Figure 1. Spontaneous network activity recorded from E12–14 mice.

A, suction electrodes were placed on embryonic mouse motor nerves in an isolated spinal cord-hindlimb preparation. B, spontaneous activity consists of episodic synchronous bursts of activity separated by several minutes. C, on occasion, localized bursts could occur that were not propagated to different muscle nerves. D, circuit diagram showing the postulated local circuit consisting of GABAergic interneurons and motoneurons. Motoneurons contribute to the onset and reinforcement of network activity via excitatory recurrent collaterals onto motoneurons and interneurons in the network. A separate glycinergic circuit is responsible for the propagation of the bursts. Data adapted from Hanson & Landmesser (2003) with permission.