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. 2014 Oct 2;9(10):e109205. doi: 10.1371/journal.pone.0109205

Figure 9. Response of a motoneuron pool to periodic stimulation from a CPG and neuromodulation.

Figure 9

50 uncoupled motoneurons are simulated, each receiving constant input I app = 2 µA/cm2 mimicking the excitability effects of neuromodulators such as serotonin, and periodic stimulation from a CPG with a frequency f = 10 Hz. The periodic stimulation is I c = 0.15 µA/cm2 during the first 20 ms of each cycle with a duration of T per = 1/f, and 0 otherwise. Different neurons have different noise realizations. Additional parameters: g h = 0.3 mS/cm2, σ = 0.032 µA×ms1/2/cm2. Realizations of the noise are different across motoneurons. (A) The membrane potential V as a function of t for two neurons (black). The stimulus pattern is schematically plotted above each panel (red) to emphasize the synchrony of spikes with the stimulus. (B) Rastergram of the spikes (black circles) of the 50 motoneurons. The stimulus is I c between each pair of adjacent red lines. (C) The total force amplitude F, in arbitrary units (A = 1, Equation 4), generated by a whole muscle whose cells are innervated by the pool of motoneurons (black). The dotted blue line denotes a similar simulation with I app = 2.4 µA/cm2.