Papers by Francisco Gonzalez varela
Ce livre est la version francaise de l'ouvrage "Naturalizing phenomenology : issues in c... more Ce livre est la version francaise de l'ouvrage "Naturalizing phenomenology : issues in contemporary phenomenology and cognitive science", Stanford Univ. Press, 1999
Nature, 1999
Transient periods of synchronization of oscillating neuronal discharges in the frequency range 30... more Transient periods of synchronization of oscillating neuronal discharges in the frequency range 30±80 Hz (gamma oscillations) have been proposed to act as an integrative mechanism that may bring a widely distributed set of neurons together into a coherent ensemble that underlies a cognitive act 1±4. Results of several experiments in animals provide support for this idea (see, for example, refs 4±10). In humans, gamma oscillations have been
Fermentation Technology, 2017
Lupinus mutabilis (LM) is a widespread species of lupin whose bean is consumed not only for its h... more Lupinus mutabilis (LM) is a widespread species of lupin whose bean is consumed not only for its high caloric value but also as a homeopathic medicine, used for a diverse range of presumed clinical properties, including as an analgesic and an antidiabetic. The properties of lupine alkaloids are responsible for their anticholinergic toxicity in both the autonomic nervous system and the central nervous system (CNS). As this syndrome may vary in severity, lupinus toxicity should be suspected in patients with isolated symptoms as well, such as hyporeactive mydriasis. We present a case of a 48-year-old male patient presented to emergency department complaining about blurred vision, dizziness and palpitations. Physical examination only reveal hyporeactive mydriasis. Urine drug screening was negative and labs were otherwise within normal ranges. Brain Computed Tomography did not identify any abnormality. During the examination patient admitted that he was taking homeopathic medication for his osteoarthritis pain that contains high amounts of LM. He received hydration with parenteral saline while maintaining an adequate diuretic rhythm. Twelve hours later, his mydriasis had completely resolved. Clinicians should consider the possibility of LM toxicity in cases of pupillary abnormalities without any clear alternative explanation.
We argue that phenomenology can be of central and positive importance to the cognitive sciences, ... more We argue that phenomenology can be of central and positive importance to the cognitive sciences, and that it can also learn from the empirical research conducted in those sciences. We discuss the project of naturalizing phenomenology and how this can be best accomplished. We provide several examples of how phenomenology and the cognitive sciences can integrate their research. Specifically, we consider issues related to embodied cognition and intersubjectivity. We provide a detailed analysis of issues related to time-consciousness, with reference to understanding schizophrenia and the loss of the sense of agency. We offer a positive proposal to address these issues based on a neurobiological dynamic-systems model.
Jorge G. F. Falorca Os novos preceitos de acessibilidade para PMC's no contexto do projecto e da ... more Jorge G. F. Falorca Os novos preceitos de acessibilidade para PMC's no contexto do projecto e da construção-uma visão global e os problemas associados GP
La investigacion actual en simulacion dinamica de sistemas multicuerpo (MBS) gira en torno a dos ... more La investigacion actual en simulacion dinamica de sistemas multicuerpo (MBS) gira en torno a dos objetivos principales: el incremento de la eficiencia computacional del software que lleva a cabo las simulaciones y la diversificacion de las tareas que este es capaz de realizar, a veces mediante la inclusion en los calculos de fenomenos no puramente mecanicos. Este trabajo aborda ambos objetivos, estudiando el efecto de la implementacion del codigo fuente en el rendimiento del software, asi como las diferentes estrategias de comunicacion con programas externos que puedan aportar a la simulacion multicuerpo la interaccion con elementos de naturaleza no mecanica. El primer capitulo de esta tesis consiste en una breve introduccion al estado actual del software para simulacion de sistemas multicuerpo. En el se muestran tambien las lineas de investigacion en las que se enmarca el proyecto y se senalan sus objetivos principales. El segundo capitulo describe la arquitectura del software para la simulacion de sistemas multicuerpo que se ha creado en esta investigacion. Para su implementacion se ha utilizado el lenguaje C++, dentro del paradigma de programacion orientada a objetos. En este capitulo se enumeran tambien las herramientas de programacion utilizadas en el proceso y se obtienen conclusiones de validez general para la generacion de programas multicuerpo. Los capitulos tercero y cuarto presentan tecnicas de implementacion eficiente de las operaciones de algebra lineal y en la paralelizacion del codigo, respectivamente. Se han cuantificado las mejoras en el tiempo de ejecucion obtenidas y se han delimitado los campos de aplicacion de cada estrategia. En los capitulos quinto y sexto se aborda la comunicacion del software desarrollado con otros programas de simulacion externos. Se ha realizado un estudio comparativo de los diversos modos posibles en que se puede realizar esta union y, ademas, se ha evaluado el impacto del empleo de tecnicas de cosimulacion multirate sobre la eficiencia y la precision de los calculos. Se ha disenado para ello una interfaz generica entre el software MBS y MATLAB/Simulink, una aplicacion matematica y de diagramas de bloques de gran aceptacion entre la comunidad de investigacion en sistemas multicuerpo. Por ultimo, en el capitulo septimo se resumen las conclusiones del presente trabajo y se proponen lineas de investigacion futuras que pueden derivarse de el.
