Rett syndrome involves a number of developmental deficits similar to those observed in autism, including dysregulated motor movements, communication skills and cognitive processes. Rett syndrome is caused by mutations in a single gene, MeCP2, allowing researchers to study the disorder in mice that carry the mutations.
Autism is a deeply complex and poorly understood developmental brain disorder. Defined genetic disorders that cause autism may be instructive for unraveling the cellular and developmental changes that underlie the disorder.
Children with autism have been shown to display an increased latency of auditory processing, as measured by the electroencephalography (EEG) response to a sound as well as differences in brain activity at rest.
One of the core symptoms of autism is impaired interpretation of social cues and abnormal emotional responses to social cues. The amygdala is a brain region that plays a fundamental role in social functioning. Human imaging studies have demonstrated abnormal amygdala activity in people with autism, which is likely to contribute to the socio-emotional symptoms. However, the amygdala comprises several interconnected regions, and the neural basis for these behaviors is not clear.
Deficits in social behaviors are a core aspect of autism and can be quite debilitating. Despite significant advances in identifying genes associated with autism spectrum disorders, the neural circuits that mediate social behaviors remain obscure.
Significant progress has been made in recent years in identifying genetic factors contributing to autism. Although the genes identified have diverse biological functions, many of them are important for controlling the structure and function of the connection points between brain cells, called synapses. Alterations in synapse function affect the ability of brain cells to communicate with each other, and can lead to imbalanced or inappropriate activity in brain networks.
The core set of behavioral symptoms that define autism spectrum disorders can arise from a wide array of genetic and environmental causes. This many-to-one correspondence between genetic causes and behavioral phenotypes suggests that understanding and eventually treating autism may depend on identifying common intermediate biomarkers at the level of neural circuits or biochemical pathways.
Deletion of the 16p11.2 chromosomal region is one of the most common causes of autism spectrum disorders (ASD) and developmental delay. Individuals with 16p11.2 deletion syndrome present with intellectual disability, language impairments, social deficits and motor delays. Interestingly, the magnitude of these deficits varies substantially from one individual to another. This makes the 16p11.2 deletion carrier population especially important for understanding the complex origins of the symptoms associated with ASD and other neurodevelopmental disorders.
In addition to problems in communication and social interaction, and the presence of restricted or repetitive behaviors, individuals with autism frequently exhibit altered sensory function. Sensory issues are commonly seen in more than one domain, and the ability to synthesize or integrate information across senses is often affected. There is little empirical information, however, that systematically characterizes the sensory and multisensory deficits in people with autism, or that relates sensory changes to cognitive abilities.
Autism spectrum disorders represent a complex set of neurodevelopmental disorders that involve a combination of many different genes and environmental factors and affect multiple parts of the brain. The molecular and cellular mechanisms that lead to autism remain elusive.