ADHD

Updated 14 June 2017

Brain's reward system may be involved with ADHD

Researchers have discovered anomalies in the brain's reward system related to the neural circuits of motivation and gratification in children with ADHD.

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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 for the first time have 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.

Neuroscience and clinical research collaborate


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. However, 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.

Hyperactivity and impulsiveness

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.

Read more:

Functional brain pathways disrupted in kids with ADHD

Preventing ADHD is possible

 

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ADHD Expert

Dr Renata Schoeman has been in full-time private practice as a general psychiatrist (child, adolescent and adult psychiatry) since 2008, currently based in Oude Westhof (Bellville). Renata also holds appointments as senior lecturer in Leadership (USB) and as a virtual faculty member of USB Executive Development’s Neuroleadership programme. She serves on the advisory boards of various pharmaceutical companies, as a director of the Psychiatric Management Group (PsychMG) and is the co-convenor of the South African Society of Psychiatrist (SASOP) special interest group for adult ADHD, and co-founder of the Goldilocks and The Bear Foundation (www.gb4adhd.co.za) She is passionate about corporate mental health awareness and uses her neuroscience background to assist leaders in equipping them to become balanced, healthy and dynamic leaders that take their own and their team’s emotional, intellectual, social health and physical needs into account. Renata is academically active and enjoys research and collaborative work, has published in many peer-reviewed journals, and has presented at local and international congresses. She is regularly invited to present at conferences and to engage with the media. During her post-graduate studies, she trained at Harvard, Boston in neurocognition and neuroimaging. Her awards include, amongst others, the Young Minds in Psychiatry award from the American Psychiatric Association, the Discovery Foundation Fellowship award, a Thuthuka award from the NRF, and a MRC Fellowship. She also received the Top MBA student award and the Director’s award from USB for 2015. She was a finalist for the Businesswomen’s Association of South Africa’s Businesswoman of the Year Award for 2016, and received the Excellence in Media Work award from SASOP during 2016.

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