Scielo RSS <![CDATA[Biological Research]]> https://scielo.conicyt.cl/rss.php?pid=0716-976020070005&lang=en vol. 40 num. 4 lang. en <![CDATA[SciELO Logo]]> https://scielo.conicyt.cl/img/en/fbpelogp.gif https://scielo.conicyt.cl <![CDATA[<b>Department of International Relations of CONICYT</b>]]> https://scielo.conicyt.cl/scielo.php?script=sci_arttext&pid=S0716-97602007000500001&lng=en&nrm=iso&tlng=en <![CDATA[<b>Networks in Cognitive Systems and Biomedicine</b>: <b>Cerebral Processes, Models and Mathematical Tools Design</b>]]> https://scielo.conicyt.cl/scielo.php?script=sci_arttext&pid=S0716-97602007000500002&lng=en&nrm=iso&tlng=en Convergence of clinical, empirical, methodological and theoretical approaches aimed at understanding the relation between brain function and cognition, is by now standard in most if not all academic programs in the area of Cognitive Science. This confederation of disciplines is one of the liveliest domains of inquiry and discussion into some of the most fundamental -and historically resilient- questions human beings have posed themselves. The contributions gathered in this special issue of Biological Research, directly inspired by the ongoing work at the Instituto de Sistemas Complejos de Valparaiso and the December 2006 CONICYT-INSERM-SFI workshop "Networks in Cognitive Systems / Trends and Challenge in Biomedicine: From Cerebral Process to Mathematical Tools Design", Chile, represent an explicit invitation to the reader to dive deeper into this fascinating terrain <![CDATA[<b>Diffusion Signal in Magnetic Resonance Imaging</b>: <b>Origin and Interpretation in Neurosciences</b>]]> https://scielo.conicyt.cl/scielo.php?script=sci_arttext&pid=S0716-97602007000500003&lng=en&nrm=iso&tlng=en Diffusion Magnetic Resonance Imaging provides images of unquestionable diagnostic value. It is commonly used in the assessment of stroke and in white matter fiber tracking, among other applications. The diffusion coefficient has been shown to depend on cell concentration, membrane permeability, and cell orientation in the case of white matter or muscle fiber tracking; yet a clear relation between diffusion measurements and known physiological parameters is not established. The aim of this paper is to review hypotheses and actual knowledge on diffusion signal origin to provide assistance in the interpretation of diffusion MR images. Focus will be set on brain images, as most common applications of diffusion MRI are found in neuroradiology. Diffusion signal does not come from two intra- or extracellular compartments, as was first assumed. Restriction of water displacement due to membranes, hindrance in the extracellular space, and tissue heterogeneity are important factors. Unanswered questions remain on how to deal with tissue heterogeneity, and how to retrieve parameters less troublesome to work with from biological and clinical points of view. Diffusion quantification should be done with care, as many variables can lead to variation in measurements <![CDATA[<b>BrainTV</b>: <b>a novel approach for online mapping of human brain functions</b>]]> https://scielo.conicyt.cl/scielo.php?script=sci_arttext&pid=S0716-97602007000500004&lng=en&nrm=iso&tlng=en Our understanding of the brain's functional organisation has greatly benefited from occasional exploratory sessions during electrophysiological studies, trying various manipulations of an animal's environment to trigger responses in particular neurons. Famous examples of such exploration have unveiled various unexpected response properties, such as those of mirror neurons. This approach, which relies on the possibility to test online the reactivity of precise neural populations has no equivalent so far in humans. The present study proposes and applies a radically novel framework for mapping human brain functions in ecological situations based on a combination of a) exploratory sessions, using real-time electrophysiology to formulate hypotheses about the functional role of precise cortical regions and b) controlled experimental protocols specifically adapted to test these hypotheses. Using this two-stage approach with an epileptic patient candidate for surgery and implanted with intracerebral electrodes, we were able to precisely map high-level auditory functions in the patients' superior temporal lobe. We propose that this procedure constitutes at the least a useful complement of electrical cortical stimulations to map eloquent brain areas in epileptic patients before their surgery, but also a path of discovery for human functional brain mapping <![CDATA[<b>Classification methods for ongoing EEG and MEG