Visual Neuroscience, 1996
Multiunit activity was recorded in the optic tectum of awake pigeons with two electrodes at sites... more Multiunit activity was recorded in the optic tectum of awake pigeons with two electrodes at sites varying in depth and separated by 0.3 to 3.0 mm. Autocorrelation and cross-correlation functions were computed from the recorded spike trains to determine temporal relationships in the neuronal firing patterns. Cross-correlation analysis revealed that spatially separate groups of cells in the tectum show synchronous responses to a visual stimulus. Strong synchronization occurred in both superficial and deep layers of the tectum, in general with zero-phase shift. The response synchronization in the avian optic tectum resembles that observed in the mammalian cortex, suggesting that it may subserve common functions in visual processing.
Cognitive Brain Research, 2003
We applied a new method of imaging frequency-specific changes in brain activity in humans during ... more We applied a new method of imaging frequency-specific changes in brain activity in humans during a finger brushing task in order to measure changes in cortical rhythms during tactile stimulation. Neuromagnetic recordings were conducted in five subjects using a whole-head MEG system during tactile stimulation of the right index finger, with or without visual feedback, and while viewing another individual's index finger being stimulated. Volumetric images of changes in source power relative to pre-stimulus baseline levels were computed with 2 mm resolution over the entire brain using a minimum-variance beamforming algorithm (synthetic aperture magnetometry). Onset of tactile stimulation produced a brief (200-300 ms) suppression of mu band (8-15 Hz) and beta band (15-30 Hz) cortical activity in the primary somatosensory and primary motor cortex, respectively, followed by a bilateral increase in beta band activity ('beta rebound') in motor cortex. This pattern of suppression / rebound was absent when subjects observed finger brushing or brushing motions without receiving stimulation. In contrast, these conditions resulted in bilateral increases in beta band activity in sensorimotor areas and decreased power in the alpha (8-12 Hz) band in primary visual areas. These results show that spatially filtered MEG provides a useful method for directly imaging the temporal sequence of changes in cortical rhythms during transient tactile stimulation, and provide evidence that observation of tactile input to another individual's hand, or object motion itself, can influence independent rhythmic activity in visual and sensorimotor cortex.
Rendiconti del Circolo Matematico di Palermo, 1984
Boston Studies in the Philosophy of Science, 1991
Organism connotes a knotty dialectic: a living system makes itself into a entity distinct from it... more Organism connotes a knotty dialectic: a living system makes itself into a entity distinct from its environment through a process that brings forth, through that very process, a world proper to the organism.
Boston Studies in the Philosophy of Science, 1980
Teleology and teleonomy are notions employed in discourse, descriptive and explanatory, about liv... more Teleology and teleonomy are notions employed in discourse, descriptive and explanatory, about living systems, and although it is claimed that they do not necessarily enter as causal elements in their functioning, it is asserted that they are essential definitory features of their organization. Our present aim is to show that in the light of the preceding discussion, these notions are unnecessary for the understanding of the living organization.
