visual memory

How emotion keeps some memories vivid

September, 2012

Emotionally arousing images that are remembered more vividly were seen more vividly. This may be because the amygdala focuses visual attention rather than more cognitive attention on the image.

We know that emotion affects memory. We know that attention affects perception (see, e.g., Visual perception heightened by meditation training; How mindset can improve vision). Now a new study ties it all together. The study shows that emotionally arousing experiences affect how well we see them, and this in turn affects how vividly we later recall them.

The study used images of positively and negatively arousing scenes and neutral scenes, which were overlaid with varying amounts of “visual noise” (like the ‘snow’ we used to see on old televisions). College students were asked to rate the amount of noise on each picture, relative to a specific image they used as a standard. There were 25 pictures in each category, and three levels of noise (less than standard, equal to standard, and more than standard).

Different groups explored different parameters: color; gray-scale; less noise (10%, 15%, 20% as compared to 35%, 45%, 55%); single exposure (each picture was only presented once, at one of the noise levels).

Regardless of the actual amount of noise, emotionally arousing pictures were consistently rated as significantly less noisy than neutral pictures, indicating that people were seeing them more clearly. This was true in all conditions.

Eye-tracking analysis ruled out the idea that people directed their attention differently for emotionally arousing images, but did show that more eye fixations were associated both with less noisy images and emotionally arousing ones. In other words, people were viewing emotionally important images as if they were less noisy.

One group of 22 students were given a 45-minute spatial working memory task after seeing the images, and then asked to write down all the details they could remember about the pictures they remembered seeing. The amount of detail they recalled was taken to be an indirect measure of vividness.

A second group of 27 students were called back after a week for a recognition test. They were shown 36 new images mixed in with the original 75 images, and asked to rate them as new, familiar, or recollected. They were also asked to rate the vividness of their recollection.

Although, overall, emotionally arousing pictures were not more likely to be remembered than neutral pictures, both experiments found that pictures originally seen as more vivid (less noise) were remembered more vividly and in more detail.

Brain scans from 31 students revealed that the amygdala was more active when looking at images rated as vivid, and this in turn increased activity in the visual cortex and in the posterior insula (which integrates sensations from the body). This suggests that the increased perceptual vividness is not simply a visual phenomenon, but part of a wider sensory activation.

There was another neural response to perceptual vividness: activity in the dorsolateral prefrontal cortex and the posterior parietal cortex was negatively correlated with vividness. This suggests that emotion is not simply increasing our attentional focus, it is instead changing it by reducing effortful attentional and executive processes in favor of more perceptual ones. This, perhaps, gives emotional memories their different ‘flavor’ compared to more neutral memories.

These findings clearly need more exploration before we know exactly what they mean, but the main finding from the study is that the vividness with which we recall some emotional experiences is rooted in the vividness with which we originally perceived it.

The study highlights how emotion can sharpen our attention, building on previous findings that emotional events are more easily detected when visibility is difficult, or attentional demands are high. It is also not inconsistent with a study I reported on last year, which found some information needs no repetition to be remembered because the amygdala decrees it of importance.

I should add, however, that the perceptual effect is not the whole story — the current study found that, although perceptual vividness is part of the reason for memories that are vividly remembered, emotional importance makes its own, independent, contribution. This contribution may occur after the event.

It’s suggested that individual differences in these reactions to emotionally enhanced vividness may underlie an individual’s vulnerability to post-traumatic stress disorder.

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Latest London taxi driver study shows brain changes driven by learning

January, 2012
  • A comparison of the brains of London taxi drivers before and after their lengthy training shows clearly that the increase in hippocampal gray matter develops with training, but this may come at the expense of other brain functions.

The evidence that adult brains could grow new neurons was a game-changer, and has spawned all manner of products to try and stimulate such neurogenesis, to help fight back against age-related cognitive decline and even dementia. An important study in the evidence for the role of experience and training in growing new neurons was Maguire’s celebrated study of London taxi drivers, back in 2000.

The small study, involving 16 male, right-handed taxi drivers with an average experience of 14.3 years (range 1.5 to 42 years), found that the taxi drivers had significantly more grey matter (neurons) in the posterior hippocampus than matched controls, while the controls showed relatively more grey matter in the anterior hippocampus. Overall, these balanced out, so that the volume of the hippocampus as a whole wasn’t different for the two groups. The volume in the right posterior hippocampus correlated with the amount of experience the driver had (the correlation remained after age was accounted for).

The posterior hippocampus is preferentially involved in spatial navigation. The fact that only the right posterior hippocampus showed an experience-linked increase suggests that the right and left posterior hippocampi are involved in spatial navigation in different ways. The decrease in anterior volume suggests that the need to store increasingly detailed spatial maps brings about a reorganization of the hippocampus.

But (although the experience-related correlation is certainly indicative) it could be that those who manage to become licensed taxi drivers in London are those who have some innate advantage, evidenced in a more developed posterior hippocampus. Only around half of those who go through the strenuous training program succeed in qualifying — London taxi drivers are unique in the world for being required to pass through a lengthy training period and pass stringent exams, demonstrating their knowledge of London’s 25,000 streets and their idiosyncratic layout, plus 20,000 landmarks.

In this new study, Maguire and her colleague made a more direct test of this question. 79 trainee taxi drivers and 31 controls took cognitive tests and had their brains scanned at two time points: at the beginning of training, and 3-4 years later. Of the 79 would-be taxi drivers, only 39 qualified, giving the researchers three groups to compare.

There were no differences in cognitive performance or brain scans between the three groups at time 1 (before training). At time 2 however, when the trainees had either passed the test or failed to acquire the Knowledge, those trainees that qualified had significantly more gray matter in the posterior hippocampus than they had had previously. There was no change in those who failed to qualify or in the controls.

Unsurprisingly, both qualified and non-qualified trainees were significantly better at judging the spatial relations between London landmarks than the control group. However, qualified trainees – but not the trainees who failed to qualify – were worse than the other groups at recalling a complex visual figure after 30 minutes (see here for an example of such a figure). Such a finding replicates previous findings of London taxi drivers. In other words, their improvement in spatial memory as it pertains to London seems to have come at a cost.

Interestingly, there was no detectable difference in the structure of the anterior hippocampus, suggesting that these changes develop later, in response to changes in the posterior hippocampus. However, the poorer performance on the complex figure test may be an early sign of changes in the anterior hippocampus that are not yet measurable in a MRI.

The ‘Knowledge’, as it is known, provides a lovely real-world example of expertise. Unlike most other examples of expertise development (e.g. music, chess), it is largely unaffected by childhood experience (there may be some London taxi drivers who began deliberately working on their knowledge of London streets in childhood, but it is surely not common!); it is developed through a training program over a limited time period common to all participants; and its participants are of average IQ and education (average school-leaving age was around 16.7 years for all groups; average verbal IQ was around or just below 100).

