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
Short stressful events may improve working memory
We know that chronic stress has a detrimental effect on learning and memory, but a new rat study shows how acute stress (a short, sharp event) can produce a beneficial effect. The rats, trained to a level of 60-70% accuracy on a maze, were put through a 20-minute forced swim before being run through the maze again. Those who experienced this stressful event were better at running the maze 4 hours later, and a day later, than those not forced through the stressful event. It appears that the stress hormone corticosterone (cortisol in humans) increases transmission of the neurotransmitter glutamate in the prefrontal cortex and improves working memory. It also appears that chronic stress suppresses the transmission of glutamate in the prefrontal cortex of male rodents, while estrogen receptors in female rodents make them more resilient to chronic stress than male rats.
[1157] Yuen, E. Y., Liu W., Karatsoreos I. N., Feng J., McEwen B. S., & Yan Z.
(2009). Acute stress enhances glutamatergic transmission in prefrontal cortex and facilitates working memory.
Proceedings of the National Academy of Sciences of the United States of America. 106(33), 14075 - 14079.
http://www.eurekalert.org/pub_releases/2009-07/uab-sse072309.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.
Feigenson, L. & Halberda, J. 2008. 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
Brain-training to improve working memory boosts fluid intelligence
General intelligence is often separated into "fluid" and "crystalline" components, of which fluid intelligence is considered more reflective of “pure” intelligence, and largely resistant to training and learning effects. However, in a new study in which participants were given a series of training exercises designed to improve their working memory, fluid intelligence was found to have significantly improved, with the amount of improvement increasing with time spent training. The small study contradicts decades of research showing that improving on one kind of cognitive task does not improve performance on other kinds, so has been regarded with some skepticism by other researchers. More research is definitely needed, but the memory task did differ from previous studies, engaging executive functions such as those that inhibit irrelevant items, monitor performance, manage two tasks simultaneously, and update memory.
Jaeggi, S.M., Buschkuehl, M., Jonides, J. & Perrig, W.J. 2008. Improving fluid intelligence with training on working memory. PNAS, 105 (19), 6829-6833.
http://www.physorg.com/news128699895.html
http://www.sciam.com/article.cfm?id=study-shows-brain-power-can-be-bolstered
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
Children's under-achievement could be down to poor working memory
A survey of over three thousand children has found that 10% of school children across all age ranges suffer from poor working memory seriously affecting their learning. However, poor working memory is rarely identified by teachers, who often describe children with this problem as inattentive or as having lower levels of intelligence. The researchers have developed a new tool, a combination of a checklist and computer programme called the Working Memory Rating Scale, that enables teachers to identify and assess children's memory capacity in the classroom from as early as four years old. The tool has already been piloted successfully in 35 schools across the UK, and is now widely available. It has been translated into ten foreign languages.
http://www.physorg.com/news123404466.html
http://www.eurekalert.org/pub_releases/2008-02/du-cuc022608.php
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
Executive function as important as IQ for math success
A study of 141 preschoolers from low-income homes has found that a child whose IQ and executive functioning were both above average was three times more likely to succeed in math than a child who simply had a high IQ. The parts of executive function that appear to be particularly linked to math ability in preschoolers are working memory and inhibitory control. In this context, working memory may be thought of as the ability to keep information or rules in mind while performing mental tasks. Inhibitory control is the ability to halt automatic impulses and focus on the problem at hand. Inhibitory control was also important for reading ability. The finding offers the hope that training to improve executive function will improve academic performance
Blair, C. & Razza, R.P. 2007. Relating Effortful Control, Executive Function, and False Belief Understanding to Emerging Math and Literacy Ability in Kindergarten. Child Development, 78 (2), 647–663.
New research shows why too much memory may be a bad thing
People who are able to easily and accurately recall historical dates or long-ago events may have a harder time with word recall or remembering the day's current events. A mouse study reveals why. Neurogenesis has been thought of as a wholly good thing — having more neurons is surely a good thing — but now a mouse study has found that stopping neurogenesis in the hippocampus improved working memory. Working memory is highly sensitive to interference from information previously stored in memory, so it may be that having too much information may hinder performing everyday working memory tasks.
