Sometimes, adolescents just can’t resist

Don’t get mad the next time you catch your teenager texting when he promised to be studying.

He simply may not be able to resist.

A University of Iowa study found teenagers are far more sensitive than adults to the immediate effect or reward of their behaviors. The findings may help explain, for example, why the initial rush of texting may be more enticing for adolescents than the long-term payoff of studying.

“The rewards have a strong, perceptional draw and are more enticing to the teenager,” says Jatin Vaidya, a professor of psychiatry at the UI and corresponding author of the study, which appeared online this week in the journal Psychological Science. “Even when a behavior is no longer in a teenager’s best interest to continue, they will because the effect of the reward is still there and lasts much longer in adolescents than in adults.”

For parents, that means limiting distractions so teenagers can make better choices. Take the homework and social media dilemma: At 9 p.m., shut off everything except a computer that has no access to Facebook or Twitter, the researchers advise.

“I’m not saying they shouldn’t be allowed access to technology,” Vaidya says. “But they need help in regulating their attention so they can develop those impulse-control skills.”

In their study, “Value-Driven Attentional Capture in Adolescence,” Vaidya and co-authors Shaun Vecera, a professor of psychology, and Zachary Roper, a graduate student in psychology, note researchers generally believe teenagers are impulsive, make bad decisions, and engage in risky behavior because the frontal lobes of their brains are not fully developed.

But the UI researchers wondered whether something more fundamental was going on with adolescents to trigger behaviors independent of higher-level reasoning.

“We wanted to try to understand the brain’s reward system and how it changes from childhood to adulthood,” says Vaidya, who adds the reward trait in the human brain is much more primitive than decision-making. “We’ve been trying to understand the reward process in adolescence and whether there is more to adolescent behavior than an under-developed frontal lobe,” he adds.

For their study, the researchers recruited 40 adolescents, ages 13 and 16, and 40 adults, ages 20 and 35. First, participants were asked to find a red or green ring hidden within an array of rings on a computer screen. Once identified, they reported whether the white line inside the ring was vertical or horizontal. If they were right, they received a reward between 2 and 10 cents, depending on the color. For some participants, the red ring paid the highest reward; for others, it was the green. None was told which color would pay the most.

After 240 trials, the participants were asked whether they noticed anything about the colors. Most made no association between a color and reward, which researchers say proves the ring exercise didn’t involve high-level, decision-making.

In the next stage, participants showed they had developed an intuitive association when they were asked to find a diamond-shaped target. This time, the red and green rings were used as decoys.

At first, the adolescents and adults selected the color ring that garnered them the highest monetary reward, the goal of the first trial. But in short order, the adults adjusted and selected the diamond. The adolescents did not.

Even after 240 trials, the adolescents were still more apt to pick the colored rings.

“Even though you’ve told them, ‘You have a new target,’ the adolescents can’t get rid of the association they learned before,” Vecera says. “It’s as if that association is much more potent for the adolescent than for the adult.

“If you give the adolescent a reward, it will persist longer,” he adds. “The fact that the reward is gone doesn’t matter. They will act as if the reward is still there.”

Researchers say that inability to readily adjust behavior explains why, for example, a teenager may continue to make inappropriate comments in class long after friends stopped laughing.

In the future, researchers hope to delve into the psychological and neurological aspects of their results.

“Are there certain brain regions or circuits that continue to develop from adolescence to adulthood that play role in directing attention away from reward stimuli that are not task relevant?” Vaidya asks. “Also, what sort of life experiences and skill help to improve performance on this task?”

Zebrafish Model of a Learning and Memory Disorder Shows Better Way to Target Treatment

Using a zebrafish model of a human genetic disease called neurofibromatosis (NF1), a team from the Perelman School of Medicine at the University of Pennsylvania has found that the learning and memory components of the disorder are distinct features that will likely need different treatment approaches. They published their results this month in Cell Reports.

NF1 is one of the most common inherited neurological disorders, affecting about one in 3,000 people. It is characterized by tumors, attention deficits, and learning problems. Most people with NF1 have symptoms before the age of 10. Therapies target Ras, a protein family that guides cell proliferation. The NF1 gene encodes neurofibromin, a very large protein with a small domain involved in Ras regulation.

Unexpectedly, the Penn team showed that some of the behavioral defects in mutant fish are not related to abnormal Ras, but can be corrected by drugs that affect another signaling pathway controlled by the small molecule cAMP. They used the zebrafish model of NF1 to show that memory defects – such as the recall of a learned task — can be corrected by drugs that target Ras, while learning deficits are corrected by modulation of the cAMP pathway. Overall, the team’s results have implications for potential therapies in people with NF1.

