Fig. 9.

Interaction of brainstem descending pathways with commissural circuits in the primate. A: intracellular records of responses of a motoneuron from the lower cervical cord in a primate. The green trace shows the mean response to stimulation of the brainstem descending pathways alone (train of 3 shocks), the red trace shows the response to stimulation of the contralateral spinal cord (cISMS) while the blue trace shows the response to combined brainstem and cISMS stimulation. The black trace underneath shows the net response to the cISMS after brainstem responses have been subtracted. Note the presence of the excitatory postsynaptic potential (EPSP) to cISMS that was absent to cISMS stimulation alone (red). The black triangles indicate the time of brainstem stimulation and the gray arrow shows the time of spinal stimulation. B: same as A but for a different motoneuron (MN). C: schematic showing the stimulated pathways and circuits that could be mediating the conditioned response. CIN, commissural interneuron; RST, reticulospinal tract. Modified from Soteropoulos et al. (2013).