve it. NY: Simon & Schuster, Inc., 1988.

I've read that people only use 10% of their brain. Is this true?

This, or variants of this, are repeated in a great many popular books about the brain and memory. Quite where this idea started I have no idea. It is not at all clear what it means, or what evidence exists for such a statement. The brain contains billions of neurons and I doubt many of them are sitting around just basking in the oxygen, waiting for you to come up with an exciting new strategy that will suddenly trigger them into action, after decades of inertness.

The brain is the most active part of our body, and its activity derives from the connections between those billions of neurons. Memory and thought are contained in patterns of activation, not in single neurons. The essence of how the brain works is that the neurons are all connected. The brain is a network. How can a network work if a significant portion of it isn't working?

The key to improving your mental skills is in making good connections. How can anyone say your connections are only 10% of what they could be? And what on earth would that mean?

The "statistic" is meaningless. What can be said, truthfully, is that we can all improve the organization of our memories.

I seem to have more trouble remembering words and names I know perfectly well. Am I getting Alzheimer's?

As we get older, it is normal to experience more frequent memory blocks for names of objects and people.Not, interestingly enough, for abstract words.

When you were in your twenties, you almost certainly didn’t have as many memory blocks — occasions when something is ‘on the tip of my tongue’. But this is not because you were less forgetful then. It is because memory blocks occur when information has not been retrieved for a long time. Obviously, the older you become, the more information there will be in your memory that has not been recalled for a long time. Hence, more memory blocks.

Related article

Why do I have so much trouble remembering people's names?

The principal reason for the common tendency to forget people's names is very simple - we usually don't pay enough attention when we hear them. But why are names so much harder than other things to remember? Or do they simply appear so, because we feel so bad when we forget a name?

Well, no, personal names are harder to remember than many other types of information, and the reason is simple - connection, or the lack of it. The main tenet of memory is that well-connected information is easy to remember. The more connections a piece of information has, the more likely you are to find it. But what connections does a name have with a person? For the most part, names are arbitrary.

Because the information itself isn't meaningful, you have to make a special effort to create a meaningful connection for it.

Related article

Does playing tapes while you're asleep help you learn?

Not really.

There are circumstances in which learning can occur while you're asleep, but it's a far cry from the science-fiction idea of achieving native fluency in a foreign language after a few nights or a few hours in the sleep lab.

  • The information to be learned cannot require understanding - it is thus useful for memorizing rather than true learning.
  • You must be in the right stage of sleep - a light, drowsy state.
  • The 'sleep learning' must augment ordinary learning, it can't take the place of it. That is, the exact information must also be presented while you are awake and attending to it.

References

Baddeley, Alan.Your memory: A user’s guide. (2nd ed.) London: Penguin Books, 1994.

Higbee, Kenneth L. Your memory. How it works and how to improve it. NY: Simon & Schuster, Inc., 1988.

Do mnemonic strategies really work?

Certainly. Mnemonic strategies work. However, for the most part they are strategies that require a great deal of practice to master, and it is arguable whether the tasks they are suited for are really worth such an effort. For example, to go to the trouble of using the method of loci simply to save yourself the effort of writing a shopping list is fairly pointless. However, if you have a professional need to remember lots of names, mastering the face-name association strategy is probably worth the (not inconsiderable) effort.

Related article

It's said that everything we've ever experienced is recorded somewhere in our brain. Is this true?

No.The origin of this belief seems to lie in the work done by a Canadian surgeon, Wilder Penfield, in the 1950s. Taking advantage of the fact that the brain itself has no sensors for pain, Penfield (with the patients' consent) used the opportunity granted by operations on the brain to investigate the storage of memory. While the brain was exposed, and the patients fully conscious, Penfield stimulated different parts of the cortex electrically. In most cases, the patients had no particular sensation or experience to report, but occasionally they would claim to re-experience very vivid scenes from their past.

This was taken by many at the time to demonstrate that memory works like a camera - that every detail is experienced, and is faithfully recorded in the brain, and nothing is truly lost. However, it now seems clear that the interpretation of these results was simplistic.

