Biomedical subjects

Peter Stiers

Publications and source records attributed to Peter Stiers.

13 recordsLinked to original sources

PubMed2006

Long-term cognitive sequelae of antenatal maternal anxiety: involvement of the orbitofrontal cortex.

Anxiety and stress experienced by the mother during pregnancy are reported to have a negative association with the cognitive development of the child. An integration of recent evidence from cognitive reaction time tasks pointed to a deficit in endogenous response inhibition, a function ascribed to prefrontal cortex. To further delineate the cognitive sequelae associated with antenatal maternal anxiety, we reviewed recent neuro-imaging literature to create a cortical map of regions commonly and selectively activated by well-known cognitive tasks. The pragmatic value of this cortical map was tested in a follow-up sample of 49 17-year old adolescents. Adolescents of mothers with high levels of anxiety during week 12-22 of their pregnancy performed significantly lower in tasks which required integration and control of different task parameters. Working memory, inhibition of a prepotent response, and visual orienting of attention were not impaired. Based on the established cortical map, these results were related to subtle developmental aberrations in a part of, or in cortical and sub-cortical regions linked to, the orbitofrontal cortex.

Animals↗

PubMed2006

Specific memory impairment in a multiple disabled male with fragile X syndrome and temporal lobe epilepsy.

Evaluation of the cognitive repercussions of an epileptic disorder and its treatment are important issues in clinical follow-up. This especially holds true for temporal lobe epilepsy (TLE) where resective surgery can be a valid treatment option. However, in patients where TLE coexists with another neurocognitive disorder, questions can arise about the precise nature of the neuropsychological deficits. The aim of the present study was to evaluate memory impairments, found in a male aged 12 years who had the dual pathology of fragile X syndrome and refractory TLE. Memory functions of this child were compared with those of a male aged 11 years 7 months with fragile X syndrome matched for intellectual functioning as indicated by highly comparable verbal (5 y 5 mo vs 5 y 9 mo) and non-verbal (7 y 2 mo vs 6 y 1 mo) cognitive age equivalents. Performance on each neuropsychological measure was evaluated twice, separately with normative data based on chronological age and on verbal or non-verbal cognitive level. A specific, distinguishable profile of task performance could be found only when controlling for general level of cognitive functioning. This made it possible to accurately evaluate neuropsychological abilities before and 6 months after anterior temporal lobe resection even in this male with a complex neurological pathology.

Abnormalities, Multiple↗

PubMed2005

ADHD deficit as measured in adolescent boys with a continuous performance task is related to antenatal maternal anxiety.

Antenatal maternal anxiety has been shown to be related to infant temperament, childhood disorders, and impulsivity in adolescence. This study prospectively investigated whether antenatal maternal anxiety is associated with performance on a continuous performance task. Sixty-four adolescents (mean age, 15 y; 34 boys, 30 girls) were examined with a computerized continuous performance task (CPT) measuring sustained attention. Results showed that the CPT performance of boys of mothers with high levels of state anxiety during the 12th to 22nd postmenstrual week of pregnancy declined as the task progressed: their processing speed became slower and the variability in their reaction times increased. The study controlled for the possible confounding influences of postnatal maternal anxiety, the parents' educational level, and intelligence. Establishing a link between antenatal maternal anxiety and an objective measure of sustained attention/self-regulation, our results extend the growing evidence for an association between antenatal maternal anxiety and the neurobehavioral development of the offspring up into adolescence.

Adolescent↗

PubMed2005

Mapping multiple visual areas in the human brain with a short fMRI sequence.