“We now know that learning and memory defects in NF1 are distinct and potentially amenable to drug therapy,” says co-senior author Jon Epstein, MD, chair of the department of Cell and Developmental Biology. “Our data convincingly show that memory defects in mutant fish are due to abnormal Ras activity, but learning defects are completely unaffected by modulation of these pathways. Rather these deficits are corrected with medicines that modulate cAMP.”

Over the last 20 years, zebrafish have become great models for studying development and disease. Like humans, zebrafish are vertebrates, and most of the genes required for normal embryonic development in zebrafish are also present in humans. When incorrectly regulated, these same genes often cause tumor formation and metastatic cancers.

Zebrafish have also become an ideal model for studying vertebrate neuroscience and behavior. In fact, co-senior author Michael Granato, PhD, professor of Cell and Developmental Biology, has developed the first high-throughput behavioral assays that measure learning and memory in fish. For example, Granato explains, “normal fish startle with changes in noise and light level by bending and swimming away from the annoying stimuli and do eventually habituate, that is get used to the alternations in their environment. But, NF1 fish mutants fail to habituate. However, after adding cAMP to their water, they do learn, and then behave like the non-mutant fish.”

This clearly indicates that learning deficits in the NF1 mutant fish are corrected by adding various substances that boost cAMP signaling. “Our data also indicate that learning and memory defects are reversible with acute pharmacologic treatments and are therefore not hard-wired, as might be expected for a defect in the development of nerves,” says Epstein. “This offers great hope for therapeutic intervention for NF1 patients.”

Memory in silent neurons

When we learn, we associate a sensory experience either with other stimuli or with a certain type of behaviour. The neurons in the cerebral cortex that transmit the information modify the synaptic connections that they have with the other neurons. According to a generally-accepted model of synaptic plasticity, a neuron that communicates with others of the same kind emits an electrical impulse as well as activating its synapses transiently. This electrical pulse, combined with the signal received from other neurons, acts to stimulate the synapses. How is it that some neurons are caught up in the communication interplay even when they are barely connected? This is the crucial chicken-or-egg puzzle of synaptic plasticity that a team led by Anthony Holtmaat, professor in the Department of Basic Neurosciences in the Faculty of Medicine at UNIGE, is aiming to solve. The results of their research into memory in silent neurons can be found in the latest edition of Nature.

Learning and memory are governed by a mechanism of sustainable synaptic strengthening. When we embark on a learning experience, our brain associates a sensory experience either with other stimuli or with a certain form of behaviour. The neurons in the cerebral cortex responsible for ensuring the transmission of the relevant information, then modify the synaptic connections that they have with other neurons. This is the very arrangement that subsequently enables the brain to optimise the way information is processed when it is met again, as well as predicting its consequences.

Neuroscientists typically induce electrical pulses in the neurons artificially in order to perform research on synaptic mechanisms.

The neuroscientists from UNIGE, however, chose a different approach in their attempt to discover what happens naturally in the neurons when they receive sensory stimuli. They observed the cerebral cortices of mice whose whiskers were repeatedly stimulated mechanically without an artificially-induced electrical pulse. The rodents use their whiskers as a sensor for navigating and interacting; they are, therefore, a key element for perception in mice.

An extremely low signal is enough

By observing these natural stimuli, professor Holtmaat’s team was able to demonstrate that sensory stimulus alone can generate long-term synaptic strengthening without the neuron discharging either an induced or natural electrical pulse. As a result – and contrary to what was previously believed – the synapses will be strengthened even when the neurons involved in a stimulus remain silent.In addition, if the sensory stimulation lasts over time, the synapses become so strong that the neuron in turn is activated and becomes fully engaged in the neural network. Once activated, the neuron can then further strengthen the synapses in a forwards and backwards movement. These findings could solve the brain’s “What came first?” mystery, as they make it possible to examine all the synaptic pathways that contribute to memory, rather than focusing on whether it is the synapsis or the neuron that activates the other.

The entire brain is mobilised

A second discovery lay in store for the researchers. During the same experiment, they were also able to establish that the stimuli that were most effective in strengthening the synapses came from secondary, non-cortical brain regions rather than major cortical pathways (which convey actual sensory information). Accordingly, storing information would simply require the co-activation of several synaptic pathways in the neuron, even if the latter remains silent. These findings may also have important implications both for the way we understand learning mechanisms and for therapeutic possibilities, in particular for rehabilitation following a stroke or in neurodegenerative disorders. As professor Holtmaat explains: “It is possible that sensory stimulation, when combined with another activity (motor activity, for example), works better for strengthening synaptic connections”. The professor concludes: “In the context of therapy, you could combine two different stimuli as a way of enhancing the effectiveness.”

