Neuronal Ensemble Entropy Coding in the Anterior Cingulate Cortex of Rats under Fear Conditioning

The aim of this study is to investigate neuronal ensemble coding mechanism via entropy under fear conditioning. Entropy is a measurement of uncertainty and the amount of information in a sequence, which can quantify information as well as describe the ensemble coding characteristic. The original data we rerecorded at anterior cingulate cortex (ACC) of rats by implicated 16 channels array under two conditions:pre-training and testing. Then through a high-pass filtering (300 Hz-7.5 KHz) and spike detection, spike trains were obtained via spike sorting. The entropy values were performed in a selected window (500 ms)with a moving step (size of 1/4 window). The results showed that the entropy values were lower in pretraining with no ensemble activity; in testing condition,the entropy values were higher, where presented obvious ensemble activity. Conclusion: in pre-training,no ensemble activity was presented, which indicated that memory was not formed; in testing condition,obvious ensemble activity was manifested, which showed that the fear memory has been built up. The effect on coding firing information of neuronal ensemble by dynamic entropy coding was proved.