It is a fundamental insight of neuroscience that the cerebral cortex is divided into spatially separated and functionally distinct areas. In this study, we tried to map a large number of visual areas in individual subjects passively viewing a simple stimulus sequence during functional magnetic resonance imaging (fMRI) at 1.5 T. The blocked stimulus sequence contrasted static object photographs with video takes of movement through natural indoor and outdoor scenes, alternated with a control fixation task. Two runs of the 5-min sequence sufficed to invoke 29 distinguishable activations, 16 (13 bilateral) of which were observed in all 10 participants. At the ventral side, object responsive activations were organized along the lateral occipital-temporal surface and near the collateral and occipital-temporal sulci. The latter activations, corresponding to the lateral occipital complex, showed a different activation profile from those near the collateral sulcus, most likely corresponding to the color constancy areas V4/V8-V4alpha. A potentially new fusiform object area was seen in 6 subjects, even more anterior than the parahippocampal place area. At the dorsal side, consistent activations were mainly related to motion stimuli and included the well-known areas V3a, VIPS, POIPS, hV5+, STS and the cingulate sulcus. There was consistent activation in the parietal-occipital sulcus, containing the areas V6a and V6. In addition, all subjects showed activation in the superior-anterior precuneus. Thus, the short stimulus sequence robustly invoked multiple visual areas and can be used to map the organization of the visual system in normal and brain-damaged individuals.

Adult↗

PubMed2005

Global form perception in cats early deprived of pattern vision.

Recently, we showed that binocularly deprived cats are not able to detect global motion in a random dot pattern (Burnat et al., 2002). Here, we examined, in these animals, a global form discrimination task, that is, distinction of a square from a rectangle, matched for total surface. In contrast to the previously tested motion task, binocularly-deprived cats, as compared with controls, performed only at higher thresholds. Interestingly, the increase of the stimuli's surface, or a shift from horizontal to vertical orientation of the rectangle, significantly impaired their performance. We therefore conclude that binocularly-deprived cats do not attend to the global form of the stimuli. Instead, they spontaneously choose a local cue to discriminate and are not able to modify it.

Age Factors↗

PubMed2005

Attention and information processing in survivors of childhood acute lymphoblastic leukemia treated with chemotherapy only.

BACKGROUND: Omitting radiotherapy for central nervous system (CNS) prophylaxis has improved the overall quality of life for long-term survivors of childhood acute lymphoblastic leukemia (ALL). However, recent reports suggest minor cognitive impairment in survivors who received chemotherapy only. PROCEDURE: This study focused on attentional functioning and speed of information processing in 23 children previously treated for ALL according to EORTC 58881 and EORTC 58951 protocol. Patients received intrathecal methotrexate combined with high doses intravenous methotrexate as CNS prophylaxis. Cognitive functioning was assessed with the Amsterdam Neuropsychological Tasks, a computerized attention assessment program. Variables of both speed and accuracy of the patients were compared with those obtained from 23 age- and sex-matched control children. RESULTS: Patients were equal to control children concerning baseline speed, sustained attention, response inhibition, and response organization. However, they were significantly slower than controls in three tasks: encoding, memory search letters, and focused attention 4-letters. Interactions with the difficulty of the task were found. There were no differences in number or type of errors between groups on all tasks. CONCLUSIONS: ALL survivors treated with chemotherapy have specific information processing difficulties. They process information slower than control children, especially when more information has to be processed or when attention has to be focused precisely. In spite of being slower, patients are equally accurate compared to control children.

Antineoplastic Agents↗

PubMed2005

Atypical neuropsychological profile in a boy with 22q11.2 Deletion Syndrome.

In this article the general and specific cognitive impairments of the boy R.H. with a de novo deletion 22q11.2 are described. His full-scale IQ was 73, and he obtained only slightly better verbal than non-verbal subtest scores. Neuropsychological assessment revealed specific impairments in perceptual categorization of objects presented suboptimal, matching of unfamiliar faces, and verbal learning and memory. In contrast, he performed in accordance with his intelligence level on other visual perceptual tasks, on non-verbal learning and memory tasks, and on attention tasks. Voxel-wise statistical comparison of a high-resolution T1-weighted magnetic resonance image of R.H's brain with similar images obtained from 14 normal control children revealed as major abnormalities a reduction of the right inferior parietal and superior occipital lobe, and a bilateral reduction of deep white matter behind the inferior frontal gyrus. These cognitive impairments and MRI abnormalities are not commonly described in 22q11.2 Deletion Syndrome and may indicate a larger heterogeneity in the neurocognitive phenotype than currently evidenced. At least in this boy the microdeletion seems to have interfered with the development and functioning of particular neural subsystems, while the structure and functioning of other subsystems was left intact.

