Fused Traditional and Geometric Morphometrics Demonstrate Pinniped Whisker Diversity

Vibrissae (whiskers) are important components of the mammalian tactile sensory system, and primarily function as detectors of vibrotactile information from the environment. Pinnipeds possess the largest vibrissae among mammals and their vibrissal hair shafts demonstrate a diversity of shapes. The vibrissae of most phocid seals exhibit a beaded morphology with repeating sequences of crests and troughs along their length. However, there are few detailed analyses of pinniped vibrissal morphology, and these are limited to a few species. Therefore, we comparatively characterized differences in vibrissal hair shaft morphologies among phocid species with a beaded profile, phocid species with a smooth profile, and otariids with a smooth profile using traditional and geometric morphometric methods. Traditional morphometric measurements (peak-to-peak distance, crest width, trough width and total length) were collected using digital photographs. Elliptic Fourier analysis (geometric morphometrics) was used to quantify the outlines of whole vibrissae. The traditional and geometric morphometric datasets were subsequently combined by mathematically scaling each to true rank, followed by a single eigendecomposition. Quadratic discriminant function analysis demonstrated that 79.3, 97.8 and 100% of individuals could be correctly classified to their species based on vibrissal shape variables in the traditional, geometric and combined morphometric analyses, respectively. Phocids with beaded vibrissae, phocids with smooth vibrissae, and otariids each occupied distinct morphospace in the geometric morphometric and combined data analyses. Otariids split into two groups in the geometric morphometric analysis and gray seals appeared intermediate between beaded- and smooth-whiskered species in the traditional and combined analyses. Vibrissal hair shafts modulate the transduction of environmental stimuli to the mechanoreceptors in the follicle-sinus complex (F-SC), which results in vibrotactile reception, but it is currently unclear how the diversity of shapes affects environmental signal modulation

Matched Field Processing of Three-Component Seismic Array Data Applied to Rayleigh and Love Microseisms

We extend three‐component plane wave beamforming to a more general form and devise a framework, which incorporates velocity heterogeneities of the seismic propagation medium and allows us to estimate accurately sources that do not follow the simple plane wave assumption. This is achieved by utilizing fast marching to track seismic wave fronts for given surface wave phase velocity maps. The resulting matched field processing approach is used to study the surface wave locations of Rayleigh and Love waves at 8 and 16 s based on data from four seismic arrays in the western United States. By accurately accounting for the path propagation effects, we are able to map microseism surface wave source locations more accurately than conventional plane wave beamforming. In the primary microseisms frequency range, Love waves are dominant over Rayleigh waves and display a directional radiation pattern. In the secondary microseisms range, we find the general source regions for both wave types to be similar, but on smaller scales differences are observed. Love waves are found to originate from a larger area than Rayleigh waves and their energy is equal or slightly weaker than Rayleigh waves. The energy ratios are additionally found to be source location dependent. Potential excitation mechanisms are discussed which favor scattering from Rayleigh‐to‐Love waves

Enhancing the visually induced self-motion illusion (vection) under natural viewing conditions in virtual reality

The visually induced illusion of ego-motion (vection) is known to be facilitated by both static fixation points [1] and foreground stimuli that are perceived to be stationary in front of a moving background stimulus [2]. In this study, we found that hardly noticeable marks in the periphery of a projection screen can have similar vection-enhancing effects, even without fixating or suppressing the optokinetic reflex (OKR). Furthermore, vection was facilitated even though the marks had no physical depth separation from the screen. Presence ratings correlated positively with vection, and seemed to be mediated by the ego-motion illusion. Interestingly, the involvement/attention aspect of overall presence was more closely related to vection onset times, whereas spatial presence-related aspects were more tightly related to convincingness ratings. This study yields important implications for both presence theory and motion simulator design and applications, where one often wants to achieve convincing ego-motion simulation without restricting eye movements artificially. Keywords--- Vection, psychophysics, spatial presence, virtual reality, illusions, motion simulation

Orientation biases in memory for vista and environmental spaces

This experiment tested whether vista spaces such as rooms or plazas are encoded differently in memory compared to environmental spaces such as buildings or cities. Participants learned an immersive virtual environment by walking through it in one direction. The environment consisted of seven corridors forming a labyrinth within which target objects were located. The participants either learned this environmental space alone, or distant mountains provided additional compass information. In a third condition, this labyrinth was located within a big hall (i.e., a vista space) which allowed self-localisation with respect to the vista space of the hall. In the testing phase, participants were teleported to different locations in the environment and were asked to identify their location and heading first, and then to point towards previously learned targets. In general, participants self localized faster when oriented in the direction in which they originally learned each corridor. However, a subset of participants showed a different orientation specificity in their pointing performance originating more from the orientation of the mountains or the hall. These participants were identified in catch trials after the experiment. The results are first hints for a difference in memory for vista and environmental spaces

Place naming: examining the influence of language on wayfinding

We asked the question how language influences a presumably embodied system such as human wayfinding. To test this, participants walked along a route in a virtual environment. They were asked to remember half of the intersections by what they saw. At the other 50 of intersections they heard an arbitrary name which they also had to remember. In the test phase they were teleported to different intersections and had to indicate the direction the route went on. At intersections without a name they performed faster and more accurately. In a second experiment meaningful names were used instead. Participants now performed better at named intersection. The results indicate an interaction between language and the presumably embodied wayfinding system. This interaction cannot be explained by a limited common resource, depth of processing, overshadowing, or linguistic scaffolding. However, it is consistent with dual coding