Strong interactions between spinal cord networks for scratching and swimming:
When a scratch stimulation and a swim stimulation were delivered at overlapping times, the resulting motor patterns revealed strong interactions between the two networks or a shared rhythm-generating network. For example, the frequency of the rhythmic motor pattern during combined stimulation was often faster than during either single stimulation, suggesting that scratch and swim inputs are integrated at some stage prior to rhythmic motor neuron activity (right,
A: rostral scratching alone-red bar, B: forward swimming alone-blue bar; C: combined stimulation-pink shading; D: rhythm frequencies in this animal; E: rhythm frequencies in another animal; KE, HF,
and HE are knee extensor, hip flexor, and hip extensor motor nerves,
respectively; Stim., stimulation; R Sc, rostral scratching; Sw, forward swimming; * indicates statistical significance; error bars are SD). In addition, combined stimulation could evoke blends of scratching and swimming motor patterns, recruit a swim motor pattern when the swim stimulation was reduced to subthreshold intensity, or disrupt rhythm generation entirely.
(Adapted from
Hao, Z.-Z., Spardy, L.E., Nguyen, B.L., Rubin, J.E., and Berkowitz, A. J.
Neurophysiol.
106:1766-1781,
2011.)