Posts tagged attention deficit
Articles and news from the latest research reports.
Researchers Uncover Cellular Mechanisms for Attention in the Brain
The ability to pay attention to relevant information while ignoring distractions is a core brain function. Without the ability to focus and filter out “noise,” we could not effectively interact with our environment. Despite much study of attention in the brain, the cellular mechanisms responsible for the effects of attention have remained a mystery… until now.
In a study appearing in the journal Nature, researchers from Dartmouth’s Geisel School of Medicine and the University of California Davis studied communications between synaptically connected neurons under conditions where subjects shifted their attention toward or away from visual stimuli that activated the recorded neurons. Using this highly sensitive measure of attention’s influence on neuron-to-neuron communication, they were able to demonstrate that attention operates at the level of the synapse to improve sensitivity to incoming signals, sharpen the precision of these signals, and selectively boost the transmission of attention-grabbing information while reducing the level of noisy or attention-disrupting information.
The results point to a novel mechanism by which attention shapes perception by selectively altering presynaptic weights to highlight sensory features among all the noisy sensory input.
"While our findings are consistent with other reported changes in neuronal firing rates with attention, they go far beyond such descriptions, revealing never-before tested mechanisms at the synaptic level," said study co-author Farran Briggs, PhD, assistant professor of Physiology and Neurobiology at the Geisel School of Medicine.
In addition to expanding our understanding of brain, this study could help people with attention deficits resulting from brain injury or disease, possibly leading to improved screening and new treatments.
Many causes for learning lags in tumor disorder
The causes of learning problems associated with an inherited brain tumor disorder are much more complex than scientists had anticipated, researchers at Washington University School of Medicine in St. Louis report.
The disorder, neurofibromatosis 1 (NF1), is among the most common inherited pediatric brain cancer syndromes. Children born with NF1 can develop low-grade brain tumors, but their most common problems are learning and attention difficulties.
“While one of our top priorities is halting tumor growth, it’s also important to ensure that these children don’t have the added challenges of living with learning and behavioral problems,” says senior author David H. Gutmann, MD, PhD, the Donald O. Schnuck Family Professor of Neurology. “Our results suggest that learning problems in these patients can be caused by more than one factor. Successful treatment depends on identifying the biological reasons underlying the problems seen in individual patients with NF1.”
The study appears online in Annals of Neurology.
According to Gutmann, who is director of the Washington University Neurofibromatosis Center, scientists are divided when considering the basis for NF1-associated learning abnormalities and attention deficits.
Mutations in the Nf1 gene can disrupt normal regulation of an important protein called RAS in the hippocampus, a brain region critical for learning. Initial work from other investigators had shown that increased RAS activity due to defective Nf1 gene function impairs memory and attention in some Nf1 mouse models.
However, earlier studies by Gutmann and collaborator David F. Wozniak, PhD, research professor in psychiatry, showed that a mutation in the Nf1 gene lowers levels of dopamine, a neurotransmitter involved in attention. In this Nf1 mouse model, Gutmann and his colleagues found that the branches of dopamine-producing nerve cells were unusually short, limiting their ability to make and distribute dopamine and leading to reduced attention in those mice.
The new research suggests that both sides may be right.
In the latest study, postdoctoral fellow Kelly Diggs-Andrews, PhD, found that the branches of dopamine-producing nerve cells that normally extend into the hippocampus are shorter in Nf1 mice. As a result, dopamine levels are lower in that part of the brain.
Charles F. Zorumski, MD, the Samuel B. Guze Professor and head of the Department of Psychiatry, showed that the low dopamine levels disrupts the ability of nerve cells in the hippocampus to modulate the way they communicate with each other. These communication adjustments are a primary way the brain creates memories.
Researchers then found that giving Nf1 mice L-DOPA, which increases dopamine levels, restored their nerve cell branch lengths to normal and corrected the hippocampal communication defect. L-DOPA also eliminated the memory and learning deficits in these mice.
“These results and the earlier findings suggest that there are a variety of ways that NF1 may cause cognitive dysfunction in people,” Gutmann says. “Some may have problems caused only by increased RAS function, others may be having problems attributable to reduced dopamine, and a third group may be having difficulties caused by both RAS and dopamine abnormalities.”
To customize patient therapy, Gutmann and his colleagues are now working to develop ways to quantify the contributions of dopamine and RAS to NF1-related learning disorders.
(Source: news.wustl.edu)