Saxe, M.D. et al. 2007. Paradoxical influence of hippocampal neurogenesis on working memory. Proceedings of the National Academy of Sciences, 104 (11), 4642-4646.
http://www.physorg.com/news94384934.html
http://www.eurekalert.org/pub_releases/2007-03/cumc-nrs032807.php
Implicit stereotypes and gender identification may affect female math performance
Relatedly, another study has come out showing that women enrolled in an introductory calculus course who possessed strong implicit gender stereotypes, (for example, automatically associating "male" more than "female" with math ability and math professions) and were likely to identify themselves as feminine, performed worse relative to their female counterparts who did not possess such stereotypes and who were less likely to identify with traditionally female characteristics. Strikingly, a majority of the women participating in the study explicitly expressed disagreement with the idea that men have superior math ability, suggesting that even when consciously disavowing stereotypes, female math students are still susceptible to negative perceptions of their ability.
Kiefer, A.K., & Sekaquaptewa, D. 2007. Implicit stereotypes, gender identification, and math performance: a prospective study of female math students. Psychological Science, 18(1), 13-18.
http://www.eurekalert.org/pub_releases/2007-01/afps-isa012407.php
Reducing the racial achievement gap
And staying with the same theme, a study that came out six months ago, and recently reviewed on the excellent new Scientific American Mind Matters blog, revealed that a single, 15-minute intervention erased almost half the racial achievement gap between African American and white students. The intervention involved writing a brief paragraph about which value, from a list of values, was most important to them and why. The intervention improved subsequent academic performance for some 70% of the African American students, but none of the Caucasians. The study was repeated the following year with the same results. It is thought that the effect of the intervention was to protect against the negative stereotypes regarding the intelligence and academic capabilities of African Americans.
[1082] Cohen, G. L., Garcia J., Apfel N., & Master A.
(2006). Reducing the Racial Achievement Gap: A Social-Psychological Intervention.
Science. 313(5791), 1307 - 1310.
Highly accomplished people more prone to failure than others when under stress
One important difference between those who do well academically and those who don’t is often working memory capacity. Those with a high working memory capacity find it easier to read and understand and reason, than those with a smaller capacity. However, a new study suggests there is a downside. Such people tend to heavily rely on their abundant supply of working memory and are therefore disadvantaged when challenged to solve difficult problems, such as mathematical ones, under pressure — because the distraction caused by stress consumes their working memory. They then fall back on the less accurate short-cuts that people with less adequate supplies of working memory tend to use, such as guessing and estimation. Such methods are not made any worse by working under pressure. In the study involving 100 undergraduates, performance of students with strong working memory declined to the same level as those with more limited working memory, when the students were put under pressure. Those with more limited working memory performed as well under added pressure as they did without the stress.
The findings were presented February 17 at the annual meeting of the American Association for the Advancement of Science.
http://www.eurekalert.org/pub_releases/2007-02/uoc-hap021607.php
Common gene version optimizes thinking but carries a risk
On the same subject, another study has found that the most common version of DARPP-32, a gene that shapes and controls a circuit between the striatum and prefrontal cortex, optimizes information filtering by the prefrontal cortex, thus improving working memory capacity and executive control (and thus, intelligence). However, the same version was also more prevalent among people who developed schizophrenia, suggesting that a beneficial gene variant may translate into a disadvantage if the prefrontal cortex is impaired. In other words, one of the things that make humans more intelligent as a species may also make us more vulnerable to schizophrenia.
[864] Kolachana, B., Kleinman J. E., Weinberger D. R., Meyer-Lindenberg A., Straub R. E., Lipska B. K., et al.
(2007). Genetic evidence implicating DARPP-32 in human frontostriatal structure, function, and cognition.
