Isolation of the flexor center. A, Schematic diagram of the surgery. The box highlights the isolated part of the C2 segment (∼4 mm long). This region alone generated rhythmic elbow flexor EMG bursts through the C2 ventral root. The C2 dorsal root was cut, and the rest of the cord was removed.B, Rhythmic alternating flexor and extensor bursts were evident in the presence of NMDA (60 μm) before the isolation. The vertical dotted lines indicate the transition from flexor bursts to extensor bursts. The extensor bursts were totally abolished by the surgical isolation as indicated, whereas rhythmic flexor bursts remained.