Behavioural and neurophysiological correlates of dyslexia in the continuous performance task

Longitudinal Stability of Neural Correlates of Pediatric Attention Deficit Hyperactivity Disorder: A Pilot Study of Event Related Potentials and Electroencephalography

OBJECTIVE

Stability and developmental effects of electroencephalography (EEG) and event related potential (ERP) correlates of ADHD are understudied. This pilot study examined stability and developmental changes in ERP and EEG metrics of interest.

METHODS

Thirty-seven 7 to 11-year-old children with ADHD and 15 typically developing (TD) children completed EEG twice, 11 to 36 months apart. A series of mixed effects linear models were run to examine stability and developmental effects of EEG and ERP metrics.

RESULTS

Stability and developmental effects of EEG and ERP correlates of ADHD varied considerably across metrics. P3 amplitude was stable over time and showed diverging developmental trajectories across groups. Developmental differences were apparent in error related ERPs and resting aperiodic exponent. Theta-beta ratio was stable over time among all children.

CONCLUSIONS

Developmental trajectories of EEG and ERP correlates of ADHD are candidate diagnostic markers. Replication with larger samples is needed.

Establishment of an objective index for the diagnosis of attention deficit/hyperactivity disorder by the continuous performance test "MOGRAZ"

OBJECTIVE

The diagnosis of attention deficit/hyperactivity disorder (AD/HD) in Japan is mainly based on information obtained from caregivers. There is therefore a need to establish an objectivity index that can be easily used in clinical practice. The purpose of the study was to create a predictive model for the diagnosis of AD/HD using the MOGRAZ, a visual continuous performance test developed in Japan.

METHODS

We collected data from an AD/HD group and a non-AD/HD group. The AD/HD group included 75 children with predominantly inattentive type AD/HD and 48 with combined type AD/HD who were aged 6 to 12 years and diagnosed at our department. The non-AD/HD group included 153 Japanese children aged 6 to 11 years enrolled in regular classes at a public elementary school. In both groups, multiple logistic regression analysis was performed using the results of MOGRAZ, age, and sex as parameters, and algorithms for a predictive diagnostic model of AD/HD were created.

RESULTS

The area under the receiver operating characteristic curve (ROC-AUC) between the predominantly inattentive type AD/HD subgroup and non-AD/HD group was 0.884 (95% confidence interval: 0.837-0.932), and the ROC-AUC between the combined type AD/HD subgroup and non-AD/HD group was 0.914 (95% CI: 0.869-0.959).

CONCLUSION

The prediction model using the MOGRAZ score allowed us to create an objectivity index to determine the diagnosis of AD/HD that can be easily used in clinical practice. We plan additional verification of this prediction model with additional participants.

The complexity of simple counting: ERP findings reveal early perceptual and late numerical processes in different arrangements

The counting process can only be fully understood when taking into account the visual characteristics of the sets counted. Comparing behavioral data as well as event-related brain potentials (ERPs) evoked by different task-irrelevant arrangements of dots during an exact enumeration task, we aimed to investigate the effect of illusory contour detection on the counting process while other grouping cues like proximity were controlled and dot sparsity did not provide a cue to the numerosity of sets. Adult participants (N = 37) enumerated dots (8–12) in irregular and two different types of regular arrangements which differed in the shape of their illusory dot lattices. Enumeration speed was affected by both arrangement and magnitude. The type of arrangement influenced an early ERP negativity peaking at about 270 ms after stimulus onset, whereas numerosity only affected later ERP components (> 300 ms). We also observed that without perceptual cues, magnitude was constructed at a later stage of cognitive processing. We suggest that chunking is a prerequisite for more fluent counting which influences automatic processing (< 300 ms) during enumeration. We conclude that the procedure of exact enumeration depends on the interaction of several perceptual and numerical processes that are influenced by magnitude and arrangement.

Uncoupled Brain and Behavior Changes in Lexical, Phonological, and Memory Processing in Struggling Readers

Paired behavioral and ERP measures were used to track change over time in 17 third- and fourth-grade struggling readers. Word and nonword reading on standardized tests improved, but differentiation of words and letter strings, measured by N170 and N400 amplitude, did not significantly change. Sound awareness scores improved, but the ERP rhyming effect did not significantly change. Both digit span scores and latency of the P300 oddball effect decreased. Correlations between the ostensibly matched behavioral and electrophysiological measures of change were not significant, indicating that use of ERP and behavioral measures can provide nonoverlapping insight into change during reading development.