Attention Deficit Disorder with Hyperactivity↗

PubMed2004

High antenatal maternal anxiety is related to impulsivity during performance on cognitive tasks in 14- and 15-year-olds.

This study prospectively investigated the influence of antenatal maternal anxiety, measured with the State Trait Anxiety Inventory at 12-22, 23-31 and 32-40 postmenstrual weeks of pregnancy, on cognitive functioning in 57 adolescents (mean age 15 years). ANCOVAs showed effects of State anxiety at 12-22 weeks, after controlling for influences of State anxiety in later pregnancy and postnatal maternal Trait anxiety. Adolescents of high anxious pregnant women reacted impulsively in the Encoding task; they responded faster but made more errors than adolescents of low anxious women. They also scored lower on two administered WISC-R subtests. In the Stop task no differences in inhibiting ongoing responses were found between adolescents of high and low anxious pregnant women. We suspect that high maternal anxiety in the first half of pregnancy may negatively affect brain development of the fetus, reflected by impulsivity and lower WISC-R scores at 14-15 years.

Adolescent↗

PubMed2004

The dissociation of perception and cognition in children with early brain damage.

Reduced non-verbal compared to verbal intelligence is used in many outcome studies of perinatal complications as an indication of visual perceptual impairment. To investigate whether this is justified, we re-examined data sets from two previous studies, both of which used the visual perceptual battery L94. The first study comprised 47 children at risk for cerebral visual impairment due to prematurity or birth asphyxia, who had been administered the McCarthy Scales of Children's abilities. The second study evaluated visual perceptual abilities in 82 children with a physical disability. These children's intellectual ability had been assessed with the Wechsler Intelligence Scale for Children-Revised and/or Wechsler Pre-school and Primary Scale of Intelligence-Revised. No significant association was found between visual perceptual impairment and (1) reduced non-verbal to verbal intelligence; (2) increased non-verbal subtest scatter; or (3) non-verbal subtest profile deviation, for any of the intelligence scales. This result suggests that non-verbal intelligence subtests assess a complex of cognitive skills that are distinct from visual perceptual abilities, and that this assessment is not hampered by deficits in perceptual abilities as manifested in these children.

Brain Injury, Chronic↗

PubMed2004

Visual perceptual impairment in children at 5 years of age with perinatal haemorrhagic or ischaemic brain damage in relation to cerebral magnetic resonance imaging.

Children with perinatally acquired parenchymal haemorrhage are thought to have better visual perceptual skills than those with leukomalacia. We examined seven prematurely born children with parenchymal haemorrhage and 14 with grades 2-4 leukomalacia, at the age of 5 years. Clinical and magnetic resonance imaging parameters were related to visual perceptual performance assessed with the L94, using performance age. Belonging to the leukomalacia group, the inability to walk, a diminished peritrigonal white matter, a high degree of gliosis and cortical damage were associated with poorer visuo-perceptual skills. Enlarged lateral ventricles, confirming the findings of Melhelm (Radiology 214 (2000) 199), were associated with both cognitive, perceptual and motor problems and probably reflect the considerable extent of the brain damage. Specific factors protecting against visual perceptual impairment were a preserved volume of the right optical radiation and of the splenium of the corpus callosum. Children with leukomalacia are at considerable risk of visual perceptual impairment. Children with right-sided parenchymal haemorrhages also appear to be at risk although they function much better due to better motor and cognitive skills.

Birth Injuries↗

PubMed2004

Optotype and grating visual acuity in patients with ocular and cerebral visual impairment.