signals</b>]]> https://scielo.conicyt.cl/scielo.php?script=sci_arttext&pid=S0716-97602007000500005&lng=en&nrm=iso&tlng=en Classification algorithms help predict the qualitative properties of a subject's mental state by extracting useful information from the highly multivariate non-invasive recordings of his brain activity. In particular, applying them to Magneto-encephalography (MEG) and electro-encephalography (EEG) is a challenging and promising task with prominent practical applications to e.g. Brain Computer Interface (BCI). In this paper, we first review the principles of the major classification techniques and discuss their application to MEG and EEG data classification. Next, we investigate the behavior of classification methods using real data recorded during a MEG visuomotor experiment. In particular, we study the influence of the classification algorithm, of the quantitative functional variables used in this classifier, and of the validation method. In addition, our findings suggest that by investigating the distribution of classifier coefficients, it is possible to infer knowledge and construct functional interpretations of the underlying neural mechanisms of the performed tasks. Finally, the promising results reported here (up to 97% classification accuracy on 1-second time windows) reflect the considerable potential of MEG for the continuous classification of mental states <![CDATA[<b>What we see is how we are</b>: <b>New paradigms in visual research</b>]]> https://scielo.conicyt.cl/scielo.php?script=sci_arttext&pid=S0716-97602007000500006&lng=en&nrm=iso&tlng=en As most sensory modalities, the visual system needs to deal with very fast changes in the environment. Instead of processing all sensory stimuli, the brain is able to construct a perceptual experience by combining selected sensory input with an ongoing internal activity. Thus, the study of visual perception needs to be approached by examining not only the physical properties of stimuli, but also the brain's ongoing dynamical states onto which these perturbations are imposed. At least three different models account for this internal dynamics. One model is based on cardinal cells where the activity of few cells by itself constitutes the neuronal correlate of perception, while a second model is based on a population coding that states that the neuronal correlate of perception requires distributed activity throughout many areas of the brain. A third proposition, known as the temporal correlation hypothesis states that the distributed neuronal populations that correlate with perception, are also defined by synchronization of the activity on a millisecond time scale. This would serve to encode contextual information by defining relations between the features of visual objects. If temporal properties of neural activity are important to establish the neural mechanisms of perception, then the study of appropriate dynamical stimuli should be instrumental to determine how these systems operate. The use of natural stimuli and natural behaviors such as free viewing, which features fast changes of internal brain states as seen by motor markers, is proposed as a new experimental paradigm to study visual perception <![CDATA[<b>Complex, multifocal, individual-specific attention-related cortical functional circuits</b>]]> https://scielo.conicyt.cl/scielo.php?script=sci_arttext&pid=S0716-97602007000500007&lng=en&nrm=iso&tlng=en Recent studies focusing on the analysis of individual patterns of non-sensory-motor CNS activity may significantly alter our view of CNS functional mapping. We have recently provided evidence for highly variable attention-related Slow Potential (SP) generating cortical areas across individuals (Basile et al., 2003, 2006). In this work, we present new evidence, searching for other physiological indexes of attention by a new use of a well established method, for individual-specific sets of cortical areas active during expecting attention. We applied latency corrected peak averaging to oscillatory bursts, from 124-channel EEG recordings, and modeled their generators by current density reconstruction. We first computed event-related total power, and averaging was based on individual patterns of narrow task-induced band-power. This method is sensitive to activity out of synchrony with stimuli, and may detect task-related changes missed by regular Event-Related Potential (ERP) averaging. We additionally analyzed overall inter-electrode phase-coherence. The main results were (1) the detection of two bands of attention-induced beta range oscillations (around 25 and 21 Hz), whose scalp topography and current density cortical distribution were