Figure 4.

Histograms of single-unit activity of a cell representing a minority of floccular VA Purkinje cells for which the SSs fire in phase with the CSs. The cell was recorded during three different stimulus conditions as in Figure 3: vestibular stimulation in the light (column 1), optokinetic stimulation (column 2), and vestibular stimulation in the dark (column 3). The stimulus frequency was 1.0 Hz. A, Average angular velocity of the head (black line), the slow-phase eye movement (gray line), and the residual retinal image slip (light-gray dashed line). B, Average CS firing rate. C, Average simple spike firing rate. The amplitude of the optokinetic stimulus (A₂, black dashed line) was set to 3.5°/s, so that the magnitude of the retinal image slip (light gray dashed line) approximately matched that of the slip during vestibular stimulation in the light (A₁).