similarity

Improve learning with co-occurring novelty

  • An animal study shows that following learning with a novel experience makes the learning stronger.
  • A human study shows that giving information positive associations improves your memory for future experiences with similar information.

We know that the neurotransmitter dopamine is involved in making strong memories. Now a mouse study helps us get more specific — and suggests how we can help ourselves learn.

The study, involving 120 mice, found that mice tasked with remembering where food had been hidden did better if they had been given a novel experience (exploring an unfamiliar floor surface) 30 minutes after being trained to remember the food location.

This memory improvement also occurred when the novel experience was replaced by the selective activation of dopamine-carrying neurons in the locus coeruleus that go to the hippocampus. The locus coeruleus is located in the brain stem and involved in several functions that affect emotion, anxiety levels, sleep patterns, and memory. The dopamine-carrying neurons in the locus coeruleus appear to be especially sensitive to environmental novelty.

In other words, if we’re given attention-grabbing experiences that trigger these LC neurons carrying dopamine to the hippocampus at around the time of learning, our memories will be stronger.

Now we already know that emotion helps memory, but what this new study tells us is that, as witness to the mice simply being given a new environment to explore, these dopamine-triggering experiences don’t have to be dramatic. It’s suggested that it could be as simple as playing a new video game during a quick break while studying for an exam, or playing tennis right after trying to memorize a big speech.

Remember that we’re designed to respond to novelty, to pay it more attention — and, it seems, that attention is extended to more mundane events that occur closely in time.

Emotionally positive situations boost memory for similar future events

In a similar vein, a human study has found that the benefits of reward extend forward in time.

In the study, volunteers were shown images from two categories (objects and animals), and were financially rewarded for one of these categories. As expected, they remembered images associated with a reward better. In a second session, however, they were shown new images of animals and objects without any reward. Participants still remembered the previously positively-associated category better.

Now, this doesn’t seem in any way surprising, but the interesting thing is that this benefit wasn’t seen immediately, but only after 24 hours — that is, after participants had slept and consolidated the learning.

Previous research has shown similar results when semantically related information has been paired with negative, that is, aversive stimuli.

https://www.eurekalert.org/pub_releases/2016-09/usmc-rim090716.php

http://www.eurekalert.org/pub_releases/2016-06/ibri-eps061516.php

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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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Cut ‘visual clutter’ to help MCI & Alzheimer’s

October, 2012

A small study shows that those with MCI perform poorly on a visual discrimination task under high interference conditions, suggesting that reducing interference may improve cognitive performance.

Memory problems in those with mild cognitive impairment may begin with problems in visual discrimination and vulnerability to interference — a hopeful discovery in that interventions to improve discriminability and reduce interference may have a flow-on effect to cognition.

The study compared the performance on a complex object discrimination task of 7 patients diagnosed with amnestic MCI, 10 older adults considered to be at risk for MCI (because of their scores on a cognitive test), and 19 age-matched controls. The task involved the side-by-side comparison of images of objects, with participants required to say, within 15 seconds, whether the two objects were the same or different.

In the high-interference condition, the objects were blob-like and presented as black and white line-drawings, with some comparison pairs identical, while others only varied slightly in either shape or fill pattern. Objects were rotated to discourage a simple feature-matching strategy. In the low-interference condition, these line-drawings were interspersed with color photos of everyday objects, for which discriminability was dramatically easier. The two conditions were interspersed by a short break, with the low interference condition run in two blocks, before and after the high interference condition.

A control task, in which the participants compared two squares that could vary in size, was run at the end.

The study found that those with MCI, as well as those at risk of MCI, performed significantly worse than the control group in the high-interference condition. There was no difference in performance between those with MCI and those at risk of MCI. Neither group was impaired in the first low-interference condition, although the at-risk group did show significant impairment in the second low-interference condition. It may be that they had trouble recovering from the high-interference experience. However, the degree of impairment was much less than it was in the high-interference condition. It’s also worth noting that the performance on this second low-interference task was, for all groups, notably higher than it was on the first low-interference task.

There was no difference between any of the groups on the control task, indicating that fatigue wasn’t a factor.

The interference task was specifically chosen as one that involved the perirhinal cortex, but not the hippocampus. The task requires the conjunction of features — that is, you need to be able to see the object as a whole (‘feature binding’), not simply match individual features. The control task, which required only the discrimination of a single feature, shows that MCI doesn’t interfere with this ability.

I do note that the amount of individual variability on the interference tasks was noticeably greater in the MCI group than the others. The MCI group was of course smaller than the other groups, but variability wasn’t any greater for this group in the control task. Presumably this variability reflects progression of the impairment, but it would be interesting to test this with a larger sample, and map performance on this task against other cognitive tasks.

