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This study presents the horizontal spatial specifications required for developing ideal head-mounted displays (HMDs) that provide visual experiences indistinguishable from those obtained without wearing HMDs. We investigated the minimum specifications for pixel density and field of view (FoV) such that users cannot perceive any degradation in these aspects. Conventional studies have measured visual acuity in the periphery and FoV size without eye movement. However, these results are not sufficient to determine the spatial specifications because users may notice a degradation in the quality of images displayed in the periphery when shifting their gaze away from the front. In this study, we measured visual characteristics under practical conditions, wherein participants moved their eyes naturally in coordination with their head movements, as observed when viewing natural scenes. Using a cylindrical display that covered the participant's entire horizontal visual field with high resolution images, we asked participants to identify degraded spatial resolution or narrowed FoV. Results showed that ideal HMDs do not have to provide spatial frequency components above 0.5 and 2 cycles per degree outside the visual fields of approximately 210° and 120° horizontally, respectively. These results suggest that a resolution equivalent to one-fifteenth of the frontal area is sufficient for the lateral areas of the head. In addition, we found that ideal HMDs require a FoV of at least 240°. This is considerably smaller than a naive estimate of 310° based on previous studies, obtained by integrating the FoV size during fixation and the movable range of the eyes. We believe that these findings will be helpful in developing ideal HMDs. [ABSTRACT FROM AUTHOR]

The subcortical visual pathway to the amygdala has long been considered a rapid and crude stream for processing emotionally salient information that is reliant on low spatial frequency (LSF) information. Recently, research has called this LSF dependency into question. To resolve this debate, we take advantage of an anatomical hemiretinal asymmetry, whereby the nasal hemiretina sends a higher proportion of information through the subcortical pathway than the temporal hemiretina. We recorded brain activity using electroencephalography (EEG) in human participants (N = 40) while they completed a monocular viewing paradigm. Pairs of faces (one fearful and one neutral, or both neutral) were projected simultaneously to the nasal and temporal hemiretina in three contrast-equated blocks; faces filtered to display only (i) LSF, (ii) high spatial frequency (HSF), or (iii) unfiltered information (broadband spatial frequency; BSF). BSF fearful faces were found to produce a greater naso-temporal asymmetry, with greater N170 amplitudes evoked by BSF faces in the nasal field, compared to HSF faces. Conversely, the naso-temporal asymmetry for LSF fearful faces did not differ between BSF and HSF. Collectively, these findings provide crucial evidence that the subcortical pathway carries combined spatial frequency visual signals, with a potential bias against HSF content. [ABSTRACT FROM AUTHOR]

Previous studies have shown that the spatial frequency (SF) of visual stimuli alters the perceived timing of subjective simultaneity. However, these studies have been limited to the effects of a single SF component. In this study, I measured and compared the points of subjective simultaneity (PSS) for audiovisual stimuli among low, high, and composited SF components. This experiment comprised a dual-presentation timing task and a ternary response format to eliminate response bias. The results indicated that the PSS value of the composition-SF stimuli was more toward visual-lead timing than the low-SF stimuli and did not differ significantly from that of the high-SF stimuli. The correlation coefficients showed that the PSS in composition-SF stimuli marginally approximated that of high-SF stimuli higher than that of low-SF stimuli. Future studies are needed to confirm these findings using visual stimuli with a wider range of SF components and with a modulated contrast. [ABSTRACT FROM AUTHOR]

Objective: This study aimed to examine the spatiotemporal coherence of capillary lumen fluctuations in relation to spatial variations in the pericyte lining in the cortex of anesthetized mice. Methods: Two‐photon microscopic angiography data (previously published) were reanalyzed, and spatial variations in capillary diameter fluctuations at rest and in capillary lining with vascular mural cells were measured along capillary centerlines. Results: Relatively large diameters of the capillaries (5.5 μm) coincided with a dense pericyte lining, while small capillaries (4.3 μm) had a sparse pericyte lining. Temporal variations had a frequency of about 0.1 Hz with an amplitude of 0.5 μm, which were negatively correlated with pericyte lining density. Spatial frequency analysis further revealed a common pattern of spatial variations in capillary diameter and pericyte lining, but temporal variations differed. The temporal variations in capillary lumens were locally distinct from those in neighboring locations, suggesting intrinsic fluctuations independent of the pericyte lining. Conclusions: Capillary lumens in the brain exhibit slow microfluctuations that are independent of pericyte lining. These microfluctuations could affect the distribution of flowing blood cells and may be important for homogenizing their distribution in capillary networks. [ABSTRACT FROM AUTHOR]

Introduction: The aim of this prospective and comparative study was to investigate the association of perimetry parameters on visual acuity and contrast sensitivity in primary open-angle glaucoma (POAG) eyes with diffractive extended depth-of-focus (EDoF) and monofocal intraocular lenses (IOLs). Methods: In cataract eyes with medicinally controlled POAG with no defects in the central visual field and mean deviation (MD) values of − 10 dB or better, EDoF and monofocal IOLs with the same platform except for echelette optics for EDoF were implanted in 22 and 24 eyes, respectively. Corrected distance visual acuity (CDVA), contrast sensitivity at 3 to 18 cycles per degree (cpd), and automated perimetry using 30-2 and 10-2 Swedish Interactive Threshold Algorithm programs were examined 3 months postoperatively. The influences of perimetry parameters including MD, foveal sensitivity (FS), and the means of the central four points (central MD and central FS) on CDVA and contrast sensitivity were evaluated using linear and multiple regression analyses. Results: In POAG eyes with EDoF IOLs, contrast sensitivities at 12 and 18 cpd were associated with 30-2 and 10-2 perimetry parameters. In POAG eyes with monofocal IOLs, associations of 30-2 parameters were found in CDVA and 3-cpd contrast sensitivity. Conclusions: The visual function of POAG eyes with EDoF IOLs was associated with perimetry parameters in high spatial frequency contrast sensitivity, which was different from that of POAG eyes with monofocal IOL. Trial Registration: Japan Registry for Clinical Research: jRCTs032200218. [ABSTRACT FROM AUTHOR]

