Complexity Digest 2001.20

14-May-2001

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Content

  1. Human-Modified Ecosystems And Future Evolution, PNAS
    1. The Biotic Crisis And The Future Of Evolution, PNAS
    2. Closing Of The Indonesian Seaway As A Precursor To East African Aridification, Nature
    3. Hungry People Vs. Rare Wildlife: A Call For New Farming Methods, NYTimes
  2. Modern Men Trace Ancestry to African Migrants, Science
    1. African Origin of Modern Humans in East Asia: A Tale of 12,000 Y Chromosomes, Science
  3. Learning From The Spinal Cord, J. Physiol.
    1. Neural Prostheses, J. Physiol
  4. Evolving Ideas Of Brain Evolution, Nature
    1. Scalable Architecture In Mammalian Brains, Nature
    2. An Evolutionary Scaling Law For The Primate Visual System And Its Basis In Cortical Function
  5. Legs, Eyes, or Wings--Selectors and Signals Make the Difference, Science
    1. Control of a Genetic Regulatory Network by a Selector Gene, Science
  6. Gene Therapy Restores Vision To Dogs Blinded By Inherited Disease, Cornell Univ
    1. Gene Therapy Restores Vision In A Canine Model Of Childhood Blindness, Nature Genetics
  7. Care Complexity in the General Hospital: Results From a European Study, Psychosomatics
    1. COMPRI--An Instrument to Detect Patients With Complex Care Needs: Results From a European Study, Psychosomatics
    2. Risk Factors for Complex Care Needs in General Medical Inpatients, Psychosomatics
  8. Evolution And Scientific Literature: Towards A Decentralized Adaptive Web, Nature
    1. Web Archive Opens a New Realm of Research, NYTimes
  9. Physical Properties Determining Self-Organization of Motors and Microtubules, Science
  10. Wolbachia: A Tale of Sex and Survival, Science
  11. A Power Law For Cells, PNAS
  12. Weeding And Grooming Of Pathogens In Agriculture By Ants, Proc. Roy. Soc.
  13. Mutual Information Analysis Of The EEG In Patients With Alzheimer's, Clin Neurophysiol
  14. Computational Methods for Analyzing and Controlling Hybrid Systems, Caltech Control & Dyn Syst Seminar
  15. Cooperation, Adaptation and the Emergence of Leadership, arXiv
  16. Microplanning with Communicative Intentions, arXiv
  17. Neuropsychology Of Fear And Loathing, Nature Reviews Neuroscience
    1. Beware And Be Aware: Capture Of Spatial Attention By Fear-Related Stimuli In Neglect, Neuroreport
  18. New Imaging Tools Put the Art Back Into Science, Science
  19. When Space And Time Conspire, Nature Bookreport
    1. Complex Systems: Chaos and Beyond, Springer
  20. Links & Snippets
    1. Other Articles

  1. Human-Modified Ecosystems And Future Evolution, PNAS Next Article Bookmark and Share

    Abstract: Our global impact is finally receiving the scientific attention it deserves. The outcome will largely determine the future course of evolution. Human-modified ecosystems are shaped by our activities and their side effects. They share a common set of traits including simplified food webs, landscape homogenization, and high nutrient and energy inputs. Ecosystem simplification is the ecological hallmark of humanity and the reason for our evolutionary success. However, the side effects of our profligacy and poor resource practices are now so pervasive as to threaten our future no less than that of biological diversity itself. This article looks at human impact on ecosystems and the consequences for evolution. It concludes that future evolution will be shaped by our awareness of the global threats, our willingness to take action, and our ability to do so. Our ability is presently hampered by several factors, including the poor state of ecosystem and planetary knowledge, ignorance of human impact, lack of guidelines for sustainability, and a paucity of good policies, practices, and incentives for adopting those guidelines in daily life. (...)

