Pattern formation in the lateral line of zebrafish.

The lateral line of fish and amphibians is a sensory system that comprises a number of individual sense organs, the neuromasts, arranged in a defined pattern on the surface of the body. A conspicuous part of the system is a line of organs that extends along each flank (and which gave the system its name). At the end of zebrafish embryogenesis, this line comprises 7-8 neuromasts regularly spaced between the ear and the tip of the tail. The neuromasts are deposited by a migrating primordium that originates from the otic region. Here, we follow the development of this pattern and show that heterogeneities within the migrating primordium prefigure neuromast formation.     

Pattern formation in associative neural networks with weak lateral interaction

A model is proposed for the formation of singularities in the director field of orientation-selective cells in the visual cortex. The model consists of a two-layer associative neural net. The forward connections converge to a continuum of steady states. The degeneracy is removed by lateral interactions. It is shown that in many cases the director field contains critical points which are identified as the vortex locations. Received: 1 January 1993/Accepted in revised form: 8 September 1993     

Pattern formation in plant epidermis through inhibition of immediately adjacent cells by pattern elements

Summary Examples of short-range inhibition in plant development were sought which satisfy four criteria for simplicity of expression. The range of inhibition extends only to adjacent cells and these criteria are (1) pattern of expression is within a two-dimensional array of cells, (2) cells of the array do not proliferate during pattern formation, (3) spacing between special cells extends only for a distance of one cell, and (4) no unequal cell divisions occur to complicate the pattern of cell arrangement. In one case of hairs or trichomes, the cells are evenly dispersed over the adaxial surface of the sepal ofSalvia splendens L. The R value of Clark and Evans is 1.64 for hair arrangement and hairs are formed from 21.1% of the epidermal cells. Based on cell behavior and an assumed method of inhibition, ordinary differential equations were written for formation of three types of cells in the tissue, free cells (F), trichome-bearing cells (T), and inhibited cells (I). Computer generated numerical solutions for these equations give cell type frequencies of 0.056 (F), 0.198 (T), and 0.745 (I), close to the observed values of 0.057 (F), 0.211 (T), and 0.731 (I). A similar approach was employed in analysis for the deployment of the cotton fibers in the ovular epidermis ofGossypium hirsutum L. and for that of the floating stomata of the fernAnemia phyllitidis (L). Sw. In general, these three patterns of epidermal deriviatives are most easily explained by one-cell wide inhibition fields between inhibiting special cells and inhibited contiguous cells. Other patterns in plants cannot be explained by this mechanism.     

Pattern formation by bacteria-driven flow

Some marine bacterial species form mucosal layers, called veils, on sulfidic marine sediment. The bacteria attached to this veil actively swim and exert force on the surrounding fluid. The bacteria can break free of the veil and swim, chemotacting back to the veil. Over time the veil forms holes arranged in a hexagonal pattern. Motivated by this system, we present a simplified model to describe pattern formation induced by force-generating bodies embedded in a layer surrounded by fluid. When the bacteria break free of the layer, they are advected by the flow and diffuse. Competition between the fluid flow generated by the embedded bacteria and diffusion of the swimmers leads to a novel instability that drives bacterial aggregation. Analytic and numeric analysis of this system correctly defines the length scale and developmental timescale for the biological system. Similar flow dynamics may also play a role in other biological systems such as encrusting bryozoan colonies.     

Activity-dependent local protection and lateral inhibition control synaptic competition in developing mitral cells in mice

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A lateral look at olfactory bulb lateral inhibition

Contrast enhancement in sensory systems often relies on spatial filters implemented by lateral inhibition. However, in this issue of Neuron, Fantana et al. provide evidence that lateral inhibition in the olfactory bulb selectively acts between sparse populations of principal neurons without regard to spatial relations.     

Boolean analysis of lateral inhibition

Journal of Mathematical Biology - We study Boolean networks which are simple spatial models of the highly conserved Delta–Notch system. The models assume the inhibition of Delta in each cell...     

Pattern formation and cortical maps

The response selectivities of neurons in adult primary sensory cortices depend on intricate patterns of synaptic connections; these selectivities are arranged over cortex in equally rich fashion. Characterising these patterns, and particularly the activity-dependence (and independence) of their developmental trajectories, has been a major task for experimental and theoretical neuroscience. Here, we describe and analyse a paradigmatic algorithm for activity-dependent development of the refinement and generation of neuronal selectivities, and relate it to some of the wealth of suggestions in the literature.     

Pattern formation and developmental mechanisms

A selection of World Wide Web sites relevant to papers published in this issue of Current Opinion in Genetics & Development.