Background
Eye Movement Desensitization and Reprocessing (EMDR) is a psychotherapy for Post-Traumatic Stress Disorder (PTSD), which has the particularity of using alternating stimulation on both sides of the patient, such as eye movements, tones or taps. EMDR has been proven to be one of the most effective treatments for PTSD and can show signs of improvement in fewer hours of therapy than other therapies. While EMDR has been investigated through physiological and imaging studies on humans, its method of action and the neural pathways it employs remain unknown. In this context, the elaboration of an animal model of EMDR would permit the use of more invasive methods of investigation which could provide new and more precise data on the subject.
Aims:
The aim of the thesis was to develop an animal model of EMDR, which was carried out in two parts. The aim of part A was to develop and validate a device for rats capable of alternatingly stimulating the rat bilaterally. The aim of part B was to study the difference of fear extinction in fear conditioning experiments between rats receiving EMDR-like stimulations during testing versus those with no stimulation of such.
Method:
Part A: A chronic implant with detachable earphones, inspired by a device developed by Nodal et al. in ferrets, was adapted to rats to produce the alternating stimulation. To prove that the rodent could hear tones coming from the device and could distinguish tones coming from one side or the other, we used a fear conditioning experiment (n=3) in which tones coming from one side of the earphone device were paired with a shock, while tones coming from the other side of the device were not.
Part B: To study the effect of alternating stimulation on fear extinction, we used a fear conditioning experiment in which light was used as a CS and alternating stimulation was delivered to the rat through the earphone device during CS presentation in the testing phase.
Results:
Part A: Maximal levels of freezing to tones coming from the earphones were measured in the testing phases of the experiment, however no discrimination of the origin of the tones was observed as maximal levels of freezing were seen in reaction to tones originating from both earphones.
Part B: While an appropriate protocol was designed and tested, technical difficulties which occurred during the experiment prevented the production of analyzable results. Nevertheless measures to avoid such technical difficulties were successfully implemented and only limited time prevented production of further results.
Conclusion
The development of a device to deliver audio EMDR-like stimulation was successful as rats were able to hear the tones given through both earphones. However, I was unable to prove that the rats were able to distinguish the origin of the tone. While technical difficulties and time limitation prevented the acquirement of results in the study of the effect of EMDR-like stimulation on fear extinction, measures to avoid the technical problems were successfully implemented.