Scielo RSS <![CDATA[Biological Research]]> https://scielo.conicyt.cl/rss.php?pid=0716-976020030001&lang=en vol. 36 num. 1 lang. en <![CDATA[SciELO Logo]]> https://scielo.conicyt.cl/img/en/fbpelogp.gif https://scielo.conicyt.cl <![CDATA[A TRIBUTE TO FRANCISCO VARELA]]> https://scielo.conicyt.cl/scielo.php?script=sci_arttext&pid=S0716-97602003000100001&lng=en&nrm=iso&tlng=en <![CDATA[Francisco Varela (1946-2001):: Filling the mind - brain gap: A life adventure]]> https://scielo.conicyt.cl/scielo.php?script=sci_arttext&pid=S0716-97602003000100002&lng=en&nrm=iso&tlng=en One of the most eminent neuroscientists recently passed away in Paris. Professor Francisco Varela was a scholar that approached science with a remarkably broad and integrative perspective, deeply contributing to a diversity of fields, from mathematics to epistemology, from immunology to neuroscience. He was strongly influenced by Buddhism and actively participated in unraveling the relationship between science and spirituality. This article introduces a special edition of Biological Research dedicated to the memory of this great man. It contains a collection of valuable contributions by various authors who collaborated with Varela at different moments of his outstanding scientific career. Their articles cover most of the fields in which he made contributions. <![CDATA[For Francisco Varela: Explorer of the phenomenal world]]> https://scielo.conicyt.cl/scielo.php?script=sci_arttext&pid=S0716-97602003000100003&lng=en&nrm=iso&tlng=en One of the most eminent neuroscientists recently passed away in Paris. Professor Francisco Varela was a scholar that approached science with a remarkably broad and integrative perspective, deeply contributing to a diversity of fields, from mathematics to epistemology, from immunology to neuroscience. He was strongly influenced by Buddhism and actively participated in unraveling the relationship between science and spirituality. This article introduces a special edition of Biological Research dedicated to the memory of this great man. It contains a collection of valuable contributions by various authors who collaborated with Varela at different moments of his outstanding scientific career. Their articles cover most of the fields in which he made contributions. <![CDATA[A walk with Francisco Varela from first- to second-generation networks: In search of the structure, dynamics and metadynamics of an organism-centered immune system]]> https://scielo.conicyt.cl/scielo.php?script=sci_arttext&pid=S0716-97602003000100004&lng=en&nrm=iso&tlng=en One of the most eminent neuroscientists recently passed away in Paris. Professor Francisco Varela was a scholar that approached science with a remarkably broad and integrative perspective, deeply contributing to a diversity of fields, from mathematics to epistemology, from immunology to neuroscience. He was strongly influenced by Buddhism and actively participated in unraveling the relationship between science and spirituality. This article introduces a special edition of Biological Research dedicated to the memory of this great man. It contains a collection of valuable contributions by various authors who collaborated with Varela at different moments of his outstanding scientific career. Their articles cover most of the fields in which he made contributions. <![CDATA[From autopoiesis to neurophenomenology: Francisco Varela's exploration of the biophysics of being]]> https://scielo.conicyt.cl/scielo.php?script=sci_arttext&pid=S0716-97602003000100005&lng=en&nrm=iso&tlng=en This paper reviews in detail Francisco Varela's work on subjectivity and consciousness in the biological sciences. His original approach to this "hard problem" presents a subjectivity that is radically intertwined with its biological and physical roots. It must be understood within the framework of his theory of a concrete, embodied dynamics, grounded in his general theory of autonomous systems. Through concepts and paradigms such as biological autonomy, embodiment and neurophenomenology, the article explores the multiple levels of circular causality assumed by Varela to play a fundamental role in the emergence of human experience. The concept of biological autonomy provides the necessary and sufficient conditions for characterizing biological life and identity as an emergent and circular self-producing process. Embodiment provides a systemic and dynamical framework for understanding how a cognitive -a mind- can arise in an organism in the midst of its operational cycles of internal regulation and ongoing sensorimotor coupling. Global subjective properties can emerge at different levels from the interactions of components and can reciprocally constrain local processes through an ongoing, recursive morphodynamics. Neurophenomenology is a supplementary step in the study of consciousness. Through a rigorous method, it advocates the careful examination of experience with first-person methodologies. It attempts to create heuristic mutual constraints between biophysical data and data produced by accounts of subjective experience. The aim is to explicitly ground the active and disciplined insight the subject has about his/her experience in a biophysical emergent process. Finally, we discuss Varela's essential contribution to our understanding of the generation of consciousness in the framework of what we call his "biophysics of being." <![CDATA[Disentangling the dynamic core: a research program for a neurodynamics at the large-scale]]> https://scielo.conicyt.cl/scielo.php?script=sci_arttext&pid=S0716-97602003000100006&lng=en&nrm=iso&tlng=en My purpose in this paper is to sketch a research direction based on Francisco Varela's pioneering work in neurodynamics (see also Rudrauf et al. 2003, in this issue). Very early on he argued that the internal coherence of every mental-cognitive state lies in the global self-organization of the brain activities at the large-scale, constituting a fundamental pole of integration called here a "dynamic core". Recent neuroimaging evidence appears to broadly support this hypothesis and suggests that a global