Recent research has suggested that the perirhinal cortex may provide protection from visual interference by inhibiting lower-level features. The perirhinal cortex is strongly connected to the hippocampus and entorhinal cortex, two brain regions known to be affected very early in MCI and Alzheimer’s.

The findings are also consistent with other evidence that damage to the medial temporal lobe may impair memory by increasing vulnerability to interference. For example, one study has found that story recall was greatly improved in patients with MCI if they rested quietly in a dark room after hearing the story, rather than being occupied in other tasks.

There may be a working memory component to all this as well. Comparison of two objects does require shifting attention back and forth. This, however, is separate to what the researchers see as primary: a perceptual deficit.

All of this suggests that reducing “visual clutter” could help MCI patients with everyday tasks. For example, buttons on a telephone tend to be the same size and color, with the only difference lying in the numbers themselves. Perhaps those with MCI or early Alzheimer’s would be assisted by a phone with varying sized buttons and different colors.

The finding also raises the question: to what extent is the difficulty Alzheimer’s patients often have in recognizing a loved one’s face a discrimination problem rather than a memory problem?

Finally, the performance of the at-risk group — people who had no subjective concerns about their memory, but who scored below 26 on the MoCA (Montreal Cognitive Assessment — a brief screening tool for MCI) — suggests that vulnerability to visual interference is an early marker of cognitive impairment that may be useful in diagnosis. It’s worth noting that, across all groups, MoCA scores predicted performance on the high-interference task, but not on any of the other tasks.

So how much cognitive impairment rests on problems with interference?

Reference: 

Newsome, R. N., Duarte, A., & Barense, M. D. (2012). Reducing Perceptual Interference Improves Visual Discrimination in Mild Cognitive Impairment : Implications for a Model of Perirhinal Cortex Function, Hippocampus, 22, 1990–1999. doi:10.1002/hipo.22071

Della Sala S, Cowan N, Beschin N, Perini M. 2005. Just lying there, remembering: Improving recall of prose in amnesic patients with mild cognitive impairment by minimising interference. Memory, 13, 435–440.

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Each memory experience biases how you approach the next one

September, 2012

A new study provides evidence that our decision to encode information as new or try and retrieve it from long-term memory is affected by how we treated the last bit of information processed.

Our life-experiences contain a wealth of new and old information. The relative proportions of these change, of course, as we age. But how do we know whether we should be encoding new information or retrieving old information? It’s easy if the information is readily accessible, but what if it’s not? Bear in mind that (especially as we get older) most information / experiences we meet share some similarity to information we already have.

This question is made even more meaningful when you consider that it is the same brain region — the hippocampus — that’s involved in both encoding and retrieval, and these two processes depend (it is thought) on two quite opposite processes. While encoding is thought to rely on pattern separation (looking for differences), retrieval is thought to depend on pattern completion.

A recent study looked at what happens in the brain when people rapidly switch between encoding new objects and retrieving recently presented ones. Participants were shown 676 pictures of objects and asked to identify each one as being shown for the first time (‘new’), being repeated (‘old’), or as a modified version of something shown earlier (‘similar’). Recognizing the similar items as similar was the question of interest, as these items contain both old and new information and so the brain’s choice between encoding and retrieval is more difficult.

What they found was that participants were more likely to recognize similar items as similar (rather than old) if they had viewed a new item on the preceding trial. In other words, the experience of a new item primed them to notice novelty. Or to put it in another way: context biases the hippocampus toward either pattern completion or pattern separation.

This was supported by a further experiment, in which participants were shown both the object pictures, and also learned associations between faces and scenes. Critically, each scene was associated with two different faces. In the next learning phase, participants were taught a new scene association for one face from each pair. Each face-scene learning trial was preceded by an object recognition trial (new and old objects were shown and participants had to identify them as old or new) — critically, either a new or old object was consistently placed before a specific face-scene association. In the final test phase, participants were tested on the new face-scene associations they had just learned, as well as the indirect associations they had not been taught (that is, between the face of each pair that had not been presented during the preceding phase, and the scene associated with its partnered face).

What this found was that participants were more likely to pair indirectly related faces if those faces had been consistently preceded by old objects, rather than new ones. Moreover, they did so more quickly when the faces had been preceded by old objects rather than new ones.

This was interpreted as indicating that the preceding experience affects how well related information is integrated during encoding.

