Neural pathways and neurogenesis in invertebrate nervous systems

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My long-term research in the nervous system is directed towards simple invertebrate nervous systems, to the circuits of identified nerve cells that provide the mechanism for adaptive behaviours. We will extend our understanding of the organisation of neural tissues, as well as enable the causal analysis of simple behaviours from the actions of identified nerve circuits. We will examine these in simple nervous systems, in the central nervous system (CNS) of the fruit fly Drosophila melanogaster, which provides access to powerful genetic molecules and tools, and in marine ancestors that shed light on our own origins on earth.A. In the fly's brain, we will use various forms of high-resolution electron microscopy to study circuits of neurons in: a) The lobes, output regions of the mushroom body (MB), a high-order integrative centre required for olfactory learning and memory. We will examine the stalk that innervates these, the development of constituent synaptic microcircuits, and how its intrinsic neurons change as a result of behavioural experience; b) the antennal lobe, where odours are encoded in the circuits of many small compartments called glomeruli. We will examine the microcircuits in identified glomeruli, from which MB input neurons derive, and changes after olfactory conditioning; c) the fly's biological clock centre; and d) the central brain, which is required for patterned behaviours such as singing and walking.B. In marine species, we will concentrate on the prototypical chordate CNS of the tadpole larva of the sea squirt. We will: a) examine the effects on swimming of damaging identified nerve cells; and b) the phenotypic determinism of the larval CNS, using larvae transfected with green fluorescent protein expressed under the promoters for neurotransmitter genes, concentrating on the motor innervation of the muscles underlying swimming and on variation between larvae. We will also map the cells of the CNS in a distantly related open sea species, using antibody labelling, confocal and electron microscopy and, depending on resources, compare those in both urochordates with the circuits in a spinal cord segment of larval lancelet.