Not only did such triggered memories occur in only 40 of 520 patients, but the vividness and specificity of such memories was overstated. It seems rather, from subsequent studies, that such memories are more like dreams - generalized experiences with no particular spatio-temporal context.

Moreover, if the same area was stimulated on a different occasion, a different memory would be elicited, and sometimes the same memories were generated by stimulating different areas. Nor, it must be said, was any attempt made to test the veracity of these 'memories'.

References

Greenfield, Susan. The human brain: A guided tour. London: Weidenfeld & Nicolson, 1997.

Schacter, Daniel L. Searching for memory: The Brain, the Mind, and the Past. NY: Basic Books, 1996.

Why do we forget?

Forgetting, it can be argued, is adaptive. The ability to abstract general rules from specific instances is far more useful than the ability to remember every specific detail, and the one seems to preclude the other1.

As yet there is no evidence that information stored in memory can actually disappear (except of course when the brain is physically damaged). However, when information is put into the long-term memory store, it passes through what is called "working memory". Information can be lost in working memory. If the information doesn't make it through the encoding process (when it is "in" working memory), then it will not enter memory, therefore you cannot "remember" it - although, because of other information encoded at the time, you may have a vague feeling that such information exists.

Forgetting, then, occurs because:

  • it was never properly encoded into memory in the first place, or
  • you can't find it

A failure to find a specific memory generally occurs because of interference from other memories.

1. Schacter, Daniel L. Searching for memory: The Brain, the Mind, and the Past. NY: Basic Books, 1996.

Am I too old to learn?

No.

It is true that memory performance begins to decline after the mid-forties, but the effects of age on memory are complex, as memory itself is complex. It is not true that a particular seventy-year-old necessarily has a 'worse' memory than his thirty-year-old grandson. It is almost certainly true that they each have particular memory tasks at which they are better than the other. It is probably true that the grandson remembers most information with less effort than his grandfather. It is not true that the grandfather can't match his grandson's performance with more effort - or more cunning. If one is skilled at specific memory strategies, and the other isn't, this is probably more important than any age differences.

Think of veteran marathon runners. There’s no way that they’re going to match the speed of a marathon runner in their twenties. But most people couldn’t run a marathon at all (without training). Maybe older adults can’t match the performance of younger adults when both receive the same training. But why should that matter? It doesn’t mean the older adult can’t achieve considerable memory improvement with instruction tailored to their needs, and more extensive practice.

For example, our memory for nonverbal information seems to decline faster than verbal information as we get older. Therefore, memory strategies involving visual imagery are typically less useful for older adults.

Older adults have a big advantage to offset the slowness that comes with increasing age. Experience. A good memory is an organized memory, is a richly connected memory. With a wealth of experience, you have the potential for many connections. With the right strategies, such rich connectivity can help your remembering.

References

Baddeley, Alan.Your memory: A user’s guide. (2nd ed.) London: Penguin Books, 1994.

Mild Cognitive Impairment

Except in the cases of stroke or traumatic brain injury, loss of cognitive function is not something that happens all at once. Cognitive impairment that comes with age may be thought of as belonging on a continuum, with one end being no cognitive impairment and the other end being dementia, of which Alzheimer's is the most common type.

Most older adults are actually at the "no impairment" end of the continuum. A further 30-40% of adults over 65 will have what is called "age-related memory impairment", which is the type of cognitive loss we regard as a normal consequence of age -- a measurable (but slight) decline on memory tests; a feeling that you're not quite as sharp or as good at remembering, as you used to be.

Only about 1% of these people will develop Alzheimer's.

But around 10% of adults over 65 develop "mild cognitive impairment", and this is a precursor of Alzheimer's. This doesn't mean someone with MCI will inevitably get Alzheimer's in their lifetime, but their likelihood of doing so is substantially increased.

