Semantic Processing in Autism Spectrum Disorders Is Associated With the Timing of Language Acquisition: A Magnetoencephalographic Study

Abstract

Individuals with autism show difficulties in using sentence context to identify the correct meaning of ambiguous words, such as homonyms. In this study, the brain basis of sentence context effects on word understanding during reading was examined in autism spectrum disorder (ASD) and typical development (TD) using magnetoencephalography. The correlates of a history of developmental language delay in ASD were also investigated. Event related field responses at early (150 ms after the onset of a final word) and N400 latencies are reported for three different types of sentence final words: dominant homonyms, subordinate homonyms, and unambiguous words. Clear evidence for semantic access was found at both early and conventional N400 latencies in both TD participants and individuals with ASD with no history of language delay. By contrast, modulation of evoked activity related to semantic access was weak and not significant at early latencies in individuals with ASD with a history of language delay. The reduced sensitivity to semantic context in individuals with ASD and language delay was accompanied by strong right hemisphere lateralization at early and N400 latencies; such strong activity was not observed in TD individuals and individuals with ASD without a history of language delay at either latency. These results provide new evidence and support for differential neural mechanisms underlying semantic processing in ASD, and indicate that delayed language acquisition in ASD is associated with different lateralization and processing of language.

Keywords: N400; autism; language; magnetoencephalography; semantics.

FIGURE 1

(A) Global activations (RMS-curves) for three final words (dominant homonym, subordinate homonym, and unambiguous word) in TD and ASD groups. (B) Global activations (RMS-curves) for three final word conditions in NLD and LD groups.

FIGURE 2

(A) First row: Local RMS-maps for the TD group’s responses to final words (dominant homonym, subordinate homonym, and unambiguous word) at 150 ms. Second row: Local RMS-maps for the ASD group’s responses to final words (dominant homonym, subordinate homonym, and unambiguous word) at 150 ms. (B) First row: TD group’s Friedman analysis result for dominant homonym, subordinate homonym, and unambiguous word at 150 ms. Wilcoxon pairwise analysis result of dominant homonym and subordinate homonym, dominant homonym and unambiguous word, and subordinate homonym and unambiguous word at 150 ms. Second row: ASD group’s Friedman analysis result for dominant homonym, subordinate homonym, and unambiguous word at 150 ms. Wilcoxon pairwise analysis result of dominant homonym and subordinate homonym, dominant homonym and unambiguous word, and subordinate homonym and unambiguous word at 150 ms. (C) Mann–Whitney U analysis result for TD vs. ASD groups’ responses to final words (dominant homonym, subordinate homonym, and unambiguous word) at 150 ms. For the presentation of data, the detectors have been projected into two dimensions (right ear on the right, front at the top).

FIGURE 3

(A) First row: Local RMS-maps for the NLD group’s responses to final words (dominant homonym, subordinate homonym, and unambiguous word) at 150 ms. Second row: Local RMS-maps for the LD group’s responses to final words (dominant homonym, subordinate homonym, and unambiguous word) at 150 ms. (B) First row: NLD group’s Friedman analysis result for dominant homonym, subordinate homonym, and unambiguous word at 150 ms. Wilcoxon pairwise analysis result of dominant homonym and subordinate homonym, dominant homonym and unambiguous word, and subordinate homonym and unambiguous word at 150 ms. Second row: LD group’s Friedman analysis result for dominant homonym, subordinate homonym, and unambiguous word at 150 ms. Wilcoxon pairwise analysis result of dominant homonym and subordinate homonym, dominant homonym and unambiguous word, and subordinate homonym and unambiguous word at 150 ms. (C) Mann–Whitney U analysis result for NLD vs. LD groups’ responses to final words (dominant homonym, subordinate homonym, and unambiguous word) at 150 ms. For the presentation of data, the detectors have been projected into two dimensions (right ear on the right, front at the top).

FIGURE 4

(A) First row: Local RMS-maps for the TD group’s responses to final words (dominant homonym, subordinate homonym, and unambiguous word) at 400 ms. Second row: Local RMS-maps for the ASD group’s responses to final words (dominant homonym, subordinate homonym, and unambiguous word) at 400 ms. (B) First row: TD group’s Friedman analysis result for dominant homonym, subordinate homonym, and unambiguous word at 400 ms. Wilcoxon pairwise analysis result of dominant homonym and subordinate homonym, dominant homonym and unambiguous word, and subordinate homonym and unambiguous word at 400 ms. Second row: ASD group’s Friedman analysis result for dominant homonym, subordinate homonym, and unambiguous word at 400 ms. Wilcoxon pairwise analysis result of dominant homonym and subordinate homonym, dominant homonym and unambiguous word, and subordinate homonym and unambiguous word at 400 ms. (C) Mann–Whitney U analysis result for TD vs. ASD groups’ responses to final words (dominant homonym, subordinate homonym, and unambiguous word) at 400 ms. For the presentation of data, the detectors have been projected into two dimensions (right ear on the right, front at the top).

FIGURE 5

(A) First row: Local RMS-maps for the NLD group’s responses to final words (dominant homonym, subordinate homonym, and unambiguous word) at 400 ms. Second row: Local RMS-maps for the LD group’s responses to final words (dominant homonym, subordinate homonym, and unambiguous word) at 400 ms. (B) First row: NLD group’s Friedman analysis result for dominant homonym, subordinate homonym, and unambiguous word at 400 ms. Wilcoxon pairwise analysis result of dominant homonym and subordinate homonym, dominant homonym and unambiguous word, and subordinate homonym and unambiguous word at 400 ms. Second row: LD group’s Friedman analysis result for dominant homonym, subordinate homonym, and unambiguous word at 400 ms. Wilcoxon pairwise analysis result of dominant homonym and subordinate homonym, dominant homonym and unambiguous word, and subordinate homonym and unambiguous word at 400 ms. (C) Mann–Whitney U analysis result for NLD vs. LD groups’ responses to final words (dominant homonym, subordinate homonym, and unambiguous word) at 400 ms. For the presentation of data, the detectors have been projected into two dimensions (right ear on the right, front at the top).

FIGURE 6

(A) Top row: TD group’s local RMS-maps for dominant homonym, subordinate homonym, and unambiguous word at 450 ms. Bottom row: ASD group’s local RMS-maps for dominant homonym, subordinate homonym, and unambiguous word at 450 ms. (B) Top row: NLD group’s local RMS-maps for dominant homonym, subordinate homonym, and unambiguous word at 450 ms. Bottom row: LD group’s local RMS-maps for dominant homonym, subordinate homonym, and unambiguous word at 450 ms. For the presentation of data, the detectors have been projected into two dimensions (right ear on the right, front at the top).