This study investigates the neural processing of other-race and other-species faces, using spatial frequencies (SFs) to probe into early visual processing mechanisms. We conducted a basic classification task to reveal fundamental aspects of facial processing without the complexity of higher-order recognition tasks. This approach utilized SFs set at low (LSF, 0.53 cycles per degree [cpd]), broadband (BB), and high (HSF, 2.1 cpd) SFs to examine their impact on the both P100 and N170 components of event-related potentials. Our findings revealed a significant latency difference in the N170 component under HSF conditions, indicating race-specific efficiency in processing fine details between Asian and Caucasian faces. Furthermore, N170 amplitudes were consistently larger for human than monkey faces, with this difference more pronounced in LSF and BB conditions. This finding indicates that the other-species effect in early visual processing is more pronounced in holistic processing (LSF and BB conditions) rather than in fine-detail processing. [ABSTRACT FROM AUTHOR]

In the domain of multi-focus (MF) and multi-model image fusion (MMIF), accurately merging focused regions from various images remains a challenge. Existing methods often fall short of capturing the nuances of depth-of-field variations, leading to sub-optimal fusion outcomes. This research introduces a novel approach, utilizing both supervised and unsupervised deep learning techniques. Unlike conventional methods, the proposed model explores the realm of deep learning. to decode sharpness dynamics and activity levels, thereby enhancing the fusion process. This innovative fusion method aims to bridge the gap between modern and traditional image processing techniques, promising a breakthrough in MF image fusion and MMIF performance. Previous methods have struggled with depth-of-field variations and failed to achieve optimal fusion outcomes in the context of multi-focus and multi-model image fusion (MF and MMIF). The existing approaches cannot often capture the intricate details required for accurate merging, highlighting the need for a more advanced solution. The proposed solution introduces a novel semi-supervised deep learning model utilizing spatial frequency analysis for brain image fusion. A convolutional neural network (CNN) is employed for feature extraction, specifically designed for learning MF and multi-model images. Spatial frequency is leveraged to assess the activity level of deep features, ensuring enhanced fusion outcomes. The CNN architecture is optimized with a 5-convolutional layer cascade, omitting pooling layers for efficient deep feature extraction. The fusion strategy incorporates decision maps derived from spatial frequency-based consistency validation, contributing to improved accuracy. Evaluation using SSIM and PSNR against various fusion methods demonstrates the superior performance of the proposed model. Experimental results show that the proposed model outperforms existing methods, demonstrating its effectiveness in brain image fusion. [ABSTRACT FROM AUTHOR]

The benefits of femtosecond laser-assisted in situ keratomileusis (FS-LASIK) for correcting vision, particularly in terms of spherical equivalent (SE) and visual acuity (VA), have gained broad recognition. Nevertheless, it has remained uncertain whether FS-LASIK has a positive impact on contrast sensitivity (CS). In this study, we measured CS on seven participants by the quick contrast sensitivity function (qCSF) and compared CS before and after the surgery at two time points (1 day and 7 days after) by the repeated measures analysis of variance (ANOVA). Then, we clarified the underlying mechanisms using the perceptual template model (PTM). Furthermore, we investigated the relationship among SE, VA, and CS employing the Pearson correlation test. We found that (1) CS exhibited significant improvements on postoperative day 1, with further enhancements observed up to postoperative day 7, (2) CS improvements were dependent on spatial frequency (SF) and external noise, (3) CS improvements were attributed to the reduction of internal noise and the enhancement of the perceptual template, (4) VA and SE demonstrated significant improvement postsurgery, and (5) no significant correlations were observed among SE, VA, and CS, possibly due to limitations in sample size and lighting conditions. These findings contribute to our comprehension of FS-LASIK and provide a great indicator for assessing the outcomes of visual surgery. [ABSTRACT FROM AUTHOR]

Abstract Introduction The aim of this prospective and comparative study was to investigate the association of perimetry parameters on visual acuity and contrast sensitivity in primary open-angle glaucoma (POAG) eyes with diffractive extended depth-of-focus (EDoF) and monofocal intraocular lenses (IOLs). Methods In cataract eyes with medicinally controlled POAG with no defects in the central visual field and mean deviation (MD) values of − 10 dB or better, EDoF and monofocal IOLs with the same platform except for echelette optics for EDoF were implanted in 22 and 24 eyes, respectively. Corrected distance visual acuity (CDVA), contrast sensitivity at 3 to 18 cycles per degree (cpd), and automated perimetry using 30-2 and 10-2 Swedish Interactive Threshold Algorithm programs were examined 3 months postoperatively. The influences of perimetry parameters including MD, foveal sensitivity (FS), and the means of the central four points (central MD and central FS) on CDVA and contrast sensitivity were evaluated using linear and multiple regression analyses. Results In POAG eyes with EDoF IOLs, contrast sensitivities at 12 and 18 cpd were associated with 30-2 and 10-2 perimetry parameters. In POAG eyes with monofocal IOLs, associations of 30-2 parameters were found in CDVA and 3-cpd contrast sensitivity. Conclusions The visual function of POAG eyes with EDoF IOLs was associated with perimetry parameters in high spatial frequency contrast sensitivity, which was different from that of POAG eyes with monofocal IOL. Trial Registration Japan Registry for Clinical Research: jRCTs032200218.

