Impaired coordination of brain activity in autism involves local, as well as long-range, signaling
A study based at the Martinos Center for Biomedical Imaging at Massachusetts General Hospital (MGH) finds that the local functional connectivity of the brain – the extent to which the activity of within a small brain region appears to be coordinated – is reduced in individuals with autism spectrum disorders (ASD). Although it has been recognized for several years that functional connectivity between separate areas of the brain was reduced in ASD, it had been assumed that local functional connectivity was actually higher in the brains of autistic individuals.
"Functional connectivity reflects connections that actually play a role in the processing of information in the cortex," says Tal Kenet, PhD, of the Martinos Center, corresponding author of the study appearing in PNAS Online Early Edition. "Imagine the brain is like an orchestra. When the violins are coordinated with the woodwinds and the trumpets with the violas, the orchestra will play in harmony – that's a version of long-range connectivity. Local functional connectivity is like focusing on the violins and whether they are all playing together.
"What has commonly been believed about autism is that the 'orchestra' isn't very well coordinated between sections but that the 'instruments' within sections were highly coordinated with each other, as though they were playing their own tune independent of the rest of the orchestra. We found that the opposite is true and that even the timing within sections is off. It's like each violin is playing independently from not only the rest of the orchestra but from all the other violins."
Because the distances involved in communication between nearby neurons or groups of neurons are on a scale of millimeters to centimeters, it has been very difficult to study local connectivity through noninvasive imaging methods. The current study took advantage of a brain activity shown by previous invasive studies to reflect local communication – measurement of what are called nested oscillations, which occur when one aspect of a particular brain rhythm affects a different aspect of another brain rhythm. In this instance they focused on phase-amplitude coupling, in which the phase of a lower-frequency rhythm changes the amplitude of a higher-frequency rhythm, measured by magnetoencephalography (MEG), an imaging technique that detects the location as well as the timing of brain activity with high precision.
The research team used MEG to measure both local phase-amplitude coupling and longer range coordination of brain rhythms in 17 young men diagnosed with an ASD and in 20 volunteers with typical neurodevelopmental histories. Functional connectivity was measured while participants viewed faces with neutral expressions, faces with emotional expression – angry or fearful – and as a control, images of houses.
Local functional connectivity was measured in an area of the brain known to be important for the recognition of faces, while long-range connectivity was determined by looking for the coordination of brain rhythms between the facial recognition area and other, more distant areas of the cortex. Results were scored based on two statistical measures: for local connectivity, whether phase-amplitude coupling in the facial recognition area was stronger when participants viewed faces than when they viewed houses, and for long-range connectivity, whether there was a difference in how rhythms in the monitored areas corresponded with those in the facial recognition area while viewing the two types of images.
As expected, typically developing participants had greater long-range functional connectivity – reflected by increased correspondence of brain rhythms between monitored areas – than did participants with autism. Contrary to previous assumptions, however, participants with ASD also had reduced local functional connectivity, in that phase-amplitude coupling was not increased in their facial recognition area while viewing facial images. In addition, local functional connectivity was reduced to the same extent that long-range connectivity was reduced, and greater reductions were seen in participants whose autism-related symptoms were more severe. A combination of the local and long-range functional connectivity measures was 90 percent accurate in distinguishing participants with autism from those who were typically developing.
An instructor in Neurology at Harvard Medical School, Kenet notes that other studies are required to investigate local functional connectivity in contexts such as memory and language and that better understanding of the mechanisms underlying phase-amplitude coupling is needed. "That sort of work would have to be done invasively in animal models," she explains. "But if we can figure out a way of disrupting phase-amplitude coupling in animals that mimics what we see in autism, that could be an important clue towards what goes wrong in autism spectrum disorders. In addition, investigating whether disrupted phase-amplitude coupling occurs in children with autism could lead us to a biomarker for early diagnosis."