Whether you are one of those 10% depends in part on your age and your level of education. A study2 of nearly 4000 people from the general population of a Minnesota county, run by the Mayo Clinic, indicates 9% of those aged 70 to 79 and nearly 18% of those 80 to 89 have MCI. The prevalence decreased with years of education: it was 25% in those with up to eight years of education, 14% in those with nine to 12 years, 9% in those with 13 to 16 years, and 8.5% in those with greater than 16 years.

Whether or not this will develop into Alzheimer’s can be predicted with a reasonably high level of accuracy (75%) by the rate at which brain tissue is being lost, and in particular the rate at which it is being lost in the hippocampus (arguably the most important region for memory in the brain). Whether actions known to build brain tissue (physical exercise, mental stimulation) can counteract that in this population is not yet known — but it certainly can’t hurt!

Mild cognitive impairment doesn’t necessarily mean memory problems. There are two types of MCI: those with the amnesic subtype (MCI-A) have memory impairments only, while those with the multiple cognitive domain subtype (MCI-MCD) have other types of mild impairments, such as in judgment or language, and mild or no memory loss. Both sub-types progress to Alzheimer's disease at the same rate, but they do have different pathologies in the brain.

Mild cognitive impairment is not necessarily obvious to outside observers. A person with it can function perfectly well, and although they may feel their impairment is obvious to all around them, it's not likely to be obvious to anyone not living with them.

A person suffering from mild cognitive impairment may find that they have problems with:

  • finding the right words
  • making decisions
  • remembering recent events
  • placing things in space (for example, getting the proportions right when drawing a simple object such as a box).

Essentially, age-related cognitive impairment might be thought of as slight, non-important, cognitive impairment, while mild cognitive impairment is a condition where significant cognitive impairment exists which nevertheless doesn't affect daily functioning. Dementia is significant cognitive impairment that does interfere with daily life.

References: 
  1. Becker, J.T. et al. 2006. Three-dimensional Patterns of Hippocampal Atrophy in Mild Cognitive Impairment. Archives of Neurology, 63, 97-101.
  2. Petersen, R. et al. 2006. Study presented April 4 at the American Academy of Neurology meeting in San Diego. Press release
  3. Quinn, J.F. & Kaye, J.A. 2004. Study presented at the 56th annual meeting of the American Academy of Neurology in San Francisco. Press release
  4. Small, G.W. 2002.What we need to know about age related memory loss. British Medical Journal, 324, 1502-1505.

The Seattle Longitudinal Study of Adult Intelligence

The Seattle Longitudinal Study of Adult Intelligence has followed a group of more than 5000 people for well over four decades. The program began in 1956 and participants have been tested across a whole gamut of mental and physical abilities at seven year intervals since that date.

The study has found:

  • no uniform pattern of age-related change across all intellectual abilities
  • some support for the idea that abilities that are primarily genetically determined tend to decline earlier than abilities that are primarily acquired through schooling or experience (although there may be gender differences here)
    • although abilities that are primarily genetic may decline earlier, abilities acquired through training decline more steeply after late 70s the change in perceptual speed begins in young adulthood and declines in a linear fashion (that is, the rate of decline is constant)
    • the rate and magnitude changes in intelligence seen in those entering old age showed greater decline in the 1st 3 cycles (till 1970); at the same time, younger members are scoring lower on tests at the same age.
    • a decline in psychometric abilities is not reliably observed before 60, but is reliably observed by 74. However, even by 81, fewer than half showed reliable decrements over the past seven years.
    • the size of this decline however is significantly reduced when age changes in perceptual speed are taken into account.
    • substantial cohort / generational differences have been observed. Later-born groups have attained successively higher scores at the same ages for inductive reasoning, verbal meaning, and spatial orientation; however, they’ve scored successively lower in number skill and word fluency (number skill peaked with the 1924 cohort). These changes presumably reflect educational changes.
    • substantial similarity between parents and their adult children and between siblings has been found for virtually all mental abilities and measures of flexibility (the exceptions are the attitude measure of social responsibility, and a measure of perceptual speed). The magnitude of similarity varied for different abilities, and was closer between parent & child than between siblings.
    • the following variables may reduce the risk of cognitive decline in old age:
      • absence of chronic diseases
      • a complex and intellectually stimulating environment
      • a flexible personality style at mid-life
      • high intellectual status of spouse
      • maintenance of high levels of perceptual processing speed
    • cognitive training studies suggested that the observed decline in many community-dwelling older people is probably a function of disuse and is often reversible. Some 2/3 of participants in a cognitive training program showed significant improvement, and 40% of those who had declined significantly were indeed returned to their earlier (pre-decline) level of cognitive functioning. These training gains were retained over seven years.
References: 
  1. Schaie, K. Warner 1998. The Seattle Longitudinal Studies of adult intelligence. In M. Powell Lawton & Timothy A. Salthouse (eds) Essential papers on the psychology of aging. NY: NY Univ Pr. Pp263-271.

