Interactions between cortical and subcortical regions important in hypersensitivity in ASD
The increased interaction between cortical and subcortical brain
regions highlights the central role of hypersensitivity and other
sensory symptoms in defining Autism Spectrum Disorder (ASD). This is
presented in research performed by a team led by Christian Keysers and
Leonardo Cerliani at the Netherlands Institute for Neuroscience in
Amsterdam. This finding provides a key to understand the often
underestimated sensory hypersensitivity in autism and to seed a
scientific understanding of how to tackle this hypersensitivity. The
research was published in JAMA Psychiatry on June 10.
People with ASD are known for their unusual behavior in the social
environment. Moreover, they often report other traits, linked to the
sensory environment: for instance the ability to perceive small details
in a picture or to detect a very soft sound coming from a distance.
“This hypersensitivity, however, is not always a gift: being captured by
the myriad of sensory stimuli we continuously receive from the
environment can be distracting and even overwhelming, and prevents us to
focus on what we care most,” says Cerliani. The scientists present in
their research that increased interaction between the cortical ad
subcortical brain regions is at the root of this hypersensitivity.
Brain regions that are strongly coupled have brain activity that
goes up and down together, even while relaxing, while regions that are
not coupled will have their brain activity fluctuate independently from
each other. By comparing how this spontaneous brain activity
synchronizes across various brain regions the team identified an
abnormally high synchrony between the sensory cortices involved in
perception and subcortical regions relaying information from the sensory
organs to the cortex. They found that a higher synchrony was associated
with a higher severity of autistic traits.
“During the development from childhood to adolescence, the
spontaneous activity of cortical regions involved in basic sensory
perception decouples from the activity of subcortical structures
relaying sensory information from the sensory organs to the cortex,”
explains Keysers. “This decoupling is thought to reflect the increasing
ability to block out irrelevant sensory information from perception,
allowing people to focus on their stream of thoughts and actions. In ASD
this process appears to be altered: their sensory cortex appears to be
abnormally coupled to subcortical structures.”
The team made these observations using resting-state functional
magnetic resonance imaging (fMRI) data from the largest neuroimaging
database on ASD aggregated so far: the ABIDE, founded and coordinated by
Dr. Adriana Di Martino, Dr. Stuart Mostofsky and Dr. Michael Milham.
The team of Keysers and Cerliani also contributed to the aggregation of
this database with the neuroimaging data acquired by Dr. Marc Thioux.
Autism Spectrum Disorder
ASD is an umbrella name for a number of developmental disorders,
including classic autism and Asperger syndrome. The number of people
with ASD is almost eightfold in the last twenty years and is seen in
more than 1% of the children.