Delcomyn F. & Cocatre-Zilgien J.H. (1988). Individual differences and
variability in the timing of motor activity during walking in insects. Biol.
Cybern. 59:379-384.
Abstract. The uniformity of the neural physiology of an animal population is a
fundamental, rarely tested assumption in most neurophysiological work. In this
study, the variability of the timing between the movement of pairs of legs
during free walking in cockroaches was assessed. Phases (a measure of timing) of
motor bursts in muscles of legs in the American cockroach, Periplaneta
americana, were calculated for insects walking straight over a flat level
surface. Student's t, Wallraff, Mann Whitney and Watson U2 two-sample tests were
used to compare the phases of motor bursts of the same pairs of legs in
different insects. The comparisons showed that in spite of the homogeneity both
of the animal population and of the conditions under which the insects walked,
most of the inter-leg phases of the animals that were compared were
significantly different statistically. Further testing of greater numbers of
insects using analysis of variance to test for population uniformity confirmed
that the insects we tested were not members of a single statistical population
with respect to the timing of motor bursts of the legs during walking. We infer
that this unexpectedly large variability in a population thought to be
relatively homogeneous reflects subtle but biologically significant differences
between animals. The possible sources of these differences and their
consequences for the study of behavior and its physiological basis are
discussed.
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