semantic memory

Physical activity linked to better memory for names and faces among older adults

  • A small study adds to evidence that walking improves memory in older adults, and indicates that this is particularly helpful for memory tasks the seniors find challenging.

A small study that fitted 29 young adults (18-31) and 31 older adults (55-82) with a device that recorded steps taken and the vigor and speed with which they were made, has found that those older adults with a higher step rate performed better on memory tasks than those who were more sedentary. There was no such effect seen among the younger adults.

Improved memory was found for both visual and episodic memory, and was strongest with the episodic memory task. This required recalling which name went with a person's face — an everyday task that older adults often have difficulty with.

However, the effect on visual memory had more to do with time spent sedentary than step rate. With the face-name task, both time spent sedentary and step rate were significant factors, and both factors had a greater effect than they had on visual memory.

Depression and hypertension were both adjusted for in the analysis.

There was no significant difference in executive function related to physical activity, although previous studies have found an effect. Less surprisingly, there was also no significant effect on verbal memory.

Both findings might be explained in terms of cognitive demand. The evidence suggests that the effect of physical exercise is only seen when the task is sufficiently cognitively demanding. No surprise that verbal memory (which tends to be much less affected by age) didn't meet that challenge, but interestingly, the older adults in this study were also less impaired on executive function than on visual memory. This is unusual, and reminds us that, especially with small studies, you cannot ignore the individual differences.

This general principle may also account for the lack of effect among younger adults. It is interesting to speculate whether physical activity effects would be found if the younger adults were given much more challenging tasks (either by increasing their difficulty, or selecting a group who were less capable).

Step Rate was calculated by total steps taken divided by the total minutes in light, moderate, and vigorous activities, based on the notion that this would provide an independent indicator of physical activity intensity (how briskly one is walking). Sedentary Time was the total minutes spent sedentary.

http://www.eurekalert.org/pub_releases/2015-11/bumc-slp112415.php

Reference: 

[4045] Hayes SM, Alosco ML, Hayes JP, Cadden M, Peterson KM, Allsup K, Forman DE, Sperling RA, Verfaellie M. Physical Activity Is Positively Associated with Episodic Memory in Aging. Journal of the International Neuropsychological Society [Internet]. 2015 ;21(Special Issue 10):780 - 790. Available from: http://journals.cambridge.org/article_S1355617715000910

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Movements and images improve new vocabulary learning

  • Foreign words are learned better when gestures or pictures are used.
  • Imitating symbolic gestures is more beneficial than viewing illustrative pictures.
  • These benefits correlate with activity in specific brain regions.
  • The benefits are only found in translation tasks, not in free recall.

A small study using an artificial language adds to evidence that new vocabulary is learned more easily when the learner uses gestures.

“Vimmish”, the artificial language used in the study, follows similar phonetic rules to Italian. The German-speaking participants were given abstract and concrete nouns to learn over the course of a week. In the first experiment, the 21 subjects heard the words and their translations under one of three conditions:

  • with a video showing a symbolic gesture of the word's meaning, which they imitated
  • with a picture illustrating the word's meaning, which they traced in the air
  • with no gestures or pictures.

On the 8th day, the participants were tested while their brain activity was monitored. The test involved hearing the foreign word, then selecting the correct translation from four written options.

The researchers were interested in learning whether they could predict the learning condition from the brain activity patterns displayed when the participants were tested. They found that the gesture condition and control could be distinguished in two brain regions: a visual area that processes biological motion (part of the right superior temporal sulcus), and the left premotor cortex. Activity in these regions was also significantly correlated with performance. The picture condition and control could be distinguished in a visual area that processes objects (the right anterior lateral occipital cortex). There was a trend for this activity to correlate with performance, but it didn't reach significance.

Paper-and-pencil translation tests two and six months after learning showed that learning with gestures was significantly better than the other conditions. But note that there was no advantage for any condition in a free recall task.