So what underlies this development of the posterior hippocampus? If the qualified and non-qualified trainees were comparable in education and IQ, what determined whether a trainee would ‘build up’ his hippocampus and pass the exams? The obvious answer is hard work / dedication, and this is borne out by the fact that, although the two groups were similar in the length of their training period, those who qualified spent significantly more time training every week (an average of 34.5 hours a week vs 16.7 hours). Those who qualified also attended far more tests (an average of 15.6 vs 2.6).

While neurogenesis is probably involved in this growth within the posterior hippocampus, it is also possible that growth reflects increases in the number of connections, or in the number of glia. Most probably (I think), all are involved.

There are two important points to take away from this study. One is its clear demonstration that training can produce measurable changes in a brain region. The other is the indication that this development may come at the expense of other regions (and functions).

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Frequent 'heading' in soccer can lead to brain injury and cognitive impairment

December, 2011

A small study extends the evidence that even mild concussions can cause brain damage, with the finding that frequent heading of the ball in soccer can cause similar damage.

American football has been in the news a lot in recent years, as evidence has accumulated as to the brain damage incurred by professional footballers. But American football is a high-impact sport. Soccer is quite different. And yet the latest research reveals that even something as apparently unexceptional as bouncing a ball off your forehead can cause damage to your brain, if done often enough.

Brain scans on 32 amateur soccer players (average age 31) have revealed that those who estimated heading the ball more than 1,000-1,500 times in the past year had damage to white matter similar to that seen in patients with concussion.

Six brain regions were seen to be affected: one in the frontal lobe and five in the temporo-occipital cortex. These regions are involved in attention, memory, executive functioning and higher-order visual functions. The number of headings (obviously very rough estimates, based presumably on individuals’ estimates of how often they play and how often they head the ball on average during a game) needed to produce measurable decreases in the white matter integrity varied per region. In four of temporo-occipital regions, the threshold number was around 1500; in the fifth it was only 1000; in the frontal lobe, it was 1300.

Those with the highest annual heading frequency also performed worse on tests of verbal memory and psychomotor speed (activities that require mind-body coordination, like throwing a ball).

This is only a small study and clearly more research is required, but the findings indicate that we should lower our ideas of what constitutes ‘harm’ to the brain — if repetition is frequent enough, even mild knocks can cause damage. This adds to the evidence I discussed in a recent blog post, that even mild concussions can produce long-lasting trauma to the brain, and it is important to give your brain time to repair itself.

At the moment we can only speculate on the effect such repetition might have to the vulnerable brains of children.

The researchers suggest that heading should be monitored to prevent players exceeding unsafe exposure thresholds.

Reference: 

Kim, N., Zimmerman, M., Lipton, R., Stewart, W., Gulko, E., Lipton, M. & Branch, C. 2011. PhD Making Soccer Safer for the Brain: DTI-defined Exposure Thresholds for White Matter Injury Due to Soccer Heading. Presented November 30 at the annual meeting of the Radiological Society of North America (RSNA) in Chicago.

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Another challenge to idea that men are better at spatial thinking

October, 2011

A cross-cultural study finds a significant gender difference on a simple puzzle problem for one culture but no gender difference for another. The difference was only partly explained by education.

Here’s an intriguing approach to the long-standing debate about gender differences in spatial thinking. The study involved 1,279 adults from two cultural groups in India. One of these groups was patrilineal, the other matrilineal. The volunteers were given a wooden puzzle to assemble as quickly as they could.

Within the patrilineal group, men were on average 36% faster than women. Within the matrilineal group, however, there was no difference between the genders.

I have previously reported on studies showing how small amounts of spatial training can close the gap in spatial abilities between the genders. It has been argued that in our culture, males are directed toward spatial activities (construction such as Lego; later, video games) more than females are.

In this case, the puzzle was very simple. However, general education was clearly one factor mediating this gender difference. In the patrilineal group, males had an average 3.67 more years of education, while in the matrilineal group, men and women had the same amount of education. When education was included in the statistical analysis, a good part of the difference between the groups was accounted for — but not all.

While we can only speculate about the remaining cause, it is interesting to note that, among the patrilineal group, the gender gap was decidedly smaller among those who lived in households not wholly owned by males (in the matrilineal group, men are not allowed to own property, so this comparison cannot be made).

It is also interesting to note that the men in the matrilineal group were faster than the men in the patrilineal group. This is not a function of education differences, because education in the matrilineal group was slightly less than that of males in the patrilineal group.

None of the participants had experience with puzzle solving, and both groups had similar backgrounds, being closely genetically related and living in villages geographically close. Participants came from eight villages: four patrilineal and four matrilineal.

Reference: 

[2519] Hoffman, M., Gneezy U., & List J. A.
(2011).  Nurture affects gender differences in spatial abilities.
Proceedings of the National Academy of Sciences. 108(36), 14786 - 14788.

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Visual Memory

Older news items (pre-2010) brought over from the old website

More light shed on distinction between long and short-term memory

The once clear-cut distinction between long- and short-term memory has increasingly come under fire in recent years. A new study involving patients with a specific form of epilepsy called 'temporal lobe epilepsy with bilateral hippocampal sclerosis' has now clarified the distinction. The patients, who all had severely compromised hippocampi, were asked to try and memorize photographic images depicting normal scenes. Their memory was tested and brain activity recorded after five seconds or 60 minutes. As expected, the patients could not remember the images after 60 minutes, but could distinguish seen-before images from new at five seconds. However, their memory was poor when asked to recall details about the images. Brain activity showed that short-term memory for details required the coordinated activity of a network of visual and temporal brain areas, whereas standard short-term memory drew on a different network, involving frontal and parietal regions, and independent of the hippocampus.

[996] Cashdollar, N., Malecki U., Rugg-Gunn F. J., Duncan J. S., Lavie N., & Duzel E.
(2009).  Hippocampus-dependent and -independent theta-networks of active maintenance.
Proceedings of the National Academy of Sciences. 106(48), 20493 - 20498.

http://www.eurekalert.org/pub_releases/2009-11/ucl-tal110909.php

Individual differences in working memory capacity depend on two factors

A new computer model adds to our understanding of working memory, by showing that working memory can be increased by the action of the prefrontal cortex in reinforcing activity in the parietal cortex (where the information is temporarily stored). The idea is that the prefrontal cortex sends out a brief stimulus to the parietal cortex that generates a reverberating activation in a small subpopulation of neurons, while inhibitory interactions with neurons further away prevents activation of the entire network. This lateral inhibition is also responsible for limiting the mnemonic capacity of the parietal network (i.e. provides the limit on your working memory capacity). The model has received confirmatory evidence from an imaging study involving 25 volunteers. It was found that individual differences in performance on a short-term visual memory task were correlated with the degree to which the dorsolateral prefrontal cortex was activated and its interconnection with the parietal cortex. In other words, your working memory capacity is determined by both storage capacity (in the posterior parietal cortex) and prefrontal top-down control. The findings may help in the development of ways to improve working memory capacity, particularly when working memory is damaged.