PURPOSE: To investigate the discrepancy between grating and optotype visual acuity in children with visual impairment due to brain and/or ocular abnormalities. METHODS: Better eye acuity at 114 cm was studied in 81 patients (ages, 5-24 years) attending special schools for the visually handicapped. Fourteen patients had a brain abnormality, 48 had an ocular disorder, and 19 had both. Three acuity tasks were administered: detecting gratings in one of two positions, discriminating the orientation of single gratings, and discriminating the orientation of uncrowded Landolt-C optotypes. The three paradigms were similar in stimulus contrast, luminance, presentation mode, and psychophysical procedure. RESULTS: Overall, grating acuity was better than optotype acuity, and the disparity increased with poorer optotype acuity. The largest discrepancies occurred in patients with brain abnormality, but disparities were also large in patients with optic nerve disorder. In patients with ocular and brain abnormality, grating acuities were only mildly better and not different from patients with only ocular abnormality. Grating orientation and grating detection tasks yielded similar thresholds, except in patients with cerebral visual impairment and with optic nerve disorder, whose grating detection acuity was better than grating orientation acuity. CONCLUSIONS: Grating-to-optotype acuity superiority is typically large in visual disorders involving the brain. The closely matched test paradigms point to stimulus characteristics as the explanation. However, because the discrepancy decreased with grating orientation acuity instead of grating detection acuity, the complexity of the response required also plays a role.

Adolescent↗

PubMed2003

Optotype and grating visual acuity in preschool children.

PURPOSE: To investigate the contribution of stimulus and response differences to the different developmental courses of grating and optotype visual acuity at the preschool age range. METHODS: Binocular visual acuity at 228 cm was assessed in 205 children in 7 age groups between 2.5 and 6 years and in 12 adults. Acuities were obtained in three tasks: detection of a grating in one of two positions, discrimination of the orientation of a single grating, and discrimination of the orientation of the gap in an uncrowded Landolt-C optotype. The three paradigms were as similar as possible in stimulus contrast, luminance, presentation mode, and psychophysical procedure. RESULTS: Mean grating and optotype acuities were lower than adult acuities at all ages. Optotype acuity was overall higher and increased faster with age than grating acuities. Grating orientation acuity was slightly but not significantly lower than grating detection acuity in all but one age group. The grating detection task was successful at earlier ages (100% at 3.5 years) than both the optotype acuity task (100% at 4.5 years) and the grating orientation task (100% at 5.75 years). CONCLUSIONS: Optotype and grating acuities follow a different developmental course in children between 3 and 6 years of age, with optotype acuity growing superior to grating acuity in that age range. The similarity of grating orientation to grating detection acuities and the difference between grating and optotype acuities suggest that superior optotype acuity is due to stimulus characteristics rather than to the complexity of the response required.

Adult↗

PubMed2002

Visual-perceptual impairment in a random sample of children with cerebral palsy.

Several studies have tried to establish the prevalence of visual-perceptual impairment in children with physical disabilities, particularly in those with cerebral palsy (CP), but failed to take into account the selective impairment of non-verbal intelligence that is frequent in these children. This has resulted in the confounding of visual-perceptual and non-verbal intelligence impairment. In the present study we aimed to determine how widespread visual-perceptual impairment is in children with CP by evaluating perceptual ability together with the performance level on non-verbal intelligence subtests. All children (n=96; 44 females, 52 males) who attended an institute for children with physical disabilities were included (age ranged from 4 years 11 months to 21 years 5 months) who had a non-verbal mental age between 3 and 7 years; Total IQ was <85 in 91% of participants. They were given a grating acuity task and the visual-perceptual battery L94, comprising six visual object recognition and two visuoconstruction tasks. Relative to their performance level on non-verbal intelligence subtests, 37.5% of the children were impaired on at least one task, and 18.7% on two or more tasks. No child was impaired on the visuoconstruction tasks. Visual-perceptual impairment was highest among six children with brain malformation (67%), followed by spastic CP (40%), and brain damage acquired after the first year of life (38%). There was no difference in visual-perceptual impairment between the subtypes of spastic CP. Results are not secondary to visual acuity deficits, as only one L94 task was significantly correlated with acuity impairment. We conclude that visual-perceptual impairment is frequent in children with physical disabilities, and not restricted to children with CP of hypoxic-ischaemic origin.

Adolescent↗