A Novel Virtual Reality-Based Training Protocol for the Enhancement of the "Mental Frame Syncing" in Individuals with Alzheimer's Disease: A Development-of-Concept Trial

Abstract

A growing body of evidence suggests that people with Alzheimer's Disease (AD) show compromised spatial abilities. In addition, there exists from the earliest stages of AD a specific impairment in "mental frame syncing," which is the ability to synchronize an allocentric viewpoint-independent representation (including object-to-object information) with an egocentric one by computing the bearing of each relevant "object" in the environment in relation to the stored heading in space (i.e., information about our viewpoint contained in the allocentric viewpoint-dependent representation). The main objective of this development-of-concept trial was to evaluate the efficacy of a novel VR-based training protocol focused on the enhancement of the "mental frame syncing" of the different spatial representations in subjects with AD. We recruited 20 individuals with AD who were randomly assigned to either "VR-based training" or "Control Group." Moreover, eight cognitively healthy elderly individuals were recruited to participate in the VR-based training in order to have a different comparison group. Based on a neuropsychological assessment, our results indicated a significant improvement in long-term spatial memory after the VR-based training for patients with AD; this means that transference of improvements from the VR-based training to more general aspects of spatial cognition was observed. Interestingly, there was also a significant effect of VR-based training on executive functioning for cognitively healthy elderly individuals. In sum, VR could be considered as an advanced embodied tool suitable for treating spatial recall impairments.

Keywords: Alzheimer's Disease; allocentric; egocentric; spatial memory; virtual reality.

Figure 1

Timeline of the VR-based training program. The training consisted of 10 sessions for 3–4 consecutive weeks, with approximately three sessions a week. After brief training in VR technology (about 2 min), each session comprised two parts: an “encoding” and a “retrieval phase.” Participants were assessed with a comprehensive neuropsychological assessment before and after participation in the training.

Figure 2

The map of the virtual city. The city was built around a central square with a fountain and a bar with some tables, which represents the starting point of the navigation. There were buildings and shops spread out in the city. In the northern part of the city, there was a large street surrounded by trees with some cars, whereas the southern part was more residential.

Figure 3

One of the objects to be found during the VR-based training program. During the encoding phase, participants were asked to locate one, two or three hidden objects (i.e., a bottle of milk, a plant in a vase and a trunk). They received the specific instruction of memorizing the position of these objects, which were positioned at different parts of the city since in the retrieval phase they were asked to retrieve their spatial positions. The training was personalized according to the level reached by each participant, so that if a patient was not able to locate the first object, the other objects were not presented.

Figure 4

During the retrieval phase, to facilitate the retrieval of spatial information, an interactive aerial view of the virtual city was presented during the navigation and the display was oriented depending on the participant's movement in the virtual world.