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L Servais

Publications and source records attributed to L Servais.

16 recordsLinked to original sources

Effect of gravity on human spontaneous 10-Hz electroencephalographic oscillations during the arrest reaction.

Electroencephalographic oscillations at 10 Hz (alpha and mu rhythms) are the most prominent rhythms observed in awake, relaxed (eye-closed) subjects. These oscillations may be considered as a marker of cortical inactivity or an index of the active inhibition of the sensory information. Different cortical sources may participate in the 10-Hz oscillation and appear to be modulated by the sensory context and functional demands. In microgravity, the marked reduction in multimodal graviceptive inputs to cortical networks participating in the representation of space could be expected to affect the 10-Hz activity. The effect of microgravity on this basic oscillation has heretofore not been studied quantitatively. Because the alpha rhythm has a functional role in the regulation of network properties of the visual areas, we hypothesised that the absence of gravity would affect its strength. Here, we report the results of an experiment conducted over the course of 3 space flights, in which we quantified the power of the 10-Hz activity in relation to the arrest reaction (i.e., in 2 distinct physiological states: eyes open and eyes closed). We observed that the power of the spontaneous 10-Hz oscillation recorded in the eyes-closed state in the parieto-occipital (alpha rhythm) and sensorimotor areas (mu rhythm) increased in the absence of gravity. The suppression coefficient during the arrest reaction and the related spectral perturbations produced by eye-opening/closure state transition also increased in on orbit. These results are discussed in terms of current theories on the source and the importance of the alpha rhythm for cognitive function.

Adult↗

Event-related potentials (ERPs) in ecstasy (MDMA) users during a visual oddball task.

Ecstasy is the common name for a drug mainly containing a substance identified as 3,4-methylenedioxymethamphetamine (MDMA). It has become popular with participants in "raves", because it enhances energy, endurance and sexual arousal, together with the widespread belief that MDMA is a safe drug [Byard, R.W., Gilbert, J., James, R., Lokan, R.J., 1998. Amphetamine derivative fatalities in South Australia. Is "ecstasy" the culprit? Am. J. Forensic Med. Pathol. 19, 261-265]. However, it is suggested that this drug causes a neurotoxicity to the serotonergic system that could lead to permanent physical and cognitive problems. In order to investigate this issue, and during an ERP recording with 32 channels, we used a visual oddball design, in which subjects (14 MDMA abusers and 14 paired normal controls) saw frequent stimuli (neutral faces) while they had to detect as quickly as possible rare stimuli with happy or fearful expression. At a behavioral level, MDMA users imply longer latencies than normal controls to detect rare stimuli. At the neurophysiological level, ERP data suggest as main result that the N200 component, which is involved in attention orienting associated to the detection of stimulus novelty (e.g. [Campanella, S., Gaspard, C., Debatisse, D., Bruyer, R., Crommelinck, M., Guerit, J.M., 2002. Discrimination of emotional facial expression in a visual oddball task: an ERP study. Biol. Psychol. 59, 171-186]), shows shorter latencies for fearful rare stimuli (as compared to happy ones), but only for normal controls. This absence of delay was interpreted as an attentional deficit due to MDMA consumption.

Adult↗

Fast cerebellar oscillation associated with ataxia in a mouse model of Angelman syndrome.

Ataxia may result from various cerebellar cortex dysfunctions. It is included in the diagnostic criteria of Angelman syndrome, a human neurogenetic condition. In order to better understand the cerebellar dysfunction in this condition, we recorded in vivo cerebellar activity in a mouse model of Angelman syndrome produced by null mutation of the maternal Ube3a gene. We found fast oscillation (approximately 160 Hz) in the cerebellar cortex sustained by abnormally increased Purkinje cell firing rate and rhythmicity. This oscillation is inhibited by sensory stimulation and gap junction or GABA(A) receptor blockers. A physiologically similar oscillation was previously found in mice lacking calcium-binding proteins that also present ataxia, but never in wild-type mice. We propose that fast oscillation in the cerebellar cortex is implicated in the cerebellar symptomatology of Angelman syndrome.

Angelman Syndrome↗

Purkinje cell rhythmicity and synchronicity during modulation of fast cerebellar oscillation.