Human and artificial features that coexist in certain types of human-like robots create a discrepancy in perceived humanness and evoke uncanny feelings in human observers. However, whether this perceptual mismatch in humanness occurs for all faces, and whether it is related to the uncanny feelings toward them, is unknown. We investigated this by examining perceived humanness for a variety of natural images of robot and human faces with different spatial frequency (SF) information: that is, faces with only low SF, middle SF, and high SF information, and intact (spatially unfiltered) faces. Uncanny feelings elicited by these faces were also measured. The results showed perceptual mismatches that LSF, MSF, and HSF faces were perceived as more human than intact faces. This was particularly true for intact robot faces that looked slightly human, which tended to evoke strong uncanny feelings. Importantly, the mismatch in perceived humanness between the intact and spatially filtered faces was positively correlated with uncanny feelings toward intact faces. Given that the human visual system performs SF analysis when processing faces, the perceptual mismatches observed in this study likely occur in real life for all faces, and as such might be a ubiquitous source of uncanny feelings in real-life situations. [ABSTRACT FROM AUTHOR]

Despite their young age, zebrafish larvae have a well-developed visual system and can distinguish between different visual stimuli. First, we investigated if the first visual surroundings the larvae experience during the first days after hatching shape their habitat preference. Indeed, these animals seem to "imprint" on the first surroundings they see and select visual stimuli accordingly at 7 days post fertilization (dpf). In particular, if zebrafish larvae experience a bar background just after hatching, they later on prefer bars over white stimuli, and vice versa. We then used this acquired preference for bars to investigate innate numerical abilities. We wanted to specifically test if the zebrafish larvae show real numerical abilities or if they rely on a lower-level mechanism—i.e. spatial frequency—to discriminate between two different numerosities. When we matched the spatial frequency in stimuli with different numbers of bars, the larvae reliably selected the higher numerosity. A previous study has ruled out that 7 dpf zebrafish larvae use convex hull, cumulative surface area and density to choose between two numerosities. Therefore, our results indicate that zebrafish larvae rely on real numerical abilities rather than other cues, including spatial frequency, when spontaneously comparing two sets with different numbers of bars. [ABSTRACT FROM AUTHOR]

The spatial frequency (SF) content of an object’s texture is an important cue for depth perception, although less is known about the role of background texture. Here, we used bandpass-filtered noise patterns to systematically study the interactions between target and background textures in a virtual environment. During the trials, three square targets were presented at 3 m against a background wall 6 m away from the observer. One of the squares was presented closer than the other two, and the subjects had to indicate it with a key press. The threshold distance from the two reference tiles was determined using a staircase procedure. Both the target and background were tested with different combinations of SF textures and a non-textured gray, which were rendered onto the flat surfaces. Against a gray background, the distance thresholds were smallest when the targets were presented with a mid-SF texture. Performance declined significantly with a non-textured target against a textured background. With different combinations of target-background texture, the background texture significantly affected the performance. We propose several hypotheses to explain the behavioral result. Understanding the effect of surrounding texture can be useful in improving the depth perception experience in virtual reality. [ABSTRACT FROM AUTHOR]

This study presents the horizontal spatial specifications required for developing ideal head-mounted displays (HMDs) that provide visual experiences indistinguishable from those obtained without wearing HMDs. We investigated the minimum specifications for pixel density and field of view (FoV) such that users cannot perceive any degradation in these aspects. Conventional studies have measured visual acuity in the periphery and FoV size without eye movement. However, these results are not sufficient to determine the spatial specifications because users may notice a degradation in the quality of images displayed in the periphery when shifting their gaze away from the front. In this study, we measured visual characteristics under practical conditions, wherein participants moved their eyes naturally in coordination with their head movements, as observed when viewing natural scenes. Using a cylindrical display that covered the participant’s entire horizontal visual field with high resolution images, we asked participants to identify degraded spatial resolution or narrowed FoV. Results showed that ideal HMDs do not have to provide spatial frequency components above 0.5 and 2 cycles per degree outside the visual fields of approximately 210° and 120° horizontally, respectively. These results suggest that a resolution equivalent to one-fifteenth of the frontal area is sufficient for the lateral areas of the head. In addition, we found that ideal HMDs require a FoV of at least 240°. This is considerably smaller than a naive estimate of 310° based on previous studies, obtained by integrating the FoV size during fixation and the movable range of the eyes. We believe that these findings will be helpful in developing ideal HMDs.

When viewing the mini‐LED display screen from a large angle, the seam appearing at the edge of the module can disrupt the uniformity of the entire screen's bright state. This paper studies the formation mechanism of bright and dark seam and color seam from the perspectives of spatial frequency and packaging structure, derives the formula for spatial frequency, analyzes the optical path at the splicing position, and designs a reasonable packaging film structure to solve the color seam. [ABSTRACT FROM AUTHOR]

The main objective of image fusion for multimodal medical images is to retrieve valuable information by combining multiple images obtained from various sources into a single image suitable for better diagnosis. In general, the visibility of structural details in medical images is difficult to interpret. The vast majority of the best in class image fusing systems are based on non-fuzzy sets, and the fused image so obtained lags with complementary information. Soft computing techniques like fuzzy sets have been applied to enhance the medical images and to extract the visibility features from the images. Fuzzy sets are strong-minded to be more appropriate for medical image processing as more hesitations are considered compared with non-fuzzy sets. Type-2 fuzzy sets are used in this work. Type-2 fuzzy sets are the fuzzy sets for which the membership function is not a single value for every element but an interval. In this paper, a procedure for efficiently fusing multimodal medical images is presented. In the proposed method, images are initially converted into Type-2 fuzzy images. Next, the enhanced images are decomposed into blocks and the blocks are compared using fitness function, contrast visibility (CV). Then, a decision map (DM) is built by taking the decision for each coefficient using the contrast visibility of the respective block. Then, teaching learning based optimization (TLBO) is introduced to optimize combination factors that change under teaching phase, and learner phase of TLBO. Finally, the fused image is achieved using optimal coefficients. Simulations on several pairs of multimodal medical images are performed and matched with the current fusion approaches. The dominance of the proposed technique is presented and is justified. Fused image quality is also verified with various quality metrics, such as peak signal to noise ratio (PSNR), universal quality index (UQI), structural similarity (SSIM), correlation coefficient (CC), entropy (E), spatial frequency (SF), edge information preservation (QAB/F) and standard deviation (SD). [ABSTRACT FROM AUTHOR]

