Showing papers by "Nicholas J. Strausfeld published in 2001"

Taurine-, aspartate- and glutamate-like immunoreactivity identifies chemically distinct subdivisions of Kenyon cells in the cockroach mushroom body.

Abstract: The lobes of the mushroom bodies of the cockroach Periplaneta americana consist of longitudinal modules called laminae. These comprise repeating arrangements of Kenyon cell axons, which like their dendrites and perikarya have an affinity to one of three antisera: to taurine, aspartate, or glutamate. Taurine-immunopositive laminae alternate with immunonegative ones. Aspartate-immunopositive Kenyon cell axons are distributed across the lobes. However, smaller leaf-like ensembles of axons that reveal particularly high affinities to anti-aspartate are embedded within taurine-positive laminae and occur in the immunonegative laminae between them. Together, these arrangements reveal a complex architecture of repeating subunits whose different levels of immunoreactivity correspond to broader immunoreactive layers identified by sera against the neuromodulator FMRFamide. Throughout development and in the adult, the most posterior lamina is glutamate immunopositive. Its axons arise from the most recently born Kenyon cells that in the adult retain their juvenile character, sending a dense system of collaterals to the front of the lobes. Glutamate-positive processes intersect aspartate- and taurine-immunopositive laminae and are disposed such that they might play important roles in synaptogenesis or synapse modification. Glutamate immunoreactivity is not seen in older, mature axons, indicating that Kenyon cells show plasticity of neurotransmitter phenotype during development. Aspartate may be a universal transmitter substance throughout the lobes. High levels of taurine immunoreactivity occur in broad laminae containing the high concentrations of synaptic vesicles. J. Comp. Neurol. 439: 352‐367, 2001. © 2001 Wiley-Liss, Inc. Indexing terms: amino acid immunoreactivity; glutamate; brain parcellation; insect; learning and memory

Development of laminar organization in the mushroom bodies of the cockroach: Kenyon cell proliferation, outgrowth, and maturation.

Abstract: The mushroom bodies of the insect brain are lobed integration centers made up of tens of thousands of parallel-projecting axons of intrinsic (Kenyon) cells. Most of the axons in the medial and vertical lobes of adult cockroach mushroom bodies derive from class I Kenyon cells and are organized into regular, alternating pairs (doublets) of pale and dark laminae. Organization of Kenyon cell axons into the adult pattern of laminae occurs gradually over the course of nymphal development. Newly hatched nymphs possess tiny mushroom bodies with lobes containing a posterior lamina of ingrowing axons, followed by a single doublet, which is flanked anteriorly by a γ layer composed of class II Kenyon cells. Golgi impregnations show that throughout nymphal development, regardless of the number of doublets present, the most posterior lamina serves as the “ingrowth lamina” for axons of newborn Kenyon cells. Axons of the ingrowth lamina are taurine- and synaptotagmin-immunonegative. They produce fine growth cone tipped filaments and long perpendicularly oriented collaterals along their length. The maturation of these Kenyon cells and the formation of a new lamina are marked by the loss of filaments and collaterals, as well as the onset of taurine and synaptotagmin expression. Class I Kenyon cells thus show plasticity in both morphology and transmitter expression during development. In a hemimetabolous insect such as the cockroach, juvenile stages are morphologically and behaviorally similar to the adult. The mushroom bodies of these insects must be functional from hatching onward, while thousands of new neurons are added to the existing structure. The observed developmental plasticity may serve as a mechanism by which extensive postembryonic development of the mushroom bodies can occur without disrupting function. This contrasts with the more evolutionarily derived holometabolous insects, such as the honey bee and the fruit fly, in which nervous system development is accomplished in a behaviorally simple larval stage and a quiescent pupal stage. J. Comp. Neurol. 430:331–351, 2001. © 2001 Wiley-Liss, Inc.

Exploitation of an ancient escape circuit by an avian predator: relationships between taxon-specific prey escape circuits and the sensitivity to visual cues from the predator.

Abstract: The painted redstart Myioborus pictus uses visual displays to flush, pursue, and then capture an abundance of brachyceran Diptera that are equipped with giant fiber escape circuits. This paper investigates the relationships between features of the giant fiber system, the structure of visual stimuli produced by redstarts and their effectiveness in eliciting escape reactions by flies. The results show that dipterous taxa having large-diameter giant fibers extending short distances from the brain to motor neurons involved in escape are flushed at greater distances than taxa with longer and small-diameter giant fibers. The results of behavioral tests show the importance of angular acceleration of expanding image edges on the compound eye in eliciting escape responses. Lateral motion of stimulus profile edges as well as structured visual profiles additionally contribute to the sensitivity of one or more neural systems that trigger escape. Retinal subtense and angular velocity are known to trigger physiological responses in fly giant fiber circuits, but the contributions of edge length and lateral motion in a looming stimulus suggest that escape pathways might also receive inputs from circuits that are tuned to different types of motion. The present results suggest that these several properties of escape pathways have contributed to the evolution of foraging displays and plumage patterns in flush-pursuing birds.

Learned discrimination of pattern orientation in walking flies

Abstract: To determine the pattern-orientation discrimination ability of blowflies, Phaenicia sericata, a learning/memory assay was developed in which sucrose served as the reward stimulus and was paired with one of two visual gratings of different orientations. Individual, freely walking flies with clipped wings were trained to discriminate between pairs of visual patterns presented in the vertical plane. During training trials, individual flies learned to search preferentially at the rewarded stimulus. In subsequent testing trials, flies continued to exhibit a learned preference for the previously rewarded stimulus, demonstrating an ability to discriminate between the two visual cues. Flies learned to discriminate between horizontal and vertical gratings, +45 ° (relative to a 0 ° vertical) and -45 ° gratings, and vertical and +5 ° gratings. Individual patterns of learning and locomotive behavior were observed in the pattern of exploration during training trials. The features of the visual cue critical for discrimination of orientation are discussed. Summary

Pathways in Dipteran Insects for Early Visual Motion Processing

Abstract: In insects, as in vertebrates, neuroanatomical, electrophysiological, and modelling studies have provided insights regarding identities and connections among neurones that accomplish elementary motion detection. These studies include intracellular recordings from identified wide-field neurones that collate local information about motion, intracellular recordings from identified, mainly non-spiking small-field neurones that are candidates for a cardinal role in motion detection, and comparative anatomical studies of retinotopic neurones that are evolutionarily conserved across taxa. Nevertheless, many important features of motion processing in insects have yet to be revealed. This review concentrates on two questions: what are the identities and relationships among neurones that participate in elementary motion detection? And, are there distinct functional classes of elementary motion detectors (EMDs) in insects?