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Biomedical subjects

Chantal Kemner

Publications and source records attributed to Chantal Kemner.

15 recordsLinked to original sources
PubMed2006

ERPs and eye movements reflect atypical visual perception in pervasive developmental disorder.

Many studies of eye tracking or event-related brain potentials (ERPs) in subjects with Pervasive Developmental Disorder (PDD) have yielded inconsistent results on attentional processing. However, recent studies have indicated that there are specific abnormalities in early processing that are probably related to perception. ERP amplitudes in response to visual stimuli, measured above the occipital (modality-specific) cortex, are reported to be abnormally small in patients with PDD, and the abnormal visual processing is possibly associated with the spatial visual frequency content of stimuli. It is suggested that subjects with PDD show abnormal activation of visual pathways dedicated to the processing of high and low spatial frequencies.

Attention↗
PubMed2006

Abnormal selective attention normalizes P3 amplitudes in PDD.

This paper studied whether abnormal P3 amplitudes in PDD are a corollary of abnormalities in ERP components related to selective attention in visual and auditory tasks. Furthermore, this study sought to clarify possible age differences in such abnormalities. Children with PDD showed smaller P3 amplitudes than controls, but no abnormalities in selective attention. Adolescents with PDD showed abnormal selective attention, as reflected by larger auditory Processing Negativity (PN) and visual N2b, but no P3 abnormalities. Dipole localizations revealed that the locations of PN generators in subjects with PDD differed from controls. It was concluded that the abnormalities in selective attention in adolescents with PDD have a normalizing effect on P3, and possibly act as a compensatory process.

Adolescent↗
PubMed2006

Superior disembedding performance of high-functioning individuals with autism spectrum disorders and their parents: the need for subtle measures.

We assessed the disembedding performance on the Embedded Figures Test (EFT) of high-functioning subjects with autism or autism spectrum disorders from multi-incidence families and the performance of their parents. The individuals with autism spectrum disorders were significantly faster than matched controls in locating the shape, but their parents were not faster than a control group of parents. However, both the individuals with autism spectrum disorders and their fathers made significantly fewer incorrect attempts before finding the right shape than matched controls. These results suggest that the number of incorrect attempts is a more subtle measure than accuracy or response time for assessing superior disembedding skills and therefore may be useful in the assessment of individuals with autism spectrum disorders.

Adolescent↗
PubMed2005

Variability in spatial normalization of pediatric and adult brain images.

OBJECTIVE: Normalization of brain images is a necessity for group comparisons of source analyses based on realistic head models. In this paper we compared the outcome of a linear registration method for brain images of psychiatric and control groups of different ages in order to assess the relative adequacy of normalization in such diverse groups. METHODS: Magnetic Resonance images (MRI) of the brains of pediatric and adolescent subjects (mean ages 19 and 10.5 years) with a pervasive developmental disorder (PDD) and their healthy controls were included. A simple voxel-wise test of the group variances in image intensities was performed to evaluate regional differences in registration quality. Dipole analysis of visual P1 was performed to establish whether source locations were comparable across groups. RESULTS: Significant differences between pediatric groups were found in white matter and thalamic regions of the brain. For all other group-wise comparisons, differences were confined to skull and neck regions. Dipole locations were found to be more anteriorly located in the adolescent groups. CONCLUSIONS: The normalization procedure used in this paper is based on a brain template of normal adult brains from a restricted age group, and the results show that the use of this method in pediatric groups is less adequate. The method seems suitable for use in psychiatric groups. Also, the generators of visual P1 in PDD patients were found to be comparable to controls. SIGNIFICANCE: The results suggest that this existing normalization method can be used in diverse populations, but is less suitable for pediatric images.

Adolescent↗
PubMed2005

Increased gray-matter volume in medication-naive high-functioning children with autism spectrum disorder.

BACKGROUND: To establish whether high-functioning children with autism spectrum disorder (ASD) have enlarged brains in later childhood, and if so, whether this enlargement is confined to the gray and/or to the white matter and whether it is global or more prominent in specific brain regions. METHOD: Brain MRI scans were acquired from 21 medication-naive, high-functioning children with ASD between 7 and 15 years of age and 21 comparison subjects matched for gender, age, IQ, height, weight, handedness, and parental education, but not pubertal status. RESULTS: Patients showed a significant increase of 6% in intracranium, total brain, cerebral gray matter, cerebellum, and of more than 40% in lateral and third ventricles compared to controls. The cortical gray-matter volume was evenly affected in all lobes. After correction for brain volume, ventricular volumes remained significantly larger in patients. CONCLUSIONS: High-functioning children with ASD showed a global increase in gray-matter, but not white-matter and cerebellar volume, proportional to the increase in brain volume, and a disproportional increase in ventricular volumes, still present after correction for brain volume. Advanced pubertal development in the patients compared to the age-matched controls may have contributed to the findings reported in the present study.

Adolescent↗
PubMed2005

Brain anatomy in non-affected parents of autistic probands: a MRI study.

