Phase-based control of the central pattern generator for locomotion

We have previously shown that the lamprey´s central pattern generator (CPG) for locomotion can be manipulated by applying electrical stimuli to the spinal cord at precise phases within the CPG cycle. Here we demonstrate how these so-called phase dependent responses (PDR) can be used to repeatably and reliably manipulate individual parameters of locomotion in the lamprey. In particular, we show that: (1) the PDR for an arbitrary stimulus prescribes the phases at which to stimulate in order to effect specific modifications of the locomotor output; (2) ipsilateral and contralateral burst lengths can be controlled separately; and (3) the responses predicted by a single-cycle PDR plot remain stable over many cycles of stimulation. All of these properties suggest that phase-dependent stimulation may be an effective means of controlling the CPG in a future spinal locomotion neuroprosthesis.