What all this suggests is that the memory activities you’ve just engaged in bias your brain toward the same sort of activities — so whether or not you notice changes to a café or instead nostalgically recall a previous meal, may depend on whether you noticed anyone you knew as you walked down the street!

An interesting speculation by the researchers is that such a memory bias (which only lasts a very brief time) might be an adaptive mechanism, reflecting the usefulness of being more sensitive to changes in new environments and less sensitive to irregularities in familiar environments.

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Extra-large letter spacing improves reading in dyslexia

July, 2012

Increasing the spacing between letters has been found to improve reading accuracy and speed in dyslexic children, with poorest readers benefiting most.

It’s generally agreed among researchers that the most efficient intervention for dyslexia is to get the child reading more — the challenge is to find ways that enable that. Training programs typically target specific component skills, which are all well and good but leave the essential problem untouched: the children still need to read more. A new study shows that a very simple manipulation substantially improves reading in a large, unselected group of dyslexic children.

The study involved 74 French and Italian children — the two groups enabling researchers to compare a transparent writing system (Italian) with a relatively opaque one (French). The children had to read 24 short, meaningful, but unrelated, sentences. The text was written in Times New Roman 14 point. Standard interletter spacing was compared to spacing increased by 2.5 points. Space between words and lines was also increased commensurately. Each child read the same sentences in two sessions, two weeks apart. In one session, standard spacing was used, and in the other, increased spacing. Order of the sessions was of course randomly assigned.

The idea behind this is that dyslexic readers seem to be particularly affected by crowding. Crowding — interference from flanking letters — mostly affects peripheral vision in normal adult readers, but has been shown to be a factor in central vision in school-aged children. Standard letter spacing appears to be optimal for skilled adult readers.

The study found that increased spacing improved accuracy in reading the text by a factor of two. Moreover, this group effect conceals substantial individual differences. Those who had the most difficulties with the text benefitted the most from the extra spacing.

Reading speed also increased. In this case, despite the 2-week interval, there was an order effect: those who read the normal text first were faster on the 2nd (spaced) reading, while those who read the spaced text first read the 2nd (normal) text at the same speed. Analysis that removed the effects of repetition found that spacing produced a speed improvement of about 0.3 syllables a second, which corresponds to the average improvement across an entire school year for Italian dyslexic children.

There was no difference between the Italian and French children, indicating that this manipulation works in both transparent (in which letters and sounds match) and opaque writing systems (like English).

Subsequent comparison of 30 of the Italian children (mean age 11) with younger normally-developing children (mean age 8) matched for reading level and IQ found that spacing benefited only the dyslexic children.

A further experiment involving some of the Italian dyslexic children compared the spaced condition with normal text that had the same line spacing as the spaced text. This confirmed that it was the letter spacing that was critical.

These findings point to a very simple way of giving dyslexic children the practice they need in reading without any training. It is not suggested that it replaces specific-skill training, but rather augments it.

Reference: 

[3017] Zorzi M, Barbiero C, Facoetti A, Lonciari I, Carrozzi M, Montico M, Bravar L, George F, Pech-Georgel C, Ziegler JC. Extra-large letter spacing improves reading in dyslexia. Proceedings of the National Academy of Sciences [Internet]. 2012 ;109(28):11455 - 11459. Available from: http://www.pnas.org/content/109/28/11455

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Ability to remember memories' origin develops slowly

October, 2011

A study comparing the brains of children, adolescents, and young adults has found that the ability to remember the origin of memories is slow to mature. As with older adults, impaired source memory increases susceptibility to false memories.

In the study, 18 children (aged 7-8), 20 adolescents (13-14), and 20 young adults (20-29) were shown pictures and asked to decide whether it was a new picture or one they had seen earlier. Some of the pictures were of known objects and others were fanciful figures (this was in order to measure the effects of novelty in general). After a 10-minute break, they resumed the task — with the twist that any pictures that had appeared in the first session should be judged “new” if that was the first appearance in the second session. EEG measurements (event-related potentials — ERPs) were taken during the sessions.

ERPs at the onset of a test stimulus (each picture) are different for new and old (repeated) stimuli. Previous studies have established various old/new effects that reflect item and source memory in adults. In the case of item memory, recognition is thought to be based on two processes — familiarity and recollection — which are reflected in ERPs of different timings and location (familiarity: mid-frontal at 300-500 msec; recollection: parietal at 400-70 msec). Familiarity is seen as a fast assessment of similarity, while recollection varies according to the amount of retrieved information.

Source memory appears to require control processes that involve the prefrontal cortex. Given that this region is the slowest to mature, it would not be surprising if source memory is a problematic memory task for the young. And indeed, previous research has found that children do have particular difficulty in sourcing memories when the sources are highly similar.

