Several studies have demonstrated that people with ASD and intact language skills still have problems processing linguistic information in context. Given this evidence for reduced sensitivity to linguistic context, the question arises how contextual information is actually processed by people with ASD. In this study, we used event-related brain potentials (ERPs) to examine context sensitivity in high-functioning adults with autistic disorder (HFA) and Asperger syndrome at two levels: at the level of sentence processing and at the level of solving reasoning problems. We found that sentence context as well as reasoning context had an immediate ERP effect in adults with Asperger syndrome, as in matched controls. Both groups showed a typical N400 effect and a late positive component for the sentence conditions, and a sustained negativity for the reasoning conditions. In contrast, the HFA group demonstrated neither an N400 effect nor a sustained negativity. However, the HFA group showed a late positive component which was larger for semantically anomalous sentences than congruent sentences. Because sentence context had a modulating effect in a later phase, semantic integration is perhaps less automatic in HFA, and presumably more elaborate processes are needed to arrive at a sentence interpretation.
Autism spectrum disorders (ASD) are characterized by deficits in social interaction and communication, and by restrictive, stereotyped and repetitive behaviors and narrow interests (DSM-IV, 1994). Both Asperger syndrome and autistic disorder belong to ASD, and are characterized by similar features but differ in early language development (DSM-IV, 1994). One core feature of ASD are deficits in pragmatic language, which include difficulties in understanding non-literal language like irony and metaphors (Dennis et al., 2001, Happé, 1993, Martin and McDonald, 2004 and Ozonoff and Miller, 1996). A possible account for such deficits is that people with ASD find it difficult to use context when computing meaning.
It has been demonstrated that individuals with autistic disorder or Asperger syndrome who have intact language skills, still have problems processing linguistic information in context (Happé, 1997 and Jolliffe and Baron-Cohen, 1999). In a homograph task, they failed to use sentence context to derive the appropriate pronunciation of the homographs, for instance, when they had to pronounce the homograph tear in a sentence like “In her dress/eye there was a big tear” ( Frith and Snowling, 1983, Happé, 1997 and Jolliffe and Baron-Cohen, 1999). They were also found to be less able to use contextual information to make a global inference in a sentence arrangement task, were less likely to choose a bridging inference to make a scenario coherent if they had to select from a list of alternatives, and were less able to use context to interpret ambiguous sentences ( Jolliffe and Baron-Cohen, 1999 and Jolliffe and Baron-Cohen, 2000). These findings indicate that people with ASD have difficulty understanding language in context. Moreover, of the two subgroups, people with autistic disorder had greater difficulty in using contextual information than people with Asperger syndrome ( Jolliffe and Baron-Cohen, 1999 and Jolliffe and Baron-Cohen, 2000). It has been argued that these findings support the weak central coherence account of ASD, which claims that people with ASD have a processing bias for details at the expense of the global picture ( Frith, 2003, Happé, 1999 and Happé and Frith, 2006). Given this evidence for reduced sensitivity to linguistic context, the question arises how contextual information is actually processed by people with ASD.
In the present work we used event-related brain potentials (ERPs) to examine context sensitivity in high-functioning adults with autistic disorder (HFA) and Asperger syndrome. ERPs have the advantage that they have good temporal resolution, and therefore can provide precise information about the time course of cognitive processes. Thus ERPs can give us more insight into when particular information is processed in the brain. We investigated the notion of context sensitivity in autism at two levels: at the level of sentence processing and at the level of solving reasoning problems. Both require one to make use of earlier encountered information in order to interpret the incoming new information, though the last mentioned involves a more elaborate context requiring inference making and reasoning. In the following sections, we will introduce these topics in greater detail.