Why do some cognitive processes decline with age?

Most basic cognitive processes decline with advanced age at higher levels of difficulty.

Part of this reflects the slowing down that occurs with age.

It does seem likely however that there is a reduction in processing capacity with age.

Strategies that reduce the memory load of a task are therefore likely to be of help to older adults, for example:

  • Use of pictures as memory aids
  • Text that is clear and explicit

Practicing new skills and habit until they become automatic is also likely to be of even more help to older adults than younger adults (because it reduces memory load).

Irrelevant detail can be more distracting for older adults, and this may also play a part in cognitive decline.

Most cognitive processes decline with age

It does appear that most component processes of cognition decline with advanced age if the difficulty level is sufficiently high. For example, the following processes have all shown age effects:

  • processes involving attention
  • working memory capabilities(the amount of information you can work with without losing track of any)
  • understanding text
  • making inferences
  • encoding(putting information into memory) and retrieval (finding information in memory)

Other processes however, show little or no decline with age, for example:

  • picture recognition
  • implicit memory (information that can't be brought to mind but can be seen to affect behavior)
  • prospective memory (remembering things you need to do)

Additionally, older adults’ performance on highly practiced expert skills can match that of young adults (e.g., typing, bridge playing, chess).

Cognitive decline in normal aging mainly due to a reduced working memory capacity?

It would seem from this that cognitive decline in old age may be primarily due to the reduction in processing capacity - understanding text, making inferences, paying attention are all processes that depend heavily on your working memory capability. Accordingly, it has been theorized that cognitive aids that minimize the use of processing resources might be effective in helping older adults.

Since picture recognition is one of those cognitive processes that don't appear to be affected by age, pictures may well provide effective memory support for older adults. For text, instructions that explicitly present material rather than requiring subtle inferences (which requires more processing), would be better.

This theory that age-related cognitive decline is due to decreased processing resources also suggests that automatizing components of complex behaviors would be an effective strategy for older adults.

Any skill that is practiced sufficiently becomes "automatized" (think of driving a car or playing the piano). A skill or habit that has been practiced to sufficient level to become automatic will never be completely lost. Unfortunately, research does suggest that older adults require a lot more practice than younger adults to achieve automatization - but the benefit to them may well be greater.

Other theories for age-related cognitive decline

It has also been theorized that age-related cognitive decline may result primarily from the slowing down that occurs with age. There is certainly little doubt about the fact of age-related slowing. But it seems likely that there is more involved than simply this, as age differences are still found on many tasks even when there is unlimited time to do them. It may well be that there is an interaction between slower processing and decreased capacity, causing timing to be more critical in complex situations (e.g., approaching a complex traffic interchange on a freeway at relatively high speed). Practice does improve speed in older adults (though not to the level that it does in younger adults).

Another theory is that older adults develop problems with the inhibitory mechanisms in working memory (the part of our brain that enables us not to pay attention to irrelevancies), and it is this that gives the impression that there has been a decrease in processing resources. A faulty inhibitory mechanism would cause older adults to pay more attention to irrelevant detail and encourage incorrect interpretations of context. There is some evidence that older adults find irrelevant information more distracting than do young adults.

