Expectations, derived from previous experience, can help in making perception faster, more reliable and informative. A key neural signature of perceptual expectations is expectation suppression, an attenuated neural response to expected compared with unexpected stimuli. While expectation suppression has been reported using a variety of paradigms and recording methods, it remains unclear what neural modulation underlies this response attenuation. Sharpening models propose that neural populations tuned away from an expected stimulus are particularly suppressed by expectations, thereby resulting in an attenuated, but sharper population response. In contrast, dampening models suggest that neural populations tuned toward the expected stimulus are most suppressed, thus resulting in a dampened, less redundant population response. Empirical support is divided, with some studies favoring sharpening, while others support dampening. A key limitation of previous neuroimaging studies is the ability to draw inferences about neural-level modulations based on population (e.g. voxel) level signals. Indeed, recent simulations of repetition suppression showed that opposite neural modulations can lead to comparable population-level modulations. Forward models provide one solution to this inference limitation. Here, we used forward models to implement sharpening and dampening models, mapping neural modulations to voxel-level data. We show that a feature-specific gain modulation, suppressing neurons tuned toward the expected stimulus, best explains the empirical fMRI data. Thus, our results support the dampening account of expectation suppression, suggesting that expectations reduce redundancy in sensory cortex, and thereby promote updating of internal models on the basis of surprising information.

Dominant motor control theories propose that the brain predicts and attenuates the somatosensory consequences of actions, referred to as somatosensory attenuation. Support comes from psychophysical and neuroimaging studies showing that touch applied on a passive hand elicits attenuated perceptual and neural responses if it is actively generated by one\'s other hand, compared to an identical touch from an external origin. However, recent experimental findings have challenged this view by providing psychophysical evidence that the perceived intensity of touch on the passive hand is enhanced if the active hand does not receive touch simultaneously with the passive hand (somatosensory enhancement) and by further attributing attenuation to the double tactile stimulation of the hands upon contact. Here, we directly contrasted the hypotheses of the attenuation and enhancement models regarding how action influences somatosensory perception by manipulating whether the active hand contacts the passive hand. We further assessed somatosensory perception in the absence of any predictive cues in a condition that turned out to be essential for interpreting the experimental findings. In three pre-registered experiments, we demonstrate that action does not enhance the predicted touch (Experiment 1), that the previously reported \'enhancement\' effects are driven by the reference condition used (Experiment 2), and that self-generated touch is robustly attenuated regardless of whether the two hands make contact (Experiment 3). Our results provide conclusive evidence that action does not enhance but attenuates predicted touch and prompt a reappraisal of recent experimental findings upon which theoretical frameworks proposing a perceptual enhancement by action prediction are based.

A recent study by Blank, Alink and Büchel, uses multivariate neuroimaging to investigate how the human brain processes the strength of face-related expectations and explores whether these expectations are represented in the same regions that process facial stimuli. In line with predictive coding theories, their study presents compelling evidence that the brain adjusts its processing based on the certainty of expectations. This occurs exclusively within high-level face-sensitive regions, rather than across the entire processing hierarchy. Here we critically discuss these findings and outline potential directions for future research to better understand how the human brain expects, processes, and perceives images.

Digital endoscopes are connected to a video processor that applies various operations to process the image. One of those operations is edge enhancement that sharpens the image. The purpose of this study was to (1) quantify the level of edge enhancement, (2) measure the effect on sharpness and image noise, and (3) study the influence of edge enhancement on image quality perceived by ENT professionals.
Three digital flexible endoscopic systems were included. The level of edge enhancement and the influence on sharpness and noise were measured in vitro, while systematically varying the levels of edge enhancement. In vivo images were captured at identical levels of one healthy larynx. Each series of in vivo images was presented to 39 ENT professionals according to a forced pairwise comparison test, to select the image with the best image quality for diagnostic purposes. The numbers of votes were converted to a psychometric scale of just noticeable differences (JND) according to the Thurstone V model.
The maximum level of edge enhancement varied per endoscopic system and ranged from 0.8 to 1.2. Edge enhancement increased sharpness and noise. Images with edge enhancement were unanimously preferred to images without edge enhancement. The quality difference with respect to zero edge enhancement reaches an optimum at levels between 0.7 and 0.9.
Edge enhancement has a major impact on sharpness, noise, and the resulting perceived image quality. We conclude that ENT professionals benefit from this video processing and should verify if their equipment is optimally configured.
NA Laryngoscope, 134:842-847, 2024.

