The amount and spectral content of the light reflected by most natural surfaces depends on the structure of the light field, the observer's viewing position, and 3D surface geometry, particularly for specular (glossy) surfaces. A growing body of data has demonstrated that perceived surface gloss can vary as a function of its 3D shape and its illumination field, but there is currently no explanation for these effects. Here, we show that the perception of gloss can be understood as a direct consequence of image properties that covary with surface geometry and the illumination field. We show that different illumination fields can generate qualitatively different patterns of interaction between perceived gloss and 3D surface geometry. Despite the complexity and variability of these interactions, we demonstrate that the perception (and misperception) of gloss is well predicted by the way that each illumination field modulates the size, contrast, sharpness, and depth of specular reflections. Our results provide a coherent explanation of the effects of extrinsic scene variables on perceived gloss, and our methods suggest a general technique for assessing the role of specific image properties in modulating our visual experience of material properties.

The main objective of this study was to determine whether bone-conducted vibration (BCV) is equally effective in activating both semicircular canal and otolith afferents in the guinea pig or whether there is preferential activation of one of these classes of vestibular afferents. To answer this question a large number (346) of single primary vestibular neurons were recorded extracellularly in anesthetized guinea pigs and were identified by their location in the vestibular nerve and classed as regular or irregular on the basis of the variability of their spontaneous discharge. If a neuron responded to angular acceleration it was classed as a semicircular canal neuron, if it responded to maintained roll or pitch tilts it was classified as an otolith neuron. Each neuron was then tested by BCV stimuli-either clicks, continuous pure tones (200-1,500 Hz) or short tone bursts (500 Hz lasting 7 ms)-delivered by a B-71 clinical bone-conduction oscillator cemented to the guinea pig's skull. All stimulus intensities were referred to that animal's own auditory brainstem response (ABR) threshold to BCV clicks, and the maximum intensity used was within the animal's physiological range and was usually around 70 dB above BCV threshold. In addition two sensitive single axis linear accelerometers cemented to the skull gave absolute values of the stimulus acceleration in the rostro-caudal direction. The criterion for a neuron being classed as activated was an audible, stimulus-locked increase in firing rate (a 10% change was easily detectable) in response to the BCV stimulus. At the stimulus levels used in this study, semicircular canal neurons, both regular and irregular, were insensitive to BCV stimuli and very few responded: only nine of 189 semicircular canal neurons tested (4.7%) showed a detectable increase in firing in response to BCV stimuli up to the maximum 2 V peak-to-peak level we delivered to the B-71 oscillator (which produced a peak-to-peak skull acceleration of around 6-8 g and was usually around 60-70 dB above the animal's own ABR threshold for BCV clicks). Regular otolithic afferents likewise had a poor response; only 14 of 99 tested (14.1%) showed any increase in firing rate up to the maximum BCV stimulus level. However, most irregular otolithic afferents (82.8%) showed a clear increase in firing rate in response to BCV stimuli: of the 58 irregular otolith neurons tested, 48 were activated, with some being activated at very low intensities (only about 10 dB above the animal's ABR threshold to BCV clicks). Most of the activated otolith afferents were in the superior division of the vestibular nerve and were probably utricular afferents. That was confirmed by evidence using juxtacellular injection of neurobiotin near BCV activated neurons to trace their site of origin to the utricular macula. We conclude there is a very clear preference for irregular otolith afferents to be activated selectively by BCV stimuli at low stimulus levels and that BCV stimuli activate some utricular irregular afferent neurons. The BCV ge...

A fundamental problem in image analysis is to understand the nature of the computations and mechanisms that provide information about the material properties of surfaces. Information about a surface's 3D shape, optics, illumination field, and atmospheric conditions are conflated in the image, which must somehow be disentangled to derive the properties of surfaces. It was recently suggested that the visual system exploits some simple image statistics-histogram or sub-band skew-to infer the lightness and gloss of surfaces (I. Motoyoshi, S. Nishida, L. Sharan, & E. H. Adelson, 2007). Here, we show that the correlations Motoyoshi et al. (2007) observed between skew, lightness, and gloss only arose because of the limited space of surface geometries, reflectance properties, and illumination fields they evaluated. We argue that the lightness effects they reported were a statistical artifact of equating the means of images with skewed histograms, and that the perception of gloss requires an analysis of the consistency between the estimate of a surface's 3D shape and the positions and orientations of highlights on a surface. We argue that the derivation of surface and material properties requires a photo-geometric analysis, and that purely photometric statistics such as skew fail to capture any diagnostic information about surfaces because they are devoid of the structural information needed to distinguish different types of surface attributes.

The singlet fission (SF) process is generally defined as the conversion of one singlet exciton (S1) into two triplet excitons (2·T1), which has the potential to overcome thermalization losses in the field of photovoltaic devices. Among the applicable compounds for SF-based photovoltaic devices, perylene bisimide (PBI) is one of the best candidates because of its electronic tunability and photostability. However, the strategy for efficient SF in PBIs remains ambiguous because of numerous competing relaxation pathways in PBI-based molecular materials. In this regard, for the first time, we observed the SF mechanism in PBI dimers by controlling the intrinsic factor (exciton coupling) and the external environment (solvent polarity and viscosity). Time-resolved spectroscopic measurements and quantum chemical simulations reveal that efficient SF occurs through the charge-transfer-assisted mechanism, entailing a large structural fluctuation. Our findings not only highlight the SF mechanism in PBI dimers but also suggest the factors responsible for an efficient SF process, which are important considerations in the design of molecular materials for photovoltaic devices.