[441] Edin, F., Klingberg T., Johansson P., McNab F., Tegner J., & Compte A.
(2009).  Mechanism for top-down control of working memory capacity.
Proceedings of the National Academy of Sciences. 106(16), 6802 - 6807.

http://www.eurekalert.org/pub_releases/2009-04/i-id-aot040109.php

Some short-term memories die suddenly, no fading

We don’t remember everything; the idea of memory as being a video faithfully recording every aspect of everything we have ever experienced is a myth. Every day we look at the world and hold a lot of what we say for no more than a few seconds before discarding it as not needed any more. Until now it was thought that these fleeting visual memories faded away, gradually becoming more imprecise. Now it seems that such memories remain quite accurate as long as they exist (about 4 seconds), and then just vanish away instantly. The study involved testing memory for shapes and colors in 12 adults, and it was found that the memory for shape or color was either there or not there – the answers either correct or random guesses. The probability of remembering correctly decreased between 4 and 10 seconds.

[941] Zhang, W., & Luck S. J.
(2009).  Sudden death and gradual decay in visual working memory.
Psychological Science: A Journal of the American Psychological Society / APS. 20(4), 423 - 428.

http://www.eurekalert.org/pub_releases/2009-04/uoc--ssm042809.php

Where visual short-term memory occurs

Working memory used to be thought of as a separate ‘store’, and now tends to be regarded more as a process, a state of mind. Such a conception suggests that it may occur in the same regions of the brain as long-term memory, but in a pattern of activity that is somehow different from LTM. However, there has been little evidence for that so far. Now a new study has found that information in WM may indeed be stored via sustained, but low, activity in sensory areas. The study involved volunteers being shown an image for one second and instructed to remember either the color or the orientation of the image. After then looking at a blank screen for 10 seconds, they were shown another image and asked whether it was the identical color/orientation as the first image. Brain activity in the primary visual cortex was scanned during the 10 second delay, revealing that areas normally involved in processing color and orientation were active during that time, and that the pattern only contained the targeted information (color or orientation).

[1032] Serences, J. T., Ester E. F., Vogel E. K., & Awh E.
(2009).  Stimulus-Specific Delay Activity in Human Primary Visual Cortex.
Psychological Science. 20(2), 207 - 214.

http://www.eurekalert.org/pub_releases/2009-02/afps-sih022009.php
http://www.eurekalert.org/pub_releases/2009-02/uoo-dsm022009.php

The finding is consistent with that of another study published this month, in which participants were shown two examples of simple striped patterns at different orientations and told to hold either one or the other of the orientations in their mind while being scanned. Orientation is one of the first and most basic pieces of visual information coded and processed by the brain. Using a new decoding technique, researchers were able to predict with 80% accuracy which of the two orientations was being remembered 11 seconds after seeing a stimulus, from the activity patterns in the visual areas. This was true even when the overall level of activity in these visual areas was very weak, no different than looking at a blank screen.

[652] Harrison, S. A., & Tong F.
(2009).  Decoding reveals the contents of visual working memory in early visual areas.
Nature. 458(7238), 632 - 635.

http://www.eurekalert.org/pub_releases/2009-02/vu-edi021709.php
http://www.physorg.com/news154186809.html

Even toddlers can ‘chunk' information for better remembering

We all know it’s easier to remember a long number (say a phone number) when it’s broken into chunks. Now a study has found that we don’t need to be taught this; it appears to come naturally to us. The study showed 14 months old children could track only three hidden objects at once, in the absence of any grouping cues, demonstrating the standard limit of working memory. However, with categorical or spatial cues, the children could remember more. For example, when four toys consisted of two groups of two familiar objects, cats and cars, or when six identical orange balls were grouped in three groups of two.

[196] Feigenson, L., & Halberda J.
(2008).  From the Cover: Conceptual knowledge increases infants' memory capacity.
Proceedings of the National Academy of Sciences. 105(29), 9926 - 9930.

http://www.eurekalert.org/pub_releases/2008-07/jhu-etg071008.php

Full text available at http://www.pnas.org/content/105/29/9926.abstract?sid=c01302b6-cd8e-4072-842c-7c6fcd40706f

Working memory has a fixed number of 'slots'

A study that showed volunteers a pattern of colored squares for a tenth of a second, and then asked them to recall the color of one of the squares by clicking on a color wheel, has found that working memory acts like a high-resolution camera, retaining three or four features in high detail. Unlike a digital camera, however, it appears that you can’t increase the number of images you can store by lowering the resolution. The resolution appears to be constant for a given individual. However, individuals do differ in the resolution of each feature and the number of features that can be stored.

[278] Zhang, W., & Luck S. J.
(2008).  Discrete fixed-resolution representations in visual working memory.
Nature. 453(7192), 233 - 235.

http://www.physorg.com/news126432902.html
http://www.eurekalert.org/pub_releases/2008-04/uoc--wmh040208.php

And another study of working memory has attempted to overcome the difficulties involved in measuring a person’s working memory capacity (ensuring that no ‘chunking’ of information takes place), and concluded that people do indeed have a fixed number of ‘slots’ in their working memory. In the study, participants were shown two, five or eight small, scattered, different-colored squares in an array, which was then replaced by an array of the same squares without the colors, after which the participant was shown a single color in one location and asked to indicate whether the color in that spot had changed from the original array.

[437] Rouder, J. N., Morey R. D., Cowan N., Zwilling C. E., Morey C. C., & Pratte M. S.
(2008).  An assessment of fixed-capacity models of visual working memory.
Proceedings of the National Academy of Sciences. 105(16), 5975 - 5979.

http://www.eurekalert.org/pub_releases/2008-04/uom-mpd042308.php

Impressive feats in visual memory

In light of all the recent experiments emphasizing how small our short-term visual memory is, it’s comforting to be reminded that, nevertheless, we have an amazing memory for pictures — in the right circumstances. Those circumstances include looking at images of familiar objects, as opposed to abstract artworks, and being motivated to do well (the best-scoring participant was given a cash prize). In the study, 14 people aged 18 to 40 viewed 2,500 images, one at a time, for a few seconds. Afterwards, they were shown pairs of images and asked to select the exact image they had seen earlier. The previously viewed item could be paired with either an object from a novel category, an object of the same basic-level category, or the same object in a different state or pose. Stunningly, participants on average chose the correct image 92%, 88% and 87% of the time, in each of the three pairing categories respectively.