In the present study, children performed more poorly than adolescents and adults on both item memory and source memory. Adolescents performed more poorly than adults on item memory but not on source memory. Children performed more poorly on source memory than item memory, but adolescents and adults showed no difference between the two tasks.

All groups responded faster to new items than old, and ERP responses to general novelty were similar across the groups — although children showed a left-frontal focus that may reflect the transition from analytic to a more holistic processing approach.

ERPs to old items, however, showed a difference: for adults, they were especially pronounced at frontal sites, and occurred at around 350-450 msec; for children and adolescents they were most pronounced at posterior sites, occurring at 600-800 msec for children and 400-600 msec for adolescents. Only adults showed the early midfrontal response that is assumed to reflect familiarity processing. On the other hand, the late old/new effect occurring at parietal sites and thought to reflect recollection, was similar across all age groups. The early old/new effect seen in children and adolescents at central and parietal regions is thought to reflect early recollection.

In other words, only adults showed the brain responses typical of familiarity as well as recollection. Now, some research has found evidence of familiarity processing in children, so this shouldn’t be taken as proof against familiarity processing in the young. What seems most likely is that children are less likely to use such processing. Clearly the next step is to find out the factors that affect this.

Another interesting point is the early recollective response shown by children and adolescents. It’s speculated that these groups may have used more retrieval cues — conceptual as well as perceptual — that facilitated recollection. I’m reminded of a couple of studies I reported on some years ago, that found that young children were better than adults on a recognition task in some circumstances — because children were using a similarity-based process and adults a categorization-based one. In these cases, it had more to do with knowledge than development.

It’s also worth noting that, in adults, the recollective response was accentuated in the right-frontal area. This suggests that recollection was overlapping with post-retrieval monitoring. It’s speculated that adults’ greater use of familiarity produces a greater need for monitoring, because of the greater uncertainty.

What all this suggests is that preadolescent children are less able to strategically recollect source information, and that strategic recollection undergoes an important step in early adolescence that is probably related to improvements in cognitive control. But this process is still being refined in adolescents, in particular as regards monitoring and coping with uncertainty.

Interestingly, source memory is also one of the areas affected early in old age.

Failure to remember the source of a memory has many practical implications, in particular in the way it renders people more vulnerable to false memories.

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Why it gets harder to remember as we get older

June, 2011

A new study finds that older adults have more difficulty in recognizing new information as ‘new’, and this is linked to degradation of the path leading into the hippocampus.

As we get older, when we suffer memory problems, we often laughingly talk about our brain being ‘full up’, with no room for more information. A new study suggests that in some sense (but not the direct one!) that’s true.

To make new memories, we need to recognize that they are new memories. That means we need to be able to distinguish between events, or objects, or people. We need to distinguish between them and representations already in our database.

We are all familiar with the experience of wondering if we’ve done something. Is it that we remember ourselves doing it today, or are we remembering a previous occasion? We go looking for the car in the wrong place because the memory of an earlier occasion has taken precedence over today’s event. As we age, we do get much more of this interference from older memories.

In a new study, the brains of 40 college students and older adults (60-80) were scanned while they viewed pictures of everyday objects and classified them as either "indoor" or "outdoor." Some of the pictures were similar but not identical, and others were very different. It was found that while the hippocampus of young students treated all the similar pictures as new, the hippocampus of older adults had more difficulty with this, requiring much more distinctiveness for a picture to be classified as new.

Later, the participants were presented with completely new pictures to classify, and then, only a few minutes later, shown another set of pictures and asked whether each item was "old," "new" or "similar." Older adults tended to have fewer 'similar' responses and more 'old' responses instead, indicating that they could not distinguish between similar items.

The inability to recognize information as "similar" to something seen recently is associated with “representational rigidity” in two areas of the hippocampus: the dentate gyrus and CA3 region. The brain scans from this study confirm this, and find that this rigidity is associated with changes in the dendrites of neurons in the dentate/CA3 areas, and impaired integrity of the perforant pathway — the main input path into the hippocampus, from the entorhinal cortex. The more degraded the pathway, the less likely the hippocampus is to store similar memories as distinct from old memories.

Apart from helping us understand the mechanisms of age-related cognitive decline, the findings also have implications for the treatment of Alzheimer’s. The hippocampus is one of the first brain regions to be affected by the disease. The researchers plan to conduct clinical trials in early Alzheimer's disease patients to investigate the effect of a drug on hippocampal function and pathway integrity.

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