complex multi-focal, and highly variable across subjects, including prefrontal and posterior cortical areas. Most important, however, was the observation that (2) the generators of task-induced oscillations are largely the same individual-specific sets of cortical areas active during the resting, baseline state. We concluded that attention-related electrical cortical activity is highly individual-specific (significantly different from sensory-related visual evoked potentials or delta and theta induced band-power), and to a great extent already established during mere wakefulness. We discuss the critical implications of those results, in combination with other studies presenting individual data, to functional mapping: the need to abandon group averaging of task-related cortical activity and to revise studies on group averaged data, since the assumption of universal function to each cortical area appears deeply challenged. Clinical implications regard the interpretation of focal lesion consequences, functional reorganization, and neurosurgical planning <![CDATA[<b>Sleep in brain development</b>]]> https://scielo.conicyt.cl/scielo.php?script=sci_arttext&pid=S0716-97602007000500008&lng=en&nrm=iso&tlng=en With the discovery of rapid eye movement (REM) sleep, sleep was no longer considered a homogeneous state of passive rest for the brain. On the contrary, sleep, and especially REM sleep, appeared as an active condition of intense cerebral activity. The fact that we get large amounts of sleep in early life suggested that sleep may play a role in brain maturation. This idea has been investigated for many years through a large number of animal and human studies, but evidence remains fragmented. The hypothesis proposed was that REM sleep would provide an endogenous source of activation, possibly critical for structural maturation of the central nervous system. This proposal led to a series of experiments looking at the role of REM sleep in brain development. In particular, the influence of sleep in developing the visual system has been highlighted. More recently, non-REM (NREM) sleep state has become a major focus of attention. The current data underscore the importance of both REM sleep and NREM sleep states in normal synaptic development and lend support to their functional roles in brain maturation. Both sleep states appear to be important for neuronal development, but the corresponding contribution is likely to be different <![CDATA[<b>Dynamical Complexity in Cognitive Neural Networks</b>]]> https://scielo.conicyt.cl/scielo.php?script=sci_arttext&pid=S0716-97602007000500009&lng=en&nrm=iso&tlng=en In the last twenty years an important effort in brain sciences, especially in cognitive science, has been the development of mathematical tool that can deal with the complexity of extensive recordings corresponding to the neuronal activity obtained from hundreds of neurons. We discuss here along with some historical issues, advantages and limitations of Artificial Neural Networks (ANN) that can help to understand how simple brain circuits work and whether ANN can be helpful to understand brain neural complexity <![CDATA[<b>Dynamic Causal Models and Autopoietic Systems</b>]]> https://scielo.conicyt.cl/scielo.php?script=sci_arttext&pid=S0716-97602007000500010&lng=en&nrm=iso&tlng=en Dynamic Causal Modelling (DCM) and the theory of autopoietic systems are two important conceptual frameworks. In this review, we suggest that they can be combined to answer important questions about self-organising systems like the brain. DCM has been developed recently by the neuroimaging community to explain, using biophysical models, the non-invasive brain imaging data are caused by neural processes. It allows one to ask mechanistic questions about the implementation of cerebral processes. In DCM the parameters of biophysical models are estimated from measured data and the evidence for each model is evaluated. This enables one to test different functional hypotheses (i.e., models) for a given data set. Autopoiesis and related formal theories of biological systems as autonomous machines represent a body of concepts with many successful applications. However, autopoiesis has remained largely theoretical and has not penetrated the empiricism of cognitive neuroscience. In this review, we try to show the connections that exist between DCM and autopoiesis. In particular, we propose a simple modification to standard formulations of DCM that includes autonomous processes. The idea is to exploit the machinery of the system identification of DCMs in neuroimaging to test the face validity of the autopoietic theory applied to