The inner tube effect.

We describe a novel size illusion in which targets appear to either shrink or grow when enclosed within a narrow tube. The direction of size change is determined by the contrast step between display elements. We first noticed this effect in the context of the dynamic "rocking line" illusion (RLI), but it can also be easily seen in completely static displays. As with the RLI, the overall scale of the display seems to play an important role. We provide an online, interactive demo, enabling the reader to explore the relevant parameter space.

The rocking line illusion.

A new visual illusion is described in which a smoothly translating object appears to rock around its own center during motion. This "rocking line" illusion occurs when the object passes through contrast boundaries formed by static background elements. However, for it to appear, the spatial scale of the display must be adjusted appropriately. We provide an online demo where the effect can be experienced and relevant parameters manipulated.

Ultra-sensitive graphene membranes for microphone applications.

Microphones exploit the motion of suspended membranes to detect sound waves. Since the microphone performance can be improved by reducing the thickness and mass of its sensing membrane, graphene-based microphones are expected to outperform state-of-the-art microelectromechanical (MEMS) microphones and allow further miniaturization of the device. Here, we present a laser vibrometry study of the acoustic response of suspended multilayer graphene membranes for microphone applications. We address performance parameters relevant for acoustic sensing, including mechanical sensitivity, limit of detection and nonlinear distortion, and discuss the trade-offs and limitations in the design of graphene microphones. We demonstrate superior mechanical sensitivities of the graphene membranes, reaching more than 2 orders of magnitude higher compliances than commercial MEMS devices, and report a limit of detection as low as 15 dBSPL, which is 10-15 dB lower than that featured by current MEMS microphones.

An Acoustic Camera for Use on UAVs.

Airborne acoustic surveillance would enable and ease several applications, including security surveillance, urban and industrial noise monitoring, rescue missions, and wildlife monitoring. Airborne surveillance with an acoustic camera mounted on an airship would provide the deployment flexibility and utility required by these applications. Nevertheless, and problematically for these applications, there is not a single acoustic camera mounted on an airship yet. We make significant advances towards solving this problem by designing and constructing an acoustic camera for direct mounting on the hull of a UAV airship. The camera consists of 64 microphones, a central processing unit, and software for data acquisition and processing dedicatedly developed for far-field low-level acoustic signal detection. We demonstrate a large-aperture mock-up camera operation on the ground, although all preparations have been made to integrate the camera onto an airship. The camera has an aperture of 2 m and has been designed for surveillance from a height up to 300 m, with a spatial resolution of 12 m.

Polarity-dependent orientation illusions: Review, model, and simulations.

Polarity-dependent orientation illusions are manifested in figures in which the impression of target orientation does not depend only on geometrical relations between the elements of the figure, but also on the relations between their luminances, that is, on luminance polarities. The best-known phenomenon belonging to this class of effects is the Münsterberg/Café Wall illusion. In this paper a considerable number of examples of this type of illusions are presented, many of which are novel variants. A two-level convolutional model of such illusions is introduced, in which the first level corresponds to the stimulus input and the second level contains units fashioned after simple cells in V1, whose spatial patterns of activity represent the model's reaction to the stimulus. The main finding of numerous simulations of the model is that the figures inducing illusory impressions of tilt share a common spatial pattern of neural activation, labeled 'oblique clusters', which is absent in related non-illusory figures. Furthermore, a similar pattern is also present in simulations of figures which induce veridical impressions of tilt. The simulations suggest that the neural basis of perception of a specific degree of tilt may not be the activity of neurons tuned narrowly to that particular degree of tilt, but rather the presence of certain signature spatial patterns of activity of populations of neurons.

What Are Visual Illusions?

Visual illusions have been a popular topic of study for a long time, but in recent years, a number of authors have questioned the coherence of this notion. This article deals in depth with ways in which illusions have been, could be, and should be defined and with various criticisms and different conceptions of the notion of illusions. After a review of definitions of illusions in the relevant literature, a more comprehensive but also more restrictive framework is presented, involving both veridicality and illusoriness, and is illustrated using two variants of a 2 × 2 scheme for the presentation of illusions. Many different aspects of illusions are discussed. A set of criteria for illusionhood is listed. Criticisms of the notion of illusions are presented, commented upon, and responded to. Conceptions of illusions differing from the one advocated here are discussed. Throughout the paper, novel variations of illusions are shown, and problems with accounts of some well-known illusions are noted. Examples of strong context effects which are not considered to be illusions are presented. It is concluded that the notion of visual illusions, suitably reformulated, is still viable.

Family and Personality Predictors of Clinical Depression and Anxiety in Emerging Adults: Common, Distinctive, or a Vulnerability Continuum?

