Autism spectrum disorder (ASD) is a very complex and heterogeneous disease, commonly characterized with deficits in social communication, interaction, and repetitive patterns of behavior, interest and activities. Current pharmacological treatments can help with some of the medical and psychiatric comorbidities as well as symptom management, but none address the core deficit. Early diagnosis and intervention for ASD have been helpful in providing care so therefore, it is essential that we are able to identify children with ASD sooner.
Genetic risk accounts for around half of the causes of ASD, and within the last 30 years, over 100 genes have been identified to place children at risk for ASD. There are multiple co-occurring conditions in individuals with autism that can be used to create subgroups of this disorder. For example, 20-30% of individuals with autism have co-occurring epilepsy, gastrointestinal problems, or sleep disorders. These various subtypes make treatment for the core symptoms of ASD difficult and hard to identify. Dr. David G. Amaral heads the UC Davis MIND Institute Autism Phenome Project, which is a longitudinal, multidisciplinary analysis of over 400 families with children with autism. They collect an extensive amount of data to create clinically meaningful subtypes of ASD, making it eventually possible to have more customized treatment for each subtype. One recent subtype that Dr. Amaral’s lab has found is a neurophenotype that is characterized by megalencephaly, a brain size that is large and disproportionate to body size. Around 15% of boys with autism have this neurophenotype and children with autism and larger brains typically have been found to have more severe disabilities and poorer prognosis. More recently, Dr. Amaral’s lab has also found that ASD is associated with varied presentations of clinical anxiety as well. The standardized parent report anxiety scales done for children with ASD have reduced sensitivity to be able to detect clinical anxiety in ASD, especially for children with intellectual impairment.
On the other end of the spectrum, Dr. Amaral’s lab also has done extensive preclinical work looking into amygdala growth in the macque monkey. Evidence in the field has suggested that human amygdala growth coincides with complex socioemotional learning. This study was done to map the growth of a nonhuman primate amygdala from birth to adulthood using magnetic resonance images. As seen in the Figure 4 attachment from his paper, they discovered that the amygdala volume increases by 50% from age 6 months to 5 years, which is a longer period of growth than most other cortical gray and white matter. They suggest that because the amygdala grows for an extended period of time, there is more time for different deleterious environmental influences to affect this growth, potentially leading to multiple diseases where the amygdala is strongly implicated, including anxiety, depression, schizophrenia and autism.
To hear more about the work being done in Dr. David G. Amaral ’s lab, please join us at 4:00pm, Tuesday 02/25/2020 in the Marilyn G. Farquhar Seminar Room at the Center for Neural Circuits and Behavior.
Written by Caroline Jia, a 1st year Neuroscience MSTP Student, working in Sung Han’s laboratory at the Salk Institute