New imaging research at UCLAdetailed Dec. 4 as an advance online publication of the journal NatureNeuroscience shows children with autism have virtually no activity in a keypart of the brain's mirror neuron system while imitating and observing emotions.
Mirror neurons fire when a person performs a goal-directedaction and while he or she observes the same action performed by others.Neuroscientists believe this observation-execution matching system provides aneural mechanism by which others' actions, intentions and emotions can beunderstood automatically.
Symptoms of autism include difficulties with socialinteraction — including verbal and nonverbal communication — imitation andempathy. The new findings dramatically bolster a growing body of evidencepointing to a breakdown of the brain's mirror neuron system as the mechanismbehind these autism symptoms.
"Our findings suggest that adysfunctional mirror neuron system may underlie the social deficits observed inautism," said Mirella Dapretto, lead author and assistant professor‑in‑residenceof psychiatry and biobehavioral sciences at the Semel Institute forNeuroscience and Human Behavior at UCLA and the David Geffen School of Medicineat UCLA. "Together with other recent data, our results provide strong supportfor a mirror neuron theory of autism. This is exciting because we finally havean account that can explain all core symptoms of this disorder."
Conducted at the Semel Institute's
Separately, symptom severity of each child with autism wastested using two independent measures (the Autism Diagnostic ObservationSchedule — Generic, and the Autism Diagnostic Interview).
The study shows that unlike typically developing children,children with autism have virtually no activity in the pars opercularis of the inferior frontal gyrus, identified by previous research as a key part of the mirrorneuron system. Importantly, the level of mirror neuron activity seen inchildren with autism was inversely related to symptom severity in the socialdomain.
Children with autism also showed reduced activity in theemotion centers of the brain, consistent with the hypothesis that thismirroring mechanism may play a crucial role for understanding how others feeland for empathizing with them.
All of the children rehearsed the tasks prior to the fMRIscans to assure researchers they could perform the tasks. Both groups performedequally well. Normal brain activity in areas of the brain involving sight andfacial movements indicated that the children with autism remained on taskduring the fMRI scans.
The research was fundedprimarily by a grant from the National Institute of Child Health and HumanDevelopment as part of the Collaborative Programs for Excellence in Autism.
In addition to Dapretto, the UCLA research team includedMarco Iacoboni, Susan Bookheimer, Marian Sigman, Mari Davies, Jennifer Pfeiferand Ashley A. Scott. The team represents the
Semel Institute for Neuroscience and HumanBehavior: http://www.npi.ucla.edu/.
UCLA Department of Psychology: http://www.psych.ucla.edu/.