place: Aarhus University Hospital, Risskov, Skovagervej 2, 8240 Risskov, denmark 

time: 11.10 am-12.15 pm

Autism is widely acknowledged to be a neurodevelopmental disorder with a genetic basis, resulting in atypical development of the brain.  Despite this assertion, very little is known about the exact genetic or biological abnormalities underlying the disorder and so diagnosis relies upon a defined set of behavioural criteria.  Although necessary, a behavioural diagnosis has the disadvantage of heterogeneity; there can be many different reasons for or causes of the same behaviour.  Equally, different behaviours in different individuals can result from the same underlying cause due to interaction with other factors.  In order to accommodate such behavioural heterogeneity, the notion of an autism spectrum has been introduced, varying in multiple directions including severity of symptoms and the pattern of symptoms present at different developmental stages and general ability levels.

Such heterogeneity at the behavioural level of course makes the identification of the biological or genetic underpinnings of autism extremely difficult.  An intermediary level of explanation between biology and behaviour is therefore helpful, describing the functions of the brain in terms of the cognitive systems they may mediate and allowing a range of behaviours to be linked to a unitary cause.  Three main theories have attempted to characterise autism at the cognitive level: theory of mind (ToM), executive function (EF) and central coherence (CC).  However, whilst they attempt to draw a variety of different behaviours together through a common cognitive cause, none appear able to account for all the behavioural manifestations seen across different children.

In order to investigate cognitive heterogeneity within the autism spectrum and how this relates to reported behaviour, 57 high-functioning 7-12 year olds with autism spectrum disorder (ASD) and 27 normally-developing children performed tasks tapping into these three cognitive domains.  Their parents completed interviews concerning their behavioural symptoms.  Support for all three theories was found, with significant group differences between the ASD and control groups.  We then identified the children who showed detectable impairment, defined as performance below the control group 5th percentile, in each cognitive domain.  Approximately 50% of the children with ASD displayed a ToM impairment, 33% executive dysfunction and 20% weak CC, and all possible combinations were found.  A further puzzling 40% of children displayed no detectable impairment.  ToM and EF abilities were closely related whilst CC was independent of these skills, indicating that at least two cognitive subtypes were present in the current sample.  However, only ToM and verbal ability were found to predict specific aspects of the behavioural triad.

These findings highlight the need to treat the autism spectrum as a heterogeneous group of individuals with different underlying cognitive impairments that cannot be assumed to be universal; any interventional approach is therefore unlikely to benefit every child.  Cognitive assessment may therefore be advantageous both for diagnosis and in treatment planning.

date: november 9th

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