Cybersickness is often experienced when viewing virtual environments through head-mounted displays (HMDs). This study examined whether vection (i.e., illusory self-motion) and mismatches between perceived and physical head motions contribute to such adverse experiences. Observers made oscillatory yaw head rotations while viewing stereoscopic optic flow through an Oculus Rift HMD. Vection and cybersickness were measured under 3 conditions of visual compensation for physical head movements: "compensated", "uncompensated", and "inversely compensated". When a nearer aperture was simulated by the HMD, vection was found to be strongest in the "compensated" condition and weakest in the "inversely compensated" condition. However, vection was similar for all 3 conditions during full-field exposures. Cybersickness was most severe for the "inversely compensated" condition, but was not different for the other two conditions. We conclude that mismatches between perceived and physical head-movements can contribute strongly to cybersickness. The relationship between vection and cybersickness is weaker and appears complex. Cybersickness is often experienced when viewing virtual environments through headmounted displays (HMDs). This study examined whether vection (i.e., illusory self-motion) and mismatches between perceived and physical head motions contribute to such adverse experiences. Observers made oscillatory yaw head rotations while viewing stereoscopic optic flow through an Oculus Rift HMD. Vection and cybersickness were measured under 3 conditions of visual compensation for physical head movements: "compensated", "uncompensated", and "inversely compensated". When a nearer aperture was simulated by the HMD, vection was found to be strongest in the "compensated" condition and weakest in the "inversely compensated" condition. However, vection was similar for all 3 conditions during full-field exposures. Cybersickness was most severe for the "inversely compensated" condition, but was not different for the other two conditions. We conclude that mismatches between perceived and physical head-movements can contribute strongly to cybersickness. The relationship between vection and cybersickness is weaker and appears complex.

Studies have shown that displacing specular highlights from their natural locations in images reduces perceived surface gloss. Here, we assessed the extent to which perceived gloss depends on congruence in the position and orientation of specular highlights relative to surface shape and the diffuse shading from which surface shape is recovered. The position and orientation congruence of specular highlights with diffuse shading was altered while preserving their compatibility with physical surface shape (Experiment 1). We found that perceived gloss diminished as the position of highlights became incompatible wit h the surface's global diffuse shading maxima. In a subsequent experiment, we constrained highlight proximity near the global luminance maxima in diffuse shading. When we disrupted the consistency in the local position and orientation of specular highlights with respect to the diffuse shading and local surface meso-structure, a decline in perceived gloss was still observed (Experiment 2). This decline in perceived gloss caused by misaligning the positions and orientations of specular highlights relative to diffuse surface shading could not be explained by differences in orientation fields alone (Experiments 3 and 4). These results suggest the visual system assesses both position and orientation congruence between specular highlights and diffuse shading to estimate surface gloss.

Summary We have created a mouse genetic model that mimics a human mutation of Shank3 that deletes the C-terminus and is associated with autism. Expressed as a single copy [Shank3(+/ΔC) mice], Shank3ΔC protein interacts with the WT gene product and results in >90 % reduction of Shank3 at synapses. This “gain of function” phenotype is linked to increased polyubiquitination of WT Shank3 and its redistribution into proteasomes. Similarly, the NR1 subunit of the NMDA receptor is reduced at synapses with increased polyubiquitination. Assays of post-synaptic density proteins, spine morphology and synapse number are unchanged in Shank3(+/ΔC) mice, but the amplitude of NMDAR responses is reduced together with reduced NMDAR-dependent LTP and LTD. Reciprocally, mGluR-dependent LTD is markedly enhanced. Shank3(+/ΔC) mice show behavioral deficits suggestive of autism and reduced NMDA receptor function. These studies reveal a mechanism distinct from haploinsufficiency by which mutations of Shank3 can evoke an autism-like disorder.

The perception of surface gloss depends on specular highlights but little is understood about how the visual system distinguishes specular highlights from other luminance maxima generated by variations in pigmentation or illumination. It has been argued that diffuse shading gradients provide information for identifying specular highlights. Specular highlights typically share the orientation of the diffuse shading locally. Specular highlights are typically proximal to the brightest region of the diffuse shading locally. We compared the contributions of these two relationships to perceived gloss. Highlight orientation relative to the diffuse shading was varied by rotating highlights. Highlight distance from the brightest region of the diffuse shading was varied by translating highlights in displays that preserved the orientations of highlights relative to their surrounds. Both manipulations reduced perceived gloss. Rotations reduced perceived gloss more than translations, even though translations displaced highlights into darker regions than rotations. The same reductions in perceived gloss occurred when highlights were matched in perceived contrast across conditions (Experiment 2b). The results provide evidence that the perception of gloss depends on highlight distance from the luminance maxima of the surrounding intensity gradient (brightness congruence) in addition to the shared orientation of highlights with their surrounds (orientation congruence).