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Changes in locomotor activity parameters with variations in cycle time in larval lamprey
Division of Biological Sciences and Interdisciplinary Neuroscience Program, University of Missouri, Columbia, MO 65211-6190, USA
Author for correspondence (e-mail: McclellanA{at}missouri.edu)
Accepted 11 September 2002
In larval lamprey, locomotor activity recorded from whole animals and
in vitro brain/spinal cord preparations was analyzed to determine how
two parameters of locomotor activity, burst proportion (BP; relative duration
of motor burst activity) and intersegmental phase lag (
; normalized delay
of burst activity along one side of the body), vary with changes in cycle time
(T). In individual animals, the slopes of BP and
versus
T were compared using linear regression analysis, followed by statistical
analysis of the slopes to determine whether the parameters changed
significantly with variations in cycle time.
For locomotor muscle activity in whole animals, the BP values increased
significantly with decreases in T (i.e. negative slopes), while the
slopes for
values versus T were not significantly different
from zero. For locomotor activity in preparations in vitro, the mean
slopes for BP values versus T, although negative, were not
significantly different from zero, and phase lags were also relatively
constant with changes in cycle time.
Increases in BP with decreases in cycle time and increases in swimming speed can be expected to generate proportionately more force per cycle, presumably to compensate for the increase in viscous resistance of moving the body more rapidly through water. By contrast, constant intersegmental phase lags will ensure that the relative timing of locomotor burst activity is constant and that an approximately single S-wave along the body is retained during different swimming speeds.
Key words: central pattern generator, coordination, phase lag, oscillator, swimming, lamprey
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