29 Mar OTFC Journal Club: Autism Spectrum Disorders – Clinical Features and Theories
At OTFC, while we have regular PD meetings amongst the OT staff, we have also started the circulation of current research, to ensure we are keeping keeping up with research trends and best practice!
As such, we will start to share some of what we have covered in our OTFC Journal Club blog post. This week we will look at Autism Spectrum Disorders – examining current clinical features, theories and diagnosis. As the article covers quite a bit of detail and is essentially a literature review of the current evidence in this area. Rather than include all the details, we have adapted the article and included a summary of the paper by Mark Fakhoury, from the Department of Neuroscience at the University of Montreal.
Fakoury, M (2015), ‘Autistic spectrum disorders: A review of clinical features, theories and diagnosis’, International Journal of Developmental Neuroscience, vol. 43, pp 70–77
Clinical Features of ASD
Autism spectrum disorder (ASD) is a set of neurodevelopmental disorders characterised by complex behavioural phenotypes and deficits in both social and cognitive functions. Given the disorder is a spectrum, there are a range of symptoms. These can be categorised into Core and Secondary symptoms. Core symptoms include difficulty with social interaction and communication skills, as well as unusually repetitive behaviour – all that have a range of how they impact an individual. Secondary symptoms can include hyperactivity, aggression, and anxiety. The current diagnostic manual is the DSM-5, which has specific criteria, that if met, denotes diagnosis of Autism Spectrum Disorder. Criteria include difficulty with a number of social, cognitive and communication skills, as mentioned above. Early symptoms can be identified by the age of 2-3, although later diagnoses are also common.
Theories of ASD
Theory of impeded plasticity
Functional Magnetic Resonance Imaging (fMRI) studies have shown that brain activity in children with autism have morphological dysfunctions, such as long disturbance connections between pathways in the brain. These are often due to abnormalities in cellular processes, impacting development. Moreover, abnormal patterns of brain connectivity (hypo or hyper) have recently been observed in autistic children. Current findings have also highlighted that children with autism can have early over growth of certain brain structures, including the frontal cortex, amygdala and cerebellum.
Excitation and inhibition dysregulation
Neutotypical brain functioning requires a balance in the chemicals and neuronal structures that control excitation and inhibition in brain activity. Imbalances can lead to a number of neuropsychiatric disorders, one of which is ASD. Mutations and environmental factors that create an imbalance with an increase in excitatory synaptic inputs in the brain, or reduced inhibitory synaptic functioning, can lead to an increased risk of ASD. Many studies have found that individuals wirh ASD have higher levels of glutamate blood levels, suggesting higher glutamate (an excitatory neurotransmitter) levels in the brain. Alternatively, alterations in the inhibitory neurotransmitters, can account for clinical features including epileptic seizures and intellectual disabilities. Despite research in this area, it is still not very well known how these neuronal abnormalities influence brain circuitry and in turn social behaviuors.
Theory of mind
”Theory of mind (ToM) is the capacity to mentally understand subjective mental states, including thoughts and desires, regardless of whether or not the circumstances involved are real” (Fakoury, 2015, p.72). ToM studies have reveled those with ASD have significant difficulties in integrating mental state information. For children without disabilities, ToM develops early. However, for children with ASD, ToM is delayed and initial aspects of ToM require them to appreciate that people can have beliefs about things, that may not be factually correct. As adults, those with ASD also fund it difficult to understand people’s belief’s and intentions. Difficulty with ToM could explain social and communication difficulties of those with ASD. There is also the suggestions that social difficulties are a result of difficulty recognizing and appropriately responding to emotions. As such, exploring social skills in children with ASD is crucial in identifying deficits and supporting emphatic and emotional capacities.
Mirror neurons and ASD
Recent studies have looked at the role of mirror neurons in ASD. “Mirror neurons are brain cells that become active when an individual performs a given action, but also when that same action is observed” (Fakoury, 2015, p.72). They are involved in functions such as the recognising motor acts by others and regulation of social, emotional, and cognitive tasks, and dysfunction of them may create difficulties in these areas. These neurons are important for social and cognitive functions and support coordination between the motor cortex and higher visual processing areas. fMRI, electroencephalography (EEG) and electromyography (EMG) have been used to show deficits in mirror neurons in children with ASD, suggesting difficulty understanding the actions of others. However, evidence is mixed, as some studies show that the function of the mirror neuron system might be preserved in individuals with ASD, with some studies showing difficulties were not due to mirror neurons, but imitative ability – suggesting a clear dissociation between ASD and mirror neurons system. Mirror neurons are therefore an area that require further exploration.
There is more to the current ASD research story, and this will be examined next week, in part 2 of the blog topic – Causes and Diagnosis.