Motor flexibility in insects: adaptive coordination of limbs in locomotion and near-range exploration
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In recent years, research on insect motor behaviour―locomotion in particular―has provided a number of important new insights, many of which became possible because of methodological advances in motion capture of unrestrained moving insects. Behavioural analyses have not only backed-up neurophysiological analyses of the underlying mechanisms at work, they have also highlighted the complexity and variability of leg movements in naturalistic, unrestrained behaviour. Here, we argue that the variability of unrestrained motor behaviour should be considered a sign of behavioural flexibility. Assuming that variation of movement-related parameters is governed by neural mechanisms, behavioural analyses can complement neurophysiological investigations, for example by (i) dissociating distinct movement episodes based on functional and statistical grounds, (ii) quantifying when and how transitions between movement episodes occur, and (iii) dissociating temporal and spatial coordination. The present review emphasises the importance of considering the functional diversity of limb movements in insect behaviour. In particular, we highlight the fundamental difference between leg movements that generate interaction forces as opposed to those that do not. On that background, we discuss the spatially continuous modulation of swing movements and the quasi-rhythmic nature of stepping across insect orders. Based on examples of motor flexibility in stick insects, we illustrate the relevance of behaviour-based approaches for computational modelling of a rich and adaptive movement repertoire. Finally, we emphasise the intimate interplay of locomotion and near-range exploration. We propose that this interplay, through continuous integration of distributed, multimodal sensory feedback, is key to locomotor flexibility.
KeywordsInsect Motor behaviour Leg coordination Gait Sensory feedback
The authors thank the students of the “control of behaviour” master course 2016 and Bianca Jaske for collecting data on free walking insects. Part of these data was used for Fig. 1a, and Fig. 2b. Moreover, we thank two anonymous reviewers for their helpful comments and suggestions, and Yannick Günzel for his assistance in data management and analysis. This work was supported by the cluster of excellence 277, CITEC, funded by of the German Research Council, DFG.
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Conflict of interest
The authors declare that they have no conflict of interest.
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