Role Of Spatial Frequency Research Articles

The role of spatial frequencies for facial pain categorization

Studies on low-level visual information underlying pain categorization have led to inconsistent findings. Some show an advantage for low spatial frequency information (SFs) and others a preponderance of mid SFs. This study aims to clarify this gap in knowledge since these results have different theoretical and practical implications, such as how far away an observer can be in order to categorize pain. This study addresses this question by using two complementary methods: a data-driven method without a priori expectations about the most useful SFs for pain recognition and a more ecological method that simulates the distance of stimuli presentation. We reveal a broad range of important SFs for pain recognition starting from low to relatively high SFs and showed that performance is optimal in a short to medium distance (1.2–4.8 m) but declines significantly when mid SFs are no longer available. This study reconciles previous results that show an advantage of LSFs over HSFs when using arbitrary cutoffs, but above all reveal the prominent role of mid-SFs for pain recognition across two complementary experimental tasks.

IMI Accommodation and Binocular Vision in Myopia Development and Progression.

The role of accommodation in myopia development and progression has been debated for decades. More recently, the understanding of the mechanisms involved in accommodation and the consequent alterations in ocular parameters has expanded. This International Myopia Institute white paper reviews the variations in ocular parameters that occur with accommodation and the mechanisms involved in accommodation and myopia development and progression. Convergence is synergistically linked with accommodation and the impact of this on myopia has also been critiqued. Specific topics reviewed included accommodation and myopia, role of spatial frequency, and contrast of the task of objects in the near environment, color cues to accommodation, lag of accommodation, accommodative-convergence ratio, and near phoria status. Aspects of retinal blur from the lag of accommodation, the impact of spatial frequency at near and a short working distance may all be implicated in myopia development and progression. The response of the ciliary body and its links with changes in the choroid remain to be explored. Further research is critical to understanding the factors underlying accommodative and binocular mechanisms for myopia development and its progression and to guide recommendations for targeted interventions to slow myopia progression.

The Peripheral View Melts Facial Emotion into a Blur: Investigating the Role of Spatial Frequency in Younger and Older Adults’ Peripheral Emotion Detection

The Peripheral View Melts Facial Emotion into a Blur: Investigating the Role of Spatial Frequency in Younger and Older Adults’ Peripheral Emotion Detection

The role of spatial frequency in emotional face classification.

Previous studies with emotional face stimuli have revealed that our ability to identify different emotional states is dependent on the faces' spatial frequency content. However, these studies typically only tested a limited number of emotional states. In the present study, we measured the consistency with which 24 different emotional states are classified when the faces are unfiltered, high-, or low-pass filtered, using a novel rating method that simultaneously measures perceived arousal (high to low) and valence (pleasant to unpleasant). The data reveal that consistent ratings are made for every emotional state independent of spatial frequency content. We conclude that emotional faces possess both high- and low-frequency information that can be relied on to facilitate classification.

Perceptual integration of faces and voices depends on the interaction of emotional content and spatial frequency

The role of spatial frequencies (SF) is highly debated in emotion perception, but previous work suggests the importance of low SFs for detecting emotion in faces. Furthermore, emotion perception essentially relies on the rapid integration of multimodal information from faces and voices. We used EEG to test the functional relevance of SFs in the integration of emotional and non-emotional audiovisual stimuli. While viewing dynamic face-voice pairs, participants were asked to identify auditory interjections, and the electroencephalogram (EEG) was recorded. Audiovisual integration was measured as auditory facilitation, indexed by the extent of the auditory N1 amplitude suppression in audiovisual compared to an auditory only condition. We found an interaction of SF filtering and emotion in the auditory response suppression. For neutral faces, larger N1 suppression ensued in the unfiltered and high SF conditions as compared to the low SF condition. Angry face perception led to a larger N1 suppression in the low SF condition. While the results for the neural faces indicate that perceptual quality in terms of SF content plays a major role in audiovisual integration, the results for angry faces suggest that early multisensory integration of emotional information favors low SF neural processing pathways, overruling the predictive value of the visual signal per se.

The role of spatial frequency in expert object recognition.

