Spatiotemporal Order Research Articles

Rhythm dynamics of complex neuronal networks with mixed bursting neurons

The spatiotemporal order and rhythm dynamics of a complex neuronal network with mixed bursting neurons are studied in this paper. A quantitative characteristic, the width factor, is introduced to describe the rhythm dynamics of an individual neuron, and the average width factor is used to characterize the rhythm dynamics of a neuronal network. An r parameter is introduced to denote the ratio of the short bursting neurons in the network. Then we investigate the effect of the ratio on the rhythm dynamics of the neuronal network. The critical value of r is derived, and the neurons in the network always remain short bursting when the r ratio is larger than the critical value.

Spatiotemporal order, disorder, and propagating defects in homogeneous system of relaxation oscillators

A variety of complex spatial patterns relevant to chemical and biological systems can be generated through reaction-diffusion mechanisms. In this paper, we show that diffusive coupling through the inactivating component in a system of relaxation oscillators extends such complexity to the temporal domain, generating remarkable spatiotemporal phenomena. We provide analytic explanations of the antiphase synchronization and spatially patterned oscillatory death regimes. We report a chimera state where patches with distinct dynamics coexist and also observe propagating phase defects resembling persistent structures in cellular automata that may be used for computation.

Grotesque Possible Worlds

The author of the articles shows that the grotesque is one of the most interesting ways of diagnosing changes and crisis in the anthroposphere (as a continuation of thinking about the subject from the middle of the seventeenth century through to postmodernity). According to Thomas Mann, the grotesque is one the most active notions in contemporary art. Its productivity results from the subject’s tendency to self-fulfilment, self-cognition, and self-definition; it is an independent vision and position in the “me – the world”, “me – community” relations. The grotesque is a strongly philosophical proposition, which bases its discourse on a conscious protest against present values and on transgressing all limiting and oppressive conventions. Therefore, the grotesque enhances the status of the subject, but it neither defends nor affi rms the subject in a direct manner. Apart from the social dimension, the grotesque also has numerous metaphysical references, the expression of which can be found in Kierkegaardian understanding of the metaphysical crisis as despair. Facing piercing emptiness, the human being tries to find some support and resorts to anything only to make a leap into the future. Laughter is only a manifestation of horror vacui, a specific dialectic moment devoid of any prospect of purification or comfort. What dominates a grotesque work is its open structure. The motifs which shape the spatiotemporal order do not always form a cause-and-effect system. Deliberately incoherent themes (logical coherence is not an aim) seem to be rather “deconstructors”, not constructors of the plot; they are intermittent, provoke the impression of a secret, a gleam, the absurd.

Gene networks: Dissecting pathways in retinal development and disease

During retinal neurogenesis, diverse cellular subtypes originate from multipotent neural progenitors in a spatiotemporal order leading to a highly specialized laminar structure combined with a distinct mosaic architecture. This is driven by the combinatorial action of transcription factors and signaling molecules which specify cell fate and differentiation. The emerging approach of gene network analysis has allowed a better understanding of the functional relationships between genes expressed in the developing retina. For instance, these gene networks have identified transcriptional hubs that have revealed potential targets and pathways for the development of therapeutic options for retinal diseases. Much of the current knowledge has been informed by targeted gene deletion experiments and gain-of-functional analysis. In this review we will provide an update on retinal development gene networks and address the wider implications for future disease therapeutics.

Spatiotemporal pattern formation in two-dimensional neural circuits: roles of refractoriness and noise

