ADHD/ADD: Confirmation of the neurobiological origin

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 behaviour modifications similar to those of some patients who suffer from ADD.

Their work also shows noradrenaline (Norepinephrine) 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 (ADD/ADHD) 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 behaviour 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 (Norepinephrine), which vary from species to species, are still poorly understood.

However, we do know that this noradrenaline (Norepinephrine) imbalance is associated with significant behavioural 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 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.

Characterising the effects of noradrenaline (Norepinephrine) 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

Babies Cannot Read! NYU Study Confirms

Can babies learn to read? While parents use DVDs and other media in an attempt to teach their infants to read, these tools don't instill reading skills in babies, a study by researchers at New York University's Steinhardt School of Culture, Education, and Human Development has found.

"While we cannot say with full assurance that infants at this age cannot learn printed words, our results make clear they did not learn printed words from the baby media product that was tested," says Susan Neuman, a professor in NYU Steinhardt's Department of Teaching and Learning and the study's senior author.

However, Neuman adds, there was one undeniable effect of these products, on parents.

In exit interviews, there was the mistaken belief among parents that their babies were learning to read and that their children had benefited from the program in some areas of vocabulary development.

Susan Neuman

"It's clear that parents have great confidence in the impact of these products on their children," Neuman explains. "However, our study indicates this sentiment is misplaced."

In their study, which appears in the Journal of Educational Psychology, the researchers examined 117 infants, aged nine to 18 months, who were randomly assigned to treatment and control groups.

Children in the treatment condition received a baby media product, which included DVDs, word and picture flashcards, and flip books to be used daily over a seven-month period; children in the control condition did not receive these materials from the researchers.

Over the course of seven months, the researchers conducted a home visit, four laboratory visits, and monthly assessments of language development.

To test children's emerging skills in the laboratory, the researchers examined the capacity to recognize letter names, letter sounds, vocabulary, words identified on sight, and comprehension.

A combination of eye-tracking tasks and standardized measures were used to study outcomes at each stage of development.

Using a state-of-the art eye-tracking technology, which follows even the slightest eye movements, the researchers were able to closely monitor how the infants distributed their attention and how they shifted their gaze from one location to another when shown specific words and phrases.

The results, which included criterion and standardized measures of emergent and early reading skills, showed no differences between the infants exposed to baby media and the control group on 13 of the 14 assessments.

The only assessment that showed a difference was parents' beliefs that their child was learning new words despite countervailing evidence from a standardized measure indicating no differences between groups.

More Information: Can Babies Learn to Read? A Randomized Trial of Baby Media. Neuman, Susan B.; Kaefer, Tanya; Pinkham, Ashley; Strouse, Gabrielle Journal of Educational Psychology, Feb 24 , 2014, No Pagination Specified. doi: 10.1037/a0035937