Journal of Clinical Investigation. 117(3), 672 - 682.
http://www.sciencedaily.com/releases/2007/02/070208230059.htm
http://www.eurekalert.org/pub_releases/2007-02/niom-cgv020707.php
People remember prices more easily if they have fewer syllables
The phonological loop — an important component of working memory —can only hold 1.5 to 2 seconds of spoken information. For that reason, faster speakers have an advantage over slower speakers. Now a consumer study reveals that every extra syllable in a product's price decreases its chances of being remembered by 20%. Thus, people who shorten the number of syllables (e.g. read 5,325 as 'five three two five' as opposed to 'five thousand three hundred and twenty five') have better recall. However, since we store information both verbally and visually, it’s also the case that unusual looking prices, such as $8.88, are recalled better than typical looking prices.
Vanhuele, M., Laurent, G., Dreze, X. & Calder, B. 2006. Consumers' Immediate Memory for Prices. Journal of Consumer Research, 33(2), 163-72.
http://www.sciencedaily.com/releases/2006/06/060623001231.htm
http://www.eurekalert.org/pub_releases/2006-06/uocp-prp062206.php
New view of hippocampus’s role in memory
Amnesiacs have overturned the established view of the hippocampus, and of the difference between long-and short-term memories. It appears the hippocampus is just as important for retrieving certain types of short-term memories as it is for long-term memories. The critical thing is not the age of the memory, but the requirement to form connections between pieces of information to create a coherent episode. The researchers suggest that, for the brain, the distinction between 'long-term' memory and 'short-term' memory are less relevant than that between ‘feature’ memory and ‘conjunction’ memory — the ability to remember specific things versus how they are related. The hippocampus may be thought of as the brain's switchboard, piecing individual bits of information together in context.
[817] Olson, I. R., Page K., Moore K S., Chatterjee A., & Verfaellie M.
(2006). Working Memory for Conjunctions Relies on the Medial Temporal Lobe.
J. Neurosci.. 26(17), 4596 - 4601.
http://origin.www.upenn.edu/pennnews/article.htm?id=963
http://www.eurekalert.org/pub_releases/2006-05/uop-aso053106.php
Learning and working memory
A 3-year research project on Working Memory and Cognition has reached its conclusion. The association between effective language learning and good short-term memory is, it seems, not a causal relationship. It is not that a good short-term memory is a prerequisite for long-term learning; it is that both short-term and long-term memory tasks tap the same ability to create representations of sufficient quality to support the maintenance of several of them at once.
Another finding is that metaphoric language often puts greater stress on working memory and so is harder to process than literal language.
Another study looked at differences between the abilities of musicians and persons who did not have music as an active hobby to remember series of notes presented in succession on a computer screen. The results show how expertise makes it possible to apparently bypass working memory limits, even when the memory items cannot be grouped into simple categories.
http://www.eurekalert.org/pub_releases/2006-03/uoh-nrd031306.php
http://www.sciencedaily.com/releases/2006/03/060320084440.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
How much can your mind keep track of?
A recent study has tried a new take on measuring how much a person can keep track of. It's difficult to measure the limits of processing capacity because most people automatically break down large complex problems into small, manageable chunks. To keep people from doing this, therefore, researchers created problems the test subjects wouldn’t be familiar with. 30 academics were presented with incomplete verbal descriptions of statistical interactions between fictitious variables, with an accompanying set of graphs that represented the interactions. It was found that, as the problems got more complex, participants performed less well and were less confident. They were significantly less able to accurately solve the problems involving four-way interactions than the ones involving three-way interactions, and were completely incapable of solving problems with five-way interactions. The researchers concluded that we cannot process more than four variables at a time (and at that, four is a strain).
[415] Halford, G. S., Baker R., McCredden J. E., & Bain J. D.
(2005). How many variables can humans process?.
Psychological Science: A Journal of the American Psychological Society / APS. 16(1), 70 - 76.
http://www.eurekalert.org/pub_releases/2005-03/aps-hmc030805.php
Cognitive therapy for ADHD
A researcher that has previously demonstrated that working memory capacity can be increased through training, has now reported that the training software has produced significant improvement in children with ADHD — a disability that is associated with deficits in working memory. The study involved 53 children with ADHD, aged 7-12, who were not on medication for their disability. 44 of these met the criterion of more than 20 days of training. Half the participants were assigned to the working memory training program and the other half to a comparison program. 60% of those who underwent the wm training program no longer met the clinical criteria for ADHD after five weeks of training. The children were tested on visual-spatial memory, which has the strongest link to inattention and ADHD. Further research is needed to show that training improves ability on a wider range of tasks.