Differences in dyslexic students before and after a remediation program: A clinical neuropsychological and event related potential study

Developmental dyslexia is defined as an unexpected specific and persistent failure to acquire efficient reading skills despite conventional instruction, adequate intelligence and sociocultural opportunity. This article reports the outcomes of a study that evaluated the implementation of a 4-month intervention program. The intervention consisted of structured activities aiming at improving (a) the children's phonological awareness, (b) their visual and auditory memory, (c) their visual discrimination ability, and (d) their text comprehension. Participants were 12 children diagnosed as dyslexic matched with 12 typically achieving peers of similar age and gender. Baseline assessment consisted of a clinical neuropsychological battery of tests and Event Related Potentials (ERPs) and resulted in confirming the discrepancy between the dyslexic and the control group. Following the remediation program, the dyslexic group did not differ significantly from their control group in six out of eight neuropsychological tests. The electrophysiological results revealed that the two groups had similar P300 latencies in 12 out of the 15 electroencephalographic sites assessed. These findings suggest that children with dyslexia can improve their abilities through a remediation program which aims to strengthen their audio-visual and phonological processes along with their working memory capability.

Attention dysfunction subtypes of developmental dyslexia

Background

Previous studies indicate that many different aspects of attention are impaired in children diagnosed with developmental dyslexia (DD). The objective of the present study was to identify cognitive profiles of DD on the basis of attentional test performance.

Material/Methods

78 children with DD (30 girls, 48 boys, mean age of 12 years ±8 months) and 32 age- and sex-matched non-dyslexic children (14 girls, 18 boys) were examined using a battery of standardized tests of reading, phonological and attentional processes (alertness, covert shift of attention, divided attention, inhibition, flexibility, vigilance, and visual search). Cluster analysis was used to identify subtypes of DD.

Results

Dyslexic children showed deficits in alertness, covert shift of attention, divided attention, flexibility, and visual search. Three different subtypes of DD were identified, each characterized by poorer performance on the reading, phonological awareness, and visual search tasks. Additionally, children in cluster no. 1 displayed deficits in flexibility and divided attention. In contrast to non-dyslexic children, cluster no. 2 performed poorer in tasks involving alertness, covert shift of attention, divided attention, and vigilance. Cluster no. 3 showed impaired covert shift of attention.

Conclusions

These results indicate different patterns of attentional impairments in dyslexic children. Remediation programs should address the individual child’s deficit profile.

Performance patterns in Conners' CPT among children with attention deficit hyperactivity disorder and dyslexia

This study investigated the performance of children with attention deficit hyperactivity disorder (ADHD) and dyslexia using Conners' Continuous Performance Test (CCPT). The clinical groups were composed of 52 children with ADHD and 32 children with dyslexia. Performance in the CCPT was evaluated using ANCOVA to compare the clinical groups with the normative Brazilian sample. The ADHD group performed worse than the normative sample in almost all of the measurements, except for reaction time and response style. The dyslexia group scored higher on commissions, variability, perseverations and inconsistency in the reaction time over the six time blocks (Hit SE Block Change) than the children in the normative Brazilian sample. The ADHD and dyslexia groups differed in omission measurements, Hit RT SE, variability, perseverations, Hit RT Interstimulus Intervals (ISI) Change and Hit SE ISI Change. We thus found that the dyslexia group had specific deficit patterns, with greater response to non-target stimuli, greater perseveration and response variability, and difficulties in hit reaction time as the test progressed.

Neurophysiological and behavioural correlates of coherent motion perception in dyslexia

Coherent motion perception was tested in nine adolescents with dyslexia and 10 control participants matched for age and IQ using low contrast stimuli with three levels of coherence (10%, 25% and 40%). Event-related potentials (ERPs) and behavioural performance data were obtained. No significant between-group differences were found in performance accuracy and response latencies of correct responses, for early (P1, N1, and P2) or late (P3) ERP peaks. However, attenuated early ERPs in the 10% coherent condition correlated significantly with lower performance accuracy (r = -.66) and with the magnitude of literacy deficit (r = -.46).

