aging

Site of plaque buildup matters

Analysis of brain scans and cognitive scores of 64 older adults from the NIA's Baltimore Longitudinal Study of Aging (average age 76) has found that, between the most cognitively stable and the most declining (over a 12-year period), there was no significant difference in the total amount of amyloid in the brain, but there was a significant difference in the location of amyloid accumulation.

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Memory complaints linked to higher risk of MCI & dementia

Data from 6257 older adults (aged 55-90) evaluated from 2005-2012 has revealed that concerns about memory should be taken seriously, with subjective complaints associated with a doubled risk of developing mild cognitive impairment or dementia, and subjective complaints supported by a loved one being associated with a fourfold risk. Complaints by a loved one alone were also associated with a doubled risk.

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Distinguishing normal cognitive decline from more serious disorders

Data from two longitudinal studies of older adults (a nationally representative sample of older adults, and the Alzheimer’s Disease Neuroimaging Initiative) has found that a brief cognitive test can distinguish memory decline associated with healthy aging from more serious memory disorders, years before obvious symptoms show up.

Moreover, the data challenge the idea that memory continues to decline through old age: after excluding the cognitively impaired, there was no evidence of further memory declines after the age of 69.

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Tracking preclinical Alzheimer's progression

New research supports the classification system for preclinical Alzheimer’s proposed two years ago. The classification system divides preclinical Alzheimer's into three stages:

Stage 1: Levels of amyloid beta begin to decrease in the spinal fluid. This indicates that the substance is beginning to form plaques in the brain.

Stage 2: Levels of tau protein start to increase in the spinal fluid, indicating that brain cells are beginning to die. Amyloid beta levels are still abnormal and may continue to fall.

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Less cognitive decline in Danish nonagenarians

A large Danish study comparing two groups of nonagenarians born 10 years apart has found that not only were people born in 1915 nearly a third (32%) more likely to reach the age of 95 than those in the 1905 cohort, but members of the group born in 1915 performed significantly better on tests of cognitive ability and activities of daily living. Additionally, significantly more members of the later cohort scored maximally on the MMSE (23% vs 13% of the earlier cohort).

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Common drugs that can cause memory problems in older adults

A large study, involving 3,690 older adults, has found that drugs with strong anticholinergic effects cause memory and cognitive impairment when taken continuously for a mere two months. Moreover, taking multiple drugs with weaker anticholinergic effects, such as many common over-the-counter digestive aids, affected cognition after 90 days’ continuous use. In both these cases, the risk of cognitive impairment doubled (approximately).

06/2013

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It’s not the noise in the brain; it’s the noise in the input

A new study has found that errors in perceptual decisions occurred only when there was confused sensory input, not because of any ‘noise’ or randomness in the cognitive processing. The finding, if replicated across broader contexts, will change some of our fundamental assumptions about how the brain works.

05/2013

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Forgetfulness in old age may be related to changes in retrieval strategy

April, 2013

A study of younger and older adults indicates that memory search tends to decline with age because, with reduced cognitive control, seniors’ minds tend to ‘flit’ too quickly from one information cluster to another.

Evidence is accumulating that age-related cognitive decline is rooted in three related factors: processing speed slows down (because of myelin degradation); the ability to inhibit distractions becomes impaired; working memory capacity is reduced.

A new study adds to this evidence by looking at one particular aspect of age-related cognitive decline: memory search.

The study put 185 adults aged 29-99 (average age 67) through three cognitive tests: a vocabulary test, digit span (a working memory test), and the animal fluency test, in which you name as many animals as you can in one minute.

Typically, in the animal fluency test, people move through semantic categories such as ‘pets’, ‘big cats’, and so on. The best performers are those who move from category to category with optimal timing — i.e., at the point where the category has been sufficiently exhausted that efforts would be better spent on a new one.

Participants recalled on average 17 animal names, with a range from 5 to 33. While there was a decline with age, it wasn’t particularly marked until the 80s (an average of 18.3 for those in their 30s, 17.5 for those in their 60s, 16.5 for the 70s, 12.8 for the 80s, and 10 for the 90s). Digit span did show a decline, but it was not significant (from 17.5 down to 15.3), while vocabulary (consistent with previous research) showed no decline with age.

But all this is by the by — the nub of the experiment was to discover how individuals were searching their memory. This required a quite complicated analysis, which I will not go into, except to mention two important distinctions. The first is between:

  • global context cue: activates each item in the active category according to how strong it is (how frequently it has been recalled in the past);
  • local context cue: activates each item in relation to its semantic similarity to the previous item recalled.

A further distinction was made between static and dynamic processes: in dynamic models, it is assumed the user switches between local and global search. This, it is further assumed, is because memory is ‘patchy’ – that is, information is represented in clusters. Within a cluster, we use local cues, but to move from one cluster to another, we use global cues.

The point of all this was to determine whether age-related decline in memory search has to do with:

  • Reduced processing speed,
  • Persisting too long on categories, or
  • Inability to maintain focus on local cues (this would relate it back to the inhibition deficit).

By modeling the exact recall patterns, the researchers ascertained that the recall process is indeed dynamic, although the points of transition are not clearly understood. The number of transitions from one cluster to another was negatively correlated with age; it was also strongly positively correlated with performance (number of items recalled). Digit span, assumed to measure ‘cognitive control’, was also negatively correlated with number of transitions, but, as I said, was not significantly correlated with age.

In other words, it appears that there is a qualitative change with age, that increasing age is correlated with increased switching, and reduced cognitive control is behind this — although it doesn’t explain it all (perhaps because we’re still not able to fully measure cognitive control).

At a practical level, the message is that memory search may become less efficient because, as people age, they tend to change categories too frequently, before they have exhausted their full potential. While this may well be a consequence of reduced cognitive control, it seems likely (to me at least) that making a deliberate effort to fight the tendency to move on too quickly will pay dividends for older adults who want to improve their memory retrieval abilities.

Nor is this restricted to older adults — since age appears to be primarily affecting performance through its effects on cognitive control, it is likely that this applies to those with reduced working memory capacity, of any age.

Reference: 

[3378] Hills, T. T., Mata R., Wilke A., & Samanez-Larkin G. R.
(2013).  Mechanisms of Age-Related Decline in Memory Search Across the Adult Life Span.
Developmental Psychology. No - Pagination Specified.

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Genetic test shows risk of cognitive impairment rather than Alzheimer’s

Analysis of data from 418 older adults (70+) has found that carriers of the ‘Alzheimer’s gene’, APOEe4, were 58% more likely to develop mild cognitive impairment compared to non-carriers. However, ε4 carriers with

04/2013

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Regular exercise throughout life helps keep aging mind sharp

Data from the very large, long-running UK National Child Development Study has revealed that those who exercised at least four times weekly as both a child and an adult performed better on cognitive tests at age 50 than those who exercised two to three times per month or less, and the latter in turn performed better than those who hadn’t regularly exercised at all.

03/2013

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