Biomedical subjects

Manuel Lopes

Publications and source records attributed to Manuel Lopes.

8 recordsLinked to original sources

PubMed2005

Visual learning by imitation with motor representations.

We propose a general architecture for action (mimicking) and program (gesture) level visual imitation. Action-level imitation involves two modules. The viewpoint Transformation (VPT) performs a "rotation" to align the demonstrator's body to that of the learner. The Visuo-Motor Map (VMM) maps this visual information to motor data. For program-level (gesture) imitation, there is an additional module that allows the system to recognize and generate its own interpretation of observed gestures to produce similar gestures/goals at a later stage. Besides the holistic approach to the problem, our approach differs from traditional work in i) the use of motor information for gesture recognition; ii) usage of context (e.g., object affordances) to focus the attention of the recognition system and reduce ambiguities, and iii) use iconic image representations for the hand, as opposed to fitting kinematic models to the video sequence. This approach is motivated by the finding of visuomotor neurons in the F5 area of the macaque brain that suggest that gesture recognition/imitation is performed in motor terms (mirror) and rely on the use of object affordances (canonical) to handle ambiguous actions. Our results show that this approach can outperform more conventional (e.g., pure visual) methods.

Algorithms↗

PubMed2004

Analysis of the bHLH transcription factors Olig1 and Olig2 in brain tumors.

In the absence of specific markers, the histological diagnosis of oligodendroglial tumors is based on subjective qualitative criteria and remains controversial. Recently, two bHLH transcription factors involved in oligodendroglial specification, Olig1 and Olig2 have been proposed as potential markers of oligodendrogliomas. Expression of Olig1/2 was analyzed by in situ hybridization on 78 samples including 47 glial, 29 non-glial tumors, and two non-tumoral brain tissues. Both genes had a similar pattern of expression. Olig1 and Olig2 were expressed in 26/30 (87%) and 28/30 (93%) of oligodendroglial tumors respectively but in only 9% of glioblastomas (1/11). Olig genes were also expressed in the low-grade fibrillary astrocytomas (4/4) and anaplastic astrocytomas (2/2). No expression was found in non-glial tumors, except for one primary cerebral lymphoma. Double staining with PLP, NFH, GFAP showed that olig genes were expressed by mature, non-tumoral oligodendrocytes, but not by normal astrocytes or neurones. This study indicates that Olig1/2 expression clearly distinguishes pure Olig-negative glioblastomas from a wide spectrum of Olig-positive tumors including traditional oligodendrogliomas and oligoastrocytomas, glioblastomas with an oligodendroglial component (GBMO), and WHO grade 2 and 3 astrocytomas. Because Olig genes have a crucial role in oligodendroglial determination, our data could be of help in defining the real spectrum of oligodendroglial tumors.

Astrocytes↗

PubMed2004

Subarachnoid hemorrhage due to cerebral aneurysmal rupture during pregnancy.

Cerebral aneurysmal complications rarely occur during pregnancy. Telling the difference between eclampsia and cerebral hemorrhage due to aneurysmal rupture can prove to be difficult. Aneurysmal management should be performed in an emergency but fetal prognosis should be considered. We report a series of eight pregnant women presenting aneurysmal complications and we have assessed their management and outcome. Both maternal and perinatal mortality rates were correlated with the maternal clinical score. We stress the role of combined care by both neurosurgeons and obstetricians. An emergency cesarean section followed by aneurysmal treatment appears to be a widely accepted strategy in pregnant women with cerebral aneurysmal complications.

Adult↗

PubMed2003

The articulatory loop: study of the subcortical connectivity by electrostimulation.

Although a cortical network involving Broca's area and the supramarginal gyrus (SMG) was widely studied using neurofunctional imaging, the functional connectivity underlying this so-called articulatory loop remains poorly documented. We describe a patient operated on for a glioma invading the left parietal operculum, using intraoperative electrical functional mapping under local anesthesia. Following the identification of cortical language sites within Broca's area and SMG, the subcortical pathways connecting these regions were detected and preserved during the resection. Postoperatively, the patient presented a slight dysarthria, then recovered. This is the first report of direct tracking of the subcortical connectivity underlying the fronto-parietal articulatory loop, allowing to better understand the pathophysiology of this network and the consequences of its damage.

Adult↗

PubMed2003

The role of dominant premotor cortex in language: a study using intraoperative functional mapping in awake patients.

Although the role of the premotor cortex (PMC) was widely studied in motor function, very few data are currently available about the participation of this structure in language. We report a series of 25 right-handed patients harboring a low-grade glioma near or within the left dominant PMC, operated on under local anesthesia with intraoperative real-time sensorimotor and language mappings using electrical stimulations all along the resection. Language tasks consisted of counting and picture naming (preceded by the reading of a short sentence). Stimulations of the left PMC induced transient speech disturbances in all patients, with disruption of both counting and reading/naming during stimulation of the ventral PMC--due to elicitation of an anarthria--while generating an anomia during stimulation of the dorsal PMC. Moreover, corresponding subcortical pathways generated the same language disorders as at the cortical level when stimulated. Eloquent structures were systematically preserved, allowing the avoidance of definitive postoperative deficit. These findings suggest first that the left dominant PMC seems to play a major role in language and second that this structure could have a well-ordered functional organization, namely with the ventral PMC, which might be involved in planification of articulation, and the dorsal PMC, which might be involved in the naming network.