References: 
  1. Park, Denise C. Applied cognitive aging research. Pp449-93. In Craik, Fergus I. M. & Salthouse, Timothy A. (eds). 1992. The Handbook of Aging and Cognition. Hillsdale, NJ: LEA. Pp111-165.

Memory in normal aging

People are poor at assessing their own memory

One thing research seems to show rather consistently is that, for older adults in particular, beliefs about one's own memory performance have little to do with one's actual memory performance¹. People who believe they have a poor memory are usually no worse at remembering than those who believe they have a good memory.

One theory for why this might be, is that people may be influenced by their general beliefs about how memory changes with age. If you believe that your memory will get progressively and noticeably worse as you get older, then you will pay more attention to your memory failures, and each one will reinforce your belief that your memory is indeed (as expected) getting worse.

Memory decline can be a self-fulfilling prophecy

Research has also shown that common, everyday memory failures tend to be judged more harshly when the failure belongs to an older adult². What is laughed off in a younger adult is treated as an indication of cognitive decline in an older person.

There are ways in which cognitive function (memory, reasoning, problem-solving, etc) declines with age, but it would be fair to say that general belief over-estimates the extent of this. It is, to a large extent, a self-fulfilling prophecy. If you believe deterioration is inevitable, you are not likely to make any effort to halt it.

Memory decline is associated with physical factors

A large-scale study that tracked seniors over a ten-year period found that cognitive decline is not a normal part of aging for most elderly people: 70% of the nearly 6000 seniors in the study showed no significant decline in cognitive function over the ten-year period. These people had two factors in common: they did not carry any of the apolipoprotein E4 genes (often associated with Alzheimer's disease), and they had little or no signs of diabetes or atherosclerosis³.Other factors that have also been implicated in age-related cognitive decline are obesity, smoking, and high blood pressure. Indeed, researchers have suggested that risk factors for cardiovascular disease are also risk factors for cognitive decline: what's bad for the heart is also bad for the brain.

References: 
  1. Hertzog, C. & Dunlosky, J. 1996. The aging of practical memory: an overview. in Herrmann, D.J., McEvoy, C., Hertzog, C., Hertel, P. & Johnson, M.K. (eds). Basic and applied memory research: Vol. 1:Theory in context. NJ: Lawrence Erlbaum.
  2. Erber, J.T., Szuchman, L.T & Rothberg, S. T. 1990. Everyday memory failure: Age differences in appraisal and attribution. Psychology & Aging, 5(2), 236-241.
  3. Haan, M.N., Shemanski, L., Jagust, W.J., Manolio, T.A. & Kuller, L. 1999. The Role of APOE4 in Modulating Effects of Other Risk Factors for Cognitive Decline in Elderly Persons. JAMA, 282, 40-46.

Word-finding problems

It is normal for word-finding problems to increase as we age

It is normal for us to be slower in processing information as we age

Difficulty in retrieving words does not mean the words are lost; there is no evidence that we lose vocabulary in normal aging

There is little evidence for any change in semantic structure (the organization of words in memory) with age

Older adults probably have more trouble dealing with large amounts of information

Older adults may develop different strategies as they age, probably to accommodate their decline in processing speed and processing capacity

What do we mean by word-finding problems?

Here are some examples:

  • increasing use of circumlocutions rather than specific terms (e.g., "I wonder where the thing that goes here is")
  • use of empty phrases, indefinite terms, and pronouns without antecedents (i.e., referring to something or someone as "it" or "him / her" without first identifying them by name)
  • increased frequency of pauses

These problems are all characteristic of Alzheimer's, but also, to a much lesser extent, of normal aging.

Verbal fluency declines with age

Verbal fluency is measured by how many words fitting a specific criteria you can generate in a fixed time (for example, how many types of fruit you can list in a minute).

Verbal fluency often (but not always) declines as we age. This may be partly because older adults are slower to access information.

