Figure 3.

Effects of thalamic lesions on recent and remote spatial memory. A, Mean (±SEM) accuracy ratio for the probe trial in the three subgroups tested after a 5 d (left) or a 25 d (right) postacquisition delay. Performance is expressed as the accuracy ratio (see Materials and Methods; dashed line: chance). Significantly different from SHAM: *p < 0.01. Significantly different from ILN/LT: ¤p < 0.05. B, Mean (±SEM) number of crossings in the target area for the probe trial, at the 5 d (left) and 25 d (right) postacquisition delays. Significantly different from SHAM: *p < 0.05. Tendency to differ from SHAM: ⁽*⁾p = 0.062. Significantly different from ILN/LT: ¤p < 0.05. C, Representative swim paths in each thalamic group during the 5 d (recent memory, upper part) and 25 d (remote memory, lower part) probe trials. The black square indicates the starting point. The position of the platform during acquisition is marked in the lower left quadrant. At both delays, SHAM rats remembered the spatial position of the platform and concentrated their searches in the target quadrant where the platform was located. In contrast, ATN lesions affected spatial exploration at both delays while ILN/LT rats were impaired only during the remote probe trial.