A second experiment compared gesture and pictures in the more common picture scenario — participants only viewed the video or picture; there was no imitation. Unsurprisingly, there was no motor cortex involvement in this scenario: gesture and control conditions were distinguished only by activity in the biological motion part of the right superior temporal sulcus. The correlation of activity in the right anterior LOC with performance in the picture condition this time reached significance. But most importantly, this time the picture condition led to better translation accuracy than the other two conditions.

However, the most significant result is this: when both experiments were evaluated together, the gesture benefit in experiment 1 (when the participant copied the gesture) was greater than the picture benefit in the second experiment.

The findings are in keeping with other evidence that foreign words are learned more easily when multiple senses are involved.

http://www.eurekalert.org/pub_releases/2015-02/m-lwa020415.php

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How your brain chunks ‘moments’ into ‘events’

We talk about memory for ‘events’, but how does the brain decide what an event is? How does it decide what is part of an event and what isn’t? A new study suggests that our brain uses categories it creates based on temporal relationships between people, objects, and actions — i.e., items that tend to—or tend not to—pop up near one another at specific times.

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 TT, Mata R, Wilke A, Samanez-Larkin GR. Mechanisms of Age-Related Decline in Memory Search Across the Adult Life Span. Developmental Psychology. 2013 :No - Pagination Specified.

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Intensive training helps seniors with long-term aphasia

February, 2013

A six-week specific language therapy program not only improved chronic aphasic’s ability to name objects, but produced durable changes in brain activity that continued to bring benefits post-training.

Here’s an encouraging study for all those who think that, because of age or physical damage, they must resign themselves to whatever cognitive impairment or decline they have suffered. In this study, older adults who had suffered from aphasia for a long time nevertheless improved their language function after six weeks of intensive training.

The study involved nine seniors with chronic aphasia and 10 age-matched controls. Those with aphasia were given six weeks of intensive and specific language therapy, after which they showed significantly better performance at naming objects. Brain scans revealed that the training had not only stimulated language circuits, but also integrated the default mode network (the circuits used when our brain is in its ‘resting state’ — i.e., not thinking about anything in particular), producing brain activity that was similar to that of the healthy controls.

Moreover, these new circuits continued to be active after training, with participants continuing to improve.

Previous research has implicated abnormal functioning of the default mode network in other cognitive disorders.

Although it didn’t reach significance, there was a trend suggesting that the level of integration of the default mode network prior to therapy predicted the outcome of the training.

The findings are especially relevant to the many seniors who no longer receive treatment for stroke damage they may have had for many years. They also add to the growing evidence for the importance of the default mode network. Changes in the integration of the default mode network with other circuits have also been implicated in age-related cognitive decline and Alzheimer’s.

Interestingly, some research suggests that meditation may help improve the coherence of brainwaves that overlap the default mode network. Meditation, already shown to be helpful for improving concentration and focus, may be of greater benefit for fighting age-related cognitive decline than we realize!

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Simple semantic task reveals early cognitive problems in older adults

January, 2013

A study finds early semantic problems in those with MCI, correlating with a reduced capacity to carry out everyday tasks.

A small study shows how those on the road to Alzheimer’s show early semantic problems long before memory problems arise, and that such problems can affect daily life.

The study compared 25 patients with amnestic MCI, 27 patients with mild-to-moderate Alzheimer's and 70 cognitively fit older adults (aged 55-90), on a non-verbal task involving size differences (for example, “What is bigger: a key or a house?”; “What is bigger: a key or an ant?”). The comparisons were presented in three different ways: as words; as images reflecting real-world differences; as incongruent images (e.g., a big ant and a small house).

Both those with MCI and those with AD were significantly less accurate, and significantly slower, in all three conditions compared to healthy controls, and they had disproportionately more difficulty on those comparisons where the size distance was smaller. But MCI and AD patients experienced their biggest problems when the images were incongruent – the ant bigger than the house. Those with MCI performed at a level between that of healthy controls and those with AD.

