Dror Cohen

A method for detecting and describing the features of faces using deformable templates is described. The feature of interest, an eye for example, is described by a parameterized template. An energy function is defined which links edges, peaks, and valleys in the image intensity to corresponding properties of the template. The template then interacts dynamically with the image, by altering its parameter values to minimize the energy function, thereby deforming itself to find the best fit. The final parameter values can be used as descriptors for the features. This method is demonstrated by showing deformable templates detecting eyes and mouths in real images.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Doublecortin (DCX) is a microtubule-associated protein necessary for neuronal migration. In spite of its ubiquitous distribution in dendrites, its possible role in dendrite development has not yet been documented. The present study examined the effects of different expression levels of DCX on the arborization of dendrites in cultured hippocampal neurons. Reduced expression of DCX following RNAi transfection resulted in reduced branch points, total length and complexity of the dendrites. Overexpression of DCX resulted in an increase in branch points and complexity of the dendrites. In contrast to control green fluorescent protein cells, DCX-overexpressing cells maintained highly branched and complex dendritic trees when subjected to reduced neuronal activity by blockade of immature GABA(A) receptors. These results suggest that DCX supports developing dendrites, in addition to its role in neuronal migration.

The three Negev Desert gerbils, Gerbillus pyramidum (greater Egyptian sand gerbil), Gerbillus allenbyi (Allenby's gerbil), and Gerbillus dasyurus (Wagner's gerbil), show strong patterns of habitat selection along a gradient, from sandy to loessal to rocky habitats, respectively. Within a habitat, a gerbil must be able to harvest seeds and escape predators. To test for the habitat-specific processes governing habitat partitioning by gerbil species, we investigated the roles of escape substrate and foraging substrate in affecting patch use. In an aviary, we manipulated predatory risk using artificial illumination and the presence of Barn Owls (Tyto alba). We manipulated escape substrate and foraging substrate by creating habitat and food patches of sand, rock (a mix of sand and small rocks), and loess substrate. In response to owls, all three gerbil species foraged less and increased their giving-up densities (GUDs) in food patches. In response to foraging substrate, all three species had their lowest GUDs on sand, and their highest GUDs on loess. Gerbillus dasyurus responded less intensively to owls when loess comprised the foraging substrate. Also, each species depended more on its “home” foraging substrate than did the others for the total amount of seeds harvested. Gerbillus pyramidum in particular harvested a greater proportion from sand than did G. dasyurus. Escape substrate had no direct effects on patch use. However, G. dasyurus exhibited a foraging substrate × escape substrate interaction, as the rocky escape substrate enhanced its use of the rocky foraging substrate. Our experiments show that foraging substrate contributes to habitat use by G. allenbyi and G. pyramidum, and that both foraging substrate and escape substrate contribute to habitat use by G. dasyurus.