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Harris, Christian M., Szczecinski, Nicholas S., Bueschges, Ansgar and Zill, Sasha N. (2022). Sensory signals of unloading in insects are tuned to distinguish leg slipping from load variations in gait: experimental and modeling studies. J. Neurophysiol., 128 (4). S. 790 - 808. Rockville: AMER PHYSIOLOGICAL SOC. ISSN 1522-1598

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Abstract

In control of walking, sensory signals of decreasing forces are used to regulate leg lifting in initiation of swing and to detect loss of substrate grip (leg slipping). We used extracellular recordings in two insect species to characterize and model responses to force decrements of tibial campaniform sensilla, receptors that detect forces as cuticular strains. Discharges to decreasing forces did not occur upon direct stimulation of the sites of mechanotransduction (cuticular caps) but were readily elicited by bending forces applied to the leg. Responses to bending force decreases were phasic but had rate sensitivities similar to discharges eli-cited by force increases in the opposite direction. Application of stimuli of equivalent amplitude at different offset levels showed that discharges were strongly dependent upon the tonic level of loading: firing was maximal to complete unloading of the leg but substantially decreased or eliminated by sustained loads. The contribution of cuticle properties to sensory responses was also evaluated: discharges to force increases showed decreased adaptation when mechanical stress relaxation was minimized; firing to force decreases could be related to viscoelastic creep in the cuticle. Discharges to force decrements apparently occur due to cuticle viscoelasticity that generates transient strains similar to bending in the opposite direction. Tuning of sensory responses through cuticular and membrane properties effectively distinguishes loss of substrate grip/complete unloading from force variations due to gait in walking. We have successfully reproduced these properties in a mathematical model of the recep-tors. Sensors with similar tuning could fulfil these functions in legs of walking machines.NEW & NOTEWORTHY Decreases in loading of legs are important in the regulation of posture and walking in both vertebrates and invertebrates. Recordings of activities of tibial campaniform sensilla, which encode forces in insects, showed that their responses are specifically tuned to detect force decreases at the end of the stance phase of walking or when a leg slips. These results have been reproduced in a mathematical model of the receptors and also have potential applications in robotics.

Item Type:	Journal Article
Creators:	Creators Email ORCID ORCID Put Code Harris, Christian M. UNSPECIFIED UNSPECIFIED UNSPECIFIED Szczecinski, Nicholas S. UNSPECIFIED UNSPECIFIED UNSPECIFIED Bueschges, Ansgar UNSPECIFIED UNSPECIFIED UNSPECIFIED Zill, Sasha N. UNSPECIFIED UNSPECIFIED UNSPECIFIED
URN:	urn:nbn:de:hbz:38-672029
DOI:	10.1152/jn.00285.2022
Journal or Publication Title:	J. Neurophysiol.
Volume:	128
Number:	4
Page Range:	S. 790 - 808
Date:	2022
Publisher:	AMER PHYSIOLOGICAL SOC
Place of Publication:	Rockville
ISSN:	1522-1598
Language:	English
Faculty:	Unspecified
Divisions:	Unspecified
Subjects:	no entry
Uncontrolled Keywords:	Keywords Language TIBIAL CAMPANIFORM SENSILLA; GLABROUS SKIN; BODY LOAD; AMERICAN COCKROACH; STANCE PHASE; STICK INSECT; SWING PHASE; WALKING; FORCE; MECHANORECEPTORS Multiple languages Neurosciences; Physiology Multiple languages
URI:	http://kups.ub.uni-koeln.de/id/eprint/67202