Category: ADD and ADHD

Medication and behavioural interventions help children with attention deficit hyperactivity disorder (ADHD) better maintain attention and self-control by normalising activity in the same brain systems, according to research funded by the Wellcome Trust.

In a study published in the journal Biological Psychiatry, researchers from the University of Nottingham show that medication has the most significant effect on brain function in children with ADHD, but this effect can be boosted by complementary use of rewards and incentives, which appear to mimic the effects of medication on brain systems.

ADHD is the most common mental health disorder in childhood, affecting around one in 20 children in the UK. Children with ADHD are excessively restless, impulsive and distractible, and experience difficulties at home and in school. Although no cure exists for the condition, symptoms can be reduced by a combination of medication and behaviour therapy.

Methylphenidate, a drug commonly used to treat ADHD, is believed to increase levels of dopamine in the brain. Dopamine is a chemical messenger associated with attention, learning and the brain's reward and pleasure systems. This increase amplifies certain brain signals and can be measured using an electroencephalogram (EEG). Until now it has been unclear how rewards and incentives affect the brain, either with or without the additional use of medication.

To answer these questions, researchers at Nottingham's Motivation, Inhibition and Development in ADHD Study (MIDAS) used EEG to measure brain activity while children played a simple game. They compared two particular markers of brain activity that relate to attention and impulsivity, and looked at how these were affected by medication and motivational incentives.

The team worked with two groups of children aged nine to 15: one group of 28 children with ADHD and a control group of 28. The children played a computer game in which green aliens were randomly interspersed with less frequent black aliens, each appearing for a short interval. Their task was to 'catch' as many green aliens as possible, while avoiding catching black aliens. For each slow or missed response, they would lose one point; they would gain one point for each timely response.

In a test designed to study the effect of incentives, the reward for avoiding catching the black alien was increased to five points; a follow-up test replaced this reward with a five-point penalty for catching the wrong alien.

The researchers found that when given their usual dose of methylphenidate, children with ADHD performed significantly better at the tasks than when given no medication, with better attention and reduced impulsivity. Their brain activity appeared to normalise, becoming similar to that of the control group.

Similarly, motivational incentives also helped to normalise brain activity on the two EEG markers and improved attention and reduced impulsivity, though its effect was much smaller than that of medication.

"When the children were given rewards or penalties, their attention and self-control was much improved," says Dr Maddie Groom, first author of the study. "We suspect that both medication and motivational incentives work by making a task more appealing, capturing the child's attention and engaging his or her brain response control systems."

Professor Chris Hollis, who led the study, believes the findings may help to reconcile the often-polarised debate between those who advocate either medication on the one hand, or psychological/behavioural therapy on the other.

"Although medication and behaviour therapy appear to be two very different approaches of treating ADHD, our study suggests that both types of intervention may have much in common in terms of their affect on the brain," he says. "Both help normalise similar components of brain function and improve performance. What's more, their effect is additive, meaning they can be more effective when used together."

The researchers believe that the results lend support from neuroscience to current treatment guidelines for ADHD as set out by the National Institute for Health and Clinical Excellence (NICE). These recommend that behavioural interventions, which have a smaller effect size, are appropriate for moderate ADHD, while medication, with its larger effect size, is added for severe ADHD.

Although the findings suggest that a combination of incentives and medication might work most effectively, and potentially enable children to take lower doses of medication, Professor Hollis believes more work is needed before the results can be applied to everyday clinical practice or classroom situations.

"The incentives and rewards in our study were immediate and consistent, but we know that children with ADHD respond disproportionately less well to delayed rewards," he says. "This could mean that in the 'real world' of the classroom or home, the neural effects of behavioural approaches using reinforcement and rewards may be less effective."

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Journal Reference:

1. Madeleine J. Groom, Gaia Scerif, Peter F. Liddle, Martin J. Batty, Elizabeth B. Liddle, Katherine L. Roberts, John D. Cahill, Mario Liotti, Chris Hollis. Effects of Motivation and Medication on Electrophysiological Markers of Response Inhibition in Children with Attention-Deficit/Hyperactivity Disorder. Biological Psychiatry, 2010; 67 (7): 624 DOI: 10.1016/j.biopsych.2009.09.029

Mount Sinai researchers have learned that meta-cognitive therapy (MCT), a method of skills teaching by use of cognitive-behavioral principles, yielded significantly greater improvements in symptoms of attention deficit hyperactivity disorder (ADHD) in adults than those that participate in supportive therapy.