Fast (approximately 160 Hz) cerebellar oscillation has been recently described in different models of ataxic mice, such as mice lacking calcium-binding proteins and in a mouse model of Angelman syndrome. Among them, calretinin-calbindin double knockout mice constitute the best model for evaluating fast oscillations in vivo. The cerebellum of these mice may present long-lasting episodes of very strong and stable local field potential oscillation alternating with the normal non-oscillating state. Spontaneous firing of the Purkinje cells in wild type and double knockout mice largely differs. Indeed, the Purkinje cell firing of the oscillating mutant is characterized by an increased rate and rhythmicity and by the emergence of synchronicity along the parallel fiber axis. To better understand the driving role played by these different parameters on fast cerebellar oscillation, we simultaneously recorded Purkinje cells and local field potential during the induction of general anesthesia by ketamine or pentobarbitone. Both drugs significantly increased Purkinje cell rhythmicity in the absence of oscillation, but they did not lead to Purkinje cell synchronization or to the emergence of fast oscillation. During fast oscillation episodes, ketamine abolished Purkinje cell synchronicity and inhibited fast oscillation. In contrast, pentobarbitone facilitated fast oscillation, induced and increased Purkinje cell synchronicity. We propose that fast cerebellar oscillation is due to the synchronous rhythmic firing of Purkinje cell populations and is facilitated by positive feedback whereby the oscillating field further phase-locks recruited Purkinje cells onto the same rhythmic firing pattern.

Anesthetics, Dissociative↗

Role of calcium binding proteins in the control of cerebellar granule cell neuronal excitability: experimental and modeling studies.

Calcium binding proteins, such as calretinin, are abundantly expressed in distinctive patterns in the central nervous system but their physiological function remains poorly understood. Calretinin is expressed in cerebellar granule cells which provide the major excitatory input to Purkinje cells through parallel fibers. Calretinin deficient mice exhibit dramatic alterations in motor coordination and in Purkinje cell firing recorded in vivo through unknown mechanisms. In the present paper, we review the results obtained with the patch clamp recording techniques in acute slice preparation. This data allow us to investigate the effect of a null mutation of the calretinin gene on the intrinsic electroresponsiveness of cerebellar granule cells at a mature developmental stage. Calretinin deficient granule cells exhibit faster action potentials and generate repetitive spike discharge showing an enhanced frequency increase with injected currents. These alterations disappear when 0.15 mM of the exogenous fast calcium buffer BAPTA is infused in the cytosol to restore the calcium buffering capacity. Furthermore, we propose a mathematical model demonstrating that the observed alterations of granule cell excitability can be explained by a decreased cytosolic calcium buffering capacity due to the absence of calretinin. We suggest that calcium binding proteins modulate intrinsic neuronal excitability and may therefore play a role in the information processing in the central nervous system.

Animals↗

Mono- and dual-frequency fast cerebellar oscillation in mice lacking parvalbumin and/or calbindin D-28k.

Calbindin is a fast Ca2+-binding protein expressed by Purkinje cells and involved in their firing regulation. Its deletion produced approximately 160-Hz oscillation sustained by synchronous, rhythmic Purkinje cells in the cerebellar cortex of mice. Parvalbumin is a slow-onset Ca2+-binding protein expressed in Purkinje cells and interneurons. In order to assess its function in Purkinje cell firing regulation, we studied the firing behavior of Purkinje cells in alert mice lacking parvalbumin (PV-/-), calbindin (CB-/-) or both (PV-/- CB-/-) and in wild-type controls. The absence of either protein resulted in Purkinje cell firing alterations (decreased complex spike duration and pause, increased simple spike firing rate) that were more pronounced in CB-/- than in PV-/- mice. Cumulative effects were found in complex spike alterations in PV-/- CB-/- mice. PV-/- and CB-/- mice manifested approximately 160-Hz oscillation that was sustained by Purkinje cells firing rhythmically and synchronously along the parallel fiber axis. This oscillation was dependent on GABA(A), N-methyl-D-aspartate and gap junction transmission. PV-/- CB-/- mice exhibited a dual-frequency (110 and 240 Hz) oscillation. The instantaneous spectral densities of both components were inversely correlated. Simple and complex spikes of Purkinje cells were phase-locked to one of the two oscillation frequencies. Mono- and dual-frequency oscillations presented similar pharmacological properties. These results demonstrate that the absence of the Ca2+ buffers parvalbumin and calbindin disrupts the regulation of Purkinje cell firing rate and rhythmicity in vivo and suggest that precise Ca2+ transient control is required to maintain the normal spontaneous arrhythmic and asynchronous firing pattern of the Purkinje cells.