Pan‐sharpening is an image fusion approach that combines the spectral information in multispectral (MS) images with the spatial properties of PAN (Panchromatic) images. This vital technique is used in categorization, detection, and other remote sensing applications. In the first step, the article focuses on increasing the finer spatial details in the MS image with PAN images using two levels of fusion without causing spectral deterioration. The suggested fusion method efficiently utilizes image transformation techniques and spatial domain image fusion methods. The luminance component of MS images typically contains spatial features that are not as detailed as the PAN images. A multiscale transform is applied to the intensity/luminance component and PAN image to introduce features into the intensity component. In the first level of processing, coefficients obtained from the non‐subsampled contourlet transform are subjected to particle swarm optimization weighted block‐based fusion. The second level of fusion is carried out using the concept of spatial frequency to reduce spectral distortion. Numerous reference and non‐reference parameters are used to evaluate the sharpened image's quality. In the next step, the article focuses on designing an evaluation metric for analysing spectral distortion based on the Bhattacharyya coefficient and distance. The Bhattacharyya coefficient and distance are calculated for each segmented region to assess the sharpened images' quality. Spectral degradation analysis using proposed techniques can also be useful for analysing materials in the segmented regions. The research findings demonstrate that the spatial features of fused images obtained from the proposed technique increased with the least spectral degradation. [ABSTRACT FROM AUTHOR]

Human visual performance for basic visual dimensions (e.g., contrast sensitivity and acuity) peaks at the fovea and decreases with eccentricity. The eccentricity effect is related to the larger visual cortical surface area corresponding to the fovea, but it is unknown if differential feature tuning contributes to this eccentricity effect. Here, we investigated two system-level computations underlying the eccentricity effect: featural representation (tuning) and internal noise. Observers (both sexes) detected a Gabor embedded in filtered white noise which appeared at the fovea or one of four perifoveal locations. We used psychophysical reverse correlation to estimate the weights assigned by the visual system to a range of orientations and spatial frequencies (SFs) in noisy stimuli, which are conventionally interpreted as perceptual sensitivity to the corresponding features. We found higher sensitivity to task-relevant orientations and SFs at the fovea than that at the perifovea, and no difference in selectivity for either orientation or SF. Concurrently, we measured response consistency using a double-pass method, which allowed us to infer the level of internal noise by implementing a noisy observer model. We found lower internal noise at the fovea than that at the perifovea. Finally, individual variability in contrast sensitivity correlated with sensitivity to and selectivity for task-relevant features as well as with internal noise. Moreover, the behavioral eccentricity effect mainly reflects the foveal advantage in orientation sensitivity compared with other computations. These findings suggest that the eccentricity effect stems from a better representation of task-relevant features and lower internal noise at the fovea than that at the perifovea. [ABSTRACT FROM AUTHOR]

When observing a simple visual scene such as an array of dots, observers can easily and automatically extract their number. How does our visual system accomplish this? We investigate the role of specific spatial frequencies to the encoding of number through cross-adaptation. In two experiments, observers were peripherally adapted to six randomly generated sinusoidal gratings varying from relatively low-spatial frequency (M = 0.44 c/deg) to relatively high-spatial frequency (M = 5.88 c/deg). Subsequently, observers judged which side of the screen had a higher number of dots. We found a strong number-adaptation effect to low-spatial frequency gratings (i.e., participants significantly underestimated the number of dots on the adapted side) but a significantly reduced adaptation effect for high-spatial frequency gratings. Various control conditions demonstrate that these effects are not due to a generic response bias for the adapted side, nor moderated by dot size or spacing effects. In a third experiment, we observed no cross-adaptation for centrally presented gratings. Our results show that observers' peripheral number perception can be adapted even with stimuli lacking any numeric or segmented object information and that low spatial frequencies adapt peripheral number perception more than high ones. Together, our results are consistent with recent number perception models that suggest a key role for spatial frequency in the extraction of number from the visual signal (e.g., Paul, Ackooij, Ten Cate, & Harvey, 2022), but additionally suggest that some spatial frequencies – especially in the low range and in the periphery – may be weighted more by the visual system when estimating number. We argue that the cross-adaptation paradigm is also a useful methodology for discovering the primitives of visual number encoding. [ABSTRACT FROM AUTHOR]

Introduction: Visual perception is a complex process that involves the analysis of different spatial and temporal features of the visual environment. One critical aspect of this process is adaptation, which allows the visual system to adjust its sensitivity to specific features based on the context of the environment. Numerous theories highlight the significance of the visual scene and its spectral properties in perceptual and adaptation mechanisms. For example, size perception is known to be influenced by the spatial frequency content of the visual scene. Nonetheless, several inquiries still exist, including how specific spectral properties of the scene play a role in size perception and adaptation mechanisms. Methods: In this study, we explore aftereffects on size perception following adaptation to a natural scene with a biased spectral amplitude distribution. Twenty participants had to manually estimate the horizontal size of a projected rectangle after adaptation to three visually biased conditions: verticalbiased, non-biased, and horizontal-biased. Size adaptation aftereffects were quantified by comparing the perceptual responses from the non-biased condition with the vertical- and horizontal-biased conditions. Results: We found size perception shifts which were contingent upon the specific orientation and spatial frequency distribution inherent in the amplitude spectra of the adaptation stimuli. Particularly, adaptation to vertical-biased produced a horizontal enlargement, while adaptation to horizontal-biased generated a decrease in the horizontal size perception of the rectangle. On average, size perception was modulated by 5–6%. Discussion: These findings provide supporting evidence for the hypothesis that the neural mechanisms responsible for processing spatial frequency channels are involved in the encoding and perception of size information. The implications for neural mechanisms underlying spatial frequency and size information encoding are discussed. [ABSTRACT FROM AUTHOR]