    1. The Biotic Crisis And The Future Of Evolution, PNAS Next Article Bookmark and Share

      Abstract: The biotic crisis overtaking our planet is likely to precipitate a major extinction of species. That much is well known. Not so well known but probably more significant in the long term is that the crisis will surely disrupt and deplete certain basic processes of evolution, with consequences likely to persist for millions of years. Distinctive features of future evolution could include a homogenization of biotas, a proliferation of opportunistic species, a pest-and-weed ecology, an outburst of speciation among taxa that prosper in human-dominated ecosystems, a decline of biodisparity, an end to the speciation of large vertebrates, the depletion of "evolutionary powerhouses" in the tropics, and unpredictable emergent novelties. Despite this likelihood, we have only a rudimentary understanding of how we are altering the evolutionary future. As a result of our ignorance, conservation policies fail to reflect long-term evolutionary


    2. Closing Of The Indonesian Seaway As A Precursor To East African Aridification, Nature Next Article Bookmark and Share

      Excerpt: Global climate change around 3-4 Myr ago is thought to have influenced the evolution of hominids, via the aridification of Africa, and may have been the precursor to Pleistocene glaciation about 2.75 Myr ago. Most explanations of these climatic events involve changes in circulation of the North Atlantic Ocean due to the closing of the Isthmus of Panama. Here we suggest, instead, that closure of the Indonesian seaway 3-4 Myr ago could be responsible for these climate changes, in particular the aridification of Africa.


    3. Hungry People Vs. Rare Wildlife: A Call For New Farming Methods, NYTimes Next Article Bookmark and Share

      Excerpt: Almost half the world's 17,000 large nature preserves are being used for agriculture by poor undernourished communities that have no other options, according to a new study by an international network of scientists.

      Given the intensifying clash between hungry people and rare species, the best way to avert extinctions and also to sustain communities in those areas is to help farmers adopt cultivation methods that provide food while maintaining the habitat, the authors of the 241-page report wrote.


  2. Modern Men Trace Ancestry to African Migrants, Science Next Article Bookmark and Share

    Abstract: In work described on page 1151, geneticists found that characteristic DNA sequences called markers on the Y (male) chromosome in a huge sample of men in Asia and Oceania could be traced to forefathers who lived in Africa in the past 35,000 to 89,000 years. Two other groups studying Y chromosome markers have come to a similar conclusion. Together with a variety of studies showing that mitochondrial DNA is of recent African origins, anthropologists now have two strong lines of evidence in favor of the "Out of Africa" model, which says that the ancestors of living humans swept out of Africa in the past 200,000 years and replaced all indigenous people they encountered. Researchers point out, however, that it is still possible that some of our nuclear DNA came from archaic humans who were not part of the recent migration out of Africa. Thus, a competing theory called "multiregionalism," which holds that living humans are descended from several archaic Old World populations, including Neandertals, is not yet dead.

    1. African Origin of Modern Humans in East Asia: A Tale of 12,000 Y Chromosomes, Science Next Article Bookmark and Share

      Abstract: To test the hypotheses of modern human origin in East Asia, we sampled 12,127 male individuals from 163 populations and typed for three Y chromosome biallelic markers (YAP, M89, and M130). All the individuals carried a mutation at one of the three sites. These three mutations (YAP+, M89T, and M130T) coalesce to another mutation (M168T), which originated in Africa about 35,000 to 89,000 years ago. Therefore, the data do not support even a minimal in situ hominid contribution in the origin of anatomically modern humans in East Asia.

      • African Origin Of Modern Humans In East Asia: A Tale Of 12,000 Y Chromosomes, Yuehai Ke, Bing Su, Xiufeng Song, Daru Lu, Lifeng Chen, Hongyu Li, Chunjian Qi, Sangkot Marzuki, Ranjan Deka, Peter Underhill, Chunjie Xiao, Mark Shriver, Jeff Lell, Douglas Wallace, R Spencer Wells, Mark Seielstad, Peter Oefner, Dingliang Zhu, Jianzhong Jin, Wei Huang, Ranajit Chakraborty, Zhu Chen, Li Jin, Science 292: 1151-1153, 01/05/11