This suggests that perceptual information is having undue influence in a judgment task that requires conceptual knowledge.

Because semantic memory is organized according to relatedness, and because this sort of basic information has been acquired a long time ago, this simple test is quite a good way to test semantic knowledge. As previous research has indicated, the problem doesn’t seem to be a memory (retrieval) one, but one reflecting an actual loss or corruption of semantic knowledge. But perhaps, rather than a loss of data, it reflects a failure of selective attention/inhibition — an inability to inhibit immediate perceptual information in favor of more relevant conceptual information.

How much does this matter? Poor performance on the semantic distance task correlated with impaired ability to perform everyday tasks, accounting (together with delayed recall) for some 35% of the variance in scores on this task — while other cognitive abilities such as processing speed, executive function, verbal fluency, naming, did not have a significant effect. Everyday functional capacity was assessed using a short form of the UCSD Skills Performance Assessment scale (a tool generally used to identify everyday problems in patients with schizophrenia), which presents scenarios such as planning a trip to the beach, determining a route, dialing a telephone number, and writing a check.

The finding indicates that semantic memory problems are starting to occur early in the deterioration, and may be affecting general cognitive decline. However, if the problems reflect an access difficulty rather than data loss, it may be possible to strengthen these semantic processing connections through training — and thus improve general cognitive processing (and ability to perform everyday tasks).

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Children learn iconic signs more easily and quickly

December, 2012

A study of deaf toddlers suggests that we can support children’s acquisition of language by providing physical links to words, through the use of gestures, facial expressions, and tone.

The relative ease with which children acquire language has produced much debate and theory, mirroring the similar quantity of debate and theory over how we evolved language. One theory of language evolution is that it began with gesture. A recent study looking at how deaf children learn sign language might perhaps be taken as partial support for this theory, and may also have wider implications for how children acquire language and how we can best support them.

The study, involving 31 deaf toddlers, looked at 89 specific signs understood and produced by the children. It was found that both younger (11-20 months) and older (21-30 months) toddlers understood and produced more signs that were iconic than signs that were less iconic. This benefit seemed to be greater for the older toddlers, supporting the idea that a certain amount of experience and/or cognitive development is needed to make the link between action and meaning.

Surprisingly, the benefits of iconicity did not seem to depend on how familiar, phonologically complex, or imageable the words were.

In contrast to spoken language, a high proportion of signs are iconic, that is, related to the concept being expressed (such as, bringing the hand to the mouth to indicate ‘eat’). Nevertheless, if iconicity is important in sign language, it is surely also important in spoken languages. This is supported by the role of gesture in speech.

The researchers suggest that iconic links between our perceptual-motor experience of the world and the form of a sign may provide an imitation-based mechanism that supports early sign acquisition, and that this might also apply to spoken language — with gestures, tone of voice, inflection, and facial expression helping make the link between words and their meanings less arbitrary.

This suggests that we can support children’s acquisition of language by providing and emphasizing such ‘scaffolding’.

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Growing the brain with a new language

November, 2012

A new study adds to the growing evidence for the cognitive benefits of learning a new language, and hints at why some people might be better at this than others.

A small Swedish brain imaging study adds to the evidence for the cognitive benefits of learning a new language by investigating the brain changes in students undergoing a highly intensive language course.

The study involved an unusual group: conscripts in the Swedish Armed Forces Interpreter Academy. These young people, selected for their talent for languages, undergo an intensive course to allow them to learn a completely novel language (Egyptian Arabic, Russian or Dari) fluently within ten months. This requires them to acquire new vocabulary at a rate of 300-500 words every week.

Brain scans were taken of 14 right-handed volunteers from this group (6 women; 8 men), and 17 controls that were matched for age, years of education, intelligence, and emotional stability. The controls were medical and cognitive science students. The scans were taken before the start of the course/semester, and three months later.

