EXAMPLE OF 2 1 INTERLIMB COORDINATION DURING FICTIVE ROSTRAL SCRATCHING IN A SPINAL TURTLE/

The usual interlimb coordination pattern during fictive rostral scratc hing in turtles is 1:1 coordination. We describe an example in a turtl e of 2:1 coordination during fictive rostral scratching in which there were two cycles of ipsilateral hip flexor activity during each cycle of contralateral hip extensor activity. During 2:1 coordination, there were fluctuations in the ipsilateral hip flexor cycle period such tha t a larger ipsilateral hip flexor normalized period, which was associa ted with the onset of a contralateral hip extensor burst, alternated w ith a smaller ipsilateral hip flexor normalized period, which was asso ciated with the absence of the onset of a contralateral hip extensor b urst. These observations support the concept that contralateral circui try modulates the timing of ipsilateral motor rhythms and therefore co ntributes to the production of the ipsilateral motor pattern for rostr al scratching.