How do neural circuits give rise to human memory? To answer this question, we combine optogenetics, pharmacology and behavioral manipulations with high-density tetrode and depth-probe recordings of neural activity in awake behaving rats. We are most interested in areas known as the hippocampus, medial septum, and entorhinal cortex which have all been shown to have important roles in memory in humans and animals. We use computational modeling to bridge this experimental work and human memory processing. This work suggests that neural rhythms allow the brain to code, manipulate and store information and that these dynamics are regulated by acetylcholine.