Atypical EEG beta asymmetry in adults with ADHD

BACKGROUND

Abnormal brain laterality (ABL) is well established in ADHD. However, its clinical specificity and association to cognitive and clinical symptoms is not yet understood. Previous studies indicate increased right hemisphere (RH) contribution in both ADHD and reading impaired samples. The current study investigates whether this ABL characteristic occurs in adults with ADHD absent comorbid language impairment.

METHODS

EEG beta asymmetry was compared in 35 adult ADHD subjects and 104 controls during rest and active cognition. Group differences in beta asymmetry were then further evaluated for association to linguistic and attentional abilities, as well as association to beta asymmetry measures across different brain regions.

RESULTS

Adults with ADHD showed pronounced rightward beta asymmetry (p=.00001) in inferior parietal regions (P8-P7) during a continuous performance task (CPT) that could not be attributed to linguistic ability. Among ADHD subjects only, greater rightward beta asymmetry at this measure was correlated with better CPT performance. Furthermore, this measure showed a lack of normal association (i.e., observed in controls) to left-biased processing in temporal-parietal (TP8-TP7) brain regions important for higher order language functions.

CONCLUSION

Adult ADHD involves abnormally increased right-biased contribution to CPT processing that could not be attributed to poor language ability. This appears to also involve abnormal recruitment of LH linguistic processing regions and represents an alternative, albeit less effective, CPT processing strategy. These findings suggest different pathophysiologic mechanisms likely underlie RH biased processing in ADHD and reading impaired samples.

Evidence for specificity of ERP abnormalities during response inhibition in ADHD children: a comparison with reading disorder children without ADHD

Executive function and working memory deficits are not only present in ADHD, but also in reading disorder (RD). Here, high-density ERPs were recorded during the Stop Signal Task in 53 children and adolescents: An ADHD-combined type group, a group with RD, and a healthy control group. The ADHD-C group displayed unique abnormalities of the frontal N200. Both healthy controls and RD groups showed a success-related right frontal N200 modulation, which was absent in the ADHD group. Second, for Success Inhibition trials, the ADHD-C had smaller right frontal N200 waves relative to healthy controls, while the RD group did not. In contrast, NoGo-P3 abnormalities were present both in the ADHD-C and RD groups. Impaired early response inhibition mechanisms, indexed by the frontal N200, appear to be limited to ADHD-C. In contrast, deficits in later cognitive control and error monitoring mechanisms, indexed by the NoGo-P3, appear to be present in both conditions.

Executive dysfunction in poor readers born prematurely at high risk

This study examined the relation between a preterm birth and reading ability and whether children born preterm with poorer reading were more likely to show lower cognitive and executive functioning skills compared to children born at term with poor reading ability. Participants born at term (N = 97) and preterm (N = 156) were studied using the Woodcock-Johnson Test of Achievement Word Attack subtest (WJWA), Stanford-Binet Intelligence Scale, Comprehensive Evaluation of Language Fundamentals, and executive function tasks during the 3rd, 5th, and 7th grades. Children born prematurely were divided into low (N = 94) and high (N = 62) risk groups based on severity of neonatal complications. Growth in WJWA scores was used to cluster the sample into three reading ability groups. Contrary to predictions, children born preterm were not more likely to be in the poor reading group. Poorer reading ability was associated with lower language and cognitive scores. The effect of premature birth demonstrated fewer and weaker associations with such scores. A significant interaction between reading ability and birth status indicated that high risk prematurely born children with poor reading ability were more likely than the other groups to perform poorly on executive function tasks. These data suggest that better reading ability is associated with better neuropsychological function independent of prematurity.

Stimulus effects on cancellation task performance in children with and without dyslexia

Both the sensitivity and administration time of a test are important in evaluating visuospatial attention in clinical settings, especially with respect to external validity. The purpose of the present study was to propose an adaptive model that provides a reference for test modification by manipulating target-to-distractor (T/D) ratios and the number of stimuli on the computerized cancellation test system. Tasks with different T/D ratios and numbers of stimuli were presented to two groups--children with and without dyslexia (n = 41 and 65, respectively)--to determine whether their visuospatial attention performance differed on different test forms. In general, there were significant differences between the two groups in hit rates, completion times, and performance quality (PQ) scores. The PQ score of visual attention was affected by the T/D ratios rather than by the number of stimuli. The findings suggested that the T/D ratio has a strong effect on PQ scores, and that it should be taken into consideration in test and task design.