  3. Learning From The Spinal Cord, J. Physiol. Next Article Bookmark and Share

    Abstract: The graceful control of multiarticulated limbs equipped with slow, non-linear actuators (muscles) is a difficult problem for which robotic engineering affords no general solution. The vertebrate spinal cord provides an existence proof that such control is, indeed, possible. The biological solution is complex and incompletely known, despite a century of meticulous neurophysiological research, celebrated in part by this symposium. This is frustrating for those who would reanimate paralysed limbs either through promoting regeneration of the injured spinal cord or by functional electrical stimulation. The importance of and general role played by the spinal cord might be more easily recognized by analogy to marionette puppets, another system in which a brain (the puppeteer¹s) must cope with a large number of partially redundant actuators (strings) moving a mechanical linkage with complex intrinsic properties.

    1. Neural Prostheses, J. Physiol Next Article Bookmark and Share

      Excerpt: Assuming that neural regeneration after spinal cord injury (SCI) will eventually become a clinical reality, functional recovery will probably remain incomplete. Assistive devices will therefore continue to play an important role in rehabilitation. Neural prostheses (NPs) are assistive devices that restore functions lost as a result of neural damage. NPs electrically stimulate nerves and are either external or implanted devices. (…) Regarding implantable NPs, since 1963 over 40 000 have been implanted to restore hearing, bladder control and respiration.

      • Neural Prostheses, Arthur Prochazka, Vivian K. Mushahwar, Douglas B. Mccreery, J. Physiol. (Lond) 2001 May 15; 533(1): P. 99-109

  4. Evolving Ideas Of Brain Evolution, Nature Next Article Bookmark and Share

    Excerpts: The brains of mammals vary greatly in size, shape, internal organization and functional capabilities. The human brain is much larger than that of a mouse lemur, for example, and includes subdivisions and connections not found in a lemur.(…)

    compared the sizes of different brain parts to total brain size, by using multidimensional comparisons of brain proportions. They define what they call 'cerebrotypes' for the species they have examined.(…)

    cerebrotypes of tree shrews clearly do not group with those of primates (…)


    1. Scalable Architecture In Mammalian Brains, Nature Next Article Bookmark and Share

      Excerpts: Mammalian taxa can be well separated by cerebrotype, thus allowing (…) to test evolutionary relationships.

      Primate cerebrotypes have progressively shifted and neocortical volume fractions have become successively larger in lemurs and lorises, New World monkeys, Old World monkeys, and hominoids, lending support to the idea that primate brain architecture has been driven by directed selection pressure. At the same time, absolute brain size can vary over 100-fold within a taxon, while maintaining a relatively uniform cerebrotype. Brains therefore constitute a scalable architecture.


    2. An Evolutionary Scaling Law For The Primate Visual System And Its Basis In Cortical Function Next Article Bookmark and Share

      Excerpt: A hallmark of mammalian brain evolution is the disproportionate increase in neocortical size as compared with subcortical structures. Because primary visual cortex (V1) is the most thoroughly understood cortical region, the visual system provides an excellent model in which to investigate the evolutionary expansion of neocortex. I have compared the numbers of neurons in the visual thalamus (lateral geniculate nucleus; LGN) and area V1 across primate species. Here I find that the number of V1 neurons increases as the 3/2 power of the number of LGN neurons.


  5. Legs, Eyes, or Wings--Selectors and Signals Make the Difference, Science Next Article Bookmark and Share

    Abstract: How do the cells that give rise to structures such as the eye, wing, and leg in the developing fruit fly know where they are and what to do? As Affolter and Mann explain in their Perspective, it now seems that a selector transcription factor complex and a signaling effector protein interact together on a DNA enhancer sequence, switching on the appropriate set of target genes that then direct development of the appropriate structure.

    1. Control of a Genetic Regulatory Network by a Selector Gene, Science Next Article Bookmark and Share

      Abstract: The formation of many complex structures is controlled by a special class of transcription factors encoded by selector genes. It is shown that (…) selector protein complex for the Drosophila wing field, binds to and directly regulates the cis-regulatory elements of many individual target genes within the genetic regulatory network controlling wing development. Furthermore, combinations of binding sites for SCALLOPED and transcriptional effectors of signaling pathways are necessary and sufficient to specify wing-specific responses to different signaling pathways.