Novices recognize objects at the basic-category level (e.g., dog, chair, and bird) at which identification is based on the global form of the objects (Rosch, Mervis, Gray, Johnson, & Boyes-Braem, 1976). In contrast, experts recognize objects within their domain of expertise at the subordinate level (e.g., Sparrow or Finch) for which the internal object information may play an important role in identification (Tanaka & Taylor, 1991). To investigate whether expert recognition relies on internal object information, we band-pass filtered bird images over a range of spatial frequencies (SF) and then masked the filtered image to preserve its global form. In Experiment 1, bird experts categorized common birds at the family level (e.g., Robin or Sparrow) more quickly and more accurately than novices. Both experts and novices were more accurate when bird images contained the internal information represented by a middle range of SFs, and this finding was characterized by a quadratic function in which accuracy decreased toward each end of the SF spectrum. However, the experts, but not the novices, showed a similar quadratic relationship between response times and SF range. In Experiment 2, experts categorized Warblers and Finches at the more specific, species level (e.g., Wilson's Warbler or House Finch). Recognition was again fastest and most accurate for images filtered in the middle range of SFs. Collectively, these results indicate that a midrange of SFs contain crucial information for subordinate recognition, and that extensive perceptual experience can influence the efficiency with which this information is utilized. (PsycINFO Database Record

Supplemental Material for The Role of Spatial Frequency in Expert Object Recognition

Supplemental Material for The Role of Spatial Frequency in Expert Object Recognition

Multiple forms of contour grouping deficits in schizophrenia: What is the role of spatial frequency?

Schizophrenia patients poorly perceive Kanizsa figures and integrate co-aligned contour elements (Gabors). They also poorly process low spatial frequencies (SFs), which presumably reflects dysfunction along the dorsal pathway. Can contour grouping deficits be explained in terms of the spatial frequency content of the display elements? To address the question, we tested patients and matched controls on three contour grouping paradigms in which the SF composition was modulated. In the Kanizsa task, subjects discriminated quartets of sectored circles (“pac-men”) that either formed or did not form Kanizsa shapes (illusory and fragmented conditions, respectively). In contour integration, subjects identified the screen quadrant thought to contain a closed chain of co-circular Gabors. In collinear facilitation, subjects attempted to detect a central low-contrast element flanked by collinear or orthogonal high-contrast elements, and facilitation corresponded to the amount by which collinear flankers reduced contrast thresholds. We varied SF by modifying the element features in the Kanizsa task and by scaling the entire stimulus display in the remaining tasks (SFs ranging from 4 to 12cycles/deg). Irrespective of SF, patients were worse at discriminating illusory, but not fragmented shapes. Contrary to our hypothesis, collinear facilitation and contour integration were abnormal in the clinical group only for the higher SF (>=10c/deg). Grouping performance correlated with clinical variables, such as conceptual disorganization, general symptoms, and levels of functioning. In schizophrenia, three forms of contour grouping impairments prominently arise and cannot be attributed to poor low SF processing. Neurobiological and clinical implications are discussed.

The role of spatial frequencies in expert object recognition

The role of spatial frequencies in expert object recognition

Lateral interactions in schizophrenia: What is the role of spatial frequency?

Lateral interactions in schizophrenia: What is the role of spatial frequency?

Kanizsa shape discrimination and contour integration deficits in schizophrenia: What is the role of spatial frequency?

Kanizsa shape discrimination and contour integration deficits in schizophrenia: What is the role of spatial frequency?

Processing of Fear and Anger Facial Expressions: The Role of Spatial Frequency

Spatial frequency (SF) components encode a portion of the affective value expressed in face images. The aim of this study was to estimate the relative weight of specific frequency spectrum bandwidth on the discrimination of anger and fear facial expressions. The general paradigm was a classification of the expression of faces morphed at varying proportions between anger and fear images in which SF adaptation and SF subtraction are expected to shift classification of facial emotion. A series of three experiments was conducted. In Experiment 1 subjects classified morphed face images that were unfiltered or filtered to remove either low (<8 cycles/face), middle (12–28 cycles/face), or high (>32 cycles/face) SF components. In Experiment 2 subjects were adapted to unfiltered or filtered prototypical (non-morphed) fear face images and subsequently classified morphed face images. In Experiment 3 subjects were adapted to unfiltered or filtered prototypical fear face images with the phase component randomized before classifying morphed face images. Removing mid frequency components from the target images shifted classification toward fear. The same shift was observed under adaptation condition to unfiltered and low- and middle-range filtered fear images. However, when the phase spectrum of the same adaptation stimuli was randomized, no adaptation effect was observed. These results suggest that medium SF components support the perception of fear more than anger at both low and high level of processing. They also suggest that the effect at high-level processing stage is related more to high-level featural and/or configural information than to the low-level frequency spectrum.

