Search PubMed⌕ Search

Biomedical subjects

F Mauguiere

Publications and source records attributed to F Mauguiere.

At least 37 records · Page 2Linked to original sources
PubMed1985

Sequential colour mapping system of brain potentials.

We present a colour mapping system for the visualization of both the spatial scalp distribution and the temporal evolution of brain potentials. The system is applicable to recordings of auditory, visual and somatosensory potentials. It uses a Tektronix 4113 colour terminal connected to a Solar 16 (SEMS) mini-computer. The brain potentials are recorded on up to 16 scalp electrodes. The gain and the baseline are corrected separately on each channel. At each point of the scalp the potential is reconstructed by a linear interpolation of the measured potentials of the four nearest electrodes. Simultaneously n2 (1 less than n less than 8) colour maps can be presented on the screen. This allows the study of the temporal evolution of full scalp evoked potentials. The user chooses the two extreme latencies defining the time window to be explored and the latencies of the maps are regularly time-spaced within this window. In a typical case, in which four maps are desired, the latencies of the maps can be chosen independently. The 16-colour palette is predetermined but the user has three possibilities to establish the correspondence between the electrical potential and the colours. Examples are shown in the visual and somatosensory stimulation modalities. The advantages and limitations of such a representation are discussed.

Brain↗
PubMed1985

[Control of visual exploration: anatomic and physiologic data].

The idea that saccadic eye movements necessary for visual space exploration could be under the control of the frontal eye field was based mainly upon Ferrier's early experiments of electrical stimulation of the cortex. More recent anatomical as well physiological data have demonstrated in monkeys that the sensori-motor processing needed to locate visual targets and to program an accurate eye movement to them is achieved in the superior colliculus, the frontal prearcurate and the posterior parietal cortices. Cells in those three structures have been identified by microelectrode studies that modify their response to a visual target before any eye movement when a saccade directed to this stimulus is to occur. Motivation to move the eyes towards the stimulus is under the control of the limbic cortex of the cingulate gyrus. Lesions to any of these structures lead to a neglect phenomenon characterized by the paucity of spontaneous saccades towards the half of space opposite to the lesion. In primates and in man neglect is observed only after cortical or thalamic lesions but not, or very transiently, after collicular lesion. The prearcuate frontal, the cingulate, and the posterior parietal cortices are interconnected via direct cortico-cortical fibres and also by a cortico-thalamo-cortical circuit, the thalamic relay of which is the medial pulvinar. The medial pulvinar is known to receive polymodal sensory informations from the intermediate layers of the superior colliculus. Thus a complete network involving cortical, thalamic and subthalamic structures is responsible for a very secure and redundant control of gaze.

Afferent Pathways↗
PubMed1984

[Visual evoked potentials (VEP's) obtained by black and white or red and black checkerboard inversion. Results in healthy subjects and in multilocular sclerosis patients].

Visual evoked potentials (VEPs) were elicited in a control group and in 125 multiple sclerosis (MS) patients by reversal of TV black and white checkerboard patterns with two different check sizes and contrasts (44'/contrast 50%; 22'/contrast 20%), and also by a display of red light emitting diodes (LEDs) generating a 'true' pattern reversal. In control subjects LED pattern reversal produced responses of lower amplitude and of longer latency compared to responses to TV black and white checkerboards. The interindividual variability of P100 latency was lower with the LED display than with the low contrasted TV pattern. In 18 patients with definite or suspected MS, VEPs were normal with the two TV patterns when delayed or absent with the LED display. Thus LED pattern reversal was a more effective stimulus than black and white pattern reversal for the detection of demyelinating lesions of the optic nerves in MS. LED stimulation proved to be particularly useful in patients with progressive spastic paraparesis or with previous history of isolated optic neuritis.

Adult↗
PubMed1983

A crossed corticotectal projection from the lateral suprasylvian area in the cat.