The study is now published in the American Journal of Psychiatry.

Mary Solanto, Ph.D., Associate Professor in the Department of Psychiatry and Director of the Attention Deficit/Hyperactivity Disorder Center at The Mount Sinai Medical Center examined the effectiveness of a 12-week meta-cognitive therapy group. The intervention was intended to enhance time management, organizational, and planning skills/abilities in adults with ADHD.

"We observed adults with ADHD who were assigned randomly to receive either meta-cognitive therapy or a support group," said Dr. Solanto. "This is the first time we have demonstrated efficacy of a non-medication treatment for adult ADHD in a study that compared the active treatment against a control group that was equivalent in therapist time, attention, and support."

The study observed 88 adults with rigorously diagnosed ADHD, who were selected following structured diagnostic interviews and standardized questionnaires. Participants were randomly assigned to receive meta-cognitive therapy or supportive psychotherapy in a group setting. Groups were equated for ADHD medication use.

Participants were evaluated by an independent (blind) clinician using a standardized interview assessment of core inattentive symptoms and a subset of symptoms related to time-management and organization. After 12 weeks, the MCT group members were significantly more improved than those in the support group. The MCT group was also more improved on self-ratings and observer ratings of these symptoms.

Meta-cognitive therapy uses cognitive-behavioral principles and methods to teach skills and strategies in time management, organization, and planning. Also targeted were depressed and anxious thoughts and ideas that undermine effective self-management. The supportive therapy group matched the MCT group with respect to the nonspecific aspects of treatment, such as providing support for the participants, while avoiding discussion of time management, organization, and planning strategies.

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Journal Reference:

1. Solanto, M., Marks, D and Wasserstein, J et al. Meta-Cognitive Therapy. American Journal of Psychiatry, 2010

 A new study suggests a trend toward developing hyperactivity among typically developing elementary-school-aged siblings of autistic preschoolers and supports the notion that mothers of young, autistic children experience more depression and stress than mothers with typically developing children.

While the impact on older siblings was not statistically significant, the trend may indicate the presence of symptoms associated with broader observable autism characteristics seen in previous studies, says Laura Lee McIntyre, a professor and director of the University of Oregon's school psychology program. The study was published in the March issue of the journal Focus on Autism and Other Developmental Disabilities.

Previous research projects have netted mixed findings, but many suggest that families dealing with autism — especially brothers and sisters of an autistic child — also experience symptoms similar to autism: widespread abnormalities of social interactions, communication and behavior.

The new study gives a fresh look at autism's early effects on families by comparing control and experimental groups whose ages, education and socioeconomic situations were virtually identical. Twenty families had a preschooler (ages 2-5 years old) diagnosed with autism and a typically developing older elementary school sibling (6-10); the control group of 23 families did not have an autistic child. Older children with diagnosed learning or mental disabilities were excluded.

"We know there are risk factors, but we don't know if they result from having a child with autism, or if there are genetic predispositions as part of the broader autism picture," McIntyre said. "Are these difficulties the result of child-rearing challenges, or are they negatively impacted because of shared genetic risks? Our sample was very clean, and that's good for science but not necessarily as good for generalizing our findings, but I'm confident with the results we found in this particular sample."

McIntyre, while a professor at Syracuse University, and her doctoral student Nicole Quintero studied families chosen in New York. They looked closely at sibling adjustments, involving social, behavioral and academic performance as recorded by both parents and teachers, and at the well- being of the mothers, whose average age was 36 and 94-95 percent of whom were married. The median age of older siblings was seven and most were first- or second-graders.

"Contrary to what has been found by many researchers, we found that older siblings were pretty well adjusted, with no significant differences in parent-reported or teacher-reported social skills," said McIntyre, who joined the UO's department of special education and clinical sciences in 2009. "These are all typically developing kids."

Teachers, however, reported slightly more behavioral problems for the siblings of children with autism than control siblings. "There was a trend toward significance," she said.

The problems resembled hyperactivity but not at levels generally attributed to attention-deficit hyperactive disorder (ADHD). Teacher reports noted that these children exhibited slightly more fidgeting, movement and attention problems.

