P. Berquin

Dysfunction of the attentional brain network in children with Developmental Coordination Disorder: a fMRI study

Children with Developmental Coordination Disorder (DCD) present impaired motor skills, frequently associated with impaired attentional and executive functions. The objective of this study was to assess the impact of DCD on effective connectivity applied to a putative model of inhibition. fMRI was performed in 9 children with DCD and 10 control children (8-13 years old) performing a go-nogo task. As previously reported, children with DCD obtained a similar score for correct inhibitions as controls, but responses were slower and more variable than in controls. Compared to controls, Structural Equation Modeling indicated that: (1) path coefficients from both middle frontal cortex (MFC) and anterior cingulate cortex (ACC) to inferior parietal cortex (IPC) increased in children with DCD particularly in the left hemisphere; (2) path coefficients between striatum and parietal cortex decreased in children with DCD in the right hemisphere. Results suggest that DCD could be characterized by abnormal brain hemispheric specialization during development. Furthermore, connectivity in the MFC-ACC-IPC network could indicate that children with DCD are less able than healthy children to easily and/or promptly switch between go and nogo motor responses. However, children with DCD seem to compensate for this poor efficiency by more actively engaging the ACC to prevent commissions allowing maintenance of a good level of inhibition.

Dynamic changes in quantitative electroencephalogram during continuous performance test in children with attention-deficit/hyperactivity disorder

To establish whether dynamic EEG changes in children with attention-deficit/hyperactivity disorder (ADHD) differ from those observed in controls, the authors investigated the effect of the continuous performance test (CPT) on delta, theta, alpha and beta frequency bands. High-resolution electroencephalography (EEG) was recorded during eyes-open resting and CPT performance in 16 right-handed children meeting the DSM-IV criteria for ADHD and 16 age-matched controls. Significant CPT vs. eyes-open differences in EEG activities was observed in children with ADHD. In particular, switching to CPT induced an alpha power increase in children with ADHD and an alpha power decrease in controls. This may reflect a primary deficit associated with cortical hypoarousal in ADHD. These EEG results agree with behavioral findings leading the authors to suggest that dynamic changes in neural network activities are impaired in children with ADHD.

Principle of structural equation modeling for exploring functional interactivity within a putative network of interconnected brain areas

Functional neuroimaging first allowed researchers to describe the functional segregation of regionally activated areas during a variety of experimental tasks. More recently, functional integration studies have described how these functionally specialized areas, interact within a highly distributed neural network. When applied to the field of neurosciences, structural equation modeling (SEM) uses theoretical and/or empirical hypotheses to estimate the effects of an experimental task within a putative network. SEM represents a linear technique for multivariate analysis of neuroimaging data and has been developed to simultaneously examine ratios of multiple causality in an experimental design; the method attempts to explain a covariance structure within an anatomical constrained model. This method, when combined with the concept of effective connectivity, can provide information on the strength and direction of the functional interactions that take place between identified brain regions of a putative network.

Differences in effective connectivity between dyslexic children and normal readers during a pseudoword reading task: an fMRI study.

PURPOSE This fMRI study investigated phonological and lexicosemantic processing in dyslexic and in chronological age- and reading level-matched children in a pseudoword reading task. MATERIALS AND METHODS The effective connectivity network was compared between the three groups using a structural model including the supramarginal cortex (BA 40; BA: Brodmann area), fusiform cortex (BA 37) and inferior frontal cortex (BA 44/45) areas of the left hemisphere. RESULTS The results revealed differences in connectivity patterns. In dyslexic patients, in contrast with chronological age- and reading level-matched groups, no causal relationship was demonstrated between BA 40 and BA 44/45. However, a significant causal relationship was demonstrated between BA 37 and BA 44/45 both in dyslexic children and in the reading level-matched group. CONCLUSIONS These findings were interpreted as evidence for a phonological deficit in developmental dyslexia.

Visual sensory processing deficit in the occipital region in children with attention-deficit/hyperactivity disorder as revealed by event-related potentials during cued continuous performance test

AIMS OF THE STUDY Recent studies described several changes of attention-related components of late frontal event-related potentials (ERPs) during Go/NoGo paradigm in children with attention-deficit/hyperactivity disorder (ADHD). We aimed to determine whether ERP components corresponding to earlier encoding of visual incoming information are also modulated by attentional disorders. METHODS We recorded high-resolution EEG in 15 children meeting DSM-IV criteria for ADHD, comprising 15 age-matched control groups during an equiprobable Go/NoGo task in a cued continuous performance test (CPT-AX) paradigm. Both P100 and N200 ERP components were measured in response to both Go and NoGo stimuli. We analyzed both components with SwLORETA in order to localize their brain sources. RESULTS A low rate of Go correct response and high rate of omission errors were observed in ADHD children. When compared to controls, these displayed delayed P100 and N200 latency, and lower P100-NoGo amplitude. In addition, the P100 latency was delayed for NoGo compared to Go condition. The source of P100 was located in occipital area. A sizable decrease in early electrical activity was found in ADHD, especially in the NoGo condition. CONCLUSION Our results suggest an early deficit in visual sensory integration within the occipital cortex in children with ADHD.

Brain functional modeling, what do we measure with fMRI data?

