Deep brain stimulation (DBS) has become an important method for directly modulating neuronal activities through electric currents. Compared with drugs, DBS is much less likely to cause brain-wide or systemic side effects. Although the use of DBS to treat several motor symptoms has been approved by FDA, using DBS for memory and cognitive disorders are still experimental. My project aims to use deep brain microstimulation (DBMS), which causes even less brain damage and has higher spatial resolution than DBS, for memory recovery. I will first explore the mechanisms of extracellular electrical stimulation and design novel waveforms to efficiently and effectively stimulation the neurons. Then I will use microelectrodes arrays to selectively stimulate neuron ensembles in the mouse hippocampus with carefully-designed current waveforms and conduct behavior experiments to recall fear memories. This would pave the way for the treatment of memory loss with DBMS in clinical trials.