[870] Brady, T. F., Konkle T., Alvarez G. A., & Oliva A.
(2008).  Visual long-term memory has a massive storage capacity for object details.
Proceedings of the National Academy of Sciences. 105(38), 14325 - 14329.

Full text available at http://www.pnas.org/content/105/38/14325.abstract

Attention grabbers snatch lion's share of visual memory

It’s long been thought that when we look at a visually "busy" scene, we are only able to store a very limited number of objects in our visual short-term or working memory. For some time, this figure was believed to be four or five objects, but a recent report suggested it could be as low as two. However, a new study reveals that although it might not be large, it’s more flexible than we thought. Rather than being restricted to a limited number of objects, it can be shared out across the whole image, with more memory allocated for objects of interest and less for background detail. What’s of interest might be something we’ve previously decided on (i.e., we’re searching for), or something that grabs our attention.  Eye movements also reveal how brief our visual memory is, and that what our eyes are looking at isn’t necessarily what we’re ‘seeing’ — when people were asked to look at objects in a particular sequence, but the final object disappeared before their eyes moved on to it, it was found that the observers could more accurately recall the location of the object that they were about to look at than the one that they had just been looking at.

[1398] Bays, P. M., & Husain M.
(2008).  Dynamic shifts of limited working memory resources in human vision.
Science (New York, N.Y.). 321(5890), 851 - 854.

http://www.physorg.com/news137337380.html

More on how short-term memory works

It’s been established that visual working memory is severely limited — that, on average, we can only be aware of about four objects at one time. A new study explored the idea that this capacity might be affected by complexity, that is, that we can think about fewer complex objects than simple objects. It found that complexity did not affect memory capacity. It also found that some people have clearer memories of the objects than other people, and that this is not related to how many items they can remember. That is, a high IQ is associated with the ability to hold more items in working memory, but not with the clarity of those items.

[426] Awh, E., Barton B., & Vogel E. K.
(2007).  Visual working memory represents a fixed number of items regardless of complexity.
Psychological Science: A Journal of the American Psychological Society / APS. 18(7), 622 - 628.

http://www.eurekalert.org/pub_releases/2007-07/uoo-htb071107.php
http://www.physorg.com/news103472118.html

Support for labeling as an aid to memory

A study involving an amnesia-inducing drug has shed light on how we form new memories. Participants in the study participants viewed words, photographs of faces and landscapes, and abstract pictures one at a time on a computer screen. Twenty minutes later, they were shown the words and images again, one at a time. Half of the images they had seen earlier, and half were new. They were then asked whether they recognized each one. For one session they were given midazolam, a drug used to relieve anxiety during surgical procedures that also causes short-term anterograde amnesia, and for one session they were given a placebo.
It was found that the participants' memory while in the placebo condition was best for words, but the worst for abstract images. Midazolam impaired the recognition of words the most, impaired memory for the photos less, and impaired recognition of abstract pictures hardly at all. The finding reinforces the idea that the ability to recollect depends on the ability to link the stimulus to a context, and that unitization increases the chances of this linking occurring. While the words were very concrete and therefore easy to link to the experimental context, the photographs were of unknown people and unknown places and thus hard to distinctively label. The abstract images were also unfamiliar and not unitized into something that could be described with a single word.

[1216] Reder, L. M., Oates J. M., Thornton E. R., Quinlan J. J., Kaufer A., & Sauer J.
(2006).  Drug-Induced Amnesia Hurts Recognition, but Only for Memories That Can Be Unitized.
Psychological science : a journal of the American Psychological Society / APS. 17(7), 562 - 567.

http://www.sciencedaily.com/releases/2006/07/060719092800.htm

Discovery disproves simple concept of memory as 'storage space'

The idea of memory “capacity” has become more and more eroded over the years, and now a new technique for measuring brainwaves seems to finally knock the idea on the head. Consistent with recent research suggesting that a crucial problem with aging is a growing inability to ignore distracting information, this new study shows that visual working memory depends on your ability to filter out irrelevant information. Individuals have long been characterized as having a “high” working memory capacity or a “low” one — the assumption has been that these people differ in their storage capacity. Now it seems it’s all about a neural mechanism that controls what information gets into awareness. People with high capacity have a much better ability to ignore irrelevant information.

[1091] Vogel, E. K., McCollough A. W., & Machizawa M. G.
(2005).  Neural measures reveal individual differences in controlling access to working memory.
Nature. 438(7067), 500 - 503.

http://www.eurekalert.org/pub_releases/2005-11/uoo-dds111805.php

Language cues help visual learning in children

A study of 4-year-old children has found that language, in the form of specific kinds of sentences spoken aloud, helped them remember mirror image visual patterns. The children were shown cards bearing red and green vertical, horizontal and diagonal patterns that were mirror images of one another. When asked to choose the card that matched the one previously seen, the children tended to mistake the original card for its mirror image, showing how difficult it was for them to remember both color and location. However, if they were told, when viewing the original card, a mnemonic cue such as ‘The red part is on the left’, they performed “reliably better”.

The paper was presented by a graduate student at the 17th annual meeting of the American Psychological Society, held May 26-29 in Los Angeles.

http://www.eurekalert.org/pub_releases/2005-05/jhu-lc051705.php

An advantage of age

A study comparing the ability of young and older adults to indicate which direction a set of bars moved across a computer screen has found that although younger participants were faster when the bars were small or low in contrast, when the bars were large and high in contrast, the older people were faster. The results suggest that the ability of one neuron to inhibit another is reduced as we age (inhibition helps us find objects within clutter, but makes it hard to see the clutter itself). The loss of inhibition as we age has previously been seen in connection with cognition and speech studies, and is reflected in our greater inability to tune out distraction as we age. Now we see the same process in vision.

[1356] Betts, L. R., Taylor C. P., Sekuler A. B., & Bennett P. J.
(2005).  Aging Reduces Center-Surround Antagonism in Visual Motion Processing.
Neuron. 45(3), 361 - 366.

http://psychology.plebius.org/article.htm?article=739
http://www.eurekalert.org/pub_releases/2005-02/mu-opg020305.php

Why working memory capacity is so limited

There’s an old parlor game whereby someone brings into a room a tray covered with a number of different small objects, which they show to the people in the room for one minute, before whisking it away again. The participants are then required to write down as many objects as they can remember. For those who perform badly at this type of thing, some consolation from researchers: it’s not (entirely) your fault. We do actually have a very limited storage capacity for visual short-term memory.
Now visual short-term memory is of course vital for a number of functions, and reflecting this, there is an extensive network of brain structures supporting this type of memory. However, a new imaging study suggests that the limited storage capacity is due mainly to just one of these regions: the posterior parietal cortex. An interesting distinction can be made here between registering information and actually “holding it in mind”. Activity in the posterior parietal cortex strongly correlated with the number of objects the subjects were able to remember, but only if the participants were asked to remember. In contrast, regions of the visual cortex in the occipital lobe responded differently to the number of objects even when participants were not asked to remember what they had seen.