Refractoriness is one of the most fundamental states of neural firing activity, in which neurons that have just fired are unable to produce another spike, regardless of the strength of afferent stimuli. Another essential and unavoidable feature of neural systems is the existence of noise. To study the role of these essential factors in spatiotemporal pattern formation in neural systems, a spatially expended neural network model is constructed, with the dynamics of its individual neurons capturing the three most essential states of the neural firing behavior: firing, refractory and resting, and the network topology consistent with the widely observed center-surround coupling manner in the real brain. By changing the refractory period with and without noise in a systematic way in the network, it is shown numerically and analytically that without refractoriness, or when the refractory period is smaller than a certain value, the collective activity pattern of the system consists of localized, oscillating patterns. However, when the refractory period is greater than a certain value, crescent-shaped, localized propagating patterns emerge in the presence of noise. It is further illustrated that the formation of the dynamical spiking patterns is due to a symmetry breaking mechanism, refractoriness-induced symmetry breaking; that is generated by the interplay of noise and refractoriness in the network model. This refractoriness-induced symmetry breaking provides a novel perspective on the emergence of localized, spiking wave patterns or spike timing sequences as ubiquitously observed in real neural systems; it therefore suggests that refractoriness may benefit neural systems in their temporal information processing, rather than limiting the performance of neurons, as has been conventionally thought. Our results also highlight the importance of considering noise in studying spatially extended neural systems, where it may facilitate the formation of spatiotemporal order.

Molecular genetic control of cell patterning and fate determination in the developing ventral spinal cord

The generation of neuronal diversity in the ventral spinal cord during development is a multistep process that occurs with precise and reproducible spatiotemporal order. The proper functioning of the central nervous system requires that this be carried out with extraordinary precision from the outset. Extrinsic influences such as the secreted Sonic hedgehog (SHH) protein provide positional cues that are read out genetically as specific patterns of gene expression in subsets of dividing progenitors, which is the first overt indication that they have begun to embark upon cell-type-specific differentiation programs. Cells generated from these segregated domains will ultimately share similar properties and functions. Recent work illustrates that SHH, which regulates target genes via the GLI transcription factors, directly controls a subset of progenitor fate determinant genes and that both derepression and activation play a role in shaping the differential response to this morphogen.

On the role of flexoeffect in synchronization of electroconvective roll oscillations in nematics

We describe the dynamics of zigzag oscillations in a system of convective rolls in a nematic liquid crystal above the electroconvection threshold under the action of an ac voltage with a biased position of the mean value. It is found that an increase in the contribution from the constant component leads to a substantial increase in the spatiotemporal ordering of zigzag rolls and their synchronization with the homogeneous twist mode. The results confirm the flexoelectric mechanism of locking.

Intravital imaging of Drosophila airways by two-photon microscopy using GFP and autofluorescence

Remodeling of airways is a major characteristic of chronic asthma. Drosophila melanogaster is an ideal model to specifically study epithelial remodeling due to easy genetic modification and lack of an adaptive immune system. To understand the spatiotemporal order of cellular events of remodeling without missing important transition states requires noninvasive continuous imaging of the airways in living animals over longer periods of time.

IN-PHASE BURST SYNCHRONIZATION AND RHYTHM DYNAMICS OF COMPLEX NEURONAL NETWORKS

In-phase burst synchronization, spatiotemporal order and rhythm dynamics of a complex neuronal network with electrical or chemically excitatory synapses are studied in this paper. A quantitative characteristic, the width factor, is introduced to describe the rhythm dynamics of an individual neuron, and the average width factor is used to characterize the rhythm dynamics of a neural network. The in-phase burst synchronization is studied in terms of the burst phase order parameter. We also study the effects of the coupling schemes, the intrinsic neuronal property and the network topology on the rhythm dynamics of the network. It is found that the neuronal network with electrical coupling is easier to realize the in-phase burst synchronization than that with the chemically excitatory coupling. The bursting type of short bursting neuronal networks is unchanged for different coupling schemes with the coupling strength increasing. Moreover, the short bursting type is robust both to the coupling strength and the coupling scheme. As for the network topology, more links can only change the bursting type of long bursting neurons, but short bursting neurons are robust to the link numbers.

Self-organization in biological systems

Biological systems are considered that are capable of dynamic self-organization, i.e., spontaneous emergence of spatio-temporal order with the formation of various spatio-temporal patterns. A cell is involved in the organization of ontogenesis of all stages. Embryonic cells exhibit coordinated social behavior and generate ordered morphological patterns displaying variability and equifinality ofdevelopment. Physical and topological patterns are essential for biological systems as an imperative that restricts and directs biological morphogenesis. Biological self-organization is directed and fixed by natural selection during which selection of the most resistant, flexible, modulator systems capable of adaptive self-organization occurs.

