It’s all about time : Precision and accuracy of Emotiv event-marking for ERPD research

Background The use of consumer-grade electroencephalography (EEG) systems for research purposes has become more prevalent. In event-related potential (ERP) research, it is critical that these systems have precise and accurate timing. The aim of the current study was to investigate the timing reliability of event-marking solutions used with Emotiv commercial EEG systems. Method We conducted three experiments. In Experiment 1 we established a jitter threshold (i.e. the point at which jitter made an event-marking method unreliable). To do this, we introduced statistical noise to the temporal position of event-marks of a pre-existing ERP dataset (recorded with a research-grade system, Neuroscan SynAmps2 at 1,000 Hz using parallel-port event-marking) and calculated the level at which the waveform peaks differed statistically from the original waveform. In Experiment 2 we established a method to identify ‘true’ events (i.e. when an event should appear in the EEG data). We did this by inserting 1,000 events into Neuroscan data using a custom-built event-marking system, the ‘Airmarker’, which marks events by triggering voltage spikes in two EEG channels. We used the lag between Airmarker events and events generated by Neuroscan as a reference for comparisons in Experiment 3. In Experiment 3 we measured the precision and accuracy of three types of Emotiv event-marking by generating 1,000 events, 1 s apart. We measured precision as the variability (standard deviation in ms) of Emotiv events and accuracy as the mean difference between Emotiv events and true events. The three triggering methods we tested were: (1) Parallel-port-generated TTL triggers; (2) Arduino-generated TTL triggers; and (3) Serial-port triggers. In Methods 1 and 2 we used an auxiliary device, Emotiv Extender, to incorporate triggers into the EEG data. We tested these event-marking methods across three configurations of Emotiv EEG systems: (1) Emotiv EPOC+ sampling at 128 Hz; (2) Emotiv EPOC+ sampling at 256 Hz; and (3) Emotiv EPOC Flex sampling at 128 Hz. Results In Experiment 1 we found that the smaller P1 and N1 peaks were attenuated at lower levels of jitter relative to the larger P2 peak (21 ms, 16 ms, and 45 ms for P1, N1, and P2, respectively). In Experiment 2, we found an average lag of 30.96 ms for Airmarker events relative to Neuroscan events. In Experiment 3, we found some lag in all configurations. However, all configurations exhibited precision of less than a single sample, with serial-port-marking the most precise when paired with EPOC+ sampling at 256 Hz. Conclusion All Emotiv event-marking methods and configurations that we tested were precise enough for ERP research as the precision of each method would provide ERP waveforms statistically equivalent to a research-standard system. Though all systems exhibited some level of inaccuracy, researchers could easily account for these during data processing

Case study: auditory brain responses in a minimally verbal child with autism and cerebral palsy

An estimated 30% of individuals with autism spectrum disorders (ASD) remain minimally verbal into late childhood, but research on cognition and brain function in ASD focuses almost exclusively on those with good or only moderately impaired language. Here we present a case study investigating auditory processing of GM, a nonverbal child with ASD and cerebral palsy. At the age of 8 years, GM was tested using magnetoencephalography (MEG) whilst passively listening to speech sounds and complex tones. Where typically developing children and verbal autistic children all demonstrated similar brain responses to speech and nonspeech sounds, GM produced much stronger responses to nonspeech than speech, particularly in the 65–165 ms (M50/M100) time window post-stimulus onset. GM was retested aged 10 years using electroencephalography (EEG) whilst passively listening to pure tone stimuli. Consistent with her MEG response to complex tones, GM showed an unusually early and strong response to pure tones in her EEG responses. The consistency of the MEG and EEG data in this single case study demonstrate both the potential and the feasibility of these methods in the study of minimally verbal children with ASD. Further research is required to determine whether GM's atypical auditory responses are characteristic of other minimally verbal children with ASD or of other individuals with cerebral palsy