Recognizing the emotions of faces in a crowd is crucial for understanding overall behavior and intention as well as for smooth and friendly social interactions. However, it is unclear whether the spatial frequency of faces affects the discrimination of crowd emotion. Although high- and low-spatial-frequency information for individual faces is processed by distinct neural channels, there is a lack of evidence on how this applies to crowd faces. Here, we used functional magnetic resonance imaging (fMRI) to investigate neural representations of crowd faces at different spatial frequencies. Thirty-three participants were asked to compare whether a test face was happy or more fearful than a crowd face that varied in high, low, and broad spatial frequencies. Our findings revealed that fearful faces with low spatial frequencies were easier to recognize in terms of accuracy (78.9%) and response time (927 ms). Brain regions, such as the fusiform gyrus, located in the ventral visual stream, were preferentially activated in high spatial frequency crowds, which, however, were the most difficult to recognize behaviorally (68.9%). Finally, the right inferior frontal gyrus was found to be better activated in the broad spatial frequency crowds. Our study suggests that people are more sensitive to fearful crowd faces with low spatial frequency and that high spatial frequency does not promote crowd face recognition. [ABSTRACT FROM AUTHOR]

Abstract Background Ultrasound is a powerful tool for diagnostic purposes and provides insight into both normal and pathologic tissue structure. Spatial frequency analysis (SFA) methods characterize musculoskeletal tissue organization from ultrasound images. Both sonographers in clinical imaging and researchers may alter a minimized range of ultrasound settings to optimize image quality, and it is important to know how these small adjustments of these settings affect SFA parameters. The purpose of this study was to investigate the effects of making small adjustments in a typical default ultrasound machine setting on extracted spatial frequency parameters (peak spatial frequency radius (PSFR), Mmax, Mmax%, and Sum) in the biceps femoris muscle. Methods Longitudinal B-mode images were collected from the biceps femoris muscle in 36 participants. The window depth, foci locations, and gain were systematically adjusted consistent with clinical imaging procedures for a total of 27 images per participant. Images were analyzed by identifying a region of interest (ROI) in the middle portion of the muscle belly in a template image and using a normalized two-dimensional cross-correlation technique between the template image and subsequent images. The ROI was analyzed in the frequency domain using conventional SFA methods. Separate linear mixed effects models were run for each extracted parameter. Results PSFR was affected by modifications in focus location only (p

Tissue engineering is a powerful tool with which to systematically identify the determinants of biological functions. Applied to the design and fabrication of biomimetic brains, tissue engineering serves to disentangle the complex anatomy of neural circuits and pathways by recapitulating structure-function relationships in simplified model systems. The complex neuroanatomy of the cerebral cortex, with its enigmatic columnar and stratified cytoarchitectonic organization, represents a major challenge toward isolating the minimal set of elements that are required to assemble neural tissues with cognitive functions. Whereas considerable efforts have highlighted important genetic and physical correlates of early cortical tissue patterning, no substantive attempt to identify the determinants of how the cortices acquire their relatively conserved, narrow range of numbered layers is evident in the literature. Similarly, it is not yet clear whether cortical columns and laminae are functionally relevant or epiphenomena of embryonic neurodevelopment. Here, we demonstrate that spatial frequencies (m−1) derived from the width-to-height ratios of cerebral cortical columns predict sinusoids with a narrow range of spatial cycles over the average cortical thickness. The resulting periodicities, denoted by theoretical wavenumbers, reflect the number of observed cortical layers among humans and across several other species as revealed by a comparative anatomy approach. We present a hypothesis that cortical columns and their periodic layers are emergent of the intrinsic spatial dimensions of neurons and their nested, self-similar aggregate structures including minicolumns. Finally, we discuss the implications of periodic tissue patterns in the context of neural tissue engineering.

IntroductionVisual perception is a complex process that involves the analysis of different spatial and temporal features of the visual environment. One critical aspect of this process is adaptation, which allows the visual system to adjust its sensitivity to specific features based on the context of the environment. Numerous theories highlight the significance of the visual scene and its spectral properties in perceptual and adaptation mechanisms. For example, size perception is known to be influenced by the spatial frequency content of the visual scene. Nonetheless, several inquiries still exist, including how specific spectral properties of the scene play a role in size perception and adaptation mechanisms.MethodsIn this study, we explore aftereffects on size perception following adaptation to a natural scene with a biased spectral amplitude distribution. Twenty participants had to manually estimate the horizontal size of a projected rectangle after adaptation to three visually biased conditions: vertical-biased, non-biased, and horizontal-biased. Size adaptation aftereffects were quantified by comparing the perceptual responses from the non-biased condition with the vertical- and horizontal-biased conditions.ResultsWe found size perception shifts which were contingent upon the specific orientation and spatial frequency distribution inherent in the amplitude spectra of the adaptation stimuli. Particularly, adaptation to vertical-biased produced a horizontal enlargement, while adaptation to horizontal-biased generated a decrease in the horizontal size perception of the rectangle. On average, size perception was modulated by 5–6%.DiscussionThese findings provide supporting evidence for the hypothesis that the neural mechanisms responsible for processing spatial frequency channels are involved in the encoding and perception of size information. The implications for neural mechanisms underlying spatial frequency and size information encoding are discussed.

Code-modulated visual evoked potentials (c-VEPs) are an innovative control signal utilized in brain-computer interfaces (BCIs) with promising performance. Prior studies on steady-state visual evoked potentials (SSVEPs) have indicated that the spatial frequency of checkerboard-like stimuli influences both performance and user experience. Spatial frequency refers to the dimensions of the individual squares comprising the visual stimulus, quantified in cycles (i.e., number of black-white squares pairs) per degree of visual angle. However, the specific effects of this parameter on c-VEP-based BCIs remain unexplored. Therefore, the objective of this study is to investigate the role of spatial frequency of checkerboard-like visual stimuli in a c-VEP-based BCI. Sixteen participants evaluated selection matrices with eight spatial frequencies: C001 (0 c/, 1×1 squares), C002 (0.15 c/1, 2×2 squares), C004 (0.3 c/, 4×4 squares), C008 (0.6 c/1, 8×8 squares), C016 (1.2 c/1, 16×16 squares), C032 (2.4 c/1, 32×32 squares), C064 (4.79 c/1, 64×64 squares), and C128 (9.58 c/1, 128×128 squares). These conditions were tested in an online spelling task, which consisted of 18 trials each conducted on a 3×3 command interface. In addition to accuracy and information transfer rate (ITR), subjectivemeasures regarding comfort, ocular irritation, and satisfaction were collected. Significant differences in performance and comfort were observed based on different stimulus spatial frequencies. Although all conditions achieved mean accuracy over 95% after 2.1 s of trial duration, C016 stood out in terms user experience. The proposed condition not only achieved a mean accuracy of 96.53% and 164.54 bits/min with a trial duration of 1.05s, but also was reported to be significantly more comfortable than the traditional C001 stimulus. Since both features are key for BCI development, higher spatial frequencies than the classical black-to-white stimulus might be more adequate for c-VEP systems. Hence, we assert that the spatial frequency should be carefully considered in the development of future applications for c-VEP-based BCIs. [ABSTRACT FROM AUTHOR]

