ABSTRACT
The trochlear nerve was localized by microelectrode recordings, and stimulation was given through the same microelectrode. Stimulation trains consisted of 0.25 ms negative rectangular pulses. Electrical microstimulation of the trochlear nerve produced unilateral eye movements whose initial trajectories deviated clearly from the expected anatomical pulling direction in the orbit. The eye position dependence becomes more pronounced during the course of stimulation. A more precise description of trochlear stimulation experiments requires a detailed analysis of the movement trajectory, time constants of return to the starting position after cessation of the stimulus, and comparison with known mechanical characteristics of muscles and other orbital tissue. To demonstrate details of movement direction as a function of time after onset of stimulation, a long stimulus time of 140 ms was chosen deliberately. Latencies between stimulus and eye movement onset were stereotypically 6 ms for suprathreshold stimulation.
