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Biomedical subjects

J Sergent

Publications and source records attributed to J Sergent.

At least 19 recordsLinked to original sources
PubMed2006

[How to carry out the indications of cardiac resynchronization therapy in practice?].

Recent studies have demonstrated that cardiac resynchronization therapy diminish morbidity and mortality of patients with heart failure, who remain symptomatic despite an optimal medical treatment and who have a wide QRS. However, 30% of patients are non-responders. Hence, echocardiography constitutes an interesting tool for the diagnosis of asynchrony. Different echocardiographic indices predict response to cardiac resynchronization therapy. In this article, a practical approach is proposed for these patients.

Cardiac Pacing, Artificial↗
PubMed2006

[Pacemakers and defibrillators: what should we know about home monitoring?].

Cardiac stimulators and defibrillators dispose of diagnostic capabilities. Home monitoring permits to have information about the cardiac rhythm of the patient and about the function of the pacemaker or the defibrillator. Technical aspects, safety and legal issues of home monitoring are discussed in this article.

Arrhythmias, Cardiac↗
PubMed2003

[Isolated carcinoid tumor of the ovary disclosed by tricuspid insufficiency].

A 68-year old woman was hospitalised because of isolated right heart failure. Doppler echocardiography revealed severe tricuspid regurgitation with thickened, shortened, hypomobile leaflets. Pulmonary valve was thickened with mild pulmonary regurgitation. Mitral and aortic valves were normal. The patient was finally diagnosed with carcinoid heart disease from an isolated ovarian carcinoid cancer without hepatic metastases. Ovarectomy was performed and the patient was considered cured of her cancer. Because of refractory right heart failure, she underwent tricuspid valve replacement with a bioprosthesis. Such cardiovascular manifestations are rarely the presenting symptoms of carcinoid disease. Carcinoid heart disease from ovarian primary cancer is exceptional. In this circumstance, carcinoid cardiac lesions may develop in the absence of hepatic metastases because the venous blood from the ovaries drains into the inferior vena cava without hepatic first past effect. Surgical resection of primary ovarian carcinoid tumor is often curative and the prognosis depends mainly on the cardiac condition. The diagnosis of carcinoid syndrome should be discussed in patients with organic tricuspid regurgitation without left valvular disease.

Aged↗
PubMed1996

[Pure epicarditis after surgical repair of atrial septal defect: a rare form of constrictive pericarditis. Apropos of a case].

The authors report a case of constrictive pericarditis occurring two years after surgical repair of an atrial septal defect in a 37 year-old-man. The diagnosis was made by right heart catheterisation and magnetic resonance imaging. The special feature of this clinical case was the exclusive localisation of the fibrosis on the visceral pericardium or epicarditis. The outcome was favourable after resection of the visceral pericardium respecting the parietal pericardium. Magnetic resonance imaging and right heart catheterisation performed 6 months after surgery were normal. Constrictive pericarditis is a classical complication of cardiac surgery but relatively rare after repair of an atrial septal defect. Isolated involvement of the visceral pericardium is rare and allows surgical correction by exclusive epicardectomy respecting the parietal pericardium.

Adult↗
PubMed1994

Brain-imaging studies of cognitive functions.

Little is understood about the brain, the mind and their relationships. However, rapid technical advances in brain-imaging devices such as positron emission tomography (PET), functional magnetic resonance imaging, EEG and EMG have increased the capabilities for visualizing the working brain, and uncovering the cerebral areas participating in the realization of cognitive tasks, and progress in cognitive science has led to a better understanding of the functional architecture of mental abilities. There is, therefore, considerable potential for achieving a greater understanding of the relationships between cognition and cerebral structures through brain-imaging studies of mental functions. However, these studies are confronted with a series of difficulties related to the assumptions that govern their application, the constraints imposed by these techniques on the design of cognitive experiments, the complexities inherent in establishing relations between cognition and anatomy through physiology, and to the interpretation of patterns of cerebral activation. In this article, potential difficulties are described drawing essentially on examples from PET studies of cognitive functions. Whereas a bright future lies ahead for the study of human brain mapping, many problems still have to be overcome and solved in order to exploit the full potential of new brain-imaging techniques.

Brain↗
PubMed1993

Music, the brain and Ravel.

Understanding the functional organization of the cerebral structures underlying receptive and expressive musical processes is confronted with a wide variety of difficulties inherent in the artistic and subjective nature of the musical experience. Yet clarifying the relationships between music and the brain is a legitimate goal of neuroscientific research. One approach toward this goal is based on new developments of brain imaging techniques, and recent investigations indicate that the realization of musical abilities such as sight-reading and piano performance relies on a distributed neural network comprising locally specialized cortical areas. Another approach is concerned with the study of musicians, like Maurice Ravel, who have been affected by brain damage. An analysis of their deficits helps to uncover some properties of music-brain relationships, to identify the essential questions raised by these deficits, and to clarify the neurofunctional anatomy of musical abilities. The understanding of the neurocognitive bases of musical functions is still at an early stage, but recent progress in cognitive and neurofunctional research opens the way to more systematic studies than had so far been possible.