Tip-of-the-tongue experiences increase with age

There is no evidence that normal older adults actually lose the meanings of words they know.

Older adults do however have more word-finding problems than younger adults. In particular, as we get older we tend to experience more experiences when the word we are searching for is "on the tip of my tongue" [1]. (For more detail about this, see the research report at Burke 1991)

Picture-naming errors also increase, though not perhaps until the eighties [2].

Some studies have found a decline in older adults’ ability to produce words when given their definitions, but others haven’t. This may relate to strategy differences.

No structural changes to memory in normal aging

So, older adults do show some of the same type of word-finding problems as Alzheimers patients do, but to a considerably smaller degree. There is little evidence however that this decline is due to any structural changes in semantic memory with age. Normal younger and older adults give the same sort of responses. (Alzheimers patients on the other hand, become more eccentric in their word associations).

Older adults may tend to use different memory strategies than younger adults

While older adults are slower to make category judgments (e.g., "Is a tomato a fruit? True or false"), they do not give responses different from those of younger adults, supporting the view that semantic organization hasn't changed. However, there is some evidence that young and old differ in the way they judge similarity (older adults seem to rely more on distinctive features; younger adults use both common and distinctive features). This may however be due to strategy differences.

There is no evidence for any decline in prose comprehension with age. However, when there is a large load on memory (when the text is complex, for example), older adults find retrieving general knowledge more difficult.

It appears that encoding of new information might become less context-specific with age, but this may only relate to particular types of context information. It might only be that older adults are less inclined to attend to such (largely irrelevant) details as: whether something was printed in upper or lower case; the sex of a speaker; the color in which a word is printed. The temporal and spatial contexts are also likely to be less important. In other words, older adults seem to encode less information about the source of new information (the circumstances in which the information was acquired) than younger adults.

References: 
  • Light, Leah L. The organization of memory in old age. In Craik, Fergus I. M. & Salthouse, Timothy A. (eds). 1992. The Handbook of Aging and Cognition. Hillsdale, NJ: LEA. Pp111-165.
  1. Burke DM, MacKay DG, Worthley JS, & Wade E. 1991. On the tip of the tongue: What causes word finding failures in young and older adults? Journal of Memory and Language, 30, 542-79.
    Cohen G & Faulkner D. 1986. Memory for proper names: Age differences in retrieval. British Journal of Developmental Psychology, 4, 187-97.
  2. Albert MS, Heller HS, & Milberg W. 1988. Changes in naming ability with age. Psychology and Aging, 3, 173-8.
    Borod JC, Goodglass H, & Kaplan E. 1980. Normative data on the Boston Diagnostic Aphasia Examination, Parietal Lobe Battery, and the Boston Naming Test. Journal of Clinical Neuropsychology, 2, 209-15.
    Van Gorp W, Satz P, Kiersch ME & Henry R. 1986. Normative data on the Boston Naming Test for a group of normal older adults. Journal of Clinical and Experimental Neuropsychology, 8, 702-5.
    Mitchell DW. 1989. How many memory systems? Evidence from aging. Journal of Experimental Psychology: Learning, Memory & Cognition, 15, 31-49. (no age effect found).

Tip-of-the-tongue experiences

In a tip-of-the-tongue experience, you typically know quite a lot of information about the target word without being able to remember the word itself.

Remembering often occurs sometime later, when you have stopped searching for the word.

Often a similar sounding word seems to block your recall, but these probably don't cause your difficulty in remembering.

TOTs probably occur because of there is a weak connection between the meaning and the sound of a word.

Connections are weak when they haven't been used frequently or recently

Aging may also weaken connections.

TOTs do occur more frequently as we age.

In general, this increase in TOTs with age is seen in poorer recall of names (proper names and names of things). Abstract words do not become harder to recall with age.

Keeping your experience of language diverse (e.g., playing scrabble, doing crosswords) may help reduce TOTs.

What is a tip-of-the-tongue experience?