"Children with siblings with autism may be experiencing some sub-clinical symptoms of hyperactivity or attention problems," noted McIntyre, an affiliate of the UO's Center for Excellence and Developmental Disabilities, Education, Research and Service. "Parents didn't report seeing such things at home. Teachers see these children in a more structured environment. Siblings of children with autism may be at heightened risk for developing problems, potentially over time."

Siblings of children with autism probably should be watched with appropriate academic supports in place, she said. "Our findings are rather positive overall, but these kids should be on our radar screens. These kids may start school OK, at least those from healthy families, but they may demonstrate difficulties over time. However, it has been shown that around 30 percent of siblings of autistic children have some associated difficulties in behavior, learning or development."

The finding that moms with children with autism were more stressed and depressed in comparison to moms of typically developing preschool children "was not surprising at all," McIntyre said. "That finding is robust in existing literature, so even though this sample involves highly organized, motivated and willing mothers, in comparison to other moms with two or more children, they are reporting more stress and more depression."

Mothers of autistic children, she added, need assistance for day-to-day child-rearing activities to give them some time to be individuals. As part of her research and clinical work at UO's nationally recognized Child and Family Center, she is looking at interventions that support parents and help kids with their daily living skills and behavior management.

The research was partially funded by the National Institute of Child Health and Human Development. Quintero is now a postdoctoral researcher in the University of Illinois at Chicago in the Institute on Disability and Human Development.

Although it's typically considered an adolescent curse, ADHD actually affects about five percent of adults as well. New research in a mouse model of attention deficit/hyperactivity disorder suggests that the root of the psychiatric disorder might be the over-activity of a protein that regulates dopaminergic pathways. The work suggests a path toward new treatments for symptoms including inattentiveness, over-activity and impulsivity.

The cause of ADHD is unknown, but there is increasing evidence that dopamine, a neurotransmitter involved in the brain's reward-motivation system, is involved. Scientists have found that the level of dopamine, and the D2 receptor it binds to, are involved in the progression of ADHD, as well as four connected regions in the frontal region of the brain, two of which are directly linked to reward and motivation.

The Rockefeller University researchers, led by Marc Flajolet, a senior research associate, and Paul Greengard, Vincent Astor Professor and head of the Laboratory of Molecular and Cellular Neuroscience, focused on an enzyme called casein kinase I (CK1), which is involved in regulating the dopamine signaling pathway. The work was published in January in the Proceedings of the National Academy of Sciences.

Flajolet and coauthor Ming-Ming Zhou, a research associate in the lab, created a line of mice genetically modified to overexpress a form of CK1, called CK1δ, specifically in the forebrain of the mouse. Under normal conditions and in response to stimulation by drugs such as the ones used today to treat ADHD, the mice that overexpress CK1δ show behavioral symptoms and responses to drugs similar to those observed in people with ADHD.

"The genetically modified mice that we generated present interesting features such as hyperactivity and altered nesting capacities that might be related to attention deficit, and possibly altered impulsivity," says Flajolet.

To test the nesting capacities, the mice were kept overnight, singly housed in an open field arena, with pressed cotton nesting material. After 24 hours, the scientists compared the overall quality of the nests and the amount of material, if any, that each mouse used to build its nest. The normal mice tore up the pressed cotton and slept in the nests, while the CK1δ-overexpressing mice barely touched the cotton material.

The researchers also found that the CK1δ-overexpressing mice became less hyper in response to amphetamine and methylphenidate (Ritalin) in a way similar to that of ADHD patients. Finally, biochemical studies by Postdoctoral Associate Heike Rebholz showed that both classes of dopamine receptors, D1R and D2R, are significantly reduced in the CK1δ-overexpressing mice, further evidence that the dopaminergic system is severely affected.

"We believe that overexpression of CK1δ induces some developmental steps that resemble what might be happening in ADHD patients and therefore we propose that the CK1δ-overexpressing mice are a model for this disorder," says Flajolet. "It will be interesting to investigate if CK1 could be the origin of developmental defects in humans that lead to ADHD."

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Journal Reference:

1. Zhou et al. Forebrain overexpression of CK1δ leads to down-regulation of dopamine receptors and altered locomotor activity reminiscent of ADHD. Proceedings of the National Academy of Sciences, 2010; DOI: 10.1073/pnas.0915173107

Until now, attention-deficit/hyperactivity disorder (ADHD) was related to alterations in the brain affecting attention and cognitive processes. Researchers at Universitat Autònoma de Barcelona and the Vall d'Hebron University Hospital have now discovered anomalies in the brain's reward system related to the neural circuits of motivation and gratification. In children with ADHD, the degree of motivation when carrying out an activity is related to the immediacy with which the objectives of the activity are met. This would explain why their attention and hyperactivity levels differ depending on the tasks being carried out.