Modulation of the Object/Background Interaction by Spatial Frequency

With regard to the relationship between object and background perception in the natural scene images, functional isolation hypothesis and interactive hypothesis were proposed. Based on previous studies, the present study investigated the role of spatial frequency in the relationship between object and background perception in the natural scene images. In three experiments, participants reported the object, background, or both after seeing each picture for 500 ms followed by a mask. The authors found that (a) backgrounds were identified more accurately when they contained a consistent rather than an inconsistent object, independently of spatial frequency; (b) objects were identified more accurately in a consistent than an inconsistent background under the condition of low spatial frequencies but not high spatial frequencies; (c) spatial frequency modulation remained when both objects and backgrounds were reported simultaneously. The authors conclude that object/background interaction is partially dependent on spatial frequency.

The role of spatial frequencies in the recognition and naming of natural and man-made objects

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The role of spatial frequency in ultra-rapid scene categorization

The role of spatial frequency in ultra-rapid scene categorization

The role of spatial frequencies in face-selective areas: Task-dependent effects

The role of spatial frequencies in face-selective areas: Task-dependent effects

The role of spatial frequency in color induction

Color induction was measured for test and inducing chromaticities presented in spatial square-wave alternation, with spatial frequencies of 0.7, 4.0, 6.0 and 9.0 cpd. Observers matched the test chromaticities to a rectangular matching field using haploscopic presentation. Data were collected and analyzed within the framework of a cone chromaticity space, allowing analysis of spatial frequency effects on post-receptoral spectral opponent pathways. Assimilation, a shift of chromaticity toward the inducing chromaticity, was found at the highest spatial frequency (9.0 cpd). Contrast, a shift of chromaticity away from the inducing chromaticity, occurred at the lowest spatial frequency (0.7 cpd). The spatial frequency at the transition point from assimilation to contrast was near 4 cpd, independent of the cone axis. Assimilation was unaffected by the presence of a neutral surround and could be described by a spread light model. Contrast was reduced in the presence of a neutral surround. The data suggested that retinal contrast signals are important determinants in the perception of chromatic contrast.

The role of spatial frequency in cued shifts of attention between global and local forms.

It has been suggested that shifts of attention between global and local forms might be based on selection between, or differential activation of, low- and high-spatial-frequency channels. In the present study, pretrial cues indicated which level (global or local) was likely to contain the target on each trial. There was a response time (RT) advantage for validly cued trials and an RT cost for invalidly cued trials relative to a neutral cue baseline. This cuing effect was the same for broadband stimuli and for contrast-balanced stimuli in which low spatial frequencies were eliminated. Thus, cued attentional shifts between global and local forms occur even when selection cannot be based on spatial frequency.

The role of spatial frequency in the processing of hierarchically organized stimuli.

Can spatial frequency differences between local and global forms account for differences in the way different levels of structure are analyzed? We examined this question by having subjects identify local or global forms of hierarchical stimuli that had been contrast balanced. Contrast balancing eliminates low spatial frequencies, so that both local and global forms must be identified on the basis of high spatial frequency information. Response times (RTs) to global (but not local) forms were slowed for contrast-balanced stimuli, suggesting that low spatial frequencies mediate the global RT advantage typically found. In contrast, interference between local and global forms was little affected by contrast balancing or by shifts of attention between local and global forms, suggesting that it does not result from inhibitory interactions between spatial frequency channels or from temporal precedence of low versus high spatial frequency information. Finally, shifts of attention between local and global forms were also little affected by contrast balancing, suggesting that they were not based on spatial frequency.

“Weber's law” for position: the role of spatial frequency and contrast

We used Gabor bars to measure the effects of spatial bandwidth, spatial scale, contrast and separation on three-line spatial interval discrimination (bisection). In the first experiment, we used stimuli that were well above threshold. Our results show that at all spatial scales, spatial interval discrimination (three-line bisection) thresholds are proportional to the separation of the Gabor patches (i.e. Weber's law) when the separation exceeds approximately 2.5 times the standard deviation (σ) of the Gaussian envelope. The optimal threshold occurs when the separation is approx. 2–2.5σ, and for separations larger than the optimal, bisection thresholds are equal to a more or less constant Weber fraction ( Δs/s) of approx. 0.02–0.04. These results are consistent with a number of previous studies. In the second experiment, we examined the effect of contrast. Our results show an interaction between separation and stimulus visibility. Reducing the stimulus contrast has a marked effect on spatial interval thresholds at small separations (e.g. separations less than about 3σ), and much less effect at larger separations. Thus, the Weber's law relationship appears to depend on the visibility of the stimuli, but does not depend on the spatial frequency or bandwidth of the stimuli. These results can be predicted by an ideal observer model of spatial interval discrimination.