The tip-of-the-tongue experience (TOT) is characterized by being able to retrieve quite a lot of information about the target word without being able to retrieve the word itself. You know the meaning of the word. You may know how many syllables the word has, or its initial sound or letter. But you can’t retrieve it all. The experience is coupled with a strong feeling (this is the frustrating part) that you know the word, and that it is hovering on the edges of your thought.

When you do eventually remember it, the experience is often as erratic and abrupt as the initial failure — typically it pops up sometime later, when you have stopped searching for it.

Another characteristic of TOTs is that a similar sounding word keeps blocking the way. There you are, trying to remember Velcro, and all you can think of is helmet. You feel strongly that if you could just stop thinking of helmet, then you’d find the word you’re looking for, but helmet won’t budge.

What causes TOTs?

It has been thought that these interfering words cause the TOTs, but some researchers now believe they’re a consequence rather than a cause. Because you have part of the sounds of the word you’re searching for, your hard-working brain, searching for words that have those sounds, keeps coming up with the same, wrong, words.

A recent study by Dr Lori James of the University of California and Dr Deborah Burke of Pomona College suggests a different cause.

How are words held in memory? A lot of emphasis has been placed on the importance of semantic information — the meaning of words. But it may be that the sound of a word is as important as its meaning.

Words contain several types of information, including:

  • semantic information (meaning),
  • lexical information (letters), and
  • phonological information (sound).

These types of information are held in separate parts of memory. They are connected of course, so that when, for example, you read Velcro, the letter information triggers the connected sound information and the connected meaning information, telling you how to pronounce the word and what it means.

When you try to think of a word, as opposed to being given it, you generally start with the meaning (“that sticky stuff that has fuzz on one side and tiny hooks on the other”). If the connection between that meaning and the sound information is not strong enough, the sound information won’t be activated strongly enough to allow you to retrieve all of it.

Drs James and Burke think that TOTs occur because of weak connections between the meaning and the sound of a word.

Connections are strengthened when they’re used a lot. They are also stronger when they’ve just been used. If you haven’t used a connection for a while, it will weaken. It may also be that aging weakens connections.

This may explain why the errant word suddenly “pops up”. It may be that you have experienced a similar sound to the target word.

Are TOTs worth worrying about?

TOTs are ranked by older adults as their most annoying memory failure. They do happen more often as you age, and this increase starts as early as the mid-thirties.

While everyone has TOTs, there are some differences in the TOTs experienced by older adults. For example, the most common type of word involved in TOTs at all ages is proper names. But while forgetting proper names and object names becomes more common as we get older, abstract words are actually forgotten less.

The length of time before the missing word is recalled also increases with age. This may be because older people are less likely to actively pursue a missing word, and more inclined to simply relax and think about something else. Older adults are also more likely than younger adults to go completely blank (unable to recall any part of the word’s sound or letters).

Alzheimer’s disease is characterized by word failures. However, normal TOTs tend to involve rarely used words. In Alzheimer’s, people lose very high frequency words, such as fork and spoon.

Why do TOTs increase as we age? Part of the reason may be that most of us experience fewer new and rare words as we get older and stuck in our own particular ruts. It seems that we need a lot of activation of the sound connections to keep them alive. The more we limit our experience to the tried and true, the less opportunity to keep these rarer connections active.

Dr James suggests: "People should keep using language, keep reading, keep doing crosswords. The more you use your language and encounter new words, the better your chances are going to be of maintaining those words, both in comprehension and in production, as you get older."

References: 
  • Burke, D.M., MacKay, D.G., Worthley, J.S. & Wade, E. (1991). On the tip of the tongue: What causes word finding failures in young and older adults. Journal of Memory and Language, 30, 542-579.
  • James, L.E. & Burke, D.M. 2001. Phonological Priming Effects on Word Retrieval and Tip-of-the-Tongue Experiences in Young and Older Adults. Journal of Experimental Psychology: Learning, Memory and Cognition, 26 (6), 1378-1391. Full text available at: http://www.apa.org/journals/xlm/xlm2661378.html
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