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This Article Full Text Full Text (PDF) All Versions of this Article: 102/2/1180    most recent 00257.2009v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Web of Science (1) Google Scholar Articles by Gruhn, M. Articles by Borgmann, A. PubMed PubMed Citation Articles by Gruhn, M. Articles by Borgmann, A.

Control of Stepping Velocity in the Stick Insect Carausius morosus

Department of Animal Physiology, Zoological Institute, University of Cologne, Cologne, Germany

Submitted 23 March 2009; accepted in final form 11 June 2009

We performed electrophysiological and behavioral experiments in single-leg preparations and intact animals of the stick insect Carausius morosus to understand mechanisms underlying the control of walking speed. At the level of the single leg, we found no significant correlation between stepping velocity and spike frequency of motor neurons (MNs) other than the previously shown modification in flexor (stance) MN activity. However, pauses between stance and swing motoneuron activity at the transition from stance to swing phase and stepping velocity are correlated. Pauses become shorter with increasing speed and completely disappear during fast stepping sequences. By means of extra- and intracellular recordings in single-leg stick insect preparations we found no systematic relationship between the velocity of a stepping front leg and the motoneuronal activity in the ipsi- or contralateral mesothoracic protractor and retractor, as well as flexor and extensor MNs. The observations on the lack of coordination of stepping velocity between legs in single-leg preparations were confirmed in behavioral experiments with intact stick insects tethered above a slippery surface, thereby effectively removing mechanical coupling through the ground. In this situation, there were again no systematic correlations between the stepping velocities of different legs, despite the finding that an increase in stepping velocity in a single front leg is correlated with a general increase in nerve activity in all connectives between the subesophageal and all thoracic ganglia. However, when the tethered animal increased walking speed due to a short tactile stimulus, provoking an escape-like response, stepping velocities of ipsilateral legs were found to be correlated for several steps. These results indicate that there is no permanent coordination of stepping velocities between legs, but that such coordination can be activated under certain circumstances.

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				G. von Uckermann and A. Buschges Premotor Interneurons in the Local Control of Stepping Motor Output for the Stick Insect Single Middle Leg J Neurophysiol, September 1, 2009; 102(3): 1956 - 1975. [Abstract] [Full Text] [PDF]