Altered semantic integration in autism beyond language: a cross-modal event-related potentials study

Children with autism spectrum disorder who demonstrate normal language scores use a bottom-up semantic processing strategy: Evidence from N400 recordings

INTRODUCTION

The N400 is an electrophysiological component that reflects lexical access and integration of words with mental representations.

METHODS

Thirty-five young children with a range of language capabilities (n = 21 neurotypical controls, 10 males, mean age = 6.3 ± 0.9 years; n = 14 children with autism, 12 males, mean age = 6.4 ± 1.1 years) completed an auditory semantic categorization paradigm to evoke the N400. Electroencephalograph (EEG) data were acquired with a 64-channel electrode cap as children listened via ear inserts to binaurally presented single syllable words and decided whether the words were congruent (in) or incongruent (out) with a pre-specified category. EEG data were filtered, epoched, and averaged referenced, and global field power (GFP) was computed. The amplitude of the N400 peak in the GFP was submitted to a multiple linear regression analysis.

RESULTS

N400 amplitude was found to predict language scores only for the children with ASD who have language scores in the normal range (r2  = 0.72).

CONCLUSIONS

This finding that N400 amplitude only predicted language scores in children with ASD and normal language scores suggests that these children may rely more on basic semantic processing (as reflected by the N400) and less on anticipating and predicting upcoming words. This suggests preferential utilization of a bottom-up strategy to access higher order language.

Spatiotemporal evidence uncovers differential neural activity patterns in cognitive and affective conflict control

Studies have shown that there are overlapping neural bases for cognitive and affective conflict control, but whether the neural activity patterns caused by the two types of conflict are similar remains to be explored. The present study utilizes electroencephalogram (EEG) and functional magnetic resonance imaging (fMRI) to temporally and spatially analyze the differences between cognitive and affective conflict control. We employ a semantic conflict task which includes blocks of cognitive and affective judgements primed by conflicting and non-conflicting contexts. The results showed a typical neural conflict effect in the cognitive judgment blocks as reflected by greater amplitudes of P2, N400, and the late positive potential (LPP), as well as greater activation of the left pre-supplementary motor area (pre-SMA) and the right inferior frontal gyrus (IFG) in the conflict condition relative to the non-conflict condition. These patterns did not emerge in the affective judgments, but instead, showed reversed effects of the LPP and in the left SMA. Taken together, these findings suggest that cognitive and affective conflict control result in different neural activity patterns.

Mapping access to meaning in adolescents with autism: Atypical lateralization and spatiotemporal patterns as a function of language ability

Individuals with autism spectrum disorders (ASD) vary in their language abilities, associated with atypical patterns of brain activity. However, few studies have examined the spatiotemporal profiles of lexico-semantic processing in ASD, particularly as a function of language heterogeneity. Thirty-nine high-functioning adolescents with ASD and 21 typically developing (TD) peers took part in a lexical decision task that combined semantic access with demands on cognitive control. Spatiotemporal characteristics of the processing stages were examined with a multimodal anatomically-constrained magnetoencephalography (aMEG) approach, which integrates MEG with structural MRI. Additional EEG data were acquired from a limited montage simultaneously with MEG. TD adolescents showed the canonical left-dominant activity in frontotemporal regions during both early (N250m) and late (N400m) stages of lexical access and semantic integration. In contrast, the ASD participants showed bilateral engagement of the frontotemporal language network, indicative of compensatory recruitment of the right hemisphere. The left temporal N400m was prominent in both groups, confirming preserved attempts to access meaning. In contrast, the left prefrontal N400m was reduced in ASD participants, consistent with impaired semantic/contextual integration and inhibitory control. To further investigate the impact of language proficiency, the ASD sample was stratified into high- and low-performing (H-ASD and L-ASD) subgroups based on their task accuracy. The H-ASD subgroup performed on par with the TD group and showed greater activity in the right prefrontal and bilateral temporal cortices relative to the L-ASD subgroup, suggesting compensatory engagement. The L-ASD subgroup additionally showed reduced and delayed left prefrontal N400m, consistent with more profound semantic and executive impairments in this subgroup. These distinct spatiotemporal activity profiles reveal the neural underpinnings of the ASD-specific access to meaning and provide insight into the phenotypic heterogeneity of language in ASD, which may be a result of different neurodevelopmental trajectories and adoption of compensatory strategies.