Susanna Carmona, researcher at the Cognitive Neuroscience Unit of the UAB Department of Psychiatry and Legal Medicine (URNC-IAPS-Hospital del Mar), has worked in collaboration with clinical researchers of the Vall d'Hebron University Hospital on the first research which relates the structure of the brain's reward system, the ventral striatum, with clinical symptoms in children suffering from ADHD.

Models describing the origin of ADHD tend to emphasise the relevance of attention processes and of the cognitive functions which guide our mental processes in achieving proposed objectives. Nevertheless, recent research has focused on neural gratification/pleasure circuits, which can be found in what is known as the brain's reward system, with the nucleus accumbens as the central part of this system.

The nucleus accumbens is in charge of maintaining levels of motivation when commencing a task and continues to do so until reaching what experts name the "reinforcement," the proposed objective. This motivation can be maintained throughout time, even when the gratification obtained is not immediate. However, in children with ADHD motivational levels seem to drop rapidly and there is a need for immediate reinforcements to continue persisting in their efforts.

In this study, researchers selected a sample of 84 participants aged 6 to 18 years and divided them according to presence of ADHD symptoms, with one experimental group of 42 children with ADHD and one control group of 42 children with no signs of mental or behavioural anomalies, paired by sex and age. Magnetic resonance images were taken of all participants to view the structure of their brains. Of these images, the cerebral region corresponding to the ventral striatum, which includes the nucleus accumbens, was demarcated.

Differences in the structure of the ventral striatum — particularly on the right-hand side — could be seen between those with ADHD and those without the disorder. Children with ADHD exhibited reduced volumes in this region. These differences were associated with symptoms of hyperactivity and impulsiveness.

The obtained data corroborate results from previous studies carried out with animals: the importance of the reward system, as well as the relation between nucleus accumbens, impulsive behaviour and the development of motor hyperactivity. This leads researchers to consider that ADHD is not only caused by brain alterations affecting cognitive processes, but also by anomalies which cause motivational deficiencies. This would explain the imbalance in levels of attention and hyperactivity in a child with ADHD depending on his or her motivation when engaged in a specific task and the immediacy of the gratification/pleasure while carrying it out.

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Journal Reference:

1. Carmona et al. Ventro-Striatal Reductions Underpin Symptoms of Hyperactivity and Impulsivity in Attention-Deficit/Hyperactivity Disorder. Biological Psychiatry, 2009; 66 (10): 972 DOI: 10.1016/j.biopsych.2009.05.013

ADHD, or attention-deficit/hyperactivity disorder, is among the costliest of behavioral disorders. Its combination of inattention, impulsivity and hyperactivity leads to accidental injuries, school failure, substance abuse, antisocial behavior and more. Yet despite nearly a century of study, the disorder’s roots remain mysterious.

Much of modern ADHD research has focused on heritability of the condition, and indeed evidence suggests that genes may account for as much as 70 percent of hyperactivity and inattention in children. But that leaves 30 percent unexplained, so recently the focus has shifted to the environment. What is it that triggers an underlying susceptibility and changes it into a full-blown disorder? New research suggests that the culprit may be an old villain—lead—and what’s more it explains the causal pathway from exposure to disability.

Lead is a neurotoxin. This has been known for a long time, and in fact government regulation drastically reduced environmental lead a generation ago. But regulating automobile fuel and paint didn’t entirely eliminate lead from the environment. It’s found in trace amounts in everything from children’s costume jewelry to imported candies to soil and drinking water. Every American today is exposed to low levels of the metal, and indeed nearly all children have measureable levels of lead in their bodies. According to psychological scientist Joel Nigg of the Oregon Health & Science University, this universal low-level exposure makes lead an ideal candidate for the disorder’s trigger.

This was just a theory until quite recently, but two recent studies now provide strong evidence. The first study compared children formally diagnosed with ADHD to controls, and found that the children with the disorder had slightly higher levels of lead in their blood. This study showed a link only between blood lead and hyperactivity/impulsivity symptoms, not inattention. But a second study showed a robust link between blood lead and both parent and teacher ratings of ADHD symptoms, including both hyperactivity and attention problems. In both studies, the connection was independent of IQ, family income, race, or maternal smoking during pregnancy.