Auditory extinction and spatio-temporal order judgment in patients with left- and right-hemisphere lesions

Auditory extinction and spatio-temporal order judgment (STOJ) were assessed in patients with acquired brain damage by systematically manipulating onset times in bilateral stimulation under free-field conditions. We tested the hypothesis that extinction will be reduced by increasing stimulus onset asynchrony. Two groups of patients with right-hemisphere (RH, n=17) or left-hemisphere (LH, n=17) damage were investigated in comparison to a healthy control group (n=12). The patients were recruited based on previously diagnosed impairments: auditory discrimination deficits with (RHE/LHE) or without extinction (RH0/LH0) due to cortical and/or subcortical temporo-parietally centred lesions. Stimuli were presented bilaterally in the acoustic free-field, with an onset asynchrony of ±30 to ±150ms, or unilaterally, from speakers located ±60°. Low frequency (LF) and high frequency (HF) stimuli were used to address spatial auditory processing in the horizontal plane based on the two main cues of interaural time and interaural intensity differences, respectively. The subjects’ task was to indicate whether they perceived one (left or right) or two stimuli (left and right), and in the case of two make an STOJ (left or right first). Temporal asynchrony significantly reduced extinction in those patients that previously exhibited extinction for bilateral-simultaneous stimulation (RHE/LHE). In addition, their error rates in STOJ were higher than the controls’. A number of patients with no previous signs of extinction in bilateral-simultaneous stimulation (RH0/LH0) also showed impaired STOJ: in RH0 patients this was specific to ipsilesional-leading stimuli, whilst in LH0 patients no side-specific effect was observed. The data support the notion of differential roles for the two hemispheres in spatio-temporal auditory perception and are discussed with respect to prevalent models of extinction and its possible long-term reduction.

Beyond the Boundaries of Interference: Ramón Gómez de la Serna and the Radio Revolution

RAMON Gomez de la Serna was a trailblazer Spain's early radio industry. From the moment the fledgling radio stations Radio Barcelona and Radio Iberica began sporadically broadcasting 1924, he was captivated by radio technology and its epitome of all things modern. He was simply awestruck at how a mechanical device simply called aparato could effectively collapse the spatiotemporal order and fold the listener into a discursive community thriving thousands of miles away. In 1925, he began his involvement with Madrid's innovative Union Radio that King Alfonso XIII and Primo de Rivera inaugurated personally, but it was not until 1930 that the radio station granted him the ability to broadcast from the intimacy of his apartment (Diaz 120). As far as we know, he was the first vanguardista Spain to have a radio emitter at his immediate disposal. An ardent believer radio's democratizing potential, he broadcast a miscellany of daily reports that consisted nothing less than rendering intelligible the dynamism of urban experience: Un dia relatare el extremo de la obra excepcional sobre la misma marcha de los acontecimientos ... otro dia el gran hombre que muera a la medianoche tendra su necrologia inmediata con lirismo de primera oracion sobre su cadaver ... otro dia radiare la conversacion sin aire de entrevista que la casualidad me lleva a sostener ... Mi voz sera como la voz de la intimidad y de la conciencia, dando los ultimos alcances del mundo, para lo que lanzare los mas urgentes ?que pasa? por mi telefono. (Ventin Pereira 195) From what we know about Gomez de la Serna's involvement with radio before his exile to Argentina 1936, there is no doubt that he regarded the technology as a liberating medium. In his own words: Para mi la radio es el mayor teatro del espiritu que se conoce (Automoribundia 504). There is, however, another side to his technophilia that bears telling, particularly as it concerns his novella !Hay que matar el Morse! of 1925 and his contributions to the avant-garde radio journal Ondas between 1927 and 1932. It must be noted that Ondas was the literary wing of Union Radio and one of the foremost publications Spain on the exploding field of radio communication. As such, [e]n Ondas se dan cita casi todos los escritores que formaron parte del movimiento vanguardista espanol. La radio, como invento revolucionario, es en la revista donde encuentra su alter ego que le da replica en cuanto a modernidad se refiere (Blanco Carpintero 254-255). Gomez de la Serna's novella and contributions Ondas provide the basis for a more nuanced understanding of his affinity with radio technology. While they clearly evidence his passion for radio, they also clarify that he was quite exasperated with its technical shortcomings to the point of believing they could threaten the promise of the newly-formed radio community. What makes these writings so revealing is that they not only bear witness to the potentially devastating setbacks that beleaguered radio's early development (the seemingly insoluble problem of interference), but also give voice to the period's fundamental anxieties with communications integrity a world of fast-paced technological progress. Since the early Enlightenment, technological progress has frequently been regarded as that expansive teleological driving force propelling civilization in a desirable direction, to use J. B. Bury's well-known words (2). While narratives of progress have always retained a privileged status within modernizing societies, it is also true that at least since the time Rousseau conceived of le bon sauvage, they have also engendered more systematic counter-narratives that have registered the many ills unleashed by man's technological evolution. While Gomez de la Serna was a champion of progress and technological innovation his youth--between 1909 and 1919 he was an advocate of Marinetti's mechanized aesthetic of progress which great locomotives, twisting tunnels, armored cars, torpedo boats, monoplanes, and racing cars improved our lot by freeing us from the cultural burdens of the past--his views on the matter began to shift the 1920s (qtd. …

