Autism/Social cues and early brain response

Autism study, 2013

                For Immediate Release        Friday, March 22, 2013        
          Contact: Robert Bock          301-496-5133       

Delay in shifting gaze linked to early brain development in autism

NIH-funded study documents possible risk factor for autism at 7 months of age

At  7 months of age, children who are later diagnosed with autism take a split  second longer to shift their gaze during a task measuring eye movements and  visual attention than do typically developing infants of the same age,  according to researchers supported by the National Institutes of Health.

The  difference between the groups’ test results was 25 to 50 milliseconds on  average, the researchers found, too brief to be detected in social interactions  with an infant. However, they showed that this measurable delay could be  accounted for by differences in the structure and organization of actively  developing neurological circuits of a child’s brain.

When they were infants, children who were later diagnosed with autism   took longer to shift their gaze during a measure of eye movements than   did infants who were not diagnosed with autism. The researchers believe   that brain circuits involved with a brain structure known as the   splenium of the corpus callosum (shown in this scan) may account for the   differences in gaze shifting between the two groups.   Image courtesy of Jason Wolff, Ph.D., University of North Carolina at Chapel Hill.

Efficiently  shifting attention early in infancy is thought to be important for later social  and cognitive development. Split-second delays, the researchers  suggested, could be a precursor to such well known symptoms of autism as  difficulty making eye contact or following a parent’s pointing finger, problems  that generally emerge after a child turns 1. Typically, autism spectrum  disorder (ASD) is not diagnosed until  after 3 or 4 years of  age.

“This  study ties a difference in reaction times to differences in the developing  brain, which may shape the way babies take in and respond to their environment  in more noticeable ways over time,” said Alice Kau, Ph.D., of the Intellectual  and Developmental Disabilities Branch of the Eunice Kennedy Shriver National  Institute of Child Health and Human Development (NICHD), the institute that  funded the research. “The brain’s pathways for communication are forming  rapidly in early infancy, and small differences at this stage could foretell  greater difference at a later age.”

First  author Jed T. Elison, Ph.D., of the University of North Carolina at Chapel Hill  (UNC) and California Institute of Technology, Pasadena, collaborated with  senior author Joseph Piven, M.D., of UNC, and researchers from The Children’s  Hospital of Philadelphia and the University of Pennsylvania, Philadelphia; the  University of Texas at Dallas; Washington University, St. Louis; the University  of Washington, Seattle; the University of Utah, Salt Lake City; McGill  University, Montreal; and the University of Alberta, Canada.

The  study appears in the American Journal of Psychiatry.

The  research is part of the ongoing Infant Brain  Imaging Study External Web Site Policy, which is  supported through the NICHD’s Autism Centers  of Excellence Program.

To  measure shifts in gaze and visual attention, the researchers used sophisticated  eye tracking equipment to capture the precise timing of eye movements. The infants sat on their parent’s laps and watched images appear on a computer  monitor. The test procedure used in the study is known as the gap/overlap  task. In one part of the test, an image would appear in the center of the  screen to attract the infant’s gaze, and would then disappear. After a brief  delay, or gap, another image would appear at the edge of the screen.

In  another part of the test, the central image remained on the screen, and an  image appeared at the periphery of the screen. The researchers measured  the time it took infants to initiate an eye movement to the image in the  periphery. In addition to the eye tracking task, the 7-month-old infants  took part in a type of magnetic resonance brain imaging called diffusion  weighted imaging, which measures the organization of neural circuits in the brain.

Fifty-seven  infants had an older sibling diagnosed with autism, and so were considered at  higher risk for developing autism themselves.  The study also included 40  infants who did not have an older sibling with autism and so were considered at  low risk for developing autism. All of the children returned to the study  facility after their second birthdays for clinical assessments.  By  this time, 16 of the high-risk children were classified as having ASD. Based on the classification during the clinical assessment visit, the  researchers compared the brain imaging data and the eye tracking data collected  at 7 months across three groups:

  • Children  with an older sibling with ASD who themselves were classified with ASD  (high-risk positive)
  • Children  with an older sibling with ASD who were not classified with ASD (high-risk  negative)
  • Children  who did not have an older sibling with ASD (low risk)

During  the overlap condition of the eye tracking task, in which presentation of the  central image overlapped with the appearance of the image at the edge of the  screen, the researchers found a notable difference in the time it took for the  high-risk positive infants to shift their gaze, compared to the other groups of  infants.

The  researchers uncovered evidence that the functioning of a key brain structure  may account for the differences in gaze shifting between the groups.  The  brain structure is called the splenium of the corpus callosum.  This  structure is considered to be an important neural connection between the two  hemispheres of the brain.

In  the low-risk infants, the researchers found that the speed with which the  infants shifted their gaze was closely associated with the size of the  splenium.  The greater the size of the splenium, the more rapidly the  infants were able to switch their gaze.

However,  in the infants who later were found to have autism, the researchers did not  find any correlation between splenium size and the speed at which an infant  shifted gaze.  The researchers theorize that the differences in gaze  shifting between the two groups may not be due directly to differences in the  splenium between the groups, but to differences in a brain circuit that  connects the splenium to visual areas of the brain.

Ultimately,  differences in gaze detected at 7 months of age might help doctors identify  children likely to develop autism later on, the authors suggested.

“By  refining the gaze test and coupling it with other assessments, we hope to  improve the ability to identify ASD in the first year of life,” Dr. Elison  said.

An  image depicting the splenium of the corpus callosum is available at http://www.nichd.nih.gov/news/releases/Pages/032113-splenium-image.aspx.

About  the Eunice Kennedy Shriver National Institute of Child Health and Human  Development (NICHD):  The NICHD sponsors research on development, before and after birth; maternal,  child, and family health; reproductive biology and population issues; and  medical rehabilitation. For more information, visit the Institute’s website at http://www.nichd.nih.gov/.

About the National Institutes of Health (NIH): NIH, the nation’s medical research agency, includes 27 Institutes and Centers  and is a component of the U.S. Department of Health and Human Services. NIH  is the primary federal agency conducting and supporting basic, clinical, and  translational medical research, and is investigating the causes, treatments,  and cures for both common and rare diseases. For more information about NIH  and its programs, visit http://www.nih.gov.

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