Fig. 2.

Impairment of probe trial performance in R6/2 mice. During the probe trials, R6/2 and control groups spent significantly >25% of their time in the platform quadrant, indicating that all mice had learned the platform location (A). The implications of A are refuted by the observation that R6/2 mice crossed what had been the exact location of the platform significantly less frequently than did controls (B) and furthermore that R6/2 mice did not show a preference for platform crossings over equivalent sites in the other quadrants. R6/2 mice spent significantly more time in the peripheral outer pool zone and significantly less time in the middle pool zone relative to control mice (C).Vertical bars indicate the SEM. Asterisksindicate significant preferences between measures (**p < 0.01).