Abstract Objective Method and material Result Conclusion \nSUMMARY Visual evoked potential recording has reported ambiguous results among migraineurs, thus the present study explored the association of check-size and reversal rates on the latency and amplitude of pattern reversal VEP among migraineurs.Monocular VEP responses for both eyes were recorded in 133 migraineurs and 111 controls. Checkerboard pattern with phase reversal frequency of 0.5, 1, 2 and 4 Hz and check-size of 16 × 16, 32 × 32, 64 × 64 and 128 × 128, i.e. spatial frequency of 0.475, 1.029, 2.056 and 4.112 cycle per degree (cpd) were used to record 100 responses each. Three-minutes gap was given after change of reversal frequency to a higher rate for next cycle of 4 check-size records.A linear increase in latencies was observed with decreasing check-size in both groups, but migraineurs had significantly higher latencies at a given reversal rate. Amplitudes A1 and A2 were higher among migraineurs and amplitude A2 showed an inverted ‘U’ shaped trend with maximum amplitude at 32 × 32 check size (1.029 cpd) in both groups, with an exaggerated response among migraineurs. Check-size 32 × 32 i.e. spatial frequency of 1.029 behaves differently than other larger or smaller check-sizes.Variable VEP response for different visual stimuli may be due to differential activation of respective retinocortical pathways and cortical areas. The highest amplitude at modest check-size suggests a contributory role of foveal-parafoveal fibres in migraineurs. Exaggerated physiological response to visual stimuli may be responsible for higher amplitudes and prolonged latencies among migraineurs.Exaggerated physiological VEP response as higher amplitudes and prolonged latencies, among migraineurs may be due to differential activation of respective retinocortical pathways and cortical areas. [ABSTRACT FROM AUTHOR]

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Medical image fusion analyzes multiple images obtained by the same/different medical modalities and constructs a robust image that is more useful for physicians by merging the complementary details contained in these images. Recently, pulse coupled neural network (PCNN) models constructed efficient image fusion algorithms, but at the expense of many parameters. Here, a novel adaptive Gaussian PCNN (AGPCNN) model is proposed that constitutes few parameters, adopts adaptive linking strength, and employs a Gaussian filter to effectively combine the surrounding neurons. In this paper, a new medical image fusion algorithm is introduced in the non-subsampled Shearlet transform domain that applies the novel AGPCNN to combine the high-pass sub-bands, whereas a new improved Roberts operator-based mechanism is incorporated to merge the low-pass sub-bands. The power of the proposed method is demonstrated using the experimental results of seven latest methods with twelve objective metrics on ten diverse medical image pairs that include the image pairs of an AIDS dementia complex patient. [ABSTRACT FROM AUTHOR]

Tissue engineering is a powerful tool with which to systematically identify the determinants of biological functions. Applied to the design and fabrication of biomimetic brains, tissue engineering serves to disentangle the complex anatomy of neural circuits and pathways by recapitulating structure-function relationships in simplified model systems. The complex neuroanatomy of the cerebral cortex, with its enigmatic columnar and stratified cytoarchitectonic organization, represents a major challenge toward isolating the minimal set of elements that are required to assemble neural tissues with cognitive functions. Whereas considerable efforts have highlighted important genetic and physical correlates of early cortical tissue patterning, no substantive attempt to identify the determinants of how the cortices acquire their relatively conserved, narrow range of numbered layers is evident in the literature. Similarly, it is not yet clear whether cortical columns and laminae are functionally relevant or epiphenomena of embryonic neurodevelopment. Here, we demonstrate that spatial frequencies (m−1) derived from the width-to-height ratios of cerebral cortical columns predict sinusoids with a narrow range of spatial cycles over the average cortical thickness. The resulting periodicities, denoted by theoretical wavenumbers, reflect the number of observed cortical layers among humans and across several other species as revealed by a comparative anatomy approach. We present a hypothesis that cortical columns and their periodic layers are emergent of the intrinsic spatial dimensions of neurons and their nested, self-similar aggregate structures including minicolumns. Finally, we discuss the implications of periodic tissue patterns in the context of neural tissue engineering. [ABSTRACT FROM AUTHOR]

Code-modulated visual evoked potentials (c-VEPs) are an innovative control signal utilized in brain-computer interfaces (BCIs) with promising performance. Prior studies on steady-state visual evoked potentials (SSVEPs) have indicated that the spatial frequency of checkerboard-like stimuli influences both performance and user experience. Spatial frequency refers to the dimensions of the individual squares comprising the visual stimulus, quantified in cycles (i.e., number of black-white squares pairs) per degree of visual angle. However, the specific effects of this parameter on c-VEP-based BCIs remain unexplored. Therefore, the objective of this study is to investigate the role of spatial frequency of checkerboard-like visual stimuli in a c-VEP-based BCI. Sixteen participants evaluated selection matrices with eight spatial frequencies: C001 (0 c/°, 1×1 squares), C002 (0.15 c/°, 2×2 squares), C004 (0.3 c/°, 4×4 squares), C008 (0.6 c/°, 8×8 squares), C016 (1.2 c/°, 16×16 squares), C032 (2.4 c/°, 32×32 squares), C064 (4.79 c/°, 64×64 squares), and C128 (9.58 c/°, 128×128 squares). These conditions were tested in an online spelling task, which consisted of 18 trials each conducted on a 3×3 command interface. In addition to accuracy and information transfer rate (ITR), subjective measures regarding comfort, ocular irritation, and satisfaction were collected. Significant differences in performance and comfort were observed based on different stimulus spatial frequencies. Although all conditions achieved mean accuracy over 95% after 2.1 s of trial duration, C016 stood out in terms user experience. The proposed condition not only achieved a mean accuracy of 96.53% and 164.54 bits/min with a trial duration of 1.05s, but also was reported to be significantly more comfortable than the traditional C001 stimulus. Since both features are key for BCI development, higher spatial frequencies than the classical black-to-white stimulus might be more adequate for c-VEP systems. Hence, we assert that the spatial frequency should be carefully considered in the development of future applications for c-VEP-based BCIs.