BACKGROUND: Autism is a neurodevelopmental disorder with an estimated genetic origin of 90%. Previous studies have reported an increase in brain volume of approximately 5% in autistic subjects, especially in children. If this increase in brain volume is genetically determined, biological parents of autistic probands might be expected to show brain enlargement, or at least intracranial enlargement, as well. Identifying structural brain abnormalities under genetic control is of particular importance as these could represent endophenotypes of autism. METHOD: Using quantitative anatomic brain magnetic resonance imaging, volumes of intracranial, total brain, frontal, parietal, temporal and occipital lobe, cerebral and cortical gray and white matter, cerebellum, lateral ventricle, and third ventricle were measured in biological, non-affected parents of autistic probands (19 couples) and in healthy, closely matched control subjects (20 couples). RESULTS: No significant differences were found between the parents of the autistic probands and healthy control couples in any of the brain volumes. Adding gender as a factor in a second analysis did not reveal a significant interaction effect of gender by group. CONCLUSIONS: The present sample of biological, non-affected parents of autistic probands did not show brain enlargements. As the intracranium is not enlarged, it is unlikely that the brain volumes of the parents of autistic probands have originally been enlarged and have been normalized. Thus, increased brain volume in autism might be caused by the interaction of paternal and maternal genes, possibly with an additional effect of environmental factors, or increased brain volumes might reflect phenotypes of autism.

Autistic Disorder↗
PubMed2005

Mutation screening and association analysis of six candidate genes for autism on chromosome 7q.

Genetic studies have provided evidence for an autism susceptibility locus (AUTS1) on chromosome 7q. Screening for mutations in six genes mapping to 7q, CUTL1, SRPK2, SYPL, LAMB1, NRCAM and PTPRZ1 in 48 unrelated individuals with autism led to the identification of several new coding variants in the genes CUTL1, LAMB1 and PTPRZ1. Analysis of genetic variants provided evidence for association with autism for one of the new missense changes identified in LAMB1; this effect was stronger in a subgroup of affected male sibling pair families, implying a possible specific sex-related effect for this variant. Association was also detected for several polymorphisms in the promoter and untranslated region of NRCAM, suggesting that alterations in expression of this gene may be linked to autism susceptibility.

Autistic Disorder↗
PubMed2004

Modulating sensorimotor gating in healthy volunteers: the effects of desipramine and haloperidol.

In schizophrenia both an involvement of a reduced prefrontal dopaminergic activity and an enhanced noradrenergic activity have been suggested. In addition, patients suffering from schizophrenia show reduced sensorimotor gating and reduced habituation. If there is a causality between these neurotransmitters and these processes, then either a reduction in dopaminergic activity or an enhanced noradrenergic activity in healthy volunteers would result in reduced sensorimotor gating and reduced habituation. In the present study, a group of 12 healthy male volunteers was tested four times in a prepulse inhibition (PPI) paradigm 2.5 h following administration of placebo/placebo, placebo/desipramine (50 mg), placebo/haloperidol (2 mg) and desipramine (50 mg)/haloperidol (2 mg). A significant reduction of percentage PPI was found in all active treatments compared with placebo/placebo, while no treatment effects on habituation were found. Furthermore, a significant increase in heart rate was found in both desipramine treatments, from 120 min following oral intake onwards. Both desipramine and haloperidol reduced PPI, which suggests that an enhanced noradrenergic activity and a reduced dopaminergic activity lead to a reduction in sensorimotor gating. Since reduced sensorimotor gating is found in schizophrenia, these results supply further evidence for a reduced prefrontal dopaminergic activity and an enhanced noradrenergic activity in schizophrenia. Furthermore, the combination of haloperidol and desipramine did not have a synergistic effect on PPI, which indicates an interaction between the compounds. The site for this interaction is most likely located in the prefrontal cortex, since evidence is accumulating that extracellular dopamine concentration is regulated by noradrenergic terminals, particularly in the frontal areas of the brain. Since no effects on habituation were found, this suggests that neither enhanced noradrenergic nor decreased dopaminergic activity is involved in this process.

Adrenergic Uptake Inhibitors↗
PubMed2004

Sources of auditory selective attention and the effects of methylphenidate in children with attention-deficit/hyperactivity disorder.

BACKGROUND: The aim of this study was to determine 1) whether abnormal auditory selective attention in children with attention-deficit/hyperactivity disorder (ADHD), as reflected in the processing negativity (PN) of the event-related potential, is related to impaired frontal functioning; and 2) how methylphenidate (MPh) affects attentional functioning in ADHD. METHODS: Sources of electrical brain activity were estimated in healthy control children, in ADHD children without medication, and in children with ADHD during a placebo-controlled medication trial involving MPh. RESULTS: The source models showed that the PN is generated in the auditory cortex. Children with ADHD showed less activity related to selective attention in this brain region. Administration of MPh resulted in more frontally located sources. CONCLUSIONS: The results showed no evidence for an important role of the frontal cortex in abnormalities in selective attention in children with ADHD. Also, the data did not indicate that MPh normalizes brain activity in these children.