Crossed cortical projections to the superior colliculus of the cat were demonstrated by unilateral superior colliculus injections of horseradish peroxidase (HRP) and by cortical injections of radioactive amino acids. This crossed corticotectal projection originates in the lateral bank of the middle suprasylvian sulcus and in both banks of the posterior suprasylvian sulcus. The site of termination of the contralateral corticotectal projection is restricted to the anterior margin of the superior colliculus (SC) while the ipsilateral projection spreads over the whole SC. The contralateral terminal areas are restricted to the superficial tectal layers. The projection fibers reach the contralateral superior colliculus by crossing the collicular commissure. The existence of such a connection may help to explain certain electrophysiological observations.

Animals↗
PubMed1983

[Cervical somatosensory evoked potentials in the healthy subject: analysis of the effect of the location of the reference electrode on aspects of the responses].

Cervical SEPs were recorded in 111 normal subjects following stimulation of the median nerve at the wrist, using 3 different sites for the reference electrode (Fz, earlobe, shoulder). It was shown that cephalic reference electrodes (Fz or earlobe) modify the wave form of the cervical response, because they pick up far-field SEPs (P9, P11, P13, P14) originating from cervical roots, spinal cord and brainstem. These far-field SEP components are injected as negativities in the activity recorded by the cervical electrode. The responses recorded with cephalic reference differ from those recorded at the same cervical site, with a non-cephalic reference in 3 main points: (1) the amplitude of negative components N11 and N13 is increased; (2) the onset latency of N11 is significantly shorter; (3) an N14 negativity is added, the origin of which is probably in the brainstem; this component may occupy the peak of the cervical negativity; thus the central conduction time, calculated as the time interval between N14 and N20, does not take into account the time for spinal propagation of the somatosensory afferent inputs. A topographic study of cervical responses in 10 normal subjects showed an increase of the onset latency of N11 (mean 0.89) from the lower cervical region to the cervico-occipital junction, provided that a non-cephalic reference is used. This result suggests that N11 corresponds to the travelling of action potentials in the ascending spinal somatosensory pathways. The use of a medio-frontal (Fz) reference electrode results in: (1) a masking of the latency shift of N11 latency because of the subtraction of the far-field Fz-recorded P11 component, the onset of which was found to be synchronous with the entry of afferent volleys in the lower cervical spinal cord; (2) a modification of the spatial organization of the responses, due to the subtraction of far-field scalp-recorded positivities P9, P11, P13 and P14, that creates negative N9, N11, N13 and N14 potentials far below the level where cervical roots enter the spinal cord.

Adult↗
PubMed1982

[Discriminant analysis of graphic elements of the EEG. Application to the detection of episodes of diffuse spike-waves].

A database of EEG information was collected from EEG recordings performed in epileptic patients with diffuse spike-wave complex discharges. Normal activity, spike-waves, slow waves and artefacts were mixed up in these recordings. The analysis of EEGs stored in the database was performed, channel by channel, through a 2.56 s moving window. For each so defined EEG sequence, a set of 22 variables chosen for their discriminatory power was computed. A subset of 8 highly discriminating variables was selected by the means of a stepwise discriminant analysis. Each class of the learning set contained 40 up to 100 EEG sequences. A classifying algorithm that takes into account zones of uncertainty is proposed. It has been evaluated on a test set which was composed of 1981 EEG sequences issued from 15 different patients. The results have been checked by two neurologists. The agreement rate between each of them and the proposed algorithm was more than 92%; this result is comparable to the agreement rate between the two neurologists (94%). A contextual analysis algorithm, using bi-dimensional smoothing techniques, allowed to improve the agreement rates which exceeded 94%.

Computers↗
PubMed1981

[Short-latency somatosensory evoked potentials (SEPs) in dyssynergia cerebellaris myoclonica (author's transl)].

