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A Marillaud

Publications and source records attributed to A Marillaud.

17 recordsLinked to original sources
PubMed1994

Three-dimensional planar and vector analysis of brainstem auditory evoked potentials as a function of intensity in guinea pig.

Brainstem auditory evoked potentials (BAEPs) have been studied in guinea pigs as a function of intensity by means of the Three-channel Lissajous' trajectory (3-CLT) method. Data were quantified in terms of duration, orientation of planar segments and orientation of equivalent dipoles. The auditory stimulus was a click varying from 48 dB pSPL to 108 dB pSPL by steps of 10 dB pSPL. A semi-automated procedure was used to identify planar segments, by calculating the curvature (apex) and magnitude curves. Dipole analysis was made at the corresponding magnitude peaks and apices. Taking into account a symmetrical orientation of planar segments and equivalent dipoles, similar results were obtained after right and left stimulation. Six planar segments, A, B, C, D, E, F were analysed as were six equivalent dipoles corresponding roughly to P1, N1, P3, N3, P4 and N4 on a vertical lead. There was a parallel latency shift of the first and last point of planar segments as a function of intensity, accounting for the stable duration of a planar segment. Planar segment D (roughly corresponding to N3 on a vertical lead) disappeared as the intensity decreased. Only planar segments C and F and dipole N3 showed a significant change in their orientation. The stable duration of planar segments suggests that intensity coding in the auditory brainstem, in terms of a global function of a system, involved the same number of synapses in a serial circuit while the activated neurons increase in the in parallel circuitry, as the intensity increases. Similar changes in orientation of planar segments C (including P3 of guinea pig BAEPs) and F (including N4 of guinea pig BAEPs) suggest a possible common source with a depolarization followed by a repolarization.

Acoustic Stimulation↗
PubMed1992

[Comparative study by computerized EEG of dementia of the ALzheimer type and Parkinson's disease with dementia].

A computerized EEG (cEEG) study was performed in two groups of patients with dementia of the Alzheimer type (DAT) and with Parkinson's disease with dementia (PDD). Compared to control subjects suffering from Parkinson's disease without dementia, both groups demonstrated similar slowing down of background activity. However, there were more low frequency components, defined as between 2.5-7 Hz, and less topographical differentiation in PDD than in DAT. Furthermore, more severe impairment of cognitive functions was observed in DAT, but their psychometric score correlated with slowing down of EEG only in DMP. These observations emphasize the influence of the subcortical/cortical axis both in dementia of Parkinson's disease and in the neurophysiology of the EEG.

Aged↗
PubMed1991

Same location of the source of P1 of BAEPs and N1 of CAP in guinea pig.

The purpose of this study was to point out the location of N1 and N2 of the compound action potential (CAP) and the first waves of the brainstem auditory evoked potentials (BAEPs) by the mean of the section of the eighth nerve at the porus acousticus in guinea pigs. Our results agree with most of the studies in the literature. In the absence of lesion of the internal auditory artery, the section of the cochlear nerve induced the persistence, alone, of the P1 of BAEPs in which latency was similar to initial P1 before section, and the subsequent waves disappeared. Simultaneously, a monophasic negative potential (N1) of the auditory nerve remained without N2. When the section included the internal auditory artery all BAEPs and CAP components disappeared simultaneously and very suddenly just after the section. These results definitively excluded a proximal contribution of the cochlear nerve in the N1 of CAP and P1 of BAEPs. The N2 of CAP and P2 of BAEPs are not generated, even in part, in the intracochlear or intrapetrous portion of the cochlear nerve.

Action Potentials↗
PubMed1990

Microcomputer analysis of three-channel Lissajous' trajectory of auditory brainstem evoked potentials.

A software package for the IBM PC computer is presented to facilitate the analysis of three-channel Lissajous' trajectories (3CLT) of auditory brainstem potentials. The program deals with 4-channel numeric or ASCII files, including three orthogonal X, Y, Z channels and standard vertex-mastoid on the stimulated side. The 3CLT analysis program implements standard measurements of peak latencies, voltage amplitude and curvature plots computed from the three orthogonal channels, interactive three-dimensional rotations of the trajectory and planar segment analysis. Parameter estimates of the best-fit plane are computed for any part of the trajectory limited by two latency cursors. Results are displayed and stored in a table including segment bounds and duration, sight vector orientation, plane equation parameters and adjustment criteria.

Evoked Potentials, Auditory↗
PubMed1988

[Auditory evoked potentials of the brain stem in brain death].

Brainstem auditory evoked responses were recorded in a neurosurgical intensive care unit in 38 patients who had all the clinical criteria for brain death. Of the brain-dead patients, 65.8% never showed a response. 3.42% showed a type I wave, which was unilateral in 26.3% and bilateral in the other 7.9%. Types II to VII waves were never seen. An increase in latency of type I waves (2.25 +/- 0.24 ms) was noted. The interest and the limits of this non invasive electrophysiologic technique for the diagnosis of brain death are discussed.

Adolescent↗
PubMed1988

Effects of electrolytic lesions of the superior olivary complex and trapezoid body on brainstem auditory-evoked potentials in the guinea pig. II. Three-channel Lissajous' trajectory analysis.