Scientists Discover Why Learning Tasks Can Be Difficult

Learning a new skill is easier when it is related to an ability we already have. For example, a trained pianist can learn a new melody easier than learning how to hit a tennis serve.

Scientists from the Center for the Neural Basis of Cognition (CNBC) — a joint program between Carnegie Mellon University and the University of Pittsburgh — have discovered a fundamental constraint in the brain that may explain why this happens. Published as the cover story in the Aug. 28, 2014, issue of Nature, they found for the first time that there are limitations on how adaptable the brain is during learning and that these restrictions are a key determinant for whether a new skill will be easy or difficult to learn. Understanding the ways in which the brain’s activity can be “flexed” during learning could eventually be used to develop better treatments for stroke and other brain injuries.

Lead author Patrick T. Sadtler, a Ph.D. candidate in Pitt’s Department of Bioengineering, compared the study’s findings to cooking.

"Suppose you have flour, sugar, baking soda, eggs, salt and milk. You can combine them to make different items - bread, pancakes and cookies — but it would be difficult to make hamburger patties with the existing ingredients," Sadtler said. "We found that the brain works in a similar way during learning. We found that subjects were able to more readily recombine familiar activity patterns in new ways relative to creating entirely novel patterns."

For the study, the research team trained animals to use a brain-computer interface (BCI), similar to ones that have shown recent promise in clinical trials for assisting quadriplegics and amputees.

"This evolving technology is a powerful tool for brain research," said Daofen Chen, program director at the National Institute of Neurological Disorders and Stroke (NINDS), part of the National Institutes of Health (NIH), which supported this research. "It helps scientists study the dynamics of brain circuits that may explain the neural basis of learning."

The researchers recorded neural activity in the subject’s motor cortex and directed the recordings into a computer, which translated the activity into movement of a cursor on the computer screen. This technique allowed the team to specify the activity patterns that would move the cursor. The test subjects’ goal was to move the cursor to targets on the screen, which required them to generate the patterns of neural activity that the experimenters had requested. If the subjects could move the cursor well, that meant that they had learned to generate the neural activity pattern that the researchers had specified.

The results showed that the subjects learned to generate some neural activity patterns more easily than others, since they only sometimes achieved accurate cursor movements. The harder-to-learn patterns were different from any of the pre-existing patterns, whereas the easier-to-learn patterns were combinations of pre-existing brain patterns. Because the existing brain patterns likely reflect how the neurons are interconnected, the results suggest that the connectivity among neurons shapes learning.

"We wanted to study how the brain changes its activity when you learn, and also how its activity cannot change. Cognitive flexibility has a limit — and we wanted to find out what that limit looks like in terms of neurons," said Aaron P. Batista, assistant professor of bioengineering at Pitt.

Byron M. Yu, assistant professor of electrical and computer engineering and biomedical engineering at Carnegie Mellon, believes this work demonstrates the utility of BCI for basic scientific studies that will eventually impact people’s lives.

"These findings could be the basis for novel rehabilitation procedures for the many neural disorders that are characterized by improper neural activity," Yu said. "Restoring function might require a person to generate a new pattern of neural activity. We could use techniques similar to what were used in this study to coach patients to generate proper neural activity."

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New research sheds light on how children’s brains memorize facts

The scientists also saw changes in the degree to which the hippocampus was connected to other parts of children’s brains, with several parts of the prefrontal, anterior temporal cortex and parietal cortex more strongly connected to the hippocampus after one year. Crucially, the stronger these connections, the greater was each individual child’s ability to retrieve math facts from memory, a finding that suggests a starting point for future studies of math-learning disabilities.

Although children were using their hippocampus more after a year, adolescents and adults made minimal use of their hippocampus while solving math problems. Instead, they pulled math facts from well-developed information stores in the neocortex.

Memory scaffold

“What this means is that the hippocampus is providing a scaffold for learning and consolidating facts into long-term memory in children,” said Menon, who is also the Rachel L. and Walter F. Nichols, MD, Professor at the medical school. Children’s brains are building a schema for mathematical knowledge. The hippocampus helps support other parts of the brain as adultlike neural connections for solving math problems are being constructed. “In adults this scaffold is not needed because memory for math facts has most likely been consolidated into the neocortex,” he said. Interestingly, the research also showed that, although the adult hippocampus is not as strongly engaged as in children, it seems to keep a backup copy of the math information that adults usually draw from the neocortex.