  6. Gene Therapy Restores Vision To Dogs Blinded By Inherited Disease, Cornell Univ Next Article Bookmark and Share

    Excerpt: Dogs blinded by an inherited retinal degenerative disease had their vision restored after treatment with genes from healthy dogs, marking the first successful gene therapy for blindness in a large animal. The treatment offers hope for humans with a similar condition. The achievement, with young dogs suffering from congenital stationary night blindness, which is similar to a childhood disease called Leber congenital amaurosis, is reported in the May 2001 issue of the journal Nature Genetics (...)

    In the gene therapy experiments, researchers used RPE65 genes that were cloned from dogs without the disease, together with a viral vector (recombinant adeno-associated virus, or AAV) to carry the normal dogs' DNA. They injected the combination into the subretinal space of the eyes of 3-month-old briard-beagle mix dogs that were known to have the defective RPE65 gene and had been blind since birth. Within six weeks, the treated eyes were producing the correct form of RPE65 protein. By three months, a series of tests (electroretinography, pupillometry and obstacle-avoidance tests in a dimly lit room) demonstrated that vision was restored to the treated eyes.


    1. Gene Therapy Restores Vision In A Canine Model Of Childhood Blindness, Nature Genetics Next Article Bookmark and Share

      Excerpt: Excerpt: Here we study one of the most clinically severe retinal degenerations, (...) LCA. LCA causes near total blindness in infancy and can result from mutations in RPE65 (...). A naturally occurring animal model, the RPE65-/- dog, suffers from early and severe visual impairment similar to that seen in human LCA. We used a recombinant adeno-associated virus (AAV) (...) to test the efficacy of gene therapy in this model. Our results indicate that visual function was restored in this large animal model of childhood blindness.


  7. Care Complexity in the General Hospital: Results From a European Study, Psychosomatics Next Article Bookmark and Share

    Abstract: There is increasing pressure to effectively treat patients with complex care needs from the moment of admission to the general hospital. In this study, the authors developed a measurement strategy for hospital-based care complexity. The authors' four-factor model describes the interrelations between complexity indicators, highlighting differences between length of stay (LOS), objective complexity (such as medications or consultations), complexity ratings by the nurse, and complexity ratings by the doctor. Their findings illustrate limitations in the use of LOS as a sole indicator for care complexity. The authors show how objective and subjective complexity indicators can be used for early and valid detection of patients needing interdisciplinary care.

    1. COMPRI--An Instrument to Detect Patients With Complex Care Needs: Results From a European Study, Psychosomatics Next Article Bookmark and Share

      Abstract: The authors developed a screening instrument to detect patients in need of complex care coordination at admission to a general hospital. On the basis of a series of risk factors for care complexity, the authors constructed a short, care complexity prediction instrument (COMPRI) and assessed its qualities. The COMPRI is an easily administered screening instrument that detects patients at risk for complex care needs for whom care coordination is indicated. COMPRI's predictive power exceeds all currently available case-mix instruments.


    2. Risk Factors for Complex Care Needs in General Medical Inpatients, Psychosomatics Next Article Bookmark and Share

      Abstract: The authors linked admission risk factors to a series of indicators for complex care delivery to enable detection of patients in need of care coordination at the moment of admission to the general hospital. The authors found 13 risk factors to be predictive of more than one indicator of care complexity. An admission risk screening procedure to detect patients in need of care coordination should focus on these risk factors and should include predictions made by doctors and nurses at admission and information collected from the patient and the medical chart.


  8. Evolution And Scientific Literature: Towards A Decentralized Adaptive Web, Nature Next Article Bookmark and Share

    Abstract: Perhaps it is time to apply a lesson from biological diversity (…). A key notion from complex systems theory is that of many simple processes, under selective pressures, being able to interact synergistically to produce desirable global behavior. (…) the scholarly communication system is a prime candidate.

