Asymmetries in Visual-Spatial Processing Following Childhood Stroke

[Formula: see text] Executive functions and psychosocial impairment in children following arterial ischemic stroke

This study examined the executive function (EF) of children with a history of arterial ischemic stroke (AIS) and preserved intellectual abilities, with reference to age at stroke onset, lesion characteristics, language, and motor functioning. In addition, the associations between EF and emotional and behavioral functioning were investigated. A battery of standardized neuropsychological tests was administered to children with previous AIS aged 7-12 in order to assess EF, including inhibition, working memory, cognitive flexibility, and attention. Parents rated questionnaires regarding real-life emotional and behavioral functioning. Finally, clinical and neuroradiological data were also gathered. Thirty patients were enrolled. Eight children fall in the lower end of the normative range or below in more than half of the EF measures, with working memory, inhibition and cognitive flexibility equally impaired, and attention relatively better preserved. Larger lesion size and language deficits were significantly associated with higher EF impairment. Emotional and behavioral functioning was lower in children with weaker EF. Children with a history of AIS, even those with preserved intellectual functioning, have a high risk of showing poor EF, mostly regardless of clinical features or functional impairment. EF difficulties are in turn associated with emotional and behavioral problems. Therefore, a standardized evaluation of EF in this population is mandatory as part of the follow-up, in order to ensure an early intervention and prevent related difficulties.

Neurocognitive Changes in Sickle Cell Disease: A Comprehensive Review

Background:

Sickle cell disease (SCD) is a type of hemoglobinopathy characterized by abnormal hemoglobin molecules, which includes numerous acute and chronic complications. Ischemic stroke, silent cerebral infarction, headache, and neurocognitive impairment are the most common neurological complications associated with SCD.

Summary:

Acute anemia because of SCD can cause cognitive impairments because of cerebral hypoxia. Cognitive abnormalities in SCD manifest in various aspects such as working memory, verbal learning, executive functions, and attention. These neurocognitive impairments have been associated with poor functional results, such as transitioning from juvenile to adult care, adherence to medications, and unemployment.

Key message:

In this review, we focus on neurocognitive aspects of SCD patients based on different imaging techniques, psychological batteries, associated neuromarkers, and interventions for managing of cognitive deficiencies..

Working Memory in Children With Neurocognitive Effects From Sickle Cell Disease: Contributions of the Central Executive and Processing Speed

Children with sickle cell disease (SCD) are at risk for working memory deficits due to multiple disease processes. We assessed working memory abilities and related functions in 32 school-age children with SCD and 85 matched comparison children using Baddeley's working memory model as a framework. Children with SCD performed worse than controls for working memory, central executive function, and processing/rehearsal speed. Central executive function was found to mediate the relationship between SCD status and working memory, but processing speed did not. Cognitive remediation strategies that focus on central executive processes may be important for remediating working memory deficits in SCD.

Determinants of cognitive outcomes of perinatal and childhood stroke: A review

Our understanding of cognitive and behavioral outcomes of perinatal and childhood stroke is rapidly evolving. A current understanding of cognitive outcomes following pediatric stroke can inform prognosis and direct interventions and our understanding of plasticity in the developing brain. However, our understanding of these outcomes has been hampered by the notable heterogeneity that exists amongst the pediatric stroke population, as the influences of various demographic, cognitive, neurological, etiological, and psychosocial variables preclude broad generalizations about outcomes in any one cognitive domain. We therefore aimed to conduct a detailed overview of the published literature regarding the effects of age at stroke, time since stroke, sex, etiology, lesion characteristics (i.e., location, laterality, volume), neurologic impairment, and seizures on cognitive outcomes following pediatric stroke. A key theme arising from this review is the importance of interactive effects among variables on cognitive outcomes following pediatric stroke. Interactions particularly of note include the following: (a) age at Stroke x Lesion Location; (b) Lesion Characteristics (i.e., volume, location) x Neurologic Impairment; (c) Lesion Volume x Time Since Stroke; (d) Sex x Lesion Laterality; and (e) Seizures x Time Since Stroke. Further, it appears that these relationships do not always apply uniformly across cognitive domains but, rather, are contingent upon the cognitive ability in question. Implications for future research directions are discussed.

