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Biomedical subjects

P Laget

Publications and source records attributed to P Laget.

At least 19 recordsLinked to original sources
PubMed1989

ERP study of the development of the holistic and analytic modes of processing between 6 and 8 years.

Event-related potentials (ERPs) were recorded (01, 02, Fcz, Cpz leads) from 32 normal children aged from 6 to 8 years during a categorisation task performed with 4 types of stimuli that allowed for a holistic and/or an analytic development to modify information processing according to the child's age. Whatever age, derivation or stimulus, the individual ERPs showed a large negative N2 wave (mean latency: 230 ms) made up of two widely overlapping components. In order to separate these components, an initial principal component analysis (PCA) was performed on the waveforms; this PCA provided a principal component that accounted for the amplitude difference between the first negative peak of the N2 wave (180 ms after stimulus onset) and the subsequent slope change. A second PCA was then carried out on the corresponding individual component scores; this second PCA provided two factors according to whether the stimuli were holistically or analytically processed. Regarding the pre- and post-vertex data (Fcz and Cpz), these two factors accounted for the same ERP effect for the 6-year-old children but opposite effects after the age of seven. We interpreted this change as reflecting the differentiation of specific - holistic and analytic - modes of processing from a non-specific mode after the establishment of the concrete operation period.

Brain↗
PubMed1986

Alterations of the functional properties of the parallel fibers in the cerebellum of the "scrapie mouse".

Alterations of the functional properties of the cerebellar parallel fibers have been investigated in scrapie mice by recording the compound action potential elicited by the superficial stimulation of the cerebellum. As soon as the 12th week following intracerebral inoculation, i.e. during the silent incubation period, there is a clear decrease of the response amplitude and of the recruiting properties. Depth profiles of the response indicate the progressive disappearance of the most superficial fibers. With respect to the remaining parallel fibers, the conduction velocity becomes progressively reduced, the duration of the refractory periods increases and the hyperexcitability and increased velocity characterizing the supernormal period are greatly reduced. Most of these electrophysiological alterations can be related to changes of the membrane properties and/or modifications of the metabolic processes ensuring the active ionic transport across the membrane.

Animals↗
PubMed1986

[Pigmentary retinopathy of neonates and infants. Their examination using electroretinography and visual evoked potentials].

A method of neurophysiological investigation (electroretinography and visual evoked potentials) is described as a non invasive exploration used in awake children. E.R.G. and V.E.P. normal patterns are described in relation to age. The data obtained in pigmentary retinopathies are referred to the physiopathology of these diseases. Usefulness of both neurophysiological tests is showed in the early diagnosis. Significative abnormalities are seen even before any detectable ophthalmoscopic symptom. In pigmentary retinopathies, V.E.P. are normal while E.R.G. is slightly then severely altered. E.R.G. and V.E.P. are also helpful in the differential diagnosis: in macular diseases, E.R.G. is usually normal while V.E.P. are altered. Repeated examinations have a prognostical value: when a disease is progressing, E.R.G. becomes more and more altered and V.E.P.'s abnormalities appear.

Electroretinography↗
PubMed1985

Drug-induced activation of the inferior olivary nucleus in young rabbits. Differential effects of harmaline and quipazine.

Ontogenic evolution of behavioural and electrophysiological responses to the serotonergic agents, quipazine and harmaline, was studied in the maturing rabbit in normal and pretreated conditions. As regards behavioural effects, tremor induced by quipazine was present from the first postnatal day and was antagonized by methysergide, but not by p-chlorophenylalanine (PCPA) or pretreatment with 5,7-dihydroxytryptamine (5,7-DHT). In contrast, tremor induced by harmaline could not be elicited before the second postnatal week and was partially antagonized by methysergide and 5,7-DHT, but not by PCPA. Electrophysiological studies of cell activity in the inferior olivary nucleus revealed a similar dependency on age since rhythmic activation of the inferior olivary nucleus could be registered from the first postnatal day with quipazine and only from the 8th postnatal day with harmaline; drug interactions with methysergide, PCPA and 5,7-DHT were the same as for the behavioural observations. It is suggested that quipazine directly activates serotonin receptors which are already present at birth, whereas harmaline requires the presence of serotonergic fibres for such activation.

5,7-Dihydroxytryptamine↗
PubMed1985

Fluorocarbons: a potential treatment of cerebral air embolism in open-heart surgery.

