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 INSERM1 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.
Currently, the fundamental work on ADD uses mainly animal models obtained by mutations that disturb dopamine production and transmission pathways. In mice 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 noradrenaline on the superior colliculus more precisely could open the way to innovative therapeutic strategies.
In this image, marking shows the axons in retinal neurons (in red) that innervate the superior colliculus (in blue) in a “normal” mouse
© Michael Reber / Inserm Institut des neurosciences cellulaires et intégratives
(Français) Attribué par la fondation Danoise Lundbeck, le « Brain Prize » est un grand prix international qui récompense des scientifiques pour l’importance de leurs recherches en neurosciences. Il est doté d’un montant d’un million d’euros. Il met cette année à l’honneur des ...
Living beings are able to integrate and identify relevant sensory information, such as smells, sounds or light, in order to regulate how they behave in the presence of potential danger. This is called context discrimination. Inserm researchers based at Neurocentre Magendie in ...
Defective response inhibition and collicular noradrenaline enrichment in mice with duplicated retinotopic map in the superior colliculus. Mathis C, Savier E, Bott JB, Clesse D, Bevins N, Sage-Ciocca D, Geiger K, Gilet A, Laux-Biehlman A, Goumon Y, Lacaud A, Lelievre V, Kelche C, Cassel JC, Pfrieger FW and Reber M. Brain Struct. Func. Brain Structure and Function -online 20 march 2014 DOI: 10.1007/s00429-014-0745-5