Advances in Consciousness Research, 2003
This book searches for the sources and means for a disciplined practical approach to exploring hu... more This book searches for the sources and means for a disciplined practical approach to exploring human experience. The spirit of this book is pragmatic and relies on a Husserlian phenomenology primarily understood as a method of exploring our experience. The authors do not aim at a neo-Kantian a priori ‘new theory’ of experience but instead they describe a concrete activity: how we examine what we live through, how we become aware of our own mental life. The range of experiences of which we can become aware is vast: all the normal dimensions of human life (perception, motion, memory, imagination, speech, everyday social interactions), cognitive events that can be precisely defined as tasks in laboratory experiments (e.g., a protocol for visual attention), but also manifestations of mental life more fraught with meaning (dreaming, intense emotions, social tensions, altered states of consciousness). The central assertion in this work is that this immanent ability is habitually ignored or at best practiced unsystematically, that is to say, blindly. Exploring human experience amounts to developing and cultivating this basic ability through specific training. Only a hands-on, non-dogmatic approach can lead to progress, and that is what animates this book. (Series B)
Physica D: Nonlinear Phenomena, 1999
The degree of interdependence between intracranial electroencephalographic (EEG) channels was inv... more The degree of interdependence between intracranial electroencephalographic (EEG) channels was investigated in epileptic patients with temporal lobe seizures during interictal (between seizures) periods. With a novel method to characterize nonlinear cross-predictability, that is, the predictability of one channel using another channel as data base, we demonstrated here a possibility to extract information on the spatio-temporal organization of interactions between multichannel recording sites. This method determines whether two channels contain common activity, and often, whether one channel contains activity induced by the activity of the other channel. In particular, the technique and the comparison with surrogate data demonstrated that transient large-scale nonlinear entrainments by the epileptogenic region can be identified, this with or without epileptic activity. Furthermore, these recurrent activities related with the epileptic foci occurred in well-defined spatio-temporal patterns. This suggests that the epileptogenic region can exhibit very subtle influences on other brain regions during an interictal period and raises the possibility that the cross-predictability analysis of interictal data may be used as a significant aid in locating epileptogenic foci.
Journal of the Neurological Sciences, 2014
Background: Multiple sclerosis is a complex disease in which genetic susceptibility plays a role ... more Background: Multiple sclerosis is a complex disease in which genetic susceptibility plays a role and familial occurrence has long been recognized. To date, no studies of familial occurrence have been conducted in Argentina, a country with low to intermediate prevalence. Methods: As part of a cross-sectional study on multiple sclerosis in Buenos Aires, immediate and extended pedigree details were collected on 219 patients. Crude and age-adjusted recurrence risks for patient relatives were also assessed. Results: Details on age or age of death and disease status were obtained for 4227 relatives. Ten percent of patients reported at least one relative with MS diagnosis, the highest risk (1.54%) was observed in daughters of patients who presented 92-times greater risk than the general population. Sibling recurrence risk ratio was similar to that reported in other locations. Conclusions: Relatives of patients with MS living in Argentina are at greater risk of developing the disease, although not as high as the risk reported for other geographic regions.
Trends in Cognitive Sciences, 2001
We propose a new approach to the neuroscience of consciousness, growing out of the ‘enactive’... more We propose a new approach to the neuroscience of consciousness, growing out of the ‘enactive’ viewpoint in cognitive science. T his approach aims to map the neural substrates of consciousness at the level of large-scale, emergent and transient dynamical patterns of brain activity (rather than at the level of particular circuits or classes of neurons), and it suggests that the processes crucial for consciousness cut across the brainâ€"bodyâ€"world divisions, rather than being brain-bound neural events. Whereas Previous Previous article Next Next article Check if you have access through your login credentials or your institution.
Multiple Sclerosis International, 2014
Background. Comorbid autoimmune diseases in MS patients have been studied extensively with contro... more Background. Comorbid autoimmune diseases in MS patients have been studied extensively with controversial results. Moreover, no such data exists for Latin-American MS patients.Methods. We conducted a case-control study aimed to establish the prevalence of autoimmune disorders in a cohort of Argentinean MS patients.Results. There were no significant differences in autoimmune disease prevalence in MS patients with respect to controls. The presence of one or more autoimmune disorders did not increase risk of MS (OR 0.85, 95% CI 0.6–1.3).Discussion. Our results indicate absence of increased comorbid autoimmune disease prevalence in MS patients, as well as of increased risk of MS in patients suffering from other autoimmune disorders.