[598] Todd, J. J., & Marois R.
(2004).  Capacity limit of visual short-term memory in human posterior parietal cortex.
Nature. 428(6984), 751 - 754.

http://www.eurekalert.org/pub_releases/2004-04/vu-slo040704.php
http://tinyurl.com/2jzwe (Telegraph article)

Brain signal predicts working memory capacity

Our visual short-term memory may have an extremely limited capacity, but some people do have a greater capacity than others. A new study reveals that an individual's capacity for such visual working memory can be predicted by his or her brainwaves. In the study, participants briefly viewed a picture containing colored squares, followed by a one-second delay, and then a test picture. They pressed buttons to indicate whether the test picture was identical to -- or differed by one color -- from the one seen earlier. The more squares a subject could correctly identify having just seen, the greater his/her visual working memory capacity, and the higher the spike of corresponding brain activity – up to a point. Neural activity of subjects with poorer working memory scores leveled off early, showing little or no increase when the number of squares to remember increased from 2 to 4, while those with high capacity showed large increases. Subjects averaged 2.8 squares.

[1154] Vogel, E. K., & Machizawa M. G.
(2004).  Neural activity predicts individual differences in visual working memory capacity.
Nature. 428(6984), 748 - 751.

http://www.eurekalert.org/pub_releases/2004-04/niom-bsp041604.php

Learning without desire or awareness

We have long known that learning can occur without attention. A recent study demonstrates learning that occurs without attention, without awareness and without any task relevance. Subjects were repeatedly presented with a background motion signal so weak that its direction was not visible; the invisible motion was an irrelevant background to the central task that engaged the subject's attention. Despite being below the threshold of visibility and being irrelevant to the central task, the repetitive exposure improved performance specifically for the direction of the exposed motion when tested in a subsequent suprathreshold test. These results suggest that a frequently presented feature sensitizes the visual system merely owing to its frequency, not its relevance or salience.

[594] Watanabe, T., Nanez J. E., & Sasaki Y.
(2001).  Perceptual learning without perception.
Nature. 413(6858), 844 - 848.

http://www.nature.com/nsu/011025/011025-12.html
http://tinyurl.com/ix98

Visual memory better than previously thought

Why is it that you can park your car at a huge mall and find it a few hours later without much problem, or make your way through a store you have never been to before? The answer may lie in our ability to build up visual memories of a scene in a short period of time. A new study counters current thinking that visual memory is generally poor and that people quickly forget the details of what they have seen. It appears that even with very limited visual exposure to a scene, people are able to build up strong visual memories and, in fact, their recall of objects in the scene improved with each exposure. It is suggested these images aren't stored in short-term or long-term memory, but in medium-term memory, which lasts for a few minutes and appears to be specific to visual information as opposed to verbal or semantic information. "Medium-term memory depends on the visual context of the scene, such as the background, furniture and walls, which seems to be key in the ability to keep in mind the location and identity of objects. These disposable accumulated visual memories can be recalled in a few minutes if faced with that scene again, but are discarded in a day or two if the scene is not viewed again so they don't take up valuable memory space."

Melcher, D. 2001. Persistence of visual memory for scenes. Nature, 412 (6845), 401.

http://www.eurekalert.org/pub_releases/2001-07/rtsu-rrf072501.php

tags memworks: 

Perception

See also

Smell

Hearing

Vision

Older news items (pre-2010) brought over from the old website

Perception affected by mood

An imaging study has revealed that when people were shown a composite image with a face surrounded by "place" images, such as a house, and asked to identify the gender of the face, those in whom a bad mood had been induced didn’t process the places in the background. However, those in a good mood took in both the focal and background images. These differences in perception were coupled with differences in activity in the parahippocampal place area. Increasing the amount of information is of course not necessarily a good thing, as it may result in more distraction.

[1054] Schmitz, T. W., De Rosa E., & Anderson A. K.
(2009).  Opposing Influences of Affective State Valence on Visual Cortical Encoding.
J. Neurosci.. 29(22), 7199 - 7207.

http://www.eurekalert.org/pub_releases/2009-06/uot-pww060309.php

What we perceive is not what we sense

Perceiving a simple touch may depend as much on memory, attention, and expectation as on the stimulus itself. A study involving macaque monkeys has found that the monkeys’ perception of a touch (varied in intensity) was more closely correlated with activity in the medial premotor cortex (MPC), a region of the brain's frontal lobe known to be involved in making decisions about sensory information, than activity in the primary somatosensory cortex (which nevertheless accurately recorded the intensity of the sensation). MPC neurons began to fire before the stimulus even touched the monkeys' fingertips — presumably because the monkey was expecting the stimulus.

[263] de Lafuente, V., & Romo R.
(2005).  Neuronal correlates of subjective sensory experience.
Nat Neurosci. 8(12), 1698 - 1703.

http://www.eurekalert.org/pub_releases/2005-11/hhmi-tsi110405.php

Varied sensory experience important in childhood

A new baby has far more connections between neurons than necessary; from birth to about age 12 the brain trims 50% of these unnecessary connections while at the same time building new ones through learning and sensory stimulation — in other words, tailoring the brain to its environment. A mouse study has found that without enough sensory stimulation, infant mice lose fewer connections — indicating that connections need to be lost in order for appropriate ones to grow. The findings support the idea that parents should try to expose their children to a variety of sensory experiences.

[479] Zuo, Y., Yang G., Kwon E., & Gan W-B.
(2005).  Long-term sensory deprivation prevents dendritic spine loss in primary somatosensory cortex.
Nature. 436(7048), 261 - 265.

http://www.sciencentral.com/articles/view.htm3?article_id=218392607

Brain regions that process reality and illusion identified

Researchers have now identified the regions of the brain involved in processing what’s really going on, and what we think is going on. Macaque monkeys played a virtual reality video game in which the monkeys were tricked into thinking that they were tracing ellipses with their hands, although they actually were moving their hands in a circle. Monitoring of nerve cells revealed that the primary motor cortex represented the actual movement while the signals from cells in a neighboring area, called the ventral premotor cortex, were generating elliptical shapes. Knowing how the brain works to distinguish between action and perception will help efforts to build biomedical devices that can control artificial limbs, some day enabling the disabled to move a prosthetic arm or leg by thinking about it.

