Physics
Scientific paper
Jan 2008
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2008njph...10a5002b&link_type=abstract
New Journal of Physics, Volume 10, Issue 1, pp. 015002 (2008).
Physics
2
Scientific paper
Among the organs of our body, the function of heart and brain are unique in that their operation emerges from the collective dynamics of millions of strongly interacting cells well organized in their geometrical structure and connectivity. In the heart muscle the propagation of a nonlinear wave pulse, the cardiac action potential, controls the contraction. Usually the propagation is well-organized both in space and time and the heart functions as an efficient biological pump. Instabilities triggered by diseased tissue but also by dynamical heterogeneities, may, however, induce cardiac arrhythmia and fibrillation, where the pacemaker looses control to dynamically generated, high-frequency self-excitation of the muscle. In this state the coherence of contraction is lost and may lead within minutes to death.
The appearance of arrhythmias can be associated with topological singularities, the so called spiral or scroll waves, and how the occurrence of this malfunctioning pattern-formation process can be understood is a dominant subject of current research. This is all the more important as cardiac arrhythmias and fibrillation are the main cause of premature death in the developed world. Similarly, in the brain the propagation of a nonlinear wave pulse, namely the neural action potential, is at the basis of the computational and memory power of the brain, i.e. what determines the workings of our 'minds'. Here, however, due to the high degree of interconnectivity and topological complexity of the neuronal network, the coordinated activity of millions of interacting nerve cells is more complex, although the basic principles of action potential generation at the level of each cell are quite similar. The currently emerging field of network dynamical systems is largely driven by the mathematical challenge and the steady stream of novel dynamical phenomena that results from the interplay of local nonlinear dynamics and complex network structure in models of biological neuronal networks. The brain, however, would be only incompletely understood when just viewed as a complex dynamical system. Understanding the operation of the mind also requires describing and analyzing its emergent information processing functions. To achieve this, many aspects of neural computation have been successfully formulated as problems of statistical inference and optimal decision making, phrasing them in the mathematical language of statistical physics. Both subjects, heart and mind, are thus united through the similarity of current models for the emergence of collective capabilities. They rely conceptually and technically essentially on the paradigms and tools of statistical physics and nonlinear dynamics. In general, none of the functions and processes of the heart or mind can be appropriately understood without a thorough analysis of the collective dynamics of the underlying biological networks and nonlinear media. Approaching any of these problems with necessity requires a coordinated interdisciplinary effort utilizing approaches from nonlinear dynamics and pattern formation to genetics, molecular biology and biological imaging. Because of their thorough understanding and advanced methodology for dissecting nonlinear and collective phenomena, physicists are playing an increasingly important role in unravelling the dynamical principles governing the operation as well as the malfunction of heart and mind.
Current research in the physics of heart and mind spans a wide spectrum of theoretical, experimental, and computational approaches. Many are guided by the aim for a transparent picture of systems function that links the biophysics of individual cells to the operation of the entire organ or information processing system. Theoretical work thus often centres on the construction and analysis of models that contain sufficient biophysical detail to represent reliably all cellular mechanisms of importance, but that are still theoretically sufficiently transparent and tractable to support a comprehensive analysis of functional performance at the systems level. Analogously, experimental work increasingly probes the system dynamics simultaneously at multiple levels from cell to whole organ. Here an invaluable contribution of physics to the experimental characterization of large scale activity in cardiac and neuronal tissues is the currently emerging high level of quantitative precision and control. Long-term high precision recording of large scale activity patterns of neural and cardiac tissues increasingly supports the formulation of quantitative phenomenological theories of complex dynamical states as well the realization of algorithms for manipulating and controlling them. Both quantitative phenomenology and control are not only essential for bridging theory and experiment in complex systems; they are also indispensable for turning scientific insight into diagnostic progress and improved treatment for the affected heart and mind.
The present Focus Issue in New Journal of Physics reflects well the richness and excitement of this currently rapidly evolving field. It combines theoretical and experimental approaches and covers analyses ranging from the organ level over investigations of model systems to the biophysics of individual cells. The articles below represent the first contributions to this collection and further additions will appear in the near future.
Focus on Heart and Mind Contents
'Heart' contributions
The formation of labyrinths, spots and stripe patterns in a biochemical approach to cardiovascular calcification A Yochelis, Y Tintut, L L Demer and A Garfinkel
Coupled iterated map models of action potential dynamics in a one-dimensional cable of cardiac cells Shihong Wang, Yuanfang Xie and Zhilin Qu
Spiral wave drift and complex-oscillatory spiral waves caused by heterogeneities in two-dimensional in vitro cardiac tissues Sung-Jae Woo, Jin Hee Hong, Tae Yun Kim, Byung Wook Bae and Kyoung J Lee
Epicardial wavefronts arise from widely distributed transient sources during ventricular fibrillation in the isolated swine heart J M Rogers, G P Walcott, J D Gladden, S B Melnick, R E Ideker and M W Kay
Efficient control of spiral wave location in an excitable medium with localized heterogeneities J Schlesner, V S Zykov, H Brandtstädter, I Gerdes and H Engel
'Mind' contributions
Information transmission with spiking Bayesian neurons Timm Lochmann and Sophie Denève
How cesium dialysis affects the passive properties of pyramidal neurons: implications for voltage clamp studies of persistent sodium current Ilya A Fleidervish and Lior Libman
Eigenanalysis of a neural network for optic flow processing F Weber, H Eichner, H Cuntz and A Borst
Time-warp invariant pattern detection with bursting neurons Tim Gollisch
Leader neurons in population bursts of 2D living neural networks J-P Eckmann, Shimshon Jacobi, Shimon Marom, Elisha Moses and Cyrille Zbinden
Decoding spatiotemporal spike sequences via the finite state automata dynamics of spiking neural networks Dezhe Z Jin
Self-organization and the selection of pinwheel density in visual cortical development Matthias Kaschube, Michael Schnabel and Fred Wolf
Free association transitions in models of cortical latching dynamics Eleonora Russo, Vijay M K Namboodiri, Alessandro Treves and Emilio Kropff
The mechanism of synchronization in feed-forward neuronal networks S Goedeke and M Diesmann
On diffusion processes with variable drift rates as models for decision making during learning P Eckhoff, P Holmes, C Law, P M Connolly and J I Gold
Bodenschatz Eberhard
Wolf Fred
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