Nigg offers a causal model for the disabling symptoms associated with ADHD: Lead attaches to sites in the brain’s striatum and frontal cortex, where it acts on the genes in these regions—causing them to turn on or remain inactive. Gene activity shapes the development and activity of these brain regions. By disrupting brain activity, the toxin in turn alters psychological processes supported by these neurons, notably cognitive control. Finally, diminished cognitive control contributes to hyperactivity and lack of vigilance.

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Journal Reference:

1. Joel Nigg. Attention-Deficit/Hyperactivity Disorder: Endophenotypes, Structure, and Etiological Pathways. Current Directions in Psychological Science, February, 2010

The adverse effects of prenatal alcohol exposure on behavioral, cognitive, and social development can lead to a range of symptoms referred to as fetal alcohol spectrum disorder (FASD). Attention and cognition problems seen in individuals with a history of prenatal alcohol exposure often resemble those linked to attention deficit hyperactivity disorder (ADHD). An assessment of these disorders has found that while children with FASD may meet the behavioral criteria for ADHD, their attention difficulties differ in subtle but important respects.

Results will be published in the April 2010 issue of Alcoholism: Clinical & Experimental Research and are currently available at Early View.

"ADHD is clinically diagnosed primarily on the basis of observations by the parent, teacher, and clinician regarding the degree to which a child exhibits specific behavioral symptoms, such as difficulty sustaining attention to and completing tasks or play activities, failure to listen when spoken to directly, impulsivity, talking out of turn, or difficulty sitting still," explained Joseph Jacobson, professor at Wayne State University School of Medicine and the study's corresponding author. "A large proportion of children with a history of prenatal alcohol exposure exhibits these behavioral characteristics and, therefore, may meet the criteria for a diagnosis of ADHD."

Jacobson and his colleagues examined event-related potentials (ERPs), which reflect changes in the brain's electrical activity in response to a particular stimulus or condition, in 102 (54 women, 48 men) 19-year-olds. All of the young adults performed a Go/No-go task, which requires the participant to attend and respond selectively to non-target stimuli (Go) and inhibit responses to a target stimulus (No-go).

Jacobson explained how the Go/No-go task was used in this study. "The participant is instructed to press a button whenever a letter appears on the screen except when the letter X appears," he said. "The participant gets into the routine of pressing the button as the letters appear on the screen. Once the rhythm of button pressing is established, individuals with ADHD find it more difficult to inhibit or hold back their impulse to press the button when the X appears and make more errors on the task regardless of whether or not they were exposed prenatally to alcohol."

While participants with childhood ADHD, regardless of their prenatal alcohol exposure, were less accurate at inhibiting responses, only the ADHD group without prenatal alcohol exposure showed a unique ERP brain wave pattern, which may reflect a more effortful strategy related to inhibitory control.

"This difference was seen in the P3 ERP brain wave component, which has been found in other studies to reflect the mental effort or heightened attention exerted in performing a task; thus, the more difficult or cognitively challenging the task, the larger the P3 brain wave," said Jacobson. "The typical response, which was seen both in the young adults with prenatal alcohol exposure and in the normal controls, is a larger P3 brain wave only in the more challenging No-go condition. We found that the young adults in the idiopathic ADHD group (i.e., those without prenatal alcohol exposure) showed a larger P3 wave during both types of trials — those where they had to inhibit the button press and those where they did not have to inhibit, which suggests that they found the whole task more difficult and were unable to develop the type of automatic strategy for inhibiting responses that would be expected at this age."

Jacobson added that this study is the first to use ERPs to compare neurophysiological function during a cognitive task with these two groups.

"The data support the notion that information processing difficulties in children with prenatal alcohol exposure who exhibit ADHD symptoms may differ from those seen in children with idiopathic ADHD, even though behaviorally both groups may exhibit inattention and hyperactivity," he said. "The ERP data suggest that different neurophysiological processes may be responsible for the attention problems seen in these two groups, which may explain why psychostimulant medication, which is often effective in treating idiopathic ADHD, is reported to be less effective in children with ADHD behavioral symptoms who were prenatally exposed to alcohol."

