Early ERF responses to final words in a sentence context during reading in individuals with autism spectrum disorders and typically developing individuals: an MEG study

Abstract

Event Abstract Back to Event Early ERF responses to final words in a sentence context during reading in individuals with autism spectrum disorders and typically developing individuals: an MEG study Banu Ahtam1*, Sven Braeutigam1 and Anthony Bailey1 1 University of Oxford, United Kingdom This study used magnetoencephalography (MEG) to study the neural basis of abnormalities in sentence context effects in individuals with an autism spectrum disorder (ASD). 22 individuals with ASD and 22 typically developing (TD) individuals participated in the study. Participants were matched on age, gender, and IQ. All measurements were taken at the Oxford Neurodevelopmental Magnetoencephalography Centre using a Neuromag-306 VectorViewTM system, providing a helmet-shaped array of 102 pairs of gradiometers. Participants read sentences ending either with a homonym [dominant (DH) vs. subordinate (SH) meanings] or an unambiguous word (UW). The sentences were followed by a probe word that was semantically related or unrelated to the meaning of the sentence. Participants were asked to indicate whether the probe word was related or unrelated to the meaning of the sentence that it followed and to give their responses with a key press. This study has been approved by the local NHS (UK) Ethics Committee. All participants gave written informed consent before the experiment. The final word results showed that the ERF responses around 150ms were weaker and a little delayed in the ASD group. The rank ordering of amplitude strengths for ~150ms response to final words was the same in the TD and ASD groups (DH > UW > SH). Activity was observed over parietal and left occipito-temporal regions in both groups, but the left posterior temporal activity was reduced in ASD. The argument that semantic access can take place as early as 150-180ms [1] is supported by the findings of this study. The reduced activity in SH was more pronounced in the ASD group suggesting different semantic representations for more and less frequent meanings of the homonyms in the ASD than the TD group. Additionally, delayed responses to final words at ~150ms in ASD may suggest differences in the time course of semantic context influences on the semantic activation of the final words between TD and ASD.