Biomedical subjects

F Wallois

Publications and source records attributed to F Wallois.

At least 19 recordsLinked to original sources

PubMed2005

Automated neonatal seizure detection: a multistage classification system through feature selection based on relevance and redundancy analysis.

OBJECTIVE: Automatic seizure detection obtains valuable information concerning duration and timing of seizures. Commonly used methods for EEG seizure detection in adults are inadequate for the same task in neonates because they lack the specific age-dependant characteristics of normal and pathological EEG. This paper presents an automatic seizure detection system for newborn with focus on feature selection via relevance and redundancy analysis. METHODS: Two linear correlation-based feature selection methods and the ReliefF method were applied to parameterized EEG data acquired from six neonates aged between 39 and 42 weeks. To evaluate the effectiveness of these methods, features extracted from seizure and non-seizure segments were ranked by these methods. The optimized ranked feature subsets were fed into a backpropagation neural network for classifying. Its performance was used as indicator for the feature selection effectiveness. RESULTS: Results showed an average seizure detection rate of 91%, an average non-seizure detection rate of 95%, an average false rejection rate of 95% and an overall average detection rate of 93% with a false seizure detection rate of 1.17/h. CONCLUSIONS: This good performance in detecting newborn ictal activities has been achieved based on an optimized subset of 30 features determined by the ReliefF-based detector, which corresponds to a reduction of the number of features of up to 75%. SIGNIFICANCE: The presented approach takes into account specific characteristics of normal and pathological EEG. Thus, it can improve the accuracy of conventional seizure detection systems in newborn.

Algorithms↗

PubMed2004

[Indications of electroencephalogram in the newborn].

The electroencephalogram (EEG), an easy-to-use and non invasive cerebral investigation, is a useful tool for diagnosis and early prognosis in newborn babies. In newborn full term babies manifesting abnormal clinical signs, EEG can point focal lesions or specific aetiology. EEG background activity and sleep organization have a high prognostic value. Tracings recorded over long period can detect seizures, with or without clinical manifestations, and differentiate them from paroxysmal non epileptic movements. The EEG should therefore be recorded at the beginning of the first symptoms, and if possible before any seizure treatment. When used as a neonatal prognostic tool, EEG background activity is classified as normal, abnormal (type A and type B discontinuous and hyperactive rapid tracing) or highly abnormal (inactive, paroxysmal, low voltage plus theta tracing). In such cases, the initial recording must be made between 12 and 48 h after birth, and then between 4 and 8 days of life. Severe EEG abnormalities before 12 h of life have no reliable prognostic value but may help in the choice of early neuroprotective treatment of acute cerebral hypoxia-ischemia. During presumed hypoxic-ischemic encephalopathy, unusual EEG patterns may indicate another diagnosis. In premature newborn babies (29-32 w GA) with neurological abnormalities, EEG use is the same as in term newborns. Without any neurological abnormal sign, EEG requirements depend on GA and the mother's or child's risk factors. Before 28 w GA, when looking for positive rolandic sharp waves (PRSW), EEG records are to be acquired systematically at D2-D3, D7-D8, 31-32 and 36 w GA. It is well known that numerous and persistent PRSW are related to periventricular leukomalacia (PVL) and indicate a bad prognosis. In babies born after 32 GA with clinically severe symptoms, an EEG should be performed before D7. Background activity, organization and maturation of the tracing are valuable diagnosis and prognosis indicators. These recommendations are designed (1) to get a maximum of precise informations from a limited number of tracings and (2) to standardize practices and thus facilitate comparisons and multicenter studies.

Electroencephalography↗

PubMed2000

Effect of hypoxia on the activity of respiratory and non-respiratory modulated retrotrapezoid neurons of the cat.