There is an ongoing debate on the relationship between depression and anxiety, but data on similarities and differences in their predictor profiles are scarce. The aim of our study was to compare family and personality predictors of these disorders among 220 "emerging adults." As such, two clinical groups with noncomorbid depressive and anxiety disorders, and one healthy control group were assessed by sociodemographic questionnaires, Structured Clinical Interview for DSM-IV Disorders and NEO Personality Inventory, Revised. We found significant overlap in family and personality risk profiles, with increasing effect size for predictors common to anxiety and depression when the categories "no disorder-anxiety disorder-depressive disorder" were considered as existing along a continuum. Among the contributing factors we assessed, family psychiatric history, family structure and conflicts with parents were more significant than personality traits. Our study indicates that emerging adults may be more vulnerable to depression than anxiety in the presence of family and personality risk factors.

Is the Ebbinghaus illusion a size contrast illusion?

The Ebbinghaus illusion, in which a central target surrounded by larger context figures looks smaller than when surrounded by smaller context figures, is usually classified as a size contrast illusion. Thus "size contrast" is the dominant account of this effect. However, according to an alternative "contour interaction" account this phenomenon has little to do with size contrast but is rather caused by distance-dependent attractive and repulsive interactions between neural representation of contours. Here evidence is presented against the size contrast account and consistent with the contour interaction account. Experiment 1 was a control study confirming that the illusion can be obtained using displays consisting only of squares, which are more convenient to manipulate than the standardly used circles. In Experiment 2, the standard configuration involving small context figures surrounding the target was compared to a novel configuration, which involved many "spread" small context figures. The illusory effect of the standard context was stronger than the illusory effect of the spread context, in accord with the prediction of the contour interaction account, and contrary to the prediction of the size contrast account. In Experiment 3 two novel configurations were used, based on standard and spread contexts. The results were in accord with the prediction of the contour interaction account, whereas the size contrast account had no prediction because the stimuli did not involve conventional size contrast. Additional aspects of the stimuli and an account of the illusion based on a perspective interpretation are also discussed.

Johann Joseph on Geometrical-Optical Illusions: A Translation and Commentary.

The term geometrical-optical illusions was coined by Johann Joseph Oppel (1815-1894) in 1855 in order to distinguish spatial distortions of size and orientation from the broader illusions of the senses. We present a translation of Oppel's article and a commentary on the material described in it. Oppel did much more than give a name to a class of visual spatial distortions. He examined a variety of figures and phenomena that were precursors of later, named illusions, and attempted to quantify and interpret them.

Multicomponent Treatment in a Day Hospital for Adolescents: A Case of Good Practice.

The dynamics of adolescence require adjustments in psychiatric treatment because of the challenges of this developmental stage in life. This column describes the Day Hospital for Adolescents (DHA) of the Institute of Mental Health in Belgrade, Serbia, which was established in December 2007. The DHA is a holistic program for the treatment of youths ages 15-25 with emotional disorders. The multicomponent therapeutic program includes individual treatment, several group therapeutic activities, and work with patients' families and the school system. An evaluation of data obtained for 102 patients indicated that DHA treatment was associated with significant reductions in depression symptom severity and improved functioning. The adolescents reported a high level of treatment satisfaction. The results suggest that a multicomponent day hospital is an effective treatment modality for adolescents with emotional disorders.

Coupled computations of three-dimensional shape and material.

Retinal image structure arises from the interaction between a surface's three-dimensional shape, its reflectance and transmittance properties, and the surrounding light field. Any local image structure can be generated by an infinite number of different combinations of surface properties, which suggests that the visual system must somehow constrain the possible scene interpretations. The research on this has searched for such constraints in statistical regularities of two-dimensional image structure [1,2]. Here, we present a new class of displays in which the perception of material properties cannot be explained with two-dimensional image properties. The displays manipulate the perceived three-dimensional shape of identical luminance gratings, and demonstrate that perceived three-dimensional shape can alter perceived surface reflectance.

How shape from contours affects shape from shading.

The spatial pattern of reflected light carries detailed but ambiguous information about 3D shapes of illuminated objects. A little studied factor that affects the perceived 3D relief of 2D shaded figures is the shape of their contours. An experiment is reported in which 102 subjects matched twelve contoured grating displays (horizontal three-cycle gratings with variously shaped top and bottom contours) with perspective line drawings of different 3D shapes, and also judged their depth extent and direction of illumination. The results showed that contour shapes can have surprisingly strong and salient effects on perceived relief. For each display there was a dominant matching drawing, chosen by the largest percentage of subjects, which varied from 95% to 26% across the set of displays. The luminance distribution of contoured gratings is essentially 1D, so that, compared to the general 2D case, their mathematical analysis is considerably simplified, and shape can in certain cases be recovered from shading in analytical form, yielding a three-parameter family of solutions. An analysis of subject responses showed that most reported reliefs had shapes which were closely related to members of the solution family. Furthermore, the particular perceived shapes of contoured gratings could with some success be predicted from the shapes of their contours, based on a simple shape-from-contours rule. However, the data also indicated the presence of a convexity tendency, independent from contour shape.

