The role of visual attention in dyslexia: Behavioral and neurobiological evidence

Poor phonological processing has typically been considered the main cause of dyslexia. However, visuo‐attentional processing abnormalities have been described as well. The goal of the present study was to determine the involvement of visual attention during fluent reading in children with dyslexia and typical readers. Here, 75 children (8–12 years old; 36 typical readers, 39 children with dyslexia) completed cognitive and reading assessments. Neuroimaging data were acquired while children performed a fluent reading task with (a) a condition where the text remained on the screen (Still) versus (b) a condition in which the letters were being deleted (Deleted). Cognitive assessment data analysis revealed that visual attention, executive functions, and phonological awareness significantly contributed to reading comprehension in both groups. A seed‐to‐voxel functional connectivity analysis was performed on the fluency functional magnetic resonance imaging task. Typical readers showed greater functional connectivity between the dorsal attention network and the left angular gyrus while performing the Still and Deleted reading tasks versus children with dyslexia. Higher connectivity values were associated with higher reading comprehension. The control group showed increased functional connectivity between the ventral attention network and the fronto‐parietal network during the Deleted text condition (compared with the Still condition). Children with dyslexia did not display this pattern. The results suggest that the synchronized activity of executive, visual attention, and reading‐related networks is a pattern of functional integration which children with dyslexia fail to achieve. The present evidence points toward a critical role of visual attention in dyslexia.     

Assessing Homework Problems in Children with ADHD: Validation of a Parent-Report Measure and Evaluation of Homework Performance Patterns

The factor structure of a parent-report measure of child homework problems, the Homework Problems Checklist (HPC), was examined in a geographically and ethnically diverse sample of children with attention-deficit/hyperactivity disorder (ADHD). This measure was completed by the parents of 579 children ages 7.0–9.9 diagnosed with ADHD Combined Type as part of the multimodal treatment study of children with ADHD (MTA). Results replicated previous work showing two salient factors that measure homework completion behaviors (Factor I) and homework management behaviors (Factor II). This two-factor solution remained consistent when examined across child sex and ethnicity subgroups. Analysis of patterns revealed that homework problems are greater for children in higher grades and that children with ADHD and comorbid learning disabilities experience significantly more homework problems than children with ADHD alone. This study also replicated previous work showing that homework problems and ADHD inattentive symptoms are highly correlated whereas correlations between homework problems and hyperactivity and impulsivity are low to moderate. Implications of the findings for the assessment of homework problems in children with ADHD and for intervention are discussed.     

Homologous versus heterologous immune responses to Norwalk-like viruses among crew members after acute gastroenteritis outbreaks on 2 US Navy vessels

Host immune responses to human caliciviruses are difficult to study because of the lack of a clear definition of antigenic or serological types. This report describes antibody responses to several Norwalk-like viruses in large outbreaks of acute gastroenteritis on 2 US Navy ships. Enzyme immunoassays (EIAs) were used to measure antibody responses. To understand the antibody response to a homologous strain causing the outbreaks, the viral capsid gene of one isolate (C59) was expressed in baculovirus and included in the EIAs. Significantly greater seroresponses were detected in patients against the homologous strain than against the heterologous strains. Strains within genogroups reacted more strongly than did strains between genogroups. Significantly higher antibody titers against the outbreak strain were detected in acute serum samples from control subjects than in those from case patients. These results indicate that recombinant EIAs are useful for outbreak investigation and that the homologous antibody might be protective against reinfection.     

Evaluation of antiretroviral treatment in two private medical centers in Addis, Ethiopia

Ethiopia is one of the countries affected severely by the HIV/AIDS epidemic in sub-Saharan Africa. The disease is gradually fatal without antiretroviral therapy (ARV). The experience with antiretroviral therapy is limited in this country. This study is the first of its kind that has evaluated the status and implication of the clinical use of ARV drugs in Ethiopia. The guidelines for the initiation of treatment, the strengths and weaknesses of such treatment and the implications of similar intervention in a wider scale were assessed. Clinical records of 33 patients under follow-up and treatment with ARV in Hayat Hospital and Bethezatha Medical Center were identified. Data were collected from the medical records using a tool designed for the purpose. All 33 patients were receiving ARV for a mean duration of about 4 months. Twenty- three (69.7%) were males and 10 (30.3%) were females and the mean age was 38 years. Fifteen (45.5%) were married, fourteen (40.7%) were single, one (3%) divorced and there was no record for three (9.1%). Fifteen (45.5%) were businessmen, seven (21.2%) were private employees, four (12.1%) civil servants and in the remaining seven (21.2%) their occupation was not recorded. The decision to initiate ARV therapy was entirely based on the presence of symptomatic HIV disease. CD4+ lymphocyte count was done in 24 (72.7%) and basic hematological tests were done for all. However, biochemical investigations were incomplete in all of them. Triple therapy was started for all patients and the cost of the drugs was covered by their family in eleven (33.3%), by the patients in twenty-two (66.7%). Side effects of the drugs were noted in ten (30.3%) that resulted in change of the regimen in two and drug interruption in one. Response to treatment was entirely based on clinical parameters only. Twenty-three patients (69.7%) were noted to improve while nine (27.3%) remained the same and death occurred in one (3%). Standard triple therapy was used in all patients in this study and symptomatic HIV disease was the reason for the initiation of treatment. The improvement observed was not substantiated by immunological or virological parameters. Thus, the impacts of ARVs cannot be measured and the response documented in this study can be due to the effective treatment of opportunistic infections. Hence a standard protocol should be developed based on the minimum set-up required for the initiation of ARV therapy.     