Background: Ultrasound is a powerful tool for diagnostic purposes and provides insight into both normal and pathologic tissue structure. Spatial frequency analysis (SFA) methods characterize musculoskeletal tissue organization from ultrasound images. Both sonographers in clinical imaging and researchers may alter a minimized range of ultrasound settings to optimize image quality, and it is important to know how these small adjustments of these settings affect SFA parameters. The purpose of this study was to investigate the effects of making small adjustments in a typical default ultrasound machine setting on extracted spatial frequency parameters (peak spatial frequency radius (PSFR), Mmax, Mmax%, and Sum) in the biceps femoris muscle. Methods: Longitudinal B-mode images were collected from the biceps femoris muscle in 36 participants. The window depth, foci locations, and gain were systematically adjusted consistent with clinical imaging procedures for a total of 27 images per participant. Images were analyzed by identifying a region of interest (ROI) in the middle portion of the muscle belly in a template image and using a normalized two-dimensional cross-correlation technique between the template image and subsequent images. The ROI was analyzed in the frequency domain using conventional SFA methods. Separate linear mixed effects models were run for each extracted parameter. Results: PSFR was affected by modifications in focus location only (p < 0.001) with differences noted between all locations. Mmax% was influenced by the interaction of gain and focus location (p < 0.001) but was also independently affected by increasing window depth (p < 0.001). Both Mmax and Sum parameters were sensitive to small changes in machine settings with the interaction of focus location and window depth (p < 0.001 for both parameters) as well as window depth and gain (p < 0.001 for both) influencing the extracted values. Conclusions: Frequently adjusted imaging settings influence some SFA statistics. PSFR and Mmax% appear to be most robust to small changes in image settings, making them best suited for comparison across individuals and between studies, which is appealing for the clinical utility of the SFA method. [ABSTRACT FROM AUTHOR]

Previous studies have shown that short-term monocular pattern deprivation can shift perceptual dominance in favor of the deprived eye. However, little is known about the effect of monocular pattern deprivation on contrast sensitivity (CS) and its corresponding mechanisms. Here, contrast sensitivity function (CSF) in the nondominant eye of normal subjects was evaluated before and after 150  min of monocular pattern deprivation. To obtain a CSF with high precision and efficiency before deprivation effect washout, a quick CSF (qCSF) method was used to assess CS over a wide range of spatial frequencies and at two external noise levels. We found that (1) monocular pattern deprivation effectively improved the CS of the deprived eye with larger effect on high spatial frequencies, (2) CS improvement only occurred when external noise was absent and its amount was spatial frequency dependent, and (3) a perceptual template model (PTM) revealed that decreased internal additive noise accounted for the mechanism of the monocular pattern derivation effect. These findings help us better understand the features of short-term monocular pattern deprivation and shed light on the treatment of amblyopia. [ABSTRACT FROM AUTHOR]

Potential cognitive and physiological alterations due to space environments have been investigated in long-term space flight and various microgravity-like conditions, for example, head-down tilt (HDT), confinement, isolation, and immobilization. However, little is known about the influence of simulated microgravity environments on visual function. Contrast sensitivity (CS), which indicates how much contrast a person requires to see a target, is a fundamental feature of human vision. Here, we investigated how the CS changed by 1-h −30° HDT and determined the corresponding mechanisms with a perceptual template model. A quick contrast sensitivity function procedure was used to assess the CS at ten spatial frequencies and three external noise levels. We found that (1) relative to the + 30° head-up tilt (HUT) position, 1-h −30° HDT significantly deteriorated the CS at intermediate frequencies when external noise was present; (2) CS loss was not detected in zero- or high-noise conditions; (3) HDT-induced CS loss was characterized by impaired perceptual template; and (4) self-reported questionnaires indicated that subjects felt less pleasure and more excitement, less comfort and more fatigued by screen light, less comfort in the area around the eye, and serious symptoms such as piercing pain, blur acid, strain, eye burning, and dizziness after HDT. These findings improve our understanding of the negative effects of simulated microgravity on visual function and elucidate the potential risks of astronauts during space flight. [ABSTRACT FROM AUTHOR]

Purpose: This study is to investigate the contrast sensitivity function (CSF) using the quick CSF (qCSF) test in Chinese adults with myopia. Methods: This case series study included 320 myopic eyes of 160 patients (mean age 27.75 ± 5.99 years) who underwent a qCSF test for acuity, area under log CSF (AULCSF), and mean contrast sensitivity (CS) at 1.0, 1.5, 3.0, 6.0, 12.0, and 18.0 cycle per degree (cpd). Spherical equivalent, corrected-distant visual acuity (CDVA), and pupil size were recorded. Results: The spherical equivalent, CDVA (LogMAR), spherical refraction, cylindrical refraction, and the scotopic pupil size of the included eyes were − 6.30 ± 2.27 D (− 14.25 to − 0.88 D), 0 ± 0.02, − 5.74 ± 2.18 D, − 1.11 ± 0.86 D, and 6.77 ± 0.73 mm, respectively. The AULCSF and CSF acuity were 1.01 ± 0.21 and 18.45 ± 5.39 cpd, respectively. The mean CS (log units) at six different spatial frequencies were 1.25 ± 0.14, 1.29 ± 0.14, 1.25 ± 0.14, 0.98 ± 0.26, 0.45 ± 0.28, and 0.13 ± 0.17, respectively. A mixed effect model showed significant correlations between age and acuity, AULCSF, and CSF at 1.0, 12.0, and 18.0 cpd. Interocular CSF differences were correlated with the interocular difference of spherical equivalent, spherical refraction (at 1.0 cpd, 1.5 cpd), and cylindrical refraction (at 12.0 cpd, 18.0 cpd). The lower cylindrical refraction eye had higher CSF compared with the higher cylindrical refraction eye (0.48 ± 0.29 vs. 0.42 ± 0.27 at 12.0 cpd and 0.15 ± 0.19 vs. 0.12 ± 0.15 at 18.0 cpd). Conclusions: The age-related decrease in contrast sensitivity is at low and high spatial frequencies. Higher-degree myopia may show a decrease in CSF acuity. Low astigmatism was noted to affect the contrast sensitivity significantly. [ABSTRACT FROM AUTHOR]