The roles of image decomposition and edge curvature in the 'snake' lightness illusion.

The snake illusion is an effect in which the lightness of target patches is strongly affected by the luminance of remote patches. One explanation is that such images are decomposed into a pattern of illumination and a pattern of reflectance, involving a classification of luminance edges into illumination and reflectance edges. Based on this decomposition, perceived reflectance is determined by discounting the illumination. A problem for this account is that image decomposition is not unique, and that different decompositions may lead to different lightness predictions. One way to rule out alternative decompositions and ensure correct predictions is to postulate that the visual system tends to classify curved luminance edges as reflectance edges rather than illumination edges. We have constructed several variations of the basic snake display in order to test the proposed curvature constraint and the more general image decomposition hypothesis. Although the results from some displays have confirmed previous findings of the effect of curvature, the general pattern of data questions the relevance of the shape of luminance edges for the determination of lightness in this class of displays. The data also argue against an image decomposition mechanism as an explanation of this effect. As an alternative, a tentative neurally based account is sketched.

Evaluation of single-point sampling strategies for the estimation of moclobemide exposure in depressive patients.

Because moclobemide pharmacokinetics vary considerably among individuals, monitoring of plasma concentrations lends insight into its pharmacokinetic behavior and enhances its rational use in clinical practice. The aim of this study was to evaluate whether single concentration-time points could adequately predict moclobemide systemic exposure. Pharmacokinetic data (full 7-point pharmacokinetic profiles), obtained from 21 depressive inpatients receiving moclobemide (150 mg 3 times daily), were randomly split into development (n = 18) and validation (n = 16) sets. Correlations between the single concentration-time points and the area under the concentration-time curve within a 6-hour dosing interval at steady-state (AUC(0-6)) were assessed by linear regression analyses. The predictive performance of single-point sampling strategies was evaluated in the validation set by mean prediction error, mean absolute error, and root mean square error. Plasma concentrations in the absorption phase yielded unsatisfactory predictions of moclobemide AUC(0-6). The best estimation of AUC(0-6) was achieved from concentrations at 4 and 6 hours following dosing. As the most reliable surrogate for moclobemide systemic exposure, concentrations at 4 and 6 hours should be used instead of predose trough concentrations as an indicator of between-patient variability and a guide for dose adjustments in specific clinical situations.

Adjacency and surroundedness in the depth effect on lightness.

Using two perpendicular planes, one brightly and one dimly illuminated, A. L. Gilchrist (1977) showed that target lightness can change nearly from black to white by changing its perceived spatial position, with no change in the retinal image, if the target has an adjacent coplanar neighbor in each position. Earlier L. Kardos (1934) found a modest depth effect for a target that was not adjacent to its coplanar neighbor but surrounded by it. Using Kardos' experimental arrangement, but articulated planes and a between-subjects design, we obtained a large depth effect on lightness without adjacency. We then explored the role of adjacency and surroundedness using Gilchrist's perpendicular planes arrangement. We replicated the large depth effect when the target was adjacent to its coplanar neighbor. However, most of this depth effect was lost when adjacency was eliminated, by moving each target within its plane away from its coplanar neighbor. When we surrounded each target by extending its non-adjacent coplanar background, half the effect provided by adjacency was restored, but only in the brightly illuminated, not the dimly illuminated plane. Our findings support the view that, to compute surface lightness, the visual system groups surfaces in the image that seem to be equally illuminated.

The effect of the observer vantage point on perceived distortions in linear perspective images.

Some features of linear perspective images may look distorted. Such distortions appear in two drawings by Jan Vredeman de Vries involving perceived elliptical, instead of circular, pillars and tilted, instead of upright, columns. Distortions may be due to factors intrinsic to the images, such as violations of the so-called Perkins's laws, or factors extrinsic to them, such as observing the images from positions different from their center of projection. When the correct projection centers for the two drawings were reconstructed, it was found that they were very close to the images and, therefore, practically unattainable in normal observation. In two experiments, enlarged versions of images were used as stimuli, making the positions of the projection centers attainable for observers. When observed from the correct positions, the perceived distortions disappeared or were greatly diminished. Distortions perceived from other positions were smaller than would be predicted by geometrical analyses, possibly due to flatness cues in the images. The results are relevant for the practical purposes of creating faithful impressions of 3-D spaces using 2-D images.

