June 10, 2014
Brain Imaging Used To Identify Why ADHD Persists Into Adulthood
Brett Smith for redOrbit.com - Your Universe Online
While about 11 percent of American school children are diagnosed with attention deficit hyperactivity disorder (ADHD), many outgrow the condition as they progress into adulthood.
In an attempt to understand why some ADHD may persist into adulthood, MIT researchers used brain-imaging technology to identify key differences in a specific brain communication network that is active when the brain is awake and not focused on a specific task, according to a paper published in the journal Brain.
“The psychiatric guidelines for whether a person’s ADHD is persistent or remitted are based on lots of clinical studies and impressions. This new study suggests that there is a real biological boundary between those two sets of patients,” said John Gabrieli, a professor of health sciences and technology and a professor of brain and cognitive sciences at MIT.
In the study, researchers recruited 35 adults who were diagnosed with ADHD as children, including 13 who still have the disorder. The study team then used functional magnetic resonance imaging (fMRI) to see what the brain is doing when a person is not focused on any particular activity. They were looking to find patterns that revealed which parts of the brain communicate with each other during “wakeful rest.”
“It’s a different way of using functional brain imaging to investigate brain networks,” said Susan Whitfield-Gabrieli, a research scientist at MIT. “Here we have subjects just lying in the scanner. This method reveals the intrinsic functional architecture of the human brain without invoking any specific task.”
When the brain is unfocused in people without ADHD, a unique synchrony of activity emerges in brain areas known as the default mode network. Previous research has demonstrated that in children and adults with ADHD, activity in two main hubs of this network, the posterior cingulate cortex and the medial prefrontal cortex, do not match up.
In the new study, the MIT team revealed that in adults who had been identified as having ADHD as children but no longer have it, this normal synchrony pattern is recovered.
“Their brains now look like those of people who never had ADHD,” said study author Aaron Mattfeld, a postdoctoral brain researcher at MIT.
“This finding is quite intriguing,” commented Francisco Xavier Castellanos, a professor of child and adolescent psychiatry at New York University who was not involved in the research. “If it can be confirmed, this pattern could become a target for potential modification to help patients learn to compensate for the disorder without changing their genetic makeup.”
Brain images taken during the study did reveal similarities between adults with ADHD and those who had outgrown the condition.
In people without ADHD, when the default mode network is active, activity in another network, called the task positive network, is lowered. When the brain is required to focus, activity in these regions switches.
Brain images taken in the study revealed that all 35 volunteers who had been diagnosed with ADHD as children showed patterns of simultaneous activation of both networks. Simultaneous activity is thought to be a sign of executive function impairment and all the volunteers performed poorly when their management of cognitive tasks was tested.
“Once you have executive function problems, they seem to hang in there,” Gabrieli said.
The study team said they plan to investigate how commonly prescribed ADHD medications affect activity in these brain networks.
“It’s unknown what’s different about the other 40 percent or so who don’t respond very much,” Gabrieli said. “We’re pretty excited about the possibility that some brain measurement would tell us which child or adult is most likely to benefit from a treatment.”