Figure 9. Type II responses to passive and active sinusoidal movements.

A, example of type II 55-03 afferent to passive length changes of their parent muscle, the ulnar wrist extensor (UWE). B, cycle averages (see Fig. 8B and C) of recordings of type II afferents 55-01 and 55-03 both from UWE during passive and active sinusoidal wrist movements. In both conditions, type II afferents – in contrast to type Ia afferents – discharged while the velocity signal was positive even if the acceleration was negative. Dashed blue lines indicate zero crossings of velocity. Again note lack of apparent ‘length encoding’ during both passive and active conditions.