Fig. 14 Block diagram of the dual-mode version subsystem with vestibular input illustrates the use of an internal monitor (IM), which feeds back the eye position command (θE CMD) and eye velocity command (dθE/dt CMD) to generate an efferent copy of eye position in the head (☐☐'E☐H) and eye velocity in the head (d☐'E☐H/dt). These signals sum with retinal error and retinal error velocity to produce an efferent copy of target position in space (θ'T) and target velocity in space (dθ'T/dt). Eye position and velocity in the head combine with head position and velocity respectively to produce eye position and velocity in space (θEH + θH = θES and dθEH/dt + dθH/dt = dθES/dt). The other symbols in this figure are identical to those in Figure 11.