Phase-dependent synaptic changes in the hippocampal CA1 field underlying extinction processes in freely moving rats

► Synaptic efficacy in the CA1 field was enhanced by repeated extinction trials. ► Synaptic potentiation did not occur during retrieval phase after extinction training. ► Synaptic changes during extinction training were mimicked by those induced by LFS. ► Freezing was reduced by repeated delivery of LFS, as well as extinction training. ► LFS-induced synaptic plasticity appears to be associated with extinction learning.