    It would be in our best long-term interests to optimize our communication systems to support a variety of approaches while we evolve our understanding of the coming adaptive web and its impact on the communication of science.


    1. Web Archive Opens a New Realm of Research, NYTimes Next Article Bookmark and Share

      Excerpts: The archive may also help to ease a smoldering issue that few Western scientists like to discuss - that papers arriving from obscure or distant institutions instantly provoke increased skepticism from journal reviewers.(…)

      Without the archive, said Dr. Edward Witten, a physicist at the Institute for Advanced Study in Princeton, "it would have been virtually impossible for a previously unknown physicist at the out-of-the-way institution such as Motl was at, to contribute to a fast-evolving subject like the matrix model."


  9. Physical Properties Determining Self-Organization of Motors and Microtubules, Science Next Article Bookmark and Share

    Abstract: In eukaryotic cells, microtubules and their associated motor proteins can be organized into various large-scale patterns. Using a simplified experimental system combined with computer simulations, we examined how the concentrations and kinetic parameters of the motors contribute to their collective behavior. We observed self-organization of generic steady-state structures such as asters, vortices, and a network of interconnected poles. We identified parameter combinations that determine the generation of each of these structures. In general, this approach may become useful for correlating the morphogenetic phenomena (…) with the biophysical characteristics of its constituents.

  10. Wolbachia: A Tale of Sex and Survival, Science Next Article Bookmark and Share

    Abstract: By manipulating the sex lives of its hosts, the ubiquitous bacterium Wolbachia--perhaps the most common infectious bacterium on Earth--boosts its own reproductive success. Although no vertebrates (humans included) are known to carry Wolbachia, it is rampant in the invertebrate world, showing up in everything from fruit flies to shrimp, spiders, and even parasitic worms and turning the study of Wolbachia into a cottage industry among evolutionary biologists. Researchers suspect that Wolbachia may even provide clues to how species originate.

  11. A Power Law For Cells, PNAS Next Article Bookmark and Share

    Abstract: Darwin observed that multiple, lowly organized, rudimentary, or exaggerated structures show increased relative variability. However, the cellular basis for these laws has never been investigated. (…)

    Here we estimate variability in organ cell number for a variety of animals, plants, slime moulds, and volvocine algae. (…)We show that the power law for cell number variability can be explained by stochastic branching process models based on the properties of cell lineages. We also identify taxa in which the precision of developmental control appears to have evolved. We propose that the scale independence of relative cell number variability is maintained by natural selection.


  12. Weeding And Grooming Of Pathogens In Agriculture By Ants, Proc. Roy. Soc. Next Article Bookmark and Share

    Abstract: Fungus farming by ants pre-dates human agriculture by millions of years. Like human agricultural crops, the cultivars of fungus-growing ants are subject to devastating diseases, and thus successful farming depends on the protection of the gardens from pathogens. We establish that the rare ability of fungus-growing ants to culture fungus for food is possible because workers rapidly detect the presence of invading microbes and aggressively remove them from the garden. Ant workers remove invading fungi by both grooming their fungal cultivars and 'weeding' out infected garden substrate. In addition, workers are apparently able to discriminate between relatively benign and virulent pathogens.

  13. Mutual Information Analysis Of The EEG In Patients With Alzheimer's, Clin Neurophysiol Next Article Bookmark and Share

    Abstract: Objective: Mutual information provides a measure of both the linear and nonlinear statistical dependencies between two time series. Cross-mutual information (CMI) is used to quantify the information transmitted from one time series to another, while auto mutual information (AMI) in a time series estimates how much on average the value of the time series can be predicted from values of the time series at preceding points. The aim of this study is to assess information transmission between different cortical areas in Alzheimer's disease (AD) patients by estimating the average CMI between EEG electrodes.Methods: We recorded the EEG from 16 scale electrodes in 15 AD patients and 15 age-matched normal controls, and estimated the local, distant, and interhemispheric CMIs of the EEG in both groups. The rate of decrease (with increasing delay) of the AMI of the EEG was also measured to evaluate the complexity of the EEG in AD patients.Results: The local CMI in AD subjects was lower than that in normal controls, especially over frontal and antero-temporal regions. A prominent decrease in information transmission between distant electrodes in the right hemisphere and between corresponding interhemispheric electrodes was detected in the AD patients. In addition, the AMIs throughout the cerebrums of the AD patients decreased significantly more slowly with delay than did the AMIs of normal controls.Conclusions: These results are consistent with previous findings that suggest the association of EEG abnormalities in AD patients with functional impairment of information transmission in long cortico-cortical connections.

