Detection of Chromatic and Achromatic Patterns at Threshold: RT Evidence of Sustained and Transient Mechanisms

Perception ◽  
1997 ◽  
Vol 26 (1_suppl) ◽  
pp. 307-307 ◽  
Author(s):  
N R A Parry ◽  
I J Murray
Keyword(s):  
Probability Theory ◽  
Reaction Time ◽  
Spatial Frequency ◽  
Stimulus Presentation ◽  
Transient Detection ◽  
Physiological Mechanisms ◽  
Spatial Frequencies ◽  
Detection Mechanisms ◽  
Chromatic Processing

In primates, relatively slow sustained-like physiological mechanisms mediate chromatic processing and rapid transient-like mechanisms mediate low-spatial-frequency achromatic processing. Our objective was to investigate the role of transient and sustained mechanisms in the detection of chromatic and achromatic gratings with the use of a reaction time (RT) paradigm. Following Tolhurst (1975 Vision Research15 1143 – 1149), we constructed RT histograms using near-threshold grating stimuli. Tolhurst showed that, for low-spatial-frequency achromatic patterns, the RT histograms cluster around the onset and the offset of the pattern, indicating transient detection. His onset and offset distributions were consistent with probability theory. With high spatial frequencies, RTs are evenly distributed over the duration of the stimulus presentation, showing the operation of a sustained mechanism. When we used low-spatial-frequency (0.22 cycle deg−1) isoluminant red - green gratings, the RT histograms were unimodal, revealing detection mechanisms with predominantly sustained characteristics, as expected. RT histograms obtained with low-spatial-frequency achromatic stimuli in our study were bimodal. However, when we compared small and large fields, the shape of the RT histogram varied in a manner which could not be accounted for by a simple probabilistic model. This can be rationalised if onsets and offsets are not equally detectable.

The Role of Spatial-Frequency Channels in the Perception of Local and Global Structure

Perception ◽  
1986 ◽  
Vol 15 (3) ◽  
pp. 259-273 ◽  
Author(s):  
Gordon L Shulman ◽  
Marc A Sullivan ◽  
Ken Gish ◽  
William J Sakoda
Keyword(s):  
Reaction Time ◽  
Spatial Frequency ◽  
Low Frequency ◽  
Global Structure ◽  
Global Processing ◽  
Low Frequencies ◽  
Subsequent Performance ◽  
Spatial Frequencies

Adaptation and reaction-time techniques were used to examine the role of different spatial-frequency channels in the perception of local and global structure. Subjects were shown figures consisting of a large C composed of smaller Cs and asked to identify the orientation of either the global C or its local elements. Prior to performing the task subjects were adapted to different spatial frequencies and the effect on subsequent performance was assessed. Two main results were found. First, the adapting frequency that most affected the global task was often lower than that most affecting the local task, suggesting that high and low frequencies independently code the structure of an image. Second, reaction time to global figures was often faster than to local figures at all levels of detectability, again suggesting a role of low-frequency channels in global processing.

scholarly journals The Role of Spatial Frequencies for Facial Pain Categorization

2021 ◽  
Author(s):  
Isabelle Charbonneau ◽  
Joël Guérette ◽  
Stéphanie Cormier ◽  
Caroline Blais ◽  
Guillaume Lalonde-Beaudoin ◽  
...  
Keyword(s):  
Spatial Frequency ◽  
Visual Information ◽  
Facial Pain ◽  
A Priori ◽  
Data Driven ◽  
Low Level ◽  
Spatial Frequencies ◽  
Pain Recognition ◽  
Practical Implications

Abstract Studies on low-level visual information underlying pain categorization have led to inconsistent findings. Some are showing 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 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 SF for pain recognition starting from low to relatively high SFs and showed that performance is optimal in a short to medium distance (1.2 to 4.8 meters) 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 experimental tasks.

The Role of High Spatial Frequencies in Face Perception

Perception ◽  
1983 ◽  
Vol 12 (2) ◽  
pp. 195-201 ◽  
Author(s):  
Adriana Fiorentini ◽  
Lamberto Maffei ◽  
Giulio Sandini
Keyword(s):  
Spatial Frequency ◽  
Face Perception ◽  
Energy Content ◽  
High Spatial Frequency ◽  
Face Width ◽  
Spatial Frequencies ◽  
Low Pass ◽  
High Pass ◽  
Spatial Frequency Domain

The relevance of low and high spatial-frequency information for the recognition of photographs of faces has been investigated by testing recognition of faces that have been either low-pass (LP) or high-pass (HP) filtered in the spatial-frequency domain. The highest resolvable spatial frequency was set at 15 cycles per face width (cycles fw−1). Recognition was much less accurate for images that contained only the low spatial frequencies (up to 5 cycles fw−1) than for images that contained only spatial frequencies higher than 5 cycles fw−1. For faces HP filtered above 8 cycles fw−1, recognition was almost as accurate as for faces LP filtered below 8 cycles fw−1, although the energy content of the latter greatly exceeded that of the former. These findings show that information conveyed by the higher spatial frequencies is not redundant. Rather, it is sufficient by itself to ensure recognition.

