Targeted Cognitive Training: Assessment and Plasticity in Autism Spectrum Disorder (ASD)

1. INTRODUCTION Autism Spectrum Disorder (ASD) is a severe neurodevelopmental disorder characterized by deficits of social and communicative skills, restricted set of interests, activities and/or repetitive behaviours that are typically observed in early childhood. The prevalence of ASD is about 1 in 68 children and it is the fastest growing developmental disability. The cost of diagnosing and treating ASD is estimated to be around $236-262 billion annually.

Plasticity broadly refers to the susceptibility of an organism to change. The human brain shows incredible plastic capacity. Multiple neuronal networks can sustain the same cognitive function (a mental ability) with different systems supporting the same function in different individuals. This "many-to-one" structure-function relationship is one form of plasticity. Examining neural networks responsible for a cognitive process in different individuals can provide insight into the plastic capacity of that process.

Cognitive training is centered on the notion of plasticity. It entails the repeated exercise of a specific cognitive process (or multiple processes) over several weeks, after which performance gains are expected on the trained task as well as various untrained tasks that directly or indirectly involve the targeted cognitive process(s). The generalization of performance gains to untrained tasks is termed "transfer" and is essential to the efficacy of the training. Cognitive training has been used to remediate deficits in adults with strokes, multiple sclerosis, Schizophrenia, children with working memory deficits , children with attention deficit hyperactivity disorder (ADHD), healthy pre-kindergarten children, as well as to enhance cognitive performance in healthy young adults, and healthy older adults. Yet, the benefits of this intervention for children with ASD have received relatively little attention.

Recent research indicates that disrupted patterns of cortical development in ASD may lead to its clinical manifestation. More specifically earlier reports have shown a pattern of reduced long-range cortical connectivity and increased localized functional connectivity in ASD. This pattern has been recently verified using highly stringent imaging analysis methods. This altered functional connectivity may be especially disruptive to cognitive functions that demand integrative information processing such as executive functioning (higher order cognitive functions that control other cognitive processes eg. Conscious control of thought and action), theory of mind, face processing, language and communication, all of which have been previously established as impaired processes in ASD.

Moreover, approximately 50-70% of children with ASD are diagnosed with intellectual disability, which manifests as cognitive impairments. Intellectual disability has been shown to place children with ASD at risk for a "low functioning" trajectory throughout life and at risk for having more severe symptoms. Cognitive training has been shown to enhance executive functions underlying intellectual capacity such as working memory, fluid intelligence, executive attention as well as academic achievement . Cognitive training delivered at an early age may strengthen the processes that are important for intellectual capacity and therefore improve the clinical trajectory of ASD.