Fig. 6.

Responses of NS neurons as a function of the spike frequency in the motoneuron. A, Representative recordings of an NS neuron to the activation of a CV motoneuron. Thetwo top traces correspond to a CV motoneuron, which was induced to fire at two different frequencies (indicated under thetraces) by the application of square current pulses (indicated by the square step lines ontop). The superimposed traces on thebottom correspond to the respective responses of the NS neuron. Black and gray traces indicate the corresponding recording pairings. B, Amplitude of the NS response as a function of the spike frequency of the motoneurons, stimulated with current steps of 0.5, 1, 1.5, and 2 nA. Firing frequencies were normalized to the one observed in response to the smallest current step (0.5 nA). Open symbolsrepresent five CV motoneurons; filled symbols represent four AE motoneurons. The curves are weighted fittings using the locally weighted least squared error method performed with Kaleidagraph.Broken line indicates CV data; solid lineindicates AE data.