Sensory processing, perception and communication in simple nervous systems

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My research program seeks to integrate studies of natural behaviour and its adaptive constraints with analyses of underlying neural mechanism to address fundamental and practical questions in the following areas. A. Common principles for integration of cues in sensory orientation tasks. B. Simple models of sensory perception. C. Relationship between sensory ecology and signal complexity in communication. Specific objectives for this proposal: 1. Insect auditory processing. 1a. Parasitoid flies (Ormia sp.) find hosts by localizing the songs of male crickets with directional hearing of unsurpassed accuracy. Current work addresses novel dimensions of hearing in this system, including plasticity, elevation sensitivity (3D localization), and near-field hearing in the context of larviposition (a distinct behavioural context following long-range phonotaxis). 1b. Plasticity and population divergence in stimulus recognition. Geographically distinct Ormia populations exploit locally specific host species varying in song characteristics relevant to host recognition and phonotaxis. A quantitative measure of signal preference allows standardized comparisons across populations to quantify host-specific divergence. Field work on three populations (FL, TX, CA) is extending these comparative studies to include ecological variables (predation; host density) that may contribute to divergence of host-foraging strategies among fly populations. 2. Vibrational sensory signals. Details of coding, recognition, and localisation of vibration stimuli by spiders are primarily known from work on few species. There is considerable variation in the structure of webs and material properties of silk, and growing interest in the relationship between these factors and the propagation and processing of vibration stimuli. Proposed work on cobweb-dwelling widow spiders will examine mechanical properties of webs and silk; characterise vibration signals and cues (prey vs conspecifics) and link these to variation in signal propagation as a function of web properties. 3. Evolution of communication and signal complexity. 3a. Competitive signals. This work is focused the role of signal costs in communication and competition, using the orthopteran insects and jumping spiders. I will continue on-going work on metabolic costs of signalling by correlating measures of energy consumption (respirometry) with individual variation in competitive success and signal quality (acoustic signals in insects; vibratory signals in spiders). 3b. Vibrational signal structure. Current work on widow spiders documents a progression from haphazard to structured signals within a single display sequence. They are therefore a good model for testing the functional significance of signal organization. Proposed work will integrate these behavioural studies with vibrosensory work (2) for an integrative study of the sensory ecology of vibrational signals (from physical constraints, to sensory coding, to behaviour).