Plasmonic Metasurface for Directional and Frequency-Selective Thermal Emission

International audienceIncandescent filaments and membranes are often used as infrared sources despite their low efficiency, broad angular emission, and lack of spectral selectivity. Here, we introduce a metasurface to control simultaneously the spectrum and the directivity of blackbody radiation. The plasmonic metasurface operates reliably at 600 °C with an emissivity higher than 0.85 in a narrow frequency band and in a narrow solid angle. This emitter paves the way for the development of compact, efficient, and cheap IR sources and gas detection systems

Contribution of Color Information in Visual Saliency Model for Videos

International audienceMuch research has been concerned with the contribution of the low level features of a visual scene to the deployment of visual attention. Bottom-up saliency models have been developed to predict the location of gaze according to these features. So far, color besides to brightness, contrast and motion is considered as one of the primary features in computing bottom-up saliency. However, its contribution in guiding eye movements when viewing natural scenes has been debated. We investigated the contribution of color information in a bottom-up visual saliency model. The model efficiency was tested using the experimental data obtained on 45 observers who were eye tracked while freely exploring a large data set of color and grayscale videos. The two datasets of recorded eye positions, for grayscale and color videos, were compared with a luminance-based saliency model. We incorporated chrominance information to the model. Results show that color information improves the performance of the saliency model in predicting eye positions

Problems with Saliency Maps

Despite the popularity that saliency models have gained in the computer vision community, they are most often conceived, exploited and benchmarked without taking heed of a number of problems and subtle issues they bring about. When saliency maps are used as proxies for the likelihood of fixating a location in a viewed scene, one such issue is the temporal dimension of visual attention deployment. Through a simple simulation it is shown how neglecting this dimension leads to results that at best cast shadows on the predictive performance of a model and its assessment via benchmarking procedures

What is the role of the film viewer? The effects of narrative comprehension and viewing task on gaze control in film

Film is ubiquitous, but the processes that guide viewers' attention while viewing film narratives are poorly understood. In fact, many film theorists and practitioners disagree on whether the film stimulus (bottom-up) or the viewer (top-down) is more important in determining how we watch movies. Reading research has shown a strong connection between eye movements and comprehension, and scene perception studies have shown strong effects of viewing tasks on eye movements, but such idiosyncratic top-down control of gaze in film would be anathema to the universal control mainstream filmmakers typically aim for. Thus, in two experiments we tested whether the eye movements and comprehension relationship similarly held in a classic film example, the famous opening scene of Orson Welles' Touch of Evil (Welles & Zugsmith, Touch of Evil, 1958). Comprehension differences were compared with more volitionally controlled task-based effects on eye movements. To investigate the effects of comprehension on eye movements during film viewing, we manipulated viewers' comprehension by starting participants at different points in a film, and then tracked their eyes. Overall, the manipulation created large differences in comprehension, but only produced modest differences in eye movements. To amplify top-down effects on eye movements, a task manipulation was designed to prioritize peripheral scene features: a map task. This task manipulation created large differences in eye movements when compared to participants freely viewing the clip for comprehension. Thus, to allow for strong, volitional top-down control of eye movements in film, task manipulations need to make features that are important to narrative comprehension irrelevant to the viewing task. The evidence provided by this experimental case study suggests that filmmakers' belief in their ability to create systematic gaze behavior across viewers is confirmed, but that this does not indicate universally similar comprehension of the film narrative

Listening to music reduces eye movements

Listening to music can change the way that people visually experience the environment, probably as a result of an inwardly directed shift of attention. We investigated whether this attentional shift can be demonstrated by reduced eye movement activity, and if so, whether that reduction depends on absorption. Participants listened to their preferred music, to unknown neutral music, or to no music while viewing a visual stimulus (a picture or a film clip). Preference and absorption were significantly higher for the preferred music than for the unknown music. Participants exhibited longer fixations, fewer saccades, and more blinks when they listened to music than when they sat in silence. However, no differences emerged between the preferred music condition and the neutral music condition. Thus, music significantly reduces eye movement activity, but an attentional shift from the outer to the inner world (i.e., to the emotions and memories evoked by the music) emerged as only one potential explanation. Other explanations, such as a shift of attention from visual to auditory input, are discussed

F77. OXYTOCIN ENHANCES VISUAL ATTENTION TO FACIAL STIMULI IN PATIENTS WITH SCHIZOPHRENIA: EVIDENCE FROM AN EYE-TRACKING STUDY

International audienceBackground: Deficits in social cognition often develop during the prod- romal stages of psychosis, remain stable over the course of the illness, and have a dramatic impact on daily functioning (Fett et al., 2011). Social cue processing, particularly face perception, plays a critical role in social cognitive functioning. Patients with schizophrenia struggle to extract information from faces and interpret facial expressions (Kohler et al., 2010). These deficits may be explained by restricted visual atten- tion. Indeed, eye-tracking studies have demonstrated that people with schizophrenia show reduced exploratory behaviour (i.e. reduced number of fixations and longer fixation durations) in response to facial stimuli compared to healthy controls (e.g. Manor et al., 1999). Oxytocin has been demonstrated to exert pro-social effects on behaviour and modu- late eye gaze during perception of faces. In the present study, we tested whether the neuropeptide, oxytocin, has a compensatory effect on visual processing of human faces.Methods: Twenty right-handed male subjects with schizophrenia (n = 16) or schizoaffective disorder (n = 4) were administered intranasal oxytocin 40UI or placebo in a double-blind, placebo-controlled, cross- over fashion during two visits separated by 7 days. Participants engaged in a free-viewing eye-tracking task, during which they were looking at 6 facial images of two Caucasian men displaying angry, happy, and neutral facial expressions, and 6 control images in a random order. Eye- tracking measures including 1) total number of fixations, 2) dispersion, 3) saccade amplitude, and 4) mean duration of fixations were captured using the EyeLink 1000 system (SR Research Ltd, Ottawa, Ontario, Canada). Four separate 2 x 4 repeated-measures analysis of variance (ANOVA) were carried out to evaluate the within-subject effects of treatment, stimuli, and the interactions between stimuli and treatment (p .231) on total number of fixations. There was a main effect of treatment on duration of fixation, (F1,13 = 5.455, p = .036) but not a main effect of stimuli (F3,39 = 1.267, p = .299). For dispersion, there was a significant main effect of stimuli (F3,51 = 3.424, p = .024) but no main effect of treatment (F1,17 = 3.170, p = .093). Analysis of saccade amplitudes revealed no main effect of treat- ment (F1,17 = 2.666, p = .121) or stimuli (F3,51 = 0.289, p = .833). None of the interactions reached significance.Discussion: To our knowledge, this is the first study to explore the effects of oxytocin on eye movements in individuals with schizophre- nia. We found that oxytocin increased exploratory viewing behaviour in response to affective facial stimuli by significantly increasing the total number and duration of fixations compared to placebo. While previous findings regarding oxytocin have been inconsistent, our findings are in line with research showing that the intranasal administration of 40UI oxytocin may improve social cognitive deficits in schizophrenia (e.g. Davis et al., 2013). Future experiments may wish to explore the corre- lation between eye movement changes induced by oxytocin and facial affect recognition in larger samples