Figure 4. Memantine induces saccades with a large vertical component.

(A) Representative eye movements in response to rotating black and white stripes before or after 30 mg/kg i.p. memantine. Predrug saccades are confined largely to the horizontal (x) axis, whereas postmemantine saccades also have a large vertical (y) component. Scale bar: 0.5 mm. (B) The number of saccades during alternating 30-second moving visual stimulus and rest (null stimulus) periods, as defined in Figure 1. Memantine induces spontaneous saccades during the rest periods but has little effect on saccade frequency in response to a visual stimulus. (C) Saccade amplitudes and 2-dimensional trajectories (as defined in A) before and after memantine in response to clockwise (CW) or counterclockwise (CCW) rotating visual stimuli or in the absence of a moving stimulus (null). After memantine injection, large vertical components are common in response to CCW motion and among spontaneous eye movements. Data in B are averages from 3 mice; data in C are from a single representative mouse.