[1107] Schwartz, A. B., Moran D. W., & Reina A. G.
(2004).  Differential Representation of Perception and Action in the Frontal Cortex.
Science. 303(5656), 380 - 383.

http://news-info.wustl.edu/tips/page/normal/652.html
http://www.eurekalert.org/pub_releases/2004-02/wuis-rpb020704.php

Memory different depending on whether information received via eyes or ears

Carnegie Mellon scientists using magnetic resonance imaging found quite different brain activity patterns for reading and listening to identical sentences. During reading, the right hemisphere was not as active as expected, suggesting a difference in the nature of comprehension experienced when reading versus listening. When listening, there was greater activation in a part of Broca's area associated with verbal working memory, suggesting that there is more semantic processing and working memory storage in listening comprehension than in reading. This should not be taken as evidence that comprehension is better in one or other of these situations, merely that it is different. "Listening to an audio book leaves a different set of memories than reading does. A newscast heard on the radio is processed differently from the same words read in a newspaper."

[2540] Michael, E. B., Keller T. A., Carpenter P. A., & Just M A.
(2001).  fMRI investigation of sentence comprehension by eye and by ear: Modality fingerprints on cognitive processes.
Human Brain Mapping. 13(4), 239 - 252.

http://www.eurekalert.org/pub_releases/2001-08/cmu-tma081401.php

The chunking of our lives: the brain "sees" life in segments

We talk about "chunking" all the time in the context of memory. But the process of breaking information down into manageable bits occurs, it seems, right from perception. Magnetic resonance imaging reveals that when people watched movies of common, everyday, goal-directed activities (making the bed, doing the dishes, ironing a shirt), their brains automatically broke these continuous events into smaller segments. The study also identified a network of brain areas that is activated during the perception of boundaries between events. "The fact that changes in brain activity occurred during the passive viewing of movies indicates that this is how we normally perceive continuous events, as a series of segments rather than a dynamic flow of action."

Zacks, J.M., Braver, T.S., Sheridan, M.A., Donaldson, D.I., Snyder, A.Z., Ollinger, J.M., Buckner, R.L. & Raichle, M.E. 2001. Human brain activity time-locked to perceptual event boundaries. Nature Neuroscience, 4(6), 651-5.

http://www.eurekalert.org/pub_releases/2001-07/aaft-bp070201.php

Amygdala may be critical for allowing perception of emotionally significant events despite inattention

We choose what to pay attention to, what to remember. We give more weight to some things than others. Our perceptions and memories of events are influenced by our preconceptions, and by our moods. Researchers at Yale and New York University have recently published research indicating that the part of the brain known as the amygdala is responsible for the influence of emotion on perception. This builds on previous research showing that the amygdala is critically involved in computing the emotional significance of events. The amygdala is connected to those brain regions dealing with sensory experiences, and the theory that these connections allow the amygdala to influence early perceptual processing is supported by this research. Dr. Anderson suggests that “the amygdala appears to be critical for the emotional tuning of perceptual experience, allowing perception of emotionally significant events to occur despite inattention.”

[968] Anderson, A. K., & Phelps E. A.
(2001).  Lesions of the human amygdala impair enhanced perception of emotionally salient events.
Nature. 411(6835), 305 - 309.

http://www.eurekalert.org/pub_releases/2001-05/NYU-Infr-1605101.php

tags memworks: 

Working memory capacity not 4 but 2+2

October, 2011

A monkey study finds that our very limited working memory capacity of around 4 items reflects two capacities of two items. The finding has practical implications for information presentation.

In the study, two rhesus monkeys were given a standard human test of working memory capacity: an array of colored squares, varying from two to five squares, was shown for 800 msec on a screen. After a delay, varying from 800 to 1000 msec, a second array was presented. This array was identical to the first except for a change in color of one item. The monkey was rewarded if its eyes went directly to this changed square (an infra-red eye-tracking system was used to determine this). During all this, activity from single neurons in the lateral prefrontal cortex and the lateral intraparietal area — areas critical for short-term memory and implicated in human capacity limitations — was recorded.

As with humans, the more squares in the array, the worse the performance (from 85% correct for two squares to 66.5% for 5). Their working memory capacity was calculated at 3.88 objects — i.e. the same as that of humans.

That in itself is interesting, speaking as it does to the question of how human intelligence differs from other animals. But the real point of the exercise was to watch what is happening at the single neuron level. And here a surprise occurred.

That total capacity of around 4 items was composed of two independent, smaller capacities in the right and left halves of the visual space. What matters is how many objects are in the hemifield an eye is covering. Each hemifield can only handle two objects. Thus, if the left side of the visual space contains three items, and the right side only one, information about the three items from the left side will be degraded. If the left side contains four items and the right side two, those two on the right side will be fine, but information from the four items on the left will be degraded.

Notice that the effect of more items than two in a hemifield is to decrease the total information from all the items in the hemifield — not to simply lose the additional items.

The behavioral evidence correlated with brain activity, with object information in LPFC neurons decreasing with increasing number of items in the same hemifield, but not the opposite hemifield, and the same for the intraparietal neurons (the latter are active during the delay; the former during the presentation).

The findings resolve a long-standing debate: does working memory function like slots, which we fill one by one with items until all are full, or as a pool that fills with information about each object, with some information being lost as the number of items increases? And now we know why there is evidence for both views, because both contain truth. Each hemisphere might be considered a slot, but each slot is a pool.

Another long-standing question is whether the capacity limit is a failure of perception or  memory. These findings indicate that the problem is one of perception. The neural recordings showed information about the objects being lost even as the monkeys were viewing them, not later as they were remembering what they had seen.

All of this is important theoretically, but there are also immediate practical applications. The work suggests that information should be presented in such a way that it’s spread across the visual space — for example, dashboard displays should spread the displays evenly on both sides of the visual field; medical monitors that currently have one column of information should balance it in right and left columns; security personnel should see displays scrolled vertically rather than horizontally; working memory training should present information in a way that trains each hemisphere separately. The researchers are forming collaborations to develop these ideas.

Reference: 

[2335] Buschman, T. J., Siegel M., Roy J. E., & Miller E. K.
(2011).  Neural substrates of cognitive capacity limitations.
Proceedings of the National Academy of Sciences.

Source: 

Topics: 

tags memworks: 

tags strategies: 

The durability and specificity of perceptual learning

September, 2011

Increasing evidence shows that perception is nowhere near the simple bottom-up process we once thought. Two recent perception studies add to the evidence.

Previous research has found practice improves your ability at distinguishing visual images that vary along one dimension, and that this learning is specific to the visual images you train on and quite durable. A new study extends the finding to more natural stimuli that vary on multiple dimensions.

