## 1 Introduction  
In our daily life, we often have to learn new locations and destinations. This involves a gradual learning process, in which typically the number of errors declines with each new route reproduction attempt. In the initial stages of learning a new route--the first one or two times you try to make a new route trip--you depend on a more or less fragile spatial episodic memory. Episodic memory allows coding of personal events, which contain complex clusters of information also informing the original context of learning [1]. Initially, route events have to be memorized on the basis of a single experience (e.g., the first route trip). Encoded memory has a conscious format: For example, you realize you have to turn right at the newspaper shop. It is also fragile: It can be incomplete, open to confusion (streets and buildings look similar), and prone to being forgotten the longer the time between the first and the second trip. Episodic memory typically stores unique events [1]. The combination of what happened within a spatiotemporal context makes a onetime experience. However, in the case of traveling the same new route multiple times, the spatial context can be repeated with only very limited variation. This could afford cumulative strengthening of the route memory trace, turning it into a more semantic memory format or even a semi-procedural memory. The latter can provide a more automatic, partly unconscious memory routine (you turn right at the newspaper store without making a deliberate decision). [PERSON] et al. [2] emphasize the difference between so called wayfinding (finding novel paths between locations) and processing well-established trajectories from one location to the other. They report distinct neural circuitries to be associated with these two types of navigation: Wayfinding recruits the hippocampus whereas the latter depends on the caudate nucleus (see, however, [PERSON] et al. [3]). In the neuropsychological literature, wayfinding--the initial learning of new destinations--has often been investigated. That is, performance is tested after a single or only a few exposures to the target routes [4; 5; 6]. In other studies, however, multiple learning and test occasions have been included. [PERSON] et al. [7] trained older participants on a route learning test in which routes of different lengths had to be reconstructed within a \(5\times 5\) array marked on the floor in an indoor environment. Practice clearly helped the older people. [PERSON] et al. [8] tested younger and older participants on VR routes that were trained on across 6 sessions. Both groups improved with training, but the older people had more difficulty in retracing the routes (going from end to start). The authors suggested that retracing might depend on a more allocentric hippocampal-dependent strategy that is similar to the wayfinding described above. Older people might suffer hippocampal decline. [PERSON] et al. [9] specifically trained stroke patients to apply novel navigation strategies, focusing not on learning a specific route but more on acquiring a richer generic navigational ability. [PERSON] and colleagues reported a highly interesting case report on a stroke patient who suffered a really severe topographical disorientation disorder [10]. The patient was followed for years and was observed to be able to learn routes after extensive dedicated interventions. A requirement was that the routes were highly familiar (traveled frequently). The authors suggest that this might involve a form of implicit route learning. Assessing the remaining route learning potential in neuropsychological patient groups is very valuable. It gives more insight in how to enhance mobility and autonomy in otherwise restricted individuals. [PERSON] et al. [10] noted for their topographical disorder patient that their rehabilitation intervention increased quality of life and independence. [PERSON] et al. [9] pointed out that their patients regarded the navigation strategy training as valuable.