Figure 5.

Facilitation of intraspinally evoked responses by interaction with MLF stimulation. A, B, Facilitation in two different motoneurons. A1, B1, Red trace shows response to cISMS alone (200 μA); blue trace when preceded by three stimuli to the cMLF stimulation (300 μA), which yielded small responses when delivered alone (green). Lower traces represent the difference between the response to combined stimulation, and to cMLF alone (black), with the response to cISMS alone overlain for comparison (red). A2, B2, Distribution of “net conditioning values” from bootstrapping analysis (see Materials and Methods). Although there were small responses to cISMS or cMLF alone, the combined stimulation produced a clear EPSP. Motoneurons were identified as projecting to the following: A, a forearm extensor muscle; B, a forearm flexor muscle.