Neurogenesis interferes with past learning in infant and adult mice
May 12, 2014
|By Helen Shen and Nature magazine
Newly-generated neurons (white) that
integrated into the hippocampus, shown in this false-colour micrograph,
had seemingly counterintuitive effects on memory.
Credit: Jason SnyderFor anyone fighting to save old memories, a fresh crop of brain cells
may be the last thing they need. Research published today in Science suggests
that newly formed neurons in the hippocampus — an area of the brain
involved in memory formation — could dislodge previously learned
information. The work may provide clues as to why childhood memories are
so difficult to recall.
“The finding was very surprising to us initially. Most people think
new neurons mean better memory,” says Sheena Josselyn, a neuroscientist
who led the study together with her husband Paul Frankland at the
Hospital for Sick Children in Toronto, Canada.
Humans, mice and several other mammals grow new neurons in the
hippocampus throughout their lives — rapidly at first, but more and more
slowly with age. Researchers have previously shown that boosting neural
proliferation before learning can enhance memory formation in adult
mice. But the latest study shows that after information is learned,
neuron growth can degrade those memories.
Although seemingly counterintuitive, the disruptive role of these
neurons makes some sense, says Josselyn. She notes that some theoretical
models have predicted such an effect. “More neurons increase the
capacity to learn new memories in the future,” she says. “But memory is
based on a circuit, so if you add to this circuit, it makes sense that
it would disrupt it.” Newly added neurons could have a useful role in
clearing old memories and making way for new ones, says Josselyn.
Forgetting curve
The researchers tested newborn and adult mice on a conditioning task,
training the animals to fear an environment in which they received
repeated electric shocks. All the mice learned the task quickly, but
whereas infant mice remembered the negative experience for only one day
after training, adult mice retained the negative memory for several
weeks.
This difference seems to correlate with differences in neural
proliferation. Josselyn and her team were able to enhance memory
persistence in newborn mice by genetically and chemically suppressing
growth of new neurons after learning. And in adult mice, four to six
weeks of regular exercise — an activity known to promote neuron
proliferation — reduced the persistence of previously learned fear.
The genetic and chemical manipulations cannot be applied readily to
humans, so the findings will be difficult to pursue in people, says
Josselyn. But both mice and humans have ‘infantile amnesia’, or
pronounced forgetting of early life experiences. Josselyn says that
rapid neurogenesis in many young animals could help to explain the
phenomenon across species.
The researchers also examined learned fear in guinea pigs and in
Chilean rodents called degus — both of which have longer gestation
periods than mice, and correspondingly reduced brain growth after birth.
Baby degus and guinea pigs do not have infantile amnesia, but the
researchers were able to mimic its effects in the animals through
exercise or drugs that promote neuron growth.
“It's incredibly impressive. They covered everything from genetic and
pharmacological interventions, to behavioral interventions, to
cross-species comparisons," says Karl Deisseroth, a neuroscientist at
Stanford University in California who is collaborating with the group on
a separate project but did not contribute to the current study.
Deisseroth, who in 2005 published the computational model Josselyn
alludes to, says he is excited to see strong experimental validation of
the idea nearly ten years later.
Amar Sahay, a neuroscientist at Massachusetts General Hospital in
Boston, says that most previous work, including his own, has focused on
the effects of neurogenesis before memory formation. The latest work, by
examining what happens after learning, paints a more complete picture
of the relationship between neurogenesis and long-term memory
management. “It’s a very exciting study,” says Sahay.
Published on February 13, 2012 by Tracy P. Alloway, Ph.D.
Working memory is critical for many activities at school, from complex subjects such as reading comprehension, mental arithmetic, and word problems to simple tasks like copying from the board and navigating the halls. We have a limited space for processing information, and the size of various individuals' working memory capacity can vary greatly. For example, a 7-year-old who has working-memory problems may have a working memory capacity the same size as an average 4-year-old. This student will likely find it difficult to keep up with what the teacher says, will struggle to remember instructions, and will mix up words. In contrast, another 7-year-old may have working-memory skills the same size as an average 10-year-old. This student will be the first to finish individual work, will respond quickly to questions during group time, and may even be bored by school.
