Effect of shift invariance and stationarity assumptions on simple detection tasks: spatial and spatial frequency domains

2001 ◽  
Author(s):  
Robert M. Gagne ◽  
Kyle J. Myers ◽  
Philip W. Quinn
Keyword(s):  
Spatial Frequency ◽  
Frequency Domains ◽  
Simple Detection ◽  
Shift Invariance

Role of the color-opponent and broad-band channels in vision

1990 ◽  
Vol 5 (04) ◽  
pp. 321-346 ◽  
Author(s):  
Peter H. Schiller ◽  
Nikos K. Logothetis ◽  
Eliot R. Charles
Keyword(s):  
Spatial Frequency ◽  
Temporal Frequency ◽  
Broad Band ◽  
High Spatial Frequency ◽  
Brightness Perception ◽  
Rods And Cones ◽  
Form Vision ◽  
Temporal Domain ◽  
Frequency Domains

AbstractThe functions of the primate color-opponent and broad-band channels were assessed by examining the visual capacities of rhesus monkeys following selective lesions of parvocellular and magnocellular lateral geniculate nucleus, which respectively relay these two channels to the cortex. Parvocellular lesions impaired color vision, high spatial-frequency form vision, and fine stereopsis. Magnocellular lesions impaired high temporal- frequency flicker and motion perception but produced no deficits in stereopsis. Low spatial-frequency form vision, stereopsis, and brightness perception were unaffected by either lesion. Much as the rods and cones of the retina can be thought of as extending the range of vision in the intensity domain, we propose that the color-opponent channel extends visual capacities in the wavelength and spatial-frequency domains whereas the broad-band channel extends them in the temporal domain.

scholarly journals Joint Entropy for Space and Spatial Frequency Domains Estimated from Psychometric Functions of Achromatic Discrimination

PLoS ONE ◽  
2014 ◽  
Vol 9 (1) ◽  
pp. e86579 ◽  
Author(s):  
Vladímir de Aquino Silveira ◽  
Givago da Silva Souza ◽  
Bruno Duarte Gomes ◽  
Anderson Raiol Rodrigues ◽  
Luiz Carlos de Lima Silveira
Keyword(s):  
Spatial Frequency ◽  
Joint Entropy ◽  
Frequency Domains

scholarly journals A Framework of Combining Short-Term Spatial/Frequency Feature Extraction and Long-Term IndRNN for Activity Recognition

Sensors ◽  
2020 ◽  
Vol 20 (23) ◽  
pp. 6984
Author(s):  
Beidi Zhao ◽  
Shuai Li ◽  
Yanbo Gao ◽  
Chuankun Li ◽  
Wanqing Li
Keyword(s):  
Feature Extraction ◽  
Spatial Frequency ◽  
Activity Recognition ◽  
Sensor Data ◽  
Short Term ◽  
Temporal Features ◽  
Frequency Domains ◽  
Smartphone Sensors ◽  
Frequency Feature

Smartphone-sensors-based human activity recognition is attracting increasing interest due to the popularization of smartphones. It is a difficult long-range temporal recognition problem, especially with large intraclass distances such as carrying smartphones at different locations and small interclass distances such as taking a train or subway. To address this problem, we propose a new framework of combining short-term spatial/frequency feature extraction and a long-term independently recurrent neural network (IndRNN) for activity recognition. Considering the periodic characteristics of the sensor data, short-term temporal features are first extracted in the spatial and frequency domains. Then, the IndRNN, which can capture long-term patterns, is used to further obtain the long-term features for classification. Given the large differences when the smartphone is carried at different locations, a group-based location recognition is first developed to pinpoint the location of the smartphone. The Sussex-Huawei Locomotion (SHL) dataset from the SHL Challenge is used for evaluation. An earlier version of the proposed method won the second place award in the SHL Challenge 2020 (first place if not considering the multiple models fusion approach). The proposed method is further improved in this paper and achieves 80.72% accuracy, better than the existing methods using a single model.

