Journal of Comparative Physiology A

, Volume 194, Issue 3, pp 283–298

Interaction between descending input and thoracic reflexes for joint coordination in cockroach: I. Descending influence on thoracic sensory reflexes

Original Paper

DOI: 10.1007/s00359-007-0307-x

Cite this article as:
Mu, L. & Ritzmann, R.E. J Comp Physiol A (2008) 194: 283. doi:10.1007/s00359-007-0307-x
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Abstract

Tethered cockroaches turn from unilateral antennal contact using asymmetrical movements of mesothoracic (T2) legs (Mu and Ritzmann in J Comp Physiol A 191:1037–1054, 2005). During the turn, the leg on the inside of the turn (the inside T2 leg) has distinctly different motor patterns from those in straight walking. One possible neural mechanism for the transformation from walking to inside leg turning could be that the descending commands alter a few critical reflexes that start a cascade of physical changes in leg movement or posture, leading to further alterations. This hypothesis has two implications: first, the descending activities must be able to influence thoracic reflexes. Second, one should be able to initiate the turning motor pattern without descending signals by mimicking a point farther down in the reflex cascade. We addressed the first implication in this paper by experiments on chordotonal organ reflexes. The activity of depressor muscle (Ds) and slow extensor tibia muscle (SETi) was excited and inhibited by stretching and relaxing the femoral chordotonal organ. However, the Ds responses were altered after eliminating the descending activity, while the SETi responses remain similar. The inhibition to Ds activity by stretching the coxal chordotonal organ was also altered after eliminating the descending activity.

Keywords

Thoracic reflex Descending input Chordotonal organ Joint coordination Cockroach 

Abbreviations

CCO

Coxal chordotonal organ

CoCL

Circumoesophageal connectives lesion

CTr

Coxa-trochanter

Ds

Depressor trochanter neuron

EMG

Electromyogram

FCO

Femoral chordotonal organ

FTi

Femur–tibia

NL

Neck lesion

SETi

Slow extensor tibia neuron

SOG

Suboesophageal ganglion

T2

Mesothoracic

ThC

Thorax–coxa

Copyright information

© Springer-Verlag 2007

Authors and Affiliations

  1. 1.Department of BiologyCase Western Reserve UniversityClevelandUSA

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