Figure 2.

Acquisition of conditional fear. All rats acquired conditional freezing during training. Graphs show the mean percent time each group spent freezing during the training session for trace conditioning (A) or delay conditioning (B). After the 6-min baseline period, each point represents 90 sec starting at CS onset of each trial. Although rats injected with the NR2A antagonist NVP prior to training tended to freeze less in general compared with control rats, this did not represent a significant reduction in freezing (P > 0.10 for both trace and delay groups).