2-Amino-5-phosphonovalerate↗

Meningitis following basal skull fracture in two in-line skaters.

INTRODUCTION: In-line skating has been reported to cause severe head injury. Basilar skull fracture (BSF) is associated with a high risk of complication. CASE REPORT: We report two children who had bacterial meningitis following seemingly trivial in-line skating injuries. In both, anterior BSF was diagnosed retrospectively following occurrence of Streptococcus pneumoniae meningitis. DISCUSSION: The clinical signs indicating BSF depend on the fracture location. Plain skull radiography and computed tomography (CT) are not sensitive enough to detect thin fractures in the anterior cranial fossa. We argue that high resolution multiple-plane CT and coronal T2-weighted magnetic resonance imaging are indicated to diagnose BSF.

Child↗

Sterilisation of intellectually disabled women.

OBJECTIVE: To point out the proportion of intellectually disabled women (IDW) who are sterilised, and the medical and social factors associated with an increased probability to be sterilised. STUDY DESIGN: A population-based study among 97% of IDW aged 18-46, attending government-accredited institutions in the region of Brussels-Capital and the province of Walloon Brabant (Belgium). RESULTS: Among the IDW included in this study, 22.2% are sterilised, which is superior to the 7% in the general Belgian population. Factors associated with an increased probability to be sterilised are: living in an institution, having a higher intellectual quotient (IQ), being enrolled in an institution where sexual intercourse is authorised and attending an institution where contraception is required. The last three factors are significant only among women living in institutions and the last two, only in women with severe disability. Among IDW using contraception, no factor was associated with a greater probability to be sterilised. CONCLUSION: The prevalence of sterilisation among IDW is three times higher than that in the Belgian population and it is mainly correlated with factors related to the institution where these women live, especially the severely disabled.

Adolescent↗

Psychosis, migration and social environment: an age--and--gender controlled study.

PURPOSE: Adverse social experiences are frequently invoked to explain the higher rate of psychosis among migrant groups. The aim of the present study was to establish the socio-environmental factors distinguishing migrant psychotic patients from autochthonous patients. SUBJECTS AND METHOD: We conducted a cross-sectional survey involving 341 migrant psychotic patients matched for age and gender with 341 autochthonous psychotic patients. RESULTS: Migrant patients lived more often with their parental family, were less often enrolled with a referral psychiatrist, presented a lower rate of employment, a lower percentage of alcohol misuse and of suicide attempts. DISCUSSION: Our findings add to the growing body of results showing that more attention needs to be focused on socio-environmental variables in psychosis research. However, several limitations have to be taken into account, particularly with regard to selection biases and age of onset of the psychotic illness. CONCLUSION: Our results are compatible with the hypothesis that unemployment is a contributing factor in the risk for psychosis among migrant groups. Migrants' families are an important keystone in the mental health care process of their sick relatives. Our service models need to be adapted with the aim to make the treatment easier for migrant patients.

Adult↗

[Chronic subdural hematoma and extramedullary erythropoiesis in an infant].

We report the case of a six-month old child with bilateral chronic subdural hematoma of unknown origin containing erythroblasts, metamyelocytes and blast-like cells. No such cells were found in venous blood. No primary neoplastic disorder was found. Throughout a 19-month follow-up period, general and neurodevelopmental examination remained normal with complete resolution of the subdural haematoma in the presence of macrocephaly. We discuss the origin and role of these cells.

Brain↗

Psychiatric disorders and social characteristics among second-generation Moroccan migrants in Belgium: an age-and gender-controlled study conducted in a psychiatric emergency department.

PURPOSE: Clinically, one of the most consistent clinical findings among migrant patients is an increase in the rate of psychosis. The aim of the present study was to confirm this finding in Belgium by comparing second-generation Moroccan migrant patients with Belgian patients, matched for the variables of age and gender. SUBJECTS AND METHOD: We conducted a cross-sectional survey on 272 patients admitted in a psychiatric emergency unit during the year 1998. We used univariate and multivariate analyses to compare the two subgroups. RESULTS: Multivariate analyses showed that migrant patients lived more often with their parental family and that they presented a higher rate of admission for psychotic disorders and a lower rate of employment. DISCUSSION: Our findings add to the growing body of results showing increased incidence of psychosis among immigrants to European countries, but several factors have to be taken into account, particularly with regard to selection biases and differences in help-seeking behaviour and in family perception of the mental illness. CONCLUSION: Our results are compatible with the hypothesis that unemployment is a contributing factor in the risk for psychosis among migrant groups. Further studies would be needed to better explain some of our results, particularly the role played by the families of migrant patients.