The retrotrapezoid nucleus (RTN), a part of the rostral ventrolateral medulla, is involved in the control of breathing. A recent immunohistological study suggested a possible involvement of the RTN in hypoxic chemoreflex loop. The present electrophysiological study performed in the cat demonstrates that 23 out of 24 RTN neurons were stimulated during the biphasic respiratory response to hypoxia, which consists of a reinforcement followed by a depression of respiratory activity. This confirms the previous immunohistological study. While 15 RTN neurons might integrate either phase I (n = 7) or phase II (n = 8) O2-chemosensitive inputs, the remaining eight RTN neurons stimulated by hypoxia are susceptible to integrate both phase I and phase II O2-chemosensitive inputs. In conclusion, our results suggest that the different subsets of RTN neurons may influence respiratory output by conveying signals originating from peripheral and/or central chemoreceptors stimulated during hypoxia.

Action Potentials↗

PubMed2000

Connections between retrotrapezoid nucleus and nucleus tractus solitarii in cat.

The retrotrapezoid nucleus (RTN), a part of the rostral ventrolateral medulla, is involved in the control of breathing. The mechanisms by which the RTN modulate the activity of respiratory neurons during chemoreceptor stimulation are not fully understood. This electrophysiological study performed in the cat demonstrates that 18 out of 22 RTN neurons receive inputs from the commissural subnucleus of the solitary tract (cNTS), the peripheral chemoreceptor afferents projection site. Moreover, six RTN neurons are found to present interconnection between RTN and the ventrolateral subnucleus of the solitary tract, an area containing mainly bulbo-spinal respiratory neurons. The present data suggest that RTN play a key role by concomitantly integrating chemosensitive informations relayed by the cNTS and providing an influence on the respiratory network.

Animals↗

PubMed1997

An improved mechanical air puff stimulator that allows activation of a variety of endoepithelial receptors and is suitable for the study of reflexes in animals and humans.

Studies of endoepithelial-triggered reflexes, such as nasal respiratory reflexes, are difficult to carry out in humans without a non-traumatic and reliable stimulation device. The air puff stimulator described allows us to deliver air puffs of brief duration at various intensities, frequencies, and temperatures. The stimulation is non-traumatizing and non-nociceptive. We have successfully used it in animals as a source of specific stimuli to enable us to study central and peripheral neuronal responses evoked by activation of endonasal dynamically sensitive receptors. Immunohistochemical studies of the c-fos expression evoked during sneezing elicited by air puffs provided additional evidence for the specificity of this particular stimulation technique. We suggest that the use of such a non-traumatizing air puff stimulator could be extended to human studies. It might be particularly useful in developmental studies of endoepithelial-triggered reflexes such as those respiratory reflexes whose immaturity at birth can be life-threatening.

Air↗

PubMed1997

Role of respiratory and non-respiratory neurones in the region of the NTS in the elaboration of the sneeze reflex in cat.

Extracellular recordings were made in the dorsal respiratory group (DRG) and adjacent reticular formation following single-shock stimulation of the anterior ethmoidal nerve (AEN) and during sneeze evoked by repetitive stimulation of the AEN in nembutal-anaesthetized, curarized and ventilated cats. These neurones were characterised according to (i) their activity during the respiratory cycle (as inspiratory augmenting or decrementing (I Aug or I Dec), expiratory augmenting or decrementing (E Aug or E Dec), silent or tonic), and (ii) their axonal projection (bulbospinal or non-bulbospinal-non-vagal (BS or NBS-NV)). Following single-shock stimulation of the AEN, most of the inspiratory neurones were transiently inhibited, whereas E Aug neurones were activated and E Dec neurones were activated and then inhibited. Silent neurones responded with a multispike or a paucispike pattern. Following repetitive stimulation of the AEN and during the resulting sneeze reflex, I Aug neurones increased their activity in parallel with the phrenic activity, I Dec neurones fired at the onset and at the end of the inspiration, E Dec and some silent neurones fired either during the compressive phase or after the expulsive phase, whereas E Aug and some silent neurones fired during the expulsive phase. We conclude that sneeze involves a reconfiguration of the central respiratory drive which uses, at least partly, the respiratory network to trigger a non-ventilatory defensive motor act.

Animals↗

PubMed1997

Changes in Fos-like immunoreactivity evoked by maturation of the sneeze reflex triggered by nasal air puff stimulation in kittens.

