Confirmation of the neurobiological origin of attention-deficit disorder

Confirmation of the neurobiological origin of attention-deficit disorder
In this image, marking shows the axons in retinal neurons (in red) that innervate the superior colliculus (in blue) in a "normal" mouse Credit: Michael Reber / Institut des Neurosciences Cellulaires et Intégratives

A study, carried out on mice, has just confirmed the neurobiological origin of attention-deficit disorder (ADD), a syndrome whose causes are poorly understood. Researchers from CNRS, the University of Strasbourg and INSERM have identified a cerebral structure, the superior colliculus, where hyperstimulation causes behavior modifications similar to those of some patients who suffer from ADD. Their work also shows noradrenaline accumulation in the affected area, shedding light on this chemical mediator having a role in attention disorders. These results are published in the journal Brain Structure and Function.

Attention-deficit disorder affects between 4-8% of children. It manifests mainly through disturbed attention and verbal and motor impulsiveness, sometimes accompanied by hyperactivity. About 60% of these children still show symptoms in adulthood. No cure exists at this time. The only effective treatment is to administer psychostimulants, but these have substantial side effects, such as dependence. Persistent controversy surrounding the neurobiological origin of this disorder has hindered the development of new treatments.

The study in Strasbourg investigated the behavior of transgenic mice having developmental defects in the superior colliculus. This structure, located in the midbrain, is a sensory hub involved in controlling attention and visual and spatial orientation. The mice studied were characterized by duplicated neuron projections between the superior colliculus and the retina. This anomaly causes visual hyperstimulation and excess noradrenaline in the superior colliculus. The effects of the neurotransmitter noradrenaline, which vary from species to species, are still poorly understood. However, we do know that this noradrenaline imbalance is associated with significant behavioral changes in mice carrying the genetic mutation. By studying them, researchers have observed a loss of inhibition: for example mice hesitate less to penetrate a hostile environment. They have difficulties in understanding relevant information and demonstrate a form of impulsiveness. These symptoms remind us of adult patients suffering from one of the forms of ADD.

Currently, the fundamental work on ADD uses mainly animal models obtained by mutations that disturb dopamine production and transmission pathways. In with a malformed superior colliculus, these pathways are intact. The changes occur elsewhere in the neural networks of the midbrain. By broadening the classic boundary used to research its causes, using these new models would allow a more global approach to ADD to be developed. Characterizing the effects of on the superior colliculus more precisely could open the way to innovative therapeutic strategies.

More information: Chantal Mathis, Elise Savier, Jean-Bastien Bott, Daniel Clesse, Nicholas Bevins, Dominique Sage-Ciocca, Karin Geiger, Anaïs Gillet, Alexis Laux-Biehlmann, Yannick Goumon, Adrien Lacaud, Vincent Lelièvre, Christian Kelche, Jean-Christophe Cassel, Frank W. Pfrieger, Michael Reber. "Defective response inhibition and collicular noradrenaline enrichment in mice with duplicated retinotopic map in the superior colliculus." Brain Structure and Function, 2014; DOI: 10.1007/s00429-014-0745-5

add to favorites email to friend print save as pdf

Related Stories

Seeing without looking

Dec 28, 2009

Like a spotlight that illuminates an otherwise dark scene, attention brings to mind specific details of our environment while shutting others out. A new study by researchers at the Salk Institute for Biological ...

Involuntary maybe, but certainly not random

Feb 12, 2009

Our eyes are in constant motion. Even when we attempt to stare straight at a stationary target, our eyes jump and jiggle imperceptibly. Although these unconscious flicks, also known as microsaccades, had long ...

Recommended for you

New research supporting stroke rehabilitation

16 hours ago

Using world-leading research methods, the team of Dr David Wright and Prof Paul Holmes, working with Dr Jacqueline Williams from the Victoria University in Melbourne, studied activity in an area of the brain ...

Team finds an off switch for pain

21 hours ago

In research published in the medical journal Brain, Saint Louis University researcher Daniela Salvemini, Ph.D. and colleagues within SLU, the National Institutes of Health (NIH) and other academic institutions have d ...

User comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.