Trends in Cognitive Sciences, 2001
It was with great sadness that we received the news of the death of Francisco Varela, who passed ... more It was with great sadness that we received the news of the death of Francisco Varela, who passed away at his home in Paris, on 28 May, 2001.Varela was well known for his work in a number of scientific fields. He was the co-originator (with Humberto Maturana) of the theory of autopoiesis 1xSee all References1, and was one of the first proponents of the embodied or ‘enactive’ approach to cognition 2xVarela, F.J., Thompson, E., and Rosch, E. See all References2. He was known for his work on autonomous-network models of the immune system 3xSecond generation immune networks. Varela, F.J. and Coutinho, A. Immunol. Today. 1991; 12: 159–166Abstract | Full Text PDF | PubMed | Scopus (233)See all References3. In recent years, he provided groundbreaking studies using multiple-electrode recordings and mathematical analysis of large-scale neuronal integration during cognitive processes 4xThe brainweb: phase synchronization and large-scale integration. Varela, F.J. et al. Nat. Rev. Neurosci. 2001; 2: 229–239Crossref | PubMed | Scopus (2228)See all References4, showing for the first time that the human perception of meaningful complex forms is accompanied by phase-locked, synchronous oscillations in distinct brain regions 5xPerception's shadow: long-distance synchronization of human brain activity. Rodriguez, E. et al. Nature. 1998; 397: 430–433See all References5, and that nonlinear analysis can be used to predict seizures in epileptic patients prior to the onset of symptoms 6xEpileptic seizures can be anticipated by non-linear analysis. Martinerie, J. et al. Nat. Med. 1998; 4: 1173–1176Crossref | PubMed | Scopus (278)See all References6. He was also known for his original philosophical and empirical studies of the ‘neurophenomenology’ of human consciousness 7xNeurophenomenology: a methodological remedy for the hard problem. Varela, F.J. J. Conscious. Stud. 1996; 3: 330–350See all References, 8xThe specious present: a neurophenomenology of time consciousness. Varela, F.J. : 266–314See all References.Varela was born on 7 September, 1946 in Chile. As a child and teenager, he received a strong classical education from the German Lyceum in Santiago, which instilled in him a deep and lifelong appreciation of literature, art, philosophy and science. He received his M.Sc. (Licenciatura) in Biology in 1967 from the University of Chile, and his Ph.D. in Biology from Harvard University in 1970. Although he was offered positions at Harvard and other American universities, he chose to return to Chile in 1970 to help build a scientific research community there. Forced to flee with his family after the military coup of 1973, he taught at the University of Colorado Medical School in Denver until 1978, spent a year at the Brain Research Laboratories of the New York University Medical School in 1979, and then returned to Chile in 1980. In 1986 he moved to Paris, where he was based at the Institut des Neurosciences and at CREA (Centre de Recherche en Epistemologie Applique). In 1988 he was appointed to be Director of Research at CNRS, a position he held until his death.Varela's years in Paris, right up to the month of his passing, were remarkably full and productive by any standard. That he suffered from Hepatitus C from the early 1990s onwards, receiving a liver transplant in 1998, makes his life and work during this time truly inspiring.Varela died calm and at peace, in the loving embrace of his family. He leaves his wife, Amy Cohen Varela, and their son Gabriel; and his former wife Leonor, and their daughters Alejandra and Leonor, and son Javier. He will be deeply missed.
NeuroReport, 1999
IN a previous publication we showed that non-linear analysis can extract spatio-temporal changes ... more IN a previous publication we showed that non-linear analysis can extract spatio-temporal changes of brain electrical activity prior to epileptic seizures. Here we describe a new method to analyze this long-term nonstationarity in the EEG by a measure of dynamical similarity between different parts of the time series. We apply this method to the study of a group of patients with temporal lobe epilepsy recorded intracranially during transitions to seizure. We show that the method, which can be implemented on a personal computer, can track in real time spatio-temporal changes in brain dynamics several minutes prior to seizure. NeuroReport 10:2149±2155 # 1999 Lippincott Williams & Wilkins.
Journal of Clinical Neurophysiology, 2001
The study of dynamic changes in neural activity preceding epileptic seizure allows the characteri... more The study of dynamic changes in neural activity preceding epileptic seizure allows the characterization of a preictal state several minutes before seizure onset. This opens up new perspectives for studying the mechanisms of epileptogenesis as well as for possible therapeutic interventions, which represent a major breakthrough. In this review the authors present and discuss the results from their group in this domain using nonlinear analysis of brain signals, as well as the limitations of this topic and current questions.
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Papers by Francisco Gonzalez varela