The sneeze reflex is a valuable tool for exploring the maturation of the respiratory control in the newborn as it alters both inspiratory and expiratory activities. Air puff stimulation of the superior nasal meatus innervated by ethmoidal afferents consistently evokes sneeze in adult cats. Such stimulation evokes only a reinforcement of expiratory activities in newborn kittens. This study demonstrates that the pattern of Fos-like immunoreactivity evoked by nasal stimulation changes during functional maturation of sneeze. Nasal stimulation evoked immunoreactivity (i) in the trigeminal sensory complex, at the levels where nasal afferents project, (ii) in the reticular formation, (iii) in the solitary complex and (iv) in the parabrachial area of mature kittens. The evoked immunoreactivity was the same in newborn kittens as in mature kittens in the projection areas of the nasal primary afferents. Fos response was less than half that in mature kittens in the reticular formation and absent in the solitary complex or the parabrachial area. Sneeze can be elicited from the time when evoked immunoreactivity in the solitary complex and the parabrachial area is above control levels. These data provide evidence that the maturation of sneeze is dependent on the development of central relays allowing peripheral inputs to be integrated by neurons engaged in respiratory control.

Aging↗

PubMed1995

C-Fos-like immunoreactivity in the cat brainstem evoked by sneeze-inducing air puff stimulation of the nasal mucosa.

Sneeze is one of the most important protective reflex of the respiratory tract. It is elicited from trigeminal peripheral fields and results in major changes in the discharge patterns of the medullary respiratory-related neurons. The pattern of c-Fos-like immunoreactivity evoked by sneezing was explored as a structural approach to the networks involved in this particular model of trigemino--respiratory interactions. Sneezes were elicited in anaesthetized adult cats by driving air puffs to the superior nasal meatus through a catheter. Additional cats were used as controls for anaesthesia and for catheter insertion into the nostril. In sneezing cats, immunoreactivity was evoked in projection areas of the ethmoidal afferents which innervate the superior nasal meatus, e.g. the subnuclei caudalis, interpolaris and in the interstitial islands of the trigeminal sensory complex. Immunoreactivity was also markedly enhanced in the areas devoted to respiratory control in the medulla (solitary complex, nucleus retroambiguus) and in the pontine parabrachial area. C-Fos expression was also evoked in the lateral aspect of the parvicellular reticular formation in sneezing cats. This area might be of major importance in the adaptation of the ventilatory system to expulsive functions.

Anesthesia↗

PubMed1995

Activities of vagal receptors in the different phases of sneeze in cats.

We studied the activity of 50 slow-adapting receptors (SAR), 13 rapidly-adapting receptors (RAR) and 3 expiratory modulated receptors in the different phases of sneeze in tracheostomized and non-tracheostomized anaesthetized cats. SAR activity increased progressively during the first phase of the preparatory inspiration in parallel to integrated diaphragmatic activity. During the second phase of the preparatory inspiration, SAR increased their discharge frequency; higher threshold SAR and RAR were recruited. During the compressive phase, discharge of SAR kept stable or increased slightly in parallel to an increase in transpulmonary pressure, while expiratory modulated receptors were activated. During the expulsive phase, only RAR were activated. Increase in transpulmonary pressure at the end of the inspiration phase of sneeze shortened expiratory duration and increased the rate of rise of expiratory muscle activity. Increase in transpulmonary pressure at the end of the compressive phase further shortened expiratory duration. These results suggest: first, a facilitatory effect on the triggering of the second phase of the preparatory inspiration from SAR; second, a modulation of the early stage of expiration by SAR, RAR and expiratory modulated receptors during the compressive phase; third, a permissive effect on a rapid expulsive thrust by SAR which can be further limited by RAR; fourth, a facilitatory effect on the triggering of inspiratory activity that follows the expiratory thrust by RAR. Both SAR and RAR might participate in the occurrence of successive sneeze in an attack and in the increased frequency of sneezing. Our results suggest that complex convergent inputs from nasal and vagal receptors, which alter the respiratory rhythm and rhythmogenesis, modulate finely the sneeze reflex.

