Max Planck Institute for Metabolism Research 1 article published in JoVE Neuroscience Optogenetic Entrainment of Hippocampal Theta Oscillations in Behaving Mice Franziska Bender1,2, Tatiana Korotkova2,3, Alexey Ponomarenko1,2 1Systems Neurophysiology Research Group, Institute of Clinical Neuroscience and Medical Psychology, Medical Faculty, Heinrich Heine University Düsseldorf, 2Behavioural Neurodynamics Group, Leibniz Institute for Molecular Pharmacology (FMP)/ NeuroCure Cluster of Excellence, 3Neuronal Circuits and Behavior Research Group, Max Planck Institute for Metabolism Research We describe the use of optogenetics and electrophysiological recordings for selective manipulations of hippocampal theta oscillations (5-10 Hz) in behaving mice. The efficacy of the rhythm entrainment is monitored using local field potential. A combination of opto- and pharmacogenetic inhibition addresses the efferent readout of hippocampal synchronization.