Wide-Field Motion Integration in Fly VS Cells: Insights from an Inverse Approach

Fly lobula plate tangential cells are known to perform wide-field motion integration. It is assumed that the shape of these neurons, and in particular the shape of the subclass of VS cells, is responsible for this type of computation. We employed an inverse approach to investigate the morphology-function relationship underlying wide-field motion integration in VS cells. In the inverse approach detailed, model neurons are optimized to perform a predefined computation: here, wide-field motion integration. We embedded the model neurons to be optimized in a biologically plausible model of fly motion detection to provide realistic inputs, and subsequently optimized model neuron with and without active conductances (gNa, gK, gK(Na)) along their dendrites to perform this computation. We found that both passive and active optimized model neurons perform well as wide-field motion integrators. In addition, all optimized morphologies share the same blueprint as real VS cells. In addition, we also found a recurring blueprint for the distribution of gK and gNa in the active models. Moreover, we demonstrate how this morphology and distribution of conductances contribute to wide-field motion integration. As such, by using the inverse approach we can predict the still unknown distribution of gK and gNa and their role in motion integration in VS cells

Neural Action Fields for Optic Flow Based Navigation: A Simulation Study of the Fly Lobula Plate Network

Optic flow based navigation is a fundamental way of visual course control described in many different species including man. In the fly, an essential part of optic flow analysis is performed in the lobula plate, a retinotopic map of motion in the environment. There, the so-called lobula plate tangential cells possess large receptive fields with different preferred directions in different parts of the visual field. Previous studies demonstrated an extensive connectivity between different tangential cells, providing, in principle, the structural basis for their large and complex receptive fields. We present a network simulation of the tangential cells, comprising most of the neurons studied so far (22 on each hemisphere) with all the known connectivity between them. On their dendrite, model neurons receive input from a retinotopic array of Reichardt-type motion detectors. Model neurons exhibit receptive fields much like their natural counterparts, demonstrating that the connectivity between the lobula plate tangential cells indeed can account for their complex receptive field structure. We describe the tuning of a model neuron to particular types of ego-motion (rotation as well as translation around/along a given body axis) by its ‘action field’. As we show for model neurons of the vertical system (VS-cells), each of them displays a different type of action field, i.e., responds maximally when the fly is rotating around a particular body axis. However, the tuning width of the rotational action fields is relatively broad, comparable to the one with dendritic input only. The additional intra-lobula-plate connectivity mainly reduces their translational action field amplitude, i.e., their sensitivity to translational movements along any body axis of the fly

Vision for navigation: what can we learn from ants?

The visual systems of all animals are used to provide information that can guide behaviour. In some cases insects demonstrate particularly impressive visually-guided behaviour and then we might reasonably ask how the low-resolution vision and limited neural resources of insects are tuned to particular behavioural strategies. Such questions are of interest to both biologists and to engineers seeking to emulate insectlevel performance with lightweight hardware. One behaviour that insects share with many animals is the use of learnt visual information for navigation. Desert ants, in particular, are expert visual navigators. Across their foraging life, ants can learn long idiosyncratic foraging routes. What's more, these routes are learnt quickly and the visual cues that define them can be implemented for guidance independently of other social or personal information. Here we review the style of visual navigation in solitary foraging ants and consider the physiological mechanisms that underpin it. Our perspective is to consider that robust navigation comes from the optimal interaction between behavioural strategy, visual mechanisms and neural hardware.We consider each of these in turn, highlighting the value of ant-like mechanisms in biomimetic endeavours

A fourth Mediterranean Rhynchothorax and remarks on the genus (Pycnogonida)

A species of Rhynchothorax, Rh. alcicornis nova species, the fourth known from the Mediterranean Sea, and the tenth in the genus is described. A new key to the species and a review of the genus are provided; an attempt is made to arrange all species known into four different species groups

Pycnogonida from Pantelleria and Catania, Sicily

The paper reports on two small collections from the island of Pantelleria and the vicinity of Catania, Sicily. The former locality (mostly surface samples) yielded 52 specimens of 9 species in 9 samples, the latter 190 specimens of 14 species in 11 samples. One species of Nymphon proved to be new to science; it belongs to an uniunguiculate species group with N. longicoxa Hoek, 1881, and N. prolatum Fage, 1942, as nearest relatives. The question of Tanystylum in the Mediterranean is raised again and it is decided that there are two species, T. conirostrum (Dohrn, 1881) and T. orbiculare Wilson, 1878, respectively. The male of Ammothella longioculata Faraggiana, 1940 is figured for the first time in order to compare it with A. longipes (Dohrn, 1881). Precisions about external morphological characters of Ammothella uniunguiculata (Dohrn, 1881) are given, whereas Anoplodactylus angulatus (Dohrn, 1881) is compared with A. virescens (Hodge, 1864)

Pycnogonida from Costa Rica collected by Scuba Diving

The knowledge of the pycnogonid fauna of Costa Rica is poor. This is the first report on Pycnogonida collected by scuba diving from both oceans of Costa Rica. Nine species from the Caribbean side and one from the Pacific coast are reported. We add eight species to the Caribbean fauna and one to the Pacific fauna of Costa Rica. No species new to science were encountered.KEY WORDSPycnogonida, Costa Rica, scuba collecting, Caribbean, Pacific.Se sabe poco de los picnogónidos de Costa Rica. Este es el primer informe sobre especímenes de Pycnogonida recolectados por buceo, en ambos océanos de Costa Rica. Se encontraron nueve especies de la zona del Caribe y uno de la costa del Pacífico. Se añaden ocho especies a la fauna del Caribe y una a la fauna del Pacífico de Costa Rica. Ninguna de las especies encontradas es nueva para la ciencia.PALABRAS CLAVEPycnogonida, Costa Rica, recolección por buceo, Caribe, Pacífico

The genus Rhynchothorax (Pycnogonida) in the Mediterranean Sea

Of the five species of Rhynchothorax recorded from the Mediterranean, the description of Rh. alcicornis is completed with new material, and Rh. anophthalmus is synomymized with Rh. philopsammum