neural subsystems. We illustrate the theoretical concepts and their implications for interpreting electroencephalographic signals acquired during amygdala stimulation in an epileptic patient. The results suggest that DCM represents a relevant biophysical approach to brain functional organisation, with a potential that is yet to be fully evaluated <![CDATA[<b>Programming Paradigms and Mind Metaphors</b>: <b>Convergence and Cross-fertilization in the Study of Cognition</b>]]> https://scielo.conicyt.cl/scielo.php?script=sci_arttext&pid=S0716-97602007000500011&lng=en&nrm=iso&tlng=en This paper describes a notable convergence between biological organization and programming language abstractions. Our aim is to explore possibilities of cross-fertilization, at both conceptual and empirical levels, towards the understanding of what cognition and cognitive systems might be <![CDATA[<b>A critical assessment of the consciousness by synchrony hypothesis</b>]]> https://scielo.conicyt.cl/scielo.php?script=sci_arttext&pid=S0716-97602007000500012&lng=en&nrm=iso&tlng=en This paper describes a notable convergence between biological organization and programming language abstractions. Our aim is to explore possibilities of cross-fertilization, at both conceptual and empirical levels, towards the understanding of what cognition and cognitive systems might be <![CDATA[<b>Right but basically wrong</b>: <b>Comments on Canales et al. 'A <i>Critical Assessment of the Consciousness by Synchrony Hypothesis'</i></b>]]> https://scielo.conicyt.cl/scielo.php?script=sci_arttext&pid=S0716-97602007000500013&lng=en&nrm=iso&tlng=en This paper describes a notable convergence between biological organization and programming language abstractions. Our aim is to explore possibilities of cross-fertilization, at both conceptual and empirical levels, towards the understanding of what cognition and cognitive systems might be <![CDATA[<b>The debate about death</b>: <b>an imperishable discussion?</b>]]> https://scielo.conicyt.cl/scielo.php?script=sci_arttext&pid=S0716-97602007000500014&lng=en&nrm=iso&tlng=en In this concise review we discuss some of the complex edges of the concept of death that arose after the notorious advances in science and medicine over the last 50 years, in which the classical cardio-pulmonary criteria have led to the neurological criteria of death. New complicated questions like the definition of death and the operational criteria for diagnosing it have arisen and we think that they are far from being adequately and satisfactorily solved. A number of important issues -like the reliability and differences between cardio-pulmonary versus brain based criteria of death, if death is an event or a process, the meaning of integration and irreversibility- have not yet received sufficient attention. Here we have approached the death problem from two (biological) complex system perspectives: the organism level and the cellular-molecular level. We also discuss issues from a third systemic approach, that is, the entire society, thus involving legal, religious, bioethical and political aspects of death. Our aim is to integrate new perspectives in order to promote further discussion on these critical yet frequently neglected issues <![CDATA[<b>The vitality of death discussions</b>: <b>Comments on Bacigalupo et al., <i>'The debate about death: an imperishable discussion?'</i></b>]]> https://scielo.conicyt.cl/scielo.php?script=sci_arttext&pid=S0716-97602007000500015&lng=en&nrm=iso&tlng=en In this concise review we discuss some of the complex edges of the concept of death that arose after the notorious advances in science and medicine over the last 50 years, in which the classical cardio-pulmonary criteria have led to the neurological criteria of death. New complicated questions like the definition of death and the operational criteria for diagnosing it have arisen and we think that they are far from being adequately and satisfactorily solved. A number of important issues -like the reliability and differences between cardio-pulmonary versus brain based criteria of death, if death is an event or a process, the meaning of integration and irreversibility- have not yet received sufficient attention. Here we have approached the death problem from two (biological) complex system perspectives: the organism level and the cellular-molecular level. We also discuss issues from a third systemic approach, that is, the entire society, thus involving legal, religious, bioethical and political aspects of death. Our aim is to integrate new perspectives in order to promote further discussion on these critical yet frequently neglected issues