Neuropsychological and neurobehavioral outcome following childhood arterial ischemic stroke: attention deficits, emotional dysregulation, and executive dysfunction

OBJECTIVES

To investigate neuropsychological and neurobehavioral outcome in children with arterial ischemic stroke (AIS).

BACKGROUND

Childhood stroke can have consequences on motor, cognitive, and behavioral development. We present a cross-sectional study of neuropsychological and neurobehavioral outcome at least one year poststroke in a uniquely homogeneous sample of children who had experienced AIS.

METHOD

Forty-nine children with AIS aged 6 to 18 years were recruited from a specialist clinic. Neuropsychological measures of intelligence, reading comprehension, attention, and executive function were administered. A triangulation of data collection included questionnaires completed by the children, their parents, and teachers, rating behavior, executive functions, and emotions.

KEY FINDINGS

Focal neuropsychological vulnerabilities in attention (response inhibition and dual attention) and executive function were found, beyond general intellectual functioning, irrespective of hemispheric side of stroke. Difficulties with emotional and behavioral regulation were also found. Consistent with an "early plasticity" hypothesis, earlier age of stroke was associated with better performance on measures of executive function.

CONCLUSIONS

A significant proportion of children poststroke are at long-term risk of difficulties with emotional regulation, executive function, and attention. Data also suggest that executive functions are represented in widespread networks in the developing brain and are vulnerable to unilateral injury.

Greater Sparing of Visual Search Abilities in Children After Congenital Rather Than Acquired Focal Brain Damage

Background. Visual search refers to the capacity of an individual to find a target among simultaneously presented distracters and is based on visual abilities such as a fast visual processing and an accurate control of ballistic eye movements (saccades) that guide the fovea to the target location. Objective. In adults, visual field defects caused by brain damage are often associated with visual search disorders; in children, little is known about the effects of early brain lesions on visual search abilities. Methods. To test the presence of visual search defects and to investigate the role of cortical plasticity after early brain lesions, 29 children with congenital or acquired cerebral lesions, with and without visual field defects, underwent a visual search test battery. Results. The children with acquired lesions and visual field defects had longer reaction times (RTs) in the contralesional visual field compared with the ipsilesional, whereas those with congenital lesions and visual field defects did not have differences in RTs between the contralateral and ipsilateral visual fields and had a visual search pattern similar to children without a visual field defect. Conclusions. These findings support the hypothesis of more effective mechanisms of functional compensation and reorganization of the visual system in children with very early brain lesions, as opposed to those with later damage.

Long-term cognitive outcomes after pediatric stroke

This study assessed neurocognitive and neurologic outcomes of children with neonatal and childhood strokes. Twenty-one children with neonatal (mean age, 6.86 years) and 10 children with childhood (mean age, 8.21 years) strokes, identified via the Estonian Pediatric Stroke Database (1995-2006), participated. A developmental neuropsychologic assessment was used for neurocognitive outcomes, and the Paediatric Stroke Outcome Measure for neurologic outcomes. Neuromotor impairment was evident in 62% of children with neonatal strokes, and in 70% of children with childhood strokes. Compared with control subjects, children with strokes exhibited worse attention, language, memory, and sensorimotor functions. The sensorimotor domain comprised the most impaired neurocognitive area, whereas executive functions remained intact in both stroke groups. A well-preserved executive function may account for the normal range of intelligence in children with strokes. More severe impairment in neurocognitive skills was evident after neonatal strokes, and the visuospatial domain was more impaired than in children from the childhood group. Prognoses were worse after left hemisphere strokes associated with epilepsy. Our results on emerging neurocognitive deficits in several areas underline the importance of neuropsychologic testing and the follow-up of children with pediatric strokes.

Plasticity of the visual system after early brain damage

The aim of this review is to discuss the existing evidence supporting different processes of visual brain plasticity after early damage, as opposed to damage that occurs during adulthood. There is initial evidence that some of the neuroplastic mechanisms adopted by the brain after early damage to the visual system are unavailable at a later stage. These are, for example, the ability to differentiate functional tissue within a larger dysplastic cortex during its formation, or to develop new thalamo-cortical connections able to bypass the lesion and reach their cortical destination in the occipital cortex. The young brain also uses the same mechanisms available at later stages of development but in a more efficient way. For example, in people with visual field defects of central origin, the anatomical expansion of the extrastriatal visual network is greater after an early lesion than after a later one, which results in more efficient mechanisms of visual exploration of the blind field. A similar mechanism is likely to support some of the differences found in people with blindsight, the phenomenon of unconscious visual perception in the blind field. In particular, compared with people with late lesions, those with early brain damage appear to have stronger subjective awareness of stimuli hitting the blind visual field, reported as a conscious feeling that something is present in the visual field. Expanding our knowledge of these mechanisms could help the development of early therapeutic interventions aimed at supporting and enhancing visual reorganization at a time of greatest potential brain plasticity.