The brain scans revealed that the language students showed significantly greater changes in several specific regions. These regions included three areas in the left hemisphere: the dorsal middle frontal gyrus, the inferior frontal gyrus, and the superior temporal gyrus. These regions all grew significantly. There was also some, more selective and smaller, growth in the middle frontal gyrus and inferior frontal gyrus in the right hemisphere. The hippocampus also grew significantly more for the interpreters compared to the controls, and this effect was greater in the right hippocampus.

Among the interpreters, language proficiency was related to increases in the right hippocampus and left superior temporal gyrus. Increases in the left middle frontal gyrus were related to teacher ratings of effort — those who put in the greatest effort (regardless of result) showed the greatest increase in this area.

In other words, both learning, and the effort put into learning, had different effects on brain development.

The main point, however, is that language learning in particular is having this effect. Bear in mind that the medical and cognitive science students are also presumably putting in similar levels of effort into their studies, and yet no such significant brain growth was observed.

Of course, there is no denying that the level of intensity with which the interpreters are acquiring a new language is extremely unusual, and it cannot be ruled out that it is this intensity, rather than the particular subject matter, that is crucial for this brain growth.

Neither can it be ruled out that the differences between the groups are rooted in the individuals selected for the interpreter group. The young people chosen for the intensive training at the interpreter academy were chosen on the basis of their talent for languages. Although brain scans showed no differences between the groups at baseline, we cannot rule out the possibility that such intensive training only benefited them because they possessed this potential for growth.

A final caveat is that the soldiers all underwent basic military training before beginning the course — three months of intense physical exercise. Physical exercise is, of course, usually very beneficial for the brain.

Nevertheless, we must give due weight to the fact that the brain scans of the two groups were comparable at baseline, and the changes discussed occurred specifically during this three-month learning period. Moreover, there is growing evidence that learning a new language is indeed ‘special’, if only because it involves such a complex network of processes and brain regions.

Given that people vary in their ‘talent’ for foreign language learning, and that learning a new language does tend to become harder as we get older, it is worth noting the link between growth of the hippocampus and superior temporal gyrus and language proficiency. The STG is involved in acoustic-phonetic processes, while the hippocampus is presumably vital for the encoding of new words into long-term memory.

Interestingly, previous research with children has suggested that the ability to learn new words is greatly affected by working memory span — specifically, by how much information they can hold in that part of working memory called phonological short-term memory. While this is less important for adults learning another language, it remains important for one particular category of new words: words that have no ready association to known words. Given the languages being studied by these Swedish interpreters, it seems likely that much if not all of their new vocabulary would fall into this category.

I wonder if the link with STG is more significant in this study, because the languages are so different from the students’ native language? I also wonder if, and to what extent, you might be able to improve your phonological short-term memory with this sort of intensive practice.

In this regard, it’s worth noting that a previous study found that language proficiency correlated with growth in the left inferior frontal gyrus in a group of English-speaking exchange students learning German in Switzerland. Is this difference because the training was less intensive? because the students had prior knowledge of German? because German and English are closely related in vocabulary? (I’m picking the last.)

The researchers point out that hippocampal plasticity might also be a critical factor in determining an individual’s facility for learning a new language. Such plasticity does, of course, tend to erode with age — but this can be largely counteracted if you keep your hippocampus limber (as it were).

All these are interesting speculations, but the main point is clear: the findings add to the growing evidence that bilingualism and foreign language learning have particular benefits for the brain, and for protecting against cognitive decline.

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Regular cocoa drinking helps those with MCI

September, 2012

Daily consumption of a high level of cocoa was found to improve cognitive scores, insulin resistance and blood pressure, in older adults with mild cognitive impairment.

Back in 2009, I reported briefly on a large Norwegian study that found that older adults who consumed chocolate, wine, and tea performed significantly better on cognitive tests. The association was assumed to be linked to the flavanols in these products. A new study confirms this finding, and extends it to older adults with mild cognitive impairment.

The study involved 90 older adults with MCI, who consumed either 990 milligrams, 520 mg, or 45 mg of a dairy-based cocoa drink daily for eight weeks. Their diet was restricted to eliminate other sources of flavanols (such as tea, red wine, apples and grapes).