PurposeTo examine the hypothesis that the spatial frequency spectra of urban and indoor environments differ from the natural environment in ways that may promote the development of myopia.MethodsA total of 814 images were analyzed from three datasets; University of California Berkeley (UCB), University of Texas (UT), and Botswana (UPenn). Images were processed in Matlab (Mathworks Inc) to map the camera color characteristics to human cone sensitivities. From the photopic luminance images generated, two-dimensional spatial frequency (SF) spectra were calculated and converted to one-dimensional spectra by rotational averaging. The spatial filtering profile of a 0.4 Bangerter foil, which has been shown to induce myopia experimentally, was also determined.ResultsThe SF slope for natural scenes followed the recognized 1/fα relationship with mean slopes of -1.08, -0.90, and -1.04 for the UCB, UT and UPenn image sets, respectively. Indoor scenes had a significantly steeper slope (-1.48, UCB; -1.52, UT; P < 0.0001). Urban environments showed an intermediate slope (-1.29, UCB; -1.22, UT) that was significantly different from the slopes derived from the natural scenes (P < 0.0001). The change in SF content between natural outdoor scenes and indoors was comparable to that induced by a 0.4 Bangerter foil, which reduced the SF slope of a natural scene from -0.88 to -1.47.ConclusionsCompared to natural outdoor images, man-made outdoor and indoor environments have spatial frequency characteristics similar to those known to induce form-deprivation myopia in animal models. The spatial properties of the man-made environment may be one of the missing drivers of the human myopia epidemic.

Background and Aim: Objective measurement of visual acuity using VEP is high valued in patients with low levels of cooperation. Therefore, this study aimed to investigate the effect of spatial frequency on VEP components in visual acuity using Sweep VEP. Material and Methods: In this cross-sectional study 63 medical students with an age of 22.81 ± 3.93 were selected. After a completed eye examination, refractive error was determined, and best-corrected visual acuity as subjective was recorded by the Freiburg Acuity contrast test. Sweep VEP using the Roland electrophysiology system was recorded for various spatial frequencies from 2 to 37.5 cycles per degree. VEP components were the latencies of N1, P1, N135, and the amplitude of VEP. Results: Repeated measures of the ANOVA test showed that the effect of spatial frequency on latencies and amplitude of VEP was significant (P

Abstract Background Studies have shown that short-term monocular deprivation induces a shift in sensory eye dominance in favor of the deprived eye. Yet, how short-term monocular deprivation modulates sensory eye dominance across spatial frequency is not clear. To address this issue, we conducted a study to investigate the dependence of short-term monocular deprivation effect on test spatial frequency. Methods Ten healthy young adults (age: 24.7 ± 1.7 years, four males) with normal vision participated. We deprived their dominant eye with a translucent patch for 2.5 h. The interocular contrast ratio (dominant eye/non-dominant eye, i.e., the balance point [BP]), which indicates the contribution that the two eyes make to binocular combination, was measured using a binocular orientation combination task. We assessed if BPs at 0.5, 4 or 6 cycles/degree (c/d) change as a result of monocular deprivation. Different test spatial frequency conditions were conducted on three separate days in a random fashion. Results We compared the BPs at 0.5, 4 and 6 c/d before and after monocular deprivation. The BPs were found to be significantly affected by deprivation, where sensory eye dominance shift to the deprived eye (F1.86, 16.76 = 33.09, P

Previous studies have found that literacy acquisition modulates configural face processing (i.e., holistic and second-order configural processing). However, it remains unclear how literacy acquisition impacts the configural processing indexed by the inversion effect of normal or filtered faces. We asked Chinese illiterate and literate adults to judge whether two sequentially-presented stimuli, including faces, houses (experiment 1), and high- or low-pass filtered faces (experiment 2) were identical. Literate adults outperformed illiterate controls in the upright face and house conditions (experiment 1) and the upright high- and low-pass filtered conditions (experiment 2) but not in the inverted conditions. Notably, the size of an inversion effect (i.e., subtracting inverted accuracy from upright accuracy) was greater among literate adults than that among illiterate adults in both experiments. These findings support that literacy acquisition promotes configural face processing. [ABSTRACT FROM AUTHOR]

The improvements due to small incision lenticule extraction (SMILE) in vision, e.g., in spherical equivalent (SE) and visual acuity (VA), has been widely recognized. However, the contrast sensitivity (CS) change after SMILE was not certain. Here, we investigated the effect of SMILE on CS before, 1 day after and 7 days after surgery and then clarified the corresponding mechanism by using a perceptual template model (PTM). In addition, the relationship among SE, VA, and CS was discussed. The quick contrast sensitivity function (qCSF) was applied to measure CS with high precision and accuracy. We found that CS was significantly improved 1 day after SMILE and was also increased 7 days after the surgery, CS improvements were dependent on spatial frequency and external noise, the increase in CS was due to the decreased internal additive noise and an enhanced perceptual template, and (4) Greater SE improvements predicted better VA improvements 1 day after SMILE, and a positive correlation between SE improvements and AULCSF improvements 7 days after SMILE was observed. These findings help us better understand the effect of SMILE and provide effective indicators for future visual research. [ABSTRACT FROM AUTHOR]