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Author Notes:

Email Address: awennin@emory.edu

A.W., B.J.N., and R.L.C. conception and design of research; A.W., B.J.N., and A.D.-M. performed experiments; A.W., A.D.-M., and R.L.C. analyzed data.

A.W., B.J.N., and R.L.C. interpreted results of experiments; A.W. prepared figures; A.W. drafted manuscript.

A.W. and R.L.C. edited and revised manuscript; A.W., B.J.N., A.D.-M., and R.L.C. approved final version of manuscript.

We thank our colleagues Drs. D. G. Lamb for helping with MATLAB coding, D. R. Stokes for designing a device for imaging adult leeches, D. Kueh for advising on statistics, and C. Günay for reading an earlier version of this manuscript.

Eugenia Botezat assisted with the imaging and the subsequent analysis.

No conflicts of interest, financial or otherwise, are declared by the author(s).


Research Funding:

This work was supported by National Institute of Neurological Disorders and Stroke Grant R01 NS-085006 to R. L. Calabrese.


  • motor pattern in vivo
  • motor performance
  • intersegmental coordination
  • variability
  • leech

Variation in motor output and motor performance in a centrally generated motor pattern


Journal Title:

Journal of Neurophysiology


Volume 112, Number 1


, Pages 95-109

Type of Work:

Article | Final Publisher PDF


Central pattern generators (CPGs) produce motor patterns that ultimately drive motor outputs. We studied how functional motor performance is achieved, specifically, whether the variation seen in motor patterns is reflected in motor performance and whether fictive motor patterns differ from those in vivo. We used the leech heartbeat system in which a bilaterally symmetrical CPG coordinates segmental heart motor neurons and two segmented heart tubes into two mutually exclusive coordination modes: rear-to-front peristaltic on one side and nearly synchronous on the other, with regular side-to-side switches. We assessed individual variability of the motor pattern and the beat pattern in vivo. To quantify the beat pattern we imaged intact adults. To quantify the phase relations between motor neurons and heart constrictions we recorded extracellularly from two heart motor neurons and movement from the corresponding heart segments in minimally dissected leeches. Variation in the motor pattern was reflected in motor performance only in the peristaltic mode, where larger intersegmental phase differences in the motor neurons resulted in larger phase differences between heart constrictions. Fictive motor patterns differed from those in vivo only in the synchronous mode, where intersegmental phase differences in vivo had a larger front-to-rear bias and were more constrained. Additionally, load-influenced constriction timing might explain the amplification of the phase differences between heart segments in the peristaltic mode and the higher variability in motor output due to body shape assumed in this soft-bodied animal. The motor pattern determines the beat pattern, peristaltic or synchronous, but heart mechanics influence the phase relations achieved.

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© 2014 the American Physiological Society

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