The description of specific circuits in networks should allow a more realistic definition of dynamic functioning of the central nervous system which underlies various brain functions. After introducing the programmed and acquired networks and recalling the concepts of functional and effective connectivity, we presented biophysical and physiological aspects of the BOLD signal. Then, we briefly presented a few data-driven and hypothesis-driven methods; in particular we described structural equation modeling (SEM), a hypothesis-driven approach used to explore circuits within networks and model spatially and anatomically interconnected regions. We compared the SEM method with an alternative hypothesis-driven method, dynamic causal modeling (DCM). Finally, we presented independent components analysis (ICA), an exploratory data-driven approach which could be used to complete the directed brain interactivity studies. ICA combined with SEM/DCM may allow extension of the statistical and explanatory power of fMRI data.

Deficit of endogenous spatial orienting of attention in children with benign epilepsy with centrotemporal spikes (BECTS)

Attention difficulties have been reported in children with benign epilepsy with centrotemporal spikes (BECTS) but have not yet been fully specified. The aim of this study was to evaluate the functions of exogenous and endogenous spatial orienting of attention and alerting in these children. Two versions of the spatial cueing paradigm and an alerting task, including trials with and without warning signal, were performed by 25 children with BECTS aged 6-12 years and 25 controls matched for age, gender and IQ. In these three tasks, patients were slower and made more omissions than controls. The alert effect amplitude was comparable in both groups at the longer SOAs (450 ms and 800 ms) while, at the shortest SOA (100 ms), it was greater in controls than in the BECTS group. In the first version of the spatial cueing task (peripheral cues and no probability information), the validity effect amplitude, measured by longer response times (RTs) in invalid trials compared to valid trials, was comparable in both groups. In the second version (central cues and a 75% probability that the target would appear at the cued location), the validity effect was larger in the BECTS group compared to controls because of a higher cost of invalid trials compared to neutral trials. These results suggest the existence of impairments in the endogenous orienting of attention in children with BECTS, in particular an attention disengagement deficit, while exogenous orienting of attention appears to be preserved.

Maturation of response time and attentional control in ADHD: evidence from an attentional capture paradigm.

Inattention and hyperactivity/impulsivity are the core symptoms of Attention Deficit/Hyperactivity Disorder (ADHD). Slowness, although less known, has been also recently reported in children with ADHD and may contribute to their learning difficulties. Slow response time and greater response time variability have been highlighted by several computerized tasks. The goal of the present work was to evaluate the age-related response time in ADHD children and in a group of matched control children during an attentional capture paradigm. The study population included 75 children with ADHD (aged between 6 and 13) and 75 age- and gender-matched typical developing children (Control group). The children with ADHD made more errors than children on the control group. The response times and the response time variability decreased with age in both groups and were significantly greater in ADHD than in controls. The distractor effect was similar in both groups. The maturation of response times and response time variability with age is quite similar in children with ADHD and typical developing children but whatever the age-class, children with ADHD were slower and exhibited greater response time variability than control children that could explain the variation during day-time of attention capacities in ADHD.

Effect of electrical activity feedback on cognition

The goal of physiological computing, i.e. brain-computer interface (BCI) is to transform bioelectrical signals from the human nervous system into computer in order to enhance and enrich the interactive experience. In this line, effect of electroencephalographic rhythm feedback (EEG biofeedback) has been investigated on different domains of cognitive functioning of Attention-deficit/hyperactivity disorder (ADHD). This approach is argued to be an effective method for treating children with ADHD. This study was performed to evaluate the effectiveness of this method. Participants were 26 children with ADHD aged between 7–12 years. Via electrical activity feedback, thirteen children were trained to enhance the power of the beta1 activity (15–18 Hz) and decrease the power of the theta activity (4–8 Hz), and 13 of which were treated with methylphenidate alone. Neuropsychological and experimental tests were administered before and after intervention. Both methods were associated with improvements on the variability and accuracy measures of computerized test. Intellectual ability increased also by both methods.

SFP P-062 – Vascularite post-infectieuse à varicelle-zona-virus (VZV) compliquée d’un AVC chez une enfant de 6 ans

Introduction La varicelle est une maladie benigne et frequente chez l’enfant. Des complications surviennent dans 3% des cas. Cas clinique Nous rapportons le cas d’une enfant de 6ans, hospitalisee pour la survenue aigue d’une hemiplegie droite. L’enfant a presente une varicelle un mois avant le debut de l’episode. L’etude du LCR a mis en evidence une meningite lymphocytaire. La presence du VZV par PCR dans le LCR a ete confirmee. L’IRM cerebrale retrouvait des lesions ischemiques dans differents territoires de l’artere sylvienne gauche. Un traitement intraveineux par aciclovir a ete instaure. Un antiagregant plaquettaire (acide acetylsalicylique) a ete debute devant la complication cerebrale vasculaire postinfectieuse. L’evolution clinique a ete rapidement favorable avec une recuperation neurologique complete. Discussion Il n’existe pas de consensus quant a l’indication d’un traitement antiviral. Un traitement antiagregant plaquettaire doit etre discute devant une complication vasculaire cerebrale. Certains auteurs evoquent l’interet de la vaccination de la population generale des le plus jeune âge dans la prevention des complications post-varicelleuses. Conclusion La vascularite cerebrale post-varicelleuse est une complication rare mais de bon pronostic neurologique.