Effects of Stimulant Medication,Incentives, and Event Rate on Reaction Time Variability in Children With ADHD

This study examined the effects of methylphenidate (MPH) on reaction time (RT) variability in children with attention deficit hyperactivity disorder (ADHD). Using a broad battery of computerized tasks, and both conventional and ex-Gaussian indicators of RT variability, in addition to within-task manipulations of incentive and event rate (ER), this study comprehensively examined the breadth, specificity, and possible moderators of effects of MPH on RT variability. A total of 93 children with ADHD completed a 4-week within-subject, randomized, double-blind, placebo-controlled crossover trial of MPH to identify an optimal dosage. Children were then randomly assigned to receive either their optimal MPH dose or placebo after which they completed five neuropsychological tasks, each allowing trial-by-trial assessment of RTs. Stimulant effects on RT variability were observed on both measures of the total RT distribution (ie, coefficient of variation) as well as on an ex-Gaussian measure examining the exponential portion of the RT distribution (ie, τ). There was minimal, if any, effect of MPH on performance accuracy or RT speed. Within-task incentive and ER manipulations did not appreciably affect stimulant effects across the tasks. The pattern of significant and pervasive effects of MPH on RT variability, and few effects of MPH on accuracy and RT speed suggest that MPH primarily affects RT variability. Given the magnitude and breadth of effects of MPH on RT variability as well as the apparent specificity of these effects of MPH on RT variability indicators, future research should focus on neurophysiological correlates of effects of MPH on RT variability in an effort to better define MPH pharmacodynamics.     

Functional magnetic resonance imaging assessment of cognitive function in childhood-onset systemic lupus erythematosus: a pilot study

OBJECTIVE: To investigate changes in brain activation patterns detected by functional magnetic resonance imaging (FMRI), and the relationship between FMRI activation patterns and results of formal neuropsychological testing, in patients with childhood-onset systemic lupus erythematosus (SLE). METHODS: Ten patients with childhood-onset SLE underwent formal neuropsychological testing and FMRI using 3 paradigms: a continuous performance task (CPT) to evaluate attention, an N-Back task to assess working memory, and verb generation to evaluate language processing. Composite Z maps were generated to summarize the brain activation patterns for each FMRI paradigm in patients with childhood-onset SLE and to compare these patterns with those observed in healthy controls. Between-group comparison Z maps showing differences in activation between childhood-onset SLE patients and controls were generated, using a significance level of P < 0.05 in a general linear model. RESULTS: Compared with the control group, the childhood-onset SLE group showed statistically significant increased activation of brain areas involved in the CPT, N-Back, and verb generation tasks. In contrast, in the absence of active stimulus, e.g., during times of the paradigm control tasks, childhood-onset SLE patients consistently undersuppressed activity in the expected brain areas. Activation in selected cortical areas was found to correlate negatively with results of a subset of individual neuropsychological test scores. CONCLUSION: FMRI abnormalities are present in childhood-onset SLE, manifesting as an imbalance between active and inhibitory responses to an array of stimuli. Differences in brain activation patterns compared with those observed in controls suggest that childhood-onset SLE may be associated with abnormalities in white matter connectivity resulting in neuronal network dysfunction, rather than injury of specific gray matter areas.     

Reliability of fMRI for studies of language in post-stroke aphasia subjects

Quantifying change in brain activation patterns associated with post-stroke recovery and reorganization of language function over time requires accurate understanding of inter-scan and inter-subject variability. Here we report inter-scan variability measures for fMRI activation patterns associated with verb generation (VG) and semantic decision/tone decision (SDTD) tasks in 4 healthy controls and 4 aphasic left middle cerebral artery (LMCA) stroke subjects. A series of 10 fMRI scans was completed on a 4T Varian scanner for each task for each subject, except for one stroke subject who completed 5 and 6 scans for SDTD and VG, thus yielding 35 and 36 total stroke subject scans for SDTD and VG, respectively. Group composite and intraclass correlation coefficient (ICC) maps were computed across all subjects and trials for each task. The patterns of reliable activation for the VG and SDTD tasks correspond well to those regions typically activated by these tasks in healthy and aphasic subjects. ICCs for activation were consistently high (R(0.05) approximately 0.8) for individual tasks among both control and aphasic subjects. These voxel-wise measures of reliability highlight regions of low inter-scan variability within language circuitry for control and post-recovery stroke subjects. ICCs computed from the combination of the SDTD/VG data were markedly reduced for both control and aphasic subjects as compared with the ICCs for the individual tasks. These quantitative measures of inter-scan variability support the proposed use of these fMRI paradigms for longitudinal mapping of neural reorganization of language processing following left hemispheric insult.