This study was designed to assess whether an oxygenated fluorocarbon solution could reduce ischemic brain damage related to arterial air embolism. Air embolism was produced by injecting air bubbles into the carotid artery of barbiturate-anesthetized rats breathing 100% oxygen. Results were assessed on electrocorticogram. In an additional set of experiments, mass spectrometry was used to provide continuous monitoring of intracerebral tissue oxygen (PO2) and carbon dioxide (PCO2) tensions and intermittent measurement of cerebral blood flow (CBF). Fluorocarbon or saline solution (containing the emulsifying agent of fluorocarbons) was given intravenously after the initial air embolism (0.2 ml), and injections of air (0.1 ml) were repeated thereafter every five minutes. The maximal amount of air required to achieve complete and irreversible flattening of the electrocorticogram was 1.60 +/- 0.06 ml (mean +/- standard error of the mean) in the saline-treated rats and 5.20 +/- 0.44 ml in the fluorocarbon-treated group (p less than 10(-7)). In the second experiment, air embolism caused CBF to rise in both groups, the average percent of increase being higher in treated (41.6%) than in control animals (38.3%) (p less than 0.02). However, in the control group, the increase in CBF did not prevent intracerebral tissue PO2 from decreasing by 7.4 +/- 7.0% over the same period; conversely, in the fluorocarbon group, PO2 levels fell by only 2.5 +/- 3.7% (p less than 0.001 versus controls), but this time-averaged percentage was calculated over a longer period of cumulative ischemia because of the greater number of air emboli tolerated by treated animals.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1985

[Maturation of late visual potentials linked to cognitive processes in the normal child].

In 21 normal children in age ranging from 6 to 9 years, endogenous P300 components were recorded on vertex and occipital areas. The ERPs were provoked by error detections in various tasks of visual discrimination involving cognitive abilities of the subjects. The data reveal an obvious influence of the age according to the number of the detected P300 and the correlations between presence and/or absence of the vertex and occipital responses. The limit of 7 years of age seemed important for the maturation of the P300 system.

Aging↗
PubMed1984

Locked in syndrome with a favourable outcome.

The locked in syndrome seldom occurs in children, is rarely due to trauma and only in exceptional cases has a favourable outcome. The case reported below is unusual in all these respects, and its evolution might be an example of successful axonal regeneration in the central nervous system.

Accidents, Traffic↗
PubMed1984

[Place of VEP's and ERG in neonatal encephalopathies and impaired visual maturation in the infant and young child].

Visual evoked potentials (VEPs) induced by brief flashes and electroretinograms (ERGs) were recorded in 15 infants (9 prematures and 6 babies with perinatal cerebral injuries) suffering from important disturbances in their visual behavior (abnormal fixation, cortical blindness). The parallel evolution of the visual symptoms and the electrophysiological signs were studied and a good correlation was observed between these clinical and electrical signs. The authors insist on the clinical and prognostic value of the VEP in this category of infants.

Blindness↗
PubMed1983

[Electromyographic study of 50 cases of Werdnig-Hoffmann disease].

An electromyographic study was performed in 50 cases of severe infantile spinal muscular atrophy (type I). 164 muscles and 93 nerves (ulnar and posterior tibialis) were tested. The thresholds of stimulation of the motor nerves were increased. Motor action potential was absent in 30% of the investigated nerves, motor nerve conduction velocity was slow in 44%, H reflex was absent in 86%. Proprioceptive nerve conduction velocity was slow in some cases. Using the long-time (50-100 msec) direct longitudinal technique of muscle stimulation (provoked fibrillation), denervation could be proved in 98% of cases. The authors emphasize diagnostical difficulties in the first days of life.

Electromyography↗
PubMed1983

[Technic and results of electromyographic exploration of the diaphragm in the infant and young child].

Electromyographic study of the diaphragma cannot be separated from the exploration of the nervi phrenici. The left nervus phrenicus is longer than the right. Both divide into 3 terminal branches that innervate the 3 main muscular areas. A different recording technique is used for each muscular area: thoracic surface electrodes for the cupulae, oesophageal probe electrodes for the crura diaphragmatis, and needle electrodes for the pars sternalis. Voluntary activity, recorded only during inspiration, is of limited use in pediatrics. The various parameters of the response to stimulation of the nervi phrenici, which are described here, are more interesting. In particular the latency period for each muscular area as a function of age is examined in detail to give an impression of the nerve conductivity.

Child↗
PubMed1982

Detergent effects of kinetic properties of (Na+ +K+)-ATPase from kidney membranes.

Studies on (Na+ +K+)-ATPase generally employ detergents such as SDS and deoxycholate. Under such conditions, the purified enzyme possesses high specific activity. The (Na+ +K+)-ATPase from kidney membranes was unmasked by deoxycholate and SDS as described by Jłrgensen and its kinetic properties were studied. The results suggest that these detergents induce some irreversible alterations in the kinetic properties of the native enzyme. Another detergent, saponin, unmasked the (Na+ +K+)-ATPase as effectively as did SDS, but it seems to affect the kinetic properties of the native enzyme to a lesser extent.

Animals↗
PubMed1982

[Electromyography in children with polymyositis (author's transl)].

Findings of repeat electromyography (EMG) in 15 children with polymyositis or dermatomyositis are reported. The data classically provided by EMG in these conditions is recalled. Emphasis is put on the contribution of stimulodetection to the diagnosis of primary disease of the muscle. With this procedure, EMG showed myogenic signs in all patients, at the first examination. Electrical anomalies are widespread from the start. A long-term study in 12 patients shows that electrical anomalies remain present long after clinical recovery. EMG disturbances are the last anomalies to disappear. EMG returns to normal when recovery is longstanding. EMG signs reappear if relapse occurs.

Adolescent↗