  14. Computational Methods for Analyzing and Controlling Hybrid Systems, Caltech Control & Dyn Syst Seminar Next Article Bookmark and Share

    Excerpts: Hybrid systems exhibit dynamics which evolve both continuously and in discrete jumps. Such behavior arises in many contexts, both in man-made systems and in nature. Continuous systems which have a phased operation, such as insect motion and biological cell growth and division,are well-suited to be modeled as hybrid systems, as are continuous systems which are controlled by a discrete logic, such as a chemical plant controlled with valves and pumps, or the autopilot modes for controlling an aircraft. (...)

  15. Cooperation, Adaptation and the Emergence of Leadership, arXiv Next Article Bookmark and Share

    Abstract: A generic property of biological, social and economical networks is their ability to evolve in time, creating and suppressing interactions. We approach this issue within the framework of an adaptive network of agents playing a Prisoner's Dilemma game, where each agent plays with its local neighbors, collects an aggregate payoff and imitates the strategy of its best neighbor. We allow the agents to adapt their local neighborhood according to their satisfaction level and the strategy played. We show that a steady state is reached, where the strategy and network configurations remain stationary. While the fraction of cooperative agents is high in these states, their average payoff is lower than the one attained by the defectors. The system self-organizes in such a way that the structure of links in the network is quite inhomogeneous, revealing the occurrence of cooperator "leaders" with a very high connectivity, which guarantee that global cooperation can be sustained in the whole network. Perturbing the leaders produces drastic changes of the network, leading to global dynamical cascades. These cascades induce a transient oscillation in the population of agents between the nearly all-defectors state and the all-cooperators outcome, before setting again in a state of high global cooperation.

  16. Microplanning with Communicative Intentions, arXiv Next Article Bookmark and Share

    Abstract: The process of microplanning encompasses a range of problems in Natural Language Generation (NLG), such as referring expression generation, lexical choice, and aggregation, problems in which a generator must bridge underlying domain-specific representations and general linguistic representations. In this paper, we describe a uniform approach to microplanning based on declarative representations of a generator's communicative intent. These representations describe the results of NLG: communicative intent associates the concrete linguistic structure planned by the generator with inferences that show how the meaning of that structure communicates needed information about some application domain in the current discourse context. Our approach, implemented in the SPUD (sentence planning using description) microplanner, uses the lexicalized tree-adjoining grammar formalism (LTAG) to connect structure to meaning and uses modal logic programming to connect meaning to context. At the same time, communicative intent representations provide a resource for the process of NLG. Using representations of communicative intent, a generator can augment the syntax, semantics and pragmatics of an incomplete sentence simultaneously, and can assess its progress on the various problems of microplanning incrementally. The declarative formulation of communicative intent translates into a well-defined methodology for designing grammatical and conceptual resources which the generator can use to achieve desired microplanning behavior in a specified domain.

  17. Neuropsychology Of Fear And Loathing, Nature Reviews Neuroscience Next Article Bookmark and Share

    Excerpt: Ideas about emotion in neuroscience and psychology have been dominated by a debate on whether emotion can be encompassed within a single unifying model. In neuroscience this approach is epitomised by the limbic system theory, and in psychology by dimensional models of emotion. (…) Evidence from humans consistent with this proposal has been obtained by showing that signals of fear and disgust may be processed by distinct neural substrates. The focus of this article is to review this research and its implications for theories of emotion.


