Mobilum-a new mobile app to engage visuospatial processing for the reduction of intrusive visual memories.

Intrusive memories are a key symptom of posttraumatic stress disorder (PTSD), a prevalent condition causing considerable personal suffering, and entailing large direct and indirect societal costs. While effective treatment options for PTSD exist, on a global scale they are not readily available to many patients in need. In the last years, several studies have shown that the computer game Tetris can reduce the frequency of intrusive memories in healthy subjects (after a trauma analogue), in populations at high risk of developing PTSD, as well as in patients already suffering from PTSD. The presumed mechanism behind this effect is that both Tetris and intrusions require-and therefore compete for-limited visuospatial working memory resources. In search for a new alternative tool that can engage visuospatial processing as effectively as Tetris, we developed a game named Mobilum. This is an app for Android devices, in which users have to rotate in an imaginative way around a translucent virtual cube in order to decide from which perspective a complex three-dimensional figure inside the cube is seen. Mobilum was developed to investigate whether the intrusion-reducing effect is exclusively inherent to Tetris, or if it can be achieved with another task engaging users in visuospatial processing. Also, unlike available versions of Tetris, Mobilum offers full control over key game parameters (e.g., difficulty, game duration), and is free of copyright and commercial issues. In this method paper, we describe the new Mobilum app, its theoretical background and development. Additionally, the first data on usability and feasibility are reported, as rated by N=16 inpatients. Finally, we will provide an outlook on the next steps necessary to investigate Mobilum's potential as a therapeutic tool.