Visual reaction time of cats to different spatial frequencies

1990 ◽  
Vol 5 (6) ◽  
pp. 557-564 ◽  
Author(s):  
Bonnie E. Aiken ◽  
Michael S. Loop
Keyword(s):  
Reaction Time ◽  
Spatial Frequency ◽  
Reaction Times ◽  
Sine Wave ◽  
Contrast Threshold ◽  
Visual Reaction Time ◽  
Spatial Frequencies ◽  
Visual Reaction ◽  
X Cells ◽  
Y Cells

AbstractIf physiological mechanisms similar to cat Y and X cells explain faster detection of low spatial frequencies by humans, then cats should show the same effect. We have tested this prediction by determining the visual reaction time of cats over a range of spatial frequencies and contrasts by training them to respond quickly when a vertical sine-wave grating was presented. At 50% contrast, the cat's visual reaction time increased monotonically from 0.25–2.0 cpd (cycle/deg). At every spatial frequency tested, the cat's reaction time increased monotonically as contrast decreased. By determining contrast threshold (70% detection) at each spatial frequency, it was possible to determine reaction times for different spatial frequencies at equal physical contrasts and equal “threshold equivalent” contrasts. Some of the cat's faster detection of low spatial frequencies was due to sensitivity differences and some was not. To determine if faster detection of low spatial frequencies was based upon Y cells, we took advantage of the fact that Y cells show a strong peripheral effect while X cells do not. Low and high spatial frequencies were detected in the presence of a flickering (7 Hz) or steady (70 Hz) surround. Surround frequency had no effect upon reaction times to 2.0 cpd but the flickering surround increased reaction times to 0.25 cpd. These results indicate that, in cats, rapid detection of low spatial frequencies is by Y cells and slower detection of high spatial frequencies is by X cells.

scholarly journals Implicit anticipation of probabilistic regularities: Larger CNV emerges for unpredictable events

2020 ◽  
Author(s):  
Andrea Kóbor ◽  
Zsófia Kardos ◽  
Kata Horváth ◽  
Karolina Janacsek ◽  
Ádám Takács ◽  
...  
Keyword(s):  
Reaction Time ◽  
Contingent Negative Variation ◽  
Target Stimulus ◽  
Stimulus Presentation ◽  
Building Blocks ◽  
Response Preparation ◽  
Attentional Resources ◽  
Probability Structure ◽  
Predictive Processes

AbstractAnticipation of upcoming events plays a crucial role in automatic behaviors. It is, however, still unclear whether the event-related brain potential (ERP) markers of anticipation could track the implicit acquisition of probabilistic regularities that can be considered as building blocks of automatic behaviors. Therefore, in a four-choice reaction time (RT) task performed by young adults (N = 36), the contingent negative variation (CNV) as an ERP marker of anticipation was measured from the onset of a cue stimulus until the presentation of a target stimulus. Due to the probability structure of the task, target stimuli were either predictable or unpredictable, but this was unknown to participants. The cue did not contain predictive information on the upcoming target. Results showed that the CNV amplitude during response preparation was larger before the unpredictable than before the predictable target stimuli. In addition, although RTs increased, the P3 amplitude decreased for the unpredictable as compared with the predictable target stimuli, possibly due to the stronger response preparation that preceded stimulus presentation. These results suggest that enhanced attentional resources are allocated to the implicit anticipation and processing of unpredictable events. This possibly results from the formation of internal models on the probabilistic regularities of the stimulus stream, favoring predictable events. Overall, we provide ERP evidence for the implicit anticipation of probabilistic regularities, confirming the role of predictive processes in learning and memory.

scholarly journals The role of spatial frequencies for facial pain categorization

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Isabelle Charbonneau ◽  
Joël Guérette ◽  
Stéphanie Cormier ◽  
Caroline Blais ◽  
Guillaume Lalonde-Beaudoin ◽  
...  
Keyword(s):  
Spatial Frequency ◽  
Visual Information ◽  
Facial Pain ◽  
A Priori ◽  
Data Driven ◽  
Low Level ◽  
Spatial Frequencies ◽  
Pain Recognition ◽  
Practical Implications

AbstractStudies 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.

