The effect of EMDR has even been proven in experiments on mice
The mechanism of action of the therapy form EMDR (Eye Movement Desensitization and Reprocessing) was demonstrated within a mouse model of fear conditioning. The aim is to treat post-traumatic stress reaction (PTSD) by unlearning fear using alternating bilateral stimulation, i.e. alternating and bilateral stimulation.
This form of therapy works with so-called extinction learning (“extinction”). Here, a new (anxiety-)inhibiting reaction is learned, through which the learned fear reaction is supposed to be suppressed. Based on the assumptions of EMDR that alternating stimulation of different stimuli (moving the eyes back and forth, alternating touches, lights or even sounds) is helpful in processing traumatic experiences, this was examined in an experiment with mice. This is preceded by Ivan Pavlov's well-known animal model of classical conditioning. South Korean neuroscientists constructed a special cage in which mice were first given a painful, electrical stimulus (unconditioned stimulus) via the floor of the cage. At the same time, an acoustic stimulus (conditioned stimulus) sounded over a loudspeaker, so that the mice associated the two stimuli with each other. After successful conditioning, the acoustic stimulus alone led to the same reaction in the mice as the painful electrical stimuli - namely, a state of shock. The researchers now asked themselves whether a moving light leads to better unlearning of the fear reaction when the acoustic stimulus sounds or whether it leads to learning the new reaction not to be afraid.
To use EMDR on mice, the animal sits in a cylindrical cage surrounded by LEDs. When the acoustic stimulus is presented again, the back and forth movement of the light also directs the animal's attention back and forth, which is intended to reduce the fear reaction. In fact, the fear response in the mice decreases more quickly and reaches a lower level under the extinction combined with EMDR condition than under extinction alone. To check whether there is a connection between the moving stimulation and the simultaneity of the stimulation with the sound, three control conditions (LEDs light continuously, LEDs flash or LEDs move back and forth) were used. It was shown that the moving LEDs with simultaneous presentation of the sound produce the effect of a reduced fear reaction. EMDR can also be carried out on mice and has a much stronger effect than the use of extinction alone. This means that “EMDR” helps mice to unlearn fear significantly better than behavioral therapy interventions alone.
But what anatomical mechanisms underlie the effectiveness of EMDR? Since the 1970s, the superior colliculus, one of the most studied structures of the midbrain, has been associated with eye movements and focusing on an object. The mechanisms located in the deeper layers of the superior colliculus were examined, which lead to an accelerated reduction of the fear reaction through EMDR. Studies in another mouse experiment, again with the stimuli used - sound and light, were able to determine that the back and forth movement of the visual stimulus activated most of the neurons and thus reduced the fear reaction more quickly. In the extinction plus EMDR condition, 63.3% of neurons were activated, compared to only 33.7% in the extinction condition. The researchers derived the effect of EMDR through increased activation of the superior colliculus.
Here is the link to the original article: Spitzer M. Neurology 2019; 38: 231–239