Evoking the N400 Event-related Potential (ERP) Component Using a Publicly Available Novel Set of Sentences with Semantically Incongruent or Congruent Eggplants (Endings)

During speech comprehension, the ongoing context of a sentence is used to predict sentence outcome by limiting subsequent word likelihood. Neurophysiologically, violations of context-dependent predictions result in amplitude modulations of the N400 event-related potential (ERP) component. While N400 is widely used to measure semantic processing and integration, no publicly-available auditory stimulus set is available to standardize approaches across the field. Here, we developed an auditory stimulus set of 442 sentences that utilized the semantic anomaly paradigm, provided cloze probability for all stimuli, and was developed for both children and adults. With 20 neurotypical adults, we validated that this set elicits robust N400′s, as well as two additional semantically-related ERP components: the recognition potential (~250 ms) and the late positivity component (~600 ms). This stimulus set (https://doi.org/10.5061/dryad.9ghx3ffkg) and the 20 high-density (128-channel) electrophysiological datasets (https://doi.org/10.5061/dryad.6wwpzgmx4) are made publicly available to promote data sharing and reuse. Future studies that use this stimulus set to investigate sentential semantic comprehension in both control and clinical populations may benefit from the increased comparability and reproducibility within this field of research.

Children with autism spectrum disorder show atypical electroencephalographic response to processing contextual incongruencies

Children with autism spectrum disorder (ASD) experience difficulties with social communication, making it challenging to interpret contextual information that aids in accurately interpreting language. To investigate how the brain processes the contextual information and how this is different in ASD, we compared event-related potentials (ERPs) in response to processing visual and auditory congruent and incongruent information. Two groups of children participated in the study: 37 typically developing children and 15 children with ASD (age range = 6 to 12). We applied a language task involving auditory sentences describing congruent or incongruent images. We investigated two ERP components associated with language processing: the N400 and P600. Our results showed how children with ASD present significant differences in their neural responses in comparison with the TD group, even when their reaction times and correct trials are not significantly different from the TD group.

The time-locked neurodynamics of semantic processing in autism spectrum disorder: an EEG study

Language processing is often an area of difficulty in Autism Spectrum Disorder (ASD). Semantic processing-the ability to add meaning to a stimulus-is thought to be especially affected in ASD. However, the neurological origin of these deficits, both structurally and temporally, have yet to be discovered. To further previous behavioral findings on language differences in ASD, the present study used an implicit semantic priming paradigm and electroencephalography (EEG) to compare the level of theta coherence throughout semantic processing, between typically developing (TD) and ASD participants. Theta coherence is an indication of synchronous EEG oscillations and was of particular interest due to its previous links with semantic processing. Theta coherence was analyzed in response to semantically related or unrelated pairs of words and pictures across bilateral short, medium, and long electrode connections. We found significant results across a variety of conditions, but most notably, we observed reduced coherence for language stimuli in the ASD group at a left fronto-parietal connection from 100 to 300 ms. This replicates previous findings of underconnectivity in left fronto-parietal language networks in ASD. Critically, the early time window of this underconnectivity, from 100 to 300 ms, suggests that impaired semantic processing of language in ASD may arise during pre-semantic processing, during the initial communication between lower-level linguistic processing and higher-level semantic processing. Our results suggest that language processing functions are unique in ASD compared to TD, and that subjects with ASD might rely on a temporally different language processing loop altogether.

Psychological and Neural Differences of Music Processing in Autistic Individuals: A Scoping Review

Despite abundant research and clinical evidence of the effectiveness of music interventions for people in the autism spectrum, understanding of music processing in this community is limited. We explored whether research evidence of differences in music processing within the autistic community is available. We developed a scoping review to search for literature with the terms "music", "processing," and "autism" (and variants). We searched PubMed, CINAHL, Scopus, Web of Science, PsycInfo, Academic Search Complete, ERIC, and Music Index databases for a total of 10,857 articles, with 5,236 duplicates. The remaining 5,621 titles and abstracts were screened for eligibility by a team of four undergraduate and graduate students and the PI. Seventy-five studies were included for data extraction. Data were analyzed with descriptive statistics regarding author, study, stimulus, and participant information, and a thematic analysis of outcome and findings. Our findings are preliminary given the emerging nature of the literature, the use of mostly non-musical auditory stimuli, passive listening experiences, and underreported demographics. However, the literature shows some evidence of differences in music processing for autistic individuals, including reduced habituation to non-musical and musical stimuli; truncated, delayed, or divergent developmental trajectories; and possible compensatory higher-order mechanisms that yield similar behavioral responses even in the presence of divergent neural correlates. Music therapists are encouraged to adopt a developmental perspective, not only of general skills, but specifically of music skill development in this community, and to extrapolate these findings with caution, given the current limitations in the evidence.

