Direct navigation

Abstract: The present study investigated the effect of aging on direct navigation measures and self-reported ones according to the real-virtual test manipulation. Navigation (wayfinding tasks) and spatial memory (paper-pencil tasks) performances, obtained either in real-world or in virtual-laboratory test conditions, were compared between young (n = 32) and older (n = 32) adults who had self-rated their everyday navigation behavior (SBSOD scale). Real age-related differences were observed in navigation tasks as well as in paper-pencil tasks, which investigated spatial learning relative to the distinction between survey-route knowledge. The manipulation of test conditions (real vs. virtual) did not change these age-related differences, which are mostly explained by age-related decline in both spatial abilities and executive functioning (measured with neuropsychological tests). In contrast, elderly adults did not differ from young adults in their self-reporting relative to everyday navigation, suggesting some underestimation of navigation difficulties by elderly adults. Also, spatial abilities in young participants had a mediating effect on the relations between actual and self-reported navigation performance, but not for older participants. So, it is assumed that the older adults carried out the navigation task with fewer available spatial abilities compared to young adults, resulting in inaccurate self-estimates.

Abstract: Background: Intraoperative navigation is a rapidly emerging procedure in orthopaedic surgery and neurosurgery. For abdominal tumors (e.g. liver metastasis) and soft tissue tumors there is only limited experience with navigation techniques due to problems of organ shift and tissue deformation. We have developed a navigation system for tumor resection in soft tissue based on 3D ultrasound imaging and optical tracking. Methods: Two different modes of navigation were evaluated and compared with conventional surgery in an experimental soft tissue model. Both techniques were based on 3D ultrasound and an optical tracking system for intraoperative real time registration of surgical instruments. These two techniques were used: a) Indirect navigation with ultrasound guided insertion of a tracked hook needle into the tumor; and b) Direct navigation using a 3D image which was obtained with an optically tracked 3D ultrasound probe. It was the aim of both techniques to achieve a circumferential resection margin of 2 cm around the tumor. Results: A total of 23 resections were performed consisting of indirect (n = 7) and direct (n = 10) navigation and conventional surgery (n = 6) as gold standard. For indirect navigation a median deviation from the ideal resection margin (accuracy) of 0.32 cm was measured. Direct navigation showed an accuracy of 0.16 cm compared to 0.42 cm with conventional surgery. Navigated surgery showed for both techniques a significant increase of resection accuracy compared to conventional resection (p < 0.05). Conclusion: 3D ultrasound based indirect and direct optoelectronic navigation for resection of soft tissue tumors is feasible and may improve intraoperative orientation with increased surgical precision.

Abstract: In everyday life, navigators often consult a map before they navigate to a destination (e.g., a hotel, a room, etc.). However, not much is known about how humans gain spatial knowledge from seeing a map and direct navigation together. In the present experiments, participants learned a simple multiple corridor space either from a map only, only from walking through the virtual environment, first from the map and then from navigation, or first from navigation and then from the map. Afterwards, they conducted a pointing task from multiple body orientations to infer the underlying reference frames. We constructed the learning experiences in a way such that map-only learning and navigation-only learning triggered spatial memory organized along different reference frame orientations. When learning from maps before and during navigation, participants employed a map- rather than a navigation-based reference frame in the subsequent pointing task. Consequently, maps caused the employment of a map-oriented reference frame found in memory for highly familiar urban environments ruling out explanations from environmental structure or north preference. When learning from navigation first and then from the map, the pattern of results reversed and participants employed a navigation-based reference frame. The priority of learning order suggests that despite considerable difference between map and navigation learning participants did not use the more salient or in general more useful information, but relied on the reference frame established first.