In everyday classroom activities, students with poor working memory often struggle in activities that place heavy demands on working memory. Thus, it is especially important for educators to be able to directly and accurately assess Working Memory. In my own research, I have published the Automated Working Memory Assessment (AWMA; published by Pearson Assessment, UK), a standardized assessment of verbal and visuo-spatial Working Memory. Not only does the AWMA eliminate the need for prior training in test administration, it also provides a practical and convenient way for educators to screen students for significant working memory problems. Currently, it is the only standardized assessment of working memory available for educators to use, and to date has been translated into 15 languages. Details on the reliability and validity of the AWMA, including research on it use with different learning needs populations, like dyslexia, ADHD, and Autistic Spectrum Disorder, can be found here:
A key question is whether the AWMA provides an accurate assessment of Working Memory in other languages. This is a question that colleagues of mine in Argentina were particularly interested in. The first step was to translate all 12 tests of the AWMA into Spanish. My colleagues who conducted the translation took into account various aspects of phonology, orthography, syntax, semantics, and communicational context (such as, word frequency). They also compared the translation, especially of the verbal tests, to a written work of different literary genres, such as popular science, editorial essays, and news articles from diverse Spanish-speaking countries, not only Spain or a particular Hispano- American country.
Next they recruited 6, 8, and 11 year olds from different demographic backgrounds in Buenos Aires and gave them the Spanish version of the AWMA. My colleagues found very similar patterns in performance between the Spanish-speaking children and the English-speaking children that I tested. Importantly, their results demonstrate that a normal distribution of scores and good relationship between the test scores.
This Spanish translation offers the first step in creating testing materials that are culturally appropriate and offers psychologists and clinicians an opportunity to reliably test Working Memory. The AWMA (and the various translations) is available from Pearson Assessment, UK.
Reference: Injoque-Ricle, I., Calero, A.D., Alloway, T.P., & Burin, D.I. (2011). Assessing Working Memory in Spanish-Speaking Children: Automated Working Memory Assessment Battery Adaptation. Learning and Individual Differences, 21, 78-84.
Children who under-achieve at school may just have a poor working memory rather than low intelligence, according to researchers who have produced the world's first tool to assess memory capacity in the classroom.
The researchers from Durham University surveyed more than 3,000 primary school children of all ages and found that 10% of them suffer from poor working memory, which seriously impedes their learning.
Nationally, this equates to almost 500,000 children in primary education being affected.
But the researchers found that teachers rarely identify a poor working memory and often describe children with this problem as inattentive or less intelligent.
Working memory is the ability to hold information in your head and manipulate it mentally - for example adding up two numbers spoken to you by someone else without using pen and paper or a calculator, or memorising verbal directions.
Children at school need this memory on a daily basis for a variety of tasks, such as following teachers' instructions or remembering sentences they have been asked to write down.
The new tool - a combination of a checklist and computer programme - will enable teachers to identify and assess children's memory capacity in the classroom from as early as four-years-old.
This should allow teachers to adopt new approaches to teaching children with poor memories, which in turn would help address the problem of under-achievement in schools.
Without appropriate intervention, poor working memory in children, which is thought to be genetic, can affect long-term academic success and prevent children from achieving their potential, the academics warned.
Although the tools have already been piloted successfully in 35 schools across the UK and have been translated into 10 languages, this is the first time they have been made widely available.
Lead researcher Dr Tracy Alloway, from Durham's school of education, told EducationGuardian.co.uk: "The concept of working memory is relatively new compared with IQ and only in the last 15 years have we been interested in the link between it and learning.
"It is a much more important predictor of learning than IQ because it measures a child's potential to learn rather than having any link to environment or socio-economic background, which are closely linked to IQ."
Teachers tend to identify children with poor working memories as having attention problems or "dreamers", she said, but the new test will allow them to screen children for the disorder.