Self-concept in poor readers : A systematic review and meta-analysis

Background The aims of this systematic review and meta-analyses were to determine if there is a statistically reliable association between poor reading and poor self-concept, and if such an association is moderated by domain of self-concept, type of reading impairment, or contextual factors including age, gender, reading instruction, and school environment. Methodology We searched 10 key databases for published and unpublished studies, as well as reference lists of included studies, and studies that cited included studies. We calculated standardised mean differences (SMDs) and 95% confidence intervals for one primary outcome (average self-concept) and 10 secondary outcomes (10 domains of self-concept). We assessed the data for risk of bias, heterogeneity, sensitivity, reporting bias, and quality of evidence. Results Thirteen studies with 3,348 participants met our selection criteria. Meta-analyses revealed statistically significant SMDs for average self-concept (−0.57) and five domains of self-concept (reading/writing/spelling: −1.03; academic: −0.67; math: −0.64; behaviour: −0.32; physical appearance: −0.28). The quality of evidence for the primary outcome was moderate, and for secondary outcomes was low, due to lack of data. Conclusions These outcomes suggest a probable moderate association between poor reading and average self-concept; a possible strong association between poor reading and reading-writing-spelling self-concept; and possible moderate associations between poor reading and self-concept in the self-concept domains of academia, mathematics, behaviour, and physical appearance

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

The attentional blink is related to phonemic decoding, but not sight-word recognition, in typically reading adults

This research investigated the relationship between the attentional blink (AB) and reading in typical adults. The AB is a deficit in the processing of the second of two rapidly presented targets when it occurs in close temporal proximity to the first target. Specifically, this experiment examined whether the AB was related to both phonological and sight-word reading abilities, and whether the relationship was mediated by accuracy on a single-target rapid serial visual processing task (single-target accuracy). Undergraduate university students completed a battery of tests measuring reading ability, non-verbal intelligence, and rapid automatised naming, in addition to rapid serial visual presentation tasks in which they were required to identify either two (AB task) or one (single target task) target/s (outlined shapes: circle, square, diamond, cross, and triangle) in a stream of random-dot distractors. The duration of the AB was related to phonological reading (n=41, ß=-0.43): participants who exhibited longer ABs had poorer phonemic decoding skills. The AB was not related to sight-word reading. Single-target accuracy did not mediate the relationship between the AB and reading, but was significantly related to AB depth (non-linear fit, R2 = .50): depth reflects the maximal cost in T2 reporting accuracy in the AB. The differential relationship between the AB and phonological versus sight-word reading implicates common resources used for phonemic decoding and target consolidation, which may be involved in cognitive control. The relationship between single-target accuracy and the AB is discussed in terms of cognitive preparation

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

AC loss in REBCO coil windings wound with various cables: effect of current distribution among the cable strands

To construct large-scale superconducting devices, it is critical to enhance the current carrying capability of superconducting coils. One practical approach is to utilise assembled cables, composed of multiple strands, for the winding. There have only been a few investigations of the dependence of current distribution among the strands on the AC losses of the cables and coils wound with these cables. In this work, we studied three types of cables; i) 8/2 (eight 2 mm-wide strands) Roebel cable, 8/2 Roebel; ii) two parallel stacks (TPS) which have the same geometrical dimensions as the Roebel cable, 8/2 TPS; and iii) an equivalent four-conductor stack (ES) comprising four 4 mm-wide conductors, 4/4 ES. We proposed a new numerical approach that can achieve equal current sharing and free current sharing among the strands. We examined the loss behaviour of all three types of straight cables and two coil assemblies comprising two, and eight, stacks of double pancakes (DPCs) wound with these cables, respectively. 2D FEM analysis was carried out in COMSOL Multiphysics using the H - formulation. The stacks were modelled in parallel connection, with the same electric field applied to all strands, so that current is distributed between the conductors. Simulated transport AC loss results in the straight 8/2 Roebel cable, 8/2 TPS and 4/4 ES were compared with previously measured results as well as each other. The numerical AC loss results in two coil windings 2-DPC and 8-DPC wound with the 8/2 Roebel cables were compared with the results in coil windings wound with the 8/2 TPS and 4/4 ES. No transposition was introduced at the connection between double pancakes, in order that current can be shared among the strands in the 8/2 TPS and 4/4 ES. The results indicate that AC loss in the straight 8/2 TPS and 4/4 ES is larger than that in the 8/2 Roebel cable. Current is more concentrated in the outer strands for the straight 8/2 TPS and 4/4 ES than the 8/2 Roebel cable and causes greater AC loss than the 8/2 Roebel cable. The 8-DPC coil winding wound with the 8/2 Roebel cable has the smallest loss and the coil winding wound with the 8/2 TPS has the greatest loss at two current amplitudes investigated. At 113 A, the AC loss value in the 8-DPC coil winding wound with the 8/2 TPS is 2.2 times of that wound with the 8/2 Roebel cable