The researchers compared the level of variation in patterns of brain activity as children, adolescents and adults correctly solved math problems. The brain’s activity patterns were more stable in adolescents and adults than in children, suggesting that as the brain gets better at solving math problems its activity becomes more consistent.

The next step, Menon said, is to compare the new findings about normal math learning to what happens in children with math-learning disabilities.

“In children with math-learning disabilities, we know that the ability to retrieve facts fluently is a basic problem, and remains a bottleneck for them in high school and college,” he said. “Is it that the hippocampus can’t provide a reliable scaffold to build good representations of math facts in other parts of the brain during the early stages of learning, and so the child continues to use inefficient strategies to solve math problems? We want to test this.”

Musical Training Offsets Some Academic Achievement Gaps

Learning to play a musical instrument or to sing can help disadvantaged children strengthen their reading and language skills, according to research presented at the American Psychological Association’s 122nd Annual Convention.

The findings, which involved hundreds of kids participating in musical training programs in Chicago and Los Angeles public schools, highlight the role learning music can have on the brains of youth in impoverished areas, according to presenter Nina Kraus, PhD, a neurobiologist at Northwestern University.

“Research has shown that there are differences in the brains of children raised in impoverished environments that affect their ability to learn,” said Kraus. “While more affluent students do better in school than children from lower income backgrounds, we are finding that musical training can alter the nervous system to create a better learner and help offset this academic gap.” Up until now, research on the impact of musical training has been primarily conducted on middle- to upper-income music students participating in private music lessons, she said.

Kraus’s lab research has concluded that musical training appears to enhance the way children’s nervous systems process sounds in a busy environment, such as a classroom or a playground. This improved neural function may lead to enhanced memory and attention spans which, in turn, allow kids to focus better in the classroom and improve their communication skills, she said.

Many of Kraus’s study participants are part of the Harmony Project in Los Angeles, which was founded by fellow presenter Margaret Martin, DrPH. In her most recent research, Kraus studied children beginning when they were in first and second grade. Half participated in musical training and the other half were randomly selected from the program’s lengthy waiting list and received no musical training during the first year of the study. Children who had no musical training had diminished reading scores while Harmony Project participants’ reading scores remained unchanged over the same time span. 

Kraus’s lab also found that, after two years, neural responses to sound in adolescent music students were faster and more precise than in students in another type of enrichment class. The researchers tested the auditory abilities in adolescents from lower economic backgrounds at three public high schools in Chicago. Over two years, half of the students participated in either band or choir during each school day while the other half were enrolled in Junior Reserve Officer’s Training Corps classes, which teaches character education, achievement, wellness, leadership and diversity. All participants had comparable reading ability and IQs at the start of the study. The researchers recorded the children’s brain waves as they listened to a repeated syllable against soft background sound, which made it harder for the brain to process. The researchers repeated measures after one year and again at the two-year mark. They found music students’ neural responses had strengthened while the JROTC students’ responses had remained the same. Interestingly, the differences in the music students’ brain waves in response to sounds as described above occurred after two years but not at one year, which showed that these programs cannot be used as quick fixes, Kraus said. This is the strongest evidence to date that public school music education in lower-income students can lead to better sound processing in the brain when compared to other types of enrichment education, she added.

Even after the lessons stop, the brain still reaps benefits, according to studies on the long-term benefits of music lessons. In one study, Kraus’s team surveyed college students and asked them how many years they had music training. As they found with the elementary school students, college students who had more than five years of musical training in elementary school or high school had improved neural responses to sound when compared to college students who had had no musical training.

The Harmony Project provides instruments for the students who participate five or more hours a week in musical instruction and ensemble rehearsals. The project is year-round and tuition-free based on income, said Martin. Many of the programs build full-time bands in neighborhoods where the students live and the students agree to commit to the program from elementary school through high school, she said.

“We’re spending millions of dollars on drugs to help kids focus and here we have a non-pharmacologic intervention that thousands of disadvantaged kids devote themselves to in their non-school hours — that works,” Martin said. “Learning to make music appears to remodel our kids’ brains in ways that facilitates and improves their ability to learn.”

The Harmony Project has launched programs in other urban school districts, including Miami, New Orleans, Tulsa, Oklahoma, Kansas City, Missouri and Ventura, California.

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