"The only way children with poor working memory can go on to achieving academic success is by teaching them how to learn despite their smaller capacity to store information mentally," she said.
The checklist, called the Working Memory Rating Scale (WMRS), will enable teachers to identify children who they think may have a problem with working memory without immediately subjecting them to a test. A high score on this checklist shows that a child is likely to have memory problems that will affect their academic progress.
If the teacher feels significantly concerned about a child's performance in class, they can get the child to do the computerised Automated Working Memory Assessment (AWMA).
The tools also suggest ways for teachers to manage the children's working memory loads, which will minimise the chances of children failing to complete tasks. Examples include repeating instructions, talking in simple short sentences and breaking down tasks into smaller chunks of information.
Chris Evans, the headteacher of Lakes primary school in Redcar, Cleveland, who has been working with Alloway, said: "With some of the staff now trained to identify problems, we have the knowledge and tools to carry out a proper assessment and have the skills to help these children be more successful in school.
"We are already beginning to see children in a different light knowing more about the difficulties faced by children with impaired working memory. We realise that they are not daydreamers, inattentive or underachieving, but children who simply need a different approach.
"We think these new ways of learning can help both the teacher and the children to successfully complete their work."
Published on December 21, 2010
by Tracy Packiam Alloway, PhD
Working memory is the ability to hold information in your head and manipulate it mentally. You use this mental workspace when adding up two numbers spoken to you by someone else without being able to use pen and paper or a calculator. Children at school need this memory on a daily basis for a variety of tasks such as following teachers' instructions or remembering sentences they have been asked to write down.
The main goal of this article was to investigate the predictive power of working memory and IQ in learning in typically developing children over a six-year period. This issue is important because distinguishing between the cognitive skills underpinning success in learning is crucial for early screening and intervention.
In this study, typically developing students were tested for their IQ and working memory at 5 years old and again when they were 11 years old. They were also tested on their academic attainments in reading, spelling and maths.
The findings revealed that a child's success in all aspects of learning is down to how good their working memory is regardless of IQ score. Critically, working memory at the start of formal education is a more powerful predictor of subsequent academic success than IQ in the early years.
This unique finding is important as it addresses concerns that general intelligence, still viewed as a key predictor of academic success, is unreliable. An individual can have an average IQ score but perform poorly in learning.
Some psychologists suggest that the link between IQ and learning is greatest when the individual is learning new information, rather than at later stages when it is suggested that gains made are the result of practice.
Yet the findings from this research that working memory capacity predicted subsequent skills in reading, spelling, and math suggests that some cognitive skills contribute to learning beyond practice effects.
The study also found that, as opposed to IQ, working memory is not linked to the parents' level of education or socio-economic background. This means all children regardless of background or environmental influence can have the same opportunities to fulfil potential if working memory is assessed and problems addressed where necessary.
Working memory is a relatively stable construct that has powerful implications for academic success. While working memory does increase with age, its relative capacity remains constant. This means that a child at the bottom 10 percentile compared to their same-aged peers is likely to remain at this level throughout their academic career.
In summary, the present article suggests that the traditional reliance on IQ as a benchmark for academic success may be misguided. Instead, schools should focus on assessing working memory as it is the best predictor of reading, spelling and math skills six years later. At present, poor working memory is rarely identified by teachers, who often describe children with this problem as inattentive or as having lower levels of intelligence. However, there are standardized assessments that are suitable for educators to use to screen their students for working memory problems. For example, the Automated Working Memory Assessment (published by the Psychological Corporation) allows non-specialist assessors such as classroom teachers to screen their students for significant working memory problems quickly and effectively.
Problems with working memory can be easily addressed in schools-an advantage over IQ which is more difficult to influence by teachers. Early intervention in working memory could lead to a reduction in the number of those failing schools and help address the problem of under-achievement in schools.
ReferenceAlloway, T.P. & Alloway, R. G. (2010). Investigating the predictive roles of working memory and IQ in academic attainment. Journal of Experimental Child Psychology, 106, 20-29.