Adult↗

PubMed2003

Usefulness of intraoperative electrical subcortical mapping during surgery for low-grade gliomas located within eloquent brain regions: functional results in a consecutive series of 103 patients.

OBJECT: Although a growing number of authors currently advocate surgery to treat low-grade gliomas, controversy still persists, especially because of the risk of inducing neurological sequelae when the tumor is located within eloquent brain areas. Many researchers performing preoperative neurofunctional imaging and intraoperative electrophysiological methods have recently reported on the usefulness of cortical functional mapping. Despite the frequent involvement of subcortical structures by these gliomas, very few investigators have specifically raised the subject of fiber tracking. The authors in this report describe the importance of mapping cortical and subcortical functional regions by using intraoperative real-time direct electrical stimulations during resection of low-grade gliomas. METHODS: Between 1996 and 2001, 103 patients harboring a corticosubcortical low-grade glioma in an eloquent area, with no or only mild deficit, had undergone surgery during which intraoperative electrical mapping of functional cortical sites and subcortical pathways was performed throughout the procedure. Both eloquent cortical areas and corresponding white fibers were systematically detected and preserved, thus defining the resection boundaries. Despite an 80% rate of immediate postoperative neurological worsening, 94% of patients recovered their preoperative status within 3 months--10% even improved--and then returned to a normal socioprofessional life. Eighty percent of resections were classified as total or subtotal based on control magnetic resonance images. CONCLUSIONS: The use of functional mapping of the white matter together with cortical mapping allowed the authors to optimize the benefit/risk ratio of surgery of low-grade glioma invading eloquent regions. Given that preoperative fiber tracking with the aid of neuroimaging is not yet validated, we used intraoperative real-time cortical and subcortical stimulations as a valuable adjunct to the other mapping methods.

Adolescent↗

PubMed2003

Consent: a Cartesian ideal? Human neural transplantation in Parkinson's disease.

The grafting of human embryonic cells in Parkinson's disease is an innovative and hopefully useful therapeutic approach. However, it still concerns a very small number of patients and is only suggested as a research protocol. We present here a study of the problems of information and consent to research within the framework of this disease in which the efficacy of medical treatment is shortlived. The only French center to use this treatment (Hôpital H. Mondor in Créteil) has received authorization from the Comité Consultatif National d'Ethique (Consultative National Committee on Ethics). Eleven patients were treated between 1991 and 1998. The study of the results of a questionnaire sent to those patients showed the difficulties met in evaluating the perception of information despite intact intellectual capacities in people "prepared to risk everything." In France, the duty to inform patients during research procedures is regulated by the Huriet Act. However, it is not easy to guarantee genuine consent when preliminary information is given to patients psychologically impaired by the slow and ineluctable course of their disease. In these borderline cases, a valid consent seems to be a myth in terms of pure autonomy when considered with the Cartesian aim of elimination of uncertainty. The relevance of this concept of genuine consent probably makes more sense as aiming at a Cartesian ideal which is perhaps more in the spirit rather than in the letter. It is in that same spirit that, from the outset, we propose to define t he practical ways of answering the patients' request for information, even sometimes after consent has been given.

Attitude to Health↗

PubMed2002

Intraoperative mapping of the subcortical language pathways using direct stimulations. An anatomo-functional study.

Functional neuroimaging has improved pre-planning of surgery in eloquent cortical areas, but remains unable to map white matter. Thus, tumour resection in functional subcortical regions still presents a high risk of sequelae. The authors successfully used intraoperative electrical stimulations to perform subcortical language pathway mapping in order to avoid postoperative definitive deficit, and correlated these functional findings with the anatomical location of the eloquent bundles detected using postoperative MRI. At the same time, this also improved knowledge of fibre connectivity. Thirty patients harbouring a cortico-subcortical low-grade glioma in the left dominant hemisphere were operated on whilst awake using intraoperative electrical functional mapping during surgical resection. Language cortical sites and subcortical pathways were clearly identified and preserved in the 30 cases. The anatomo-functional correlations between data obtained using intraoperative subcortical mapping and postoperative MRI revealed the existence in all patients of common pathways which seem essential to language. This was shown by inducing reproducible speech disturbances during stimulations as follows: the subcallosal fasciculus (initiation disorders), the periventricular white matter (dysarthria), the arcuate fasciculus and the insular connections (anomia). Clinically, all patients except three presented a transient postoperative dysphasia, which resolved within 3 months. On control MRI, 14 resections were total and 16 subtotal due to infiltration of functional bundles described above. It is recommended that the combination of the techniques as described could prove ideal for future non-invasive reliable subcortical mapping both in healthy volunteers and in patients harbouring a (cortico)subcortical lesion in order to optimize surgical pre-planning.

Adult↗