While three main theories have attempted to characterise autism at the cognitive level: theory of mind, executive function and central coherence; but none are able to account for all the behavioural manifestations seen across different children. The central coherence theory is quite different in nature to the mentalising and executive function theories as it proposes a different information processing style rather than a specific deficit. It attempts to account for some of the non-diagnostic features of autism, namely the islets of ability and the savant skills seen in a proportion of individuals with the disorder. This cognitive processing style is thought to be characterised by a bias towards detail-focussed processing. While the cognitive basis remains controversial, one strong hypothesis is that there are high processing costs associated with changing from local into global processing. A possible neural mechanism underlying this processing style is abnormal neural connectivity; specifically an excess of inefficient feedback connections might lead to good exemplar-based processing but poor generalisation. This same neural mechanism has also been suggested to account for the increased incidence of macrocephaly in autism (increased head/brain size). The present study therefore investigated the effect of head size on the ability to switch between global and local processing in autism. 49 high- functioning 7-12 year olds with autism (12 with macrocephaly) were compared to 25 normally developing children in their performance on a Local-Global Switching task. Those children with autism who also had macrocephaly showed a greater processing cost when switching into global processing, or zooming out, than the remaining children with autism. A second experiment revealed that macrocephaly in the context of normal development is not associated with difficulty switching into global processing but rather occurs in children who are physically large. Macrocephaly in the context of autism may therefore be a biological marker of weak central coherence.

time: 2 pm

date: november 6th

place: the box, trøjborgvej 72 

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