Fig. 11. Two examples of the Fast assistance depressor motor neuron (Dep MN). (Ai) This Fast assistance (FA) neuron has sparse neurites and lacks branches in the anterior-lateral quadrant. It receives mono- (E) and polysynaptic EPSPs (P) as well as IPSPs (I). The orthodromic delay is 1.62 ms. (Aii) The neuron depicted in Ai depolarizes during the stretch phase of sinusoidal movement (mvt). In response to a ramp-and-hold stimulus the neuron strongly depolarizes phasically during stretches and weakly hyperpolarizes during releases. The resting membrane potential (dotted lines) was –69 mV. The response to sinusoidal movement is an average of 9 cycles triggered from the movement trace. The response to ramp-and-hold movement is an average of 5 cycles. (Bi) The morphology of this Fast assistance neuron is similar to that of the one shown to the left. In this particular experiment we did not record from other depressor motor neurons. Therefore, there is no histogram of spike amplitudes. The orthodromic delay is 2.3 ms. (Bii) The response of this neuron to movement is very similar to that of the neuron shown to the left. The resting membrane potential (dotted lines) was –50 mV. The response to sinusoidal movement is an average of 22 cycles triggered from the movement trace. The response to ramp-and-hold movement is an average of 13 cycles.