Adult↗

Contraception of women with intellectual disability: prevalence and determinants.

The contraception of women with intellectual disability (ID) is a major concern for caregivers. However, the prevalence of contraception and the frequency of use of different methods (e.g. sterilization) remain generally unknown. Moreover, indications specific to women with ID are controversial. The present authors conducted a population-based study among 97% of the women with ID aged between 18 and 46 years attending government-funded facilities in Brussels and the nearby province of Walloon Brabant in Belgium. Out of 397 subjects, 40.8% did not use any contraceptive method, 22.2% were sterilized, 18.4% used an oral contraceptive agent, 17.6% used depotmedroxyprogesterone acetate and 1% used an intrauterine device. These figures differ widely from those of the general Belgian population. Binary logistic regression for 'contraceptive utilization' showed the strong influence of institutional factors such as sleeping environment (i.e. institutional or parental), sexual relationship policy and contraception policy. Having or having had a boyfriend is also correlated with a stronger probability of contraceptive use. Other factors have a smaller influence (e.g. a milder level of ID). Very few factors, none of which are medical, are correlated with an increased use of a specific method. The present results are discussed in the light of the general medical application of contraception and the commonly assumed specific indications for women with ID.

Adult↗

Factors influencing the determination of arousal thresholds in infants - a review.

Objective: To review the major confounding factors that influence the determination of arousal thresholds in infants.Review of confounding factors: The determination of arousal thresholds in infants measures their arousability from sleep. The evaluation is influenced by various conditions. The infant's arousability is decreased by maternal factors, such as exposure to cigarette smoke, alcohol, illegal drugs or medications during gestation or breastfeeding. The levels of arousal thresholds also depend on the age of the infant and on experimental conditions, such as previous sleep deprivation, type of arousal challenges, time of administration of the arousal challenge, sleep stage, body position, room temperature, use of a pacifier, bed sharing, or type of feeding. In addition, spontaneous arousals can occur and modify the infant's response to external arousal challenges.Conclusions: Factors known to modify infants' arousability from sleep should be controlled during studies designed to determine arousal thresholds.

Journal Article↗

[Evaluation of typical psychopathic traits with juvenile offenders].

