We have developed a method to visualize matrix-assisted laser desorption ionization imaging mass spectrometry (MALDI IMS) data aligned with optically determinable tissue structures in three dimensions. Details of the methodology are exemplified using the 3-D reconstruction of myelin basic protein (MBP) in the corpus callosum of a mouse brain. In this procedure, optical images obtained from serial coronal sections are first aligned to each other to reconstruct a surface of the corpus callosum from segmented contours of the aligned images. The MALDI IMS data are then coregistered to the optical images and superimposed into the surface to create the final 3-D visualization. Correlating proteomic data with anatomical structures provides a more comprehensive understanding of healthy and pathological brain functions, and holds promise to be utilized in more complex anatomical arrangements. (J Am Soc Mass Spectrom 2005, 16, 1093-1099

Virtual Environments presented through head-mounted displays (HMDs) are often explored on foot. Exploration on foot is useful since the afferent and efferent cues of physical locomotion aid spatial awareness. However, the size of the virtual environment that can be explored on foot is limited to the dimensions of the tracking space of the HMD unless other strategies are used. This paper presents a system for exploring a large virtual environment on foot when the size of the physical surroundings is small by leveraging people's natural ability to spatially update. This paper presents three methods of "resetting" users when they reach the physical limits of the HMD tracking system. Resetting involves manipulating the users' location in physical space to move them out of the path of the physical obstruction while maintaining their spatial awareness of the virtual space.

Abstract. Physical rotations and translations are the basic constituents of navigation behavior, yet there is mixed evidence about their relative importance for complex navigation in virtual reality (VR). In the present experiment, 24 participants wore head-mounted displays and performed navigational search tasks with rotations/translations controlled by physical motion or joystick. As expected, physical walking showed performance benefits over joystick navigation. Controlling translations via joystick and rotations via physical rotations led to better performance than joystick navigation, and yielded almost comparable performance to actual walking in terms of search efficiency and time. Walking resulted, however, in increased viewpoint changes and shorter navigation paths, suggesting a rotation/translation tradeoff and different navigation strategies. While previous studies have emphasized the importance of full physical motion via walking (Ruddle & Lessels, 2006, our data suggests that considerable navigation improvements can already be gained by allowing for full-body rotations, without the considerable cost, space, tracking, and safety requirements of free-space walking setups.

Navigating through large virtual environments using a headmounted display (HMD) is difficult due to the spatial limitations of the tracking system. We conducted two experiments to examine methods of exploring large virtual spaces with an HMD under translation conditions different than normal walking. Experiment 1 compares locomotion in the virtual environment using two different motor actions to translate the subject. The study contrasts user learning and orientation of two different translational gains of bipedal locomotion (not scaled and scaled by ten) with joystick locomotion, where rotation in both locomotion interfaces is accomplished by physically turning. Experiment 2 looks further at the effects of increasing the translational gain of bipedal locomotion in a virtual environment. A subject's spatial learning and orientation were evaluated in three gain conditions where each physical step was: not scaled, scaled by two, or scaled by ten (1:1, 2:1, 10:1, respectively). A sub-study of this experiment compared the performance of people who played video games against people who did not.