In summary, he said, this study provides improved understanding of the differences in neurophysiological processing responsible for the behavioral symptoms in these two different groups, which may in turn, provide important clues regarding new treatments that may be more effective for treating ADHD symptoms in children with prenatal alcohol exposure.

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Journal Reference:

1. Burden et al. An Event-Related Potential Study of Response Inhibition in ADHD With and Without Prenatal Alcohol Exposure. Alcoholism Clinical and Experimental Research, 2010; DOI: 10.1111/j.1530-0277.2009.01130.x

An Australian-German team of scientists at Freie Universität and the Queensland Brain Institute in Brisbane, Australia, has found a way to measure the attention span of a fly. The findings could lead to further advances in the understanding of attention-deficit hyperactivity disorder (ADHD) and autism in humans.

Associate Professor Bruno van Swinderen at the Queensland Brain Institute in Brisbane and Dr. Björn Brembs at Freie Universität combined genetic techniques with brain recordings and behavioral testing. They found different mutations that either increase or decrease a fly's attention span.

Using the genetic fruit fly model, Drosophila melanogaster, van Swinderen found that a fly's level of distractibility is finely tuned to allow "normal" behavioral responses to a constantly changing environment. He said, "We now have the two ends of an attention spectrum in our model. We have a fly memory mutant that is hard to distract and another fly memory mutant that's too distractible. They both have the same result — they don't learn well but for completely different reasons, not unlike human patients afflicted with autism and ADHD."

The fruit flies were fed methylphenidate, which is sold under the brand name Ritalin and is used to treat patients with ADHD. The researchers found the drug had similar effects on fruit flies as it did on people: it helped the distractible flies to pay attention to visual stimuli.

"It suggests there may be similar pathways in the brains of fruit flies and humans, which means we now have a simple reductionist model, with all the genetic tools that go along with it, to try to understand what exactly this drug is doing," according to van Swinderen.

Heisenberg fellow Brembs agrees: "These surprising parallels between insects and humans may point to a general, common functional organization of brains."

The research is reported in the Journal of Neuroscience.

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Journal Reference:

1. Bruno van Swinderen, Björn Brembs. Attention-Like Deficit and Hyperactivity in a Drosophila Memory Mutant. Journal of Neuroscience, 2010; 30 (3): 1003 DOI: 10.1523/JNEUROSCI.4516-09.2010

Children who are mixed-handed, or ambidextrous, are more likely to have mental health, language and scholastic problems in childhood than right- or left-handed children, according to a new study published in the journal Pediatrics.

The researchers behind the study, from Imperial College London and other European institutions, suggest that their findings may help teachers and health professionals to identify children who are particularly at risk of developing certain problems.

Around one in every 100 people is mixed-handed. The study looked at nearly 8,000 children, 87 of whom were mixed-handed, and found that mixed-handed 7 and 8-year old children were twice as likely as their right-handed peers to have difficulties with language and to perform poorly in school.

When they reached 15 or 16, mixed-handed adolescents were also at twice the risk of having symptoms of attention deficit/hyperactivity disorder (ADHD). They were also likely to have more severe symptoms of ADHD than their right-handed counterparts. It is estimated that ADHD affects between 3 to 9 percent of school-aged children and young people.

The adolescents also reported having greater difficulties with language than those who were left- or right-handed. This is in line with earlier studies that have linked mixed-handedness with dyslexia.

Little is known about what makes people mixed-handed but it is known that handedness is linked to the hemispheres in the brain. Previous research has shown that where a person's natural preference is for using their right hand, the left hemisphere of their brain is more dominant.

Some researchers have suggested that mixed-handedness indicates that the pattern of dominance is not that which is typically seen in most people, i.e. it is less clear that one hemisphere is dominant over the other. One study has suggested that ADHD is linked to having a weaker function in the right hemisphere of the brain, which could help explain why some of the mixed-handed students in the study had symptoms of ADHD.

Dr Alina Rodriguez, the lead researcher on the study from the School of Public Health at Imperial College London, said: "Mixed-handedness is intriguing — we don't know why some people prefer to make use of both hands when most people use only one. Our study is interesting because it suggests that some children who are mixed handed experience greater difficulties in school than their left- and right-handed friends. We think that there are differences in the brain that might explain these difficulties, but there needs to be more research.