[583] Klingberg, T., Fernell E., Olesen P. J., Johnson M., Gustafsson P., Dahlström K., et al.
(2005). Computerized Training of Working Memory in Children With ADHD-A Randomized, Controlled Trial.
Journal of the American Academy of Child & Adolescent Psychiatry. 44(2), 177 - 186.
http://www.sciam.com/article.cfm?articleID=000560D5-7252-12B9-9A2C83414B7F0000&sc=I100322
Anxiety adversely affects those who are most likely to succeed at exams
It has been thought that pressure harms performance on cognitive skills such as mathematical problem-solving by reducing the working memory capacity available for skill execution. However, a new study of 93 students has found that this applies only to those high in working memory. It appears that the advantage of a high working memory capacity disappears when that attention capacity is compromised by anxiety.
[355] Beilock, S. L., & Carr T. H.
(2005). When high-powered people fail: working memory and "choking under pressure" in math.
Psychological Science: A Journal of the American Psychological Society / APS. 16(2), 101 - 105.
http://www.eurekalert.org/pub_releases/2005-02/bpl-wup020705.php
Development of working memory with age
An imaging study of 20 healthy 8- to 30-year-olds has shed new light on the development of working memory. The study found that pre-adolescent children relied most heavily on the prefrontal and parietal regions of the brain during the working memory task; adolescents used those regions plus the anterior cingulate; and in adults, a third area of the brain, the medial temporal lobe, was brought in to support the functions of the other areas. Adults performed best. The results support the view that a person's ability to have voluntary control over behavior improves with age because with development, additional brain processes are used.
http://www.eurekalert.org/pub_releases/2004-10/uopm-dow102104.php
Training improves working memory capacity
Working memory capacity has traditionally been thought to be constant. Recent studies, however, suggest that working memory can be improved by training. In this recent imaging study, it was found that adults who practiced working memory tasks for 5 weeks showed increased brain activity in the middle frontal gyrus and superior and inferior parietal cortices. These changes could be evidence of training-induced plasticity in the neural systems that underlie working memory.
Olesen, P.J., Westerberg, H. & Klingberg, T. 2004. Increased prefrontal and parietal activity after training of working memory. Nature Neuroscience, 7(1), 75-9.
http://www.nature.com/cgi-taf/DynaPage.taf?file=/neuro/journal/v7/n1/abs/nn1165.html
Tests for working memory capacity more limited than thought
The so-called “magic number 7” has been a useful mnemonic for working memory capacity — how many items you can hold in your working memory at one time — but we’ve known for some time that it isn’t quite as it was originally thought. Apart from the fact that the “7” is an average, and that the idea of an “item” is awfully vague as far as informational content is concerned, we have known for some time that what is really important is how long it takes for you to say the words. Thus, Chinese can hold on average 9 items, because the words used in the test are short and simple to pronounce, whereas the Welsh can hold only 5 on average, because of the length and complexity of their words. (note: it’s not because we actually say these words out loud). Similarly, the finding that deaf users of American Sign Language have an average of only 5 items was thought to be because signs take longer to utter. However, new research casts doubt on this theory. The researchers were trying to devise a sign-language test that would be comparable to a hearing language test. To their surprise they found that even when signs were faster to pronounce than spoken language, signers recalled only five items. Also, hearing individuals who were fluent in American Sign Language scored differently when asked to recall spoken lists in order, versus when they recalled signed lists (seven heard items remembered, five signed items remembered). Up until this time, the predominant idea was that the number found by this test was a good measure of overall cognitive capacity, but this assumption must now be in doubt. It's suggested that a test requiring recall of items, but not in temporal order, is a better measure of cognitive capacity. The results have important implications for standardized tests, which often employ ordered-list retention as a measure of a person's mental aptitude.
[422] Boutla, M., Supalla T., Newport E. L., & Bavelier D.