Nichtsprachliche Lernstörung: Eine unspezifische oder richtungsweisende Klassifikation?

Die nichtsprachliche Lernstörung stellt eine Subgruppe von Lernstörungen dar, die in Kanada und den USA in der praktischen Arbeit mit Kindern einen wichtigen Platz eingenommen hat. Die nichtsprachliche Lernstörung umfasst verschiedene kognitive Defizite, die sich primär auf visuelle und taktile Schwierigkeiten beziehen, aber auch Beeinträchtigungen in der Flexibilität des Denkens und der Psychomotorik berücksichtigen. Durch die Verwendung dieser Klassifikation ist es möglich, eine Gruppe von lerngestörten Kindern zu beachten, die in den internationalen Klassifikationsrichtlinien keine Entsprechung finden. Die Entwicklung, die Ursachen und die Diagnostik dieser Störung werden vorgestellt und kritisch beleuchtet. Der Nutzen dieser Klassifikation wird hinterfragt und auf der Basis aktueller diagnostischer Anforderungen diskutiert. Vorschläge für die Weiterentwicklung und Anpassung der Klassifikation an deutsche Standards werden vorgenommen.

Is there continuity between categorical and coordinate spatial relations coding? Evidence from a grid/no-grid working memory paradigm

We ask the question whether the coding of categorical versus coordinate spatial relations depends on different neural networks showing hemispheric specialization or whether there is continuity between these two coding types. The 'continuous spatial coding' hypothesis would mean that the two coding types rely essentially on the same neural network consisting of more general-purpose processes, such as visuo-spatial attention, but with a different weighting of these general processes depending on exact task requirements. With event-related fMRI, we have studied right-handed male subjects performing a grid/no-grid visuo-spatial working memory task inducing categorical and coordinate spatial relations coding. Our data support the 'continuous spatial coding' hypothesis, indicating that, while based on the same fronto-parieto-occipital neural network than categorical spatial relations coding, the coding of coordinate spatial relations relies more heavily on attentional and executive processes, which could induce hemispheric differences similar to those described in the literature. The results also show that visuo-spatial working memory consists of a short-term posterior store with a capacity of up to three elements in the parietal and extrastriate cortices. This store depends on the presence of a visible space categorization and thus can be used for the coding of categorical spatial relations. When no visible space categorization is given or when more than three elements have to be coded, additional attentional and executive processes are recruited, mainly located in the dorso-lateral prefrontal cortex.

Hemispheric differences for global/local processing in divided attention tasks: further evidence for the integration theory

Functional hemispheric asymmetries with respect to global/local processing have been observed more reliably in divided-attention than in selective-attention tasks. This difference has been accounted for by assuming that the hemispheres operate differently in the two tasks. In our study, the alternative hypothesis was tested that the interference between the global and local levels is increased under divided attention, and that this makes it necessary to base response selection on a more elaborated mental stimulus representation in which the levels and their content are integrated. Because the hemispheres systematically differ in this integration process, the increased interference between the levels explains why the corresponding asymmetries occur more reliably under divided attention. Two experiments supporting this hypothesis are reported, one with a divided and one with a selective attention task.

Hemispheric differences for the integration of stimulus levels and their contents: evidence from bilateral presentations

Several studies have demonstrated that hemispheric differences for the processing of hierarchical letter stimuli are more likely to occur when the letters at the levels are associated with conflicting responses. Typically, a single stimulus is presented, so that the conflict occurs between the global and the local levels of the same stimulus. Our hypothesis is that in this situation, conflict resolution requires integration of the letters and their respective levels and that the hemispheres differ in this integration process. According to this integration theory, the favorable effect of response conflict on hemispheric differences should vanish if other features, such as location, can also serve for conflict resolution. This prediction was tested in the present study by simultaneously presenting an individual hierarchical stimulus to each visual field. Conflicting letters either were arranged within one stimulus or were placed in different stimuli. In the latter case, a response conflict could also be resolved by integrating letters and locations. As was expected, there were no visual field effects in these conditions. On the other hand, visual field effects showed up when the conflicting letters were located within the same stimulus. These results support the idea that the hemispheres differ in their capacity for integrating level and form.