    1. Beware And Be Aware: Capture Of Spatial Attention By Fear-Related Stimuli In Neglect, Neuroreport Next Article Bookmark and Share

      Abstract: Stimuli with threat significance may be privileged in summoning attention, allowing fast detection even outside the field of attention. We studied patients with unilateral neglect and visual extinction, who usually remain unaware of contralesional stimuli presented together with concurrent ipsilesional stimuli, to learn whether emotional stimuli might differentially be affected by contralesional extinction. Pictures of spiders or flowers with similar features were presented in right, left, or both fields. On bilateral trials, the patients detected emotional stimuli (spiders) on the left side much more often than neutral pictures (flowers). While mechanisms of spatial attention are impaired after parietal damage in neglect patients, intact visual pathways to the ventral temporal lobe and amygdala might still mediate distinct mechanisms of emotional attention.


  18. New Imaging Tools Put the Art Back Into Science, Science Next Article Bookmark and Share

    Abstract: Across virtually every discipline, computer-aided tools and new technologies, often developed for the art and entertainment industries, are becoming common on the lab bench--and raising complex questions about the role of aesthetics in science and the fine line between enhancement and falsification. Next month the Massachusetts Institute of Technology will bring together researchers, publishers, and imagemakers to discuss the promises and pitfalls of imaging in science. The National Science Foundation (NSF), a primary sponsor of the conference,stands ready to provide additional funding for imaging projects, promises NSF director Rita Colwell.

  19. When Space And Time Conspire, Nature Bookreport Next Article Bookmark and Share

    The understanding of complex systems is itself a complex process: It is too easy to detect patterns at one level (especially if the patterns are represented with esthetically stimulating graphics) and then to generalize what one has learned to assume that this pattern applies to the rest of complex systems as well. Mike Shlesinger, a veteran of chaos theory himself, apparently liked the pictures that you can produce with coupled map models so that he assumed that the book was about spatio-temporal chaos. This restricted (and admittedly not so biologically relevant) class of models is discussed in chapter 3 of the book. He somehow missed that the more important message of the book was not a recipe to produce pretty pictures but to offer a serious contribution to a computational approach to complex systems with a special focus on biological networks including the brain.

    The general class of models that the authors propose (GCM = "globally coupled maps") is general enough to allow accurate implementation of, say, brain models with any desired degree of realism. One can appreciate how powerful GCM's are by recognizing that they also include network models of the "Small World" category that have been widely discussed recently. As a contrast, cellular automata or coupled map models do not share this property.

    In terms of modeling strategy we are convinced that this book will have a fundamental impact on the new, systems-oriented biology. Demonstrating how one can build mathematical models with the ideas of mapping states into each other as they evolve in time can have tremendous heuristic values and frees theoretical bio-scientists from squeezing their creative ideas into the language of stocks, flows and rates. This discrete time approach also encourages the modeler to carefully analyze the relevant time-scales that are relevant in the modeled system.

    Excerpt: Kaneko and Tsuda also seek ways of measuring the complexity of their systems. They define an information flow and entropy derived from the number and size of synchronized spatial clusters. And they make analogies between information storage, flow and processing in the brain and the many possible states of the coupled map lattice (…). Spatiotemporal dynamics of nonlinear coupled map lattices is a new field of study, and much remains to be done to determine whether it will be a fruitful approach to biological problems.


    1. Complex Systems: Chaos and Beyond, Springer Next Article Bookmark and Share

  20. Links & Snippets Next Article Bookmark and Share

    1. What's New In Classical Music? Not Much, Anthony Tommasini, NYTimes 01/04/29
    2. Who or what is AARON? And how does it work?, Kurzweil AI, 2001
    3. Game Theory: Tracking an Elusive Film Game Online, Charles Herold, NYTimes, 01/05/03
    4. Formula One Sets Off A Debate As It Embraces High-Tech Again,Brad Spurgeon,NYTimes 01/04/29
    5. Adult Stem Cells May Adapt For Body's Benefit, David Perlman, The San Francisco Chronicle, 5/4/01
    6. Where There's Smoke, There's Not Always Ozone, 5/03/01, Peter N. Spotts, The Christian Science Monitor


    1. Other Articles Bookmark and Share


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