Small Network (small + network)

Distribution by Scientific Domains


Selected Abstracts


Consistent dynamics suggests tight regulation of biophysical parameters in a small network of bursting neurons

DEVELOPMENTAL NEUROBIOLOGY, Issue 14 2006
Attila Szücs
Abstract The neuronal firing patterns in the pyloric network of crustaceans are remarkably consistent among animals. Although this characteristic of the pyloric network is well-known, the biophysical mechanisms underlying the regulation of the systems output are receiving renewed attention. Computer simulations of the pyloric network recently demonstrated that consistent motor output can be achieved from neurons with disparate biophysical parameters among animals. Here we address this hypothesis by pharmacologically manipulating the pyloric network and analyzing the emerging voltage oscillations and firing patterns. Our results show that the pyloric network of the lobster stomatogastric ganglion maintains consistent and regular firing patterns even when entire populations of specific voltage-gated channels and synaptic receptors are blocked. The variations of temporal parameters used to characterize the burst patterns of the neurons as well as their intraburst spike dynamics do not display statistically significant increase after blocking the transient K-currents (with 4-aminopyridine), the glutamatergic inhibitory synapses (with picrotoxin), or the cholinergic synapses (with atropine) in pyloric networks from different animals. These data suggest that in this very compact circuit, the biophysical parameters are cell-specific and tightly regulated. © 2006 Wiley Periodicals, Inc. J Neurobiol, 2006 [source]


The Rich, the Powerful and the Endangered: Conservation Elites, Networks and the Dominican Republic

ANTIPODE, Issue 3 2010
George Holmes
Abstract:, This paper explores conservation as an elite process in the Dominican Republic. It begins by showing how conservation at a global level is an elite process, driven by a small powerful elite. Looking at the Dominican Republic, it demonstrates how the extraordinary levels of protection have been achieved by a small network of well connected individuals, who have been able to shape conservation as they like, while limiting the involvement by the large international conservation NGOs who are considered so dominant throughout Latin America. Despite this, conservation both globally and in the Dominican Republic is shown to share similar political structures and the same lack of critique of capitalism or its environmental impacts. [source]


Offer and demand: proliferation and survival of neurons in the dentate gyrus

EUROPEAN JOURNAL OF NEUROSCIENCE, Issue 12 2005
Konrad Lehmann
Abstract The proliferation and survival of new cells in the dentate gyrus of mammals is a complex process that is subject to numerous influences, presenting a confusing picture. We suggest regarding these processes on the level of small networks, which can be simulated in silico and which illustrate in a nutshell the influences that proliferating cells exert on plasticity and the conditions they require for survival. Beyond the insights gained by this consideration, we review the available literature on factors that regulate cell proliferation and neurogenesis in the dentate gyrus in vivo. It turns out that the rate of cell proliferation and excitatory afferents via the perforant path interactively determine cell survival, such that the best network stability is achieved when either of the two is increased whereas concurrent activation of the two factors lowers cell survival rates. Consequently, the mitotic activity is regulated by systemic parameters in compliance with the hippocampal network's requirements. The resulting neurogenesis, in contrast, depends on local factors, i.e. the activity flow within the network. In the process of cell differentiation and survival, each cell's spectrum of afferent and efferent connections decides whether it will integrate into the network or undergo apoptosis, and it is the current neuronal activity which determines the synaptic spectrum. We believe that this framework will help explain the biology of dentate cell proliferation and provide a basis for future research hypotheses. [source]


Big decisions by small networks

BIOESSAYS, Issue 8 2010
Stefan Schuster
Abstract The primate brain is able to guide complex decisions that can rapidly be adapted to changing constraints. Unfortunately, the vast numbers of highly interconnected neurons that seem to be needed make it difficult to study the cellular mechanisms that underlie the flexible combination of stored and acute information during a decision. Established simpler networks, particularly with few and identified neurons, would lend themselves more readily to such a dissection. But can simple networks implement complex and flexible decisions similarly? After a brief overview of complex decisions in primates and of decision-making in simple networks, I argue that simpler systems can combine complexity with accessibility at the cellular level. Indeed, examination of a network in fish may help in dissecting key mechanisms of complex and flexible decision-making in an established model of synaptic plasticity at the level of identified neurons. [source]