1SB-01 DNAの硬さと柔らかさ : 高次構造転移が生み出す時空間秩序(1SB 身体-細胞ダイナミクス連関:やわらかさの階層と連携,シンポジウム,日本生物物理学会第50回年会(2012年度))

1SB-01 DNAの硬さと柔らかさ : 高次構造転移が生み出す時空間秩序(1SB 身体-細胞ダイナミクス連関:やわらかさの階層と連携,シンポジウム,日本生物物理学会第50回年会(2012年度))

Administrative accounting systems (AAS) thought as systems of social interaction, based on Giddens's theory of structuration

The purpose of this paper is to consider the role that the administrative accounting systems (hereinafter AAS) play in the spatio-temporal order of social practices in modern organisations, hence we go over some works by authors related to the critical-interpretive school of thought, such as: Macintosh, Scapens, Boland, Lawrence and Northcott, Lowe, Burns, Englund and Gerdin, synthesising in three thematic axes the uses so far given to Giddens’s theory of structuration in the accounting and management research. Those axes are: 1 the analysis of the three dimensions of the structure 2 how to apply the concepts given by Giddens in the study of the management accounting systems (hereinafter MAS) 3 the diverse conceptions of the rules and routines that compose them. In addition, we intend to look over some new possibilities for studying and extending the comprehension domain of the social character of the MAS, including other analytical categories of the theory still not taken into account and precising such concepts through the proposal of what in this paper is denoted as AAS, interpreted as an interaction system based on the notion of social system provided by Giddens, a notion different from those developed so far in the reviewed literature.

Delay-enhanced coherent chaotic oscillations in networks with large disorders

We study the effect of coupling delay in a regular network with a ring topology and in a more complex network with an all-to-all (global) topology in the presence of impurities (disorder). We find that the coupling delay is capable of inducing phase-coherent chaotic oscillations in both types of networks, thereby enhancing the spatiotemporal complexity even in the presence of 50% of symmetric disorders of both fixed and random types. Furthermore, the coupling delay increases the robustness of the networks up to 70% of disorders, thereby preventing the network from acquiring periodic oscillations to foster disorder-induced spatiotemporal order. We also confirm the enhancement of coherent chaotic oscillations using snapshots of the phases and values of the associated Kuramoto order parameter. We also explain a possible mechanism for the phenomenon of delay-induced coherent chaotic oscillations despite the presence of large disorders and discuss its applications.

