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All behavioral tests were conducted during the light cycle. Before each test, the miniature microscope was attached to the baseplate of a mouse under isoflurane anesthetization (1–2% in O₂) and the focus ring was adjusted until the fluorescence from the GCaPM6f was clearly observed. We secured the microscope on to the baseplate with a screw and Kwik-cast silicone sealant (World Precision Instruments). The focus was maintained at the same position across the fear conditioning and memory recall tests. Each mouse was habituated in the testing room for at least 1 hr before any behavioral tests were performed. The environment for habituation and testing included white noise at 60 dB and the light intensity at 100 lx. Animal behaviors and calcium imaging movies were recorded simultaneously with the TTL-trigger interface. Calcium signals were acquired at 20 Hz using the nVista software (Inscopix Inc.) with the LED power 60–150 uW. Mice were excluded if acquired data sets were incomplete or AAV injection was not successfully targeted to CA1.