Showing papers by "Nicholas J. Strausfeld published in 1989"

Physiology and morphology of projection neurons in the antennal lobe of the male moth Manduca sexta

Abstract: 1. We have used intracellular recording and staining, followed by reconstruction from serial sections, to characterize the responses and structure of projection neurons (PNs) that link the antennal lobe (AL) to other regions of the brain of the male sphinx mothManduca sexta. 2. Dendritic arborizations of the AL PNs were usually restricted either to ordinary glomeruli or to the male-specific macroglomerular complex (MGC) within the AL neuropil. Dendritic fields in the MGC appeared to belong to distinct partitions within the MGC (Figs. 2, 3). PNs innervating the ordinary glomeruli had arborizations in a single glomerulus (uniglomerular) (Figs. 6, 7, 9, 11, 12A) or in more than one ordinary glomerulus of one AL (multiglomerular) (Figs. 12B, C, 14, 15), or in one case, in single glomeruli in both ALs (bilateral-uniglomerular) (Fig. 16). One PN innervated the MGC and many or all ordinary glomeruli of the AL (Fig. 13). 3. PNs with dendritic arborizations in the ordinary glomeruli and PNs associated with the MGC typically projected both to the calyces of the ipsilateral mushroom body and to the lateral protocerebrum, but some differences in the patterns of termination in those regions have been noted for the two classes of PNs (Figs. 2, 3, 6, 7, 9, 16). One PN conspicuously lacked branches in the calyces but did project to the lateral protocerebrum (Fig. 14). The PN innervating the MGC and many ordinary glomeruli projected to the calyces of the ipsilateral mushroom body and the superior protocerebrum (Fig. 13). 4. Crude sex-pheromone extracts excited all neurons with arborizations in the MGC, although some were inhibited by other odors (Figs. 3, 4). One P(MGC) was excited by crude sex-pheromone extract and by a mimic of one component of the pheromone blend but was inhibited by another component of the blend (Fig. 5). 5. PNs with dendritic arborizations in ordinary glomeruli were excited (Figs. 7, 8, 10) or inhibited (Figs. 9, 11) by certain non-pheromonal odors. Some of these PNs also responded to mechanosensory stimulation of the antennae (Figs. 10, 11, 15, 16). 6. The PN with dendritic arborizations in the MGC and many ordinary glomeruli was excited by crude sex-pheromone extracts and non-pheromonal odors and also responded to mechanosensory stimulation of the antenna (Fig. 13).

Insect Vision and Olfaction: Common Design Principles of Neuronal Organization

Abstract: In insects, the organization of neurons in visual and olfactory neuropils is comparable to arrangements in analogous systems in the brains of higher vertebrates. However, although the two modalities of vision and olfaction are subjectively quite different from each other, in insects they are served by common neuroarchitectures, the glomeruli, which are here suggested to be paramount in the processing of qualitative information. Visual and olfactory systems show other specific similarities with respect to the parallel organization of large- and small-axoned neurons. In the visual system, two parallel channels comprise large color-insensitive and small color-sensitive relay neurons that are linked to two major descending pathways. Color insensitive pathways supply motor circuits mediating visually stabilized flight and optokinetic head movements. This pathway is distinct from the parallel subsystem comprising numerous smaller neurons and many synaptic stations that supply leg and direct flight muscle motor neuropils. These two subsystems provide a simple model of magno- and parvocellular organizations identified in the mammalian visual system. Surprisingly, there exists a similar parallel organization amongst large- and small-axoned neurons in the insect olfactory system. Magnocellular olfactory projection neurons provide a relatively direct route to descending pathways. Smaller parvocellular projection neurons provide the first step in a complex sequence of neurons in which higher brain centers play a cardinal role.