"Because mixed-handedness is such a rare condition, the number of mixed-handed children we were able to study was relatively small, but our results are statistically and clinically significant. That said, our results should not be taken to mean that all children who are mixed-handed will have problems at school or develop ADHD. We found that mixed-handed children and adolescents were at a higher risk of having certain problems, but we'd like to stress that most of the mixed-handed children we followed didn't have any of these difficulties," added Dr Rodriguez.

To study the effects of mixed-handedness, Dr Rodriguez and her colleagues looked at prospective data from a cohort of 7,871 children from Northern Finland. Using questionnaires, the researchers assessed the children when they reached 7 to 8 years of age and again at 15 to 16 years of age.

When the children were aged 8, the researchers asked parents and teachers to assess their linguistic abilities, scholastic performance and behaviour. The teachers reported whether children had difficulties in reading, writing or mathematics and rated the children's academic performance as below average, average or above average.

The adolescents' parents and the adolescents themselves completed follow-up questionnaires when they were 15-16 years of age, with the children evaluating their school performance in relation to their peers and the parents assessing their children's behaviour, on a questionnaire that is widely used to identify ADHD symptoms.

The research was funded by the Academy of Finland; Sigrid Juselius Foundation, Finland; Thule Institute, University of Oulu, Finland; and the National Institute of Mental Health. Dr Rodriguez received support from VINNMER.

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Journal Reference:

1. Alina Rodriguez, Marika Kaakinen, Irma Moilanen, Anja Taanila, James J. McGough, Sandra Loo, and Marjo-Riitta Järvelin. Mixed-Handedness Is Linked to Mental Health Problems in Children and Adolescents. Pediatrics, 2010

Two brain areas fail to connect when children with attention deficit hyperactivity disorder attempt a task that measures attention, according to researchers at the UC Davis Center for Mind and Brain and M.I.N.D. Institute.

"This is the first time that we have direct evidence that this connectivity is missing in ADHD," said Ali Mazaheri, postdoctoral researcher at the Center for Mind and Brain. Mazaheri and his colleagues made the discovery by analyzing the brain activity in children with ADHD. The paper appears in the current online issue of the journal Biological Psychiatry.

The researchers measured electrical rhythms from the brains of volunteers, especially the alpha rhythm. When part of the brain is emitting alpha rhythms, it shows that it is disengaged from the rest of the brain and not receiving or processing information optimally, Mazaheri said.

In the experiments, children with diagnosed ADHD and normal children were given a simple attention test while their brain waves were measured. The test consisted of being shown a red or blue image, or hearing a high or low sound, and having to react by pressing a button. Immediately before the test, the children were shown either a letter "V" to alert them that the test would involve a picture (visual), or an inverted "V" representing the letter "A" to alert them that they would hear a sound (auditory).

The experiments were conducted by researchers in the laboratories of Ron Mangun, professor of psychology and neurology, and Blythe Corbett, associate clinical professor of psychiatry and behavioral sciences and a researcher at the M.I.N.D. Institute.

According to current models of how the brain allocates attention, signals from the frontal cortex — such as the "V" and "A" cues — should alert other parts of the brain, such as the visual processing area at the back of the head, to prepare to pay attention to something. That should be reflected in a drop in alpha wave activity in the visual area, Mazaheri said.

And that is what the researchers found in the brain waves of children without ADHD. But children with the disorder showed no such drop in activity, indicating a disconnection between the center of the brain that allocates attention and the visual processing regions, Mazaheri said.

"The brains of the children with ADHD apparently prepare to attend to upcoming stimuli differently than do typically developing children," he said.

Children with ADHD did improve their reaction times when properly cued, but they don't seem to allocate resources as efficiently, Mazaheri said.

This is the first evidence from brain electrical patterns for a functional disconnection in cortical attention systems in ADHD, he said. Current definitions of ADHD are based only on behavior.

The research was originally inspired by a desire to combine laboratory and clinical research to go beyond existing measures of ADHD and get a better understanding of the condition, Corbett said.

"Clearly the crosstalk from bedside to bench has been fruitful," she said.

Other co-authors on the paper are staff research associate Sharon Corina, postdoctoral fellow Evelijn Bekker and research assistant Anne Berry.

The study was funded by the grants from the National Institutes of Health, the Netherlands Organization for Scientific Research, the Perry Family Foundation, the Debber Family Foundation and the Aristos Academy.