Animals↗

PubMed1994

Influence of vagal afferents in the sneeze reflex in cats.

We studied the effects of bilateral vagotomy and step pulmonary inflations (5, 10, 15 mmHg, i.e., 0.66, 1.33, 2 kKPa) on sneeze reflex in ketamine-anaesthetized cats. Bilateral vagotomy lengthens the duration of preparatory inspiration and diminishes the amplitude of expiratory activities in sneeze. In contrast, 5 mmHg pulmonary inflation facilitates the sneeze. It shortens the inspiratory preparation and increases the frequency of sneeze attacks. At 10 mmHg pulmonary inflations, inspiration is inhibited and only expiratory thrust occurs. At 15 mmHg pulmonary inflations, vagal afferent stimulations inhibit the sneeze.

Afferent Pathways↗

PubMed1994

Nasal air puff stimulations and laryngeal, thoracic and abdominal muscle activities.

In cats, we studied the activity of laryngeal, thoracic and abdominal muscles and the variations in oesophageal pressure in response to air puff stimulations of the nasal mucosa. Following single stimulations, inspiratory and laryngeal dilator muscles were transiently inhibited. During inspiratory inhibition, expiratory muscles and laryngeal constrictor were transiently activated. Repetitive air puff stimulations, which induced sneeze, evoked a similar pattern of transient activities during the inspiratory preparation of sneeze. This resulted in transient fluctuations of the oesophageal pressure, whose mean value became more negative as the preparatory inspiration enhanced. Our results suggest that the entire pool of respiratory neurons (bulbospinal, vagal and facial) works together in the sneeze reflex. Study of transient inspiratory inhibition demonstrates two periods during the preparatory inspiration phase of sneeze. In the first period transient effects are related to each shock of the stimulation. The second period is characterized by a diminution or a lack of transient effects associated with the stimulation. At the end of the expulsive phase, the diaphragm and the glottal dilator were further activated.

Abdominal Muscles↗

PubMed1994

c-fos-like immunoreactivity in the cat's neuraxis following moderate hypoxia or hypercapnia.

The overall pattern of c-fos immunoreactivity was studied in the brainstem and spinal cord of cats subjected to moderate hypoxia or hypercapnia. In control cats (normoxic, normocapnic), c-fos was expressed mainly in pontine and periaqueductal grey but not in brainstem structures engaged in respiratory control nor in the spinal cord. Both hypoxia and hypercapnia induced c-fos expression in the parabrachial area (pneumotaxic center). In the retrotrapezoid nucleus, a structure involved in respiratory rhythmogenesis and chemoreception, immunoreactivity was detected in hypoxic but not in hypercapnic cats. Neurons in the nucleus raphe pallidus preferentially expressed c-fos in response to hypercapnia. Labelled neurons were concentrated in the dorsal and gelatinosus subnuclei of the solitary tract following hypoxia and hypercapnia, respectively. Our data suggest that some neurons that express c-fos in hypoxic or hypercapnic cats may be involved in coordination of cardiovascular and respiratory function.

Animals↗

PubMed1994

Nonvagal reflex apnea in the newborn kitten and during the early postnatal period.

The aim of this work was to study the nonvagal mechanisms which might induce apneic reflexes in kittens. Experiments were performed on spontaneously breathing animals (19 kittens at different postnatal ages). Animals were anesthetized (halothane) or decerebrated by transcollicular section of the brainstem. Weakly nociceptive cutaneous stimulations and various oral stimulations were administered in all animals. In 10 kittens, one of the lingual nerves was stimulated electrically. In 3 decerebrate kittens the effects of serotonin on respiratory activity and on muscles innervated by the hypoglossal nerve were studied. All the stimulations produced apneas of variable duration, and expiratory reinforcement was associated with activation of pretracheal muscles. Similar effects were observed after applying serotonin to the floor of the 4th ventricle. Thus serotonin may be involved in the mechanisms that cause some apneas.

Anesthesia↗

PubMed1993

Postnatal development of the anterior ethmoidal nerve in cats: unmyelinated and myelinated nerve fiber analysis.