Fate Restriction and Multipotency in Retinal Stem Cells

Stem cells have the capacity to both self-renew and generate postmitotic cells. Long-term tracking of individual clones in their natural environment constitutes the ultimate way to validate postembryonic stem cells. We identify retinal stem cells (RSCs) using the spatiotemporal organization of the fish retina and follow the complete offspring of a single cell during the postnatal life. RSCs generate two tissues of the adult fish retina, the neural retina (NR) and the retinal-pigmented epithelium (RPE). Despite their common embryonic origin and tight coordination during continuous organ growth, we prove that NR and RPE are maintained by dedicated RSCs that contribute in a fate-restricted manner to either one or the other tissue. We show that in the NR, RSCs are multipotent and generate all neuron types and glia. The clonal origin of these different cell types from a multipotent NSC has far-reaching implications for cell type and tissue homeostasis.

Spontaneous motion of a droplet coupled with a chemical wave

We propose a framework for the spontaneous motion of a droplet coupled with internal dynamic patterns generated in a reaction-diffusion system. The spatiotemporal order of the chemical reaction gives rise to inhomogeneous surface tension and results in self-propulsion driven by the surrounding flow due to the Marangoni effect. Numerical calculations of internal patterns together with theoretical results of the flow fields at low Reynolds number reproduce well the experimental results obtained using a droplet of the Belousov-Zhabotinsky reaction medium.

Modelling the mobility of living organisms in heterogeneous landscapes: does memory improve foraging success?

Thanks to recent technological advances, it is now possible to track with an unprecedented precision and for long periods of time the movement patterns of many living organisms in their habitat. The increasing amount of data available on single trajectories offers the possibility of understanding how animals move and of testing basic movement models. Random walks have long represented the main description for micro-organisms and have also been useful to understand the foraging behaviour of large animals. Nevertheless, most vertebrates, in particular humans and other primates, rely on sophisticated cognitive tools such as spatial maps, episodic memory and travel cost discounting. These properties call for other modelling approaches of mobility patterns. We propose a foraging framework where a learning mobile agent uses a combination of memory-based and random steps. We investigate how advantageous it is to use memory for exploiting resources in heterogeneous and changing environments. An adequate balance of determinism and random exploration is found to maximize the foraging efficiency and to generate trajectories with an intricate spatio-temporal order, where travel routes emerge without multi-step planning. Based on this approach, we propose some tools for analysing the non-random nature of mobility patterns in general.

Delay-enhanced spatiotemporal order in coupled neuronal systems

In a network of noisy neuron oscillators with time-delayed coupling, we uncover a phenomenon of delay-enhanced spatiotemporal order. We find that time delay in the coupling can dramatically enhance the temporal coherence and spatial synchrony of the noise-induced spike trains. In addition, if the delay time is tuned to nearly match the intrinsic spiking period of the neuronal network, both the coherence and the synchrony reach maximum levels, demonstrating an interesting type of resonance phenomenon with delay. Such findings are shown to be robust to the change of the noise intensity and the rewiring probability of small-world network.

Evolution of developmental pattern for vertebrate dentitions: an oro‐pharyngeal specific mechanism

Classically the oral dentition with teeth regulated into a successional iterative order was thought to have evolved from the superficial skin denticles migrating into the mouth at the stage when jaws evolved. The canonical view is that the initiation of a pattern order for teeth at the mouth margin required development of a sub-epithelial, permanent dental lamina. This provided regulated tooth production in advance of functional need, as exemplified by the Chondrichthyes. It had been assumed that teeth in the Osteichthyes form in this way as in tetrapods. However, this has been shown not to be true for many osteichthyan fish where a dental lamina of this kind does not form, but teeth are regularly patterned and replaced. We question the evolutionary origin of pattern information for the dentition driven by new morphological data on spatial initiation of skin denticles in the catshark. We review recent gene expression data for spatio-temporal order of tooth initiation for Scyliorhinus canicula, selected teleosts in both oral and pharyngeal dentitions, and Neoceratodus forsteri. Although denticles in the chondrichthyan skin appear not to follow a strict pattern order in space and time, tooth replacement in a functional system occurs with precise timing and spatial order. We suggest that the patterning mechanism observed for the oral and pharyngeal dentition is unique to the vertebrate oro-pharynx and independent of the skin system. Therefore, co-option of a successional iterative pattern occurred in evolution not from the skin but from mechanisms existing in the oro-pharynx of now extinct agnathans.