UNLABELLED: The concept of psychopathy has received many definitions for the first days of psychiatry. Recently, the Hare's Psychopathy Check List Revised has been created. This scale has the advantage to investigate the classically characteristic traits of the syndrome (need of stimulation, lack of culpability, superficial activity, lack of empathy, impassivity) and to point out the early development of behavior disturbances. In the American classification (DSM IV), oppositional and aggressive behavior in child and adolescent is grouped under the Conduct Disorder diagnostic criteria. This trouble appears to be a strong predictive factor of psychopathy in adult. Identifying the high risk factors of evolution to psychopathic personality would allow an earlier intervention and prevention by multisystemic interventions for example. The present study aims to evaluate in what measure characteristic traits of psychopathy in adults are present in severe juvenile offenders and to point out, in a second time, the differences between adolescents meeting the DSM IV criteria for Conduct Disorder and a control population by a dimensional personality inventory. METHOD: The sample consists in 47 severe juvenile offenders referred for at least 3 months by a Youth Court to a Public Institution for Youth Protection (Belgium, Wauthier-Braine, 1999-2001), who have given an oral contentment and completely fulfilled the Temperament and Character Inventory-TCI. We have collected data about: schooling year by year, number of fails, changes of school; antecedents of oppositional defiant disorder with provocation (ODD, DSM IV criteria); antecedent of Conduct Disorder (CD, DSM IV criteria); penal antecedents (Youth Judge, works of general interest, placements); medico-psychological antecedents (consultation to a psychologist or a psychiatrist, hospitalization, illness, surgical intervention); psychoactive drug use or abuse. We used the TCI--Temperament and Character Inventory. This is a dimensional personality inventory. Based on biological, genetic and clinical hypothesis, it describes 2 types of variables defining personality: Variables of temperament (genetically transmitted and biologically controlled), and Variables of character (learned part of the personality reflecting the degree of adaptation and maturity, varying with environment through development). We have chosen this tool because of its dimensional aspect. Adolescence being a time of psychological and personality changes, such a tool is more useful than a categorical one. We also used this tool to verify the existence of the specific triad described by Cloninger and Svrakic. According to these authors, psychopathic personality in adult is characterized by a specific triad in which novelty seeking is high while harm avoidance and reward dependence are low. These observations are highly correlated to Hare's definition of psychopathy. We give the principal scores for the 7 personality dimensions expressed in global scores (total of the items for each dimension) and pondered ones (global scores divided by the number of items of the dimension x 100). RESULTS: Statistical analysis was performed with the Stateview 5.0 t-test program for data analysis. Statistical results show the absence of a statistically significant difference between the 2 groups for TCI 1, 4.5 and 7 but a statistically significant difference for TCI 2, 3 and 6 (p <.0001). DISCUSSION: The first limitation of our study is linked to the sample composed of young adolescents placed in an Institution for Youth Protection who doesn't reflect the whole population of offenders. A second limitation is correlated to the randomization system: randomization for age but not for sex, ethnical and cultural origin and socioeconomic status. Our results with adolescent offenders don't completely meet the Cloninger's psychopathy triad in adults. Moreover, in literature data, aggressive behavior is correlated to high novelty seeking and associated with low harm avoidance, reward dependence and persistence in children, these items are predictive of antisocial behavior in teenage and young adulthood. In our sample where antisocial behaviors are severe, we should be expecting a high novelty seeking but that is not the case. Our results should be explained by the fact that adolescence in itself is a more powerful factor of high novelty seeking than psychopathic trait. Harm avoidance and reward dependence seem to be a real problem in offending population and reflect aggressive behaviors in adolescents (lack of harm perception, sensitivity and empathy). Another interesting element is the cooperation factor that is significantly lower in the study group. This seems to comfort the hypothesis of a lower social maturity in institutionalized adolescents. CONCLUSION: Regarding to a control group subjects from 15 to 25 years old, adolescent offenders observed in an Institution for Youth Protection show a significantly different profile in the TCI for Harm Avoidance, Reward Dependence and Cooperation. Regarding to adult psychopaths, adolescent offenders partially meet the classical diagnostic triad of psychopathy, what should be indicating that such adolescents already show emotional perturbations: lower harm avoidance, reward dependence and cooperation than control population. This third factor is not characteristic of psychopathy but reflects relational difficulties, which are important in adolescent offenders. So, our study point out the complex psychopathology of adolescent offenders and the coexistence in such adolescents of attachment disorder and the difficulty to treat them because of their multiple lacks (cognitive, psychopathological, familial and scholar). We think important to discuss the necessity of approaches based on the development of personal creative abilities and involving all the professionals concerned in the young's universe. Future researches should compare adolescent offenders and controls randomized for age, sex, socioeconomic, ethnical and cultural status. They also should test specifically the diagnostic triad of psychopathology developed by Cloninger, especially the novelty seeking dimension. Moreover, it would be interesting to integrate these results in a wider protocol and to compare them with clinical, forensic and neurocognitive data, individually and within the familial context.

Adolescent↗

Case report: acute pancreatitis induced by Clozapine.

Two percent of acute pancreatitis are drug induced. In the present paper, we reported the case of a 39 year-old patient with chronic-hallucinatory schizophrenia who developed symptomatic pancreatitis during the clozapine dose titration performed to reach the therapeutic range. Diagnosis of pancreatitis was suggested by clinical examination and abnormal laboratory values of pancreatic enzymes and confirmed by C-T scan and ultrasonography. The causal incrimination of clozapine in this case seems likely as all other possible causes of pancreatitis were excluded, as AP developed shortly after the introduction of the drug and as the pancreatic enzymes normalized after clozapine was stopped. No rechallenge to confirm the causal relationship was however attempted. So far, only eight cases of acute pancreatitis have been reported in association with clozapine use. Clozapine is an atypical antipsychotic drug which belongs to the chemical class of dibenzodiazepines. The mechanism by which clozapine could produce acute pancreatitis remained unclear. Nevertheless, we advocate a careful biological follow-up (measuring periodically the concentrations of amylase, lipase and triglycerides) during the treatment by clozapine.

Acute Disease↗