Cell Types and Connectivity Patterns in Mosaic Retinas
In many parts of vertebrate and invertebrate central nervous systems, groups of nerve or receptor cells can be found that are arranged and connected according to a precise, functionally defined pattern (Braitenberg, 1973; Santini, 1975; Strausfeld, 1976; Chan-Palay, 1977). In these cases, groups of cell bodies or synapses appear as basically similar configurations, which, however, are different in detail from each other. Such abstract patterns of connectivity are of a statistical nature and do not allow, in a given example, for the prediction of the localization or connections of a particular cell. "Wiring diagrams", therefore, can be obtained only from a multitude of individual observations. In contrast, in several sensory organs, concrete patterns occur that con sist of a regular, mosaic-like, and geometric arrangement of similar cell types. The constancy of such a mosaic allows predictions about certain units of the pattern on the basis of only a few exemplary observations. Typical examples are found in the visual system: In the compound eye of insects, each ommatidium contains a definite number of visual cells that are grouped around the optical axis in a hexogonal array (Kirsch feld, 1967); in the vertebrate retina, mosaics of geometrically arranged cones are found most frequently in lower vertebrates; they are common among teleosts. A number of studies have dealt with their phylogenetic significance and their functional role as adaptation to specific environments or modes of feeding.
What people are saying - Write a review
We haven't found any reviews in the usual places.
Other editions - View all
accessory single cone amacrine cell araldite axon bipolar cells bipolar dendrites brook trout cell body central single cone central square unit cichlid cone ellipsoids cone horizontal cells cone mosaics connectivity cyprinids cytoplasm dendritic fields diameter double cone partners double cone pedicles ellipsoids equal double cones external limiting membrane external plexiform layer Field catch ﬁelds ﬁgures ﬁrst ganglion cells Golgi Golgi-impregnated horizontal cell processes intermediate bipolar cell internal nuclear layer interneurons interplexiform cell lateral inhibition Miiller cells morphologic mosaic retinas myoids Nannacara anomala neurons number of cone number of synaptic observed outer segments phosphotungstic acid photoreceptor cells plasmalemma postsynaptic presynaptic regular arrangement ribbon synapses rod spherules sclerad processes semithin sections single cone pedicle single cone types small bipolar cells somata square mosaic square pattern Stell synaptic ribbons synaptic ridge synaptic vesicles tangential sections teleosts type of cone types of horizontal unequal double cones vertebrates visual cells Wagner whereas