Posts tagged network analysis
Articles and news from the latest research reports.
‘Rain Man’-like Brains Mapped with Network Analysis
Innovative Technique Sheds Light on Abnormal Brain Connectivity Responsible for Common Genetic Cause of Autism
A group of researchers at UC San Francisco and UC Berkeley have mapped the three-dimensional global connections within the brains of seven adults who have genetic malformations that leave them without the corpus callosum, which connects the left and right sides of the brain.
These “structural connectome” maps, which combine hospital MRIs with the mathematical tool known as network analysis, are described in the upcoming April 15 issue of the journal Neuroimage. They reveal new details about the condition known as agenesis of the corpus callosum, which is one of the top genetic causes of autism. The condition was part of the mysterious brain physiology of Laurence Kim Peek, the remarkable savant portrayed by Dustin Hoffman in the 1987 movie “Rain Man.”
While some people born with agenesis of the corpus callosum are of normal intelligence and do not have any obvious signs of neurologic disease, approximately 40 percent of people with the condition are at high risk for autism. Given this, the work is a step toward finding better ways to image the brains of people with the condition, said Pratik Mukherjee, MD, PhD, a professor of radiology and biomedical imaging at UCSF who was the co-senior author of the research.
Understanding how brain connectivity varies from person to person may help researchers identify imaging biomarkers for autism to help diagnose it and manage care for individuals. Currently autism is diagnosed and assessed based on cognitive tests, such as those involving stacking blocks and looking at pictures on flip cards.
While the new work falls short of a quantitative measure doctors could use instead of cognitive testing, it does offer a proof-of-principle that this novel technique may shed light on neurodevelopment disorders.
“Because you are looking at the whole brain at the network level, you can do new types of analysis to find what’s abnormal,” Mukherjee said.
The Connection between the Brain Hemispheres and Autism
Agenesis of the corpus callosum can arise if individuals are born missing DNA from chromosome 16 and often leads to autism.
Scientists have long puzzled over what the link is between this disorder and the autistic brain, said co-senior author of the paper Elliott Sherr, MD, PhD, professor of neurology and genetics especially since not all people with this malformation develop autism.
Doctors believe this is because the brain has a rich capacity for rewiring in alternative ways.
Pursuing this question, Mukherjee and Sherr turned to MRI and the mathematical technique of network analysis, which has long supported fields like civil engineering, helping urban planners optimize the timing of traffic lights to speed traffic. This is the first time network analysis has been applied to brain mapping for a genetic cause of autism.
The brain offers a significantly complicated challenge for analysis because, unlike the streets of a given city, the brain has hundreds of billions of neurons, many of which make tens of thousands of connections to each other, making its level of connectivity highly complex.
By comparing the seven rain man-like brains to those of 11 people without this malformation, the scientists determined how particular structures called the cingulate bundles were smaller and the neurons within these bundles were less connected to others in the brain. They also found that the network topology of the brain was more variable in people with agenesis of the corpus callosum than in people without the malformation.
'Network' analysis of the brain may explain features of autism
A look at how the brain processes information finds a distinct pattern in children with autism spectrum disorders. Using EEGs to track the brain’s electrical cross-talk, researchers from Boston Children’s Hospital have found a structural difference in brain connections. Compared with neurotypical children, those with autism have multiple redundant connections between neighboring brain areas at the expense of long-distance links.
The study, using a “network analysis” like that used to study airlines or electrical grids, may help in understanding some classic behaviors in autism. It was published February 27 in BioMed Central’s open access journal BMC Medicine, accompanied by a commentary.
"We examined brain networks as a whole in terms of their capacity to transfer and process information," says Jurriaan Peters, MD, of the Department of Neurology at Boston Children’s Hospital, who is co-first author of the paper with Maxime Taquet, a PhD student in Boston Children’s Computational Radiology Laboratory. "What we found may well change the way we look at the brains of autistic children."
Peters, Taquet and senior authors Simon Warfield, PhD, of the Computational Radiology Laboratory and Mustafa Sahin, MD, PhD, of Neurology, analyzed EEG recordings from two groups of autistic children: 16 children with classic autism, and 14 children whose autism is part of a genetic syndrome known as tuberous sclerosis complex (TSC). They compared these readings with EEGs from two control groups—46 healthy neurotypical children and 29 children with TSC but not autism.
In both groups with autism, there were more short-range connections within different brain region, but fewer connections linking far-flung areas.
A brain network that favors short-range over long-range connections seems to be consistent with autism’s classic cognitive profile—a child who excels at specific, focused tasks like memorizing streets, but who cannot integrate information across different brain areas into higher-order concepts.
"For example, a child with autism may not understand why a face looks really angry, because his visual brain centers and emotional brain centers have less cross-talk," Peters says. "The brain cannot integrate these areas. It’s doing a lot with the information locally, but it’s not sending it out to the rest of the brain."