Speech Processing in Autism Spectrum Disorder: An Integrative Review of Auditory Neurophysiology Findings

Purpose Investigations into the nature of communication disorders in autistic individuals increasingly evaluate neural responses to speech stimuli. This integrative review aimed to consolidate the available data related to speech and language processing across levels of stimulus complexity (from single speech sounds to sentences) and to relate it to the current theories of autism. Method An electronic database search identified peer-reviewed articles using event-related potentials or magnetoencephalography to investigate auditory processing from single speech sounds to sentences in autistic children and adults varying in language and cognitive abilities. Results Atypical neural responses in autistic persons became more prominent with increasing stimulus and task complexity. Compared with their typically developing peers, autistic individuals demonstrated mostly intact sensory responses to single speech sounds, diminished spontaneous attentional orienting to spoken stimuli, specific difficulties with categorical speech sound discrimination, and reduced processing of semantic content. Atypical neural responses were more often observed in younger autistic participants and in those with concomitant language disorders. Conclusions The observed differences in neural responses to speech stimuli suggest that communication difficulties in autistic individuals are more consistent with the reduced social interest than the auditory dysfunction explanation. Current limitations and future directions for research are also discussed.

Developmental differences in neural connectivity for semantic processing in youths with autism

BACKGROUND

Youths with autism spectrum disorder (ASD) rely more on lower-level visual processing as revealed by greater occipital activation, yet less effectively engage higher-level processing of modality-independent semantic knowledge as indicated by reduced frontal activation, compared to typically developing (TD) youths. However, little is known about age-dependent differences in neural connectivity during semantic processing in youths with ASD as compared to TD youths.

METHODS

Four groups were recruited: 31 ASD children (mean age = 10.5 years old), 33 TD children (mean age = 10.4), 30 ASD adolescents (mean age = 14.9), and 34 TD adolescents (mean age = 15.1). We explored their differences in neural connectivity by using functional magnetic resonance imaging (fMRI) with psychophysiological interaction (PPI) during semantic judgments.

RESULTS

In comparison with TD children, children with ASD showed greater activation in the left cuneus and weaker connectivity between the left cuneus and left middle temporal gyrus (MTG). In comparison with TD adolescents, adolescents with ASD showed less activation in the left inferior frontal gyrus (IFG) and weaker functional connectivity between the left IFG and left MTG.

CONCLUSIONS

Children with ASD may rely more on visual processes in the occipital cortex that are disconnected from modality-independent semantics in the temporal cortex. However, adolescents with ASD may less effectively engage frontal mechanisms involved in the top-down control of modality-independent semantic knowledge in the temporal cortex. Our findings provide evidence of developmental differences in the neural substrates of the alterations in semantic processing in youths with ASD compared to TD youths.

The electrophysiology of audiovisual processing in visual narratives in adolescents with autism spectrum disorder

We investigated the semantic processing of the multimodal audiovisual combination of visual narratives with auditory descriptive words and auditory sounds in individuals with ASD. To this aim, we recorded ERPs to critical auditory words and sounds associated with events in visual narrative that were either semantically congruent or incongruent with the climactic visual event. A similar N400 effect was found both in adolescents with ASD and neurotypical adolescents (ages 9-16) when accessing different types of auditory information (i.e. words and sounds) into a visual narrative. This result might suggest that verbal information processing in ASD adolescents could be facilitated by direct association with meaningful visual information. In addition, we observed differences in scalp distribution of later brain responses between ASD and neurotypical adolescents. This finding might suggest ASD adolescents differ from neurotypical adolescents during the processing of the multimodal combination of visual narratives with auditory information at later stages of the process. In conclusion, the semantic processing of verbal information, typically impaired in individuals with ASD, can be facilitated when embedded into a meaningful visual information.