The effect of face eccentricity on the perception of gaze direction.

The perception of a looker's gaze direction depends not only on iris eccentricity (the position of the looker's irises within the sclera) but also on the orientation of the lookers' head. One among several potential cues of head orientation is face eccentricity, the position of the inner features of the face (eyes, nose, mouth) within the head contour, as viewed by the observer. For natural faces this cue is confounded with many other head-orientation cues, but in schematic faces it can be studied in isolation. Salient novel illustrations of the effectiveness of face eccentricity are 'Necker faces', which involve equal iris eccentricities but multiple perceived gaze directions. In four experiments, iris and face eccentricity in schematic faces were manipulated, revealing strong and consistent effects of face eccentricity on perceived gaze direction, with different types of tasks. An additional experiment confirmed the 'Mona Lisa' effect with this type of stimuli. Face eccentricity most likely acted as a simple but robust cue of head turn. A simple computational account of combined effects of cues of eye and head turn on perceived gaze direction is presented, including a formal condition for the perception of direct gaze. An account of the 'Mona Lisa' effect is presented.

Moclobemide monotherapy vs. combined therapy with valproic acid or carbamazepine in depressive patients: a pharmacokinetic interaction study.

WHAT IS ALREADY KNOWN ABOUT THIS SUBJECT: Moclobemide (MCB) undergoes extensive both presystemic and systemic metabolism that can be affected by concomitant drugs. Valproic acid (VPA) and carbamazepine (CBZ) have been found to interact with psychotropic medications of all classes and many other drugs; VPA acts as a broad-spectrum inhibitor, and CBZ as a potent inducer of a variety of drug-metabolizing enzymes. There have been no previous studies designed to investigate a potential pharmacokinetic (PK) interaction between MCB and VPA or CBZ; however, these agents are likely to be used concomitantly for the treatment of depressive disorders. WHAT THIS STUDY ADDS: VPA does not significantly affect PK or metabolism of MCB at steady state. CBZ significantly decreases MCB exposure. This effect is time-dependent, being more pronounced after 3-5 weeks of co-administration. AIM: To assess the impact of valproic acid (VPA) and carbamazepine (CBZ) on moclobemide (MCB) pharmacokinetics (PK) and metabolism at steady state in depressive patients. METHODS: Twenty-one inpatients with recurrent endogenous depression received MCB (150 mg t.i.d.), either as monotherapy or in combination with VPA (500 mg b.i.d.) or CBZ (200 mg b.i.d.) in a nonrandomized manner. Steady-state plasma PK parameters of MCB and its two metabolites, Ro 12-8095 and Ro 12-5637, were derived. Clinical assessments of treatment efficacy were performed weekly using standard depression rating scales. RESULTS: CBZ, but not VPA, was associated with decreases in the MCB AUC by 35% [from 7.794 to 5.038 mg h l(-1); 95% confidence interval (CI) -4.84863, -0.66194; P = 0.01] and C(max) by 28% (from 1.911 to 1.383 mg l(-1); 95% CI -0.98197, -0.07518; P < 0.05), and an increase in its oral clearance by 41% (from 0.323 to 0.454 l h(-1) kg(-1); 95% CI 0.00086, 0.26171; P < 0.05) after 4 weeks of co-administration. MCB through concentrations were also decreased, on average by 41% (from 0.950 to 0.559 mg l(-1); 95% CI -0.77479, -0.03301; P < 0.05). However, the efficacy in this group of patients was not inferior to the controls, for several possible reasons. Overall tolerability of all study medications was good. CONCLUSIONS: VPA does not significantly affect PK or metabolism of MCB, whereas CBZ time-dependently decreases MCB exposure, probably by inducing metabolism of MCB and its major plasma metabolite. The actual clinical relevance of the observed MCB-CBZ PK interaction needs to be further evaluated in a more comprehensive study.

Is pictorial perception robust? The effect of the observer vantage point on the perceived depth structure of linear-perspective images.

Every image of a scene produced in accord with the rules of linear perspective has an associated projection centre. Only if observed from that position does the image provide the stimulus which is equivalent to the one provided by the original scene. According to the perspective-transformation hypothesis, observing the image from other vantage points should result in specific transformations of the structure of the conveyed scene, whereas according to the vantage-point compensation hypothesis it should have little effect. Geometrical analyses illustrating the transformation theory are presented. An experiment is reported to confront the two theories. The results provide little support for the compensation theory and are generally in accord with the transformation theory, but also show systematic deviations from it, possibly due to cue conflict and asymmetry of visual angles.