Search PubMed⌕ Search

Biomedical subjects

B Renault

Publications and source records attributed to B Renault.

At least 73 records · Page 4Linked to original sources
PubMed1992

An event-related potential study of controlled and automatic processes in 6-8-year-old boys with attention deficit hyperactivity disorder.

Event-related potentials (ERPs) were recorded from 2 groups (attention deficit hyperactivity disorder (ADHD) and normal control) of 12 boys aged from 6 to 8 years. Subjects were submitted to 2 different types of categorization tasks (with rare targets and frequent standards) implying either the use of a verbal class or that of an ordered series. Each type of task was performed twice, the first with reading and the second without. Amplitudes and latencies of a fronto-central N150-P250 complex, a parieto-occipital N250-P350 complex and a parieto-occipital P500 were measured. Regardless of the task, hyperactive children showed larger fronto-central P250, larger parieto-occipital N250 and smaller parieto-occipital P350s and P500s; moreover, the latencies of their parieto-occipital P350s were shortened. When the categorization depended on the use of a verbal class, ERP reading effects were significantly smaller in hyperactives than in normal controls for the parieto-occipital waves only. Alternatively, the target effects were significantly larger in hyperactive children but for the fronto-central P250 only. These results suggest that in ADHD automatic processes were enhanced when higher-order controlled processes were inadequate.

Aging↗
PubMed1992

Effect of target position on the sequential organization of processing stages.

In order to study the organization of processing stages taking place in a choice reaction time (RT) situation, the three following experimental variables were manipulated: (1) S-R compatibility; (2) movement direction; and (3) time uncertainty, these variables being known to influence distinct information processing stages. Both behavioural (RT and movement time, MT) and electrophysiological (N200 and P300 latencies) indices of processing time were analysed. All three experimental variables showed significant, additive effects on RT. Only the preparatory period had a significant effect on N200 and on P300 latencies. These results support the construction of a serial model. Furthermore, the analysis of the time intervals between electrophysiological and behavioural indices allows one to infer the relative order of the different stages in this model, as follows: motor pre-initiation, motor pre-programming, response selection and programming, and motor initiation.

Adult↗
PubMed1991

Event-related potential assessment of attention and the orienting reaction in boxers before and after a fight.

Boxers' attention and orienting mechanisms were investigated using event-related brain potential recordings, before and after a fight. This study did not reveal any abnormalities of attention or detection processes. However, a slight deficit in the orienting reaction towards stimuli delivered in the right ear, related to a greater number of blows delivered on the left side of the head, was observed.

Adult↗
PubMed1991

[Pulmonary siderosis and long-term respiratory risks of arc welders].

Pulmonary siderosis and bronchial cancer are respiratory risks in the long term in arc welders. We report a case of siderosis discovered from radiological abnormalities in a patient of 56 who had been an arc welder for 30 years. An analysis of the broncho-alveolar lavage liquid and transbronchial biopsy confirmed an iron overload and revealed patchy interstitial fibrosis. The toxic risks in arc welders arise from the gaseous fumes produced and inhaled particles at the alveolar level. The pulmonary siderosis is currently considered as a simple pneumoconiosis with a good prognosis. Some recent studies suggest the possibility of a more serious outcome with fibrosis even in the absence of any associated silicosis. The risks of bronchial cancer seem to be principally linked to exposure to chrome. A better understanding of these risks could be furnished by data from epidemiological studies which are still lacking.

Bronchoalveolar Lavage Fluid↗
PubMed1990

[Evoked potentials and the mode of cognitive development in boys 6 to 8 years of age presenting hyperactivity with attention deficit].

Event-related potentials were recorded in 2 groups (attention deficit hyperactivity disorder--ADHD--and normal controls) of 12 male children aged between 6-8 years during 4 categorization tasks. Each task was performed with a different type of visual stimulus; pictures, words, geometrical figures or digits. The amplitudes and latencies of a fronto-central P250 and a parieto-occipital P350 were examined. The overall amplitude of the fronto-central P250 was larger in the ADHD group. However, the overall latency of the parieto-occipital P350 decreased with age; coincidentally, in the control group, the P350 latency measured in the left hemisphere became shorter with age for the words than for the pictures. This was not the case in the ADHD group. These results are discussed in relation to the level of the orienting reaction and the modes (general or differentiated) of cognitive development.

Attention Deficit Disorder with Hyperactivity↗
PubMed1990

High-dose methylprednisolone and 'ex vivo' release of eicosanoids after experimental subarachnoid haemorrhage.

