Freely moving animals may turn through several revolutions in one direction. While recording from freely moving animals, therefore, an electrical commutator is needed to prevent twisting of the wires that go from the electrode (moving and rotating with the head) to the amplifier/recorder (fixed to the ground).
To capture the complex movements of freely moving animals, it's necessary to use an electrical commutator. This ensures that wires from the rotating electrodes (attached to the animal) do not become tangled with the fixed amplifiers/recorders (located on the ground).