Technical approaches used in the laboratory include 1) functional epifluorescence imaging of transmembrane voltage changes in populations of neurons; 2) multiphoton and confocal imaging of intracellular calcium dynamics both in individual neurons and large populations of neurons; 3) multielectrode array recording of neuronal activation within hippocampal microcircuits; 4) transgenic labeling and gene targeting in specified subpopulations of neurons; 5) optogenetic activation and silencing of specified populations of neurons; and 6) patch clamp and extracellular recording techniques.