Location: HSB G-328, 10:30am (unless otherwise noted)
February 13, 2014
Martha Bagnall, Ph.D. , Northwestern University
Host: Stan Froehner
The evolutionary transition from the simple swimming rhythms of fish to more complicated motor patterns of tetrapods implies a major diversification of locomotor circuitry in the spinal cord. It remains unclear how axial spinal circuits for left/right alternation could have given rise to complex tetrapod networks required for walking. Using physiological recordings from motor neuron pairs in vivo, here we show that in fact, the zebrafish spinal cord contains two parallel, distinct microcircuits for independent control of dorsal and ventral musculature on each side of its body. During normal upright swimming, the dorsal and ventral microcircuits are equally active; but during postural correction, fish differentially engage these microcircuits to generate torque for self-righting. These findings reveal greater complexity in the fish spinal networks responsible for swimming than previously recognized. We suggest that these parallel microcircuits in early vertebrates represent a plausible template for the evolution of limb control in tetrapods.