Unconstrained multivariate EEG decoding can help detect lexical-semantic processing in individual children

Funder: Macquarie UniversityAbstract: In conditions such as minimally-verbal autism, standard assessments of language comprehension are often unreliable. Given the known heterogeneity within the autistic population, it is crucial to design tests of semantic comprehension that are sensitive in individuals. Recent efforts to develop neural signals of language comprehension have focused on the N400, a robust marker of lexical-semantic violation at the group level. However, homogeneity of response in individual neurotypical children has not been established. Here, we presented 20 neurotypical children with congruent and incongruent visual animations and spoken sentences while measuring their neural response using electroencephalography (EEG). Despite robust group-level responses, we found high inter-individual variability in response to lexico-semantic anomalies. To overcome this, we analysed our data using temporally and spatially unconstrained multivariate pattern analyses (MVPA), supplemented by descriptive analyses to examine the timecourse, topography, and strength of the effect. Our results show that neurotypical children exhibit heterogenous responses to lexical-semantic violation, implying that any application to heterogenous disorders such as autism spectrum disorder will require individual-subject analyses that are robust to variation in topology and timecourse of neural responses

Unconstrained multivariate EEG decoding can help detect lexical-semantic processing in individual children

Funder: Macquarie UniversityAbstract: In conditions such as minimally-verbal autism, standard assessments of language comprehension are often unreliable. Given the known heterogeneity within the autistic population, it is crucial to design tests of semantic comprehension that are sensitive in individuals. Recent efforts to develop neural signals of language comprehension have focused on the N400, a robust marker of lexical-semantic violation at the group level. However, homogeneity of response in individual neurotypical children has not been established. Here, we presented 20 neurotypical children with congruent and incongruent visual animations and spoken sentences while measuring their neural response using electroencephalography (EEG). Despite robust group-level responses, we found high inter-individual variability in response to lexico-semantic anomalies. To overcome this, we analysed our data using temporally and spatially unconstrained multivariate pattern analyses (MVPA), supplemented by descriptive analyses to examine the timecourse, topography, and strength of the effect. Our results show that neurotypical children exhibit heterogenous responses to lexical-semantic violation, implying that any application to heterogenous disorders such as autism spectrum disorder will require individual-subject analyses that are robust to variation in topology and timecourse of neural responses

Decoding hidden language: towards a reliable neural assessment of language comprehension in minimally-verbal autistic children

Thesis by publication.Includes bibliographic references.Chapter 1. Introduction -- Chapter 2. Towards an individualised neural assessment of receptive language in children -- Chapter 3. Even neurotypical children are heterogeneous: using multivariate decoding to improve individual subject analysis of lexico-semantic EEG data -- Chapter 4. Finding hidden treasures: a child-friendly neural test of task-following in individuals using functional transcranial Doppler ultrasound -- Chapter 5. Neural assessment of lexico-semantic processing in minimally-verbal autism: a pilot case-series -- Chapter 6. Discussion -- AppendixLanguage is fundamental for cognition and social functioning, and something we often take for granted. In cases where people cannot use language to communicate, it can be difficult to evaluate cognitive abilities and the extent of spoken language understanding. In the case of minimally-verbal autistic people, accumulating evidence suggests a discrepancy between their receptive and productive language skills. In particular, it is becoming evident that at least some minimally-verbal children may understand more language than they can demonstrate. Because of the nature of their condition, including behavioural challenges and difficulties in social situations, autistic children often perform poorly on traditional measures of language such as standardised tests. Therefore, passive tests that do not require verbal answers may be more suitable. The aim of this thesis was to develop neural tests of language comprehension for minimally-verbal autistic children that do not require overt behavioural answers. Chapters 2 to 4 cover the development and validation of four paradigms in neurotypical children, and Chapter 5 presents the results of one of the paradigms applied to three minimally-verbal autistic children. In Chapter 1, I present the scope and the challenges of this work, and I review the relevant literature. In Chapter 2, I developed two child-friendly auditory paradigms that use spoken words and sentences to detect lexico-semantic processing in neurotypical children (N = 31), using electroencephalography (EEG). In this work, I also evaluated the data recording quality of a low-cost portable EEG system, Emotiv EPOC+, which provides an easy-to-setup and affordable EEG option. I compared two data analyses approaches: univariate and multivariate pattern analyses (MVPA). Three main findings emerged: first, there was large inter-individual variability in neural signals, with only around 50% of individuals showing a statically significant univariate effect. Second, the EPOC+ recorded similar signal to the research-grade system, when analysing the data with a univariate approach. Third, MVPA, which is robust to intra-individual differences in the time course and topology of effect, improved our reliability at the individual level to a maximum of 88% of children. This provided a promising avenue for a covert assessment of lexico-semantic processing in children. In Chapter 3, I extended this work and designed an updated paradigm in which I better controlled the stimuli, and added visual animations. I again found large inter-individual variability in the neural responses to semantic processing in children (N = 20), and the detection rate did not improve from Chapter 2. In Chapter 4, I turned to a novel paradigm that used functional transcranial Doppler ultrasound (fTCD) to assess mental task-following from the brain activity of neurotypical children (N = 20). I found that, for identical visual stimuli, children showed distinct lateralisation patterns when performing language and visuo-spatial memory tasks, with language being left-lateralised, and visuo-spatial memory being more bilateral. However, at the individual-subject level, I again found only half of participants showing statistically reliable task-following neural patterns. In Chapter 5, I selected the most promising paradigm (one of the EEG paradigms from Chapter 2) and tested three minimally-verbal autistic children (aged 5 to 15 years). I demonstrated that my techniques can be used with this population and I found evidence of language comprehension from one child's neural activity without requiring behavioural answers from him. Finally, in Chapter 6, I discuss the implications of these results for assessing language comprehension in minimally-verbal populations, and propose some future directions for this work. Together, this research provides a rigorous exploration of the methodological issues in using neuroimaging to assess cognition at the individual subject level, and an initial proof-of-concept that we can measure intact lexico-semantic processing in populations that may otherwise struggle to communicate -- summary.Mode of access: Internet.1 online resource (xiii, 247 pages

Finding hidden treasures: A child-friendly neural test of task-following in individuals using functional Transcranial Doppler ultrasound.