Cognitive assessment at the end of this period revealed that, although scores on the MMSE were similar across all groups, those consuming higher levels of flavanol cocoa took significantly less time to complete Trail Making Tests A and B, and scored significantly higher on the verbal fluency test. Insulin resistance and blood pressure was also lower.

Those with the highest levels of flavanols did better than those on intermediate levels on the cognitive tests. Both did better than those on the lowest levels.

Changes in insulin resistance explained part, but not all, of the cognitive improvement.

One caveat: the group were generally in good health without known cardiovascular disease — thus, not completely representative of all those with MCI.

 

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Second language processing differs for negative words

June, 2012

A study involving Chinese-English bilinguals shows how words with negative emotional connotations don’t automatically access native translations, while those with positive or neutral emotions do.

Here’s an intriguing study for those interested in how language affects how we think. It’s also of interest to those who speak more than one language or are interested in learning another language, because it deals with the long-debated question as to whether bilinguals working in their non-native language automatically access the native-language representations in long-term memory, or whether they can ‘switch off’ their native language and use only the target language memory codes.

The study follows on from an earlier study by the same researchers that indicated, through the demonstration of hidden priming effects, that bilinguals subconsciously access their first language when reading in their second language. In this new study, 45 university students (15 native English speakers, 15 native Chinese speakers, and 15 Chinese-English bilinguals) were shown two blocks of 90 word pairs. The pairs could have positive emotional value (e.g., honesty-program), negative valence (failure-poet), or neutral valence (aim-carpenter); could be semantically related (virus-bacteria; love-rose) or unrelated (weather-gender). The English or Chinese words were flashed on the screen one at a time, with a brief interval between the first and second word. The students had to indicate whether the second word was related in meaning to the first, and their brain activity was monitored.

The English and Chinese speakers acted as controls — it was the bilinguals, of course, who were the real interest. Some of the English word pairs shared a sound in the Chinese translation. If the Chinese words were automatically activated, therefore, the sound repetition would have a priming effect.

This is indeed what was found (confirming the earlier finding and supporting the idea that native language translations are automatically activated) — but here’s the interesting thing: the priming effect occurred only for positive and neutral words. It did not occur when the bilinguals saw negative words such as war, discomfort, inconvenience, and unfortunate.

The finding, which surprised the researchers, is nonetheless consistent with previous evidence that anger, swearing or discussing intimate feelings has more power in a speaker's native language. Parents, too, tend to speak to their infants in their native tongue. Emotion, it seems, is more strongly linked to our first language.

It’s traditionally thought that second language processing is fundamentally determined by the age of acquisition and the level of proficiency. The differences in emotional resonance have been, naturally enough, attributed to the native language being acquired first. This finding suggests the story is a little more complicated.

The researchers theorize that they have touched on the mechanism by which emotion controls our fundamental thought processes. They suggest that the brain is trying to protect us by minimizing the effect of distressing or disturbing emotional content, by shutting down the unconscious access to the native language (in which the negative words would be more strongly felt).

A few more technical details for those interested:

The Chinese controls demonstrated longer reaction times than the English controls, which suggests (given that 60% of the Chinese word pairs had overt sound repetitions but no semantic relatedness) that this conjunction made the task substantially more difficult. The bilinguals, however, had reaction times comparable to the English controls. The Chinese controls showed no effect of emotional valence, but did show priming effects of the overt sound manipulation that were equal for all emotion conditions.

The native Chinese speakers had recently arrived in Britain to attend an English course. Bilinguals had been exposed to English since the age of 12 and had lived in Britain for an average of 20.5 months.

Reference: 

[2969] Wu YJ, Thierry G. How Reading in a Second Language Protects Your Heart. The Journal of Neuroscience [Internet]. 2012 ;32(19):6485 - 6489. Available from: http://www.jneurosci.org/content/32/19/6485

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