Attention↗
PubMed2004

Larger brains in medication naive high-functioning subjects with pervasive developmental disorder.

BACKGROUND: Are brain volumes of individuals with Pervasive Developmental Disorder (PDD) still enlarged in adolescence and adulthood, and if so, is this enlargement confined to the gray and/or the white matter and is it global or more prominent in specific brain regions. METHODS: Brain MRI scans were made of 21 adolescents with PDD and 21 closely matched controls. RESULTS: All brain volumes, except the white matter, were significantly larger in patients. After correction for brain volume, ventricular volumes remained significantly larger in patients. CONCLUSIONS: Patients showed a proportional, global increase in gray matter and cerebellum volume, and a disproportional increase in ventricular volumes. Thus, at least in high-functioning patients with PDD, brain enlargement may still be present in adult life.

Adult↗
PubMed2004

Processing capacity in children and adolescents with pervasive developmental disorders.

This study sought to investigate whether the abnormally small P3 amplitudes observed in pervasive developmental disorder (PDD) are related to differences in processing capacity. PDD children and adolescents and their control groups participated in the study. Visual probe stimuli were presented during an auditory task with two levels of difficulty. Event-related potentials (ERP) were measured from 62 electrodes during task performance. All groups showed amplitude increases to auditory stimuli with increasing task load. Controls showed expected smaller P3 amplitudes to visual probes, whereas PDD subjects did not. The results suggest that autistic subjects show abnormal capacity allocation. Some of these abnormalities may dissolve over time, while others remain into adolescence.

Adolescent↗
PubMed2002

Inhibition in children with attention-deficit/hyperactivity disorder: a psychophysiological study of the stop task.

BACKGROUND: The purpose of the study was to investigate and identify abnormal brain activity, as revealed by event-related potentials (ERPs) concurring with deficient inhibitory control in children with attention-deficit/hyperactivity disorder (ADHD). METHODS: Performance and ERPs from 16 children with ADHD and 16 control subjects were compared in the stop-signal paradigm. RESULTS: The ADHD children showed a lower inhibition percentage and their (estimated) response time to the stop signal was disproportionally longer compared to the slowing of reaction times to primary-task stimuli. In normal control subjects, fronto-central positivity (100-400 msec) after the onset of the stop-signal was larger in case of successful inhibition, relative to failed inhibition; this was less so in ADHD children. A late positive wave (500-700 msec), maximal at Oz on failed inhibition trials, and possibly related to error-detection, was smaller in ADHD children. CONCLUSIONS: These results point to abnormalities in brain processes involved in motor inhibition and error-detection in ADHD children.

Attention Deficit Disorder with Hyperactivity↗
PubMed2002

Open-label study of olanzapine in children with pervasive developmental disorder.

The effects of olanzapine on the symptomatology of children with pervasive developmental disorder with emphasis on problems of communication and the safety of the drug were investigated in a 3-month open-label, open-dosage study. Participating in the study were 25 children age 6 to 16 years with a diagnosis of either autistic disorder or pervasive developmental disorder not otherwise specified. Psychometric measures included the Clinical Global Impression of Severity/Improvement, the Aberrant Behavior Checklist, and the TARGET (a checklist of five target symptoms). Communication skills were assessed during behavioral analysis of a playroom session. Safety measures included clinical chemistry variables, electrocardiography, the SimpsonAngus Neurological Rating Scale, the Barnes Akathisia Scale, and vital signs. Twenty-three children completed the study and showed significant improvement on three subscales of the Aberrant Behavior Checklist (Irritability, Hyperactivity, and Excessive Speech) and the TARGET. The final mean dose was 10.7 mg/day. Several aspects of communication were also improved after olanzapine treatment. However, only three children were considered responders in terms of the Clinical Global Impression of Severity/Improvement scores. The most important adverse events were weight gain, increased appetite, and loss of strength. Three children showed extrapyramidal symptoms that disappeared after the dose was lowered. Thus, while olanzapine was a relatively safe medication in children, its clinical relevance in children with pervasive developmental disorder may be limited.

Adolescent↗
PubMed2002

Normal P50 gating in children with autism.

BACKGROUND: An important characteristic of children with autism is their unusual reaction to stimuli, which may be related to problems in the filtering of sensory input. For this reason, sensory filtering was measured in children with autism using the P50 gating paradigm. METHOD: Twelve non-mentally retarded children with autism (i.e., having a DSM-IV diagnosis of either autistic disorder or pervasive developmental disorder not otherwise specified) and 11 healthy control children were tested for their ability to suppress P50, measured at the Cz electrode. RESULTS: No differences were found between the children with autism and the control children with regard to absolute P50 amplitudes and P50 suppression. CONCLUSION: The excitability of the neuronal substrate that causes P50 is normal in children with autism, as are the early, inhibitory processes related to P50 gating. These results distinguish between subjects with autism and subjects with schizophrenia, in whom sensory gating is abnormal.

Acoustic Stimulation↗