Such neurons have long been known to exist in the visual system and other parts of the vertebrate and invertebrate nervous system. In invertebrates, the first DS neurons were found in flies, located in a brain structure called the lobula plate. The lobula plate is the third of a stack of neuropiles of the fly’s optic lobe, each forming a retinotopic representation of the image as initially formed by the compound eye. Starting from the periphery, these are called lamina, medulla, and lobula complex, the latter being divided into an anterior lobula

and a posterior lobula plate (Figure 2A). As a consequence of the retinotopic structure, each neuropile is built from repetitive columns containing an identical set of neurons first described anatomically by Ramón y Cajal on the basis selleck screening library of Golgi staining (Cajal and Sanchez, 1915). For the fruit fly Drosophila melanogaster, a large set of columnar neurons has been cataloged ( Fischbach and Dittrich, 1989). More recently, this set has been complemented by assigning transmitter systems to various columnar neurons (e.g., Morante and Desplan, 2008, Raghu and Borst, 2011 and Raghu et al., 2011). Each columnar neuron, whether located in the lamina, medulla, or lobula complex, has distinct arborizations in particular layers

of its neuropile and some neurons connecting the lamina with the medulla or the medulla to the lobula plate. Furthermore, all these cells

CCI-779 datasheet restrict their arborizations to a small part of their respective neuropile, mostly respecting the columnar borders. This is different for the lobula plate, where dendrites of the so-called lobula plate tangential cells span large parts of the neuropile, apparently collecting signals from local neurons within hundreds of columns. These tangential cells have been thoroughly analyzed, first in the blow fly Calliphora ( Hausen, 1982a, Hausen, 1982b, Hengstenberg, 1982, Hengstenberg et al., 1982, Borst and Haag, 1996, Haag et al., 1997 and Haag et al., 1999) and, more recently, also in the fruit fly Drosophila ( Joesch et al., 2008 and Schnell Ketanserin et al., 2010). Although the exact number depends on the species, the tangential cells comprise roughly 50 neurons, each of which can be uniquely identified on the basis of its anatomy, receptive field, and electrical response properties. All tangential cells respond to visual motion in a DS way. Among them, the three cells of the horizontal system, called HS cells, respond most strongly to horizontal image motion: When the pattern moves from the front to the back, the cells depolarize (Figure 2B). This direction of image motion is their preferred direction. When the pattern moves from the back to the front, they hyperpolarize. This direction of image motion is their null direction.