Figure 6.

The relative change in hippocampal gamma power during the RFTs (A) and non-RFTs (B) of the retention test for the simple discrimination task (Simple), the early learning stage (Early stage), and the late learning stage (Late stage) of the FN task. The 0-ms period indicates the onset of stimulus presentation. The period was divided into 45 sub-periods of 100 ms each. The mean hippocampal gamma power (30–100 Hz) from 500 to 400 ms before the stimulus onset was counted as the −400-ms period (no stimuli were present and no rats pressed the lever during this period), and the relative gamma power calculated for each period was normalized to that of the −400-ms period (relative gamma power of each period = gamma power of each period/gamma power at the −400-ms period). The “LS” indicates a significant difference between the late learning stage of the FN task and the retention test for the simple discrimination task (LS: p < 0.05). Error bars indicate s.e.m.