Showing papers by "Nicholas J. Strausfeld published in 1970"

The optic lobes of Lepidoptera.

Abstract: Variants of the Golgi-Colonnier (1964) selective silver procedure have been used to show up neurons in insect brains. Neural elements are particularly clearly impregnated in the optic lobes. Three classes of nerve cells can be distinguished; perpendicular (class I), tangential (class II) and amacrine cells (class III). There are many types of neurons in each class which together have a very wide variety of form. Their components are related to specific strata in the optic lobe regions. Short visual cells from the retina terminate in the lamina in discrete groups of endings (optic cartridges). Pairs of long visual fibres from ommatidia pass through the lamina and end in the medulla. Class I cells link these two regions in parallel with the long visual fibres and groups of these elements define columns in the medulla. These in turn give rise to small-field fibres that project to the lobula complex. Tangential processes intersect the parallel arrays of class I cells at characteristic levels. Some are complex in form and may invade up to three regions. Another type provides a direct link between the ipsi- and contralateral optic lobe. Amacrine cells are intrinsic to single lobe regions and have processes situated at the same levels as those of classes I and II cells. A fifth optic lobe region, the optic tubercle, is connected to the medulla and lobula and also receives a set of processes from the mid-brain. There are at least six separate types of small-field relays which could represent the retina mosaic arrangement in the lobula.

The Optic Lobes of Diptera

Abstract: The optic lobes of Diptera have been examined by variants of the Golgi-Colonnier selective staining techniques and by reduced silver procedures. All, bar one, of the elements described by the earlier authors (Vigier 1908; Zawarzin 1913; Cajal & Sanchez 1915) have been seen, in part or in their entirely, in these preparations. Many other forms, hitherto unrecognized, have been found. Their perpendicular topographical relationships have been reconstructed in the optic lobe regions. Some lateral relationships have also been reconstructed between elements in regions whose columnar arrangement is clearly discernible in Golgi preparations; these include the lamina and the medulla. In the Diptera the projection pattern of the retina mosaic into the lamina neuropil involves complex chiasmata between the two regions (Braitenberg 1967); these have been confirmed from these species. The retina-lamina mosaic is, essentially, homotopically preserved in the columnar medulla, via long visual fibres and monopolar cells. The medullary mosaic is preserved through its strata by transmedullary cells and the longest small-field amacrine cells. The mosaic is projected to the two regions of the lobula complex by class I cells (see part I). The organization of the tangential cell processes suggests that some of them may interact with large or whole field aggragates of the relayed retinal mosaic. Others, especially in the lobula, may interact with small oval or narrow strip-field aggragates. Although there are many differences of neural form and number of neurons between species, both the Lepidoptera and Diptera have the same fundamental plan of neuroarchitecture.

The compound eye of the fly (Musca domestica): connections between the cartridges of the lamina ganglionaris

Abstract: In addition to the three first order interneurons (L1, L2, L3) which are present in each optic cartridge of the lamina, a fourth type of interneuron (L4) has been discovered whose collaterals to other cartridges compose an orderly network arrangement of fibres under the lamina's inner face.