Predictive coding theories of visual perception assume that expectations based on prior knowledge modulate the processing of information. However, the underlying mechanisms remain debated. Some accounts propose that expectations enhance the perception of expected relative to unexpected stimuli while others assume the opposite. Recently, the opposing process theory suggested that enhanced perception of expected vs. unexpected stimuli may occur alternatively depending upon the reliability of the visual signal. When the signal is noisy, perception would be biassed toward what is expected since anything else may be too noisy to be resolved. When the signal is unambiguous, perception would be biassed toward what diverges from expectations and is more informative. Our study tested this hypothesis, using a perceptual matching task to investigate the influence of expectations on the perceived sharpness of objects in context. Participants saw two blurred images depicting the same object and had to adjust the blur level of one object to match the blur level of the other one. We manipulated the validity of expectations about objects by varying their scene context (congruent or incongruent context leading to valid or invalid expectations about the object). We also manipulated the reliability of the visual signal by varying the initial blur level of object pairs. Results showed that expectations validity differentially affected the perception of objects depending on signal reliability. Perception of validly expected objects was enhanced (sharpened) relative to unexpected objects when visual inputs were unreliable while this effect reversed to the benefit of unexpected objects when the signal was more reliable.

The most widely used method for shaping technical blades is grinding with abrasive tools made of cubic boron nitride (cBN) grains and vitrified bond. The goal of this work was to determine the effect of grinding wheel grain size (cBN grain number according to FEPA standards: B126, B181 and B251), kinematics (grinding with the circumference, face and conical surface of the wheel) and feed rate (vf = 100; 150; 200 mm/min) on the effects of the grinding process evaluated by the cutting force of the blade after machining F, blade surface texture parameters (Sa, St, Smvr, Str, Sdq, Sdr and Sbi) as well as blade surface morphology. An analysis of output quantities showed that grinding wheels made of B181 cBN grains are most favorable for shaping planar technical blades of X39Cr13 steel in the grinding process.

Flexible endoscopes are essential for medical internal examinations. Digital endoscopes are connected to a video processor that can apply various operations to enhance the image. One of those operations is edge enhancement, which has a major impact on the perceived image quality by medical professionals. However, the specific methods and parameters of this operation are undisclosed and the arbitrary units to express the level of edge enhancement differ per video processor.
Objectively quantify the level of edge enhancement from the recorded images alone, and measure the effect on sharpness and noise
Edge enhancement was studied in four types of flexible digital ear nose and throat endoscopes. Measurements were performed using slanted edges and gray patches. The level of edge enhancement was determined by subtracting the step response of an image without edge enhancement from images with selected settings of edge enhancement and measuring the resulting peak-to-peak differences. These values were then normalized by the step size. Sharpness was characterized by observing the normalized modulation transfer function (MTF) and computing the spatial frequency at 50% MTF. The noise was measured on the gray patches and computed as a weighted sum of variances from the luminance and two chrominance channels of the pixel values.
The measured levels were consistent with the level set via the user interface on the video processor and varied typically from 0 to 1.3. Both sharpness and noise increase with larger levels of edge enhancement with factors of 3 and 4 respectively.
The presented method overcomes the issue of vendors expressing the level of edge enhancement each differently in arbitrary units. This allows us to compare the effects, and we can start exploring the relationship with the subjectively perceived image quality by medical professionals to find substantiated optimal settings.