Cerebral Cortex↗
PubMed1992

Distributed neural network underlying musical sight-reading and keyboard performance.

Music, like other forms of expression, requires specific skills for its production, and the organization and representation of these skills in the human brain are not well understood. With the use of positron emission tomography and magnetic resonance imaging, the functional neuroanatomy of musical sight-reading and keyboard performance was studied in ten professional pianists. Reading musical notations and translating these notations into movement patterns on a keyboard resulted in activation of cortical areas distinct from, but adjacent to, those underlying similar verbal operations. These findings help explain why brain damage in musicians may or may not affect both verbal and musical functions depending on the size and location of the damaged area.

Auditory Perception↗
PubMed1992

Functional and anatomical decomposition of face processing: evidence from prosopagnosia and PET study of normal subjects.

Studies of brain-damaged patients have revealed the existence of a selective impairment of face processing, prosopagnosia, resulting from lesions at different loci in the occipital and temporal lobes. The lesions are often extensive, and it is unclear what functional aspects of face processing are normally served by the damaged areas, and whether they are uniquely devoted to the processing of faces. These issues are further addressed through a combined magnetic resonance imaging (MRI) and positron emission tomography (PET) study of regional cerebral blood flow (rCBF) in normal subjects performing different tasks of face and object processing. The results indicate different patterns of cerebral activation depending on the requirements of the tasks within the processing of faces, as well as a clear dissociation of the neural substrates underlying face and object processing. These results are compared with radiological data from prosopagnosic patients, and are put in relation with the patterns of deficits observed in the patients as a function of the location of their lesions. Together, the findings offer new evidence regarding the functional neuroanatomy of face and object processing.

Agnosia↗
PubMed1992

Judgements about numerosity by a commissurotomized subject.

A commissurotomized subject, L.B., was shown asterisks flashed at random locations, up to four in each field, and attempted either to compare the numbers in the two fields or to report the total number. The main results were: (a) Report was more accurate with unilateral than with bilateral presentation, suggesting that the difficulty integrating across fields was partly attentional; (b) in integrating across fields, attention was focused on one field, with only crude 'one-or-many' information from the other; (c) in cross-field comparisons, the focus was on the LVF, but in reporting the number it was on the RVF when report was oral or right-handed, and on the LVF when report was left-handed; (d) cross-field comparisons were improved when the locations were mirrored across the midline.

Adult↗
PubMed1992

Face recognition.

The study of face-selective neurons in the monkey temporal lobe, and face recognition deficits in humans after brain damage have both become very active fields of investigation. Face-selective neurons appear to be members of ensembles for coding faces rather than individual face detectors or grandmother cells. They reflect the more general role of temporal cortex in pattern recognition. In humans there are a variety of face-processing impairments that result from damage to different areas, and which reflect interference at different levels of processing of the facial image.

Animals↗
PubMed1992

Functional neuroanatomy of face and object processing. A positron emission tomography study.

Studies of brain-damaged patients have revealed the existence of a selective impairment of face processing, prosopagnosia, resulting from lesions at different loci in the occipital and temporal lobes. The results of such studies have led to the identification of several cortical areas underlying the processing of faces, but it remains unclear what functional aspects of face processing are served by these areas and whether they are uniquely devoted to the processing of faces. The present study addresses these questions in a positron emission tomography (PET) study of regional cerebral blood flow in normal adults, using the 15 oxygen water bolus technique. The subjects participated in six tasks (with gratings, faces and objects), and the resulting level of cerebral activation was mapped on images of the subjects' cerebral structures obtained through magnetic resonance and was compared between tasks using the subtraction method. Compared with a fixation condition, regional cerebral blood flow (rCBF) changes were found in the striate and extrastriate cortex when subjects had to decide on the orientation of sine-wave gratings. A face-gender categorization resulted in activation changes in the right extrastriate cortex, and a face-identity condition produced additional activation of the fusiform gyrus and anterior temporal cortex of both hemispheres, and of the right parahippocampal gyrus and adjacent areas. Cerebral activation during an object-recognition task occurred essentially in the left occipito-temporal cortex and did not involve the right hemisphere regions specifically activated during the face-identity task. The results provide the first empirical evidence from normal subjects regarding the crucial role of the ventro-medial region of the right hemisphere in face recognition, and they offer new information about the dissociation between face and object processing.

Adult↗
PubMed1991

Judgments of relative position and distance on representations of spatial relations.

This article examines Kosslyn's (1987) hypothesis of the unequal capacity of cerebral hemispheres to process categorical and coordinate spatial relations. Experiment 1 comprised 4 different tasks and failed to support this hypothesis in normal Ss. With the same stimulus patterns as in Kosslyn's study, the results failed to confirm cerebral asymmetry for representing the 2 types of spatial relations, in normal (Experiment 2) and commissurotomized (Experiment 3) Ss. In Experiment 4, a reduction in stimulus luminance produced a partial confirmation of the hypothesis as the right hemisphere proved more adept than the left hemisphere at operating on coordinate representations, whereas both were equally competent at processing categorical spatial-relation representations. The results suggest that the 2 hemispheres can operate on both types of spatial relations, but their respective efficiency depends on the quality of the representations to be processed.

