Figure 2.

When tonic levels of excitation and inhibition, the substrate for push–pull control, are present, maximum depolarization (and maximum firing frequencies) is achieved when disinhibition is coupled with excitation. Similarly, maximum hyperpolarization is achieved by the coupling of disfacilitation with inhibition. In our experiments, this was tested by having either an intact Ia reciprocal inhibition system or by disrupting reciprocal inhibition by cutting the tendons to antagonist muscles.