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