Progression of activity and structural changes in the anterior cingulate cortex during remote memory formation

•Conditioned mice show strong freezing on post-training days 1, 5, 7, 14, 21 and 36.•C-fos activation in anterior cingulate cortex augments regularly from day 5 to day 21.•Spine density on neurons in the same region augments at day 7 and then remains stable.•Single neuron spine density scores become more homogeneous as memory matures over time.