Sickle cell disease as a neurodevelopmental disorder

Sickle cell disease (SCD) is a blood disorder; however, the central nervous system (CNS) is one of the organs frequently affected by the disease. Brain disease can begin early in life and often leads to neurocognitive dysfunction. Approximately one-fourth to one-third of children with SCD have some form of CNS effects from the disease, which typically manifest as deficits in specific cognitive domains and academic difficulties. We discuss SCD as a neurodevelopmental disorder by reviewing the mechanisms of neurological morbidity in SCD, the timing of these mechanisms, the types of cognitive and behavioral morbidity that is typical, and the interaction of social-environmental context with disease processes. The impact of the disease on families shares many features similar to other neurodevelopmental disorders; however, social-environmental factors related to low socioeconomic status, worry and concerns about social stigma, and recurrent, unpredictable medical complications can be sources of relatively higher stress in SCD. Greater public awareness of the neurocognitive effects of SCD and their impact on child outcomes is a critical step toward improved treatment, adaptation to illness, and quality of life.

Deconfounding the Effects of Congruency and Task Difficulty on Hemispheric Differences in Global/Local Processing

Abstract. Although it is often assumed that the left and right cerebral hemispheres are specialized for local and global processing, respectively, recent studies show that this difference mainly occurs if the responses to the two levels of a stimulus are conflicting. In the present study we examined whether the favorable effect of response conflicts is caused by the increased task difficulty in this situation. To this end, the response selection for nonconflicting stimuli was complicated by frequently changing the stimulus-response mappings. As a result, the reactions to nonconflicting stimuli were as slow as those to conflicting ones. Nevertheless, hemispheric differences were again restricted to the latter situation. This shows that increased task difficulty can not explain the modulating effect of response conflicts. The results support the alternative hypothesis that different representations are needed for the response selection for nonconflicting and conflicting stimuli, and that the hemispheres differ only with respect to the latter.

Schlaganfälle im Kindes- und Jugendalter

Zusammenfassung. Schlaganfälle im Kindes- und Jugendalter gehören zu den seltenen Erkrankungen des Kindesalters. Die neurologischen Beeinträchtigungen verursachen sehr unterschiedliche neuropsychologische Defizite. Art und das Ausmaß der kognitiven Beeinträchtigungen hängen wesentlich vom Alter der Kinder zum Zeitpunkt des Schlaganfalls und von der Lokalisation der Schädigung ab. Eine neuropsychologisch orientierte Diagnostik kann wertvolle Ansatzpunkte zur Therapie der kognitiven Defizite sowie der schulbezogenen Lernstörungen liefern. Dabei spielen Aufmerksamkeits- und Gedächtnisstörungen auch bei der Beurteilung der allgemeinen Intelligenz von Kindern mit einem Schlaganfall eine zentrale Rolle. Therapeutische Bemühungen erfordern aufgrund der Vielschichtigkeit von Beeinträchtigungen nach einem Schlaganfall im Kindes- und Jugendalter einen multidisziplinären Ansatz.

Decreased corpus callosum size in sickle cell disease: relationship with cerebral infarcts and cognitive functioning

We assessed midsagittal corpus callosum size in sickle cell disease (SCD) and its relationship to lesion volume, lesion location, and cognitive functioning. Twenty-eight children with SCD and 16 demographic controls completed magnetic resonance imaging (MRI) and neuropsychological testing. Corpus callosum (CC) size was smaller for children with silent infarcts (n = 8) or overt stroke (n = 8) than for those without visible infarcts (n = 12) or control participants. Lesion volume was a robust predictor of IQ and other cognitive scores; total CC size did not typically add explanatory power for these measures. The size of the rostral body of the CC, however, independently predicted measures of distractibility, speeded production, and working memory. Posterior CC size was also decreased among many of the children with SCD, even in the absence of visible infarcts in this region. Brain morphology appears to provide additional information about SCD-related effects on the brain above and beyond visible infarcts.