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Encoding properties of the wing hinge stretch receptor in the hawkmoth Manduca sexta
University of Washington, Department of Zoology, Box 351800, Seattle, WA 98195-1800, USA
Present address: Department of Integrative Biology, University of California, Berkeley, CA 94720, USA (e-mail: markfrye{at}socrates.berkeley.edu)
Accepted August 8, 2001
To characterize the in vivo responses of the wing hinge stretch receptor of Manduca sexta, I recorded its activity and simultaneously tracked the up-and-down motion of the wing while the hawkmoth flew tethered in a wind tunnel. The stretch receptor fires a high-frequency burst of spikes near each dorsal stroke reversal. The onset of the burst is tightly tuned to a set-point in wing elevation, and the number of spikes contained within the burst encodes the maximal degree of wing elevation during the stroke. In an effort to characterize its mechanical encoding properties, I constructed an actuator that delivered deformations to the wing hinge and simultaneously recorded the resultant stretch and tension and the activity of the stretch receptor. Stimuli included stepwise changes in length as well as more natural dynamic deformation that was measured in vivo. Step changes in length reveal that the stretch receptor encodes the static amplitude of stretch with both phasic and tonic firing dynamics. In vivo sinusoidal deformation revealed (i) that the timing of stretch receptor activity is tightly phase-locked within the oscillation cycle, (ii) that the number of spikes per burst is inversely related to oscillation frequency and (iii) that the instantaneous frequency of the burst increases with oscillation rate. At all oscillation rates tested, the instantaneous frequency of the burst increases with amplitude.
Key words: insect, flight, mechanosensory, proprioception, hawkmoth, Manduca sexta.
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  M. A. Frye Effects of stretch receptor ablation on the optomotor control of lift in the hawkmoth Manduca sexta J. Exp. Biol., January 11, 2001; 204(21): 3683 - 3691. [Abstract] [Full Text] [PDF]
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