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.
For more information
Eunice Kennedy Shriver National Institute of Child
Health and Human Development (NICHD)
(MDN)
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