Application of Flux Diverters in High Temperature Superconducting Transformer Windings for AC Loss Reduction

Flux diverters (FDs) are used in High Temperature Superconducting (HTS) transformers for AC loss reduction and flux optimization. In this paper, a 2D axial symmetric superconducting winding model is proposed and two designs of flux diverters are applied to the windings. A homogenization approach is used to analyze the windings with large turn numbers. The key parameters including the number, width, height and the spatial positions of the FDs are adjusted for AC loss and magnetic flux analysis. The means of obtaining optimum designs of the FDs is provided and can be used to develop new winding designs with FDs, which contributes to better electromagnetic performance and higher efficiency of HTS transformers

Word Detection in Individual Subjects Is Difficult to Probe With Fast Periodic Visual Stimulation

Measuring cognition in single subjects presents unique challenges. On the other hand, individually sensitive measurements offer extraordinary opportunities, from informing theoretical models to enabling truly individualised clinical assessment. Here, we test the robustness of fast, periodic, and visual stimulation (FPVS), an emerging method proposed to elicit detectable responses to written words in the electroencephalogram (EEG) of individual subjects. The method is non-invasive, passive, and requires only a few minutes of testing, making it a potentially powerful tool to test comprehension in those who do not speak or who struggle with long testing procedures. In an initial study, Lochy et al. (2015) used FPVS to detect word processing in eight out of 10 fluent French readers. Here, we attempted to replicate their study in a new sample of 10 fluent English readers. Participants viewed rapid streams of pseudo-words with words embedded at regular intervals, while we recorded their EEG. Based on Lochy et al. (2015) we expected that words would elicit a steady-state response at the word-presentation frequency (2 Hz) over parieto-occipital electrode sites. However, across 40 datasets (10 participants, two conditions, and two regions of interest–ROIs), only four datasets met the criteria for a unique response to words. This corresponds to a 10% detection rate. We conclude that FPVS should be developed further before it can serve as an individually-sensitive measure of written word processing

Relationships between Reading Ability and Child Mental Health: Moderating Effects of Self-Esteem

Objective: Children with reading difficulties are at elevated risk for externalising (e.g., conduct disorder) and internalising (e.g., anxiety and depression) mental health problems. Reading ability is also negatively associated with self-esteem, a consistent predictor of child and adolescent mental health more broadly. This study examined whether self-esteem moderated and/or mediated relationships between reading ability and mental health. Method: One hundred and seventeen children (7-12 years) completed standardised reading assessments (Castles and Coltheart Test 2; CC2) and self-report measures of mental health (Strengths and Difficulties Questionnaire; SDQ) and self-esteem (Coopersmith Self-esteem Inventory). Non-verbal intelligence (IQ) was measured using the block design and matrix reasoning subscales of the Wechsler Abbreviated Scale of Intelligence, and was controlled for in all multivariate analyses. Results: Reading ability was negatively associated with internalising symptoms. This relationship was not moderated by self-esteem. Poor readers also reported more total difficulties and externalising symptoms, but only at low levels of self-esteem. There was no evidence that self-esteem mediated relationships between reading ability and mental health. Conclusions: Poor reading was associated with internalising symptoms. Self-esteem moderated the impact of reading ability on total difficulties and externalising symptoms, with high self-esteem buffering against negative impacts of poor reading. However, the reliability of the self-esteem scale used in the study was poor and findings need replication using a reliable and valid self-esteem measure, as well as other measures of child mental health. If replicated, future research should examine whether interventions aiming to improve self-esteem can reduce the risk of externalising problems in children with reading difficulties