Losing one's way in a digital world: VR studies on navigation

Transcription

1 Losing one's way in a digital world: VR studies on navigation Albert Postma, Jessie Bullens and Ineke J. M. van der Ham Experimental Psychology, Helmholtz Institute, Utrecht University, the Netherlands

2 Introduction Spatial navigation is an essential part of our lives: we have to find our way in familiar environments, such as when making the usual trip to work; engage in serious spatial planning such as taking a detour when the usual road is blocked ; and learn a new route, for example when going to a job interview in an unfamiliar town. Importantly, we engage in navigation activities several times a day. Furthermore, the social consequences of getting lost are considerable. In other words, the ecological validity of spatial navigation is high. How does our brain manage to guide us through a complex spatial world? Multiple sources of information can be used evoking a variety of mental processes. A major distinction is that between allocentric (world-centered) and egocentric (body-centered) representations (Arleo & Rondi-Reig, 2007; Burgess, 2006). The former is based on processing relations between places and multiple distal landmarks; the latter fixates on the to be traversed direction with respect to the own body (e.g go straight ahead or turn left ). In rats allocentric (or place-learning) navigation has been observed to depend in particular on the hippocampus, whereas simple egocentric (stimulus-response like) navigation involves the dorsal striatum (+parietal areas) (Morris et al., 1982; O Keefe & Nadel, 1978; Packard & Knowlton, 2002; White & McDonald, 2002). Recently, Rondi-Reig and colleagues (2006) showed that an additional sequential egocentric representation also loads on the rodent hippocampus. A sequential egocentric strategy essentially refers to a memory for the temporal order of body turns associated with spatially distinct choice points. In humans the neurocognition of spatial navigation is less easy to examine. Typically, the environment is larger and more complex. Van Asselen et al. (2006a, 2006b) and van der Ham et al. (in press) identified landmark recognition, landmark order, route continuation, map drawing, and global orientation as the basic components in a complex route memory test. Map drawing and global orientation sense can be seen as more allocentric. Temporal order memory is linked to an egocentric updating strategy. Route continuation may be solved either in a more egocentric way or by an allocentric computation. Van Asselen et al. (2006b) observed an extended right hemispheric circuitry

3 for these various route components in a lesions overlap study in stroke patients. Their participants had to learn a route in an indoor, unfamiliar university building complex. One can question to what extent the latter type of environment and test situation applies to spatial navigation in the real world. The spatial range is limited, and the landmarks can be regarded as more local rather than really distal (e.g. in the direction of the coffee machine ). Furthermore, it can be difficult to strictly control prior knowledge of the participants with the testing environment (e.g. testing patients navigation abilities in a hospital setting). Most importantly, the experimenter does not have any direct control over distracters (i.e. people moving in the same space) or explicit spatial cues (i.e. direction signs). In light of these limitations, Virtual reality technology can form a powerful research tool which avoids these problems. In collaboration with the UMPC and the Collège de France in Paris (Rondi-Reig; Berthoz) we recently used a VR maze learning test in children 5, 7 and 10 years of age (Bullens et al., in press). Interestingly, this test was inspired by the real mazes employed to study memory in rats (Rondi-Reig et al., 2006). Children could move themselves through the virtual maze ( StarMaze ) by means of a joystick. They were trained on a fixed route but after some time unbeknownst to the participants the starting point changed. Since both a sequential egocentric strategy as well as an allocentric strategy were rewarded it could be examined to what extent children used either strategy spontaneously while learning the fixed route. All children were found to have a higher amount of sequential egocentric strategy usage, however only older children (>7 yrs) also showed allocentric strategy usage. However, in a different version of the task, in which participants were only rewarded when they used an allocentric strategy, it was shown that 5-year-olds were able to employ this strategy. These findings indicated that already from a young age children can use different navigation strategies, but that the preference for either of these strategies changes with age.

4 Figure 1. Example from the Star Maze task (Igloi et al., 2009) Towards a more ecological VR environment While the foregoing StarMaze test can elegantly separate sequential egocentric from allocentric navigation, one could argue that it still far removed from how we humans navigate in the real world. Fortunately there is a recent trend to adopt real life VR environments for navigations studies (Péruch & Wilson, 2004; Schmelter et al., 2009). One particularly strong example is the VR model of the German town Tübingen, created by the MPI. In collaboration with the MPI we adapted this test to study navigation in brain damaged patients. Spatial memory and navigation is typically affected by damage to the right hemisphere. Two cases of right hemisphere lesioned patients were brought to our attention because of their self reported spatial navigation problems, including extreme difficulties in coping with new environments and high levels of spatial anxiety. We showed them a route through Virtual Tübingen and afterwards tested them on their ability to recognize scenes from the city, indicate the correct turns to be taken at certain points in the route, and temporally order scenes from the route.

5 Interestingly one patient was specifically impaired in the temporal domain; ordering the places you have encountered in time, whereas the other patient performed poorly in a more strictly spatial way; choosing where to go next from a given scene. Both tests refer to essential processing components of spatial navigation. This is one the first studies that showed these navigation components can be dissociated in a neurocognitive sense. Further VR studies are needed to pinpoint the precise brain areas which underlie them. Figure 2. Scene from Virtual Tubingen Recommendations Virtual Reality environments can be exciting tools to study spatial navigation. They can accurately mimic real life environments and situations, such as the authors of this paper encountered on their first trip to real Tübingen. We can control for various unforeseen distracters and interfering conditions: road blocks, unwanted traffic, fellow travellers asking the road or pointing towards the destination. VR tools might form ideal training tools for neurological patients, sensory impaired persons and the elderly. Anxiety might drop after exposure to the virtual worlds which in turn could

6 assist the participant in finding their way in a new, real world. Ultimately they can offer invaluable assistance to city planners and geographical scientists when they make plans for new roads, parks and buildings. References Arleo, A., and Rondi-Reig, L. (2007). Multimodal sensory integration and concurrent navigation strategies for spatial cognition in real and artificial organisms. J Integr Neurosci 6, Burgess, N. (2006). Spatial memory: how egocentric and allocentric combine. Trends in Cognitive Sciences 10, Igloi, K., Zaoui, M., Berthoz, A., and Rondi-Reig, L. (2009). Sequential egocentric strategy is acquired as early as allocentric strategy: Parallel acquisition of these two navigation strategies. Hippocampus. Available at: tation&list_uids= Morris, R. G. (2001). Episodic-like memory in animals: psychological criteria, neural mechanisms and the value of episodic-like tasks to investigate animal models of neurodegenerative disease. Philos Trans R Soc Lond B Biol Sci 356, O'Keefe, J., and Nadel, L. (1978). The Hippocampus as a Cognitive map (Oxford University Press). Overman, W., Pate, B., Moore, K., and Peuster, A. (1996). Ontogeny of place learning in children as measured in the radial arm maze, Morris search task, and open field task. Behavioral Neuroscience 110, Packard, M., and McGaugh, J. (1996). Inactivation of hippocampus or caudate nucleus with lidocaine differentially affects expression of place and response learning. Neurobiol.Learn.Mem. 65, Rondi-Reig, L., Libbey, M., Eichenbaum, H., and Tonegawa, S. (2001). CA1-specific N- methyl-d-aspartate receptor knockout mice are deficient in solving a nonspatial transverse patterning task. Proc Natl Acad Sci U S A 98, Rondi-Reig, L., Petit, G., Tobin, C., Tonegawa, S., Mariani, J., and Berthoz, A. (2006). Impaired sequential egocentric and allocentric memories in forebrain-specific-nmda receptor knock-out mice during a new task dissociating strategies of navigation. J.Neurosci. 26,

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