Behavioral Neurosciences Institute (INeC) 1 article published in JoVE Behavior A Wireless, Bidirectional Interface for In Vivo Recording and Stimulation of Neural Activity in Freely Behaving Rats Liana Melo-Thomas1,2, K.-Alexander Engelhardt1, Uwe Thomas3, Dirk Hoehl3, Sascha Thomas3, Markus Wöhr1, Bjoern Werner4, Frank Bremmer4, Rainer K.W. Schwarting1 1Behavioral Neuroscience, Experimental and Biological Psychology, Philipps-Universität Marburg, 2Behavioral Neurosciences Institute (INeC), 3Thomas RECORDING GmbH, 4Department of Neurophysics, Philipps-Universität Marburg A wireless, bidirectional system for multi-channel neural recordings and stimulation in freely behaving rats is introduced. The system is light and compact, thus having minimal impact on the animal´s behavioral repertoire. Moreover, this bidirectional system provides a sophisticated tool to assess causal relationships between brain activation patterns and behavior.