Tone Responses Latency of Plasticity Cross-Correlations Pre Pre Post 6a。 10-15 Post 上hh士 ,16 Post-Extinction Post-Extinction ■ 6 ms eral amygd LA onditioning,esepcial cy respons (10-15 away atter tcorclato before con right pe the ony rem Based on Quirk et a().0 2 4 6 8 0 10 20 30 40 50 60 70 10 20 15 2 6 4 10-15 ms 0 50 100 150 ms Conditioning Extinction 1 2 3 4 5 6 100 200 300 400 500 600 700 0 2 4 6 -16 -8 0 8 16 0 2 4 6 -16 -8 0 8 16 0 2 4 6 -16 -8 0 8 16 Pre Post Post-Extinction Pre Post Post-Extinction Tone Responses Cross-Correlations Latency of Plasticity ms Latency (ms) Blocks of 10 Trials -80 Figure 5 During fear conditioning, cells in the lateral amygdala (LA) of rats show plasticity (increased firing rates) during exposure to a conditioned stimulus tone. (Left) Some cells are responsive to tones prior to conditioning (Pre), but their rate of firing increases after conditioning, esepcially the earliest latency response (10–15 ms after tone onset). This early plasticity goes away after extinction. From simultaneously recorded cells, it can be seen that conditioning also leads to an increase in the synchrony of firing, such that cells that were not correlated before conditioning become so afterward (right panel). In some cases (not shown), the synchrony remained even after extinction, which suggests that long-term memory may be in part encoded by connections between cells rather than just in the rate of firing. Based on Quirk et al (1995). 168