brain dynamics emerges at the large scale level from the cooperative interactions among widely distributed neuronal populations. Despite a growing body of evidence supporting this view, our understanding of these large-scale brain processes remains hampered by the lack of a theoretical language for expressing these complex behaviors in dynamical terms. In this paper, I propose a rough cartography of a comprehensive approach that offers a conceptual and mathematical framework to analyze spatio-temporal large-scale brain phenomena. I emphasize how these nonlinear methods can be applied, what property might be inferred from neuronal signals, and where one might productively proceed for the future. This paper is dedicated, with respect and affection, to the memory of Francisco Varela. <![CDATA[Long distance communication in the human brain: timing constraints for inter-hemispheric synchrony and the origin of brain lateralization]]> https://scielo.conicyt.cl/scielo.php?script=sci_arttext&pid=S0716-97602003000100007&lng=en&nrm=iso&tlng=en Analysis of corpus callosum fiber composition reveals that inter-hemispheric transmission time may put constraints on the development of inter-hemispheric synchronic ensembles, especially in species with large brains like humans. In order to overcome this limitation, a subset of large-diameter callosal fibers are specialized for fast inter-hemispheric transmission, particularly in large-brained species. Nevertheless, the constraints on fast inter-hemispheric communication in large-brained species can somehow contribute to the development of ipsilateral, intrahemispheric networks, which might promote the development of brain lateralization. <![CDATA[An "enactive" approach to integrative and comparative biology: Thoughts on the table]]> https://scielo.conicyt.cl/scielo.php?script=sci_arttext&pid=S0716-97602003000100008&lng=en&nrm=iso&tlng=en We discuss the concept of Enaction as originally proposed by Varela. We attempt to exemplify through two specific topics, sensory ecology and behavior, as well as physiological and behavioral ecology, on which the enactive approach is based. We argue that sensory physiology allows us to explore the biological and cognitive meaning of animal 'private' sensory channels, beyond the scope of our own sensory capacity. Furthermore, after analyzing the interplay between factors that may impose limits upon an animal's use of time and energy, we call for a program of research in integrative and comparative biology that simultaneously considers evolutionary ecology (including physiological and behavioral ecology) and neurobiology (including cognitive mechanisms as well structural design). We believe that this approach represents a shift in scientific attitude among biologists concerning the place of biological and ecological topics in studies of integrative and comparative biology and biological diversity and vice versa <![CDATA[Morphodynamical enaction: the case of color]]> https://scielo.conicyt.cl/scielo.php?script=sci_arttext&pid=S0716-97602003000100009&lng=en&nrm=iso&tlng=en We discuss the concept of Enaction as originally proposed by Varela. We attempt to exemplify through two specific topics, sensory ecology and behavior, as well as physiological and behavioral ecology, on which the enactive approach is based. We argue that sensory physiology allows us to explore the biological and cognitive meaning of animal 'private' sensory channels, beyond the scope of our own sensory capacity. Furthermore, after analyzing the interplay between factors that may impose limits upon an animal's use of time and energy, we call for a program of research in integrative and comparative biology that simultaneously considers evolutionary ecology (including physiological and behavioral ecology) and neurobiology (including cognitive mechanisms as well structural design). We believe that this approach represents a shift in scientific attitude among biologists concerning the place of biological and ecological topics in studies of integrative and comparative biology and biological diversity and vice versa <![CDATA[Evolution of probability measures by cellular automata on algebraic topological Markov chains]]> https://scielo.conicyt.cl/scielo.php?script=sci_arttext&pid=S0716-97602003000100010&lng=en&nrm=iso&tlng=en In this paper we review some recent results on the evolution of probability measures under cellular automata acting on a fullshift. In particular we discuss the crucial role of the attractiveness of maximal measures. We enlarge the context of the results of a previous study of topological Markov chains that are Abelian groups; the shift map is an automorphism of this group. This is carried out by studying the dynamics of Markov measures by a particular additive cellular automata. Many of these topics were within the focus of Francisco Varela's mathematical interests. <![CDATA[Color vision in the comb frequency domain]]> https://scielo.conicyt.cl/scielo.php?script=sci_arttext&pid=S0716-97602003000100011&lng=en&nrm=iso&tlng=en In 1982, Horace Barlow considered the question of human trichromacy in the context of information theory: according to the Sampling Theorem, three types of receptors covering the visible spectrum (400- -700 nm) might be sufficient to reconstruct the color signal. Although Barlow was led to reject the direct application of the Sampling Theorem to explain color dimensionality, the theoretical framework offers a fresh point of view for analyzing the color system in conjunction with the physical characteristics of natural color signals. This review aims to illustrate that if the strict mathematical reconstruction (as implied by the Sampling Theorem) is replaced by a pragmatic approximation of color signals, then trichromacy, with its subsequent opponent-color process, could be regarded as an optimization of color constancy abilities in the spectral environment of primates. Higher dimension systems (tetrachromacy) found in other species can also serve the purpose of color constancy optimization in environments where color signals exhibit a finer spectral structure.