Elsevier

Brain Research

Volume 214, Issue 1, 9 June 1981, Pages 89-100
Brain Research

The crayfish lateral giants as command neurons for escape behavior

https://doi.org/10.1016/0006-8993(81)90440-6Get rights and content

Summary

The lateral giants (LGs) of the crayfish have often been described as command neurons. Recently, questions have arisen as to the definition of command neurons and as to whether the LGs are necessary for tailflips. We find that in an isolated abdomen preparation the LGs are necessary; temporarily blocking the LGs by hyperpolarization eliminates the tailflip flexor muscle output normally elicited by stimulation of the sensory afferents. However this demonstration of the LGs' necessity does not establish the LGs as the decision point of the behavior, for the LGs might be driven by a large input from a preceding decision neuron. We have checked for such an input by plotting the size of the EPSP produced in the hyperpolarized LG by various stimulus levels near spike threshold. We find no evidence for a large driving input near spike threshold. We conclude that the LGs have most of the features of command neurons.

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    Citation Excerpt :

    Here I suggest these structures were sensory, providing information to abdominal flexor and extensor circuits, as do segmental mechanoreceptors of the abdomen of the crayfish Pacifastacus leniusculus, thereby controlling abdominal posture (Leise et al., 1987). Tail-flip behavior would imply that associated giant fiber neurons driving this action (see Olson and Krasne, 1981) would have existed for at least 508 million years. Fossils of bent but unruptured Waptia abdomens, which may have tumbled about during burial, show curvature that suggests flexion of as much as 45° from horizontal could have been achieved, enough to provide an escape reaction and certainly enabling escape swimming, as occurs in shrimps today.

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