To investigate the effects of image postprocessing functions (ie, edge enhancement, noise reduction, and sharpening) that are available on digital radiography systems, including computed radiography (CR) and direct digital radiography (DDR), for detection of wooden, soft tissue foreign bodies.
Dorsoplantar and lateral porcine foot radiographs with 4 lengths of wooden foreign bodies (no foreign bodies, 2 mm, 5 mm, and 10 mm) placed 1 mm (superficial) and 1 cm (deep) below the skin were acquired by CR and DDR systems using 10 exposure factors. Images were postprocessed to produce 960 images, including original CR, original DDR, sharpened CR, sharpened DDR, edge-enhanced DDR, and noised-reduced DDR images. Contrast-to-noise ratios (CNR) were used for objective assessments of foreign body visibility on the images. Six Australian radiologic technologists were recruited to review selected images. Australia allows radiologic technologists to provide initial comments on plain radiographs with the supervision of a radiologist. Technologists rated the visibility of foreign bodies using a 4-point scale to determine diagnostic performances of different image receptor and postprocessing types. Means, standard deviations, analyses of variance, and intraclass correlation coefficients were calculated for statistical analyses.
Among the CR and DDR images with and without postprocessing, the edge-enhanced DDR images had the highest overall mean CNR value (3.39, P = .003) and sensitivity (35.13%). The sensitivity of the edge-enhanced DDR images for detecting the 10 mm foreign body was 43.33%.
Edge-enhanced DDR can be considered an additional tool for suspected wooden, soft tissue foreign body diagnoses in rural areas where digital radiography is the only available imaging modality. This would allow some patients in rural areas to avoid long-distance travel to access sonography or computed tomography to detect foreign bodies, which could minimize emotional, financial, and social costs.
This study shows that the image postprocessing function of the DDR system can detect wooden, soft tissue foreign bodies. Edge enhancement, specifically, can improve wooden, soft tissue foreign body detection, especially for large foreign bodies (≥ 10 mm).

To improve the safety of nuclear power plants, a Cr protective layer is deposited on zirconium alloys to enhance oxidation resistance of the nuclear fuel cladding during both in-service and hypothetical accidental transients at High Temperature (HT) in Light Water Reactors. The formation of the Cr2O3 film on the coating surface considerably helps in reducing the oxidation kinetics of the zirconium alloy, especially during hypothetic Loss of Coolant Accident (LOCA). However, if the Cr coating is successful to increase the oxidation resistance at HT of the zirconium substrate, for in-service conditions, under neutron irradiation, Cr desquamation has to be avoided to guarantee a safe use of the Cr-coated zirconium alloys. Therefore, the adhesion properties have to be maintained despite the structural defects created by sustained neutron irradiation in the reactor environment. This paper proposes to study the behavior of the Zircaloy-Cr interface of a first generation Cr-coated material during a specific in situ ion irradiation. As deposited, the Cr-coated sample presents a f.c.c. C15 Laves-type intermetallic phase at the interface with off-stoichiometric composition. After irradiation and for the specific conditions applied, this interfacial phase has significantly dissolved. Energy Dispersion Spectroscopy revealed that the dissolution was accompanied by a counterintuitive \"sharpening\" effect.

Electron cryomicroscopy (cryo-EM) has emerged as a powerful structural biology instrument to solve near-atomic three-dimensional structures. Despite the fast growth in the number of density maps generated from cryo-EM data, comparison tools among these reconstructions are still lacking. Current proposals to compare cryo-EM data derived volumes perform map subtraction based on adjustment of each volume grey level to the same scale. We present here a more sophisticated way of adjusting the volumes before comparing, which implies adjustment of grey level scale and spectrum energy, but keeping phases intact inside a mask and imposing the results to be strictly positive. The adjustment that we propose leaves the volumes in the same numeric frame, allowing to perform operations among the adjusted volumes in a more reliable way. This adjustment can be a preliminary step for several applications such as comparison through subtraction, map sharpening, or combination of volumes through a consensus that selects the best resolved parts of each input map. Our development might also be used as a sharpening method using an atomic model as a reference. We illustrate the applicability of this algorithm with the reconstructions derived of several experimental examples. This algorithm is implemented in Xmipp software package and its applications are user-friendly accessible through the cryo-EM image processing framework Scipion.