This is the first quantitative electron microscopic study of anterior ethmoidal nerve in adult and newborn cats. The adult nerve comprises about 1,000 myelinated fibers including A delta (65%) and A beta (35%) fibers and 6,000 unmyelinated fibers. At birth, only 27% of the adult myelinated fibers complement is already present. The immaturity of the nerve is discussed in relation to that of the sneeze reflex.

Aging↗

PubMed1993

Oral stimulations induce apnoea in newborn kittens.

The aim of the present work was to study oral trigeminal mechanisms which might induce apnoeic reflexes in adult cats and kittens at different postnatal ages. Various oral stimulations and electrical stimulations of the lingual nerve produced apnoeas whose duration decreased with age until three weeks of life. In addition, swallowing was only rarely observed before 5 days and then occurred with apnoea until the third week. Responses became similar to those observed in adults between weeks 3 and 4. Thus, in kittens, the nervous control which regulates coordination between breathing and swallowing appears to be immature at birth.

Aging↗

PubMed1993

The sneeze: maturation of the reflex in kittens.

This is the first study to compare the influence of nasal afferent stimulation on inspiratory and expiratory muscle activity during sneezing, in kittens and adult cats. In kittens, we demonstrate that nasal afferent stimulation does not reinforce inspiratory activity prior to the expiratory thrust as it normally does in adult cats. These stimulations evoke an active expiration similar to but weaker than the expiratory thrusts observed under the same conditions during sneezing in adult cats. Sneezing can be elicited from three weeks of life. Among the different hypotheses discussed, the most likely explanation appears to be the immaturity of medullary respiratory connections.

Aging↗

PubMed1992

Influence of trigeminal nasal afferents on bulbar respiratory neuronal activity.

This study examined the influence of nasal trigeminal afferents, the anterior ethmoidal nerve (AEN) and posterior nasal nerves (PNN) on the spike discharges of respiratory-related neurons recorded in the ventral respiratory group (VRG) (2.6-3.5 mm lateral to the midline, from 1 mm rostral to 3 mm caudal to the obex and at depth of 2-4 mm below the dorsal surface). Electrical stimulations to the AEN and PNN were administered to 10 pentobarbital anaesthetized cats and to 8 ketamine anaesthetized, vagotomized, curarized and ventilated cats. Single shock stimulations of either nerve evoked transient and total inhibition of inspiratory activities. Expiratory-related neurons of the VRG presented three patterns of activity in response to stimulation:excitation, inhibition or inhibition followed by excitation. More generally, expiratory units are activated with a short latency. In the course of repetitive stimulation of the AEN and PNN we observed a prolongation of the spontaneous inspiratory discharge which presented transient, short inhibition in response to each shock. Most expiratory units presented a short activation which was synchronous with the transient inhibition of inspiratory activities. When repetitive stimulation provoked a sneeze-like response, we observed a progressive increase in the duration of transient inspiratory inhibition first, associated with a progressive reinforcement of transient expiratory activation. Secondarily, just before the expiratory thrust, we noted a stronger inhibition of the inspiratory activity which preceded a high-frequency (400 Hz) expiratory discharge. Nasal afferents exert a forceful excitatory effect on bulbospinal (BS) and non-bulbospinal-non-vagal (NBS-NV) expiratory cells of the VRG. The effects due to vagotomy and curarization are discussed.

Action Potentials↗

PubMed1992

A comparative HRP study of the neuronal supply to the inferior and superior nasal meatus in the cat.

Neurons supplying the nasal mucosa in the cat were retrogradely labelled with horseradish peroxidase. Sensory trigeminal neurons to the inferior and superior nasal meati are somatotopically organized, according to the ophthalmic or maxillary origin of the afferents studied. Whatever their relative location, the cell bodies from nasal afferents were, on average, smaller than the overall cell population in the ganglion, in keeping with the high proportion of nasal receptors innervated by thin fibers. Postganglionic neurons from parasympathetic origin could be labelled in the sphenopalatine ganglion. These neurons probably supply mucosal secretory glands. They are in the same size range as the bulk of neurons in the same ganglia.

Animals↗