Fig. 2.

Horizontal eye velocity vs. time during leftward (positive) and rightward (negative) yaw-axis velocity steps (0–80°/s) in the normal, plugged, and prosthesis-on states. The amplitude of the step response was symmetric in the normal state in both monkeys, although monkey N again demonstrated a positive bias due to spontaneous nystagmus in the dark. After the prosthesis was activated, both animals show evidence of a small VOR bias due to the residual spontaneous nystagmus that was present after 30 min of tonic stimulation in the dark. The small bias (∼2°/s) is negative (rightward) in monkey S due to left ear stimulation and is positive (leftward) in monkey N due to right ear stimulation.