Despite growing interest in the mental life of individuals who cannot communicate verbally, objective and non-invasive tests of covert cognition are still sparse. In this study, we assessed the ability of neurotypical children to understand and follow task instructions by measuring neural responses through functional transcranial Doppler ultrasound (fTCD). We recorded blood flow velocity for the two brain hemispheres of twenty children (aged 9 to 12) while they performed either a language task or a visuospatial memory task, on identical visual stimuli. We extracted measures of neural lateralisation for the two tasks separately to investigate lateralisation, and we compared the left-minus-right pattern of activation across tasks to assess task-following. At the group level, we found that neural responses were left-lateralised when children performed the language task, and not when they performed the visuospatial task. However, with statistically robust analyses and controlled paradigms, significant lateralisation in individual children was less frequent than expected from the literature. Nonetheless, the pattern of hemispheric activation for the two tasks allowed us to confirm task-following in the group of participants, as well as in over half of the individuals. This provides a promising avenue for a covert and inexpensive test of children's ability to covertly follow task instructions and perform different mental tasks on identical stimuli.MR

Toward an Individualized Neural Assessment of Receptive Language in Children.

Purpose We aimed to develop a noninvasive neural test of language comprehension to use with nonspeaking children for whom standard behavioral testing is unreliable (e.g., minimally verbal autism). Our aims were threefold. First, we sought to establish the sensitivity of two auditory paradigms to elicit neural responses in individual neurotypical children. Second, we aimed to validate the use of a portable and accessible electroencephalography (EEG) system, by comparing its recordings to those of a research-grade system. Third, in light of substantial interindividual variability in individuals' neural responses, we assessed whether multivariate decoding methods could improve sensitivity. Method We tested the sensitivity of two child-friendly covert N400 paradigms. Thirty-one typically developing children listened to identical spoken words that were either strongly predicted by the preceding context or violated lexical-semantic expectations. Context was given by a cue word (Experiment 1) or sentence frame (Experiment 2), and participants either made an overall judgment on word relatedness or counted lexical-semantic violations. We measured EEG concurrently from a research-grade system, Neuroscan's SynAmps2, and an adapted gaming system, Emotiv's EPOC+. Results We found substantial interindividual variability in the timing and topology of N400-like effects. For both paradigms and EEG systems, traditional N400 effects at the expected sensors and time points were statistically significant in around 50% of individuals. Using multivariate analyses, detection rate increased to 88% of individuals for the research-grade system in the sentences paradigm, illustrating the robustness of this method in the face of interindividual variations in topography. Conclusions There was large interindividual variability in neural responses, suggesting interindividual variation in either the cognitive response to lexical-semantic violations and/or the neural substrate of that response. Around half of our neurotypical participants showed the expected N400 effect at the expected location and time points. A low-cost, accessible EEG system provided comparable data for univariate analysis but was not well suited to multivariate decoding. However, multivariate analyses with a research-grade EEG system increased our detection rate to 88% of individuals. This approach provides a strong foundation to establish a neural index of language comprehension in children with limited communication. Supplemental Material https://doi.org/10.23641/asha.12606311

Toward an Individualized Neural Assessment of Receptive Language in Children.

Purpose We aimed to develop a noninvasive neural test of language comprehension to use with nonspeaking children for whom standard behavioral testing is unreliable (e.g., minimally verbal autism). Our aims were threefold. First, we sought to establish the sensitivity of two auditory paradigms to elicit neural responses in individual neurotypical children. Second, we aimed to validate the use of a portable and accessible electroencephalography (EEG) system, by comparing its recordings to those of a research-grade system. Third, in light of substantial interindividual variability in individuals' neural responses, we assessed whether multivariate decoding methods could improve sensitivity. Method We tested the sensitivity of two child-friendly covert N400 paradigms. Thirty-one typically developing children listened to identical spoken words that were either strongly predicted by the preceding context or violated lexical-semantic expectations. Context was given by a cue word (Experiment 1) or sentence frame (Experiment 2), and participants either made an overall judgment on word relatedness or counted lexical-semantic violations. We measured EEG concurrently from a research-grade system, Neuroscan's SynAmps2, and an adapted gaming system, Emotiv's EPOC+. Results We found substantial interindividual variability in the timing and topology of N400-like effects. For both paradigms and EEG systems, traditional N400 effects at the expected sensors and time points were statistically significant in around 50% of individuals. Using multivariate analyses, detection rate increased to 88% of individuals for the research-grade system in the sentences paradigm, illustrating the robustness of this method in the face of interindividual variations in topography. Conclusions There was large interindividual variability in neural responses, suggesting interindividual variation in either the cognitive response to lexical-semantic violations and/or the neural substrate of that response. Around half of our neurotypical participants showed the expected N400 effect at the expected location and time points. A low-cost, accessible EEG system provided comparable data for univariate analysis but was not well suited to multivariate decoding. However, multivariate analyses with a research-grade EEG system increased our detection rate to 88% of individuals. This approach provides a strong foundation to establish a neural index of language comprehension in children with limited communication. Supplemental Material https://doi.org/10.23641/asha.12606311