"There was a lower concentration of dopamine markers in the brain of individuals with A.D.H.D., specifically in the areas of the brain that are involved with reward and motivation."

VOA: special.2009.09.29

She played a survivor of a Nazi concentration camp.

VOA: special.2009.05.29

Now,he thinks short is better. "I've gotten researchers telling me that you don't realize is how long someone can have a high level of concentration.

VOA: standard.2010.03.26

"There has been a real concentration in those three states of intertribal trouble.

VOA: standard.2010.03.23