Contrast Sensitivity Function for Stereopsis

Perception ◽  
1978 ◽  
Vol 7 (4) ◽  
pp. 423-429 ◽  
Author(s):  
John P Frisby ◽  
John E W Mayhew
Keyword(s):  
Spatial Frequency ◽  
Contrast Sensitivity ◽  
Narrow Band ◽  
Sensitivity Function ◽  
Contrast Sensitivity Function ◽  
Band Noise ◽  
Random Dot Stereograms ◽  
Simple Detection ◽  
Global Stereopsis ◽  
Contrast Thresholds

Contrast thresholds for stereopsis from narrow-band-filtered random-dot stereograms were compared with contrast thresholds for simple detection of similar narrow-band noise. Centre frequencies of filters were in the range 2·5–15 cycles deg−1. It was found that the contrast sensitivity function for stereopsis is similar in shape to that for detection, suggesting that as far as contrast requirements are concerned the mechanisms of global stereopsis do not show a bias in sensitivity to any particular spatial frequency but instead require a constant level of suprathreshold contrast regardless of spatial frequency.

Organisation and Interrelationships of Functional Maps in Cat and Monkey Striate Cortex

Perception ◽  
1997 ◽  
Vol 26 (1_suppl) ◽  
pp. 356-356
Author(s):  
D Shoham ◽  
M Hübener ◽  
T Bonhoeffer ◽  
A Grinvald
Keyword(s):  
Spatial Frequency ◽  
Cytochrome Oxidase ◽  
Striate Cortex ◽  
Temporal Frequency ◽  
Activity Patterns ◽  
Ocular Dominance ◽  
High Spatial Frequency ◽  
Spatial Frequencies ◽  
Frequency Domains

Optical imaging of intrinsic signals allows mapping of the cortical functional architecture in vivo at high spatial resolution. The ability to image activity patterns evoked by many different stimuli in the same piece of cortex can provide information on the spatial relationships between different functional maps. Our findings on the organisation of multiple functional maps in cat and monkey striate cortex are reviewed. The main focus is on the recent finding in cat of two subsystems differing in their response to spatiotemporal aspects of the stimulus. We used grating stimuli of different spatial frequencies in an attempt to verify the existence of spatial frequency columns in cat area 17. Rather than observing a map of continuously changing spatial frequency across the cortical surface we found two distinct sets of domains, one preferring low and one preferring high spatial frequencies. By using different drift velocities we also found that the low-spatial-frequency domains preferred higher speeds than the high-spatial-frequency domains. Comparison of these spatiotemporal frequency domains with the cytochrome oxidase staining pattern revealed that the cytochrome oxidase blobs in cat striate cortex coincide with domains devoted to the processing of the low-spatial-frequency and high-temporal-frequency contents of the visual scene. Together with recent anatomical results these data suggest that spatiotemporal frequency domains are the manifestation of parallel streams in cat visual cortex with distinct patterns of thalamic inputs and extrastriate projections. In the same experiments we also imaged the orientation preference and ocular dominance maps. We investigated the relationships between these three columnar systems, and compared them to an earlier study of orientation, ocular dominance, and blobs in macaque striate cortex. We found systematic relationships between the three systems. While some of these relationships were much weaker than those found in monkey, the organisational principles are similar.

scholarly journals The Representation of Complex Images in Spatial Frequency Domains of Primary Visual Cortex

2007 ◽  
Vol 27 (35) ◽  
pp. 9310-9318 ◽  
Author(s):  
J. X. Zhang ◽  
A. Rosenberg ◽  
A. K. Mallik ◽  
T. R. Husson ◽  
N. P. Issa
Keyword(s):  
Visual Cortex ◽  
Spatial Frequency ◽  
Primary Visual Cortex ◽  
Frequency Domains ◽  
Complex Images
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