Short-latency SEPs following stimulation of the median nerve at the wrist have been studied in 6 patients suffering from dyssynergia cerebellaris myoclonica (DCM). Cervical N14 and scalp-recorded P15 potentials were found to be normal in patients with appropriate recording conditions. The N20 potential, usually recorded in normals in the parietal region contralateral to the stimulated side, was recorded only in 3 cases out of 6. When present, the N20 potential was found to be normal in latency, amplitude and topography. These data suggest that the electrophysiological events related with information processing at the subcortical levels of the lemniscal pathways (N14, P15) are unmodified in DCM, and lend substance to the hypothesis of a cortical long-loop reflex responsible for the triggering of intention myoclonus in these patients.

Adult↗
PubMed1980

The duality of the cingulate gyrus in monkey. Neuroanatomical study and functional hypothesis.

According to most behavioural, electrophysiological, and clinical studies, the cingulate gyrus is widely thought to be involved in regulation of emotional life, reactivity to painful stimuli, memory processing, and attention to sensory stimuli. Anatomically the cingulate cortex is composed of two distinct areas numbered 24 and 23 in Brodmann's classification. We have investigated the connections of the cingulate gyrus in monkeys, using horseradish peroxydase and radioautographic techniques, in order to verify the hypothesis of an anatomical complementarity of these cytoarchitectonic subdivisions. The posterior cingulate gyrus (area 23) is specifically connected with the associative temporal cortex, the medial temporal and orbitofrontal cortices, and with the medial pulvinar. The anterior cingulate gyrus (area 24) is related to the intralaminar, mediodorsal, and ventral anterior thalamic nuclei, the amygdala, and the nucleus accumbens septi. The two cingulate areas were found to be interconnected and to have, in common, connections with the 'limbic' thalamic nuclei (AM, AV, LD), the caudate nucleus, the claustrum, the lateral frontal and the posterior parietal (area 7) cortices.

Afferent Pathways↗
PubMed1978

Projections of the ascending somesthetic pathways to the cat superior colliculus visualized by the horseradish peroxidase technique.

Projections of the somesthetic ascending pathways to the superior colliculus (SC) of the cat have been demonstrated by means of the horseradish peroxidase (HRP) tracing technique. Following HRP injection in one SC, marked neurons were found in the contralateral dorsal horn and in the contralateral dorsal column nuclei, mainly the cuneate nucleus. Moreover, in the contralateral trigeminal complex, the sub-nucleus caudalis of the spinal nucleus of the Vth nerve, and the subnucleus oralis plus the main sensory trigeminal nucleus were labeled. Thus, the anterolateral system and the lemniscal system subserving face and forelimb sensation send afferent fibers to the contralateral SC.

Afferent Pathways↗
PubMed1978

["Functional and anatomical organization of associative" cortical areas 7, 21 and 22 in monkeys. A study of the cortical projections from the pulvinar by means of HRP tracing technique (author's transl)].

The thalamic projections to the parietal and temporal associative areas (Brodmann's areas 7, 21 and 22) have been revealed by means of the retrograde axonal transport of horseradish peroxidase (HRP). The medial pulvinar (PM) was found to send afferents to the three studied areas. Labelled neurones of the PM appeared to be grouped in terms of their cortical target; indeed, neurones of origin of projection fibres to areas 7, 21 and 22 were respectively localized in the dorso-lateral, ventro-lateral and ventro-medial part of the PM. Although the multimodal sensory nature of the PM has been demonstrated by electrophysiological works, the function of PM neurones and the significance of their topographical repartition remain unknown. However PM could be involved in the transmission of specific sensory informations to the three associative areas 7, 21 and 22. Such an hypothesis is discussed according to the hitherto available data.

Afferent Pathways↗
PubMed1975

Epileptogenic properties of folic acid and N5 methyltetrahydrofolate in cat.

The epileptogenic properties of folic acid and N5-methyltetrahydrofolate applied locally on the cortex were compared in cats. Neither substance was epileptogenic except in very high concentration, on the order of 10(-3) M. N5-Methyltetrahydrofolate, the folate derivative most widely distributed in the central nervous system and CSF of mammals, was not more epileptogenic than folic acid. Because the level of N5-methyltetrahydrofolate is only slightly diminished in patients treated with anticonvulsants, the change cannot account for the therapeutic effect of the drugs.

Animals↗