EN 
NL 
D Eye Movement Desensitisation and Reprocessing (EMDR) therapy has evolved significantly with technological advancements, including Virtual Reality (VR) applications. A key component of this therapy is the movement of visual stimuli, such as a sphere, across the user's field of vision (Figure 1). Additionally, auditory clicks and various tasks (like a go/no-go task or mathematical equations) can be added to tax the working memory while reprocessing traumatic memories.
It is expected that the speed and trajectory of the moving sphere can impact the therapy's effectiveness in reducing Subjective Units of Distress (SUD; a scale ranging from 0 to 10 measuring the subjective intensity of distress that is currently experienced by the client). This blog post presents an analysis of a subset of Psylaris’ internal database (5732 individual sessions) in order to see how settings like the sphere’s speed and trajectory may influence SUD reduction. Subjective Units of Distress (SUD; a scale ranging from 0 to 10 measuring the subjective intensity of distress that is currently experienced by the client). This blog post presents an analysis of a subset of Psylaris’ internal database (5732 individual sessions) in order to see how settings like the sphere’s speed and trajectory may influence SUD reduction.
Understanding the sphere’s speed and its impact on SUD-decrease
The "speed of the sphere" in EMDR refers to how quickly the visual stimulus travels across the user's field of vision. With Psylaris’ EMDR-VR, where the headset can be used autonomously, the sphere's speed has to be set before handing over the headset to the client that will take it home. With EMDR-Plus, where the headset will be used together with a therapist in the treatment room, the settings can be altered even during the session. For the current analysis, only EMDR-VR sessions are included to ensure that the sphere’s speed and trajectory were consistent during the entire session.
Research (Van Veen et al., 2015) suggests that the speed of the sphere affects SUD reduction. They state that for optimal engagement, the speed must be fast enough to engage the brain's information processing mechanisms without overwhelming the user. If it is too slow, the session may not be engaging enough and leave too many resources accessible for vivid memory recall and its associated emotions; if it is too fast, it will prevent the memory from being recalled or even increase anxiety or discomfort. However, different users have varying abilities to track moving objects and respond differently to the therapy. Factors such as individual distress levels and cognitive processing speeds influence the ideal sphere’s speed for each user.
With Psylaris’ modules for EMDR, a default speed of "1" corresponds to a movement cycle of 1.5 seconds (for a linear path, this means left-to-right-to-left). Each increment of 0.25 increases the speed by an additional 25% relative to the default speed of 1. For example, a speed of 1.25 is 25% faster than 1 and a speed of 1.5 is 50% faster than 1. Similarly, a speed of 0.75 is 25% slower than 1.
A violin boxplot (Figure 2) is a chart that shows both the distribution and spread of data. The central line represents the median of the data, the box shows the spread of the middle 50% of the data and the whiskers (lines outside the box) show the range of the data. The width of the "violin" behind the box indicates the density of the data. The wider the section, the more data points are in that range.
Our findings indicate that a sphere’s speed of "1" results in the most significant decrease in distress levels compared to speeds of 1.25 and 1.5. The effects of speeds 1.25 and 1.5 are very similar, both showing a slight reduction in effectiveness compared with the default of 1, while a lower speed of 0.75 shows a lower SUD-decrease between the start and end of the session compared to the higher speeds. However, the number of sessions using speeds lower than 1 is limited, making further research necessary to strengthen these findings.
One potential confounding variable is that different speeds are typically paired with specific trajectories. For example, "linear" trajectories are often set at a speed of 1, while "bouncing" trajectories default to 1.25. This suggests that trajectory type might also play a role in SUD reduction, which will be explored in the following section.
The role of the sphere’s trajectory in SUD-decrease
When using VR for EMDR therapy, the sphere can follow different movement paths, including:
- Linear trajectory (side-to-side movement)
- Bouncing trajectory (up and down motion)
- Elliptical trajectory (circular or oval movement pattern)
Our findings (see Table 1) suggest that the elliptical trajectory may lead to a steeper reduction in SUD scores compared to the linear or bouncing trajectories for EMDR-VR (SUD-decrease of 5.38 compared to 4.55 and 4.06 respectively). However, due to the limited number of sessions using this “ellipse” setting, more data is needed to confirm its effectiveness statistically.
Key takeaways and future directions
- Sphere’s speed: The most effective speed for SUD reduction appears to be the default of "1", though some users may require adjustments based on their individual responses.
- Sphere’s trajectoryThe elliptical trajectory shows promise but requires further study.
- Personalisation is essentialUsers respond differently to therapy settings, highlighting the need for flexible adjustments. With Psylaris’ EMDR-Plus, it is possible to modify sphere settings and introduce additional distractors to maximize working memory load during the session.
To enhance the effectiveness of EMDR therapy with VR, future research should aim for a balanced distribution of session settings across speeds and trajectories. This will help pinpoint the optimal parameters for reducing distress levels effectively. In the meantime, therapists should consider individual user needs when selecting the sphere’s speed and trajectory settings to maximise therapy benefits.
What has been your experience with adjusting the sphere’s speed and trajectory in EMDR-VR and/or EMDR-Plus sessions? Have you found certain settings to be more effective for specific types of clients?
References
- Van Veen, S. C., van Schie, K., Wijngaards-de Meij, L. D., Littel, M., Engelhard, I. M., & van den Hout, M. A. (2015). Speed matters: Relationship between speed of eye movements and modification of aversive autobiographical memories. Frontiers in Psychiatry, 6, 45.
