A new electrode configuration for recording electromyographic activity in behaving mice

With the increasing use of normal and genetically modified mice in the field of motor physiology, there is a need for a simple and reliable technique for recording electromyographic (EMG) activity in behaving mice. Here, we describe a new method for the fabrication and implantation of fine EMG recording electrodes into multiple muscles of adult mice. This method minimizes surgical damage to the muscles and the connecting leads have only a modest influence on leg movements when electrodes are implanted into distal muscles. We demonstrate that excellent EMG recordings can be obtained during walking, swimming and scratching for the vastus lateralis, tibialis anterior and gastrocnemius muscles in normal adult mice. EMG recordings were also made in a mutant EphA4 mouse to demonstrate the utility of the method for examining motor patterns in genetically modified animals. We also developed a method for constructing highly reflective markers that could be viewed over a range of orientations to measure the kinematics of legs movements during stepping. A commercial motion analysis system was used to track six markers during walking and to synchronize video and EMG data during walking sequences.