In the present study we have investigated the effects of high-dose methylprednisolone (MP) treatment on the 'ex vivo' release of four major eicosanoids in an experimental model of subarachnoid haemorrhage (SAH) with the aim of verifying: (a) the efficacy in reducing arachidonic acid metabolism enhancement; (b) whether high-dose methylprednisolone is effective on both the cyclooxygenase and lipoxygenase pathways; and (c) discussing the possible role of high-dose MP treatment in brain protection after SAH. Levels of prostaglandin D2 and E2, prostacyclin and also leukotriene C4 were determined by the radioimmunoassay technique after 1 h incubation of cerebral cortex samples of rats which had been subjected to experimental SAH procedure (injection of 0.3 ml of autologous arterial blood). The release of prostaglandin D2 at 48 h after SAH is significantly higher when compared to that of sham-operated animals (P less than 0.01); prostaglandin E2 release is significantly enhanced at 6 h after the SAH procedure (P less than 0.01); release of the lipoxygenase metabolite is significantly enhanced at 1, 6 and 48 h after SAH induction; MP significantly decreases the release of all eicosanoids, and values in treated animals do not differ from those of sham-operated animals. The results of the present study suggest that the global inhibitory effect of high-dose MP treatment on the 'ex vivo' release of eicosanoids after experimental SAH could be considered to be one of the neurochemical correlates for the reduced incidence and severity of arterial inflammatory response, which results in chronic vasospasm and supports the clinical evidence of MP efficacy in preventing or reducing the incidence of arterial vasospasm after aneurysmal rupture.

6-Ketoprostaglandin F1 alpha↗
PubMed1989

Brain potentials reveal covert facial recognition in prosopagnosia.

Brain potentials were recorded in a prosopagnosic patient, in response to familiar and unfamiliar faces he was asked to recognize. The amplitude of the P300 component was found to be an inverse function of probability for each category of faces despite the patient's inability to consciously recognize the familiarity of these faces. In addition, P300 latency varied from 700 to 800 msec according to the familiarity of the faces, and P300 scalp location was different as a function of faces probability and overt recognition. The results imply that covert facial recognition may be evidenced in using event-related potentials of the brain. They also demonstrate that automatic and covert processing of face familiarity are preserved, but prolonged in this patient.

Agnosia↗
PubMed1989

[Cerebral evoked potentials and conscious and unconscious recognition of faces: application to the study of prosopagnosia].

Twelve normal subjects and a prosopagnosic patient were tested in a classification task of a random display of well-known among unknown faces. Each face was presented several times. Event-related potentials (ERP) and reaction time (RT) were studied as a function of face repetition and familiarity. For normal subjects, the greater the repetition level, the more positive ERPs were on both hemispheres: between 250 and 600 msec. Moreover, the familiarity of faces modified ERPs between 350 and 600 msec. In contrast for the patient, the greater the repetition, the more negative the ERPs were. This "negative effect" was maximum on right parieto-temporal leads and was longer for unrecognized well-known than for unknown faces. These results support a differential processing of faces as a function of their memory representations for both normal subjects and patients. They further demonstrate the existence of covert face recognition processes in prosopagnosia.

Adult↗
PubMed1988

Latencies of event related potentials as a tool for studying motor processing organization.

The aim of this experiment was to better define the relative organization of motor processing using both behavioral measures and ERPs. Using the additive factors method, three motor variables; (1) stimulus-response (S-R) compatibility, (2) movement extent, and (3) time uncertainty, were all manipulated in a visuo-bimanual, four-choice, pointing task. As expected, all three variables significantly lengthened RT without interaction. All three motor variables also affected ERP latencies. Both P300 and N200 latencies were lengthened by greater movement extent. Moreover, N200 and P300 latencies were differentially affected by S-R compatibility and time uncertainty. Finally, both RT-minus-N200 and RT-minus-P300 were significantly lengthened by S-R incompatibility and greater time uncertainty whereas movement extent had no effect. In sum, ERP results did not support the assumptions of the classical serial model but rather of a contingent-parallel model. Furthermore, the ERP data can be used to infer the relative order of the different stages in this model.

Adult↗
PubMed1982

Onset and offset of brain events as indices of mental chronometry.

Analysis of single-trial electroencephalogram waveforms in a reaction time task demonstrated that the onset and offset values of event-related potentials can be used as indices of the duration of information processing. Two negative waves have been identified which peak at different times in different regions of the scalp, with the second overlapping the last part of the first. These waves are related in different ways to the duration of perceptual processing.

Brain↗
PubMed1982

Ideomotor apraxia and P300: a preliminary study.

Event-related cerebral potentials and reaction time were studied in two patients with life parietal lesions inducing ideomotor apraxia and in seven control subjects. Results showed no marked increase of P300 latency in the patients with respect to the control group, whereas the RT was largely lengthened. This suggests that the decision-making processes are left intact in IMA and that only the motor execution stage is impaired.

Adult↗
PubMed1981

Effect of task and stimulus probability on evoked potentials.

Some experimental data demonstrate the existence of at least two different P300s distinguished by latency, topography and functional significance. These positive waves are preceded by a negative component which has been labelled N200. The purpose of this study was to analyze the modifications of these negative and positive components according to probability and task (GO vs. NOGO) in order to better understand the significance of each of them in terms of stages of information processing. Six normal subjects were tested twice on separate days, in a GO-NOGO paradigm. Auditory stimuli - high pitch (GO) and low pitch (NOGO) - were presented in three different occurrence probability combinations: 0.2/0.8; 0.5/0.5; 0.8/0.2, in successive blocks. In both GO and NOGO responses, a vertex N200 component was followed by two positive waves - the first peaking at 300 msec at Cz (Cz : P300), the other one Ca 400 msec at Pz (Pz : P400). An inverse relation between amplitude and probability was seen for the three components but it was twice as large for P400 as for P300. A task effect was only seen for N200, the amplitude and latency of which increased in the GO condition. From the first session to the second, the amplitude of N200 decreased whereas that of P300 increased.

Adult↗