Brainstem auditory-evoked potentials (BAEP) were studied both with vertex (positive) - tragus (negative) derivation and three-channel Lissajous' trajectory (3-CLT) planar analysis in guinea pigs (GP) after destruction of the ipsilateral superior olivary complex (SOC) (6 GP), contralateral SOC (8 GP) referred to the stimulation side, and trapezoid body (TB) in the sagittal line (8 GP). The size of the lesion was evaluated on histological examination. The right ear was locally destroyed with aminoside instillation. The left ear was stimulated with unfiltered clicks and tone bursts of different frequencies at 100 dB SPL. Three questions were the basis of this study: (i) What are the effects of brainstem lesions on 3-CLT? (ii) Is there a relationship between planar segments and underlying sources? (iii) What is the generator of planar segment C (P3) in GP? 3-CLT analysis was made on plane A (corresponding to P1 on a vertex-tragus channel), plane B (N1-P2) and plane C (P3.) Plane C disappeared after TB lesions and remained after ipsi- and contralateral SOC destructions. However, plane C disappeared after extensive lesions to the contralateral SOC affecting the TB. Planes A and B were always observed whatever the lesion, with sometimes a modification of their orientation. A localized brainstem lesion induced a local modification of the three-dimensional trajectory. These data are in agreement with the assumption that some planes of 3-CLT reflect the activity of underlying generators. However, the loop which contains the planar segment is a better indicator of the global electrical activity of the source. Plane C (P3) would have a contralateral source which is probably not the SOC but the afferent curved fibers of the TB close to the contralateral SOC.

Animals↗
PubMed1986

Digitization of electrophysiological documents.

The mechanism presented in this paper is devoted to the transfer of paper documents as electrophysiological records into 'electronic documents' for direct storage and analysis by a computer.

Computers↗
PubMed1986

[Characteristics of 3-dimensional representations of brain stem auditory evoked potentials].

The three dimensional Lissajous curves (3 CLT) of orthogonal derivation (vertex Z+; throat Z-) (left mastoïd Y+; right mastoïd Y-) (nasion X+; neck X-) were calculated and recorded by a computer. 3-D curves were computed with an apparent rotation around the vertical axis Z. Through successive exhibition of the "virtual" plots, the observer will remark a spatial representation of the 3-D curve. As in vectocardiography, a careful scrutiny of these curves displays different planar segments. Of the different coordinates specifying planar segments position in space: azimuth and elevation are the most reproducible. This paper describes the graphic and automatic measurements submitted and gives the results obtained from subjects with normal hearing.

Brain Stem↗
PubMed1986

Three-dimensional curves: main parameters of brainstem auditory-evoked responses in the normal subject.

Brainstem evoked potentials (BER) have been studied in three dimensions (3D). It was necessary to record simultaneously three orthogonal derivations in the three spatial axes. The 3D curves obtained were formed by successive uncompletely locked loops which correspond with the first five waves of BER. Planar segment could be identified in the 3D curves; planes were defined by geometrical parameters, following standard analytic geometry. The 3D curves appeared to be symmetrical after right and left stimulation, and were almost completely flattened around the anteroposterior axis after binaural stimulation. This flattening was not observed in the case of multiple sclerosis.

Acoustic Stimulation↗
PubMed1982

[Sodium gamma-hydroxybutyrate. Effects on visual flash-evoked potentials].

Na gamma hydroxybutyrate being recognized as a mean of brain protection, the effect of Na gamma hydroxybutyrate on visual evoked potentials is studied in ten neurosurgical patients. Recordings are made in the same intensive care unit and with the same equipment. Latencies of the three principal peaks (III, IV, V) are analysed. No gamma hydroxybutyrate, given intravenously (60 mg . kg-1), significantly increased latencies (p less than 0,001). So, it must take into account of this effect when visual evoked potentials are studied in Na gamma hydroxybutyrate treated-patients. However, visual evoked potentials peaks are only delayed by Na gamma hydroxybutyrate and none of the studied peaks is abolished.

Brain Diseases↗
PubMed1980

Impairment of memorization by high doses of pyridoxine in man.

Two controlled trials were performed successively to evaluate the effect of high doses of oral pyridoxine on brain performance in man. In trial I, medical students volunteered to take 100 mg, 500 mg of pyridoxine a day or placebo for 10 days. A digit coding test was performed before, and at the end of the treatment period and a third 15 days later. The improvement of performance from the first to the third test (learning effect) was significantly better in the placebo group than in the B6 treated groups. This could be attributed to memorization of skills. Trial II was performed in obese patients starting a low calorie diet in whom vitamins are routinely prescribed. Performance in a work recognition test and in a visual retention test was lower for the group receiving 1 g of pyridoxine a day. Thus, high doses of oral pyridoxine are likely to impair memorization in man. Disturbances of neuro-transmitter metabolism such as increase of GABA production might explain the effect. As the benefit of high doses of pyridoxine has not been well-documented and as the study has suggested that undesired effects may indeed exist, the widespread use of such doses is questionable.

Adult↗
PubMedDate not supplied

Wave III of brain-stem auditory evoked potentials analysed both with 3-channel Lissajous' trajectory and dipole localization method.

Wave III of the BAEP was analysed both with 3-channel Lissajous' trajectory (3-CLT) and a dipole localization method. The experiments were performed on 5 normally hearing subjects. The dipole analysis used an iterative algorithm assuming a spherical head model and homogeneous media. 3-CLT planar analysis was performed with a laboratory system. The parameters of plane C (azimuth and elevation) corresponding to wave III and those of the equivalent dipole showed a similar orientation of the plane and the dipole. This result is in agreement with previous investigations and confirms the interest of 3-CLT in far-field analysis and, at the same time, validates the dipole localization model used in this study, at least for BAEP analysis.

Adult↗
PubMedDate not supplied

[A method for recording auditory evoked brain stem responses for use with objective audiometry and in neurology (author's transl)].

After defining the auditory evoked brain stem responses, the authors discuss the importance of the recording conditions and their influence on the recorded response. The choice of leads, frequency of stimulus repetition and strength of stimulus are all modifying factors. In objective audiometry it seemed preeferable to choose the technical conditions which would highlight wave V, which is identifiable even with stimuli close to threshold. The experimental conditions must be different for neurological investigation because one requires to visualise all the waves constituting the response.

Adolescent↗