Adult↗
PubMed1991

Processing of spatial relations within and between the disconnected cerebral hemispheres.

This study examined three issues related to the processing of spatial relations by commissurotomized subjects. One issue was concerned with the respective competence of the disconnected cerebral hemispheres at performing judgements of relative position and distance between 2 objects appearing at varying locations in the visual space. Contrary to recent suggestions, the results showed that the two hemispheres were equally competent at representing categorical and coordinate spatial relations and at operating on these representations. The second issue was concerned with the capacity of the two disconnected hemispheres to operate conjointly. The subjects were simultaneously presented with the same information in the two visual fields and were required to produce a single response based on this information. Compared with unilateral presentations, bilateral presentations resulted in enhanced response accuracy and, depending on the type of decision, in patterns of response latency and accuracy different from the patterns of either unilateral condition. These results suggest that the two disconnected hemispheres can operate simultaneously and are able to join the outcomes of their respective operations before the production of a single response. The third issue was concerned with interhemispheric communication of visuospatial information. Unlike pattern information that is typically confined to the hemisphere that receives it in the commissurotomized brain, visuospatial information could be subjected to interhemispheric comparison as a function of its categorical and metric properties, although the patients had only implicit knowledge of part of the transferred information. Implications of these findings for the contribution of the hemispheres to visuospatial processing and for the understanding of the functioning of the commissurotomized brain are discussed.

Adult↗
PubMed1990

The neuropsychology of visual image generation: data, method, and theory.

This paper presents a review of the empirical evidence bearing on the localization of the image-generation process in cerebral structures and examines several issues related to the study of functional hemispheric asymmetry. In spite of recent claims that the left hemisphere is specialized for the generation of mental visual images, an examination of the relevant data and experimental procedures provides little support for this view and suggests that both hemispheres simultaneously and conjointly contribute to this process. Methodological and theoretical issues related to the localization of functions in the brain, some assumptions guiding laterality research, and computational models of cerebral lateralization are briefly discussed.

Brain↗
PubMed1990

Furtive incursions into bicameral minds. Integrative and coordinating role of subcortical structures.

Section of forebrain commissures results in a pervasive disconnection syndrome characterized by the incapacity of the two cerebral hemispheres to exchange their respective information content. Yet commissurotomized patients are capable of unified behaviour in their daily activities and, in laboratory situations, are able to produce a single response as a function of the information received by both hemispheres. This study further investigated the nature of the information that can be communicated between the disconnected hemispheres in 3 commissurotomized patients. The first part comprised 7 experiments in which the patients were required to compare 2 digits simultaneously, 1 projected to each hemisphere. While the stimulus and experimental conditions were the same across experiments, the information content on which to base the comparison was manipulated. The level of performance varied as a function of the information content, such that the patients were unable to decide whether the 2 digits were the same or different, performed better when required to compare the digits in terms of their odd-even category, and were highly accurate at deciding which digit was the higher. In addition, when instructed to focus on the numerical value of the digits to decide whether the 2 digits were the same or different, they performed significantly above chance. In the second part, they were requested to report verbally information about emotional faces and familiar faces projected to the right hemisphere. While they were unable to access the visual characteristics and the identity of the faces, they could provide various correct items of semantic information about the individuals. Taken together, the results indicate that the disconnection syndrome is limited to specific categories of information and does not extend to all the knowledge that may be derived from a given object. They also suggest that subcortical structures do not serve simply as pathways linking the two hemispheres but play an essential coordinating role in the integration of hemisphere activity.

Brain↗
PubMed1990

From covert to overt recognition of faces in a prosopagnosic patient.

Prosopagnosia is an inability to recognize known persons as a result of a failure to access relevant memories through the inspection of their faces. The nature of this disturbance, and the fate of memories related to faces, were investigated in a long-standing prosopagnosic woman (P.V.). An examination of P.V.'s perceptual capacities indicated no major impairment at matching faces, including different views of the same faces, and multidimensional scaling analysis showed that she could achieve configurational representations of faces as do normal subjects. In spite of her inability to evoke memories of known persons from their faces, P.V. displayed clear evidence that she could use pertinent memories related to these faces in tasks that did not explicitly call for their evocation. This covert recognition of faces was observed in perceptual learning and cued-recognized faces, attempts were made at surmounting the blocked activation of pertinent memories. Some of these attempts were successful in inducing P.V. into experiencing a sense of familiarity with the faces and identifying them, and this was the first occurrence of overt face recognition by P.V. since the onset of her illness. These findings provide clarification of the nature of the prosopagnosic disturbance and new information about the processes by which faces are recognized. They suggest that (1) prosopagnosia may result from a breakdown at different levels of face-recognition processes, (2) prosopagnosia may occur in spite of normal configurational encoding of facial representations, (3) covert recognition of overtly unrecognized faces requires the integrity of perceptual processes, and (4) failure of overt face recognition reflects a disturbance in the normal interactions between pertinent memories and facial representations which thus remain meaningless.

Agnosia↗