Journal reference: Proceedings of the National Academy of Sciences
Provided by Massachusetts General Hospital
- Autism risk gene linked to differences in brain structure Mar 21, 2012 | not rated yet | 0
- EEG test to identify autism in children Jun 26, 2012 | not rated yet | 0
- 'Faulty' brain connections may be responsible for social impairments in autism Jun 12, 2008 | not rated yet | 0
- Research may unlock mystery of autism's origin in the brain Aug 22, 2007 | not rated yet | 0
- Study: Common gene mutation affects kids with autism spectrum disorders Sep 14, 2012 | not rated yet | 0
- Motion perception revisited: High Phi effect challenges established motion perception assumptions Apr 23, 2013 | 3 / 5 (2) | 2
- Anything you can do I can do better: Neuromolecular foundations of the superiority illusion (Update) Apr 02, 2013 | 4.5 / 5 (11) | 5
- The visual system as economist: Neural resource allocation in visual adaptation Mar 30, 2013 | 5 / 5 (2) | 9
- Separate lives: Neuronal and organismal lifespans decoupled Mar 27, 2013 | 4.9 / 5 (8) | 0
- Sizing things up: The evolutionary neurobiology of scale invariance Feb 28, 2013 | 4.8 / 5 (10) | 14
question on coriolis effect with drag force
1 hour ago I really need help with this question. A small floating object initially moves with velocity v on the surface of a liquid at latitude λ. The...
Question of reflection and transmission of TEM wave in normal incidenc
7 hours ago Suppose TEM wave in +z normal to a boundary on xy plane at z=0. We know *E* & *H* are tangential to the boundary. Let ##\vec E_i=\hat x E##, be the...
the rudyak-krasnolutski effective potencial
8 hours ago Hi ... anyone now how to calculate or the formula of the rudyak-krasnolutski EFFECTIVE potencial ? the effective potencial includes the angular...
Normal force for a lever model
9 hours ago My model is a lever on a table top. One arm is horizontal on the table, while the other arm is raised at an angle alpha. I'm assuming the weight of...
gravity is std. therefore can we rate a 'mass at height' by watts?
14 hours ago For example.... wind turbines are primarily listed by their wattage (1.5MW etc.) Presumably their output is varied according to rotational speed, so...
Calculating on-axis elements of a solenoid
May 22, 2013 I wanted to mention that this solenoid has many winds over many layers. The thickness of the windings is 2.4 inches coming off of the engineering...
- More from Physics Forums - Classical Physics
More news stories
Children with autism showed significant improvement after six months of simple sensory exercises at home using everyday items such as scents, spoons and sponges, according to UC Irvine neurobiologists.
Autism spectrum disorders May 21, 2013 | 3 / 5 (1) | 0 |
Research by Victoria University PhD education graduand Larah van der Meer highlights the importance of understanding the communication preferences of children with developmental disabilities such as autism.
Autism spectrum disorders May 14, 2013 | 3.3 / 5 (3) | 1
At times, Andy Shih still finds himself overwhelmed by the groundswell of interest in autism applications he's seen in the three years since Apple Inc. released the first iPad.
Autism spectrum disorders May 09, 2013 | 2 / 5 (1) | 0
Children with autism see simple movement twice as quickly as other children their age, and this hypersensitivity to motion may provide clues to a fundamental cause of the developmental disorder, according ...
Autism spectrum disorders May 08, 2013 | not rated yet | 0 |
(AP)—Autism scientists are seeking more brain samples for research.
Autism spectrum disorders May 02, 2013 | 5 / 5 (1) | 0
(Medical Xpress)—Regulating the distribution of power in neurons is done by a system that makes the national electric grid look simple by comparison. Each neuron has several thousand mitochondria confined ...
6 hours ago | 4.8 / 5 (5) | 0 |
Teams of highly respected Alzheimer's researchers failed to replicate what appeared to be breakthrough results for the treatment of this brain disease when they were published last year in the journal Science.
9 hours ago | 5 / 5 (1) | 2 |
A brief visual task can predict IQ, according to a new study. This surprisingly simple exercise measures the brain's unconscious ability to filter out visual movement. The study shows that individuals whose ...
11 hours ago | 4.9 / 5 (8) | 0 |
Scientists at the National Institutes of Health report they have discovered in mouse studies that a small molecule released in the spinal cord triggers a process that is later experienced in the brain as ...
9 hours ago | 5 / 5 (2) | 0 |
Little is known about why asthma develops, how it constricts the airway or why response to treatments varies between patients. Now, a team of researchers at Weill Cornell Medical College, Columbia University Medical Center ...
10 hours ago | not rated yet | 0 |
Ethnic background plays a surprisingly large role in how diabetes develops on a cellular level, according to two new studies led by researchers at the Stanford University School of Medicine.
7 hours ago | not rated yet | 0 |