In the small study, 9 participants learned to identify faces and 6 participants learned to identify “textures” (noise patterns) over the course of two hour-long sessions of 840 trials (consecutive days). Faces were cropped to show only internal features and only shown briefly, so this was not a particularly easy task. Participants were then tested over a year later (range: 10-18 months; average 13 and 15 months, respectively).

On the test, participants were shown both images from training and new images that closely resembled them. While accuracy rates were high for the original images, they plummeted for the very similar new images, indicating that despite the length of time since they had seen the original images, they still retained much of the memory of them.

Although practice improved performance across nearly all items and for all people, there were significant differences between both participants and individual stimuli. More interestingly, individual differences (in both stimuli and people) were stable across sessions (e.g., if you were third-best on day 1, you were probably third-best on day 2 too, even though you were doing better). In other words, learning didn’t produce any qualitative changes in the representations of different items — practice had nearly the same effect on all; differences were rooted in initial difficulty of discriminating the pattern.

However, while it’s true that individual differences were stable, that doesn’t mean that every person improved their performance the exact same amount with the same amount of practice. Interestingly (and this is just from my eye-ball examination of the graphs), it looks like there was more individual variation among the group looking at noise patterns. This isn’t surprising. We all have a lot of experience discriminating faces; we’re all experts. This isn’t the case with the textures. For these, people had to ‘catch on’ to the features that were useful in discriminating patterns. You would expect more variability between people in how long it takes to work out a strategy, and how good that strategy is. Interestingly, three of the six people in the texture group actually performed better on the test than they had done on the second day of training, over a year ago. For the other three, and all nine of those in the face group, test performance was worse than it had been on the second day of training (but decidedly better than the first day).

The durability and specificity of this perceptual learning, the researchers point out, resembles that found in implicit memory and some types of sensory adaptation. It also indicates that such perceptual learning is not limited, as has been thought, to changes early in the visual pathway, but produces changes in a wider network of cortical neurons, particularly in the inferior temporal cortex.

The second, unrelated, study also bears on this issue of specificity.

We look at a scene and extract the general features — a crowd of people, violently riotous or riotously happy? — or we look at a scene and extract specific features that over time we use to build patterns about what goes with what. The first is called “statistical summary perception”; the second “statistical learning”.

A study designed to disentangle these two processes found that you can only do one or other; you can’t derive both types of information at the same time. Thus, when people were shown grids of lines slanted to varying degrees, they could either assess whether the lines were generally leaning to the left or right, or they could learn to recognize pairs of lines that had been hidden repeatedly in the grids — but they couldn’t do both.

The fact that each of these tasks interfered with the other suggests that the two processes are fundamentally related.

Reference: 

Source: 

Topics: 

tags memworks: 

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 below in more detail. 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

Older news items (pre-2010) brought over from the old website

More on how meditation can improve attention

Another study adds to research showing meditation training helps people improve their ability to focus and ignore distraction. The new study shows that three months of rigorous training in Vipassana meditation improved people's ability to stabilize attention on target tones, when presented with tones in both ears and instructed to respond only to specific tones in one ear. Marked variability in response time is characteristic of those with ADHD.

[1500] 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.

http://www.physorg.com/news177347438.html

Meditation may increase gray matter

Adding to the increasing evidence for the cognitive benefits of meditation, a new imaging study of 22 experienced meditators and 22 controls has revealed that 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. There were no regions where controls had significantly more gray matter than meditators. These areas of the brain are all closely linked to emotion, and may explain meditators' improved ability in regulating their emotions.

[1055] Luders, E., Toga A. W., Lepore N., & Gaser C.
(2009).  The underlying anatomical correlates of long-term meditation: Larger hippocampal and frontal volumes of gray matter.
NeuroImage. 45(3), 672 - 678.

http://www.eurekalert.org/pub_releases/2009-05/uoc--htb051209.php

Meditation technique can temporarily improve visuospatial abilities

And continuing on the subject of visual short-term memory, a study involving experienced practitioners of two styles of meditation: Deity Yoga (DY) and Open Presence (OP) has found that, although meditators performed similarly to nonmeditators on two types of visuospatial tasks (mental rotation and visual memory), when they did the tasks immediately after meditating for 20 minutes (while the nonmeditators rested or did something else), practitioners of the DY style of meditation showed a dramatic improvement compared to OP practitioners and controls. In other words, although the claim that regular meditation practice can increase your short-term memory capacity was not confirmed, it does appear that some forms of meditation can temporarily (and dramatically) improve it. Since the form of meditation that had this effect was one that emphasizes visual imagery, it does support the idea that you can improve your imagery and visual memory skills (even if you do need to ‘warm up’ before the improvement is evident).

[860] Kozhevnikov, M., Louchakova O., Josipovic Z., & Motes M. A.
(2009).  The enhancement of visuospatial processing efficiency through Buddhist Deity meditation.
Psychological Science: A Journal of the American Psychological Society / APS. 20(5), 645 - 653.

http://www.sciencedaily.com/releases/2009/04/090427131315.htm
http://www.eurekalert.org/pub_releases/2009-04/afps-ssb042709.php

Transcendental Meditation reduces ADHD symptoms among students

A pilot study involving 10 middle school students with ADHD has found that those who participated in twice-daily 10 minute sessions of Trancendental Meditation for three months showed a dramatic reduction in stress and anxiety and improvements in ADHD symptoms and executive function. The effect was much greater than expected. ADHD children have a reduced ability to cope with stress.
A second, recently completed study has also found that three months practice of the technique resulted in significant positive changes in brain functioning during visual-motor skills, especially in the circuitry of the brain associated with attention and distractibility. After six months practice, measurements of distractibility moved into the normal range.

Grosswald, S. J., Stixrud, W. R., Travis, F., & Bateh, M. A. (2008, December). Use of the Transcendental Meditation technique to reduce symptoms of Attention Deficit Hyperactivity Disorder (ADHD) by reducing stress and anxiety: An exploratory study. Current Issues in Education [On-line], 10(2). Available: http://cie.ed.asu.edu/volume10/number2/

http://www.eurekalert.org/pub_releases/2008-12/muom-tmr122408.php

Meditation speeds the mind's return after distraction

Another study comparing brain activity in experienced meditators and novices has looked at what happens when people meditating were interrupted by stimuli designed to mimic the appearance of spontaneous thoughts. The study compared 12 people with more than three years of daily practice in Zen meditation with 12 others who had never practiced meditation. It was found that, after interruption, experienced meditators were able to bring activity in most regions of the default mode network (especially the angular gyrus, a region important for processing language) back to baseline faster than non-meditators. The default mode network is associated with the occurrence of spontaneous thoughts and mind-wandering during wakeful rest. The findings indicate not only the attentional benefits of meditation, but also suggest a value for disorders characterized by excessive rumination or an abnormal production of task-unrelated thoughts, such as obsessive-compulsive disorder, anxiety disorder and major depression.