(2004). Short-term memory span: insights from sign language.
Nat Neurosci. 7(9), 997 - 1002.
http://www.eurekalert.org/pub_releases/2004-08/uor-stm083104.php
Hippocampus and subiculum both critical for short-term memory
A new animal study has revealed that the hippocampus shares its involvement in short-term memory with an adjacent brain region, the subiculum. Both regions act together to establish and retrieve short-term memories. The process involves each region acting at different times, with the other region shutting off while the other is active. The shortest memories (10-15s) were found to be controlled almost exclusively by the subiculum. After 15s, the hippocampus took over. It was also found that the hippocampus appeared to respond in a way influenced by previous experiences, allowing it to anticipate future events on the basis of past outcomes. This is an advantage but can also cause errors.
[349] Deadwyler, S. A., & Hampson R. E.
(2004). Differential but Complementary Mnemonic Functions of the Hippocampus and Subiculum.
Neuron. 42(3), 465 - 476.
http://www.eurekalert.org/pub_releases/2004-05/wfub-nrs050604.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
Small world networks key to working memory
A computer model may reveal an important aspect of working memory. The key, researchers say, is that the neurons form a "small world" network. In such a network, regardless of its size, any two points within them are always linked by only a small number of steps. Working memory may rely on the same property.
[2547] Micheloyannis, S., Pachou E., Stam C. J., Vourkas M., Erimaki S., & Tsirka V.
(2006). Using graph theoretical analysis of multi channel EEG to evaluate the neural efficiency hypothesis.
Neuroscience Letters. 402(3), 273 - 277.
http://www.newscientist.com/article/mg18224481.600-its-a-small-world-inside-your-head.html
Memory-enhancing drugs for elderly may impair working memory and other executive functions
Drugs that increase the activity of an enzyme called protein kinase A improve long-term memory in aged mice and have been proposed as memory-enhancing drugs for elderly humans. However, the type of memory improved by this activity occurs principally in the hippocampus. A new study suggests that increased activity of this enzyme has a deleterious effect on working memory (which principally involves the prefrontal cortex). In other words, a drug that helps you remember a recent event may worsen your ability to remember what you’re about to do (to take an example).
Ramos, B.P., Birnbaum, S.G., Lindenmayer, I., Newton, S.S., Duman, R.S. & Arnsten, A.F.T. 2003. Dysregulation of Protein Kinase A Signaling in the Aged Prefrontal Cortex: New Strategy for Treating Age-Related Cognitive Decline. Neuron, 40, 835-845.
http://www.eurekalert.org/pub_releases/2003-11/naos-mdf110303.php
Sleep deprivation affects working memory
A recent study investigated the working memory capacities of individuals who were sleep-deprived. For nine days, 7 of the 12 participants slept four hours each night, and 5 slept for eight hours. Each morning, participants completed a computer task to measure how quickly they could access a list of numbers they had been asked to memorize. The list could be one, three, or five items long. Then participants were presented with a series of single digits and asked to answer "yes" or "no" to indicate whether each digit was one they had memorized. Those who slept eight hours a night steadily increased their working memory efficiency on this task, but those who slept only four hours a night failed to show any improvement in memory efficiency. Motor skill did not change across days for either group of participants.
Casement, M.D., Mullington, J.M., Broussard, J.L., & Press, D.Z. 2003. The effects of prolonged sleep restriction on working memory performance. Paper presented at the annual meeting of the Society for Neuroscience, New Orleans, LA.
http://www.eurekalert.org/pub_releases/2003-11/sfn-sfb_1111003.php
Why is it that people cannot keep their hands still when they talk? One reason may be that gesturing actually lightens cognitive load while a person is thinking of what to say. Adults and children were asked to remember a list of letters or words while explaining how they solved a math problem. Both groups remembered significantly more items when they gestured during their math explanations than when they did not gesture.
[1300] Goldin-Meadow, S., Nusbaum H., Kelly S. D., & Wagner S.
(2001). Explaining math: gesturing lightens the load.
Psychological Science: A Journal of the American Psychological Society / APS. 12(6), 516 - 522.