MEG Theta during Lexico-Semantic and Executive Processing Is Altered in High-Functioning Adolescents with Autism

Neuroimaging studies have revealed atypical activation during language and executive tasks in individuals with autism spectrum disorders (ASD). However, the spatiotemporal stages of processing associated with these dysfunctions remain poorly understood. Using an anatomically constrained magnetoencephalography approach, we examined event-related theta oscillations during a double-duty lexical decision task that combined demands on lexico-semantic processing and executive functions. Relative to typically developing peers, high-functioning adolescents with ASD had lower performance accuracy on trials engaging selective semantic retrieval and cognitive control. They showed an early overall theta increase in the left fusiform cortex followed by greater activity in the left-lateralized temporal (starting at ~250 ms) and frontal cortical areas (after ~450 ms) known to contribute to language processing. During response preparation and execution, the ASD group exhibited elevated theta in the anterior cingulate cortex, indicative of greater engagement of cognitive control. Simultaneously increased activity in the ipsilateral motor cortex may reflect a less lateralized and suboptimally organized motor circuitry. Spanning early sensory-specific and late response selection stages, the higher event-related theta responsivity in ASD may indicate compensatory recruitment to offset inefficient lexico-semantic retrieval under cognitively demanding conditions. Together, these findings provide further support for atypical language and executive functions in high-functioning ASD.

The Neurobiology of Semantic Processing in Autism Spectrum Disorder: An Activation Likelihood Estimation Analysis

Semantic processing impairments are present in a proportion of individuals with autism spectrum disorder (ASD). Despite the numerous imaging studies investigating this language domain in ASD, there is a lack of consensus regarding the brain structures showing abnormal pattern of activity. This meta-analysis aimed to identify neural activation patterns present during semantic processing in ASD. Findings reveal activation of areas associated with semantic processing and executive functions in ASD. However, the activation was less concise in comparison to controls and there was less activation in the right hemisphere and in areas associated with executive functions. This provides strong support for impaired semantic processing in ASD that is consistently associated with abnormal patterns of neural activity in the semantic network.

Visual and Verbal Narrative Comprehension in Children and Adolescents with Autism Spectrum Disorders: An ERP Study

We examined semantic processing in ASD children by presenting sentences with congruent or incongruent final words and visual narratives with congruent or incongruent final panels. An N400 effect to incongruent words appeared as compared to congruent ones, which was attenuated for the ASD children. We observed a negativity sustained to incongruous than congruous words, but only for the TD children. Incongruent panels evoked a greater fronto-central N400 amplitude than congruent panels in both groups. In addition, incongruent panels evoked a centro-parietal late positivity, only in controls. In conclusion, ASD children face processing deficits in both verbal and visual materials when integrating meaning across information, though such impairments may arise in different parts of the interpretive process, depending on the modality.

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

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.

ERP evidence of semantic processing in children with ASD

25% of children with autism spectrum disorder (ASD) remain minimally verbal (MV), despite intervention. Electroencephalography can reveal neural mechanisms underlying language impairment in ASD, potentially improving our ability to predict language outcomes and target interventions. Verbal (V) and MV children with ASD, along with an age-matched typically developing (TD) group participated in a semantic congruence ERP paradigm, during which pictures were displayed followed by the expected or unexpected word. An N400 effect was evident in all groups, with a shorter latency in the TD group. A late negative component (LNC) also differentiated conditions, with a group by condition by region interaction. Post hoc analyses revealed that the LNC was present across multiple regions in the TD group, in the mid-frontal region in MVASD, and not present in the VASD group. Cluster analysis identified subgroups within the ASD participants. Two subgroups showed markedly atypical patterns of processing, one with reversed but robust differentiation of conditions, and the other with initially reversed followed by typical differentiation. Findings indicate that children with ASD, including those with minimal language, showed EEG evidence of semantic processing, but it was characterized by delayed speed of processing and limited integration with mental representations.

The Real-Time Comprehension of Idioms by Typical Children, Children with Specific Language Impairment and Children with Autism

Objective

We examined on-line auditory idiom comprehension in typically developing (TD) children, children with specific language impairment (SLI), and children with autism. Theories of idiom processing in adults agree on a reliance on lexical/semantic memory for these forms, but differ in their specifics. The Lexical Representation hypothesis claims that literal and non-literal meanings are activated in parallel. The Configuration hypothesis claims that a non-literal meaning will take precedence, such that a literal meaning may not be activated at all.

Method

Children aged 6–16 years listened to sentences containing idioms for a cross-modal priming task. The idioms were ambiguous between an idiomatic and a literal meaning. We looked at priming for both meanings at the offset of the idiom.

Results

TD children (n=14) and children with SLI (n=7) primed for the idiomatic but not literal meaning of the idiom. Children with autism (n=5) instead primed for the literal but not idiomatic meaning.

Conclusions

TD children showed an adult-like pattern, consistent with predictions of the Configuration Hypothesis. Children with SLI showed the typical pattern, whereas the atypical pattern observed for children with autism may reflect a particular deficit with complex material in semantic memory.