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. Author manuscript; available in PMC: 2020 Jun 24.
Published in final edited form as: Clin Neurophysiol. 2009 Sep 27;120(12):2040–2054. doi: 10.1016/j.clinph.2009.08.009

Figure 5.

Figure 5

The effect of synaptic input on the input-output function of a motor pool and the muscle that it innervates, based on computer simulations of data for the feline medial gastrocnemius pool and muscle (Heckman and Binder, 1991, 1993a, b). The base state is simulated from data obtained in preparations where brainstem neuromodulatory input is suppressed and all motoneurons receive exactly equal proportions of synaptic input. The “Max ionotropic” effect is based the maximum sub-threshold depolarization that can be achieved without producing any motor unit recruitment and a distribution of input that favors high over low threshold units. This distribution was set as non-uniformly as possible with the the constraint that recruitment reversals should not exceed about 20% (Heckman and Binder, 1993b). Medium and Max neuromodulatory effects are based on studies where the brainstem is highly active and where this activity is supplemented by an exogenous monoaminergic agonist (Lee and Heckman, 1998a, b, 1999a).