Investigation of CA1 Neuronal Activity During Context fear Conditioning with Miniature Fluorescence Microscopes

Plastic changes in the neurons of the amygdala during learning in fear conditioning and their contribution to the modifications of behavior are well known, but the impact of hippocampal neurons in this behavioral task is not well studied to date. Recently a novel technique for simultaneous recording of calcium signal in multiple neurons in the brain of awake freely moving animals by miniature fluorescent microscope (miniscope) was developed. With the use of the miniscope, we have investigated neuronal activity in the CA1 area of hippocampus during memory formation and a recall in the task of contextual fear conditioning and correlated it with recorded mice behavior. Three epochs during learning were analyzed in mice behavior and brain activity: 120 s before, 2 s during, and 30 s after the electric shock. Memory retrieval was induced by placement of the animals for 180 s in the same context 24 h and 48 h after learning. The total amount of the neurons recorded in three mice was 507 during learning and 401 during memory retrieval. The patterns of neuronal activity were analyzed and discussed.