Chemical Availability of Bromide Dictates CsPbBr3 Nanocrystal Growth

2019 ◽  
Author(s):  
Je-Ruei Wen ◽  
Benjamin Roman ◽  
Freddy Rodriguez Ortiz ◽  
Noel Mireles Villegas ◽  
Nicholas Porcellino ◽  
...  
Keyword(s):  
Reaction Time ◽  
Growth Mechanism ◽  
Chemical Control ◽  
Critical Role ◽  
Phase Evolution ◽  
Detailed Understanding ◽  
Semiconductor Nanocrystal ◽  
Nanocrystal Growth ◽  
Chemical Availability

Lack of detailed understanding of the growth mechanism of CsPbBr3 nanocrystals has hindered sophisticated morphological and chemical control of this important emerging optoelectronic material. Here, we have elucidated the growth mechanism by slowing the reaction kinetics. When 1-bromohexane is used as an alternative halide source, bromide is slowly released into the reaction mixture, extending the reaction time from ~3 seconds to greater than 20 minutes. This enables us to monitor the phase evolution of products over the course of reaction, revealing that CsBr is the initial species formed, followed by Cs4PbBr6, and finally CsPbBr3. Further, formation of monodisperse CsBr nanocrystals is demonstrated in a bromide-deficient and lead-abundant solution. The CsBr can only be transformed into CsPbBr3 nanocubes if additional bromide is added. Our results indicate a fundamentally different growth mechanism for CsPbBr3 in comparison with more established semiconductor nanocrystal systems and reveal the critical role of the chemical availability of bromide for the growth reactions.<br>

The Non-Causal Character of Renormalization Group Explanations

2018 ◽  
Author(s):  
Margaret Morrison
Keyword(s):  
Probability Theory ◽  
Renormalization Group ◽  
Dynamical Systems ◽  
Recent Literature ◽  
Mathematical Explanation ◽  
Causal Status ◽  
Physical Information ◽  
The Relationship ◽  
Structural Aspects

After reviewing some of the recent literature on non-causal and mathematical explanation, this chapter develops an argument as to why renormalization group (RG) methods should be seen as providing non-causal, yet physical, information about certain kinds of systems/phenomena. The argument centres on the structural character of RG explanations and the relationship between RG and probability theory. These features are crucial for the claim that the non-causal status of RG explanations involves something different from simply ignoring or “averaging over” microphysical details—the kind of explanations common to statistical mechanics. The chapter concludes with a discussion of the role of RG in treating dynamical systems and how that role exemplifies the structural aspects of RG explanations which in turn exemplifies the non-causal features.

scholarly journals Role of miRNAs in Normal Endometrium and in Endometrial Disorders: Comprehensive Review

2021 ◽  
Vol 10 (16) ◽  
pp. 3457
Author(s):  
Kamila Kolanska ◽  
Sofiane Bendifallah ◽  
Geoffroy Canlorbe ◽  
Arsène Mekinian ◽  
Cyril Touboul ◽  
...  
Keyword(s):  
Endometrial Cancer ◽  
Mirna Expression ◽  
Expression Patterns ◽  
Mirna Regulation ◽  
Rigorous Analysis ◽  
Sexual Hormones ◽  
Physiological Mechanisms ◽  
Normal Endometrium ◽  
Gynecological Disorders

The molecular responses to hormonal stimuli in the endometrium are modulated at the transcriptional and post-transcriptional stages. Any imbalance in cellular and molecular endometrial homeostasis may lead to gynecological disorders. MicroRNAs (miRNAs) are involved in a wide variety of physiological mechanisms and their expression patterns in the endometrium are currently attracting a lot of interest. miRNA regulation could be hormone dependent. Conversely, miRNAs could regulate the action of sexual hormones. Modifications to miRNA expression in pathological situations could either be a cause or a result of the existing pathology. The complexity of miRNA actions and the diversity of signaling pathways controlled by numerous miRNAs require rigorous analysis and findings need to be interpreted with caution. Alteration of miRNA expression in women with endometriosis has been reported. Thus, a potential diagnostic test supported by a specific miRNA signature could contribute to early diagnosis and a change in the therapeutic paradigm. Similarly, specific miRNA profile signatures are expected for RIF and endometrial cancer, with direct implications for associated therapies for RIF and adjuvant therapies for endometrial cancer. Advances in targeted therapies based on the regulation of miRNA expression are under evaluation.

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