[910] Pagnoni, G., Cekic M., & Guo Y.
(2008).  “Thinking about Not-Thinking”: Neural Correlates of Conceptual Processing during Zen Meditation.
PLoS ONE. 3(9), e3083 - e3083.

Full text available at http://dx.plos.org/10.1371/journal.pone.0003083
http://www.eurekalert.org/pub_releases/2008-09/eu-zts082908.php

Improved attention with mindfulness training

More evidence of the benefits of meditation for attention comes from a study looking at the performance of novices taking part in an eight-week course that included up to 30 minutes of daily meditation, and experienced meditators who attended an intensive full-time, one-month retreat. Initially, the experienced participants demonstrated better executive functioning skills, the cognitive ability to voluntarily focus, manage tasks and prioritize goals. After the eight-week training, the novices had improved their ability to quickly and accurately move and focus attention, while the experienced participants, after their one-month intensive retreat, also improved their ability to keep attention "at the ready."

[329] Jha, A. P., Krompinger J., & Baime M. J.
(2007).  Mindfulness training modifies subsystems of attention.
Cognitive, Affective & Behavioral Neuroscience. 7(2), 109 - 119.

http://www.eurekalert.org/pub_releases/2007-06/uop-mtc062507.php

Brain scans show how meditation affects the brain

An imaging study comparing novice and experienced meditators found that experienced meditators showed greater activity in brain circuits involved in paying attention. But the most experienced meditators with at least 40,000 hours of experience showed a brief increase in activity as they started meditating, and then a drop to baseline, as if they were able to concentrate in an effortless way. Moreover, while the subjects meditated inside the MRI, the researchers periodically blasted them with disturbing noises. Among the experienced meditators, the noise had less effect on the brain areas involved in emotion and decision-making than among novice meditators. Among meditators with more than 40,000 hours of lifetime practice, these areas were hardly affected at all. The attention circuits affected by meditation are also involved in attention deficit hyperactivity disorder.

[1364] Brefczynski-Lewis, J. A., Lutz A., Schaefer H. S., Levinson D. B., & Davidson R. J.
(2007).  Neural correlates of attentional expertise in long-term meditation practitioners.
Proceedings of the National Academy of Sciences. 104(27), 11483 - 11488.

Full text is available at http://tinyurl.com/3d6wx4
http://www.physorg.com/news102179695.html

Meditation may improve attentional control

Paying attention to one thing can keep you from noticing something else. When people are shown two visual signals half a second apart, they often miss the second one — this effect is called the attentional blink. In a study involving 40 participants being trained in Vipassana meditation (designed to reduce mental distraction and improve sensory awareness), one group of 17 attended a 3 month retreat during which they meditated for 10–12 hours a day (practitioner group), and 23 simply received a 1-hour meditation class and were asked to meditate for 20 minutes daily for 1 week prior to each testing session (control group). The three months of intense training resulted in a smaller attentional blink and reduced brain activity to the first target (which was still detected with the same level of accuracy. Individuals with the most reduction in activity generally showed the most reduction in attentional blink size. The study demonstrates that mental training can result in increased attentional control.

[1153] Slagter, H. A., Lutz A., Greischar L. L., Francis A. D., Nieuwenhuis S., Davis J. M., et al.
(2007).  Mental Training Affects Distribution of Limited Brain Resources.
PLoS Biol. 5(6), e138 - e138.

Full text available at http://www.plosbiology.org/article/info:doi/10.1371/journal.pbio.0050138 
http://www.physorg.com/news97825611.html
http://www.eurekalert.org/pub_releases/2007-05/uow-mmf050407.php

Meditation skills of Buddhist monks yield clues to brain's regulation of attention

Recent research has suggested that skilled meditation can alter certain aspects of the brain's neural activity. A new study has now found evidence that certain types of trained meditative practice can influence the conscious experience of visual perceptual rivalry, a phenomenon thought to involve brain mechanisms that regulate attention and conscious awareness. Perceptual rivalry arises normally when two different images are presented to each eye, and it is manifested as a fluctuation in the "dominant" image that is consciously perceived. The study involved 76 Tibetan Buddhist monks with training ranging from 5 to 54 years. Tested during the practice of two types of meditation: a "compassion"-oriented meditation (contemplation of suffering within the world), and "one-point" meditation (involving the maintained focus of attention on a single object or thought). Major increases in the durations of perceptual dominance were experienced by monks practicing one-point meditation, but not during compassion-oriented meditation. Additionally, under normal conditions the monks showed longer stable perception (average 4.1 seconds compared to 2.6 seconds for meditation-naïve control subjects). The findings suggest that processes particularly associated with one-point meditation can considerably alter the normal fluctuations in conscious state that are induced by perceptual rivalry.

[350] Carter, O., Presti D., Callistemon C., Ungerer Y., Liu G., & Pettigrew J.
(2005).  Meditation alters perceptual rivalry in Tibetan Buddhist monks.
Current Biology. 15(11), R412-R413 - R412-R413.

http://www.eurekalert.org/pub_releases/2005-06/cp-mso060205.php

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Negative gossip sharpens attention

July, 2011

Faces of people about whom something negative was known were perceived more quickly than faces of people about whom nothing, or something positive or neutral, was known.

Here’s a perception study with an intriguing twist. In my recent round-up of perception news I spoke of how images with people in them were more memorable, and of how some images ‘jump out’ at you. This study showed different images to each participant’s left and right eye at the same time, creating a contest between them. The amount of time it takes the participant to report seeing each image indicates the relative priority granted by the brain.

So, 66 college students were shown faces of people, and told something ‘gossipy’ about each one. The gossip could be negative, positive or neutral — for example, the person “threw a chair at a classmate”; “helped an elderly woman with her groceries”; “passed a man on the street.” These faces were then shown to one eye while the other eye saw a picture of a house.

The students had to press one button when they could see a face and another when they saw a house. As a control, some faces were used that the students had never seen. The students took the same length of time to register seeing the unknown faces and those about which they had been told neutral or positive information, but pictures of people about whom they had heard negative information registered around half a second quicker, and were looked at for longer.

A second experiment confirmed the findings and showed that subjects saw the faces linked to negative gossip for longer periods than faces about whom they had heard about upsetting personal experiences.

Reference: 

[2283] Anderson, E., Siegel E. H., Bliss-Moreau E., & Barrett L F.
(2011).  The Visual Impact of Gossip.
Science. 332(6036), 1446 - 1448.

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